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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Generic ring buffer
4 *
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 */
7#include <linux/trace_recursion.h>
8#include <linux/trace_events.h>
9#include <linux/ring_buffer.h>
10#include <linux/trace_clock.h>
11#include <linux/sched/clock.h>
12#include <linux/cacheflush.h>
13#include <linux/trace_seq.h>
14#include <linux/spinlock.h>
15#include <linux/irq_work.h>
16#include <linux/security.h>
17#include <linux/uaccess.h>
18#include <linux/hardirq.h>
19#include <linux/kthread.h> /* for self test */
20#include <linux/module.h>
21#include <linux/percpu.h>
22#include <linux/mutex.h>
23#include <linux/delay.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/hash.h>
27#include <linux/list.h>
28#include <linux/cpu.h>
29#include <linux/oom.h>
30#include <linux/mm.h>
31
32#include <asm/local64.h>
33#include <asm/local.h>
34
35#include "trace.h"
36
37/*
38 * The "absolute" timestamp in the buffer is only 59 bits.
39 * If a clock has the 5 MSBs set, it needs to be saved and
40 * reinserted.
41 */
42#define TS_MSB (0xf8ULL << 56)
43#define ABS_TS_MASK (~TS_MSB)
44
45static void update_pages_handler(struct work_struct *work);
46
47#define RING_BUFFER_META_MAGIC 0xBADFEED
48
49struct ring_buffer_meta {
50 int magic;
51 int struct_size;
52 unsigned long text_addr;
53 unsigned long data_addr;
54 unsigned long first_buffer;
55 unsigned long head_buffer;
56 unsigned long commit_buffer;
57 __u32 subbuf_size;
58 __u32 nr_subbufs;
59 int buffers[];
60};
61
62/*
63 * The ring buffer header is special. We must manually up keep it.
64 */
65int ring_buffer_print_entry_header(struct trace_seq *s)
66{
67 trace_seq_puts(s, "# compressed entry header\n");
68 trace_seq_puts(s, "\ttype_len : 5 bits\n");
69 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
70 trace_seq_puts(s, "\tarray : 32 bits\n");
71 trace_seq_putc(s, '\n');
72 trace_seq_printf(s, "\tpadding : type == %d\n",
73 RINGBUF_TYPE_PADDING);
74 trace_seq_printf(s, "\ttime_extend : type == %d\n",
75 RINGBUF_TYPE_TIME_EXTEND);
76 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
77 RINGBUF_TYPE_TIME_STAMP);
78 trace_seq_printf(s, "\tdata max type_len == %d\n",
79 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
80
81 return !trace_seq_has_overflowed(s);
82}
83
84/*
85 * The ring buffer is made up of a list of pages. A separate list of pages is
86 * allocated for each CPU. A writer may only write to a buffer that is
87 * associated with the CPU it is currently executing on. A reader may read
88 * from any per cpu buffer.
89 *
90 * The reader is special. For each per cpu buffer, the reader has its own
91 * reader page. When a reader has read the entire reader page, this reader
92 * page is swapped with another page in the ring buffer.
93 *
94 * Now, as long as the writer is off the reader page, the reader can do what
95 * ever it wants with that page. The writer will never write to that page
96 * again (as long as it is out of the ring buffer).
97 *
98 * Here's some silly ASCII art.
99 *
100 * +------+
101 * |reader| RING BUFFER
102 * |page |
103 * +------+ +---+ +---+ +---+
104 * | |-->| |-->| |
105 * +---+ +---+ +---+
106 * ^ |
107 * | |
108 * +---------------+
109 *
110 *
111 * +------+
112 * |reader| RING BUFFER
113 * |page |------------------v
114 * +------+ +---+ +---+ +---+
115 * | |-->| |-->| |
116 * +---+ +---+ +---+
117 * ^ |
118 * | |
119 * +---------------+
120 *
121 *
122 * +------+
123 * |reader| RING BUFFER
124 * |page |------------------v
125 * +------+ +---+ +---+ +---+
126 * ^ | |-->| |-->| |
127 * | +---+ +---+ +---+
128 * | |
129 * | |
130 * +------------------------------+
131 *
132 *
133 * +------+
134 * |buffer| RING BUFFER
135 * |page |------------------v
136 * +------+ +---+ +---+ +---+
137 * ^ | | | |-->| |
138 * | New +---+ +---+ +---+
139 * | Reader------^ |
140 * | page |
141 * +------------------------------+
142 *
143 *
144 * After we make this swap, the reader can hand this page off to the splice
145 * code and be done with it. It can even allocate a new page if it needs to
146 * and swap that into the ring buffer.
147 *
148 * We will be using cmpxchg soon to make all this lockless.
149 *
150 */
151
152/* Used for individual buffers (after the counter) */
153#define RB_BUFFER_OFF (1 << 20)
154
155#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
156
157#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
158#define RB_ALIGNMENT 4U
159#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
160#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
161
162#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
163# define RB_FORCE_8BYTE_ALIGNMENT 0
164# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
165#else
166# define RB_FORCE_8BYTE_ALIGNMENT 1
167# define RB_ARCH_ALIGNMENT 8U
168#endif
169
170#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
171
172/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
173#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
174
175enum {
176 RB_LEN_TIME_EXTEND = 8,
177 RB_LEN_TIME_STAMP = 8,
178};
179
180#define skip_time_extend(event) \
181 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
182
183#define extended_time(event) \
184 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
185
186static inline bool rb_null_event(struct ring_buffer_event *event)
187{
188 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
189}
190
191static void rb_event_set_padding(struct ring_buffer_event *event)
192{
193 /* padding has a NULL time_delta */
194 event->type_len = RINGBUF_TYPE_PADDING;
195 event->time_delta = 0;
196}
197
198static unsigned
199rb_event_data_length(struct ring_buffer_event *event)
200{
201 unsigned length;
202
203 if (event->type_len)
204 length = event->type_len * RB_ALIGNMENT;
205 else
206 length = event->array[0];
207 return length + RB_EVNT_HDR_SIZE;
208}
209
210/*
211 * Return the length of the given event. Will return
212 * the length of the time extend if the event is a
213 * time extend.
214 */
215static inline unsigned
216rb_event_length(struct ring_buffer_event *event)
217{
218 switch (event->type_len) {
219 case RINGBUF_TYPE_PADDING:
220 if (rb_null_event(event))
221 /* undefined */
222 return -1;
223 return event->array[0] + RB_EVNT_HDR_SIZE;
224
225 case RINGBUF_TYPE_TIME_EXTEND:
226 return RB_LEN_TIME_EXTEND;
227
228 case RINGBUF_TYPE_TIME_STAMP:
229 return RB_LEN_TIME_STAMP;
230
231 case RINGBUF_TYPE_DATA:
232 return rb_event_data_length(event);
233 default:
234 WARN_ON_ONCE(1);
235 }
236 /* not hit */
237 return 0;
238}
239
240/*
241 * Return total length of time extend and data,
242 * or just the event length for all other events.
243 */
244static inline unsigned
245rb_event_ts_length(struct ring_buffer_event *event)
246{
247 unsigned len = 0;
248
249 if (extended_time(event)) {
250 /* time extends include the data event after it */
251 len = RB_LEN_TIME_EXTEND;
252 event = skip_time_extend(event);
253 }
254 return len + rb_event_length(event);
255}
256
257/**
258 * ring_buffer_event_length - return the length of the event
259 * @event: the event to get the length of
260 *
261 * Returns the size of the data load of a data event.
262 * If the event is something other than a data event, it
263 * returns the size of the event itself. With the exception
264 * of a TIME EXTEND, where it still returns the size of the
265 * data load of the data event after it.
266 */
267unsigned ring_buffer_event_length(struct ring_buffer_event *event)
268{
269 unsigned length;
270
271 if (extended_time(event))
272 event = skip_time_extend(event);
273
274 length = rb_event_length(event);
275 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
276 return length;
277 length -= RB_EVNT_HDR_SIZE;
278 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
279 length -= sizeof(event->array[0]);
280 return length;
281}
282EXPORT_SYMBOL_GPL(ring_buffer_event_length);
283
284/* inline for ring buffer fast paths */
285static __always_inline void *
286rb_event_data(struct ring_buffer_event *event)
287{
288 if (extended_time(event))
289 event = skip_time_extend(event);
290 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
291 /* If length is in len field, then array[0] has the data */
292 if (event->type_len)
293 return (void *)&event->array[0];
294 /* Otherwise length is in array[0] and array[1] has the data */
295 return (void *)&event->array[1];
296}
297
298/**
299 * ring_buffer_event_data - return the data of the event
300 * @event: the event to get the data from
301 */
302void *ring_buffer_event_data(struct ring_buffer_event *event)
303{
304 return rb_event_data(event);
305}
306EXPORT_SYMBOL_GPL(ring_buffer_event_data);
307
308#define for_each_buffer_cpu(buffer, cpu) \
309 for_each_cpu(cpu, buffer->cpumask)
310
311#define for_each_online_buffer_cpu(buffer, cpu) \
312 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
313
314#define TS_SHIFT 27
315#define TS_MASK ((1ULL << TS_SHIFT) - 1)
316#define TS_DELTA_TEST (~TS_MASK)
317
318static u64 rb_event_time_stamp(struct ring_buffer_event *event)
319{
320 u64 ts;
321
322 ts = event->array[0];
323 ts <<= TS_SHIFT;
324 ts += event->time_delta;
325
326 return ts;
327}
328
329/* Flag when events were overwritten */
330#define RB_MISSED_EVENTS (1 << 31)
331/* Missed count stored at end */
332#define RB_MISSED_STORED (1 << 30)
333
334#define RB_MISSED_MASK (3 << 30)
335
336struct buffer_data_page {
337 u64 time_stamp; /* page time stamp */
338 local_t commit; /* write committed index */
339 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
340};
341
342struct buffer_data_read_page {
343 unsigned order; /* order of the page */
344 struct buffer_data_page *data; /* actual data, stored in this page */
345};
346
347/*
348 * Note, the buffer_page list must be first. The buffer pages
349 * are allocated in cache lines, which means that each buffer
350 * page will be at the beginning of a cache line, and thus
351 * the least significant bits will be zero. We use this to
352 * add flags in the list struct pointers, to make the ring buffer
353 * lockless.
354 */
355struct buffer_page {
356 struct list_head list; /* list of buffer pages */
357 local_t write; /* index for next write */
358 unsigned read; /* index for next read */
359 local_t entries; /* entries on this page */
360 unsigned long real_end; /* real end of data */
361 unsigned order; /* order of the page */
362 u32 id:30; /* ID for external mapping */
363 u32 range:1; /* Mapped via a range */
364 struct buffer_data_page *page; /* Actual data page */
365};
366
367/*
368 * The buffer page counters, write and entries, must be reset
369 * atomically when crossing page boundaries. To synchronize this
370 * update, two counters are inserted into the number. One is
371 * the actual counter for the write position or count on the page.
372 *
373 * The other is a counter of updaters. Before an update happens
374 * the update partition of the counter is incremented. This will
375 * allow the updater to update the counter atomically.
376 *
377 * The counter is 20 bits, and the state data is 12.
378 */
379#define RB_WRITE_MASK 0xfffff
380#define RB_WRITE_INTCNT (1 << 20)
381
382static void rb_init_page(struct buffer_data_page *bpage)
383{
384 local_set(&bpage->commit, 0);
385}
386
387static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
388{
389 return local_read(&bpage->page->commit);
390}
391
392static void free_buffer_page(struct buffer_page *bpage)
393{
394 /* Range pages are not to be freed */
395 if (!bpage->range)
396 free_pages((unsigned long)bpage->page, bpage->order);
397 kfree(bpage);
398}
399
400/*
401 * We need to fit the time_stamp delta into 27 bits.
402 */
403static inline bool test_time_stamp(u64 delta)
404{
405 return !!(delta & TS_DELTA_TEST);
406}
407
408struct rb_irq_work {
409 struct irq_work work;
410 wait_queue_head_t waiters;
411 wait_queue_head_t full_waiters;
412 atomic_t seq;
413 bool waiters_pending;
414 bool full_waiters_pending;
415 bool wakeup_full;
416};
417
418/*
419 * Structure to hold event state and handle nested events.
420 */
421struct rb_event_info {
422 u64 ts;
423 u64 delta;
424 u64 before;
425 u64 after;
426 unsigned long length;
427 struct buffer_page *tail_page;
428 int add_timestamp;
429};
430
431/*
432 * Used for the add_timestamp
433 * NONE
434 * EXTEND - wants a time extend
435 * ABSOLUTE - the buffer requests all events to have absolute time stamps
436 * FORCE - force a full time stamp.
437 */
438enum {
439 RB_ADD_STAMP_NONE = 0,
440 RB_ADD_STAMP_EXTEND = BIT(1),
441 RB_ADD_STAMP_ABSOLUTE = BIT(2),
442 RB_ADD_STAMP_FORCE = BIT(3)
443};
444/*
445 * Used for which event context the event is in.
446 * TRANSITION = 0
447 * NMI = 1
448 * IRQ = 2
449 * SOFTIRQ = 3
450 * NORMAL = 4
451 *
452 * See trace_recursive_lock() comment below for more details.
453 */
454enum {
455 RB_CTX_TRANSITION,
456 RB_CTX_NMI,
457 RB_CTX_IRQ,
458 RB_CTX_SOFTIRQ,
459 RB_CTX_NORMAL,
460 RB_CTX_MAX
461};
462
463struct rb_time_struct {
464 local64_t time;
465};
466typedef struct rb_time_struct rb_time_t;
467
468#define MAX_NEST 5
469
470/*
471 * head_page == tail_page && head == tail then buffer is empty.
472 */
473struct ring_buffer_per_cpu {
474 int cpu;
475 atomic_t record_disabled;
476 atomic_t resize_disabled;
477 struct trace_buffer *buffer;
478 raw_spinlock_t reader_lock; /* serialize readers */
479 arch_spinlock_t lock;
480 struct lock_class_key lock_key;
481 struct buffer_data_page *free_page;
482 unsigned long nr_pages;
483 unsigned int current_context;
484 struct list_head *pages;
485 /* pages generation counter, incremented when the list changes */
486 unsigned long cnt;
487 struct buffer_page *head_page; /* read from head */
488 struct buffer_page *tail_page; /* write to tail */
489 struct buffer_page *commit_page; /* committed pages */
490 struct buffer_page *reader_page;
491 unsigned long lost_events;
492 unsigned long last_overrun;
493 unsigned long nest;
494 local_t entries_bytes;
495 local_t entries;
496 local_t overrun;
497 local_t commit_overrun;
498 local_t dropped_events;
499 local_t committing;
500 local_t commits;
501 local_t pages_touched;
502 local_t pages_lost;
503 local_t pages_read;
504 long last_pages_touch;
505 size_t shortest_full;
506 unsigned long read;
507 unsigned long read_bytes;
508 rb_time_t write_stamp;
509 rb_time_t before_stamp;
510 u64 event_stamp[MAX_NEST];
511 u64 read_stamp;
512 /* pages removed since last reset */
513 unsigned long pages_removed;
514
515 unsigned int mapped;
516 unsigned int user_mapped; /* user space mapping */
517 struct mutex mapping_lock;
518 unsigned long *subbuf_ids; /* ID to subbuf VA */
519 struct trace_buffer_meta *meta_page;
520 struct ring_buffer_meta *ring_meta;
521
522 /* ring buffer pages to update, > 0 to add, < 0 to remove */
523 long nr_pages_to_update;
524 struct list_head new_pages; /* new pages to add */
525 struct work_struct update_pages_work;
526 struct completion update_done;
527
528 struct rb_irq_work irq_work;
529};
530
531struct trace_buffer {
532 unsigned flags;
533 int cpus;
534 atomic_t record_disabled;
535 atomic_t resizing;
536 cpumask_var_t cpumask;
537
538 struct lock_class_key *reader_lock_key;
539
540 struct mutex mutex;
541
542 struct ring_buffer_per_cpu **buffers;
543
544 struct hlist_node node;
545 u64 (*clock)(void);
546
547 struct rb_irq_work irq_work;
548 bool time_stamp_abs;
549
550 unsigned long range_addr_start;
551 unsigned long range_addr_end;
552
553 long last_text_delta;
554 long last_data_delta;
555
556 unsigned int subbuf_size;
557 unsigned int subbuf_order;
558 unsigned int max_data_size;
559};
560
561struct ring_buffer_iter {
562 struct ring_buffer_per_cpu *cpu_buffer;
563 unsigned long head;
564 unsigned long next_event;
565 struct buffer_page *head_page;
566 struct buffer_page *cache_reader_page;
567 unsigned long cache_read;
568 unsigned long cache_pages_removed;
569 u64 read_stamp;
570 u64 page_stamp;
571 struct ring_buffer_event *event;
572 size_t event_size;
573 int missed_events;
574};
575
576int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
577{
578 struct buffer_data_page field;
579
580 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
581 "offset:0;\tsize:%u;\tsigned:%u;\n",
582 (unsigned int)sizeof(field.time_stamp),
583 (unsigned int)is_signed_type(u64));
584
585 trace_seq_printf(s, "\tfield: local_t commit;\t"
586 "offset:%u;\tsize:%u;\tsigned:%u;\n",
587 (unsigned int)offsetof(typeof(field), commit),
588 (unsigned int)sizeof(field.commit),
589 (unsigned int)is_signed_type(long));
590
591 trace_seq_printf(s, "\tfield: int overwrite;\t"
592 "offset:%u;\tsize:%u;\tsigned:%u;\n",
593 (unsigned int)offsetof(typeof(field), commit),
594 1,
595 (unsigned int)is_signed_type(long));
596
597 trace_seq_printf(s, "\tfield: char data;\t"
598 "offset:%u;\tsize:%u;\tsigned:%u;\n",
599 (unsigned int)offsetof(typeof(field), data),
600 (unsigned int)buffer->subbuf_size,
601 (unsigned int)is_signed_type(char));
602
603 return !trace_seq_has_overflowed(s);
604}
605
606static inline void rb_time_read(rb_time_t *t, u64 *ret)
607{
608 *ret = local64_read(&t->time);
609}
610static void rb_time_set(rb_time_t *t, u64 val)
611{
612 local64_set(&t->time, val);
613}
614
615/*
616 * Enable this to make sure that the event passed to
617 * ring_buffer_event_time_stamp() is not committed and also
618 * is on the buffer that it passed in.
619 */
620//#define RB_VERIFY_EVENT
621#ifdef RB_VERIFY_EVENT
622static struct list_head *rb_list_head(struct list_head *list);
623static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
624 void *event)
625{
626 struct buffer_page *page = cpu_buffer->commit_page;
627 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
628 struct list_head *next;
629 long commit, write;
630 unsigned long addr = (unsigned long)event;
631 bool done = false;
632 int stop = 0;
633
634 /* Make sure the event exists and is not committed yet */
635 do {
636 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
637 done = true;
638 commit = local_read(&page->page->commit);
639 write = local_read(&page->write);
640 if (addr >= (unsigned long)&page->page->data[commit] &&
641 addr < (unsigned long)&page->page->data[write])
642 return;
643
644 next = rb_list_head(page->list.next);
645 page = list_entry(next, struct buffer_page, list);
646 } while (!done);
647 WARN_ON_ONCE(1);
648}
649#else
650static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
651 void *event)
652{
653}
654#endif
655
656/*
657 * The absolute time stamp drops the 5 MSBs and some clocks may
658 * require them. The rb_fix_abs_ts() will take a previous full
659 * time stamp, and add the 5 MSB of that time stamp on to the
660 * saved absolute time stamp. Then they are compared in case of
661 * the unlikely event that the latest time stamp incremented
662 * the 5 MSB.
663 */
664static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
665{
666 if (save_ts & TS_MSB) {
667 abs |= save_ts & TS_MSB;
668 /* Check for overflow */
669 if (unlikely(abs < save_ts))
670 abs += 1ULL << 59;
671 }
672 return abs;
673}
674
675static inline u64 rb_time_stamp(struct trace_buffer *buffer);
676
677/**
678 * ring_buffer_event_time_stamp - return the event's current time stamp
679 * @buffer: The buffer that the event is on
680 * @event: the event to get the time stamp of
681 *
682 * Note, this must be called after @event is reserved, and before it is
683 * committed to the ring buffer. And must be called from the same
684 * context where the event was reserved (normal, softirq, irq, etc).
685 *
686 * Returns the time stamp associated with the current event.
687 * If the event has an extended time stamp, then that is used as
688 * the time stamp to return.
689 * In the highly unlikely case that the event was nested more than
690 * the max nesting, then the write_stamp of the buffer is returned,
691 * otherwise current time is returned, but that really neither of
692 * the last two cases should ever happen.
693 */
694u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
695 struct ring_buffer_event *event)
696{
697 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
698 unsigned int nest;
699 u64 ts;
700
701 /* If the event includes an absolute time, then just use that */
702 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
703 ts = rb_event_time_stamp(event);
704 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
705 }
706
707 nest = local_read(&cpu_buffer->committing);
708 verify_event(cpu_buffer, event);
709 if (WARN_ON_ONCE(!nest))
710 goto fail;
711
712 /* Read the current saved nesting level time stamp */
713 if (likely(--nest < MAX_NEST))
714 return cpu_buffer->event_stamp[nest];
715
716 /* Shouldn't happen, warn if it does */
717 WARN_ONCE(1, "nest (%d) greater than max", nest);
718
719 fail:
720 rb_time_read(&cpu_buffer->write_stamp, &ts);
721
722 return ts;
723}
724
725/**
726 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
727 * @buffer: The ring_buffer to get the number of pages from
728 * @cpu: The cpu of the ring_buffer to get the number of pages from
729 *
730 * Returns the number of pages that have content in the ring buffer.
731 */
732size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
733{
734 size_t read;
735 size_t lost;
736 size_t cnt;
737
738 read = local_read(&buffer->buffers[cpu]->pages_read);
739 lost = local_read(&buffer->buffers[cpu]->pages_lost);
740 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
741
742 if (WARN_ON_ONCE(cnt < lost))
743 return 0;
744
745 cnt -= lost;
746
747 /* The reader can read an empty page, but not more than that */
748 if (cnt < read) {
749 WARN_ON_ONCE(read > cnt + 1);
750 return 0;
751 }
752
753 return cnt - read;
754}
755
756static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
757{
758 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
759 size_t nr_pages;
760 size_t dirty;
761
762 nr_pages = cpu_buffer->nr_pages;
763 if (!nr_pages || !full)
764 return true;
765
766 /*
767 * Add one as dirty will never equal nr_pages, as the sub-buffer
768 * that the writer is on is not counted as dirty.
769 * This is needed if "buffer_percent" is set to 100.
770 */
771 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
772
773 return (dirty * 100) >= (full * nr_pages);
774}
775
776/*
777 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
778 *
779 * Schedules a delayed work to wake up any task that is blocked on the
780 * ring buffer waiters queue.
781 */
782static void rb_wake_up_waiters(struct irq_work *work)
783{
784 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
785
786 /* For waiters waiting for the first wake up */
787 (void)atomic_fetch_inc_release(&rbwork->seq);
788
789 wake_up_all(&rbwork->waiters);
790 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
791 /* Only cpu_buffer sets the above flags */
792 struct ring_buffer_per_cpu *cpu_buffer =
793 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
794
795 /* Called from interrupt context */
796 raw_spin_lock(&cpu_buffer->reader_lock);
797 rbwork->wakeup_full = false;
798 rbwork->full_waiters_pending = false;
799
800 /* Waking up all waiters, they will reset the shortest full */
801 cpu_buffer->shortest_full = 0;
802 raw_spin_unlock(&cpu_buffer->reader_lock);
803
804 wake_up_all(&rbwork->full_waiters);
805 }
806}
807
808/**
809 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
810 * @buffer: The ring buffer to wake waiters on
811 * @cpu: The CPU buffer to wake waiters on
812 *
813 * In the case of a file that represents a ring buffer is closing,
814 * it is prudent to wake up any waiters that are on this.
815 */
816void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
817{
818 struct ring_buffer_per_cpu *cpu_buffer;
819 struct rb_irq_work *rbwork;
820
821 if (!buffer)
822 return;
823
824 if (cpu == RING_BUFFER_ALL_CPUS) {
825
826 /* Wake up individual ones too. One level recursion */
827 for_each_buffer_cpu(buffer, cpu)
828 ring_buffer_wake_waiters(buffer, cpu);
829
830 rbwork = &buffer->irq_work;
831 } else {
832 if (WARN_ON_ONCE(!buffer->buffers))
833 return;
834 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
835 return;
836
837 cpu_buffer = buffer->buffers[cpu];
838 /* The CPU buffer may not have been initialized yet */
839 if (!cpu_buffer)
840 return;
841 rbwork = &cpu_buffer->irq_work;
842 }
843
844 /* This can be called in any context */
845 irq_work_queue(&rbwork->work);
846}
847
848static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
849{
850 struct ring_buffer_per_cpu *cpu_buffer;
851 bool ret = false;
852
853 /* Reads of all CPUs always waits for any data */
854 if (cpu == RING_BUFFER_ALL_CPUS)
855 return !ring_buffer_empty(buffer);
856
857 cpu_buffer = buffer->buffers[cpu];
858
859 if (!ring_buffer_empty_cpu(buffer, cpu)) {
860 unsigned long flags;
861 bool pagebusy;
862
863 if (!full)
864 return true;
865
866 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
867 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
868 ret = !pagebusy && full_hit(buffer, cpu, full);
869
870 if (!ret && (!cpu_buffer->shortest_full ||
871 cpu_buffer->shortest_full > full)) {
872 cpu_buffer->shortest_full = full;
873 }
874 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
875 }
876 return ret;
877}
878
879static inline bool
880rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
881 int cpu, int full, ring_buffer_cond_fn cond, void *data)
882{
883 if (rb_watermark_hit(buffer, cpu, full))
884 return true;
885
886 if (cond(data))
887 return true;
888
889 /*
890 * The events can happen in critical sections where
891 * checking a work queue can cause deadlocks.
892 * After adding a task to the queue, this flag is set
893 * only to notify events to try to wake up the queue
894 * using irq_work.
895 *
896 * We don't clear it even if the buffer is no longer
897 * empty. The flag only causes the next event to run
898 * irq_work to do the work queue wake up. The worse
899 * that can happen if we race with !trace_empty() is that
900 * an event will cause an irq_work to try to wake up
901 * an empty queue.
902 *
903 * There's no reason to protect this flag either, as
904 * the work queue and irq_work logic will do the necessary
905 * synchronization for the wake ups. The only thing
906 * that is necessary is that the wake up happens after
907 * a task has been queued. It's OK for spurious wake ups.
908 */
909 if (full)
910 rbwork->full_waiters_pending = true;
911 else
912 rbwork->waiters_pending = true;
913
914 return false;
915}
916
917struct rb_wait_data {
918 struct rb_irq_work *irq_work;
919 int seq;
920};
921
922/*
923 * The default wait condition for ring_buffer_wait() is to just to exit the
924 * wait loop the first time it is woken up.
925 */
926static bool rb_wait_once(void *data)
927{
928 struct rb_wait_data *rdata = data;
929 struct rb_irq_work *rbwork = rdata->irq_work;
930
931 return atomic_read_acquire(&rbwork->seq) != rdata->seq;
932}
933
934/**
935 * ring_buffer_wait - wait for input to the ring buffer
936 * @buffer: buffer to wait on
937 * @cpu: the cpu buffer to wait on
938 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
939 * @cond: condition function to break out of wait (NULL to run once)
940 * @data: the data to pass to @cond.
941 *
942 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
943 * as data is added to any of the @buffer's cpu buffers. Otherwise
944 * it will wait for data to be added to a specific cpu buffer.
945 */
946int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
947 ring_buffer_cond_fn cond, void *data)
948{
949 struct ring_buffer_per_cpu *cpu_buffer;
950 struct wait_queue_head *waitq;
951 struct rb_irq_work *rbwork;
952 struct rb_wait_data rdata;
953 int ret = 0;
954
955 /*
956 * Depending on what the caller is waiting for, either any
957 * data in any cpu buffer, or a specific buffer, put the
958 * caller on the appropriate wait queue.
959 */
960 if (cpu == RING_BUFFER_ALL_CPUS) {
961 rbwork = &buffer->irq_work;
962 /* Full only makes sense on per cpu reads */
963 full = 0;
964 } else {
965 if (!cpumask_test_cpu(cpu, buffer->cpumask))
966 return -ENODEV;
967 cpu_buffer = buffer->buffers[cpu];
968 rbwork = &cpu_buffer->irq_work;
969 }
970
971 if (full)
972 waitq = &rbwork->full_waiters;
973 else
974 waitq = &rbwork->waiters;
975
976 /* Set up to exit loop as soon as it is woken */
977 if (!cond) {
978 cond = rb_wait_once;
979 rdata.irq_work = rbwork;
980 rdata.seq = atomic_read_acquire(&rbwork->seq);
981 data = &rdata;
982 }
983
984 ret = wait_event_interruptible((*waitq),
985 rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
986
987 return ret;
988}
989
990/**
991 * ring_buffer_poll_wait - poll on buffer input
992 * @buffer: buffer to wait on
993 * @cpu: the cpu buffer to wait on
994 * @filp: the file descriptor
995 * @poll_table: The poll descriptor
996 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
997 *
998 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
999 * as data is added to any of the @buffer's cpu buffers. Otherwise
1000 * it will wait for data to be added to a specific cpu buffer.
1001 *
1002 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1003 * zero otherwise.
1004 */
1005__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1006 struct file *filp, poll_table *poll_table, int full)
1007{
1008 struct ring_buffer_per_cpu *cpu_buffer;
1009 struct rb_irq_work *rbwork;
1010
1011 if (cpu == RING_BUFFER_ALL_CPUS) {
1012 rbwork = &buffer->irq_work;
1013 full = 0;
1014 } else {
1015 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1016 return EPOLLERR;
1017
1018 cpu_buffer = buffer->buffers[cpu];
1019 rbwork = &cpu_buffer->irq_work;
1020 }
1021
1022 if (full) {
1023 poll_wait(filp, &rbwork->full_waiters, poll_table);
1024
1025 if (rb_watermark_hit(buffer, cpu, full))
1026 return EPOLLIN | EPOLLRDNORM;
1027 /*
1028 * Only allow full_waiters_pending update to be seen after
1029 * the shortest_full is set (in rb_watermark_hit). If the
1030 * writer sees the full_waiters_pending flag set, it will
1031 * compare the amount in the ring buffer to shortest_full.
1032 * If the amount in the ring buffer is greater than the
1033 * shortest_full percent, it will call the irq_work handler
1034 * to wake up this list. The irq_handler will reset shortest_full
1035 * back to zero. That's done under the reader_lock, but
1036 * the below smp_mb() makes sure that the update to
1037 * full_waiters_pending doesn't leak up into the above.
1038 */
1039 smp_mb();
1040 rbwork->full_waiters_pending = true;
1041 return 0;
1042 }
1043
1044 poll_wait(filp, &rbwork->waiters, poll_table);
1045 rbwork->waiters_pending = true;
1046
1047 /*
1048 * There's a tight race between setting the waiters_pending and
1049 * checking if the ring buffer is empty. Once the waiters_pending bit
1050 * is set, the next event will wake the task up, but we can get stuck
1051 * if there's only a single event in.
1052 *
1053 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1054 * but adding a memory barrier to all events will cause too much of a
1055 * performance hit in the fast path. We only need a memory barrier when
1056 * the buffer goes from empty to having content. But as this race is
1057 * extremely small, and it's not a problem if another event comes in, we
1058 * will fix it later.
1059 */
1060 smp_mb();
1061
1062 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1063 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1064 return EPOLLIN | EPOLLRDNORM;
1065 return 0;
1066}
1067
1068/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1069#define RB_WARN_ON(b, cond) \
1070 ({ \
1071 int _____ret = unlikely(cond); \
1072 if (_____ret) { \
1073 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1074 struct ring_buffer_per_cpu *__b = \
1075 (void *)b; \
1076 atomic_inc(&__b->buffer->record_disabled); \
1077 } else \
1078 atomic_inc(&b->record_disabled); \
1079 WARN_ON(1); \
1080 } \
1081 _____ret; \
1082 })
1083
1084/* Up this if you want to test the TIME_EXTENTS and normalization */
1085#define DEBUG_SHIFT 0
1086
1087static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1088{
1089 u64 ts;
1090
1091 /* Skip retpolines :-( */
1092 if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1093 ts = trace_clock_local();
1094 else
1095 ts = buffer->clock();
1096
1097 /* shift to debug/test normalization and TIME_EXTENTS */
1098 return ts << DEBUG_SHIFT;
1099}
1100
1101u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1102{
1103 u64 time;
1104
1105 preempt_disable_notrace();
1106 time = rb_time_stamp(buffer);
1107 preempt_enable_notrace();
1108
1109 return time;
1110}
1111EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1112
1113void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1114 int cpu, u64 *ts)
1115{
1116 /* Just stupid testing the normalize function and deltas */
1117 *ts >>= DEBUG_SHIFT;
1118}
1119EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1120
1121/*
1122 * Making the ring buffer lockless makes things tricky.
1123 * Although writes only happen on the CPU that they are on,
1124 * and they only need to worry about interrupts. Reads can
1125 * happen on any CPU.
1126 *
1127 * The reader page is always off the ring buffer, but when the
1128 * reader finishes with a page, it needs to swap its page with
1129 * a new one from the buffer. The reader needs to take from
1130 * the head (writes go to the tail). But if a writer is in overwrite
1131 * mode and wraps, it must push the head page forward.
1132 *
1133 * Here lies the problem.
1134 *
1135 * The reader must be careful to replace only the head page, and
1136 * not another one. As described at the top of the file in the
1137 * ASCII art, the reader sets its old page to point to the next
1138 * page after head. It then sets the page after head to point to
1139 * the old reader page. But if the writer moves the head page
1140 * during this operation, the reader could end up with the tail.
1141 *
1142 * We use cmpxchg to help prevent this race. We also do something
1143 * special with the page before head. We set the LSB to 1.
1144 *
1145 * When the writer must push the page forward, it will clear the
1146 * bit that points to the head page, move the head, and then set
1147 * the bit that points to the new head page.
1148 *
1149 * We also don't want an interrupt coming in and moving the head
1150 * page on another writer. Thus we use the second LSB to catch
1151 * that too. Thus:
1152 *
1153 * head->list->prev->next bit 1 bit 0
1154 * ------- -------
1155 * Normal page 0 0
1156 * Points to head page 0 1
1157 * New head page 1 0
1158 *
1159 * Note we can not trust the prev pointer of the head page, because:
1160 *
1161 * +----+ +-----+ +-----+
1162 * | |------>| T |---X--->| N |
1163 * | |<------| | | |
1164 * +----+ +-----+ +-----+
1165 * ^ ^ |
1166 * | +-----+ | |
1167 * +----------| R |----------+ |
1168 * | |<-----------+
1169 * +-----+
1170 *
1171 * Key: ---X--> HEAD flag set in pointer
1172 * T Tail page
1173 * R Reader page
1174 * N Next page
1175 *
1176 * (see __rb_reserve_next() to see where this happens)
1177 *
1178 * What the above shows is that the reader just swapped out
1179 * the reader page with a page in the buffer, but before it
1180 * could make the new header point back to the new page added
1181 * it was preempted by a writer. The writer moved forward onto
1182 * the new page added by the reader and is about to move forward
1183 * again.
1184 *
1185 * You can see, it is legitimate for the previous pointer of
1186 * the head (or any page) not to point back to itself. But only
1187 * temporarily.
1188 */
1189
1190#define RB_PAGE_NORMAL 0UL
1191#define RB_PAGE_HEAD 1UL
1192#define RB_PAGE_UPDATE 2UL
1193
1194
1195#define RB_FLAG_MASK 3UL
1196
1197/* PAGE_MOVED is not part of the mask */
1198#define RB_PAGE_MOVED 4UL
1199
1200/*
1201 * rb_list_head - remove any bit
1202 */
1203static struct list_head *rb_list_head(struct list_head *list)
1204{
1205 unsigned long val = (unsigned long)list;
1206
1207 return (struct list_head *)(val & ~RB_FLAG_MASK);
1208}
1209
1210/*
1211 * rb_is_head_page - test if the given page is the head page
1212 *
1213 * Because the reader may move the head_page pointer, we can
1214 * not trust what the head page is (it may be pointing to
1215 * the reader page). But if the next page is a header page,
1216 * its flags will be non zero.
1217 */
1218static inline int
1219rb_is_head_page(struct buffer_page *page, struct list_head *list)
1220{
1221 unsigned long val;
1222
1223 val = (unsigned long)list->next;
1224
1225 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1226 return RB_PAGE_MOVED;
1227
1228 return val & RB_FLAG_MASK;
1229}
1230
1231/*
1232 * rb_is_reader_page
1233 *
1234 * The unique thing about the reader page, is that, if the
1235 * writer is ever on it, the previous pointer never points
1236 * back to the reader page.
1237 */
1238static bool rb_is_reader_page(struct buffer_page *page)
1239{
1240 struct list_head *list = page->list.prev;
1241
1242 return rb_list_head(list->next) != &page->list;
1243}
1244
1245/*
1246 * rb_set_list_to_head - set a list_head to be pointing to head.
1247 */
1248static void rb_set_list_to_head(struct list_head *list)
1249{
1250 unsigned long *ptr;
1251
1252 ptr = (unsigned long *)&list->next;
1253 *ptr |= RB_PAGE_HEAD;
1254 *ptr &= ~RB_PAGE_UPDATE;
1255}
1256
1257/*
1258 * rb_head_page_activate - sets up head page
1259 */
1260static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1261{
1262 struct buffer_page *head;
1263
1264 head = cpu_buffer->head_page;
1265 if (!head)
1266 return;
1267
1268 /*
1269 * Set the previous list pointer to have the HEAD flag.
1270 */
1271 rb_set_list_to_head(head->list.prev);
1272
1273 if (cpu_buffer->ring_meta) {
1274 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1275 meta->head_buffer = (unsigned long)head->page;
1276 }
1277}
1278
1279static void rb_list_head_clear(struct list_head *list)
1280{
1281 unsigned long *ptr = (unsigned long *)&list->next;
1282
1283 *ptr &= ~RB_FLAG_MASK;
1284}
1285
1286/*
1287 * rb_head_page_deactivate - clears head page ptr (for free list)
1288 */
1289static void
1290rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1291{
1292 struct list_head *hd;
1293
1294 /* Go through the whole list and clear any pointers found. */
1295 rb_list_head_clear(cpu_buffer->pages);
1296
1297 list_for_each(hd, cpu_buffer->pages)
1298 rb_list_head_clear(hd);
1299}
1300
1301static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1302 struct buffer_page *head,
1303 struct buffer_page *prev,
1304 int old_flag, int new_flag)
1305{
1306 struct list_head *list;
1307 unsigned long val = (unsigned long)&head->list;
1308 unsigned long ret;
1309
1310 list = &prev->list;
1311
1312 val &= ~RB_FLAG_MASK;
1313
1314 ret = cmpxchg((unsigned long *)&list->next,
1315 val | old_flag, val | new_flag);
1316
1317 /* check if the reader took the page */
1318 if ((ret & ~RB_FLAG_MASK) != val)
1319 return RB_PAGE_MOVED;
1320
1321 return ret & RB_FLAG_MASK;
1322}
1323
1324static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1325 struct buffer_page *head,
1326 struct buffer_page *prev,
1327 int old_flag)
1328{
1329 return rb_head_page_set(cpu_buffer, head, prev,
1330 old_flag, RB_PAGE_UPDATE);
1331}
1332
1333static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1334 struct buffer_page *head,
1335 struct buffer_page *prev,
1336 int old_flag)
1337{
1338 return rb_head_page_set(cpu_buffer, head, prev,
1339 old_flag, RB_PAGE_HEAD);
1340}
1341
1342static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1343 struct buffer_page *head,
1344 struct buffer_page *prev,
1345 int old_flag)
1346{
1347 return rb_head_page_set(cpu_buffer, head, prev,
1348 old_flag, RB_PAGE_NORMAL);
1349}
1350
1351static inline void rb_inc_page(struct buffer_page **bpage)
1352{
1353 struct list_head *p = rb_list_head((*bpage)->list.next);
1354
1355 *bpage = list_entry(p, struct buffer_page, list);
1356}
1357
1358static struct buffer_page *
1359rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1360{
1361 struct buffer_page *head;
1362 struct buffer_page *page;
1363 struct list_head *list;
1364 int i;
1365
1366 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1367 return NULL;
1368
1369 /* sanity check */
1370 list = cpu_buffer->pages;
1371 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1372 return NULL;
1373
1374 page = head = cpu_buffer->head_page;
1375 /*
1376 * It is possible that the writer moves the header behind
1377 * where we started, and we miss in one loop.
1378 * A second loop should grab the header, but we'll do
1379 * three loops just because I'm paranoid.
1380 */
1381 for (i = 0; i < 3; i++) {
1382 do {
1383 if (rb_is_head_page(page, page->list.prev)) {
1384 cpu_buffer->head_page = page;
1385 return page;
1386 }
1387 rb_inc_page(&page);
1388 } while (page != head);
1389 }
1390
1391 RB_WARN_ON(cpu_buffer, 1);
1392
1393 return NULL;
1394}
1395
1396static bool rb_head_page_replace(struct buffer_page *old,
1397 struct buffer_page *new)
1398{
1399 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1400 unsigned long val;
1401
1402 val = *ptr & ~RB_FLAG_MASK;
1403 val |= RB_PAGE_HEAD;
1404
1405 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1406}
1407
1408/*
1409 * rb_tail_page_update - move the tail page forward
1410 */
1411static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1412 struct buffer_page *tail_page,
1413 struct buffer_page *next_page)
1414{
1415 unsigned long old_entries;
1416 unsigned long old_write;
1417
1418 /*
1419 * The tail page now needs to be moved forward.
1420 *
1421 * We need to reset the tail page, but without messing
1422 * with possible erasing of data brought in by interrupts
1423 * that have moved the tail page and are currently on it.
1424 *
1425 * We add a counter to the write field to denote this.
1426 */
1427 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1428 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1429
1430 /*
1431 * Just make sure we have seen our old_write and synchronize
1432 * with any interrupts that come in.
1433 */
1434 barrier();
1435
1436 /*
1437 * If the tail page is still the same as what we think
1438 * it is, then it is up to us to update the tail
1439 * pointer.
1440 */
1441 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1442 /* Zero the write counter */
1443 unsigned long val = old_write & ~RB_WRITE_MASK;
1444 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1445
1446 /*
1447 * This will only succeed if an interrupt did
1448 * not come in and change it. In which case, we
1449 * do not want to modify it.
1450 *
1451 * We add (void) to let the compiler know that we do not care
1452 * about the return value of these functions. We use the
1453 * cmpxchg to only update if an interrupt did not already
1454 * do it for us. If the cmpxchg fails, we don't care.
1455 */
1456 (void)local_cmpxchg(&next_page->write, old_write, val);
1457 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1458
1459 /*
1460 * No need to worry about races with clearing out the commit.
1461 * it only can increment when a commit takes place. But that
1462 * only happens in the outer most nested commit.
1463 */
1464 local_set(&next_page->page->commit, 0);
1465
1466 /* Either we update tail_page or an interrupt does */
1467 if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1468 local_inc(&cpu_buffer->pages_touched);
1469 }
1470}
1471
1472static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1473 struct buffer_page *bpage)
1474{
1475 unsigned long val = (unsigned long)bpage;
1476
1477 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1478}
1479
1480static bool rb_check_links(struct ring_buffer_per_cpu *cpu_buffer,
1481 struct list_head *list)
1482{
1483 if (RB_WARN_ON(cpu_buffer,
1484 rb_list_head(rb_list_head(list->next)->prev) != list))
1485 return false;
1486
1487 if (RB_WARN_ON(cpu_buffer,
1488 rb_list_head(rb_list_head(list->prev)->next) != list))
1489 return false;
1490
1491 return true;
1492}
1493
1494/**
1495 * rb_check_pages - integrity check of buffer pages
1496 * @cpu_buffer: CPU buffer with pages to test
1497 *
1498 * As a safety measure we check to make sure the data pages have not
1499 * been corrupted.
1500 */
1501static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1502{
1503 struct list_head *head, *tmp;
1504 unsigned long buffer_cnt;
1505 unsigned long flags;
1506 int nr_loops = 0;
1507
1508 /*
1509 * Walk the linked list underpinning the ring buffer and validate all
1510 * its next and prev links.
1511 *
1512 * The check acquires the reader_lock to avoid concurrent processing
1513 * with code that could be modifying the list. However, the lock cannot
1514 * be held for the entire duration of the walk, as this would make the
1515 * time when interrupts are disabled non-deterministic, dependent on the
1516 * ring buffer size. Therefore, the code releases and re-acquires the
1517 * lock after checking each page. The ring_buffer_per_cpu.cnt variable
1518 * is then used to detect if the list was modified while the lock was
1519 * not held, in which case the check needs to be restarted.
1520 *
1521 * The code attempts to perform the check at most three times before
1522 * giving up. This is acceptable because this is only a self-validation
1523 * to detect problems early on. In practice, the list modification
1524 * operations are fairly spaced, and so this check typically succeeds at
1525 * most on the second try.
1526 */
1527again:
1528 if (++nr_loops > 3)
1529 return;
1530
1531 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1532 head = rb_list_head(cpu_buffer->pages);
1533 if (!rb_check_links(cpu_buffer, head))
1534 goto out_locked;
1535 buffer_cnt = cpu_buffer->cnt;
1536 tmp = head;
1537 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1538
1539 while (true) {
1540 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1541
1542 if (buffer_cnt != cpu_buffer->cnt) {
1543 /* The list was updated, try again. */
1544 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1545 goto again;
1546 }
1547
1548 tmp = rb_list_head(tmp->next);
1549 if (tmp == head)
1550 /* The iteration circled back, all is done. */
1551 goto out_locked;
1552
1553 if (!rb_check_links(cpu_buffer, tmp))
1554 goto out_locked;
1555
1556 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1557 }
1558
1559out_locked:
1560 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1561}
1562
1563/*
1564 * Take an address, add the meta data size as well as the array of
1565 * array subbuffer indexes, then align it to a subbuffer size.
1566 *
1567 * This is used to help find the next per cpu subbuffer within a mapped range.
1568 */
1569static unsigned long
1570rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
1571{
1572 addr += sizeof(struct ring_buffer_meta) +
1573 sizeof(int) * nr_subbufs;
1574 return ALIGN(addr, subbuf_size);
1575}
1576
1577/*
1578 * Return the ring_buffer_meta for a given @cpu.
1579 */
1580static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
1581{
1582 int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
1583 unsigned long ptr = buffer->range_addr_start;
1584 struct ring_buffer_meta *meta;
1585 int nr_subbufs;
1586
1587 if (!ptr)
1588 return NULL;
1589
1590 /* When nr_pages passed in is zero, the first meta has already been initialized */
1591 if (!nr_pages) {
1592 meta = (struct ring_buffer_meta *)ptr;
1593 nr_subbufs = meta->nr_subbufs;
1594 } else {
1595 meta = NULL;
1596 /* Include the reader page */
1597 nr_subbufs = nr_pages + 1;
1598 }
1599
1600 /*
1601 * The first chunk may not be subbuffer aligned, where as
1602 * the rest of the chunks are.
1603 */
1604 if (cpu) {
1605 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1606 ptr += subbuf_size * nr_subbufs;
1607
1608 /* We can use multiplication to find chunks greater than 1 */
1609 if (cpu > 1) {
1610 unsigned long size;
1611 unsigned long p;
1612
1613 /* Save the beginning of this CPU chunk */
1614 p = ptr;
1615 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1616 ptr += subbuf_size * nr_subbufs;
1617
1618 /* Now all chunks after this are the same size */
1619 size = ptr - p;
1620 ptr += size * (cpu - 2);
1621 }
1622 }
1623 return (void *)ptr;
1624}
1625
1626/* Return the start of subbufs given the meta pointer */
1627static void *rb_subbufs_from_meta(struct ring_buffer_meta *meta)
1628{
1629 int subbuf_size = meta->subbuf_size;
1630 unsigned long ptr;
1631
1632 ptr = (unsigned long)meta;
1633 ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs);
1634
1635 return (void *)ptr;
1636}
1637
1638/*
1639 * Return a specific sub-buffer for a given @cpu defined by @idx.
1640 */
1641static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx)
1642{
1643 struct ring_buffer_meta *meta;
1644 unsigned long ptr;
1645 int subbuf_size;
1646
1647 meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu);
1648 if (!meta)
1649 return NULL;
1650
1651 if (WARN_ON_ONCE(idx >= meta->nr_subbufs))
1652 return NULL;
1653
1654 subbuf_size = meta->subbuf_size;
1655
1656 /* Map this buffer to the order that's in meta->buffers[] */
1657 idx = meta->buffers[idx];
1658
1659 ptr = (unsigned long)rb_subbufs_from_meta(meta);
1660
1661 ptr += subbuf_size * idx;
1662 if (ptr + subbuf_size > cpu_buffer->buffer->range_addr_end)
1663 return NULL;
1664
1665 return (void *)ptr;
1666}
1667
1668/*
1669 * See if the existing memory contains valid ring buffer data.
1670 * As the previous kernel must be the same as this kernel, all
1671 * the calculations (size of buffers and number of buffers)
1672 * must be the same.
1673 */
1674static bool rb_meta_valid(struct ring_buffer_meta *meta, int cpu,
1675 struct trace_buffer *buffer, int nr_pages,
1676 unsigned long *subbuf_mask)
1677{
1678 int subbuf_size = PAGE_SIZE;
1679 struct buffer_data_page *subbuf;
1680 unsigned long buffers_start;
1681 unsigned long buffers_end;
1682 int i;
1683
1684 if (!subbuf_mask)
1685 return false;
1686
1687 /* Check the meta magic and meta struct size */
1688 if (meta->magic != RING_BUFFER_META_MAGIC ||
1689 meta->struct_size != sizeof(*meta)) {
1690 pr_info("Ring buffer boot meta[%d] mismatch of magic or struct size\n", cpu);
1691 return false;
1692 }
1693
1694 /* The subbuffer's size and number of subbuffers must match */
1695 if (meta->subbuf_size != subbuf_size ||
1696 meta->nr_subbufs != nr_pages + 1) {
1697 pr_info("Ring buffer boot meta [%d] mismatch of subbuf_size/nr_pages\n", cpu);
1698 return false;
1699 }
1700
1701 buffers_start = meta->first_buffer;
1702 buffers_end = meta->first_buffer + (subbuf_size * meta->nr_subbufs);
1703
1704 /* Is the head and commit buffers within the range of buffers? */
1705 if (meta->head_buffer < buffers_start ||
1706 meta->head_buffer >= buffers_end) {
1707 pr_info("Ring buffer boot meta [%d] head buffer out of range\n", cpu);
1708 return false;
1709 }
1710
1711 if (meta->commit_buffer < buffers_start ||
1712 meta->commit_buffer >= buffers_end) {
1713 pr_info("Ring buffer boot meta [%d] commit buffer out of range\n", cpu);
1714 return false;
1715 }
1716
1717 subbuf = rb_subbufs_from_meta(meta);
1718
1719 bitmap_clear(subbuf_mask, 0, meta->nr_subbufs);
1720
1721 /* Is the meta buffers and the subbufs themselves have correct data? */
1722 for (i = 0; i < meta->nr_subbufs; i++) {
1723 if (meta->buffers[i] < 0 ||
1724 meta->buffers[i] >= meta->nr_subbufs) {
1725 pr_info("Ring buffer boot meta [%d] array out of range\n", cpu);
1726 return false;
1727 }
1728
1729 if ((unsigned)local_read(&subbuf->commit) > subbuf_size) {
1730 pr_info("Ring buffer boot meta [%d] buffer invalid commit\n", cpu);
1731 return false;
1732 }
1733
1734 if (test_bit(meta->buffers[i], subbuf_mask)) {
1735 pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu);
1736 return false;
1737 }
1738
1739 set_bit(meta->buffers[i], subbuf_mask);
1740 subbuf = (void *)subbuf + subbuf_size;
1741 }
1742
1743 return true;
1744}
1745
1746static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf);
1747
1748static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu,
1749 unsigned long long *timestamp, u64 *delta_ptr)
1750{
1751 struct ring_buffer_event *event;
1752 u64 ts, delta;
1753 int events = 0;
1754 int e;
1755
1756 *delta_ptr = 0;
1757 *timestamp = 0;
1758
1759 ts = dpage->time_stamp;
1760
1761 for (e = 0; e < tail; e += rb_event_length(event)) {
1762
1763 event = (struct ring_buffer_event *)(dpage->data + e);
1764
1765 switch (event->type_len) {
1766
1767 case RINGBUF_TYPE_TIME_EXTEND:
1768 delta = rb_event_time_stamp(event);
1769 ts += delta;
1770 break;
1771
1772 case RINGBUF_TYPE_TIME_STAMP:
1773 delta = rb_event_time_stamp(event);
1774 delta = rb_fix_abs_ts(delta, ts);
1775 if (delta < ts) {
1776 *delta_ptr = delta;
1777 *timestamp = ts;
1778 return -1;
1779 }
1780 ts = delta;
1781 break;
1782
1783 case RINGBUF_TYPE_PADDING:
1784 if (event->time_delta == 1)
1785 break;
1786 fallthrough;
1787 case RINGBUF_TYPE_DATA:
1788 events++;
1789 ts += event->time_delta;
1790 break;
1791
1792 default:
1793 return -1;
1794 }
1795 }
1796 *timestamp = ts;
1797 return events;
1798}
1799
1800static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu)
1801{
1802 unsigned long long ts;
1803 u64 delta;
1804 int tail;
1805
1806 tail = local_read(&dpage->commit);
1807 return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
1808}
1809
1810/* If the meta data has been validated, now validate the events */
1811static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
1812{
1813 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1814 struct buffer_page *head_page;
1815 unsigned long entry_bytes = 0;
1816 unsigned long entries = 0;
1817 int ret;
1818 int i;
1819
1820 if (!meta || !meta->head_buffer)
1821 return;
1822
1823 /* Do the reader page first */
1824 ret = rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu);
1825 if (ret < 0) {
1826 pr_info("Ring buffer reader page is invalid\n");
1827 goto invalid;
1828 }
1829 entries += ret;
1830 entry_bytes += local_read(&cpu_buffer->reader_page->page->commit);
1831 local_set(&cpu_buffer->reader_page->entries, ret);
1832
1833 head_page = cpu_buffer->head_page;
1834
1835 /* If both the head and commit are on the reader_page then we are done. */
1836 if (head_page == cpu_buffer->reader_page &&
1837 head_page == cpu_buffer->commit_page)
1838 goto done;
1839
1840 /* Iterate until finding the commit page */
1841 for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) {
1842
1843 /* Reader page has already been done */
1844 if (head_page == cpu_buffer->reader_page)
1845 continue;
1846
1847 ret = rb_validate_buffer(head_page->page, cpu_buffer->cpu);
1848 if (ret < 0) {
1849 pr_info("Ring buffer meta [%d] invalid buffer page\n",
1850 cpu_buffer->cpu);
1851 goto invalid;
1852 }
1853
1854 /* If the buffer has content, update pages_touched */
1855 if (ret)
1856 local_inc(&cpu_buffer->pages_touched);
1857
1858 entries += ret;
1859 entry_bytes += local_read(&head_page->page->commit);
1860 local_set(&cpu_buffer->head_page->entries, ret);
1861
1862 if (head_page == cpu_buffer->commit_page)
1863 break;
1864 }
1865
1866 if (head_page != cpu_buffer->commit_page) {
1867 pr_info("Ring buffer meta [%d] commit page not found\n",
1868 cpu_buffer->cpu);
1869 goto invalid;
1870 }
1871 done:
1872 local_set(&cpu_buffer->entries, entries);
1873 local_set(&cpu_buffer->entries_bytes, entry_bytes);
1874
1875 pr_info("Ring buffer meta [%d] is from previous boot!\n", cpu_buffer->cpu);
1876 return;
1877
1878 invalid:
1879 /* The content of the buffers are invalid, reset the meta data */
1880 meta->head_buffer = 0;
1881 meta->commit_buffer = 0;
1882
1883 /* Reset the reader page */
1884 local_set(&cpu_buffer->reader_page->entries, 0);
1885 local_set(&cpu_buffer->reader_page->page->commit, 0);
1886
1887 /* Reset all the subbuffers */
1888 for (i = 0; i < meta->nr_subbufs - 1; i++, rb_inc_page(&head_page)) {
1889 local_set(&head_page->entries, 0);
1890 local_set(&head_page->page->commit, 0);
1891 }
1892}
1893
1894/* Used to calculate data delta */
1895static char rb_data_ptr[] = "";
1896
1897#define THIS_TEXT_PTR ((unsigned long)rb_meta_init_text_addr)
1898#define THIS_DATA_PTR ((unsigned long)rb_data_ptr)
1899
1900static void rb_meta_init_text_addr(struct ring_buffer_meta *meta)
1901{
1902 meta->text_addr = THIS_TEXT_PTR;
1903 meta->data_addr = THIS_DATA_PTR;
1904}
1905
1906static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
1907{
1908 struct ring_buffer_meta *meta;
1909 unsigned long *subbuf_mask;
1910 unsigned long delta;
1911 void *subbuf;
1912 int cpu;
1913 int i;
1914
1915 /* Create a mask to test the subbuf array */
1916 subbuf_mask = bitmap_alloc(nr_pages + 1, GFP_KERNEL);
1917 /* If subbuf_mask fails to allocate, then rb_meta_valid() will return false */
1918
1919 for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
1920 void *next_meta;
1921
1922 meta = rb_range_meta(buffer, nr_pages, cpu);
1923
1924 if (rb_meta_valid(meta, cpu, buffer, nr_pages, subbuf_mask)) {
1925 /* Make the mappings match the current address */
1926 subbuf = rb_subbufs_from_meta(meta);
1927 delta = (unsigned long)subbuf - meta->first_buffer;
1928 meta->first_buffer += delta;
1929 meta->head_buffer += delta;
1930 meta->commit_buffer += delta;
1931 buffer->last_text_delta = THIS_TEXT_PTR - meta->text_addr;
1932 buffer->last_data_delta = THIS_DATA_PTR - meta->data_addr;
1933 continue;
1934 }
1935
1936 if (cpu < nr_cpu_ids - 1)
1937 next_meta = rb_range_meta(buffer, nr_pages, cpu + 1);
1938 else
1939 next_meta = (void *)buffer->range_addr_end;
1940
1941 memset(meta, 0, next_meta - (void *)meta);
1942
1943 meta->magic = RING_BUFFER_META_MAGIC;
1944 meta->struct_size = sizeof(*meta);
1945
1946 meta->nr_subbufs = nr_pages + 1;
1947 meta->subbuf_size = PAGE_SIZE;
1948
1949 subbuf = rb_subbufs_from_meta(meta);
1950
1951 meta->first_buffer = (unsigned long)subbuf;
1952 rb_meta_init_text_addr(meta);
1953
1954 /*
1955 * The buffers[] array holds the order of the sub-buffers
1956 * that are after the meta data. The sub-buffers may
1957 * be swapped out when read and inserted into a different
1958 * location of the ring buffer. Although their addresses
1959 * remain the same, the buffers[] array contains the
1960 * index into the sub-buffers holding their actual order.
1961 */
1962 for (i = 0; i < meta->nr_subbufs; i++) {
1963 meta->buffers[i] = i;
1964 rb_init_page(subbuf);
1965 subbuf += meta->subbuf_size;
1966 }
1967 }
1968 bitmap_free(subbuf_mask);
1969}
1970
1971static void *rbm_start(struct seq_file *m, loff_t *pos)
1972{
1973 struct ring_buffer_per_cpu *cpu_buffer = m->private;
1974 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1975 unsigned long val;
1976
1977 if (!meta)
1978 return NULL;
1979
1980 if (*pos > meta->nr_subbufs)
1981 return NULL;
1982
1983 val = *pos;
1984 val++;
1985
1986 return (void *)val;
1987}
1988
1989static void *rbm_next(struct seq_file *m, void *v, loff_t *pos)
1990{
1991 (*pos)++;
1992
1993 return rbm_start(m, pos);
1994}
1995
1996static int rbm_show(struct seq_file *m, void *v)
1997{
1998 struct ring_buffer_per_cpu *cpu_buffer = m->private;
1999 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
2000 unsigned long val = (unsigned long)v;
2001
2002 if (val == 1) {
2003 seq_printf(m, "head_buffer: %d\n",
2004 rb_meta_subbuf_idx(meta, (void *)meta->head_buffer));
2005 seq_printf(m, "commit_buffer: %d\n",
2006 rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer));
2007 seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size);
2008 seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs);
2009 return 0;
2010 }
2011
2012 val -= 2;
2013 seq_printf(m, "buffer[%ld]: %d\n", val, meta->buffers[val]);
2014
2015 return 0;
2016}
2017
2018static void rbm_stop(struct seq_file *m, void *p)
2019{
2020}
2021
2022static const struct seq_operations rb_meta_seq_ops = {
2023 .start = rbm_start,
2024 .next = rbm_next,
2025 .show = rbm_show,
2026 .stop = rbm_stop,
2027};
2028
2029int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, int cpu)
2030{
2031 struct seq_file *m;
2032 int ret;
2033
2034 ret = seq_open(file, &rb_meta_seq_ops);
2035 if (ret)
2036 return ret;
2037
2038 m = file->private_data;
2039 m->private = buffer->buffers[cpu];
2040
2041 return 0;
2042}
2043
2044/* Map the buffer_pages to the previous head and commit pages */
2045static void rb_meta_buffer_update(struct ring_buffer_per_cpu *cpu_buffer,
2046 struct buffer_page *bpage)
2047{
2048 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
2049
2050 if (meta->head_buffer == (unsigned long)bpage->page)
2051 cpu_buffer->head_page = bpage;
2052
2053 if (meta->commit_buffer == (unsigned long)bpage->page) {
2054 cpu_buffer->commit_page = bpage;
2055 cpu_buffer->tail_page = bpage;
2056 }
2057}
2058
2059static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2060 long nr_pages, struct list_head *pages)
2061{
2062 struct trace_buffer *buffer = cpu_buffer->buffer;
2063 struct ring_buffer_meta *meta = NULL;
2064 struct buffer_page *bpage, *tmp;
2065 bool user_thread = current->mm != NULL;
2066 gfp_t mflags;
2067 long i;
2068
2069 /*
2070 * Check if the available memory is there first.
2071 * Note, si_mem_available() only gives us a rough estimate of available
2072 * memory. It may not be accurate. But we don't care, we just want
2073 * to prevent doing any allocation when it is obvious that it is
2074 * not going to succeed.
2075 */
2076 i = si_mem_available();
2077 if (i < nr_pages)
2078 return -ENOMEM;
2079
2080 /*
2081 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
2082 * gracefully without invoking oom-killer and the system is not
2083 * destabilized.
2084 */
2085 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
2086
2087 /*
2088 * If a user thread allocates too much, and si_mem_available()
2089 * reports there's enough memory, even though there is not.
2090 * Make sure the OOM killer kills this thread. This can happen
2091 * even with RETRY_MAYFAIL because another task may be doing
2092 * an allocation after this task has taken all memory.
2093 * This is the task the OOM killer needs to take out during this
2094 * loop, even if it was triggered by an allocation somewhere else.
2095 */
2096 if (user_thread)
2097 set_current_oom_origin();
2098
2099 if (buffer->range_addr_start)
2100 meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
2101
2102 for (i = 0; i < nr_pages; i++) {
2103 struct page *page;
2104
2105 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2106 mflags, cpu_to_node(cpu_buffer->cpu));
2107 if (!bpage)
2108 goto free_pages;
2109
2110 rb_check_bpage(cpu_buffer, bpage);
2111
2112 /*
2113 * Append the pages as for mapped buffers we want to keep
2114 * the order
2115 */
2116 list_add_tail(&bpage->list, pages);
2117
2118 if (meta) {
2119 /* A range was given. Use that for the buffer page */
2120 bpage->page = rb_range_buffer(cpu_buffer, i + 1);
2121 if (!bpage->page)
2122 goto free_pages;
2123 /* If this is valid from a previous boot */
2124 if (meta->head_buffer)
2125 rb_meta_buffer_update(cpu_buffer, bpage);
2126 bpage->range = 1;
2127 bpage->id = i + 1;
2128 } else {
2129 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
2130 mflags | __GFP_COMP | __GFP_ZERO,
2131 cpu_buffer->buffer->subbuf_order);
2132 if (!page)
2133 goto free_pages;
2134 bpage->page = page_address(page);
2135 rb_init_page(bpage->page);
2136 }
2137 bpage->order = cpu_buffer->buffer->subbuf_order;
2138
2139 if (user_thread && fatal_signal_pending(current))
2140 goto free_pages;
2141 }
2142 if (user_thread)
2143 clear_current_oom_origin();
2144
2145 return 0;
2146
2147free_pages:
2148 list_for_each_entry_safe(bpage, tmp, pages, list) {
2149 list_del_init(&bpage->list);
2150 free_buffer_page(bpage);
2151 }
2152 if (user_thread)
2153 clear_current_oom_origin();
2154
2155 return -ENOMEM;
2156}
2157
2158static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2159 unsigned long nr_pages)
2160{
2161 LIST_HEAD(pages);
2162
2163 WARN_ON(!nr_pages);
2164
2165 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
2166 return -ENOMEM;
2167
2168 /*
2169 * The ring buffer page list is a circular list that does not
2170 * start and end with a list head. All page list items point to
2171 * other pages.
2172 */
2173 cpu_buffer->pages = pages.next;
2174 list_del(&pages);
2175
2176 cpu_buffer->nr_pages = nr_pages;
2177
2178 rb_check_pages(cpu_buffer);
2179
2180 return 0;
2181}
2182
2183static struct ring_buffer_per_cpu *
2184rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
2185{
2186 struct ring_buffer_per_cpu *cpu_buffer;
2187 struct ring_buffer_meta *meta;
2188 struct buffer_page *bpage;
2189 struct page *page;
2190 int ret;
2191
2192 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
2193 GFP_KERNEL, cpu_to_node(cpu));
2194 if (!cpu_buffer)
2195 return NULL;
2196
2197 cpu_buffer->cpu = cpu;
2198 cpu_buffer->buffer = buffer;
2199 raw_spin_lock_init(&cpu_buffer->reader_lock);
2200 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
2201 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
2202 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
2203 init_completion(&cpu_buffer->update_done);
2204 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
2205 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
2206 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
2207 mutex_init(&cpu_buffer->mapping_lock);
2208
2209 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2210 GFP_KERNEL, cpu_to_node(cpu));
2211 if (!bpage)
2212 goto fail_free_buffer;
2213
2214 rb_check_bpage(cpu_buffer, bpage);
2215
2216 cpu_buffer->reader_page = bpage;
2217
2218 if (buffer->range_addr_start) {
2219 /*
2220 * Range mapped buffers have the same restrictions as memory
2221 * mapped ones do.
2222 */
2223 cpu_buffer->mapped = 1;
2224 cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu);
2225 bpage->page = rb_range_buffer(cpu_buffer, 0);
2226 if (!bpage->page)
2227 goto fail_free_reader;
2228 if (cpu_buffer->ring_meta->head_buffer)
2229 rb_meta_buffer_update(cpu_buffer, bpage);
2230 bpage->range = 1;
2231 } else {
2232 page = alloc_pages_node(cpu_to_node(cpu),
2233 GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
2234 cpu_buffer->buffer->subbuf_order);
2235 if (!page)
2236 goto fail_free_reader;
2237 bpage->page = page_address(page);
2238 rb_init_page(bpage->page);
2239 }
2240
2241 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2242 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2243
2244 ret = rb_allocate_pages(cpu_buffer, nr_pages);
2245 if (ret < 0)
2246 goto fail_free_reader;
2247
2248 rb_meta_validate_events(cpu_buffer);
2249
2250 /* If the boot meta was valid then this has already been updated */
2251 meta = cpu_buffer->ring_meta;
2252 if (!meta || !meta->head_buffer ||
2253 !cpu_buffer->head_page || !cpu_buffer->commit_page || !cpu_buffer->tail_page) {
2254 if (meta && meta->head_buffer &&
2255 (cpu_buffer->head_page || cpu_buffer->commit_page || cpu_buffer->tail_page)) {
2256 pr_warn("Ring buffer meta buffers not all mapped\n");
2257 if (!cpu_buffer->head_page)
2258 pr_warn(" Missing head_page\n");
2259 if (!cpu_buffer->commit_page)
2260 pr_warn(" Missing commit_page\n");
2261 if (!cpu_buffer->tail_page)
2262 pr_warn(" Missing tail_page\n");
2263 }
2264
2265 cpu_buffer->head_page
2266 = list_entry(cpu_buffer->pages, struct buffer_page, list);
2267 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
2268
2269 rb_head_page_activate(cpu_buffer);
2270
2271 if (cpu_buffer->ring_meta)
2272 meta->commit_buffer = meta->head_buffer;
2273 } else {
2274 /* The valid meta buffer still needs to activate the head page */
2275 rb_head_page_activate(cpu_buffer);
2276 }
2277
2278 return cpu_buffer;
2279
2280 fail_free_reader:
2281 free_buffer_page(cpu_buffer->reader_page);
2282
2283 fail_free_buffer:
2284 kfree(cpu_buffer);
2285 return NULL;
2286}
2287
2288static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
2289{
2290 struct list_head *head = cpu_buffer->pages;
2291 struct buffer_page *bpage, *tmp;
2292
2293 irq_work_sync(&cpu_buffer->irq_work.work);
2294
2295 free_buffer_page(cpu_buffer->reader_page);
2296
2297 if (head) {
2298 rb_head_page_deactivate(cpu_buffer);
2299
2300 list_for_each_entry_safe(bpage, tmp, head, list) {
2301 list_del_init(&bpage->list);
2302 free_buffer_page(bpage);
2303 }
2304 bpage = list_entry(head, struct buffer_page, list);
2305 free_buffer_page(bpage);
2306 }
2307
2308 free_page((unsigned long)cpu_buffer->free_page);
2309
2310 kfree(cpu_buffer);
2311}
2312
2313static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
2314 int order, unsigned long start,
2315 unsigned long end,
2316 struct lock_class_key *key)
2317{
2318 struct trace_buffer *buffer;
2319 long nr_pages;
2320 int subbuf_size;
2321 int bsize;
2322 int cpu;
2323 int ret;
2324
2325 /* keep it in its own cache line */
2326 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
2327 GFP_KERNEL);
2328 if (!buffer)
2329 return NULL;
2330
2331 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
2332 goto fail_free_buffer;
2333
2334 buffer->subbuf_order = order;
2335 subbuf_size = (PAGE_SIZE << order);
2336 buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
2337
2338 /* Max payload is buffer page size - header (8bytes) */
2339 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
2340
2341 buffer->flags = flags;
2342 buffer->clock = trace_clock_local;
2343 buffer->reader_lock_key = key;
2344
2345 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
2346 init_waitqueue_head(&buffer->irq_work.waiters);
2347
2348 buffer->cpus = nr_cpu_ids;
2349
2350 bsize = sizeof(void *) * nr_cpu_ids;
2351 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
2352 GFP_KERNEL);
2353 if (!buffer->buffers)
2354 goto fail_free_cpumask;
2355
2356 /* If start/end are specified, then that overrides size */
2357 if (start && end) {
2358 unsigned long ptr;
2359 int n;
2360
2361 size = end - start;
2362 size = size / nr_cpu_ids;
2363
2364 /*
2365 * The number of sub-buffers (nr_pages) is determined by the
2366 * total size allocated minus the meta data size.
2367 * Then that is divided by the number of per CPU buffers
2368 * needed, plus account for the integer array index that
2369 * will be appended to the meta data.
2370 */
2371 nr_pages = (size - sizeof(struct ring_buffer_meta)) /
2372 (subbuf_size + sizeof(int));
2373 /* Need at least two pages plus the reader page */
2374 if (nr_pages < 3)
2375 goto fail_free_buffers;
2376
2377 again:
2378 /* Make sure that the size fits aligned */
2379 for (n = 0, ptr = start; n < nr_cpu_ids; n++) {
2380 ptr += sizeof(struct ring_buffer_meta) +
2381 sizeof(int) * nr_pages;
2382 ptr = ALIGN(ptr, subbuf_size);
2383 ptr += subbuf_size * nr_pages;
2384 }
2385 if (ptr > end) {
2386 if (nr_pages <= 3)
2387 goto fail_free_buffers;
2388 nr_pages--;
2389 goto again;
2390 }
2391
2392 /* nr_pages should not count the reader page */
2393 nr_pages--;
2394 buffer->range_addr_start = start;
2395 buffer->range_addr_end = end;
2396
2397 rb_range_meta_init(buffer, nr_pages);
2398 } else {
2399
2400 /* need at least two pages */
2401 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2402 if (nr_pages < 2)
2403 nr_pages = 2;
2404 }
2405
2406 cpu = raw_smp_processor_id();
2407 cpumask_set_cpu(cpu, buffer->cpumask);
2408 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
2409 if (!buffer->buffers[cpu])
2410 goto fail_free_buffers;
2411
2412 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2413 if (ret < 0)
2414 goto fail_free_buffers;
2415
2416 mutex_init(&buffer->mutex);
2417
2418 return buffer;
2419
2420 fail_free_buffers:
2421 for_each_buffer_cpu(buffer, cpu) {
2422 if (buffer->buffers[cpu])
2423 rb_free_cpu_buffer(buffer->buffers[cpu]);
2424 }
2425 kfree(buffer->buffers);
2426
2427 fail_free_cpumask:
2428 free_cpumask_var(buffer->cpumask);
2429
2430 fail_free_buffer:
2431 kfree(buffer);
2432 return NULL;
2433}
2434
2435/**
2436 * __ring_buffer_alloc - allocate a new ring_buffer
2437 * @size: the size in bytes per cpu that is needed.
2438 * @flags: attributes to set for the ring buffer.
2439 * @key: ring buffer reader_lock_key.
2440 *
2441 * Currently the only flag that is available is the RB_FL_OVERWRITE
2442 * flag. This flag means that the buffer will overwrite old data
2443 * when the buffer wraps. If this flag is not set, the buffer will
2444 * drop data when the tail hits the head.
2445 */
2446struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
2447 struct lock_class_key *key)
2448{
2449 /* Default buffer page size - one system page */
2450 return alloc_buffer(size, flags, 0, 0, 0,key);
2451
2452}
2453EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
2454
2455/**
2456 * __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory
2457 * @size: the size in bytes per cpu that is needed.
2458 * @flags: attributes to set for the ring buffer.
2459 * @order: sub-buffer order
2460 * @start: start of allocated range
2461 * @range_size: size of allocated range
2462 * @key: ring buffer reader_lock_key.
2463 *
2464 * Currently the only flag that is available is the RB_FL_OVERWRITE
2465 * flag. This flag means that the buffer will overwrite old data
2466 * when the buffer wraps. If this flag is not set, the buffer will
2467 * drop data when the tail hits the head.
2468 */
2469struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
2470 int order, unsigned long start,
2471 unsigned long range_size,
2472 struct lock_class_key *key)
2473{
2474 return alloc_buffer(size, flags, order, start, start + range_size, key);
2475}
2476
2477/**
2478 * ring_buffer_last_boot_delta - return the delta offset from last boot
2479 * @buffer: The buffer to return the delta from
2480 * @text: Return text delta
2481 * @data: Return data delta
2482 *
2483 * Returns: The true if the delta is non zero
2484 */
2485bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text,
2486 long *data)
2487{
2488 if (!buffer)
2489 return false;
2490
2491 if (!buffer->last_text_delta)
2492 return false;
2493
2494 *text = buffer->last_text_delta;
2495 *data = buffer->last_data_delta;
2496
2497 return true;
2498}
2499
2500/**
2501 * ring_buffer_free - free a ring buffer.
2502 * @buffer: the buffer to free.
2503 */
2504void
2505ring_buffer_free(struct trace_buffer *buffer)
2506{
2507 int cpu;
2508
2509 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2510
2511 irq_work_sync(&buffer->irq_work.work);
2512
2513 for_each_buffer_cpu(buffer, cpu)
2514 rb_free_cpu_buffer(buffer->buffers[cpu]);
2515
2516 kfree(buffer->buffers);
2517 free_cpumask_var(buffer->cpumask);
2518
2519 kfree(buffer);
2520}
2521EXPORT_SYMBOL_GPL(ring_buffer_free);
2522
2523void ring_buffer_set_clock(struct trace_buffer *buffer,
2524 u64 (*clock)(void))
2525{
2526 buffer->clock = clock;
2527}
2528
2529void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
2530{
2531 buffer->time_stamp_abs = abs;
2532}
2533
2534bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
2535{
2536 return buffer->time_stamp_abs;
2537}
2538
2539static inline unsigned long rb_page_entries(struct buffer_page *bpage)
2540{
2541 return local_read(&bpage->entries) & RB_WRITE_MASK;
2542}
2543
2544static inline unsigned long rb_page_write(struct buffer_page *bpage)
2545{
2546 return local_read(&bpage->write) & RB_WRITE_MASK;
2547}
2548
2549static bool
2550rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
2551{
2552 struct list_head *tail_page, *to_remove, *next_page;
2553 struct buffer_page *to_remove_page, *tmp_iter_page;
2554 struct buffer_page *last_page, *first_page;
2555 unsigned long nr_removed;
2556 unsigned long head_bit;
2557 int page_entries;
2558
2559 head_bit = 0;
2560
2561 raw_spin_lock_irq(&cpu_buffer->reader_lock);
2562 atomic_inc(&cpu_buffer->record_disabled);
2563 /*
2564 * We don't race with the readers since we have acquired the reader
2565 * lock. We also don't race with writers after disabling recording.
2566 * This makes it easy to figure out the first and the last page to be
2567 * removed from the list. We unlink all the pages in between including
2568 * the first and last pages. This is done in a busy loop so that we
2569 * lose the least number of traces.
2570 * The pages are freed after we restart recording and unlock readers.
2571 */
2572 tail_page = &cpu_buffer->tail_page->list;
2573
2574 /*
2575 * tail page might be on reader page, we remove the next page
2576 * from the ring buffer
2577 */
2578 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
2579 tail_page = rb_list_head(tail_page->next);
2580 to_remove = tail_page;
2581
2582 /* start of pages to remove */
2583 first_page = list_entry(rb_list_head(to_remove->next),
2584 struct buffer_page, list);
2585
2586 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
2587 to_remove = rb_list_head(to_remove)->next;
2588 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
2589 }
2590 /* Read iterators need to reset themselves when some pages removed */
2591 cpu_buffer->pages_removed += nr_removed;
2592
2593 next_page = rb_list_head(to_remove)->next;
2594
2595 /*
2596 * Now we remove all pages between tail_page and next_page.
2597 * Make sure that we have head_bit value preserved for the
2598 * next page
2599 */
2600 tail_page->next = (struct list_head *)((unsigned long)next_page |
2601 head_bit);
2602 next_page = rb_list_head(next_page);
2603 next_page->prev = tail_page;
2604
2605 /* make sure pages points to a valid page in the ring buffer */
2606 cpu_buffer->pages = next_page;
2607 cpu_buffer->cnt++;
2608
2609 /* update head page */
2610 if (head_bit)
2611 cpu_buffer->head_page = list_entry(next_page,
2612 struct buffer_page, list);
2613
2614 /* pages are removed, resume tracing and then free the pages */
2615 atomic_dec(&cpu_buffer->record_disabled);
2616 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2617
2618 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
2619
2620 /* last buffer page to remove */
2621 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
2622 list);
2623 tmp_iter_page = first_page;
2624
2625 do {
2626 cond_resched();
2627
2628 to_remove_page = tmp_iter_page;
2629 rb_inc_page(&tmp_iter_page);
2630
2631 /* update the counters */
2632 page_entries = rb_page_entries(to_remove_page);
2633 if (page_entries) {
2634 /*
2635 * If something was added to this page, it was full
2636 * since it is not the tail page. So we deduct the
2637 * bytes consumed in ring buffer from here.
2638 * Increment overrun to account for the lost events.
2639 */
2640 local_add(page_entries, &cpu_buffer->overrun);
2641 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
2642 local_inc(&cpu_buffer->pages_lost);
2643 }
2644
2645 /*
2646 * We have already removed references to this list item, just
2647 * free up the buffer_page and its page
2648 */
2649 free_buffer_page(to_remove_page);
2650 nr_removed--;
2651
2652 } while (to_remove_page != last_page);
2653
2654 RB_WARN_ON(cpu_buffer, nr_removed);
2655
2656 return nr_removed == 0;
2657}
2658
2659static bool
2660rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
2661{
2662 struct list_head *pages = &cpu_buffer->new_pages;
2663 unsigned long flags;
2664 bool success;
2665 int retries;
2666
2667 /* Can be called at early boot up, where interrupts must not been enabled */
2668 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2669 /*
2670 * We are holding the reader lock, so the reader page won't be swapped
2671 * in the ring buffer. Now we are racing with the writer trying to
2672 * move head page and the tail page.
2673 * We are going to adapt the reader page update process where:
2674 * 1. We first splice the start and end of list of new pages between
2675 * the head page and its previous page.
2676 * 2. We cmpxchg the prev_page->next to point from head page to the
2677 * start of new pages list.
2678 * 3. Finally, we update the head->prev to the end of new list.
2679 *
2680 * We will try this process 10 times, to make sure that we don't keep
2681 * spinning.
2682 */
2683 retries = 10;
2684 success = false;
2685 while (retries--) {
2686 struct list_head *head_page, *prev_page;
2687 struct list_head *last_page, *first_page;
2688 struct list_head *head_page_with_bit;
2689 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
2690
2691 if (!hpage)
2692 break;
2693 head_page = &hpage->list;
2694 prev_page = head_page->prev;
2695
2696 first_page = pages->next;
2697 last_page = pages->prev;
2698
2699 head_page_with_bit = (struct list_head *)
2700 ((unsigned long)head_page | RB_PAGE_HEAD);
2701
2702 last_page->next = head_page_with_bit;
2703 first_page->prev = prev_page;
2704
2705 /* caution: head_page_with_bit gets updated on cmpxchg failure */
2706 if (try_cmpxchg(&prev_page->next,
2707 &head_page_with_bit, first_page)) {
2708 /*
2709 * yay, we replaced the page pointer to our new list,
2710 * now, we just have to update to head page's prev
2711 * pointer to point to end of list
2712 */
2713 head_page->prev = last_page;
2714 cpu_buffer->cnt++;
2715 success = true;
2716 break;
2717 }
2718 }
2719
2720 if (success)
2721 INIT_LIST_HEAD(pages);
2722 /*
2723 * If we weren't successful in adding in new pages, warn and stop
2724 * tracing
2725 */
2726 RB_WARN_ON(cpu_buffer, !success);
2727 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2728
2729 /* free pages if they weren't inserted */
2730 if (!success) {
2731 struct buffer_page *bpage, *tmp;
2732 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2733 list) {
2734 list_del_init(&bpage->list);
2735 free_buffer_page(bpage);
2736 }
2737 }
2738 return success;
2739}
2740
2741static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2742{
2743 bool success;
2744
2745 if (cpu_buffer->nr_pages_to_update > 0)
2746 success = rb_insert_pages(cpu_buffer);
2747 else
2748 success = rb_remove_pages(cpu_buffer,
2749 -cpu_buffer->nr_pages_to_update);
2750
2751 if (success)
2752 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2753}
2754
2755static void update_pages_handler(struct work_struct *work)
2756{
2757 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2758 struct ring_buffer_per_cpu, update_pages_work);
2759 rb_update_pages(cpu_buffer);
2760 complete(&cpu_buffer->update_done);
2761}
2762
2763/**
2764 * ring_buffer_resize - resize the ring buffer
2765 * @buffer: the buffer to resize.
2766 * @size: the new size.
2767 * @cpu_id: the cpu buffer to resize
2768 *
2769 * Minimum size is 2 * buffer->subbuf_size.
2770 *
2771 * Returns 0 on success and < 0 on failure.
2772 */
2773int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2774 int cpu_id)
2775{
2776 struct ring_buffer_per_cpu *cpu_buffer;
2777 unsigned long nr_pages;
2778 int cpu, err;
2779
2780 /*
2781 * Always succeed at resizing a non-existent buffer:
2782 */
2783 if (!buffer)
2784 return 0;
2785
2786 /* Make sure the requested buffer exists */
2787 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2788 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2789 return 0;
2790
2791 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2792
2793 /* we need a minimum of two pages */
2794 if (nr_pages < 2)
2795 nr_pages = 2;
2796
2797 /* prevent another thread from changing buffer sizes */
2798 mutex_lock(&buffer->mutex);
2799 atomic_inc(&buffer->resizing);
2800
2801 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2802 /*
2803 * Don't succeed if resizing is disabled, as a reader might be
2804 * manipulating the ring buffer and is expecting a sane state while
2805 * this is true.
2806 */
2807 for_each_buffer_cpu(buffer, cpu) {
2808 cpu_buffer = buffer->buffers[cpu];
2809 if (atomic_read(&cpu_buffer->resize_disabled)) {
2810 err = -EBUSY;
2811 goto out_err_unlock;
2812 }
2813 }
2814
2815 /* calculate the pages to update */
2816 for_each_buffer_cpu(buffer, cpu) {
2817 cpu_buffer = buffer->buffers[cpu];
2818
2819 cpu_buffer->nr_pages_to_update = nr_pages -
2820 cpu_buffer->nr_pages;
2821 /*
2822 * nothing more to do for removing pages or no update
2823 */
2824 if (cpu_buffer->nr_pages_to_update <= 0)
2825 continue;
2826 /*
2827 * to add pages, make sure all new pages can be
2828 * allocated without receiving ENOMEM
2829 */
2830 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2831 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2832 &cpu_buffer->new_pages)) {
2833 /* not enough memory for new pages */
2834 err = -ENOMEM;
2835 goto out_err;
2836 }
2837
2838 cond_resched();
2839 }
2840
2841 cpus_read_lock();
2842 /*
2843 * Fire off all the required work handlers
2844 * We can't schedule on offline CPUs, but it's not necessary
2845 * since we can change their buffer sizes without any race.
2846 */
2847 for_each_buffer_cpu(buffer, cpu) {
2848 cpu_buffer = buffer->buffers[cpu];
2849 if (!cpu_buffer->nr_pages_to_update)
2850 continue;
2851
2852 /* Can't run something on an offline CPU. */
2853 if (!cpu_online(cpu)) {
2854 rb_update_pages(cpu_buffer);
2855 cpu_buffer->nr_pages_to_update = 0;
2856 } else {
2857 /* Run directly if possible. */
2858 migrate_disable();
2859 if (cpu != smp_processor_id()) {
2860 migrate_enable();
2861 schedule_work_on(cpu,
2862 &cpu_buffer->update_pages_work);
2863 } else {
2864 update_pages_handler(&cpu_buffer->update_pages_work);
2865 migrate_enable();
2866 }
2867 }
2868 }
2869
2870 /* wait for all the updates to complete */
2871 for_each_buffer_cpu(buffer, cpu) {
2872 cpu_buffer = buffer->buffers[cpu];
2873 if (!cpu_buffer->nr_pages_to_update)
2874 continue;
2875
2876 if (cpu_online(cpu))
2877 wait_for_completion(&cpu_buffer->update_done);
2878 cpu_buffer->nr_pages_to_update = 0;
2879 }
2880
2881 cpus_read_unlock();
2882 } else {
2883 cpu_buffer = buffer->buffers[cpu_id];
2884
2885 if (nr_pages == cpu_buffer->nr_pages)
2886 goto out;
2887
2888 /*
2889 * Don't succeed if resizing is disabled, as a reader might be
2890 * manipulating the ring buffer and is expecting a sane state while
2891 * this is true.
2892 */
2893 if (atomic_read(&cpu_buffer->resize_disabled)) {
2894 err = -EBUSY;
2895 goto out_err_unlock;
2896 }
2897
2898 cpu_buffer->nr_pages_to_update = nr_pages -
2899 cpu_buffer->nr_pages;
2900
2901 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2902 if (cpu_buffer->nr_pages_to_update > 0 &&
2903 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2904 &cpu_buffer->new_pages)) {
2905 err = -ENOMEM;
2906 goto out_err;
2907 }
2908
2909 cpus_read_lock();
2910
2911 /* Can't run something on an offline CPU. */
2912 if (!cpu_online(cpu_id))
2913 rb_update_pages(cpu_buffer);
2914 else {
2915 /* Run directly if possible. */
2916 migrate_disable();
2917 if (cpu_id == smp_processor_id()) {
2918 rb_update_pages(cpu_buffer);
2919 migrate_enable();
2920 } else {
2921 migrate_enable();
2922 schedule_work_on(cpu_id,
2923 &cpu_buffer->update_pages_work);
2924 wait_for_completion(&cpu_buffer->update_done);
2925 }
2926 }
2927
2928 cpu_buffer->nr_pages_to_update = 0;
2929 cpus_read_unlock();
2930 }
2931
2932 out:
2933 /*
2934 * The ring buffer resize can happen with the ring buffer
2935 * enabled, so that the update disturbs the tracing as little
2936 * as possible. But if the buffer is disabled, we do not need
2937 * to worry about that, and we can take the time to verify
2938 * that the buffer is not corrupt.
2939 */
2940 if (atomic_read(&buffer->record_disabled)) {
2941 atomic_inc(&buffer->record_disabled);
2942 /*
2943 * Even though the buffer was disabled, we must make sure
2944 * that it is truly disabled before calling rb_check_pages.
2945 * There could have been a race between checking
2946 * record_disable and incrementing it.
2947 */
2948 synchronize_rcu();
2949 for_each_buffer_cpu(buffer, cpu) {
2950 cpu_buffer = buffer->buffers[cpu];
2951 rb_check_pages(cpu_buffer);
2952 }
2953 atomic_dec(&buffer->record_disabled);
2954 }
2955
2956 atomic_dec(&buffer->resizing);
2957 mutex_unlock(&buffer->mutex);
2958 return 0;
2959
2960 out_err:
2961 for_each_buffer_cpu(buffer, cpu) {
2962 struct buffer_page *bpage, *tmp;
2963
2964 cpu_buffer = buffer->buffers[cpu];
2965 cpu_buffer->nr_pages_to_update = 0;
2966
2967 if (list_empty(&cpu_buffer->new_pages))
2968 continue;
2969
2970 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2971 list) {
2972 list_del_init(&bpage->list);
2973 free_buffer_page(bpage);
2974 }
2975 }
2976 out_err_unlock:
2977 atomic_dec(&buffer->resizing);
2978 mutex_unlock(&buffer->mutex);
2979 return err;
2980}
2981EXPORT_SYMBOL_GPL(ring_buffer_resize);
2982
2983void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2984{
2985 mutex_lock(&buffer->mutex);
2986 if (val)
2987 buffer->flags |= RB_FL_OVERWRITE;
2988 else
2989 buffer->flags &= ~RB_FL_OVERWRITE;
2990 mutex_unlock(&buffer->mutex);
2991}
2992EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2993
2994static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2995{
2996 return bpage->page->data + index;
2997}
2998
2999static __always_inline struct ring_buffer_event *
3000rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
3001{
3002 return __rb_page_index(cpu_buffer->reader_page,
3003 cpu_buffer->reader_page->read);
3004}
3005
3006static struct ring_buffer_event *
3007rb_iter_head_event(struct ring_buffer_iter *iter)
3008{
3009 struct ring_buffer_event *event;
3010 struct buffer_page *iter_head_page = iter->head_page;
3011 unsigned long commit;
3012 unsigned length;
3013
3014 if (iter->head != iter->next_event)
3015 return iter->event;
3016
3017 /*
3018 * When the writer goes across pages, it issues a cmpxchg which
3019 * is a mb(), which will synchronize with the rmb here.
3020 * (see rb_tail_page_update() and __rb_reserve_next())
3021 */
3022 commit = rb_page_commit(iter_head_page);
3023 smp_rmb();
3024
3025 /* An event needs to be at least 8 bytes in size */
3026 if (iter->head > commit - 8)
3027 goto reset;
3028
3029 event = __rb_page_index(iter_head_page, iter->head);
3030 length = rb_event_length(event);
3031
3032 /*
3033 * READ_ONCE() doesn't work on functions and we don't want the
3034 * compiler doing any crazy optimizations with length.
3035 */
3036 barrier();
3037
3038 if ((iter->head + length) > commit || length > iter->event_size)
3039 /* Writer corrupted the read? */
3040 goto reset;
3041
3042 memcpy(iter->event, event, length);
3043 /*
3044 * If the page stamp is still the same after this rmb() then the
3045 * event was safely copied without the writer entering the page.
3046 */
3047 smp_rmb();
3048
3049 /* Make sure the page didn't change since we read this */
3050 if (iter->page_stamp != iter_head_page->page->time_stamp ||
3051 commit > rb_page_commit(iter_head_page))
3052 goto reset;
3053
3054 iter->next_event = iter->head + length;
3055 return iter->event;
3056 reset:
3057 /* Reset to the beginning */
3058 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3059 iter->head = 0;
3060 iter->next_event = 0;
3061 iter->missed_events = 1;
3062 return NULL;
3063}
3064
3065/* Size is determined by what has been committed */
3066static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
3067{
3068 return rb_page_commit(bpage) & ~RB_MISSED_MASK;
3069}
3070
3071static __always_inline unsigned
3072rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
3073{
3074 return rb_page_commit(cpu_buffer->commit_page);
3075}
3076
3077static __always_inline unsigned
3078rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
3079{
3080 unsigned long addr = (unsigned long)event;
3081
3082 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
3083
3084 return addr - BUF_PAGE_HDR_SIZE;
3085}
3086
3087static void rb_inc_iter(struct ring_buffer_iter *iter)
3088{
3089 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3090
3091 /*
3092 * The iterator could be on the reader page (it starts there).
3093 * But the head could have moved, since the reader was
3094 * found. Check for this case and assign the iterator
3095 * to the head page instead of next.
3096 */
3097 if (iter->head_page == cpu_buffer->reader_page)
3098 iter->head_page = rb_set_head_page(cpu_buffer);
3099 else
3100 rb_inc_page(&iter->head_page);
3101
3102 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3103 iter->head = 0;
3104 iter->next_event = 0;
3105}
3106
3107/* Return the index into the sub-buffers for a given sub-buffer */
3108static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf)
3109{
3110 void *subbuf_array;
3111
3112 subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs;
3113 subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size);
3114 return (subbuf - subbuf_array) / meta->subbuf_size;
3115}
3116
3117static void rb_update_meta_head(struct ring_buffer_per_cpu *cpu_buffer,
3118 struct buffer_page *next_page)
3119{
3120 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3121 unsigned long old_head = (unsigned long)next_page->page;
3122 unsigned long new_head;
3123
3124 rb_inc_page(&next_page);
3125 new_head = (unsigned long)next_page->page;
3126
3127 /*
3128 * Only move it forward once, if something else came in and
3129 * moved it forward, then we don't want to touch it.
3130 */
3131 (void)cmpxchg(&meta->head_buffer, old_head, new_head);
3132}
3133
3134static void rb_update_meta_reader(struct ring_buffer_per_cpu *cpu_buffer,
3135 struct buffer_page *reader)
3136{
3137 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3138 void *old_reader = cpu_buffer->reader_page->page;
3139 void *new_reader = reader->page;
3140 int id;
3141
3142 id = reader->id;
3143 cpu_buffer->reader_page->id = id;
3144 reader->id = 0;
3145
3146 meta->buffers[0] = rb_meta_subbuf_idx(meta, new_reader);
3147 meta->buffers[id] = rb_meta_subbuf_idx(meta, old_reader);
3148
3149 /* The head pointer is the one after the reader */
3150 rb_update_meta_head(cpu_buffer, reader);
3151}
3152
3153/*
3154 * rb_handle_head_page - writer hit the head page
3155 *
3156 * Returns: +1 to retry page
3157 * 0 to continue
3158 * -1 on error
3159 */
3160static int
3161rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
3162 struct buffer_page *tail_page,
3163 struct buffer_page *next_page)
3164{
3165 struct buffer_page *new_head;
3166 int entries;
3167 int type;
3168 int ret;
3169
3170 entries = rb_page_entries(next_page);
3171
3172 /*
3173 * The hard part is here. We need to move the head
3174 * forward, and protect against both readers on
3175 * other CPUs and writers coming in via interrupts.
3176 */
3177 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
3178 RB_PAGE_HEAD);
3179
3180 /*
3181 * type can be one of four:
3182 * NORMAL - an interrupt already moved it for us
3183 * HEAD - we are the first to get here.
3184 * UPDATE - we are the interrupt interrupting
3185 * a current move.
3186 * MOVED - a reader on another CPU moved the next
3187 * pointer to its reader page. Give up
3188 * and try again.
3189 */
3190
3191 switch (type) {
3192 case RB_PAGE_HEAD:
3193 /*
3194 * We changed the head to UPDATE, thus
3195 * it is our responsibility to update
3196 * the counters.
3197 */
3198 local_add(entries, &cpu_buffer->overrun);
3199 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
3200 local_inc(&cpu_buffer->pages_lost);
3201
3202 if (cpu_buffer->ring_meta)
3203 rb_update_meta_head(cpu_buffer, next_page);
3204 /*
3205 * The entries will be zeroed out when we move the
3206 * tail page.
3207 */
3208
3209 /* still more to do */
3210 break;
3211
3212 case RB_PAGE_UPDATE:
3213 /*
3214 * This is an interrupt that interrupt the
3215 * previous update. Still more to do.
3216 */
3217 break;
3218 case RB_PAGE_NORMAL:
3219 /*
3220 * An interrupt came in before the update
3221 * and processed this for us.
3222 * Nothing left to do.
3223 */
3224 return 1;
3225 case RB_PAGE_MOVED:
3226 /*
3227 * The reader is on another CPU and just did
3228 * a swap with our next_page.
3229 * Try again.
3230 */
3231 return 1;
3232 default:
3233 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
3234 return -1;
3235 }
3236
3237 /*
3238 * Now that we are here, the old head pointer is
3239 * set to UPDATE. This will keep the reader from
3240 * swapping the head page with the reader page.
3241 * The reader (on another CPU) will spin till
3242 * we are finished.
3243 *
3244 * We just need to protect against interrupts
3245 * doing the job. We will set the next pointer
3246 * to HEAD. After that, we set the old pointer
3247 * to NORMAL, but only if it was HEAD before.
3248 * otherwise we are an interrupt, and only
3249 * want the outer most commit to reset it.
3250 */
3251 new_head = next_page;
3252 rb_inc_page(&new_head);
3253
3254 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
3255 RB_PAGE_NORMAL);
3256
3257 /*
3258 * Valid returns are:
3259 * HEAD - an interrupt came in and already set it.
3260 * NORMAL - One of two things:
3261 * 1) We really set it.
3262 * 2) A bunch of interrupts came in and moved
3263 * the page forward again.
3264 */
3265 switch (ret) {
3266 case RB_PAGE_HEAD:
3267 case RB_PAGE_NORMAL:
3268 /* OK */
3269 break;
3270 default:
3271 RB_WARN_ON(cpu_buffer, 1);
3272 return -1;
3273 }
3274
3275 /*
3276 * It is possible that an interrupt came in,
3277 * set the head up, then more interrupts came in
3278 * and moved it again. When we get back here,
3279 * the page would have been set to NORMAL but we
3280 * just set it back to HEAD.
3281 *
3282 * How do you detect this? Well, if that happened
3283 * the tail page would have moved.
3284 */
3285 if (ret == RB_PAGE_NORMAL) {
3286 struct buffer_page *buffer_tail_page;
3287
3288 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
3289 /*
3290 * If the tail had moved passed next, then we need
3291 * to reset the pointer.
3292 */
3293 if (buffer_tail_page != tail_page &&
3294 buffer_tail_page != next_page)
3295 rb_head_page_set_normal(cpu_buffer, new_head,
3296 next_page,
3297 RB_PAGE_HEAD);
3298 }
3299
3300 /*
3301 * If this was the outer most commit (the one that
3302 * changed the original pointer from HEAD to UPDATE),
3303 * then it is up to us to reset it to NORMAL.
3304 */
3305 if (type == RB_PAGE_HEAD) {
3306 ret = rb_head_page_set_normal(cpu_buffer, next_page,
3307 tail_page,
3308 RB_PAGE_UPDATE);
3309 if (RB_WARN_ON(cpu_buffer,
3310 ret != RB_PAGE_UPDATE))
3311 return -1;
3312 }
3313
3314 return 0;
3315}
3316
3317static inline void
3318rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
3319 unsigned long tail, struct rb_event_info *info)
3320{
3321 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
3322 struct buffer_page *tail_page = info->tail_page;
3323 struct ring_buffer_event *event;
3324 unsigned long length = info->length;
3325
3326 /*
3327 * Only the event that crossed the page boundary
3328 * must fill the old tail_page with padding.
3329 */
3330 if (tail >= bsize) {
3331 /*
3332 * If the page was filled, then we still need
3333 * to update the real_end. Reset it to zero
3334 * and the reader will ignore it.
3335 */
3336 if (tail == bsize)
3337 tail_page->real_end = 0;
3338
3339 local_sub(length, &tail_page->write);
3340 return;
3341 }
3342
3343 event = __rb_page_index(tail_page, tail);
3344
3345 /*
3346 * Save the original length to the meta data.
3347 * This will be used by the reader to add lost event
3348 * counter.
3349 */
3350 tail_page->real_end = tail;
3351
3352 /*
3353 * If this event is bigger than the minimum size, then
3354 * we need to be careful that we don't subtract the
3355 * write counter enough to allow another writer to slip
3356 * in on this page.
3357 * We put in a discarded commit instead, to make sure
3358 * that this space is not used again, and this space will
3359 * not be accounted into 'entries_bytes'.
3360 *
3361 * If we are less than the minimum size, we don't need to
3362 * worry about it.
3363 */
3364 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
3365 /* No room for any events */
3366
3367 /* Mark the rest of the page with padding */
3368 rb_event_set_padding(event);
3369
3370 /* Make sure the padding is visible before the write update */
3371 smp_wmb();
3372
3373 /* Set the write back to the previous setting */
3374 local_sub(length, &tail_page->write);
3375 return;
3376 }
3377
3378 /* Put in a discarded event */
3379 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
3380 event->type_len = RINGBUF_TYPE_PADDING;
3381 /* time delta must be non zero */
3382 event->time_delta = 1;
3383
3384 /* account for padding bytes */
3385 local_add(bsize - tail, &cpu_buffer->entries_bytes);
3386
3387 /* Make sure the padding is visible before the tail_page->write update */
3388 smp_wmb();
3389
3390 /* Set write to end of buffer */
3391 length = (tail + length) - bsize;
3392 local_sub(length, &tail_page->write);
3393}
3394
3395static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
3396
3397/*
3398 * This is the slow path, force gcc not to inline it.
3399 */
3400static noinline struct ring_buffer_event *
3401rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
3402 unsigned long tail, struct rb_event_info *info)
3403{
3404 struct buffer_page *tail_page = info->tail_page;
3405 struct buffer_page *commit_page = cpu_buffer->commit_page;
3406 struct trace_buffer *buffer = cpu_buffer->buffer;
3407 struct buffer_page *next_page;
3408 int ret;
3409
3410 next_page = tail_page;
3411
3412 rb_inc_page(&next_page);
3413
3414 /*
3415 * If for some reason, we had an interrupt storm that made
3416 * it all the way around the buffer, bail, and warn
3417 * about it.
3418 */
3419 if (unlikely(next_page == commit_page)) {
3420 local_inc(&cpu_buffer->commit_overrun);
3421 goto out_reset;
3422 }
3423
3424 /*
3425 * This is where the fun begins!
3426 *
3427 * We are fighting against races between a reader that
3428 * could be on another CPU trying to swap its reader
3429 * page with the buffer head.
3430 *
3431 * We are also fighting against interrupts coming in and
3432 * moving the head or tail on us as well.
3433 *
3434 * If the next page is the head page then we have filled
3435 * the buffer, unless the commit page is still on the
3436 * reader page.
3437 */
3438 if (rb_is_head_page(next_page, &tail_page->list)) {
3439
3440 /*
3441 * If the commit is not on the reader page, then
3442 * move the header page.
3443 */
3444 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
3445 /*
3446 * If we are not in overwrite mode,
3447 * this is easy, just stop here.
3448 */
3449 if (!(buffer->flags & RB_FL_OVERWRITE)) {
3450 local_inc(&cpu_buffer->dropped_events);
3451 goto out_reset;
3452 }
3453
3454 ret = rb_handle_head_page(cpu_buffer,
3455 tail_page,
3456 next_page);
3457 if (ret < 0)
3458 goto out_reset;
3459 if (ret)
3460 goto out_again;
3461 } else {
3462 /*
3463 * We need to be careful here too. The
3464 * commit page could still be on the reader
3465 * page. We could have a small buffer, and
3466 * have filled up the buffer with events
3467 * from interrupts and such, and wrapped.
3468 *
3469 * Note, if the tail page is also on the
3470 * reader_page, we let it move out.
3471 */
3472 if (unlikely((cpu_buffer->commit_page !=
3473 cpu_buffer->tail_page) &&
3474 (cpu_buffer->commit_page ==
3475 cpu_buffer->reader_page))) {
3476 local_inc(&cpu_buffer->commit_overrun);
3477 goto out_reset;
3478 }
3479 }
3480 }
3481
3482 rb_tail_page_update(cpu_buffer, tail_page, next_page);
3483
3484 out_again:
3485
3486 rb_reset_tail(cpu_buffer, tail, info);
3487
3488 /* Commit what we have for now. */
3489 rb_end_commit(cpu_buffer);
3490 /* rb_end_commit() decs committing */
3491 local_inc(&cpu_buffer->committing);
3492
3493 /* fail and let the caller try again */
3494 return ERR_PTR(-EAGAIN);
3495
3496 out_reset:
3497 /* reset write */
3498 rb_reset_tail(cpu_buffer, tail, info);
3499
3500 return NULL;
3501}
3502
3503/* Slow path */
3504static struct ring_buffer_event *
3505rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3506 struct ring_buffer_event *event, u64 delta, bool abs)
3507{
3508 if (abs)
3509 event->type_len = RINGBUF_TYPE_TIME_STAMP;
3510 else
3511 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
3512
3513 /* Not the first event on the page, or not delta? */
3514 if (abs || rb_event_index(cpu_buffer, event)) {
3515 event->time_delta = delta & TS_MASK;
3516 event->array[0] = delta >> TS_SHIFT;
3517 } else {
3518 /* nope, just zero it */
3519 event->time_delta = 0;
3520 event->array[0] = 0;
3521 }
3522
3523 return skip_time_extend(event);
3524}
3525
3526#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
3527static inline bool sched_clock_stable(void)
3528{
3529 return true;
3530}
3531#endif
3532
3533static void
3534rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3535 struct rb_event_info *info)
3536{
3537 u64 write_stamp;
3538
3539 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
3540 (unsigned long long)info->delta,
3541 (unsigned long long)info->ts,
3542 (unsigned long long)info->before,
3543 (unsigned long long)info->after,
3544 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
3545 sched_clock_stable() ? "" :
3546 "If you just came from a suspend/resume,\n"
3547 "please switch to the trace global clock:\n"
3548 " echo global > /sys/kernel/tracing/trace_clock\n"
3549 "or add trace_clock=global to the kernel command line\n");
3550}
3551
3552static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3553 struct ring_buffer_event **event,
3554 struct rb_event_info *info,
3555 u64 *delta,
3556 unsigned int *length)
3557{
3558 bool abs = info->add_timestamp &
3559 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
3560
3561 if (unlikely(info->delta > (1ULL << 59))) {
3562 /*
3563 * Some timers can use more than 59 bits, and when a timestamp
3564 * is added to the buffer, it will lose those bits.
3565 */
3566 if (abs && (info->ts & TS_MSB)) {
3567 info->delta &= ABS_TS_MASK;
3568
3569 /* did the clock go backwards */
3570 } else if (info->before == info->after && info->before > info->ts) {
3571 /* not interrupted */
3572 static int once;
3573
3574 /*
3575 * This is possible with a recalibrating of the TSC.
3576 * Do not produce a call stack, but just report it.
3577 */
3578 if (!once) {
3579 once++;
3580 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
3581 info->before, info->ts);
3582 }
3583 } else
3584 rb_check_timestamp(cpu_buffer, info);
3585 if (!abs)
3586 info->delta = 0;
3587 }
3588 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
3589 *length -= RB_LEN_TIME_EXTEND;
3590 *delta = 0;
3591}
3592
3593/**
3594 * rb_update_event - update event type and data
3595 * @cpu_buffer: The per cpu buffer of the @event
3596 * @event: the event to update
3597 * @info: The info to update the @event with (contains length and delta)
3598 *
3599 * Update the type and data fields of the @event. The length
3600 * is the actual size that is written to the ring buffer,
3601 * and with this, we can determine what to place into the
3602 * data field.
3603 */
3604static void
3605rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
3606 struct ring_buffer_event *event,
3607 struct rb_event_info *info)
3608{
3609 unsigned length = info->length;
3610 u64 delta = info->delta;
3611 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
3612
3613 if (!WARN_ON_ONCE(nest >= MAX_NEST))
3614 cpu_buffer->event_stamp[nest] = info->ts;
3615
3616 /*
3617 * If we need to add a timestamp, then we
3618 * add it to the start of the reserved space.
3619 */
3620 if (unlikely(info->add_timestamp))
3621 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
3622
3623 event->time_delta = delta;
3624 length -= RB_EVNT_HDR_SIZE;
3625 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
3626 event->type_len = 0;
3627 event->array[0] = length;
3628 } else
3629 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
3630}
3631
3632static unsigned rb_calculate_event_length(unsigned length)
3633{
3634 struct ring_buffer_event event; /* Used only for sizeof array */
3635
3636 /* zero length can cause confusions */
3637 if (!length)
3638 length++;
3639
3640 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
3641 length += sizeof(event.array[0]);
3642
3643 length += RB_EVNT_HDR_SIZE;
3644 length = ALIGN(length, RB_ARCH_ALIGNMENT);
3645
3646 /*
3647 * In case the time delta is larger than the 27 bits for it
3648 * in the header, we need to add a timestamp. If another
3649 * event comes in when trying to discard this one to increase
3650 * the length, then the timestamp will be added in the allocated
3651 * space of this event. If length is bigger than the size needed
3652 * for the TIME_EXTEND, then padding has to be used. The events
3653 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
3654 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
3655 * As length is a multiple of 4, we only need to worry if it
3656 * is 12 (RB_LEN_TIME_EXTEND + 4).
3657 */
3658 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
3659 length += RB_ALIGNMENT;
3660
3661 return length;
3662}
3663
3664static inline bool
3665rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
3666 struct ring_buffer_event *event)
3667{
3668 unsigned long new_index, old_index;
3669 struct buffer_page *bpage;
3670 unsigned long addr;
3671
3672 new_index = rb_event_index(cpu_buffer, event);
3673 old_index = new_index + rb_event_ts_length(event);
3674 addr = (unsigned long)event;
3675 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3676
3677 bpage = READ_ONCE(cpu_buffer->tail_page);
3678
3679 /*
3680 * Make sure the tail_page is still the same and
3681 * the next write location is the end of this event
3682 */
3683 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
3684 unsigned long write_mask =
3685 local_read(&bpage->write) & ~RB_WRITE_MASK;
3686 unsigned long event_length = rb_event_length(event);
3687
3688 /*
3689 * For the before_stamp to be different than the write_stamp
3690 * to make sure that the next event adds an absolute
3691 * value and does not rely on the saved write stamp, which
3692 * is now going to be bogus.
3693 *
3694 * By setting the before_stamp to zero, the next event
3695 * is not going to use the write_stamp and will instead
3696 * create an absolute timestamp. This means there's no
3697 * reason to update the wirte_stamp!
3698 */
3699 rb_time_set(&cpu_buffer->before_stamp, 0);
3700
3701 /*
3702 * If an event were to come in now, it would see that the
3703 * write_stamp and the before_stamp are different, and assume
3704 * that this event just added itself before updating
3705 * the write stamp. The interrupting event will fix the
3706 * write stamp for us, and use an absolute timestamp.
3707 */
3708
3709 /*
3710 * This is on the tail page. It is possible that
3711 * a write could come in and move the tail page
3712 * and write to the next page. That is fine
3713 * because we just shorten what is on this page.
3714 */
3715 old_index += write_mask;
3716 new_index += write_mask;
3717
3718 /* caution: old_index gets updated on cmpxchg failure */
3719 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
3720 /* update counters */
3721 local_sub(event_length, &cpu_buffer->entries_bytes);
3722 return true;
3723 }
3724 }
3725
3726 /* could not discard */
3727 return false;
3728}
3729
3730static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
3731{
3732 local_inc(&cpu_buffer->committing);
3733 local_inc(&cpu_buffer->commits);
3734}
3735
3736static __always_inline void
3737rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
3738{
3739 unsigned long max_count;
3740
3741 /*
3742 * We only race with interrupts and NMIs on this CPU.
3743 * If we own the commit event, then we can commit
3744 * all others that interrupted us, since the interruptions
3745 * are in stack format (they finish before they come
3746 * back to us). This allows us to do a simple loop to
3747 * assign the commit to the tail.
3748 */
3749 again:
3750 max_count = cpu_buffer->nr_pages * 100;
3751
3752 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
3753 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
3754 return;
3755 if (RB_WARN_ON(cpu_buffer,
3756 rb_is_reader_page(cpu_buffer->tail_page)))
3757 return;
3758 /*
3759 * No need for a memory barrier here, as the update
3760 * of the tail_page did it for this page.
3761 */
3762 local_set(&cpu_buffer->commit_page->page->commit,
3763 rb_page_write(cpu_buffer->commit_page));
3764 rb_inc_page(&cpu_buffer->commit_page);
3765 if (cpu_buffer->ring_meta) {
3766 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3767 meta->commit_buffer = (unsigned long)cpu_buffer->commit_page->page;
3768 }
3769 /* add barrier to keep gcc from optimizing too much */
3770 barrier();
3771 }
3772 while (rb_commit_index(cpu_buffer) !=
3773 rb_page_write(cpu_buffer->commit_page)) {
3774
3775 /* Make sure the readers see the content of what is committed. */
3776 smp_wmb();
3777 local_set(&cpu_buffer->commit_page->page->commit,
3778 rb_page_write(cpu_buffer->commit_page));
3779 RB_WARN_ON(cpu_buffer,
3780 local_read(&cpu_buffer->commit_page->page->commit) &
3781 ~RB_WRITE_MASK);
3782 barrier();
3783 }
3784
3785 /* again, keep gcc from optimizing */
3786 barrier();
3787
3788 /*
3789 * If an interrupt came in just after the first while loop
3790 * and pushed the tail page forward, we will be left with
3791 * a dangling commit that will never go forward.
3792 */
3793 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3794 goto again;
3795}
3796
3797static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3798{
3799 unsigned long commits;
3800
3801 if (RB_WARN_ON(cpu_buffer,
3802 !local_read(&cpu_buffer->committing)))
3803 return;
3804
3805 again:
3806 commits = local_read(&cpu_buffer->commits);
3807 /* synchronize with interrupts */
3808 barrier();
3809 if (local_read(&cpu_buffer->committing) == 1)
3810 rb_set_commit_to_write(cpu_buffer);
3811
3812 local_dec(&cpu_buffer->committing);
3813
3814 /* synchronize with interrupts */
3815 barrier();
3816
3817 /*
3818 * Need to account for interrupts coming in between the
3819 * updating of the commit page and the clearing of the
3820 * committing counter.
3821 */
3822 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3823 !local_read(&cpu_buffer->committing)) {
3824 local_inc(&cpu_buffer->committing);
3825 goto again;
3826 }
3827}
3828
3829static inline void rb_event_discard(struct ring_buffer_event *event)
3830{
3831 if (extended_time(event))
3832 event = skip_time_extend(event);
3833
3834 /* array[0] holds the actual length for the discarded event */
3835 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3836 event->type_len = RINGBUF_TYPE_PADDING;
3837 /* time delta must be non zero */
3838 if (!event->time_delta)
3839 event->time_delta = 1;
3840}
3841
3842static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3843{
3844 local_inc(&cpu_buffer->entries);
3845 rb_end_commit(cpu_buffer);
3846}
3847
3848static __always_inline void
3849rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3850{
3851 if (buffer->irq_work.waiters_pending) {
3852 buffer->irq_work.waiters_pending = false;
3853 /* irq_work_queue() supplies it's own memory barriers */
3854 irq_work_queue(&buffer->irq_work.work);
3855 }
3856
3857 if (cpu_buffer->irq_work.waiters_pending) {
3858 cpu_buffer->irq_work.waiters_pending = false;
3859 /* irq_work_queue() supplies it's own memory barriers */
3860 irq_work_queue(&cpu_buffer->irq_work.work);
3861 }
3862
3863 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3864 return;
3865
3866 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3867 return;
3868
3869 if (!cpu_buffer->irq_work.full_waiters_pending)
3870 return;
3871
3872 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3873
3874 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3875 return;
3876
3877 cpu_buffer->irq_work.wakeup_full = true;
3878 cpu_buffer->irq_work.full_waiters_pending = false;
3879 /* irq_work_queue() supplies it's own memory barriers */
3880 irq_work_queue(&cpu_buffer->irq_work.work);
3881}
3882
3883#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3884# define do_ring_buffer_record_recursion() \
3885 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3886#else
3887# define do_ring_buffer_record_recursion() do { } while (0)
3888#endif
3889
3890/*
3891 * The lock and unlock are done within a preempt disable section.
3892 * The current_context per_cpu variable can only be modified
3893 * by the current task between lock and unlock. But it can
3894 * be modified more than once via an interrupt. To pass this
3895 * information from the lock to the unlock without having to
3896 * access the 'in_interrupt()' functions again (which do show
3897 * a bit of overhead in something as critical as function tracing,
3898 * we use a bitmask trick.
3899 *
3900 * bit 1 = NMI context
3901 * bit 2 = IRQ context
3902 * bit 3 = SoftIRQ context
3903 * bit 4 = normal context.
3904 *
3905 * This works because this is the order of contexts that can
3906 * preempt other contexts. A SoftIRQ never preempts an IRQ
3907 * context.
3908 *
3909 * When the context is determined, the corresponding bit is
3910 * checked and set (if it was set, then a recursion of that context
3911 * happened).
3912 *
3913 * On unlock, we need to clear this bit. To do so, just subtract
3914 * 1 from the current_context and AND it to itself.
3915 *
3916 * (binary)
3917 * 101 - 1 = 100
3918 * 101 & 100 = 100 (clearing bit zero)
3919 *
3920 * 1010 - 1 = 1001
3921 * 1010 & 1001 = 1000 (clearing bit 1)
3922 *
3923 * The least significant bit can be cleared this way, and it
3924 * just so happens that it is the same bit corresponding to
3925 * the current context.
3926 *
3927 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3928 * is set when a recursion is detected at the current context, and if
3929 * the TRANSITION bit is already set, it will fail the recursion.
3930 * This is needed because there's a lag between the changing of
3931 * interrupt context and updating the preempt count. In this case,
3932 * a false positive will be found. To handle this, one extra recursion
3933 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3934 * bit is already set, then it is considered a recursion and the function
3935 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3936 *
3937 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3938 * to be cleared. Even if it wasn't the context that set it. That is,
3939 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3940 * is called before preempt_count() is updated, since the check will
3941 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3942 * NMI then comes in, it will set the NMI bit, but when the NMI code
3943 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3944 * and leave the NMI bit set. But this is fine, because the interrupt
3945 * code that set the TRANSITION bit will then clear the NMI bit when it
3946 * calls trace_recursive_unlock(). If another NMI comes in, it will
3947 * set the TRANSITION bit and continue.
3948 *
3949 * Note: The TRANSITION bit only handles a single transition between context.
3950 */
3951
3952static __always_inline bool
3953trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3954{
3955 unsigned int val = cpu_buffer->current_context;
3956 int bit = interrupt_context_level();
3957
3958 bit = RB_CTX_NORMAL - bit;
3959
3960 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3961 /*
3962 * It is possible that this was called by transitioning
3963 * between interrupt context, and preempt_count() has not
3964 * been updated yet. In this case, use the TRANSITION bit.
3965 */
3966 bit = RB_CTX_TRANSITION;
3967 if (val & (1 << (bit + cpu_buffer->nest))) {
3968 do_ring_buffer_record_recursion();
3969 return true;
3970 }
3971 }
3972
3973 val |= (1 << (bit + cpu_buffer->nest));
3974 cpu_buffer->current_context = val;
3975
3976 return false;
3977}
3978
3979static __always_inline void
3980trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3981{
3982 cpu_buffer->current_context &=
3983 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3984}
3985
3986/* The recursive locking above uses 5 bits */
3987#define NESTED_BITS 5
3988
3989/**
3990 * ring_buffer_nest_start - Allow to trace while nested
3991 * @buffer: The ring buffer to modify
3992 *
3993 * The ring buffer has a safety mechanism to prevent recursion.
3994 * But there may be a case where a trace needs to be done while
3995 * tracing something else. In this case, calling this function
3996 * will allow this function to nest within a currently active
3997 * ring_buffer_lock_reserve().
3998 *
3999 * Call this function before calling another ring_buffer_lock_reserve() and
4000 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
4001 */
4002void ring_buffer_nest_start(struct trace_buffer *buffer)
4003{
4004 struct ring_buffer_per_cpu *cpu_buffer;
4005 int cpu;
4006
4007 /* Enabled by ring_buffer_nest_end() */
4008 preempt_disable_notrace();
4009 cpu = raw_smp_processor_id();
4010 cpu_buffer = buffer->buffers[cpu];
4011 /* This is the shift value for the above recursive locking */
4012 cpu_buffer->nest += NESTED_BITS;
4013}
4014
4015/**
4016 * ring_buffer_nest_end - Allow to trace while nested
4017 * @buffer: The ring buffer to modify
4018 *
4019 * Must be called after ring_buffer_nest_start() and after the
4020 * ring_buffer_unlock_commit().
4021 */
4022void ring_buffer_nest_end(struct trace_buffer *buffer)
4023{
4024 struct ring_buffer_per_cpu *cpu_buffer;
4025 int cpu;
4026
4027 /* disabled by ring_buffer_nest_start() */
4028 cpu = raw_smp_processor_id();
4029 cpu_buffer = buffer->buffers[cpu];
4030 /* This is the shift value for the above recursive locking */
4031 cpu_buffer->nest -= NESTED_BITS;
4032 preempt_enable_notrace();
4033}
4034
4035/**
4036 * ring_buffer_unlock_commit - commit a reserved
4037 * @buffer: The buffer to commit to
4038 *
4039 * This commits the data to the ring buffer, and releases any locks held.
4040 *
4041 * Must be paired with ring_buffer_lock_reserve.
4042 */
4043int ring_buffer_unlock_commit(struct trace_buffer *buffer)
4044{
4045 struct ring_buffer_per_cpu *cpu_buffer;
4046 int cpu = raw_smp_processor_id();
4047
4048 cpu_buffer = buffer->buffers[cpu];
4049
4050 rb_commit(cpu_buffer);
4051
4052 rb_wakeups(buffer, cpu_buffer);
4053
4054 trace_recursive_unlock(cpu_buffer);
4055
4056 preempt_enable_notrace();
4057
4058 return 0;
4059}
4060EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
4061
4062/* Special value to validate all deltas on a page. */
4063#define CHECK_FULL_PAGE 1L
4064
4065#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
4066
4067static const char *show_irq_str(int bits)
4068{
4069 const char *type[] = {
4070 ".", // 0
4071 "s", // 1
4072 "h", // 2
4073 "Hs", // 3
4074 "n", // 4
4075 "Ns", // 5
4076 "Nh", // 6
4077 "NHs", // 7
4078 };
4079
4080 return type[bits];
4081}
4082
4083/* Assume this is a trace event */
4084static const char *show_flags(struct ring_buffer_event *event)
4085{
4086 struct trace_entry *entry;
4087 int bits = 0;
4088
4089 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4090 return "X";
4091
4092 entry = ring_buffer_event_data(event);
4093
4094 if (entry->flags & TRACE_FLAG_SOFTIRQ)
4095 bits |= 1;
4096
4097 if (entry->flags & TRACE_FLAG_HARDIRQ)
4098 bits |= 2;
4099
4100 if (entry->flags & TRACE_FLAG_NMI)
4101 bits |= 4;
4102
4103 return show_irq_str(bits);
4104}
4105
4106static const char *show_irq(struct ring_buffer_event *event)
4107{
4108 struct trace_entry *entry;
4109
4110 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4111 return "";
4112
4113 entry = ring_buffer_event_data(event);
4114 if (entry->flags & TRACE_FLAG_IRQS_OFF)
4115 return "d";
4116 return "";
4117}
4118
4119static const char *show_interrupt_level(void)
4120{
4121 unsigned long pc = preempt_count();
4122 unsigned char level = 0;
4123
4124 if (pc & SOFTIRQ_OFFSET)
4125 level |= 1;
4126
4127 if (pc & HARDIRQ_MASK)
4128 level |= 2;
4129
4130 if (pc & NMI_MASK)
4131 level |= 4;
4132
4133 return show_irq_str(level);
4134}
4135
4136static void dump_buffer_page(struct buffer_data_page *bpage,
4137 struct rb_event_info *info,
4138 unsigned long tail)
4139{
4140 struct ring_buffer_event *event;
4141 u64 ts, delta;
4142 int e;
4143
4144 ts = bpage->time_stamp;
4145 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
4146
4147 for (e = 0; e < tail; e += rb_event_length(event)) {
4148
4149 event = (struct ring_buffer_event *)(bpage->data + e);
4150
4151 switch (event->type_len) {
4152
4153 case RINGBUF_TYPE_TIME_EXTEND:
4154 delta = rb_event_time_stamp(event);
4155 ts += delta;
4156 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
4157 e, ts, delta);
4158 break;
4159
4160 case RINGBUF_TYPE_TIME_STAMP:
4161 delta = rb_event_time_stamp(event);
4162 ts = rb_fix_abs_ts(delta, ts);
4163 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
4164 e, ts, delta);
4165 break;
4166
4167 case RINGBUF_TYPE_PADDING:
4168 ts += event->time_delta;
4169 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
4170 e, ts, event->time_delta);
4171 break;
4172
4173 case RINGBUF_TYPE_DATA:
4174 ts += event->time_delta;
4175 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
4176 e, ts, event->time_delta,
4177 show_flags(event), show_irq(event));
4178 break;
4179
4180 default:
4181 break;
4182 }
4183 }
4184 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
4185}
4186
4187static DEFINE_PER_CPU(atomic_t, checking);
4188static atomic_t ts_dump;
4189
4190#define buffer_warn_return(fmt, ...) \
4191 do { \
4192 /* If another report is happening, ignore this one */ \
4193 if (atomic_inc_return(&ts_dump) != 1) { \
4194 atomic_dec(&ts_dump); \
4195 goto out; \
4196 } \
4197 atomic_inc(&cpu_buffer->record_disabled); \
4198 pr_warn(fmt, ##__VA_ARGS__); \
4199 dump_buffer_page(bpage, info, tail); \
4200 atomic_dec(&ts_dump); \
4201 /* There's some cases in boot up that this can happen */ \
4202 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
4203 /* Do not re-enable checking */ \
4204 return; \
4205 } while (0)
4206
4207/*
4208 * Check if the current event time stamp matches the deltas on
4209 * the buffer page.
4210 */
4211static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4212 struct rb_event_info *info,
4213 unsigned long tail)
4214{
4215 struct buffer_data_page *bpage;
4216 u64 ts, delta;
4217 bool full = false;
4218 int ret;
4219
4220 bpage = info->tail_page->page;
4221
4222 if (tail == CHECK_FULL_PAGE) {
4223 full = true;
4224 tail = local_read(&bpage->commit);
4225 } else if (info->add_timestamp &
4226 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
4227 /* Ignore events with absolute time stamps */
4228 return;
4229 }
4230
4231 /*
4232 * Do not check the first event (skip possible extends too).
4233 * Also do not check if previous events have not been committed.
4234 */
4235 if (tail <= 8 || tail > local_read(&bpage->commit))
4236 return;
4237
4238 /*
4239 * If this interrupted another event,
4240 */
4241 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
4242 goto out;
4243
4244 ret = rb_read_data_buffer(bpage, tail, cpu_buffer->cpu, &ts, &delta);
4245 if (ret < 0) {
4246 if (delta < ts) {
4247 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
4248 cpu_buffer->cpu, ts, delta);
4249 goto out;
4250 }
4251 }
4252 if ((full && ts > info->ts) ||
4253 (!full && ts + info->delta != info->ts)) {
4254 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
4255 cpu_buffer->cpu,
4256 ts + info->delta, info->ts, info->delta,
4257 info->before, info->after,
4258 full ? " (full)" : "", show_interrupt_level());
4259 }
4260out:
4261 atomic_dec(this_cpu_ptr(&checking));
4262}
4263#else
4264static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4265 struct rb_event_info *info,
4266 unsigned long tail)
4267{
4268}
4269#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
4270
4271static struct ring_buffer_event *
4272__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
4273 struct rb_event_info *info)
4274{
4275 struct ring_buffer_event *event;
4276 struct buffer_page *tail_page;
4277 unsigned long tail, write, w;
4278
4279 /* Don't let the compiler play games with cpu_buffer->tail_page */
4280 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
4281
4282 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
4283 barrier();
4284 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4285 rb_time_read(&cpu_buffer->write_stamp, &info->after);
4286 barrier();
4287 info->ts = rb_time_stamp(cpu_buffer->buffer);
4288
4289 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
4290 info->delta = info->ts;
4291 } else {
4292 /*
4293 * If interrupting an event time update, we may need an
4294 * absolute timestamp.
4295 * Don't bother if this is the start of a new page (w == 0).
4296 */
4297 if (!w) {
4298 /* Use the sub-buffer timestamp */
4299 info->delta = 0;
4300 } else if (unlikely(info->before != info->after)) {
4301 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
4302 info->length += RB_LEN_TIME_EXTEND;
4303 } else {
4304 info->delta = info->ts - info->after;
4305 if (unlikely(test_time_stamp(info->delta))) {
4306 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
4307 info->length += RB_LEN_TIME_EXTEND;
4308 }
4309 }
4310 }
4311
4312 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
4313
4314 /*C*/ write = local_add_return(info->length, &tail_page->write);
4315
4316 /* set write to only the index of the write */
4317 write &= RB_WRITE_MASK;
4318
4319 tail = write - info->length;
4320
4321 /* See if we shot pass the end of this buffer page */
4322 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
4323 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
4324 return rb_move_tail(cpu_buffer, tail, info);
4325 }
4326
4327 if (likely(tail == w)) {
4328 /* Nothing interrupted us between A and C */
4329 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
4330 /*
4331 * If something came in between C and D, the write stamp
4332 * may now not be in sync. But that's fine as the before_stamp
4333 * will be different and then next event will just be forced
4334 * to use an absolute timestamp.
4335 */
4336 if (likely(!(info->add_timestamp &
4337 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4338 /* This did not interrupt any time update */
4339 info->delta = info->ts - info->after;
4340 else
4341 /* Just use full timestamp for interrupting event */
4342 info->delta = info->ts;
4343 check_buffer(cpu_buffer, info, tail);
4344 } else {
4345 u64 ts;
4346 /* SLOW PATH - Interrupted between A and C */
4347
4348 /* Save the old before_stamp */
4349 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4350
4351 /*
4352 * Read a new timestamp and update the before_stamp to make
4353 * the next event after this one force using an absolute
4354 * timestamp. This is in case an interrupt were to come in
4355 * between E and F.
4356 */
4357 ts = rb_time_stamp(cpu_buffer->buffer);
4358 rb_time_set(&cpu_buffer->before_stamp, ts);
4359
4360 barrier();
4361 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
4362 barrier();
4363 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
4364 info->after == info->before && info->after < ts) {
4365 /*
4366 * Nothing came after this event between C and F, it is
4367 * safe to use info->after for the delta as it
4368 * matched info->before and is still valid.
4369 */
4370 info->delta = ts - info->after;
4371 } else {
4372 /*
4373 * Interrupted between C and F:
4374 * Lost the previous events time stamp. Just set the
4375 * delta to zero, and this will be the same time as
4376 * the event this event interrupted. And the events that
4377 * came after this will still be correct (as they would
4378 * have built their delta on the previous event.
4379 */
4380 info->delta = 0;
4381 }
4382 info->ts = ts;
4383 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
4384 }
4385
4386 /*
4387 * If this is the first commit on the page, then it has the same
4388 * timestamp as the page itself.
4389 */
4390 if (unlikely(!tail && !(info->add_timestamp &
4391 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4392 info->delta = 0;
4393
4394 /* We reserved something on the buffer */
4395
4396 event = __rb_page_index(tail_page, tail);
4397 rb_update_event(cpu_buffer, event, info);
4398
4399 local_inc(&tail_page->entries);
4400
4401 /*
4402 * If this is the first commit on the page, then update
4403 * its timestamp.
4404 */
4405 if (unlikely(!tail))
4406 tail_page->page->time_stamp = info->ts;
4407
4408 /* account for these added bytes */
4409 local_add(info->length, &cpu_buffer->entries_bytes);
4410
4411 return event;
4412}
4413
4414static __always_inline struct ring_buffer_event *
4415rb_reserve_next_event(struct trace_buffer *buffer,
4416 struct ring_buffer_per_cpu *cpu_buffer,
4417 unsigned long length)
4418{
4419 struct ring_buffer_event *event;
4420 struct rb_event_info info;
4421 int nr_loops = 0;
4422 int add_ts_default;
4423
4424 /*
4425 * ring buffer does cmpxchg as well as atomic64 operations
4426 * (which some archs use locking for atomic64), make sure this
4427 * is safe in NMI context
4428 */
4429 if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) ||
4430 IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) &&
4431 (unlikely(in_nmi()))) {
4432 return NULL;
4433 }
4434
4435 rb_start_commit(cpu_buffer);
4436 /* The commit page can not change after this */
4437
4438#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4439 /*
4440 * Due to the ability to swap a cpu buffer from a buffer
4441 * it is possible it was swapped before we committed.
4442 * (committing stops a swap). We check for it here and
4443 * if it happened, we have to fail the write.
4444 */
4445 barrier();
4446 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
4447 local_dec(&cpu_buffer->committing);
4448 local_dec(&cpu_buffer->commits);
4449 return NULL;
4450 }
4451#endif
4452
4453 info.length = rb_calculate_event_length(length);
4454
4455 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
4456 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
4457 info.length += RB_LEN_TIME_EXTEND;
4458 if (info.length > cpu_buffer->buffer->max_data_size)
4459 goto out_fail;
4460 } else {
4461 add_ts_default = RB_ADD_STAMP_NONE;
4462 }
4463
4464 again:
4465 info.add_timestamp = add_ts_default;
4466 info.delta = 0;
4467
4468 /*
4469 * We allow for interrupts to reenter here and do a trace.
4470 * If one does, it will cause this original code to loop
4471 * back here. Even with heavy interrupts happening, this
4472 * should only happen a few times in a row. If this happens
4473 * 1000 times in a row, there must be either an interrupt
4474 * storm or we have something buggy.
4475 * Bail!
4476 */
4477 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
4478 goto out_fail;
4479
4480 event = __rb_reserve_next(cpu_buffer, &info);
4481
4482 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
4483 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
4484 info.length -= RB_LEN_TIME_EXTEND;
4485 goto again;
4486 }
4487
4488 if (likely(event))
4489 return event;
4490 out_fail:
4491 rb_end_commit(cpu_buffer);
4492 return NULL;
4493}
4494
4495/**
4496 * ring_buffer_lock_reserve - reserve a part of the buffer
4497 * @buffer: the ring buffer to reserve from
4498 * @length: the length of the data to reserve (excluding event header)
4499 *
4500 * Returns a reserved event on the ring buffer to copy directly to.
4501 * The user of this interface will need to get the body to write into
4502 * and can use the ring_buffer_event_data() interface.
4503 *
4504 * The length is the length of the data needed, not the event length
4505 * which also includes the event header.
4506 *
4507 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
4508 * If NULL is returned, then nothing has been allocated or locked.
4509 */
4510struct ring_buffer_event *
4511ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
4512{
4513 struct ring_buffer_per_cpu *cpu_buffer;
4514 struct ring_buffer_event *event;
4515 int cpu;
4516
4517 /* If we are tracing schedule, we don't want to recurse */
4518 preempt_disable_notrace();
4519
4520 if (unlikely(atomic_read(&buffer->record_disabled)))
4521 goto out;
4522
4523 cpu = raw_smp_processor_id();
4524
4525 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
4526 goto out;
4527
4528 cpu_buffer = buffer->buffers[cpu];
4529
4530 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
4531 goto out;
4532
4533 if (unlikely(length > buffer->max_data_size))
4534 goto out;
4535
4536 if (unlikely(trace_recursive_lock(cpu_buffer)))
4537 goto out;
4538
4539 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4540 if (!event)
4541 goto out_unlock;
4542
4543 return event;
4544
4545 out_unlock:
4546 trace_recursive_unlock(cpu_buffer);
4547 out:
4548 preempt_enable_notrace();
4549 return NULL;
4550}
4551EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
4552
4553/*
4554 * Decrement the entries to the page that an event is on.
4555 * The event does not even need to exist, only the pointer
4556 * to the page it is on. This may only be called before the commit
4557 * takes place.
4558 */
4559static inline void
4560rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
4561 struct ring_buffer_event *event)
4562{
4563 unsigned long addr = (unsigned long)event;
4564 struct buffer_page *bpage = cpu_buffer->commit_page;
4565 struct buffer_page *start;
4566
4567 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
4568
4569 /* Do the likely case first */
4570 if (likely(bpage->page == (void *)addr)) {
4571 local_dec(&bpage->entries);
4572 return;
4573 }
4574
4575 /*
4576 * Because the commit page may be on the reader page we
4577 * start with the next page and check the end loop there.
4578 */
4579 rb_inc_page(&bpage);
4580 start = bpage;
4581 do {
4582 if (bpage->page == (void *)addr) {
4583 local_dec(&bpage->entries);
4584 return;
4585 }
4586 rb_inc_page(&bpage);
4587 } while (bpage != start);
4588
4589 /* commit not part of this buffer?? */
4590 RB_WARN_ON(cpu_buffer, 1);
4591}
4592
4593/**
4594 * ring_buffer_discard_commit - discard an event that has not been committed
4595 * @buffer: the ring buffer
4596 * @event: non committed event to discard
4597 *
4598 * Sometimes an event that is in the ring buffer needs to be ignored.
4599 * This function lets the user discard an event in the ring buffer
4600 * and then that event will not be read later.
4601 *
4602 * This function only works if it is called before the item has been
4603 * committed. It will try to free the event from the ring buffer
4604 * if another event has not been added behind it.
4605 *
4606 * If another event has been added behind it, it will set the event
4607 * up as discarded, and perform the commit.
4608 *
4609 * If this function is called, do not call ring_buffer_unlock_commit on
4610 * the event.
4611 */
4612void ring_buffer_discard_commit(struct trace_buffer *buffer,
4613 struct ring_buffer_event *event)
4614{
4615 struct ring_buffer_per_cpu *cpu_buffer;
4616 int cpu;
4617
4618 /* The event is discarded regardless */
4619 rb_event_discard(event);
4620
4621 cpu = smp_processor_id();
4622 cpu_buffer = buffer->buffers[cpu];
4623
4624 /*
4625 * This must only be called if the event has not been
4626 * committed yet. Thus we can assume that preemption
4627 * is still disabled.
4628 */
4629 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
4630
4631 rb_decrement_entry(cpu_buffer, event);
4632 if (rb_try_to_discard(cpu_buffer, event))
4633 goto out;
4634
4635 out:
4636 rb_end_commit(cpu_buffer);
4637
4638 trace_recursive_unlock(cpu_buffer);
4639
4640 preempt_enable_notrace();
4641
4642}
4643EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
4644
4645/**
4646 * ring_buffer_write - write data to the buffer without reserving
4647 * @buffer: The ring buffer to write to.
4648 * @length: The length of the data being written (excluding the event header)
4649 * @data: The data to write to the buffer.
4650 *
4651 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
4652 * one function. If you already have the data to write to the buffer, it
4653 * may be easier to simply call this function.
4654 *
4655 * Note, like ring_buffer_lock_reserve, the length is the length of the data
4656 * and not the length of the event which would hold the header.
4657 */
4658int ring_buffer_write(struct trace_buffer *buffer,
4659 unsigned long length,
4660 void *data)
4661{
4662 struct ring_buffer_per_cpu *cpu_buffer;
4663 struct ring_buffer_event *event;
4664 void *body;
4665 int ret = -EBUSY;
4666 int cpu;
4667
4668 preempt_disable_notrace();
4669
4670 if (atomic_read(&buffer->record_disabled))
4671 goto out;
4672
4673 cpu = raw_smp_processor_id();
4674
4675 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4676 goto out;
4677
4678 cpu_buffer = buffer->buffers[cpu];
4679
4680 if (atomic_read(&cpu_buffer->record_disabled))
4681 goto out;
4682
4683 if (length > buffer->max_data_size)
4684 goto out;
4685
4686 if (unlikely(trace_recursive_lock(cpu_buffer)))
4687 goto out;
4688
4689 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4690 if (!event)
4691 goto out_unlock;
4692
4693 body = rb_event_data(event);
4694
4695 memcpy(body, data, length);
4696
4697 rb_commit(cpu_buffer);
4698
4699 rb_wakeups(buffer, cpu_buffer);
4700
4701 ret = 0;
4702
4703 out_unlock:
4704 trace_recursive_unlock(cpu_buffer);
4705
4706 out:
4707 preempt_enable_notrace();
4708
4709 return ret;
4710}
4711EXPORT_SYMBOL_GPL(ring_buffer_write);
4712
4713static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
4714{
4715 struct buffer_page *reader = cpu_buffer->reader_page;
4716 struct buffer_page *head = rb_set_head_page(cpu_buffer);
4717 struct buffer_page *commit = cpu_buffer->commit_page;
4718
4719 /* In case of error, head will be NULL */
4720 if (unlikely(!head))
4721 return true;
4722
4723 /* Reader should exhaust content in reader page */
4724 if (reader->read != rb_page_size(reader))
4725 return false;
4726
4727 /*
4728 * If writers are committing on the reader page, knowing all
4729 * committed content has been read, the ring buffer is empty.
4730 */
4731 if (commit == reader)
4732 return true;
4733
4734 /*
4735 * If writers are committing on a page other than reader page
4736 * and head page, there should always be content to read.
4737 */
4738 if (commit != head)
4739 return false;
4740
4741 /*
4742 * Writers are committing on the head page, we just need
4743 * to care about there're committed data, and the reader will
4744 * swap reader page with head page when it is to read data.
4745 */
4746 return rb_page_commit(commit) == 0;
4747}
4748
4749/**
4750 * ring_buffer_record_disable - stop all writes into the buffer
4751 * @buffer: The ring buffer to stop writes to.
4752 *
4753 * This prevents all writes to the buffer. Any attempt to write
4754 * to the buffer after this will fail and return NULL.
4755 *
4756 * The caller should call synchronize_rcu() after this.
4757 */
4758void ring_buffer_record_disable(struct trace_buffer *buffer)
4759{
4760 atomic_inc(&buffer->record_disabled);
4761}
4762EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
4763
4764/**
4765 * ring_buffer_record_enable - enable writes to the buffer
4766 * @buffer: The ring buffer to enable writes
4767 *
4768 * Note, multiple disables will need the same number of enables
4769 * to truly enable the writing (much like preempt_disable).
4770 */
4771void ring_buffer_record_enable(struct trace_buffer *buffer)
4772{
4773 atomic_dec(&buffer->record_disabled);
4774}
4775EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4776
4777/**
4778 * ring_buffer_record_off - stop all writes into the buffer
4779 * @buffer: The ring buffer to stop writes to.
4780 *
4781 * This prevents all writes to the buffer. Any attempt to write
4782 * to the buffer after this will fail and return NULL.
4783 *
4784 * This is different than ring_buffer_record_disable() as
4785 * it works like an on/off switch, where as the disable() version
4786 * must be paired with a enable().
4787 */
4788void ring_buffer_record_off(struct trace_buffer *buffer)
4789{
4790 unsigned int rd;
4791 unsigned int new_rd;
4792
4793 rd = atomic_read(&buffer->record_disabled);
4794 do {
4795 new_rd = rd | RB_BUFFER_OFF;
4796 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4797}
4798EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4799
4800/**
4801 * ring_buffer_record_on - restart writes into the buffer
4802 * @buffer: The ring buffer to start writes to.
4803 *
4804 * This enables all writes to the buffer that was disabled by
4805 * ring_buffer_record_off().
4806 *
4807 * This is different than ring_buffer_record_enable() as
4808 * it works like an on/off switch, where as the enable() version
4809 * must be paired with a disable().
4810 */
4811void ring_buffer_record_on(struct trace_buffer *buffer)
4812{
4813 unsigned int rd;
4814 unsigned int new_rd;
4815
4816 rd = atomic_read(&buffer->record_disabled);
4817 do {
4818 new_rd = rd & ~RB_BUFFER_OFF;
4819 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4820}
4821EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4822
4823/**
4824 * ring_buffer_record_is_on - return true if the ring buffer can write
4825 * @buffer: The ring buffer to see if write is enabled
4826 *
4827 * Returns true if the ring buffer is in a state that it accepts writes.
4828 */
4829bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4830{
4831 return !atomic_read(&buffer->record_disabled);
4832}
4833
4834/**
4835 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4836 * @buffer: The ring buffer to see if write is set enabled
4837 *
4838 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4839 * Note that this does NOT mean it is in a writable state.
4840 *
4841 * It may return true when the ring buffer has been disabled by
4842 * ring_buffer_record_disable(), as that is a temporary disabling of
4843 * the ring buffer.
4844 */
4845bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4846{
4847 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4848}
4849
4850/**
4851 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4852 * @buffer: The ring buffer to stop writes to.
4853 * @cpu: The CPU buffer to stop
4854 *
4855 * This prevents all writes to the buffer. Any attempt to write
4856 * to the buffer after this will fail and return NULL.
4857 *
4858 * The caller should call synchronize_rcu() after this.
4859 */
4860void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4861{
4862 struct ring_buffer_per_cpu *cpu_buffer;
4863
4864 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4865 return;
4866
4867 cpu_buffer = buffer->buffers[cpu];
4868 atomic_inc(&cpu_buffer->record_disabled);
4869}
4870EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4871
4872/**
4873 * ring_buffer_record_enable_cpu - enable writes to the buffer
4874 * @buffer: The ring buffer to enable writes
4875 * @cpu: The CPU to enable.
4876 *
4877 * Note, multiple disables will need the same number of enables
4878 * to truly enable the writing (much like preempt_disable).
4879 */
4880void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4881{
4882 struct ring_buffer_per_cpu *cpu_buffer;
4883
4884 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4885 return;
4886
4887 cpu_buffer = buffer->buffers[cpu];
4888 atomic_dec(&cpu_buffer->record_disabled);
4889}
4890EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4891
4892/*
4893 * The total entries in the ring buffer is the running counter
4894 * of entries entered into the ring buffer, minus the sum of
4895 * the entries read from the ring buffer and the number of
4896 * entries that were overwritten.
4897 */
4898static inline unsigned long
4899rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4900{
4901 return local_read(&cpu_buffer->entries) -
4902 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4903}
4904
4905/**
4906 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4907 * @buffer: The ring buffer
4908 * @cpu: The per CPU buffer to read from.
4909 */
4910u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4911{
4912 unsigned long flags;
4913 struct ring_buffer_per_cpu *cpu_buffer;
4914 struct buffer_page *bpage;
4915 u64 ret = 0;
4916
4917 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4918 return 0;
4919
4920 cpu_buffer = buffer->buffers[cpu];
4921 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4922 /*
4923 * if the tail is on reader_page, oldest time stamp is on the reader
4924 * page
4925 */
4926 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4927 bpage = cpu_buffer->reader_page;
4928 else
4929 bpage = rb_set_head_page(cpu_buffer);
4930 if (bpage)
4931 ret = bpage->page->time_stamp;
4932 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4933
4934 return ret;
4935}
4936EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4937
4938/**
4939 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4940 * @buffer: The ring buffer
4941 * @cpu: The per CPU buffer to read from.
4942 */
4943unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4944{
4945 struct ring_buffer_per_cpu *cpu_buffer;
4946 unsigned long ret;
4947
4948 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4949 return 0;
4950
4951 cpu_buffer = buffer->buffers[cpu];
4952 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4953
4954 return ret;
4955}
4956EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4957
4958/**
4959 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4960 * @buffer: The ring buffer
4961 * @cpu: The per CPU buffer to get the entries from.
4962 */
4963unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4964{
4965 struct ring_buffer_per_cpu *cpu_buffer;
4966
4967 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4968 return 0;
4969
4970 cpu_buffer = buffer->buffers[cpu];
4971
4972 return rb_num_of_entries(cpu_buffer);
4973}
4974EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4975
4976/**
4977 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4978 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4979 * @buffer: The ring buffer
4980 * @cpu: The per CPU buffer to get the number of overruns from
4981 */
4982unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4983{
4984 struct ring_buffer_per_cpu *cpu_buffer;
4985 unsigned long ret;
4986
4987 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4988 return 0;
4989
4990 cpu_buffer = buffer->buffers[cpu];
4991 ret = local_read(&cpu_buffer->overrun);
4992
4993 return ret;
4994}
4995EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4996
4997/**
4998 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4999 * commits failing due to the buffer wrapping around while there are uncommitted
5000 * events, such as during an interrupt storm.
5001 * @buffer: The ring buffer
5002 * @cpu: The per CPU buffer to get the number of overruns from
5003 */
5004unsigned long
5005ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
5006{
5007 struct ring_buffer_per_cpu *cpu_buffer;
5008 unsigned long ret;
5009
5010 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5011 return 0;
5012
5013 cpu_buffer = buffer->buffers[cpu];
5014 ret = local_read(&cpu_buffer->commit_overrun);
5015
5016 return ret;
5017}
5018EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
5019
5020/**
5021 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
5022 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
5023 * @buffer: The ring buffer
5024 * @cpu: The per CPU buffer to get the number of overruns from
5025 */
5026unsigned long
5027ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
5028{
5029 struct ring_buffer_per_cpu *cpu_buffer;
5030 unsigned long ret;
5031
5032 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5033 return 0;
5034
5035 cpu_buffer = buffer->buffers[cpu];
5036 ret = local_read(&cpu_buffer->dropped_events);
5037
5038 return ret;
5039}
5040EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
5041
5042/**
5043 * ring_buffer_read_events_cpu - get the number of events successfully read
5044 * @buffer: The ring buffer
5045 * @cpu: The per CPU buffer to get the number of events read
5046 */
5047unsigned long
5048ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
5049{
5050 struct ring_buffer_per_cpu *cpu_buffer;
5051
5052 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5053 return 0;
5054
5055 cpu_buffer = buffer->buffers[cpu];
5056 return cpu_buffer->read;
5057}
5058EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
5059
5060/**
5061 * ring_buffer_entries - get the number of entries in a buffer
5062 * @buffer: The ring buffer
5063 *
5064 * Returns the total number of entries in the ring buffer
5065 * (all CPU entries)
5066 */
5067unsigned long ring_buffer_entries(struct trace_buffer *buffer)
5068{
5069 struct ring_buffer_per_cpu *cpu_buffer;
5070 unsigned long entries = 0;
5071 int cpu;
5072
5073 /* if you care about this being correct, lock the buffer */
5074 for_each_buffer_cpu(buffer, cpu) {
5075 cpu_buffer = buffer->buffers[cpu];
5076 entries += rb_num_of_entries(cpu_buffer);
5077 }
5078
5079 return entries;
5080}
5081EXPORT_SYMBOL_GPL(ring_buffer_entries);
5082
5083/**
5084 * ring_buffer_overruns - get the number of overruns in buffer
5085 * @buffer: The ring buffer
5086 *
5087 * Returns the total number of overruns in the ring buffer
5088 * (all CPU entries)
5089 */
5090unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
5091{
5092 struct ring_buffer_per_cpu *cpu_buffer;
5093 unsigned long overruns = 0;
5094 int cpu;
5095
5096 /* if you care about this being correct, lock the buffer */
5097 for_each_buffer_cpu(buffer, cpu) {
5098 cpu_buffer = buffer->buffers[cpu];
5099 overruns += local_read(&cpu_buffer->overrun);
5100 }
5101
5102 return overruns;
5103}
5104EXPORT_SYMBOL_GPL(ring_buffer_overruns);
5105
5106static void rb_iter_reset(struct ring_buffer_iter *iter)
5107{
5108 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5109
5110 /* Iterator usage is expected to have record disabled */
5111 iter->head_page = cpu_buffer->reader_page;
5112 iter->head = cpu_buffer->reader_page->read;
5113 iter->next_event = iter->head;
5114
5115 iter->cache_reader_page = iter->head_page;
5116 iter->cache_read = cpu_buffer->read;
5117 iter->cache_pages_removed = cpu_buffer->pages_removed;
5118
5119 if (iter->head) {
5120 iter->read_stamp = cpu_buffer->read_stamp;
5121 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
5122 } else {
5123 iter->read_stamp = iter->head_page->page->time_stamp;
5124 iter->page_stamp = iter->read_stamp;
5125 }
5126}
5127
5128/**
5129 * ring_buffer_iter_reset - reset an iterator
5130 * @iter: The iterator to reset
5131 *
5132 * Resets the iterator, so that it will start from the beginning
5133 * again.
5134 */
5135void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
5136{
5137 struct ring_buffer_per_cpu *cpu_buffer;
5138 unsigned long flags;
5139
5140 if (!iter)
5141 return;
5142
5143 cpu_buffer = iter->cpu_buffer;
5144
5145 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5146 rb_iter_reset(iter);
5147 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5148}
5149EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
5150
5151/**
5152 * ring_buffer_iter_empty - check if an iterator has no more to read
5153 * @iter: The iterator to check
5154 */
5155int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
5156{
5157 struct ring_buffer_per_cpu *cpu_buffer;
5158 struct buffer_page *reader;
5159 struct buffer_page *head_page;
5160 struct buffer_page *commit_page;
5161 struct buffer_page *curr_commit_page;
5162 unsigned commit;
5163 u64 curr_commit_ts;
5164 u64 commit_ts;
5165
5166 cpu_buffer = iter->cpu_buffer;
5167 reader = cpu_buffer->reader_page;
5168 head_page = cpu_buffer->head_page;
5169 commit_page = READ_ONCE(cpu_buffer->commit_page);
5170 commit_ts = commit_page->page->time_stamp;
5171
5172 /*
5173 * When the writer goes across pages, it issues a cmpxchg which
5174 * is a mb(), which will synchronize with the rmb here.
5175 * (see rb_tail_page_update())
5176 */
5177 smp_rmb();
5178 commit = rb_page_commit(commit_page);
5179 /* We want to make sure that the commit page doesn't change */
5180 smp_rmb();
5181
5182 /* Make sure commit page didn't change */
5183 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
5184 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
5185
5186 /* If the commit page changed, then there's more data */
5187 if (curr_commit_page != commit_page ||
5188 curr_commit_ts != commit_ts)
5189 return 0;
5190
5191 /* Still racy, as it may return a false positive, but that's OK */
5192 return ((iter->head_page == commit_page && iter->head >= commit) ||
5193 (iter->head_page == reader && commit_page == head_page &&
5194 head_page->read == commit &&
5195 iter->head == rb_page_size(cpu_buffer->reader_page)));
5196}
5197EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
5198
5199static void
5200rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
5201 struct ring_buffer_event *event)
5202{
5203 u64 delta;
5204
5205 switch (event->type_len) {
5206 case RINGBUF_TYPE_PADDING:
5207 return;
5208
5209 case RINGBUF_TYPE_TIME_EXTEND:
5210 delta = rb_event_time_stamp(event);
5211 cpu_buffer->read_stamp += delta;
5212 return;
5213
5214 case RINGBUF_TYPE_TIME_STAMP:
5215 delta = rb_event_time_stamp(event);
5216 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
5217 cpu_buffer->read_stamp = delta;
5218 return;
5219
5220 case RINGBUF_TYPE_DATA:
5221 cpu_buffer->read_stamp += event->time_delta;
5222 return;
5223
5224 default:
5225 RB_WARN_ON(cpu_buffer, 1);
5226 }
5227}
5228
5229static void
5230rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
5231 struct ring_buffer_event *event)
5232{
5233 u64 delta;
5234
5235 switch (event->type_len) {
5236 case RINGBUF_TYPE_PADDING:
5237 return;
5238
5239 case RINGBUF_TYPE_TIME_EXTEND:
5240 delta = rb_event_time_stamp(event);
5241 iter->read_stamp += delta;
5242 return;
5243
5244 case RINGBUF_TYPE_TIME_STAMP:
5245 delta = rb_event_time_stamp(event);
5246 delta = rb_fix_abs_ts(delta, iter->read_stamp);
5247 iter->read_stamp = delta;
5248 return;
5249
5250 case RINGBUF_TYPE_DATA:
5251 iter->read_stamp += event->time_delta;
5252 return;
5253
5254 default:
5255 RB_WARN_ON(iter->cpu_buffer, 1);
5256 }
5257}
5258
5259static struct buffer_page *
5260rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
5261{
5262 struct buffer_page *reader = NULL;
5263 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
5264 unsigned long overwrite;
5265 unsigned long flags;
5266 int nr_loops = 0;
5267 bool ret;
5268
5269 local_irq_save(flags);
5270 arch_spin_lock(&cpu_buffer->lock);
5271
5272 again:
5273 /*
5274 * This should normally only loop twice. But because the
5275 * start of the reader inserts an empty page, it causes
5276 * a case where we will loop three times. There should be no
5277 * reason to loop four times (that I know of).
5278 */
5279 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
5280 reader = NULL;
5281 goto out;
5282 }
5283
5284 reader = cpu_buffer->reader_page;
5285
5286 /* If there's more to read, return this page */
5287 if (cpu_buffer->reader_page->read < rb_page_size(reader))
5288 goto out;
5289
5290 /* Never should we have an index greater than the size */
5291 if (RB_WARN_ON(cpu_buffer,
5292 cpu_buffer->reader_page->read > rb_page_size(reader)))
5293 goto out;
5294
5295 /* check if we caught up to the tail */
5296 reader = NULL;
5297 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
5298 goto out;
5299
5300 /* Don't bother swapping if the ring buffer is empty */
5301 if (rb_num_of_entries(cpu_buffer) == 0)
5302 goto out;
5303
5304 /*
5305 * Reset the reader page to size zero.
5306 */
5307 local_set(&cpu_buffer->reader_page->write, 0);
5308 local_set(&cpu_buffer->reader_page->entries, 0);
5309 local_set(&cpu_buffer->reader_page->page->commit, 0);
5310 cpu_buffer->reader_page->real_end = 0;
5311
5312 spin:
5313 /*
5314 * Splice the empty reader page into the list around the head.
5315 */
5316 reader = rb_set_head_page(cpu_buffer);
5317 if (!reader)
5318 goto out;
5319 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
5320 cpu_buffer->reader_page->list.prev = reader->list.prev;
5321
5322 /*
5323 * cpu_buffer->pages just needs to point to the buffer, it
5324 * has no specific buffer page to point to. Lets move it out
5325 * of our way so we don't accidentally swap it.
5326 */
5327 cpu_buffer->pages = reader->list.prev;
5328
5329 /* The reader page will be pointing to the new head */
5330 rb_set_list_to_head(&cpu_buffer->reader_page->list);
5331
5332 /*
5333 * We want to make sure we read the overruns after we set up our
5334 * pointers to the next object. The writer side does a
5335 * cmpxchg to cross pages which acts as the mb on the writer
5336 * side. Note, the reader will constantly fail the swap
5337 * while the writer is updating the pointers, so this
5338 * guarantees that the overwrite recorded here is the one we
5339 * want to compare with the last_overrun.
5340 */
5341 smp_mb();
5342 overwrite = local_read(&(cpu_buffer->overrun));
5343
5344 /*
5345 * Here's the tricky part.
5346 *
5347 * We need to move the pointer past the header page.
5348 * But we can only do that if a writer is not currently
5349 * moving it. The page before the header page has the
5350 * flag bit '1' set if it is pointing to the page we want.
5351 * but if the writer is in the process of moving it
5352 * than it will be '2' or already moved '0'.
5353 */
5354
5355 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
5356
5357 /*
5358 * If we did not convert it, then we must try again.
5359 */
5360 if (!ret)
5361 goto spin;
5362
5363 if (cpu_buffer->ring_meta)
5364 rb_update_meta_reader(cpu_buffer, reader);
5365
5366 /*
5367 * Yay! We succeeded in replacing the page.
5368 *
5369 * Now make the new head point back to the reader page.
5370 */
5371 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
5372 rb_inc_page(&cpu_buffer->head_page);
5373
5374 cpu_buffer->cnt++;
5375 local_inc(&cpu_buffer->pages_read);
5376
5377 /* Finally update the reader page to the new head */
5378 cpu_buffer->reader_page = reader;
5379 cpu_buffer->reader_page->read = 0;
5380
5381 if (overwrite != cpu_buffer->last_overrun) {
5382 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
5383 cpu_buffer->last_overrun = overwrite;
5384 }
5385
5386 goto again;
5387
5388 out:
5389 /* Update the read_stamp on the first event */
5390 if (reader && reader->read == 0)
5391 cpu_buffer->read_stamp = reader->page->time_stamp;
5392
5393 arch_spin_unlock(&cpu_buffer->lock);
5394 local_irq_restore(flags);
5395
5396 /*
5397 * The writer has preempt disable, wait for it. But not forever
5398 * Although, 1 second is pretty much "forever"
5399 */
5400#define USECS_WAIT 1000000
5401 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
5402 /* If the write is past the end of page, a writer is still updating it */
5403 if (likely(!reader || rb_page_write(reader) <= bsize))
5404 break;
5405
5406 udelay(1);
5407
5408 /* Get the latest version of the reader write value */
5409 smp_rmb();
5410 }
5411
5412 /* The writer is not moving forward? Something is wrong */
5413 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
5414 reader = NULL;
5415
5416 /*
5417 * Make sure we see any padding after the write update
5418 * (see rb_reset_tail()).
5419 *
5420 * In addition, a writer may be writing on the reader page
5421 * if the page has not been fully filled, so the read barrier
5422 * is also needed to make sure we see the content of what is
5423 * committed by the writer (see rb_set_commit_to_write()).
5424 */
5425 smp_rmb();
5426
5427
5428 return reader;
5429}
5430
5431static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
5432{
5433 struct ring_buffer_event *event;
5434 struct buffer_page *reader;
5435 unsigned length;
5436
5437 reader = rb_get_reader_page(cpu_buffer);
5438
5439 /* This function should not be called when buffer is empty */
5440 if (RB_WARN_ON(cpu_buffer, !reader))
5441 return;
5442
5443 event = rb_reader_event(cpu_buffer);
5444
5445 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
5446 cpu_buffer->read++;
5447
5448 rb_update_read_stamp(cpu_buffer, event);
5449
5450 length = rb_event_length(event);
5451 cpu_buffer->reader_page->read += length;
5452 cpu_buffer->read_bytes += length;
5453}
5454
5455static void rb_advance_iter(struct ring_buffer_iter *iter)
5456{
5457 struct ring_buffer_per_cpu *cpu_buffer;
5458
5459 cpu_buffer = iter->cpu_buffer;
5460
5461 /* If head == next_event then we need to jump to the next event */
5462 if (iter->head == iter->next_event) {
5463 /* If the event gets overwritten again, there's nothing to do */
5464 if (rb_iter_head_event(iter) == NULL)
5465 return;
5466 }
5467
5468 iter->head = iter->next_event;
5469
5470 /*
5471 * Check if we are at the end of the buffer.
5472 */
5473 if (iter->next_event >= rb_page_size(iter->head_page)) {
5474 /* discarded commits can make the page empty */
5475 if (iter->head_page == cpu_buffer->commit_page)
5476 return;
5477 rb_inc_iter(iter);
5478 return;
5479 }
5480
5481 rb_update_iter_read_stamp(iter, iter->event);
5482}
5483
5484static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
5485{
5486 return cpu_buffer->lost_events;
5487}
5488
5489static struct ring_buffer_event *
5490rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
5491 unsigned long *lost_events)
5492{
5493 struct ring_buffer_event *event;
5494 struct buffer_page *reader;
5495 int nr_loops = 0;
5496
5497 if (ts)
5498 *ts = 0;
5499 again:
5500 /*
5501 * We repeat when a time extend is encountered.
5502 * Since the time extend is always attached to a data event,
5503 * we should never loop more than once.
5504 * (We never hit the following condition more than twice).
5505 */
5506 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
5507 return NULL;
5508
5509 reader = rb_get_reader_page(cpu_buffer);
5510 if (!reader)
5511 return NULL;
5512
5513 event = rb_reader_event(cpu_buffer);
5514
5515 switch (event->type_len) {
5516 case RINGBUF_TYPE_PADDING:
5517 if (rb_null_event(event))
5518 RB_WARN_ON(cpu_buffer, 1);
5519 /*
5520 * Because the writer could be discarding every
5521 * event it creates (which would probably be bad)
5522 * if we were to go back to "again" then we may never
5523 * catch up, and will trigger the warn on, or lock
5524 * the box. Return the padding, and we will release
5525 * the current locks, and try again.
5526 */
5527 return event;
5528
5529 case RINGBUF_TYPE_TIME_EXTEND:
5530 /* Internal data, OK to advance */
5531 rb_advance_reader(cpu_buffer);
5532 goto again;
5533
5534 case RINGBUF_TYPE_TIME_STAMP:
5535 if (ts) {
5536 *ts = rb_event_time_stamp(event);
5537 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
5538 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5539 cpu_buffer->cpu, ts);
5540 }
5541 /* Internal data, OK to advance */
5542 rb_advance_reader(cpu_buffer);
5543 goto again;
5544
5545 case RINGBUF_TYPE_DATA:
5546 if (ts && !(*ts)) {
5547 *ts = cpu_buffer->read_stamp + event->time_delta;
5548 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5549 cpu_buffer->cpu, ts);
5550 }
5551 if (lost_events)
5552 *lost_events = rb_lost_events(cpu_buffer);
5553 return event;
5554
5555 default:
5556 RB_WARN_ON(cpu_buffer, 1);
5557 }
5558
5559 return NULL;
5560}
5561EXPORT_SYMBOL_GPL(ring_buffer_peek);
5562
5563static struct ring_buffer_event *
5564rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5565{
5566 struct trace_buffer *buffer;
5567 struct ring_buffer_per_cpu *cpu_buffer;
5568 struct ring_buffer_event *event;
5569 int nr_loops = 0;
5570
5571 if (ts)
5572 *ts = 0;
5573
5574 cpu_buffer = iter->cpu_buffer;
5575 buffer = cpu_buffer->buffer;
5576
5577 /*
5578 * Check if someone performed a consuming read to the buffer
5579 * or removed some pages from the buffer. In these cases,
5580 * iterator was invalidated and we need to reset it.
5581 */
5582 if (unlikely(iter->cache_read != cpu_buffer->read ||
5583 iter->cache_reader_page != cpu_buffer->reader_page ||
5584 iter->cache_pages_removed != cpu_buffer->pages_removed))
5585 rb_iter_reset(iter);
5586
5587 again:
5588 if (ring_buffer_iter_empty(iter))
5589 return NULL;
5590
5591 /*
5592 * As the writer can mess with what the iterator is trying
5593 * to read, just give up if we fail to get an event after
5594 * three tries. The iterator is not as reliable when reading
5595 * the ring buffer with an active write as the consumer is.
5596 * Do not warn if the three failures is reached.
5597 */
5598 if (++nr_loops > 3)
5599 return NULL;
5600
5601 if (rb_per_cpu_empty(cpu_buffer))
5602 return NULL;
5603
5604 if (iter->head >= rb_page_size(iter->head_page)) {
5605 rb_inc_iter(iter);
5606 goto again;
5607 }
5608
5609 event = rb_iter_head_event(iter);
5610 if (!event)
5611 goto again;
5612
5613 switch (event->type_len) {
5614 case RINGBUF_TYPE_PADDING:
5615 if (rb_null_event(event)) {
5616 rb_inc_iter(iter);
5617 goto again;
5618 }
5619 rb_advance_iter(iter);
5620 return event;
5621
5622 case RINGBUF_TYPE_TIME_EXTEND:
5623 /* Internal data, OK to advance */
5624 rb_advance_iter(iter);
5625 goto again;
5626
5627 case RINGBUF_TYPE_TIME_STAMP:
5628 if (ts) {
5629 *ts = rb_event_time_stamp(event);
5630 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
5631 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5632 cpu_buffer->cpu, ts);
5633 }
5634 /* Internal data, OK to advance */
5635 rb_advance_iter(iter);
5636 goto again;
5637
5638 case RINGBUF_TYPE_DATA:
5639 if (ts && !(*ts)) {
5640 *ts = iter->read_stamp + event->time_delta;
5641 ring_buffer_normalize_time_stamp(buffer,
5642 cpu_buffer->cpu, ts);
5643 }
5644 return event;
5645
5646 default:
5647 RB_WARN_ON(cpu_buffer, 1);
5648 }
5649
5650 return NULL;
5651}
5652EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
5653
5654static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
5655{
5656 if (likely(!in_nmi())) {
5657 raw_spin_lock(&cpu_buffer->reader_lock);
5658 return true;
5659 }
5660
5661 /*
5662 * If an NMI die dumps out the content of the ring buffer
5663 * trylock must be used to prevent a deadlock if the NMI
5664 * preempted a task that holds the ring buffer locks. If
5665 * we get the lock then all is fine, if not, then continue
5666 * to do the read, but this can corrupt the ring buffer,
5667 * so it must be permanently disabled from future writes.
5668 * Reading from NMI is a oneshot deal.
5669 */
5670 if (raw_spin_trylock(&cpu_buffer->reader_lock))
5671 return true;
5672
5673 /* Continue without locking, but disable the ring buffer */
5674 atomic_inc(&cpu_buffer->record_disabled);
5675 return false;
5676}
5677
5678static inline void
5679rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
5680{
5681 if (likely(locked))
5682 raw_spin_unlock(&cpu_buffer->reader_lock);
5683}
5684
5685/**
5686 * ring_buffer_peek - peek at the next event to be read
5687 * @buffer: The ring buffer to read
5688 * @cpu: The cpu to peak at
5689 * @ts: The timestamp counter of this event.
5690 * @lost_events: a variable to store if events were lost (may be NULL)
5691 *
5692 * This will return the event that will be read next, but does
5693 * not consume the data.
5694 */
5695struct ring_buffer_event *
5696ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
5697 unsigned long *lost_events)
5698{
5699 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5700 struct ring_buffer_event *event;
5701 unsigned long flags;
5702 bool dolock;
5703
5704 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5705 return NULL;
5706
5707 again:
5708 local_irq_save(flags);
5709 dolock = rb_reader_lock(cpu_buffer);
5710 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5711 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5712 rb_advance_reader(cpu_buffer);
5713 rb_reader_unlock(cpu_buffer, dolock);
5714 local_irq_restore(flags);
5715
5716 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5717 goto again;
5718
5719 return event;
5720}
5721
5722/** ring_buffer_iter_dropped - report if there are dropped events
5723 * @iter: The ring buffer iterator
5724 *
5725 * Returns true if there was dropped events since the last peek.
5726 */
5727bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
5728{
5729 bool ret = iter->missed_events != 0;
5730
5731 iter->missed_events = 0;
5732 return ret;
5733}
5734EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
5735
5736/**
5737 * ring_buffer_iter_peek - peek at the next event to be read
5738 * @iter: The ring buffer iterator
5739 * @ts: The timestamp counter of this event.
5740 *
5741 * This will return the event that will be read next, but does
5742 * not increment the iterator.
5743 */
5744struct ring_buffer_event *
5745ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5746{
5747 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5748 struct ring_buffer_event *event;
5749 unsigned long flags;
5750
5751 again:
5752 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5753 event = rb_iter_peek(iter, ts);
5754 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5755
5756 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5757 goto again;
5758
5759 return event;
5760}
5761
5762/**
5763 * ring_buffer_consume - return an event and consume it
5764 * @buffer: The ring buffer to get the next event from
5765 * @cpu: the cpu to read the buffer from
5766 * @ts: a variable to store the timestamp (may be NULL)
5767 * @lost_events: a variable to store if events were lost (may be NULL)
5768 *
5769 * Returns the next event in the ring buffer, and that event is consumed.
5770 * Meaning, that sequential reads will keep returning a different event,
5771 * and eventually empty the ring buffer if the producer is slower.
5772 */
5773struct ring_buffer_event *
5774ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5775 unsigned long *lost_events)
5776{
5777 struct ring_buffer_per_cpu *cpu_buffer;
5778 struct ring_buffer_event *event = NULL;
5779 unsigned long flags;
5780 bool dolock;
5781
5782 again:
5783 /* might be called in atomic */
5784 preempt_disable();
5785
5786 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5787 goto out;
5788
5789 cpu_buffer = buffer->buffers[cpu];
5790 local_irq_save(flags);
5791 dolock = rb_reader_lock(cpu_buffer);
5792
5793 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5794 if (event) {
5795 cpu_buffer->lost_events = 0;
5796 rb_advance_reader(cpu_buffer);
5797 }
5798
5799 rb_reader_unlock(cpu_buffer, dolock);
5800 local_irq_restore(flags);
5801
5802 out:
5803 preempt_enable();
5804
5805 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5806 goto again;
5807
5808 return event;
5809}
5810EXPORT_SYMBOL_GPL(ring_buffer_consume);
5811
5812/**
5813 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5814 * @buffer: The ring buffer to read from
5815 * @cpu: The cpu buffer to iterate over
5816 * @flags: gfp flags to use for memory allocation
5817 *
5818 * This performs the initial preparations necessary to iterate
5819 * through the buffer. Memory is allocated, buffer resizing
5820 * is disabled, and the iterator pointer is returned to the caller.
5821 *
5822 * After a sequence of ring_buffer_read_prepare calls, the user is
5823 * expected to make at least one call to ring_buffer_read_prepare_sync.
5824 * Afterwards, ring_buffer_read_start is invoked to get things going
5825 * for real.
5826 *
5827 * This overall must be paired with ring_buffer_read_finish.
5828 */
5829struct ring_buffer_iter *
5830ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5831{
5832 struct ring_buffer_per_cpu *cpu_buffer;
5833 struct ring_buffer_iter *iter;
5834
5835 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5836 return NULL;
5837
5838 iter = kzalloc(sizeof(*iter), flags);
5839 if (!iter)
5840 return NULL;
5841
5842 /* Holds the entire event: data and meta data */
5843 iter->event_size = buffer->subbuf_size;
5844 iter->event = kmalloc(iter->event_size, flags);
5845 if (!iter->event) {
5846 kfree(iter);
5847 return NULL;
5848 }
5849
5850 cpu_buffer = buffer->buffers[cpu];
5851
5852 iter->cpu_buffer = cpu_buffer;
5853
5854 atomic_inc(&cpu_buffer->resize_disabled);
5855
5856 return iter;
5857}
5858EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5859
5860/**
5861 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5862 *
5863 * All previously invoked ring_buffer_read_prepare calls to prepare
5864 * iterators will be synchronized. Afterwards, read_buffer_read_start
5865 * calls on those iterators are allowed.
5866 */
5867void
5868ring_buffer_read_prepare_sync(void)
5869{
5870 synchronize_rcu();
5871}
5872EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5873
5874/**
5875 * ring_buffer_read_start - start a non consuming read of the buffer
5876 * @iter: The iterator returned by ring_buffer_read_prepare
5877 *
5878 * This finalizes the startup of an iteration through the buffer.
5879 * The iterator comes from a call to ring_buffer_read_prepare and
5880 * an intervening ring_buffer_read_prepare_sync must have been
5881 * performed.
5882 *
5883 * Must be paired with ring_buffer_read_finish.
5884 */
5885void
5886ring_buffer_read_start(struct ring_buffer_iter *iter)
5887{
5888 struct ring_buffer_per_cpu *cpu_buffer;
5889 unsigned long flags;
5890
5891 if (!iter)
5892 return;
5893
5894 cpu_buffer = iter->cpu_buffer;
5895
5896 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5897 arch_spin_lock(&cpu_buffer->lock);
5898 rb_iter_reset(iter);
5899 arch_spin_unlock(&cpu_buffer->lock);
5900 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5901}
5902EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5903
5904/**
5905 * ring_buffer_read_finish - finish reading the iterator of the buffer
5906 * @iter: The iterator retrieved by ring_buffer_start
5907 *
5908 * This re-enables resizing of the buffer, and frees the iterator.
5909 */
5910void
5911ring_buffer_read_finish(struct ring_buffer_iter *iter)
5912{
5913 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5914
5915 /* Use this opportunity to check the integrity of the ring buffer. */
5916 rb_check_pages(cpu_buffer);
5917
5918 atomic_dec(&cpu_buffer->resize_disabled);
5919 kfree(iter->event);
5920 kfree(iter);
5921}
5922EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5923
5924/**
5925 * ring_buffer_iter_advance - advance the iterator to the next location
5926 * @iter: The ring buffer iterator
5927 *
5928 * Move the location of the iterator such that the next read will
5929 * be the next location of the iterator.
5930 */
5931void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5932{
5933 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5934 unsigned long flags;
5935
5936 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5937
5938 rb_advance_iter(iter);
5939
5940 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5941}
5942EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5943
5944/**
5945 * ring_buffer_size - return the size of the ring buffer (in bytes)
5946 * @buffer: The ring buffer.
5947 * @cpu: The CPU to get ring buffer size from.
5948 */
5949unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5950{
5951 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5952 return 0;
5953
5954 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5955}
5956EXPORT_SYMBOL_GPL(ring_buffer_size);
5957
5958/**
5959 * ring_buffer_max_event_size - return the max data size of an event
5960 * @buffer: The ring buffer.
5961 *
5962 * Returns the maximum size an event can be.
5963 */
5964unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5965{
5966 /* If abs timestamp is requested, events have a timestamp too */
5967 if (ring_buffer_time_stamp_abs(buffer))
5968 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5969 return buffer->max_data_size;
5970}
5971EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5972
5973static void rb_clear_buffer_page(struct buffer_page *page)
5974{
5975 local_set(&page->write, 0);
5976 local_set(&page->entries, 0);
5977 rb_init_page(page->page);
5978 page->read = 0;
5979}
5980
5981static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
5982{
5983 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
5984
5985 if (!meta)
5986 return;
5987
5988 meta->reader.read = cpu_buffer->reader_page->read;
5989 meta->reader.id = cpu_buffer->reader_page->id;
5990 meta->reader.lost_events = cpu_buffer->lost_events;
5991
5992 meta->entries = local_read(&cpu_buffer->entries);
5993 meta->overrun = local_read(&cpu_buffer->overrun);
5994 meta->read = cpu_buffer->read;
5995
5996 /* Some archs do not have data cache coherency between kernel and user-space */
5997 flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page));
5998}
5999
6000static void
6001rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
6002{
6003 struct buffer_page *page;
6004
6005 rb_head_page_deactivate(cpu_buffer);
6006
6007 cpu_buffer->head_page
6008 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6009 rb_clear_buffer_page(cpu_buffer->head_page);
6010 list_for_each_entry(page, cpu_buffer->pages, list) {
6011 rb_clear_buffer_page(page);
6012 }
6013
6014 cpu_buffer->tail_page = cpu_buffer->head_page;
6015 cpu_buffer->commit_page = cpu_buffer->head_page;
6016
6017 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
6018 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6019 rb_clear_buffer_page(cpu_buffer->reader_page);
6020
6021 local_set(&cpu_buffer->entries_bytes, 0);
6022 local_set(&cpu_buffer->overrun, 0);
6023 local_set(&cpu_buffer->commit_overrun, 0);
6024 local_set(&cpu_buffer->dropped_events, 0);
6025 local_set(&cpu_buffer->entries, 0);
6026 local_set(&cpu_buffer->committing, 0);
6027 local_set(&cpu_buffer->commits, 0);
6028 local_set(&cpu_buffer->pages_touched, 0);
6029 local_set(&cpu_buffer->pages_lost, 0);
6030 local_set(&cpu_buffer->pages_read, 0);
6031 cpu_buffer->last_pages_touch = 0;
6032 cpu_buffer->shortest_full = 0;
6033 cpu_buffer->read = 0;
6034 cpu_buffer->read_bytes = 0;
6035
6036 rb_time_set(&cpu_buffer->write_stamp, 0);
6037 rb_time_set(&cpu_buffer->before_stamp, 0);
6038
6039 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
6040
6041 cpu_buffer->lost_events = 0;
6042 cpu_buffer->last_overrun = 0;
6043
6044 rb_head_page_activate(cpu_buffer);
6045 cpu_buffer->pages_removed = 0;
6046
6047 if (cpu_buffer->mapped) {
6048 rb_update_meta_page(cpu_buffer);
6049 if (cpu_buffer->ring_meta) {
6050 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
6051 meta->commit_buffer = meta->head_buffer;
6052 }
6053 }
6054}
6055
6056/* Must have disabled the cpu buffer then done a synchronize_rcu */
6057static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6058{
6059 unsigned long flags;
6060
6061 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6062
6063 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
6064 goto out;
6065
6066 arch_spin_lock(&cpu_buffer->lock);
6067
6068 rb_reset_cpu(cpu_buffer);
6069
6070 arch_spin_unlock(&cpu_buffer->lock);
6071
6072 out:
6073 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6074}
6075
6076/**
6077 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
6078 * @buffer: The ring buffer to reset a per cpu buffer of
6079 * @cpu: The CPU buffer to be reset
6080 */
6081void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
6082{
6083 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6084 struct ring_buffer_meta *meta;
6085
6086 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6087 return;
6088
6089 /* prevent another thread from changing buffer sizes */
6090 mutex_lock(&buffer->mutex);
6091
6092 atomic_inc(&cpu_buffer->resize_disabled);
6093 atomic_inc(&cpu_buffer->record_disabled);
6094
6095 /* Make sure all commits have finished */
6096 synchronize_rcu();
6097
6098 reset_disabled_cpu_buffer(cpu_buffer);
6099
6100 atomic_dec(&cpu_buffer->record_disabled);
6101 atomic_dec(&cpu_buffer->resize_disabled);
6102
6103 /* Make sure persistent meta now uses this buffer's addresses */
6104 meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
6105 if (meta)
6106 rb_meta_init_text_addr(meta);
6107
6108 mutex_unlock(&buffer->mutex);
6109}
6110EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
6111
6112/* Flag to ensure proper resetting of atomic variables */
6113#define RESET_BIT (1 << 30)
6114
6115/**
6116 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
6117 * @buffer: The ring buffer to reset a per cpu buffer of
6118 */
6119void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
6120{
6121 struct ring_buffer_per_cpu *cpu_buffer;
6122 struct ring_buffer_meta *meta;
6123 int cpu;
6124
6125 /* prevent another thread from changing buffer sizes */
6126 mutex_lock(&buffer->mutex);
6127
6128 for_each_online_buffer_cpu(buffer, cpu) {
6129 cpu_buffer = buffer->buffers[cpu];
6130
6131 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
6132 atomic_inc(&cpu_buffer->record_disabled);
6133 }
6134
6135 /* Make sure all commits have finished */
6136 synchronize_rcu();
6137
6138 for_each_buffer_cpu(buffer, cpu) {
6139 cpu_buffer = buffer->buffers[cpu];
6140
6141 /*
6142 * If a CPU came online during the synchronize_rcu(), then
6143 * ignore it.
6144 */
6145 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
6146 continue;
6147
6148 reset_disabled_cpu_buffer(cpu_buffer);
6149
6150 /* Make sure persistent meta now uses this buffer's addresses */
6151 meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
6152 if (meta)
6153 rb_meta_init_text_addr(meta);
6154
6155 atomic_dec(&cpu_buffer->record_disabled);
6156 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
6157 }
6158
6159 mutex_unlock(&buffer->mutex);
6160}
6161
6162/**
6163 * ring_buffer_reset - reset a ring buffer
6164 * @buffer: The ring buffer to reset all cpu buffers
6165 */
6166void ring_buffer_reset(struct trace_buffer *buffer)
6167{
6168 struct ring_buffer_per_cpu *cpu_buffer;
6169 int cpu;
6170
6171 /* prevent another thread from changing buffer sizes */
6172 mutex_lock(&buffer->mutex);
6173
6174 for_each_buffer_cpu(buffer, cpu) {
6175 cpu_buffer = buffer->buffers[cpu];
6176
6177 atomic_inc(&cpu_buffer->resize_disabled);
6178 atomic_inc(&cpu_buffer->record_disabled);
6179 }
6180
6181 /* Make sure all commits have finished */
6182 synchronize_rcu();
6183
6184 for_each_buffer_cpu(buffer, cpu) {
6185 cpu_buffer = buffer->buffers[cpu];
6186
6187 reset_disabled_cpu_buffer(cpu_buffer);
6188
6189 atomic_dec(&cpu_buffer->record_disabled);
6190 atomic_dec(&cpu_buffer->resize_disabled);
6191 }
6192
6193 mutex_unlock(&buffer->mutex);
6194}
6195EXPORT_SYMBOL_GPL(ring_buffer_reset);
6196
6197/**
6198 * ring_buffer_empty - is the ring buffer empty?
6199 * @buffer: The ring buffer to test
6200 */
6201bool ring_buffer_empty(struct trace_buffer *buffer)
6202{
6203 struct ring_buffer_per_cpu *cpu_buffer;
6204 unsigned long flags;
6205 bool dolock;
6206 bool ret;
6207 int cpu;
6208
6209 /* yes this is racy, but if you don't like the race, lock the buffer */
6210 for_each_buffer_cpu(buffer, cpu) {
6211 cpu_buffer = buffer->buffers[cpu];
6212 local_irq_save(flags);
6213 dolock = rb_reader_lock(cpu_buffer);
6214 ret = rb_per_cpu_empty(cpu_buffer);
6215 rb_reader_unlock(cpu_buffer, dolock);
6216 local_irq_restore(flags);
6217
6218 if (!ret)
6219 return false;
6220 }
6221
6222 return true;
6223}
6224EXPORT_SYMBOL_GPL(ring_buffer_empty);
6225
6226/**
6227 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
6228 * @buffer: The ring buffer
6229 * @cpu: The CPU buffer to test
6230 */
6231bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
6232{
6233 struct ring_buffer_per_cpu *cpu_buffer;
6234 unsigned long flags;
6235 bool dolock;
6236 bool ret;
6237
6238 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6239 return true;
6240
6241 cpu_buffer = buffer->buffers[cpu];
6242 local_irq_save(flags);
6243 dolock = rb_reader_lock(cpu_buffer);
6244 ret = rb_per_cpu_empty(cpu_buffer);
6245 rb_reader_unlock(cpu_buffer, dolock);
6246 local_irq_restore(flags);
6247
6248 return ret;
6249}
6250EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
6251
6252#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
6253/**
6254 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
6255 * @buffer_a: One buffer to swap with
6256 * @buffer_b: The other buffer to swap with
6257 * @cpu: the CPU of the buffers to swap
6258 *
6259 * This function is useful for tracers that want to take a "snapshot"
6260 * of a CPU buffer and has another back up buffer lying around.
6261 * it is expected that the tracer handles the cpu buffer not being
6262 * used at the moment.
6263 */
6264int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
6265 struct trace_buffer *buffer_b, int cpu)
6266{
6267 struct ring_buffer_per_cpu *cpu_buffer_a;
6268 struct ring_buffer_per_cpu *cpu_buffer_b;
6269 int ret = -EINVAL;
6270
6271 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
6272 !cpumask_test_cpu(cpu, buffer_b->cpumask))
6273 goto out;
6274
6275 cpu_buffer_a = buffer_a->buffers[cpu];
6276 cpu_buffer_b = buffer_b->buffers[cpu];
6277
6278 /* It's up to the callers to not try to swap mapped buffers */
6279 if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
6280 ret = -EBUSY;
6281 goto out;
6282 }
6283
6284 /* At least make sure the two buffers are somewhat the same */
6285 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
6286 goto out;
6287
6288 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
6289 goto out;
6290
6291 ret = -EAGAIN;
6292
6293 if (atomic_read(&buffer_a->record_disabled))
6294 goto out;
6295
6296 if (atomic_read(&buffer_b->record_disabled))
6297 goto out;
6298
6299 if (atomic_read(&cpu_buffer_a->record_disabled))
6300 goto out;
6301
6302 if (atomic_read(&cpu_buffer_b->record_disabled))
6303 goto out;
6304
6305 /*
6306 * We can't do a synchronize_rcu here because this
6307 * function can be called in atomic context.
6308 * Normally this will be called from the same CPU as cpu.
6309 * If not it's up to the caller to protect this.
6310 */
6311 atomic_inc(&cpu_buffer_a->record_disabled);
6312 atomic_inc(&cpu_buffer_b->record_disabled);
6313
6314 ret = -EBUSY;
6315 if (local_read(&cpu_buffer_a->committing))
6316 goto out_dec;
6317 if (local_read(&cpu_buffer_b->committing))
6318 goto out_dec;
6319
6320 /*
6321 * When resize is in progress, we cannot swap it because
6322 * it will mess the state of the cpu buffer.
6323 */
6324 if (atomic_read(&buffer_a->resizing))
6325 goto out_dec;
6326 if (atomic_read(&buffer_b->resizing))
6327 goto out_dec;
6328
6329 buffer_a->buffers[cpu] = cpu_buffer_b;
6330 buffer_b->buffers[cpu] = cpu_buffer_a;
6331
6332 cpu_buffer_b->buffer = buffer_a;
6333 cpu_buffer_a->buffer = buffer_b;
6334
6335 ret = 0;
6336
6337out_dec:
6338 atomic_dec(&cpu_buffer_a->record_disabled);
6339 atomic_dec(&cpu_buffer_b->record_disabled);
6340out:
6341 return ret;
6342}
6343EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
6344#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
6345
6346/**
6347 * ring_buffer_alloc_read_page - allocate a page to read from buffer
6348 * @buffer: the buffer to allocate for.
6349 * @cpu: the cpu buffer to allocate.
6350 *
6351 * This function is used in conjunction with ring_buffer_read_page.
6352 * When reading a full page from the ring buffer, these functions
6353 * can be used to speed up the process. The calling function should
6354 * allocate a few pages first with this function. Then when it
6355 * needs to get pages from the ring buffer, it passes the result
6356 * of this function into ring_buffer_read_page, which will swap
6357 * the page that was allocated, with the read page of the buffer.
6358 *
6359 * Returns:
6360 * The page allocated, or ERR_PTR
6361 */
6362struct buffer_data_read_page *
6363ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
6364{
6365 struct ring_buffer_per_cpu *cpu_buffer;
6366 struct buffer_data_read_page *bpage = NULL;
6367 unsigned long flags;
6368 struct page *page;
6369
6370 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6371 return ERR_PTR(-ENODEV);
6372
6373 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
6374 if (!bpage)
6375 return ERR_PTR(-ENOMEM);
6376
6377 bpage->order = buffer->subbuf_order;
6378 cpu_buffer = buffer->buffers[cpu];
6379 local_irq_save(flags);
6380 arch_spin_lock(&cpu_buffer->lock);
6381
6382 if (cpu_buffer->free_page) {
6383 bpage->data = cpu_buffer->free_page;
6384 cpu_buffer->free_page = NULL;
6385 }
6386
6387 arch_spin_unlock(&cpu_buffer->lock);
6388 local_irq_restore(flags);
6389
6390 if (bpage->data)
6391 goto out;
6392
6393 page = alloc_pages_node(cpu_to_node(cpu),
6394 GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
6395 cpu_buffer->buffer->subbuf_order);
6396 if (!page) {
6397 kfree(bpage);
6398 return ERR_PTR(-ENOMEM);
6399 }
6400
6401 bpage->data = page_address(page);
6402
6403 out:
6404 rb_init_page(bpage->data);
6405
6406 return bpage;
6407}
6408EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
6409
6410/**
6411 * ring_buffer_free_read_page - free an allocated read page
6412 * @buffer: the buffer the page was allocate for
6413 * @cpu: the cpu buffer the page came from
6414 * @data_page: the page to free
6415 *
6416 * Free a page allocated from ring_buffer_alloc_read_page.
6417 */
6418void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
6419 struct buffer_data_read_page *data_page)
6420{
6421 struct ring_buffer_per_cpu *cpu_buffer;
6422 struct buffer_data_page *bpage = data_page->data;
6423 struct page *page = virt_to_page(bpage);
6424 unsigned long flags;
6425
6426 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
6427 return;
6428
6429 cpu_buffer = buffer->buffers[cpu];
6430
6431 /*
6432 * If the page is still in use someplace else, or order of the page
6433 * is different from the subbuffer order of the buffer -
6434 * we can't reuse it
6435 */
6436 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
6437 goto out;
6438
6439 local_irq_save(flags);
6440 arch_spin_lock(&cpu_buffer->lock);
6441
6442 if (!cpu_buffer->free_page) {
6443 cpu_buffer->free_page = bpage;
6444 bpage = NULL;
6445 }
6446
6447 arch_spin_unlock(&cpu_buffer->lock);
6448 local_irq_restore(flags);
6449
6450 out:
6451 free_pages((unsigned long)bpage, data_page->order);
6452 kfree(data_page);
6453}
6454EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
6455
6456/**
6457 * ring_buffer_read_page - extract a page from the ring buffer
6458 * @buffer: buffer to extract from
6459 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
6460 * @len: amount to extract
6461 * @cpu: the cpu of the buffer to extract
6462 * @full: should the extraction only happen when the page is full.
6463 *
6464 * This function will pull out a page from the ring buffer and consume it.
6465 * @data_page must be the address of the variable that was returned
6466 * from ring_buffer_alloc_read_page. This is because the page might be used
6467 * to swap with a page in the ring buffer.
6468 *
6469 * for example:
6470 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
6471 * if (IS_ERR(rpage))
6472 * return PTR_ERR(rpage);
6473 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
6474 * if (ret >= 0)
6475 * process_page(ring_buffer_read_page_data(rpage), ret);
6476 * ring_buffer_free_read_page(buffer, cpu, rpage);
6477 *
6478 * When @full is set, the function will not return true unless
6479 * the writer is off the reader page.
6480 *
6481 * Note: it is up to the calling functions to handle sleeps and wakeups.
6482 * The ring buffer can be used anywhere in the kernel and can not
6483 * blindly call wake_up. The layer that uses the ring buffer must be
6484 * responsible for that.
6485 *
6486 * Returns:
6487 * >=0 if data has been transferred, returns the offset of consumed data.
6488 * <0 if no data has been transferred.
6489 */
6490int ring_buffer_read_page(struct trace_buffer *buffer,
6491 struct buffer_data_read_page *data_page,
6492 size_t len, int cpu, int full)
6493{
6494 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6495 struct ring_buffer_event *event;
6496 struct buffer_data_page *bpage;
6497 struct buffer_page *reader;
6498 unsigned long missed_events;
6499 unsigned long flags;
6500 unsigned int commit;
6501 unsigned int read;
6502 u64 save_timestamp;
6503 int ret = -1;
6504
6505 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6506 goto out;
6507
6508 /*
6509 * If len is not big enough to hold the page header, then
6510 * we can not copy anything.
6511 */
6512 if (len <= BUF_PAGE_HDR_SIZE)
6513 goto out;
6514
6515 len -= BUF_PAGE_HDR_SIZE;
6516
6517 if (!data_page || !data_page->data)
6518 goto out;
6519 if (data_page->order != buffer->subbuf_order)
6520 goto out;
6521
6522 bpage = data_page->data;
6523 if (!bpage)
6524 goto out;
6525
6526 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6527
6528 reader = rb_get_reader_page(cpu_buffer);
6529 if (!reader)
6530 goto out_unlock;
6531
6532 event = rb_reader_event(cpu_buffer);
6533
6534 read = reader->read;
6535 commit = rb_page_size(reader);
6536
6537 /* Check if any events were dropped */
6538 missed_events = cpu_buffer->lost_events;
6539
6540 /*
6541 * If this page has been partially read or
6542 * if len is not big enough to read the rest of the page or
6543 * a writer is still on the page, then
6544 * we must copy the data from the page to the buffer.
6545 * Otherwise, we can simply swap the page with the one passed in.
6546 */
6547 if (read || (len < (commit - read)) ||
6548 cpu_buffer->reader_page == cpu_buffer->commit_page ||
6549 cpu_buffer->mapped) {
6550 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
6551 unsigned int rpos = read;
6552 unsigned int pos = 0;
6553 unsigned int size;
6554
6555 /*
6556 * If a full page is expected, this can still be returned
6557 * if there's been a previous partial read and the
6558 * rest of the page can be read and the commit page is off
6559 * the reader page.
6560 */
6561 if (full &&
6562 (!read || (len < (commit - read)) ||
6563 cpu_buffer->reader_page == cpu_buffer->commit_page))
6564 goto out_unlock;
6565
6566 if (len > (commit - read))
6567 len = (commit - read);
6568
6569 /* Always keep the time extend and data together */
6570 size = rb_event_ts_length(event);
6571
6572 if (len < size)
6573 goto out_unlock;
6574
6575 /* save the current timestamp, since the user will need it */
6576 save_timestamp = cpu_buffer->read_stamp;
6577
6578 /* Need to copy one event at a time */
6579 do {
6580 /* We need the size of one event, because
6581 * rb_advance_reader only advances by one event,
6582 * whereas rb_event_ts_length may include the size of
6583 * one or two events.
6584 * We have already ensured there's enough space if this
6585 * is a time extend. */
6586 size = rb_event_length(event);
6587 memcpy(bpage->data + pos, rpage->data + rpos, size);
6588
6589 len -= size;
6590
6591 rb_advance_reader(cpu_buffer);
6592 rpos = reader->read;
6593 pos += size;
6594
6595 if (rpos >= commit)
6596 break;
6597
6598 event = rb_reader_event(cpu_buffer);
6599 /* Always keep the time extend and data together */
6600 size = rb_event_ts_length(event);
6601 } while (len >= size);
6602
6603 /* update bpage */
6604 local_set(&bpage->commit, pos);
6605 bpage->time_stamp = save_timestamp;
6606
6607 /* we copied everything to the beginning */
6608 read = 0;
6609 } else {
6610 /* update the entry counter */
6611 cpu_buffer->read += rb_page_entries(reader);
6612 cpu_buffer->read_bytes += rb_page_size(reader);
6613
6614 /* swap the pages */
6615 rb_init_page(bpage);
6616 bpage = reader->page;
6617 reader->page = data_page->data;
6618 local_set(&reader->write, 0);
6619 local_set(&reader->entries, 0);
6620 reader->read = 0;
6621 data_page->data = bpage;
6622
6623 /*
6624 * Use the real_end for the data size,
6625 * This gives us a chance to store the lost events
6626 * on the page.
6627 */
6628 if (reader->real_end)
6629 local_set(&bpage->commit, reader->real_end);
6630 }
6631 ret = read;
6632
6633 cpu_buffer->lost_events = 0;
6634
6635 commit = local_read(&bpage->commit);
6636 /*
6637 * Set a flag in the commit field if we lost events
6638 */
6639 if (missed_events) {
6640 /* If there is room at the end of the page to save the
6641 * missed events, then record it there.
6642 */
6643 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
6644 memcpy(&bpage->data[commit], &missed_events,
6645 sizeof(missed_events));
6646 local_add(RB_MISSED_STORED, &bpage->commit);
6647 commit += sizeof(missed_events);
6648 }
6649 local_add(RB_MISSED_EVENTS, &bpage->commit);
6650 }
6651
6652 /*
6653 * This page may be off to user land. Zero it out here.
6654 */
6655 if (commit < buffer->subbuf_size)
6656 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
6657
6658 out_unlock:
6659 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6660
6661 out:
6662 return ret;
6663}
6664EXPORT_SYMBOL_GPL(ring_buffer_read_page);
6665
6666/**
6667 * ring_buffer_read_page_data - get pointer to the data in the page.
6668 * @page: the page to get the data from
6669 *
6670 * Returns pointer to the actual data in this page.
6671 */
6672void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
6673{
6674 return page->data;
6675}
6676EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
6677
6678/**
6679 * ring_buffer_subbuf_size_get - get size of the sub buffer.
6680 * @buffer: the buffer to get the sub buffer size from
6681 *
6682 * Returns size of the sub buffer, in bytes.
6683 */
6684int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
6685{
6686 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6687}
6688EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
6689
6690/**
6691 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
6692 * @buffer: The ring_buffer to get the system sub page order from
6693 *
6694 * By default, one ring buffer sub page equals to one system page. This parameter
6695 * is configurable, per ring buffer. The size of the ring buffer sub page can be
6696 * extended, but must be an order of system page size.
6697 *
6698 * Returns the order of buffer sub page size, in system pages:
6699 * 0 means the sub buffer size is 1 system page and so forth.
6700 * In case of an error < 0 is returned.
6701 */
6702int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
6703{
6704 if (!buffer)
6705 return -EINVAL;
6706
6707 return buffer->subbuf_order;
6708}
6709EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
6710
6711/**
6712 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
6713 * @buffer: The ring_buffer to set the new page size.
6714 * @order: Order of the system pages in one sub buffer page
6715 *
6716 * By default, one ring buffer pages equals to one system page. This API can be
6717 * used to set new size of the ring buffer page. The size must be order of
6718 * system page size, that's why the input parameter @order is the order of
6719 * system pages that are allocated for one ring buffer page:
6720 * 0 - 1 system page
6721 * 1 - 2 system pages
6722 * 3 - 4 system pages
6723 * ...
6724 *
6725 * Returns 0 on success or < 0 in case of an error.
6726 */
6727int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
6728{
6729 struct ring_buffer_per_cpu *cpu_buffer;
6730 struct buffer_page *bpage, *tmp;
6731 int old_order, old_size;
6732 int nr_pages;
6733 int psize;
6734 int err;
6735 int cpu;
6736
6737 if (!buffer || order < 0)
6738 return -EINVAL;
6739
6740 if (buffer->subbuf_order == order)
6741 return 0;
6742
6743 psize = (1 << order) * PAGE_SIZE;
6744 if (psize <= BUF_PAGE_HDR_SIZE)
6745 return -EINVAL;
6746
6747 /* Size of a subbuf cannot be greater than the write counter */
6748 if (psize > RB_WRITE_MASK + 1)
6749 return -EINVAL;
6750
6751 old_order = buffer->subbuf_order;
6752 old_size = buffer->subbuf_size;
6753
6754 /* prevent another thread from changing buffer sizes */
6755 mutex_lock(&buffer->mutex);
6756 atomic_inc(&buffer->record_disabled);
6757
6758 /* Make sure all commits have finished */
6759 synchronize_rcu();
6760
6761 buffer->subbuf_order = order;
6762 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
6763
6764 /* Make sure all new buffers are allocated, before deleting the old ones */
6765 for_each_buffer_cpu(buffer, cpu) {
6766
6767 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6768 continue;
6769
6770 cpu_buffer = buffer->buffers[cpu];
6771
6772 if (cpu_buffer->mapped) {
6773 err = -EBUSY;
6774 goto error;
6775 }
6776
6777 /* Update the number of pages to match the new size */
6778 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
6779 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
6780
6781 /* we need a minimum of two pages */
6782 if (nr_pages < 2)
6783 nr_pages = 2;
6784
6785 cpu_buffer->nr_pages_to_update = nr_pages;
6786
6787 /* Include the reader page */
6788 nr_pages++;
6789
6790 /* Allocate the new size buffer */
6791 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6792 if (__rb_allocate_pages(cpu_buffer, nr_pages,
6793 &cpu_buffer->new_pages)) {
6794 /* not enough memory for new pages */
6795 err = -ENOMEM;
6796 goto error;
6797 }
6798 }
6799
6800 for_each_buffer_cpu(buffer, cpu) {
6801 struct buffer_data_page *old_free_data_page;
6802 struct list_head old_pages;
6803 unsigned long flags;
6804
6805 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6806 continue;
6807
6808 cpu_buffer = buffer->buffers[cpu];
6809
6810 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6811
6812 /* Clear the head bit to make the link list normal to read */
6813 rb_head_page_deactivate(cpu_buffer);
6814
6815 /*
6816 * Collect buffers from the cpu_buffer pages list and the
6817 * reader_page on old_pages, so they can be freed later when not
6818 * under a spinlock. The pages list is a linked list with no
6819 * head, adding old_pages turns it into a regular list with
6820 * old_pages being the head.
6821 */
6822 list_add(&old_pages, cpu_buffer->pages);
6823 list_add(&cpu_buffer->reader_page->list, &old_pages);
6824
6825 /* One page was allocated for the reader page */
6826 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6827 struct buffer_page, list);
6828 list_del_init(&cpu_buffer->reader_page->list);
6829
6830 /* Install the new pages, remove the head from the list */
6831 cpu_buffer->pages = cpu_buffer->new_pages.next;
6832 list_del_init(&cpu_buffer->new_pages);
6833 cpu_buffer->cnt++;
6834
6835 cpu_buffer->head_page
6836 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6837 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6838
6839 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6840 cpu_buffer->nr_pages_to_update = 0;
6841
6842 old_free_data_page = cpu_buffer->free_page;
6843 cpu_buffer->free_page = NULL;
6844
6845 rb_head_page_activate(cpu_buffer);
6846
6847 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6848
6849 /* Free old sub buffers */
6850 list_for_each_entry_safe(bpage, tmp, &old_pages, list) {
6851 list_del_init(&bpage->list);
6852 free_buffer_page(bpage);
6853 }
6854 free_pages((unsigned long)old_free_data_page, old_order);
6855
6856 rb_check_pages(cpu_buffer);
6857 }
6858
6859 atomic_dec(&buffer->record_disabled);
6860 mutex_unlock(&buffer->mutex);
6861
6862 return 0;
6863
6864error:
6865 buffer->subbuf_order = old_order;
6866 buffer->subbuf_size = old_size;
6867
6868 atomic_dec(&buffer->record_disabled);
6869 mutex_unlock(&buffer->mutex);
6870
6871 for_each_buffer_cpu(buffer, cpu) {
6872 cpu_buffer = buffer->buffers[cpu];
6873
6874 if (!cpu_buffer->nr_pages_to_update)
6875 continue;
6876
6877 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6878 list_del_init(&bpage->list);
6879 free_buffer_page(bpage);
6880 }
6881 }
6882
6883 return err;
6884}
6885EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6886
6887static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6888{
6889 struct page *page;
6890
6891 if (cpu_buffer->meta_page)
6892 return 0;
6893
6894 page = alloc_page(GFP_USER | __GFP_ZERO);
6895 if (!page)
6896 return -ENOMEM;
6897
6898 cpu_buffer->meta_page = page_to_virt(page);
6899
6900 return 0;
6901}
6902
6903static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6904{
6905 unsigned long addr = (unsigned long)cpu_buffer->meta_page;
6906
6907 free_page(addr);
6908 cpu_buffer->meta_page = NULL;
6909}
6910
6911static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer,
6912 unsigned long *subbuf_ids)
6913{
6914 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
6915 unsigned int nr_subbufs = cpu_buffer->nr_pages + 1;
6916 struct buffer_page *first_subbuf, *subbuf;
6917 int id = 0;
6918
6919 subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page;
6920 cpu_buffer->reader_page->id = id++;
6921
6922 first_subbuf = subbuf = rb_set_head_page(cpu_buffer);
6923 do {
6924 if (WARN_ON(id >= nr_subbufs))
6925 break;
6926
6927 subbuf_ids[id] = (unsigned long)subbuf->page;
6928 subbuf->id = id;
6929
6930 rb_inc_page(&subbuf);
6931 id++;
6932 } while (subbuf != first_subbuf);
6933
6934 /* install subbuf ID to kern VA translation */
6935 cpu_buffer->subbuf_ids = subbuf_ids;
6936
6937 meta->meta_struct_len = sizeof(*meta);
6938 meta->nr_subbufs = nr_subbufs;
6939 meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6940 meta->meta_page_size = meta->subbuf_size;
6941
6942 rb_update_meta_page(cpu_buffer);
6943}
6944
6945static struct ring_buffer_per_cpu *
6946rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
6947{
6948 struct ring_buffer_per_cpu *cpu_buffer;
6949
6950 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6951 return ERR_PTR(-EINVAL);
6952
6953 cpu_buffer = buffer->buffers[cpu];
6954
6955 mutex_lock(&cpu_buffer->mapping_lock);
6956
6957 if (!cpu_buffer->user_mapped) {
6958 mutex_unlock(&cpu_buffer->mapping_lock);
6959 return ERR_PTR(-ENODEV);
6960 }
6961
6962 return cpu_buffer;
6963}
6964
6965static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6966{
6967 mutex_unlock(&cpu_buffer->mapping_lock);
6968}
6969
6970/*
6971 * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need
6972 * to be set-up or torn-down.
6973 */
6974static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
6975 bool inc)
6976{
6977 unsigned long flags;
6978
6979 lockdep_assert_held(&cpu_buffer->mapping_lock);
6980
6981 /* mapped is always greater or equal to user_mapped */
6982 if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped))
6983 return -EINVAL;
6984
6985 if (inc && cpu_buffer->mapped == UINT_MAX)
6986 return -EBUSY;
6987
6988 if (WARN_ON(!inc && cpu_buffer->user_mapped == 0))
6989 return -EINVAL;
6990
6991 mutex_lock(&cpu_buffer->buffer->mutex);
6992 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6993
6994 if (inc) {
6995 cpu_buffer->user_mapped++;
6996 cpu_buffer->mapped++;
6997 } else {
6998 cpu_buffer->user_mapped--;
6999 cpu_buffer->mapped--;
7000 }
7001
7002 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7003 mutex_unlock(&cpu_buffer->buffer->mutex);
7004
7005 return 0;
7006}
7007
7008/*
7009 * +--------------+ pgoff == 0
7010 * | meta page |
7011 * +--------------+ pgoff == 1
7012 * | subbuffer 0 |
7013 * | |
7014 * +--------------+ pgoff == (1 + (1 << subbuf_order))
7015 * | subbuffer 1 |
7016 * | |
7017 * ...
7018 */
7019#ifdef CONFIG_MMU
7020static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
7021 struct vm_area_struct *vma)
7022{
7023 unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
7024 unsigned int subbuf_pages, subbuf_order;
7025 struct page **pages;
7026 int p = 0, s = 0;
7027 int err;
7028
7029 /* Refuse MP_PRIVATE or writable mappings */
7030 if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
7031 !(vma->vm_flags & VM_MAYSHARE))
7032 return -EPERM;
7033
7034 subbuf_order = cpu_buffer->buffer->subbuf_order;
7035 subbuf_pages = 1 << subbuf_order;
7036
7037 if (subbuf_order && pgoff % subbuf_pages)
7038 return -EINVAL;
7039
7040 /*
7041 * Make sure the mapping cannot become writable later. Also tell the VM
7042 * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
7043 */
7044 vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
7045 VM_MAYWRITE);
7046
7047 lockdep_assert_held(&cpu_buffer->mapping_lock);
7048
7049 nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
7050 nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */
7051 if (nr_pages <= pgoff)
7052 return -EINVAL;
7053
7054 nr_pages -= pgoff;
7055
7056 nr_vma_pages = vma_pages(vma);
7057 if (!nr_vma_pages || nr_vma_pages > nr_pages)
7058 return -EINVAL;
7059
7060 nr_pages = nr_vma_pages;
7061
7062 pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
7063 if (!pages)
7064 return -ENOMEM;
7065
7066 if (!pgoff) {
7067 unsigned long meta_page_padding;
7068
7069 pages[p++] = virt_to_page(cpu_buffer->meta_page);
7070
7071 /*
7072 * Pad with the zero-page to align the meta-page with the
7073 * sub-buffers.
7074 */
7075 meta_page_padding = subbuf_pages - 1;
7076 while (meta_page_padding-- && p < nr_pages) {
7077 unsigned long __maybe_unused zero_addr =
7078 vma->vm_start + (PAGE_SIZE * p);
7079
7080 pages[p++] = ZERO_PAGE(zero_addr);
7081 }
7082 } else {
7083 /* Skip the meta-page */
7084 pgoff -= subbuf_pages;
7085
7086 s += pgoff / subbuf_pages;
7087 }
7088
7089 while (p < nr_pages) {
7090 struct page *page;
7091 int off = 0;
7092
7093 if (WARN_ON_ONCE(s >= nr_subbufs)) {
7094 err = -EINVAL;
7095 goto out;
7096 }
7097
7098 page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
7099
7100 for (; off < (1 << (subbuf_order)); off++, page++) {
7101 if (p >= nr_pages)
7102 break;
7103
7104 pages[p++] = page;
7105 }
7106 s++;
7107 }
7108
7109 err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
7110
7111out:
7112 kfree(pages);
7113
7114 return err;
7115}
7116#else
7117static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
7118 struct vm_area_struct *vma)
7119{
7120 return -EOPNOTSUPP;
7121}
7122#endif
7123
7124int ring_buffer_map(struct trace_buffer *buffer, int cpu,
7125 struct vm_area_struct *vma)
7126{
7127 struct ring_buffer_per_cpu *cpu_buffer;
7128 unsigned long flags, *subbuf_ids;
7129 int err = 0;
7130
7131 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7132 return -EINVAL;
7133
7134 cpu_buffer = buffer->buffers[cpu];
7135
7136 mutex_lock(&cpu_buffer->mapping_lock);
7137
7138 if (cpu_buffer->user_mapped) {
7139 err = __rb_map_vma(cpu_buffer, vma);
7140 if (!err)
7141 err = __rb_inc_dec_mapped(cpu_buffer, true);
7142 mutex_unlock(&cpu_buffer->mapping_lock);
7143 return err;
7144 }
7145
7146 /* prevent another thread from changing buffer/sub-buffer sizes */
7147 mutex_lock(&buffer->mutex);
7148
7149 err = rb_alloc_meta_page(cpu_buffer);
7150 if (err)
7151 goto unlock;
7152
7153 /* subbuf_ids include the reader while nr_pages does not */
7154 subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL);
7155 if (!subbuf_ids) {
7156 rb_free_meta_page(cpu_buffer);
7157 err = -ENOMEM;
7158 goto unlock;
7159 }
7160
7161 atomic_inc(&cpu_buffer->resize_disabled);
7162
7163 /*
7164 * Lock all readers to block any subbuf swap until the subbuf IDs are
7165 * assigned.
7166 */
7167 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7168 rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
7169
7170 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7171
7172 err = __rb_map_vma(cpu_buffer, vma);
7173 if (!err) {
7174 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7175 /* This is the first time it is mapped by user */
7176 cpu_buffer->mapped++;
7177 cpu_buffer->user_mapped = 1;
7178 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7179 } else {
7180 kfree(cpu_buffer->subbuf_ids);
7181 cpu_buffer->subbuf_ids = NULL;
7182 rb_free_meta_page(cpu_buffer);
7183 atomic_dec(&cpu_buffer->resize_disabled);
7184 }
7185
7186unlock:
7187 mutex_unlock(&buffer->mutex);
7188 mutex_unlock(&cpu_buffer->mapping_lock);
7189
7190 return err;
7191}
7192
7193int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
7194{
7195 struct ring_buffer_per_cpu *cpu_buffer;
7196 unsigned long flags;
7197 int err = 0;
7198
7199 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7200 return -EINVAL;
7201
7202 cpu_buffer = buffer->buffers[cpu];
7203
7204 mutex_lock(&cpu_buffer->mapping_lock);
7205
7206 if (!cpu_buffer->user_mapped) {
7207 err = -ENODEV;
7208 goto out;
7209 } else if (cpu_buffer->user_mapped > 1) {
7210 __rb_inc_dec_mapped(cpu_buffer, false);
7211 goto out;
7212 }
7213
7214 mutex_lock(&buffer->mutex);
7215 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7216
7217 /* This is the last user space mapping */
7218 if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped))
7219 cpu_buffer->mapped--;
7220 cpu_buffer->user_mapped = 0;
7221
7222 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7223
7224 kfree(cpu_buffer->subbuf_ids);
7225 cpu_buffer->subbuf_ids = NULL;
7226 rb_free_meta_page(cpu_buffer);
7227 atomic_dec(&cpu_buffer->resize_disabled);
7228
7229 mutex_unlock(&buffer->mutex);
7230
7231out:
7232 mutex_unlock(&cpu_buffer->mapping_lock);
7233
7234 return err;
7235}
7236
7237int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
7238{
7239 struct ring_buffer_per_cpu *cpu_buffer;
7240 struct buffer_page *reader;
7241 unsigned long missed_events;
7242 unsigned long reader_size;
7243 unsigned long flags;
7244
7245 cpu_buffer = rb_get_mapped_buffer(buffer, cpu);
7246 if (IS_ERR(cpu_buffer))
7247 return (int)PTR_ERR(cpu_buffer);
7248
7249 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7250
7251consume:
7252 if (rb_per_cpu_empty(cpu_buffer))
7253 goto out;
7254
7255 reader_size = rb_page_size(cpu_buffer->reader_page);
7256
7257 /*
7258 * There are data to be read on the current reader page, we can
7259 * return to the caller. But before that, we assume the latter will read
7260 * everything. Let's update the kernel reader accordingly.
7261 */
7262 if (cpu_buffer->reader_page->read < reader_size) {
7263 while (cpu_buffer->reader_page->read < reader_size)
7264 rb_advance_reader(cpu_buffer);
7265 goto out;
7266 }
7267
7268 reader = rb_get_reader_page(cpu_buffer);
7269 if (WARN_ON(!reader))
7270 goto out;
7271
7272 /* Check if any events were dropped */
7273 missed_events = cpu_buffer->lost_events;
7274
7275 if (cpu_buffer->reader_page != cpu_buffer->commit_page) {
7276 if (missed_events) {
7277 struct buffer_data_page *bpage = reader->page;
7278 unsigned int commit;
7279 /*
7280 * Use the real_end for the data size,
7281 * This gives us a chance to store the lost events
7282 * on the page.
7283 */
7284 if (reader->real_end)
7285 local_set(&bpage->commit, reader->real_end);
7286 /*
7287 * If there is room at the end of the page to save the
7288 * missed events, then record it there.
7289 */
7290 commit = rb_page_size(reader);
7291 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
7292 memcpy(&bpage->data[commit], &missed_events,
7293 sizeof(missed_events));
7294 local_add(RB_MISSED_STORED, &bpage->commit);
7295 }
7296 local_add(RB_MISSED_EVENTS, &bpage->commit);
7297 }
7298 } else {
7299 /*
7300 * There really shouldn't be any missed events if the commit
7301 * is on the reader page.
7302 */
7303 WARN_ON_ONCE(missed_events);
7304 }
7305
7306 cpu_buffer->lost_events = 0;
7307
7308 goto consume;
7309
7310out:
7311 /* Some archs do not have data cache coherency between kernel and user-space */
7312 flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page));
7313
7314 rb_update_meta_page(cpu_buffer);
7315
7316 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7317 rb_put_mapped_buffer(cpu_buffer);
7318
7319 return 0;
7320}
7321
7322/*
7323 * We only allocate new buffers, never free them if the CPU goes down.
7324 * If we were to free the buffer, then the user would lose any trace that was in
7325 * the buffer.
7326 */
7327int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
7328{
7329 struct trace_buffer *buffer;
7330 long nr_pages_same;
7331 int cpu_i;
7332 unsigned long nr_pages;
7333
7334 buffer = container_of(node, struct trace_buffer, node);
7335 if (cpumask_test_cpu(cpu, buffer->cpumask))
7336 return 0;
7337
7338 nr_pages = 0;
7339 nr_pages_same = 1;
7340 /* check if all cpu sizes are same */
7341 for_each_buffer_cpu(buffer, cpu_i) {
7342 /* fill in the size from first enabled cpu */
7343 if (nr_pages == 0)
7344 nr_pages = buffer->buffers[cpu_i]->nr_pages;
7345 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
7346 nr_pages_same = 0;
7347 break;
7348 }
7349 }
7350 /* allocate minimum pages, user can later expand it */
7351 if (!nr_pages_same)
7352 nr_pages = 2;
7353 buffer->buffers[cpu] =
7354 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
7355 if (!buffer->buffers[cpu]) {
7356 WARN(1, "failed to allocate ring buffer on CPU %u\n",
7357 cpu);
7358 return -ENOMEM;
7359 }
7360 smp_wmb();
7361 cpumask_set_cpu(cpu, buffer->cpumask);
7362 return 0;
7363}
7364
7365#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
7366/*
7367 * This is a basic integrity check of the ring buffer.
7368 * Late in the boot cycle this test will run when configured in.
7369 * It will kick off a thread per CPU that will go into a loop
7370 * writing to the per cpu ring buffer various sizes of data.
7371 * Some of the data will be large items, some small.
7372 *
7373 * Another thread is created that goes into a spin, sending out
7374 * IPIs to the other CPUs to also write into the ring buffer.
7375 * this is to test the nesting ability of the buffer.
7376 *
7377 * Basic stats are recorded and reported. If something in the
7378 * ring buffer should happen that's not expected, a big warning
7379 * is displayed and all ring buffers are disabled.
7380 */
7381static struct task_struct *rb_threads[NR_CPUS] __initdata;
7382
7383struct rb_test_data {
7384 struct trace_buffer *buffer;
7385 unsigned long events;
7386 unsigned long bytes_written;
7387 unsigned long bytes_alloc;
7388 unsigned long bytes_dropped;
7389 unsigned long events_nested;
7390 unsigned long bytes_written_nested;
7391 unsigned long bytes_alloc_nested;
7392 unsigned long bytes_dropped_nested;
7393 int min_size_nested;
7394 int max_size_nested;
7395 int max_size;
7396 int min_size;
7397 int cpu;
7398 int cnt;
7399};
7400
7401static struct rb_test_data rb_data[NR_CPUS] __initdata;
7402
7403/* 1 meg per cpu */
7404#define RB_TEST_BUFFER_SIZE 1048576
7405
7406static char rb_string[] __initdata =
7407 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
7408 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
7409 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
7410
7411static bool rb_test_started __initdata;
7412
7413struct rb_item {
7414 int size;
7415 char str[];
7416};
7417
7418static __init int rb_write_something(struct rb_test_data *data, bool nested)
7419{
7420 struct ring_buffer_event *event;
7421 struct rb_item *item;
7422 bool started;
7423 int event_len;
7424 int size;
7425 int len;
7426 int cnt;
7427
7428 /* Have nested writes different that what is written */
7429 cnt = data->cnt + (nested ? 27 : 0);
7430
7431 /* Multiply cnt by ~e, to make some unique increment */
7432 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
7433
7434 len = size + sizeof(struct rb_item);
7435
7436 started = rb_test_started;
7437 /* read rb_test_started before checking buffer enabled */
7438 smp_rmb();
7439
7440 event = ring_buffer_lock_reserve(data->buffer, len);
7441 if (!event) {
7442 /* Ignore dropped events before test starts. */
7443 if (started) {
7444 if (nested)
7445 data->bytes_dropped += len;
7446 else
7447 data->bytes_dropped_nested += len;
7448 }
7449 return len;
7450 }
7451
7452 event_len = ring_buffer_event_length(event);
7453
7454 if (RB_WARN_ON(data->buffer, event_len < len))
7455 goto out;
7456
7457 item = ring_buffer_event_data(event);
7458 item->size = size;
7459 memcpy(item->str, rb_string, size);
7460
7461 if (nested) {
7462 data->bytes_alloc_nested += event_len;
7463 data->bytes_written_nested += len;
7464 data->events_nested++;
7465 if (!data->min_size_nested || len < data->min_size_nested)
7466 data->min_size_nested = len;
7467 if (len > data->max_size_nested)
7468 data->max_size_nested = len;
7469 } else {
7470 data->bytes_alloc += event_len;
7471 data->bytes_written += len;
7472 data->events++;
7473 if (!data->min_size || len < data->min_size)
7474 data->max_size = len;
7475 if (len > data->max_size)
7476 data->max_size = len;
7477 }
7478
7479 out:
7480 ring_buffer_unlock_commit(data->buffer);
7481
7482 return 0;
7483}
7484
7485static __init int rb_test(void *arg)
7486{
7487 struct rb_test_data *data = arg;
7488
7489 while (!kthread_should_stop()) {
7490 rb_write_something(data, false);
7491 data->cnt++;
7492
7493 set_current_state(TASK_INTERRUPTIBLE);
7494 /* Now sleep between a min of 100-300us and a max of 1ms */
7495 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
7496 }
7497
7498 return 0;
7499}
7500
7501static __init void rb_ipi(void *ignore)
7502{
7503 struct rb_test_data *data;
7504 int cpu = smp_processor_id();
7505
7506 data = &rb_data[cpu];
7507 rb_write_something(data, true);
7508}
7509
7510static __init int rb_hammer_test(void *arg)
7511{
7512 while (!kthread_should_stop()) {
7513
7514 /* Send an IPI to all cpus to write data! */
7515 smp_call_function(rb_ipi, NULL, 1);
7516 /* No sleep, but for non preempt, let others run */
7517 schedule();
7518 }
7519
7520 return 0;
7521}
7522
7523static __init int test_ringbuffer(void)
7524{
7525 struct task_struct *rb_hammer;
7526 struct trace_buffer *buffer;
7527 int cpu;
7528 int ret = 0;
7529
7530 if (security_locked_down(LOCKDOWN_TRACEFS)) {
7531 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
7532 return 0;
7533 }
7534
7535 pr_info("Running ring buffer tests...\n");
7536
7537 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
7538 if (WARN_ON(!buffer))
7539 return 0;
7540
7541 /* Disable buffer so that threads can't write to it yet */
7542 ring_buffer_record_off(buffer);
7543
7544 for_each_online_cpu(cpu) {
7545 rb_data[cpu].buffer = buffer;
7546 rb_data[cpu].cpu = cpu;
7547 rb_data[cpu].cnt = cpu;
7548 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
7549 cpu, "rbtester/%u");
7550 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
7551 pr_cont("FAILED\n");
7552 ret = PTR_ERR(rb_threads[cpu]);
7553 goto out_free;
7554 }
7555 }
7556
7557 /* Now create the rb hammer! */
7558 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
7559 if (WARN_ON(IS_ERR(rb_hammer))) {
7560 pr_cont("FAILED\n");
7561 ret = PTR_ERR(rb_hammer);
7562 goto out_free;
7563 }
7564
7565 ring_buffer_record_on(buffer);
7566 /*
7567 * Show buffer is enabled before setting rb_test_started.
7568 * Yes there's a small race window where events could be
7569 * dropped and the thread wont catch it. But when a ring
7570 * buffer gets enabled, there will always be some kind of
7571 * delay before other CPUs see it. Thus, we don't care about
7572 * those dropped events. We care about events dropped after
7573 * the threads see that the buffer is active.
7574 */
7575 smp_wmb();
7576 rb_test_started = true;
7577
7578 set_current_state(TASK_INTERRUPTIBLE);
7579 /* Just run for 10 seconds */;
7580 schedule_timeout(10 * HZ);
7581
7582 kthread_stop(rb_hammer);
7583
7584 out_free:
7585 for_each_online_cpu(cpu) {
7586 if (!rb_threads[cpu])
7587 break;
7588 kthread_stop(rb_threads[cpu]);
7589 }
7590 if (ret) {
7591 ring_buffer_free(buffer);
7592 return ret;
7593 }
7594
7595 /* Report! */
7596 pr_info("finished\n");
7597 for_each_online_cpu(cpu) {
7598 struct ring_buffer_event *event;
7599 struct rb_test_data *data = &rb_data[cpu];
7600 struct rb_item *item;
7601 unsigned long total_events;
7602 unsigned long total_dropped;
7603 unsigned long total_written;
7604 unsigned long total_alloc;
7605 unsigned long total_read = 0;
7606 unsigned long total_size = 0;
7607 unsigned long total_len = 0;
7608 unsigned long total_lost = 0;
7609 unsigned long lost;
7610 int big_event_size;
7611 int small_event_size;
7612
7613 ret = -1;
7614
7615 total_events = data->events + data->events_nested;
7616 total_written = data->bytes_written + data->bytes_written_nested;
7617 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
7618 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
7619
7620 big_event_size = data->max_size + data->max_size_nested;
7621 small_event_size = data->min_size + data->min_size_nested;
7622
7623 pr_info("CPU %d:\n", cpu);
7624 pr_info(" events: %ld\n", total_events);
7625 pr_info(" dropped bytes: %ld\n", total_dropped);
7626 pr_info(" alloced bytes: %ld\n", total_alloc);
7627 pr_info(" written bytes: %ld\n", total_written);
7628 pr_info(" biggest event: %d\n", big_event_size);
7629 pr_info(" smallest event: %d\n", small_event_size);
7630
7631 if (RB_WARN_ON(buffer, total_dropped))
7632 break;
7633
7634 ret = 0;
7635
7636 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
7637 total_lost += lost;
7638 item = ring_buffer_event_data(event);
7639 total_len += ring_buffer_event_length(event);
7640 total_size += item->size + sizeof(struct rb_item);
7641 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
7642 pr_info("FAILED!\n");
7643 pr_info("buffer had: %.*s\n", item->size, item->str);
7644 pr_info("expected: %.*s\n", item->size, rb_string);
7645 RB_WARN_ON(buffer, 1);
7646 ret = -1;
7647 break;
7648 }
7649 total_read++;
7650 }
7651 if (ret)
7652 break;
7653
7654 ret = -1;
7655
7656 pr_info(" read events: %ld\n", total_read);
7657 pr_info(" lost events: %ld\n", total_lost);
7658 pr_info(" total events: %ld\n", total_lost + total_read);
7659 pr_info(" recorded len bytes: %ld\n", total_len);
7660 pr_info(" recorded size bytes: %ld\n", total_size);
7661 if (total_lost) {
7662 pr_info(" With dropped events, record len and size may not match\n"
7663 " alloced and written from above\n");
7664 } else {
7665 if (RB_WARN_ON(buffer, total_len != total_alloc ||
7666 total_size != total_written))
7667 break;
7668 }
7669 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
7670 break;
7671
7672 ret = 0;
7673 }
7674 if (!ret)
7675 pr_info("Ring buffer PASSED!\n");
7676
7677 ring_buffer_free(buffer);
7678 return 0;
7679}
7680
7681late_initcall(test_ringbuffer);
7682#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Generic ring buffer
4 *
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 */
7#include <linux/trace_recursion.h>
8#include <linux/trace_events.h>
9#include <linux/ring_buffer.h>
10#include <linux/trace_clock.h>
11#include <linux/sched/clock.h>
12#include <linux/trace_seq.h>
13#include <linux/spinlock.h>
14#include <linux/irq_work.h>
15#include <linux/security.h>
16#include <linux/uaccess.h>
17#include <linux/hardirq.h>
18#include <linux/kthread.h> /* for self test */
19#include <linux/module.h>
20#include <linux/percpu.h>
21#include <linux/mutex.h>
22#include <linux/delay.h>
23#include <linux/slab.h>
24#include <linux/init.h>
25#include <linux/hash.h>
26#include <linux/list.h>
27#include <linux/cpu.h>
28#include <linux/oom.h>
29
30#include <asm/local64.h>
31#include <asm/local.h>
32
33/*
34 * The "absolute" timestamp in the buffer is only 59 bits.
35 * If a clock has the 5 MSBs set, it needs to be saved and
36 * reinserted.
37 */
38#define TS_MSB (0xf8ULL << 56)
39#define ABS_TS_MASK (~TS_MSB)
40
41static void update_pages_handler(struct work_struct *work);
42
43/*
44 * The ring buffer header is special. We must manually up keep it.
45 */
46int ring_buffer_print_entry_header(struct trace_seq *s)
47{
48 trace_seq_puts(s, "# compressed entry header\n");
49 trace_seq_puts(s, "\ttype_len : 5 bits\n");
50 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
51 trace_seq_puts(s, "\tarray : 32 bits\n");
52 trace_seq_putc(s, '\n');
53 trace_seq_printf(s, "\tpadding : type == %d\n",
54 RINGBUF_TYPE_PADDING);
55 trace_seq_printf(s, "\ttime_extend : type == %d\n",
56 RINGBUF_TYPE_TIME_EXTEND);
57 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
58 RINGBUF_TYPE_TIME_STAMP);
59 trace_seq_printf(s, "\tdata max type_len == %d\n",
60 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
61
62 return !trace_seq_has_overflowed(s);
63}
64
65/*
66 * The ring buffer is made up of a list of pages. A separate list of pages is
67 * allocated for each CPU. A writer may only write to a buffer that is
68 * associated with the CPU it is currently executing on. A reader may read
69 * from any per cpu buffer.
70 *
71 * The reader is special. For each per cpu buffer, the reader has its own
72 * reader page. When a reader has read the entire reader page, this reader
73 * page is swapped with another page in the ring buffer.
74 *
75 * Now, as long as the writer is off the reader page, the reader can do what
76 * ever it wants with that page. The writer will never write to that page
77 * again (as long as it is out of the ring buffer).
78 *
79 * Here's some silly ASCII art.
80 *
81 * +------+
82 * |reader| RING BUFFER
83 * |page |
84 * +------+ +---+ +---+ +---+
85 * | |-->| |-->| |
86 * +---+ +---+ +---+
87 * ^ |
88 * | |
89 * +---------------+
90 *
91 *
92 * +------+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
96 * | |-->| |-->| |
97 * +---+ +---+ +---+
98 * ^ |
99 * | |
100 * +---------------+
101 *
102 *
103 * +------+
104 * |reader| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
107 * ^ | |-->| |-->| |
108 * | +---+ +---+ +---+
109 * | |
110 * | |
111 * +------------------------------+
112 *
113 *
114 * +------+
115 * |buffer| RING BUFFER
116 * |page |------------------v
117 * +------+ +---+ +---+ +---+
118 * ^ | | | |-->| |
119 * | New +---+ +---+ +---+
120 * | Reader------^ |
121 * | page |
122 * +------------------------------+
123 *
124 *
125 * After we make this swap, the reader can hand this page off to the splice
126 * code and be done with it. It can even allocate a new page if it needs to
127 * and swap that into the ring buffer.
128 *
129 * We will be using cmpxchg soon to make all this lockless.
130 *
131 */
132
133/* Used for individual buffers (after the counter) */
134#define RB_BUFFER_OFF (1 << 20)
135
136#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
137
138#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
139#define RB_ALIGNMENT 4U
140#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
141#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
142
143#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
144# define RB_FORCE_8BYTE_ALIGNMENT 0
145# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
146#else
147# define RB_FORCE_8BYTE_ALIGNMENT 1
148# define RB_ARCH_ALIGNMENT 8U
149#endif
150
151#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
152
153/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
154#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
155
156enum {
157 RB_LEN_TIME_EXTEND = 8,
158 RB_LEN_TIME_STAMP = 8,
159};
160
161#define skip_time_extend(event) \
162 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
163
164#define extended_time(event) \
165 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
166
167static inline bool rb_null_event(struct ring_buffer_event *event)
168{
169 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
170}
171
172static void rb_event_set_padding(struct ring_buffer_event *event)
173{
174 /* padding has a NULL time_delta */
175 event->type_len = RINGBUF_TYPE_PADDING;
176 event->time_delta = 0;
177}
178
179static unsigned
180rb_event_data_length(struct ring_buffer_event *event)
181{
182 unsigned length;
183
184 if (event->type_len)
185 length = event->type_len * RB_ALIGNMENT;
186 else
187 length = event->array[0];
188 return length + RB_EVNT_HDR_SIZE;
189}
190
191/*
192 * Return the length of the given event. Will return
193 * the length of the time extend if the event is a
194 * time extend.
195 */
196static inline unsigned
197rb_event_length(struct ring_buffer_event *event)
198{
199 switch (event->type_len) {
200 case RINGBUF_TYPE_PADDING:
201 if (rb_null_event(event))
202 /* undefined */
203 return -1;
204 return event->array[0] + RB_EVNT_HDR_SIZE;
205
206 case RINGBUF_TYPE_TIME_EXTEND:
207 return RB_LEN_TIME_EXTEND;
208
209 case RINGBUF_TYPE_TIME_STAMP:
210 return RB_LEN_TIME_STAMP;
211
212 case RINGBUF_TYPE_DATA:
213 return rb_event_data_length(event);
214 default:
215 WARN_ON_ONCE(1);
216 }
217 /* not hit */
218 return 0;
219}
220
221/*
222 * Return total length of time extend and data,
223 * or just the event length for all other events.
224 */
225static inline unsigned
226rb_event_ts_length(struct ring_buffer_event *event)
227{
228 unsigned len = 0;
229
230 if (extended_time(event)) {
231 /* time extends include the data event after it */
232 len = RB_LEN_TIME_EXTEND;
233 event = skip_time_extend(event);
234 }
235 return len + rb_event_length(event);
236}
237
238/**
239 * ring_buffer_event_length - return the length of the event
240 * @event: the event to get the length of
241 *
242 * Returns the size of the data load of a data event.
243 * If the event is something other than a data event, it
244 * returns the size of the event itself. With the exception
245 * of a TIME EXTEND, where it still returns the size of the
246 * data load of the data event after it.
247 */
248unsigned ring_buffer_event_length(struct ring_buffer_event *event)
249{
250 unsigned length;
251
252 if (extended_time(event))
253 event = skip_time_extend(event);
254
255 length = rb_event_length(event);
256 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
257 return length;
258 length -= RB_EVNT_HDR_SIZE;
259 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
260 length -= sizeof(event->array[0]);
261 return length;
262}
263EXPORT_SYMBOL_GPL(ring_buffer_event_length);
264
265/* inline for ring buffer fast paths */
266static __always_inline void *
267rb_event_data(struct ring_buffer_event *event)
268{
269 if (extended_time(event))
270 event = skip_time_extend(event);
271 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
272 /* If length is in len field, then array[0] has the data */
273 if (event->type_len)
274 return (void *)&event->array[0];
275 /* Otherwise length is in array[0] and array[1] has the data */
276 return (void *)&event->array[1];
277}
278
279/**
280 * ring_buffer_event_data - return the data of the event
281 * @event: the event to get the data from
282 */
283void *ring_buffer_event_data(struct ring_buffer_event *event)
284{
285 return rb_event_data(event);
286}
287EXPORT_SYMBOL_GPL(ring_buffer_event_data);
288
289#define for_each_buffer_cpu(buffer, cpu) \
290 for_each_cpu(cpu, buffer->cpumask)
291
292#define for_each_online_buffer_cpu(buffer, cpu) \
293 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
294
295#define TS_SHIFT 27
296#define TS_MASK ((1ULL << TS_SHIFT) - 1)
297#define TS_DELTA_TEST (~TS_MASK)
298
299static u64 rb_event_time_stamp(struct ring_buffer_event *event)
300{
301 u64 ts;
302
303 ts = event->array[0];
304 ts <<= TS_SHIFT;
305 ts += event->time_delta;
306
307 return ts;
308}
309
310/* Flag when events were overwritten */
311#define RB_MISSED_EVENTS (1 << 31)
312/* Missed count stored at end */
313#define RB_MISSED_STORED (1 << 30)
314
315struct buffer_data_page {
316 u64 time_stamp; /* page time stamp */
317 local_t commit; /* write committed index */
318 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
319};
320
321struct buffer_data_read_page {
322 unsigned order; /* order of the page */
323 struct buffer_data_page *data; /* actual data, stored in this page */
324};
325
326/*
327 * Note, the buffer_page list must be first. The buffer pages
328 * are allocated in cache lines, which means that each buffer
329 * page will be at the beginning of a cache line, and thus
330 * the least significant bits will be zero. We use this to
331 * add flags in the list struct pointers, to make the ring buffer
332 * lockless.
333 */
334struct buffer_page {
335 struct list_head list; /* list of buffer pages */
336 local_t write; /* index for next write */
337 unsigned read; /* index for next read */
338 local_t entries; /* entries on this page */
339 unsigned long real_end; /* real end of data */
340 unsigned order; /* order of the page */
341 struct buffer_data_page *page; /* Actual data page */
342};
343
344/*
345 * The buffer page counters, write and entries, must be reset
346 * atomically when crossing page boundaries. To synchronize this
347 * update, two counters are inserted into the number. One is
348 * the actual counter for the write position or count on the page.
349 *
350 * The other is a counter of updaters. Before an update happens
351 * the update partition of the counter is incremented. This will
352 * allow the updater to update the counter atomically.
353 *
354 * The counter is 20 bits, and the state data is 12.
355 */
356#define RB_WRITE_MASK 0xfffff
357#define RB_WRITE_INTCNT (1 << 20)
358
359static void rb_init_page(struct buffer_data_page *bpage)
360{
361 local_set(&bpage->commit, 0);
362}
363
364static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
365{
366 return local_read(&bpage->page->commit);
367}
368
369static void free_buffer_page(struct buffer_page *bpage)
370{
371 free_pages((unsigned long)bpage->page, bpage->order);
372 kfree(bpage);
373}
374
375/*
376 * We need to fit the time_stamp delta into 27 bits.
377 */
378static inline bool test_time_stamp(u64 delta)
379{
380 return !!(delta & TS_DELTA_TEST);
381}
382
383struct rb_irq_work {
384 struct irq_work work;
385 wait_queue_head_t waiters;
386 wait_queue_head_t full_waiters;
387 atomic_t seq;
388 bool waiters_pending;
389 bool full_waiters_pending;
390 bool wakeup_full;
391};
392
393/*
394 * Structure to hold event state and handle nested events.
395 */
396struct rb_event_info {
397 u64 ts;
398 u64 delta;
399 u64 before;
400 u64 after;
401 unsigned long length;
402 struct buffer_page *tail_page;
403 int add_timestamp;
404};
405
406/*
407 * Used for the add_timestamp
408 * NONE
409 * EXTEND - wants a time extend
410 * ABSOLUTE - the buffer requests all events to have absolute time stamps
411 * FORCE - force a full time stamp.
412 */
413enum {
414 RB_ADD_STAMP_NONE = 0,
415 RB_ADD_STAMP_EXTEND = BIT(1),
416 RB_ADD_STAMP_ABSOLUTE = BIT(2),
417 RB_ADD_STAMP_FORCE = BIT(3)
418};
419/*
420 * Used for which event context the event is in.
421 * TRANSITION = 0
422 * NMI = 1
423 * IRQ = 2
424 * SOFTIRQ = 3
425 * NORMAL = 4
426 *
427 * See trace_recursive_lock() comment below for more details.
428 */
429enum {
430 RB_CTX_TRANSITION,
431 RB_CTX_NMI,
432 RB_CTX_IRQ,
433 RB_CTX_SOFTIRQ,
434 RB_CTX_NORMAL,
435 RB_CTX_MAX
436};
437
438struct rb_time_struct {
439 local64_t time;
440};
441typedef struct rb_time_struct rb_time_t;
442
443#define MAX_NEST 5
444
445/*
446 * head_page == tail_page && head == tail then buffer is empty.
447 */
448struct ring_buffer_per_cpu {
449 int cpu;
450 atomic_t record_disabled;
451 atomic_t resize_disabled;
452 struct trace_buffer *buffer;
453 raw_spinlock_t reader_lock; /* serialize readers */
454 arch_spinlock_t lock;
455 struct lock_class_key lock_key;
456 struct buffer_data_page *free_page;
457 unsigned long nr_pages;
458 unsigned int current_context;
459 struct list_head *pages;
460 struct buffer_page *head_page; /* read from head */
461 struct buffer_page *tail_page; /* write to tail */
462 struct buffer_page *commit_page; /* committed pages */
463 struct buffer_page *reader_page;
464 unsigned long lost_events;
465 unsigned long last_overrun;
466 unsigned long nest;
467 local_t entries_bytes;
468 local_t entries;
469 local_t overrun;
470 local_t commit_overrun;
471 local_t dropped_events;
472 local_t committing;
473 local_t commits;
474 local_t pages_touched;
475 local_t pages_lost;
476 local_t pages_read;
477 long last_pages_touch;
478 size_t shortest_full;
479 unsigned long read;
480 unsigned long read_bytes;
481 rb_time_t write_stamp;
482 rb_time_t before_stamp;
483 u64 event_stamp[MAX_NEST];
484 u64 read_stamp;
485 /* pages removed since last reset */
486 unsigned long pages_removed;
487 /* ring buffer pages to update, > 0 to add, < 0 to remove */
488 long nr_pages_to_update;
489 struct list_head new_pages; /* new pages to add */
490 struct work_struct update_pages_work;
491 struct completion update_done;
492
493 struct rb_irq_work irq_work;
494};
495
496struct trace_buffer {
497 unsigned flags;
498 int cpus;
499 atomic_t record_disabled;
500 atomic_t resizing;
501 cpumask_var_t cpumask;
502
503 struct lock_class_key *reader_lock_key;
504
505 struct mutex mutex;
506
507 struct ring_buffer_per_cpu **buffers;
508
509 struct hlist_node node;
510 u64 (*clock)(void);
511
512 struct rb_irq_work irq_work;
513 bool time_stamp_abs;
514
515 unsigned int subbuf_size;
516 unsigned int subbuf_order;
517 unsigned int max_data_size;
518};
519
520struct ring_buffer_iter {
521 struct ring_buffer_per_cpu *cpu_buffer;
522 unsigned long head;
523 unsigned long next_event;
524 struct buffer_page *head_page;
525 struct buffer_page *cache_reader_page;
526 unsigned long cache_read;
527 unsigned long cache_pages_removed;
528 u64 read_stamp;
529 u64 page_stamp;
530 struct ring_buffer_event *event;
531 size_t event_size;
532 int missed_events;
533};
534
535int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
536{
537 struct buffer_data_page field;
538
539 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
540 "offset:0;\tsize:%u;\tsigned:%u;\n",
541 (unsigned int)sizeof(field.time_stamp),
542 (unsigned int)is_signed_type(u64));
543
544 trace_seq_printf(s, "\tfield: local_t commit;\t"
545 "offset:%u;\tsize:%u;\tsigned:%u;\n",
546 (unsigned int)offsetof(typeof(field), commit),
547 (unsigned int)sizeof(field.commit),
548 (unsigned int)is_signed_type(long));
549
550 trace_seq_printf(s, "\tfield: int overwrite;\t"
551 "offset:%u;\tsize:%u;\tsigned:%u;\n",
552 (unsigned int)offsetof(typeof(field), commit),
553 1,
554 (unsigned int)is_signed_type(long));
555
556 trace_seq_printf(s, "\tfield: char data;\t"
557 "offset:%u;\tsize:%u;\tsigned:%u;\n",
558 (unsigned int)offsetof(typeof(field), data),
559 (unsigned int)buffer->subbuf_size,
560 (unsigned int)is_signed_type(char));
561
562 return !trace_seq_has_overflowed(s);
563}
564
565static inline void rb_time_read(rb_time_t *t, u64 *ret)
566{
567 *ret = local64_read(&t->time);
568}
569static void rb_time_set(rb_time_t *t, u64 val)
570{
571 local64_set(&t->time, val);
572}
573
574/*
575 * Enable this to make sure that the event passed to
576 * ring_buffer_event_time_stamp() is not committed and also
577 * is on the buffer that it passed in.
578 */
579//#define RB_VERIFY_EVENT
580#ifdef RB_VERIFY_EVENT
581static struct list_head *rb_list_head(struct list_head *list);
582static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
583 void *event)
584{
585 struct buffer_page *page = cpu_buffer->commit_page;
586 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
587 struct list_head *next;
588 long commit, write;
589 unsigned long addr = (unsigned long)event;
590 bool done = false;
591 int stop = 0;
592
593 /* Make sure the event exists and is not committed yet */
594 do {
595 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
596 done = true;
597 commit = local_read(&page->page->commit);
598 write = local_read(&page->write);
599 if (addr >= (unsigned long)&page->page->data[commit] &&
600 addr < (unsigned long)&page->page->data[write])
601 return;
602
603 next = rb_list_head(page->list.next);
604 page = list_entry(next, struct buffer_page, list);
605 } while (!done);
606 WARN_ON_ONCE(1);
607}
608#else
609static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
610 void *event)
611{
612}
613#endif
614
615/*
616 * The absolute time stamp drops the 5 MSBs and some clocks may
617 * require them. The rb_fix_abs_ts() will take a previous full
618 * time stamp, and add the 5 MSB of that time stamp on to the
619 * saved absolute time stamp. Then they are compared in case of
620 * the unlikely event that the latest time stamp incremented
621 * the 5 MSB.
622 */
623static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
624{
625 if (save_ts & TS_MSB) {
626 abs |= save_ts & TS_MSB;
627 /* Check for overflow */
628 if (unlikely(abs < save_ts))
629 abs += 1ULL << 59;
630 }
631 return abs;
632}
633
634static inline u64 rb_time_stamp(struct trace_buffer *buffer);
635
636/**
637 * ring_buffer_event_time_stamp - return the event's current time stamp
638 * @buffer: The buffer that the event is on
639 * @event: the event to get the time stamp of
640 *
641 * Note, this must be called after @event is reserved, and before it is
642 * committed to the ring buffer. And must be called from the same
643 * context where the event was reserved (normal, softirq, irq, etc).
644 *
645 * Returns the time stamp associated with the current event.
646 * If the event has an extended time stamp, then that is used as
647 * the time stamp to return.
648 * In the highly unlikely case that the event was nested more than
649 * the max nesting, then the write_stamp of the buffer is returned,
650 * otherwise current time is returned, but that really neither of
651 * the last two cases should ever happen.
652 */
653u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
654 struct ring_buffer_event *event)
655{
656 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
657 unsigned int nest;
658 u64 ts;
659
660 /* If the event includes an absolute time, then just use that */
661 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
662 ts = rb_event_time_stamp(event);
663 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
664 }
665
666 nest = local_read(&cpu_buffer->committing);
667 verify_event(cpu_buffer, event);
668 if (WARN_ON_ONCE(!nest))
669 goto fail;
670
671 /* Read the current saved nesting level time stamp */
672 if (likely(--nest < MAX_NEST))
673 return cpu_buffer->event_stamp[nest];
674
675 /* Shouldn't happen, warn if it does */
676 WARN_ONCE(1, "nest (%d) greater than max", nest);
677
678 fail:
679 rb_time_read(&cpu_buffer->write_stamp, &ts);
680
681 return ts;
682}
683
684/**
685 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
686 * @buffer: The ring_buffer to get the number of pages from
687 * @cpu: The cpu of the ring_buffer to get the number of pages from
688 *
689 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
690 */
691size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
692{
693 return buffer->buffers[cpu]->nr_pages;
694}
695
696/**
697 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
698 * @buffer: The ring_buffer to get the number of pages from
699 * @cpu: The cpu of the ring_buffer to get the number of pages from
700 *
701 * Returns the number of pages that have content in the ring buffer.
702 */
703size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
704{
705 size_t read;
706 size_t lost;
707 size_t cnt;
708
709 read = local_read(&buffer->buffers[cpu]->pages_read);
710 lost = local_read(&buffer->buffers[cpu]->pages_lost);
711 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
712
713 if (WARN_ON_ONCE(cnt < lost))
714 return 0;
715
716 cnt -= lost;
717
718 /* The reader can read an empty page, but not more than that */
719 if (cnt < read) {
720 WARN_ON_ONCE(read > cnt + 1);
721 return 0;
722 }
723
724 return cnt - read;
725}
726
727static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
728{
729 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
730 size_t nr_pages;
731 size_t dirty;
732
733 nr_pages = cpu_buffer->nr_pages;
734 if (!nr_pages || !full)
735 return true;
736
737 /*
738 * Add one as dirty will never equal nr_pages, as the sub-buffer
739 * that the writer is on is not counted as dirty.
740 * This is needed if "buffer_percent" is set to 100.
741 */
742 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
743
744 return (dirty * 100) >= (full * nr_pages);
745}
746
747/*
748 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
749 *
750 * Schedules a delayed work to wake up any task that is blocked on the
751 * ring buffer waiters queue.
752 */
753static void rb_wake_up_waiters(struct irq_work *work)
754{
755 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
756
757 /* For waiters waiting for the first wake up */
758 (void)atomic_fetch_inc_release(&rbwork->seq);
759
760 wake_up_all(&rbwork->waiters);
761 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
762 /* Only cpu_buffer sets the above flags */
763 struct ring_buffer_per_cpu *cpu_buffer =
764 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
765
766 /* Called from interrupt context */
767 raw_spin_lock(&cpu_buffer->reader_lock);
768 rbwork->wakeup_full = false;
769 rbwork->full_waiters_pending = false;
770
771 /* Waking up all waiters, they will reset the shortest full */
772 cpu_buffer->shortest_full = 0;
773 raw_spin_unlock(&cpu_buffer->reader_lock);
774
775 wake_up_all(&rbwork->full_waiters);
776 }
777}
778
779/**
780 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
781 * @buffer: The ring buffer to wake waiters on
782 * @cpu: The CPU buffer to wake waiters on
783 *
784 * In the case of a file that represents a ring buffer is closing,
785 * it is prudent to wake up any waiters that are on this.
786 */
787void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
788{
789 struct ring_buffer_per_cpu *cpu_buffer;
790 struct rb_irq_work *rbwork;
791
792 if (!buffer)
793 return;
794
795 if (cpu == RING_BUFFER_ALL_CPUS) {
796
797 /* Wake up individual ones too. One level recursion */
798 for_each_buffer_cpu(buffer, cpu)
799 ring_buffer_wake_waiters(buffer, cpu);
800
801 rbwork = &buffer->irq_work;
802 } else {
803 if (WARN_ON_ONCE(!buffer->buffers))
804 return;
805 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
806 return;
807
808 cpu_buffer = buffer->buffers[cpu];
809 /* The CPU buffer may not have been initialized yet */
810 if (!cpu_buffer)
811 return;
812 rbwork = &cpu_buffer->irq_work;
813 }
814
815 /* This can be called in any context */
816 irq_work_queue(&rbwork->work);
817}
818
819static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
820{
821 struct ring_buffer_per_cpu *cpu_buffer;
822 bool ret = false;
823
824 /* Reads of all CPUs always waits for any data */
825 if (cpu == RING_BUFFER_ALL_CPUS)
826 return !ring_buffer_empty(buffer);
827
828 cpu_buffer = buffer->buffers[cpu];
829
830 if (!ring_buffer_empty_cpu(buffer, cpu)) {
831 unsigned long flags;
832 bool pagebusy;
833
834 if (!full)
835 return true;
836
837 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
838 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
839 ret = !pagebusy && full_hit(buffer, cpu, full);
840
841 if (!ret && (!cpu_buffer->shortest_full ||
842 cpu_buffer->shortest_full > full)) {
843 cpu_buffer->shortest_full = full;
844 }
845 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
846 }
847 return ret;
848}
849
850static inline bool
851rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
852 int cpu, int full, ring_buffer_cond_fn cond, void *data)
853{
854 if (rb_watermark_hit(buffer, cpu, full))
855 return true;
856
857 if (cond(data))
858 return true;
859
860 /*
861 * The events can happen in critical sections where
862 * checking a work queue can cause deadlocks.
863 * After adding a task to the queue, this flag is set
864 * only to notify events to try to wake up the queue
865 * using irq_work.
866 *
867 * We don't clear it even if the buffer is no longer
868 * empty. The flag only causes the next event to run
869 * irq_work to do the work queue wake up. The worse
870 * that can happen if we race with !trace_empty() is that
871 * an event will cause an irq_work to try to wake up
872 * an empty queue.
873 *
874 * There's no reason to protect this flag either, as
875 * the work queue and irq_work logic will do the necessary
876 * synchronization for the wake ups. The only thing
877 * that is necessary is that the wake up happens after
878 * a task has been queued. It's OK for spurious wake ups.
879 */
880 if (full)
881 rbwork->full_waiters_pending = true;
882 else
883 rbwork->waiters_pending = true;
884
885 return false;
886}
887
888struct rb_wait_data {
889 struct rb_irq_work *irq_work;
890 int seq;
891};
892
893/*
894 * The default wait condition for ring_buffer_wait() is to just to exit the
895 * wait loop the first time it is woken up.
896 */
897static bool rb_wait_once(void *data)
898{
899 struct rb_wait_data *rdata = data;
900 struct rb_irq_work *rbwork = rdata->irq_work;
901
902 return atomic_read_acquire(&rbwork->seq) != rdata->seq;
903}
904
905/**
906 * ring_buffer_wait - wait for input to the ring buffer
907 * @buffer: buffer to wait on
908 * @cpu: the cpu buffer to wait on
909 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
910 * @cond: condition function to break out of wait (NULL to run once)
911 * @data: the data to pass to @cond.
912 *
913 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
914 * as data is added to any of the @buffer's cpu buffers. Otherwise
915 * it will wait for data to be added to a specific cpu buffer.
916 */
917int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
918 ring_buffer_cond_fn cond, void *data)
919{
920 struct ring_buffer_per_cpu *cpu_buffer;
921 struct wait_queue_head *waitq;
922 struct rb_irq_work *rbwork;
923 struct rb_wait_data rdata;
924 int ret = 0;
925
926 /*
927 * Depending on what the caller is waiting for, either any
928 * data in any cpu buffer, or a specific buffer, put the
929 * caller on the appropriate wait queue.
930 */
931 if (cpu == RING_BUFFER_ALL_CPUS) {
932 rbwork = &buffer->irq_work;
933 /* Full only makes sense on per cpu reads */
934 full = 0;
935 } else {
936 if (!cpumask_test_cpu(cpu, buffer->cpumask))
937 return -ENODEV;
938 cpu_buffer = buffer->buffers[cpu];
939 rbwork = &cpu_buffer->irq_work;
940 }
941
942 if (full)
943 waitq = &rbwork->full_waiters;
944 else
945 waitq = &rbwork->waiters;
946
947 /* Set up to exit loop as soon as it is woken */
948 if (!cond) {
949 cond = rb_wait_once;
950 rdata.irq_work = rbwork;
951 rdata.seq = atomic_read_acquire(&rbwork->seq);
952 data = &rdata;
953 }
954
955 ret = wait_event_interruptible((*waitq),
956 rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
957
958 return ret;
959}
960
961/**
962 * ring_buffer_poll_wait - poll on buffer input
963 * @buffer: buffer to wait on
964 * @cpu: the cpu buffer to wait on
965 * @filp: the file descriptor
966 * @poll_table: The poll descriptor
967 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
968 *
969 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
970 * as data is added to any of the @buffer's cpu buffers. Otherwise
971 * it will wait for data to be added to a specific cpu buffer.
972 *
973 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
974 * zero otherwise.
975 */
976__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
977 struct file *filp, poll_table *poll_table, int full)
978{
979 struct ring_buffer_per_cpu *cpu_buffer;
980 struct rb_irq_work *rbwork;
981
982 if (cpu == RING_BUFFER_ALL_CPUS) {
983 rbwork = &buffer->irq_work;
984 full = 0;
985 } else {
986 if (!cpumask_test_cpu(cpu, buffer->cpumask))
987 return EPOLLERR;
988
989 cpu_buffer = buffer->buffers[cpu];
990 rbwork = &cpu_buffer->irq_work;
991 }
992
993 if (full) {
994 poll_wait(filp, &rbwork->full_waiters, poll_table);
995
996 if (rb_watermark_hit(buffer, cpu, full))
997 return EPOLLIN | EPOLLRDNORM;
998 /*
999 * Only allow full_waiters_pending update to be seen after
1000 * the shortest_full is set (in rb_watermark_hit). If the
1001 * writer sees the full_waiters_pending flag set, it will
1002 * compare the amount in the ring buffer to shortest_full.
1003 * If the amount in the ring buffer is greater than the
1004 * shortest_full percent, it will call the irq_work handler
1005 * to wake up this list. The irq_handler will reset shortest_full
1006 * back to zero. That's done under the reader_lock, but
1007 * the below smp_mb() makes sure that the update to
1008 * full_waiters_pending doesn't leak up into the above.
1009 */
1010 smp_mb();
1011 rbwork->full_waiters_pending = true;
1012 return 0;
1013 }
1014
1015 poll_wait(filp, &rbwork->waiters, poll_table);
1016 rbwork->waiters_pending = true;
1017
1018 /*
1019 * There's a tight race between setting the waiters_pending and
1020 * checking if the ring buffer is empty. Once the waiters_pending bit
1021 * is set, the next event will wake the task up, but we can get stuck
1022 * if there's only a single event in.
1023 *
1024 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1025 * but adding a memory barrier to all events will cause too much of a
1026 * performance hit in the fast path. We only need a memory barrier when
1027 * the buffer goes from empty to having content. But as this race is
1028 * extremely small, and it's not a problem if another event comes in, we
1029 * will fix it later.
1030 */
1031 smp_mb();
1032
1033 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1034 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1035 return EPOLLIN | EPOLLRDNORM;
1036 return 0;
1037}
1038
1039/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1040#define RB_WARN_ON(b, cond) \
1041 ({ \
1042 int _____ret = unlikely(cond); \
1043 if (_____ret) { \
1044 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1045 struct ring_buffer_per_cpu *__b = \
1046 (void *)b; \
1047 atomic_inc(&__b->buffer->record_disabled); \
1048 } else \
1049 atomic_inc(&b->record_disabled); \
1050 WARN_ON(1); \
1051 } \
1052 _____ret; \
1053 })
1054
1055/* Up this if you want to test the TIME_EXTENTS and normalization */
1056#define DEBUG_SHIFT 0
1057
1058static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1059{
1060 u64 ts;
1061
1062 /* Skip retpolines :-( */
1063 if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1064 ts = trace_clock_local();
1065 else
1066 ts = buffer->clock();
1067
1068 /* shift to debug/test normalization and TIME_EXTENTS */
1069 return ts << DEBUG_SHIFT;
1070}
1071
1072u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1073{
1074 u64 time;
1075
1076 preempt_disable_notrace();
1077 time = rb_time_stamp(buffer);
1078 preempt_enable_notrace();
1079
1080 return time;
1081}
1082EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1083
1084void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1085 int cpu, u64 *ts)
1086{
1087 /* Just stupid testing the normalize function and deltas */
1088 *ts >>= DEBUG_SHIFT;
1089}
1090EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1091
1092/*
1093 * Making the ring buffer lockless makes things tricky.
1094 * Although writes only happen on the CPU that they are on,
1095 * and they only need to worry about interrupts. Reads can
1096 * happen on any CPU.
1097 *
1098 * The reader page is always off the ring buffer, but when the
1099 * reader finishes with a page, it needs to swap its page with
1100 * a new one from the buffer. The reader needs to take from
1101 * the head (writes go to the tail). But if a writer is in overwrite
1102 * mode and wraps, it must push the head page forward.
1103 *
1104 * Here lies the problem.
1105 *
1106 * The reader must be careful to replace only the head page, and
1107 * not another one. As described at the top of the file in the
1108 * ASCII art, the reader sets its old page to point to the next
1109 * page after head. It then sets the page after head to point to
1110 * the old reader page. But if the writer moves the head page
1111 * during this operation, the reader could end up with the tail.
1112 *
1113 * We use cmpxchg to help prevent this race. We also do something
1114 * special with the page before head. We set the LSB to 1.
1115 *
1116 * When the writer must push the page forward, it will clear the
1117 * bit that points to the head page, move the head, and then set
1118 * the bit that points to the new head page.
1119 *
1120 * We also don't want an interrupt coming in and moving the head
1121 * page on another writer. Thus we use the second LSB to catch
1122 * that too. Thus:
1123 *
1124 * head->list->prev->next bit 1 bit 0
1125 * ------- -------
1126 * Normal page 0 0
1127 * Points to head page 0 1
1128 * New head page 1 0
1129 *
1130 * Note we can not trust the prev pointer of the head page, because:
1131 *
1132 * +----+ +-----+ +-----+
1133 * | |------>| T |---X--->| N |
1134 * | |<------| | | |
1135 * +----+ +-----+ +-----+
1136 * ^ ^ |
1137 * | +-----+ | |
1138 * +----------| R |----------+ |
1139 * | |<-----------+
1140 * +-----+
1141 *
1142 * Key: ---X--> HEAD flag set in pointer
1143 * T Tail page
1144 * R Reader page
1145 * N Next page
1146 *
1147 * (see __rb_reserve_next() to see where this happens)
1148 *
1149 * What the above shows is that the reader just swapped out
1150 * the reader page with a page in the buffer, but before it
1151 * could make the new header point back to the new page added
1152 * it was preempted by a writer. The writer moved forward onto
1153 * the new page added by the reader and is about to move forward
1154 * again.
1155 *
1156 * You can see, it is legitimate for the previous pointer of
1157 * the head (or any page) not to point back to itself. But only
1158 * temporarily.
1159 */
1160
1161#define RB_PAGE_NORMAL 0UL
1162#define RB_PAGE_HEAD 1UL
1163#define RB_PAGE_UPDATE 2UL
1164
1165
1166#define RB_FLAG_MASK 3UL
1167
1168/* PAGE_MOVED is not part of the mask */
1169#define RB_PAGE_MOVED 4UL
1170
1171/*
1172 * rb_list_head - remove any bit
1173 */
1174static struct list_head *rb_list_head(struct list_head *list)
1175{
1176 unsigned long val = (unsigned long)list;
1177
1178 return (struct list_head *)(val & ~RB_FLAG_MASK);
1179}
1180
1181/*
1182 * rb_is_head_page - test if the given page is the head page
1183 *
1184 * Because the reader may move the head_page pointer, we can
1185 * not trust what the head page is (it may be pointing to
1186 * the reader page). But if the next page is a header page,
1187 * its flags will be non zero.
1188 */
1189static inline int
1190rb_is_head_page(struct buffer_page *page, struct list_head *list)
1191{
1192 unsigned long val;
1193
1194 val = (unsigned long)list->next;
1195
1196 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1197 return RB_PAGE_MOVED;
1198
1199 return val & RB_FLAG_MASK;
1200}
1201
1202/*
1203 * rb_is_reader_page
1204 *
1205 * The unique thing about the reader page, is that, if the
1206 * writer is ever on it, the previous pointer never points
1207 * back to the reader page.
1208 */
1209static bool rb_is_reader_page(struct buffer_page *page)
1210{
1211 struct list_head *list = page->list.prev;
1212
1213 return rb_list_head(list->next) != &page->list;
1214}
1215
1216/*
1217 * rb_set_list_to_head - set a list_head to be pointing to head.
1218 */
1219static void rb_set_list_to_head(struct list_head *list)
1220{
1221 unsigned long *ptr;
1222
1223 ptr = (unsigned long *)&list->next;
1224 *ptr |= RB_PAGE_HEAD;
1225 *ptr &= ~RB_PAGE_UPDATE;
1226}
1227
1228/*
1229 * rb_head_page_activate - sets up head page
1230 */
1231static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1232{
1233 struct buffer_page *head;
1234
1235 head = cpu_buffer->head_page;
1236 if (!head)
1237 return;
1238
1239 /*
1240 * Set the previous list pointer to have the HEAD flag.
1241 */
1242 rb_set_list_to_head(head->list.prev);
1243}
1244
1245static void rb_list_head_clear(struct list_head *list)
1246{
1247 unsigned long *ptr = (unsigned long *)&list->next;
1248
1249 *ptr &= ~RB_FLAG_MASK;
1250}
1251
1252/*
1253 * rb_head_page_deactivate - clears head page ptr (for free list)
1254 */
1255static void
1256rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1257{
1258 struct list_head *hd;
1259
1260 /* Go through the whole list and clear any pointers found. */
1261 rb_list_head_clear(cpu_buffer->pages);
1262
1263 list_for_each(hd, cpu_buffer->pages)
1264 rb_list_head_clear(hd);
1265}
1266
1267static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1268 struct buffer_page *head,
1269 struct buffer_page *prev,
1270 int old_flag, int new_flag)
1271{
1272 struct list_head *list;
1273 unsigned long val = (unsigned long)&head->list;
1274 unsigned long ret;
1275
1276 list = &prev->list;
1277
1278 val &= ~RB_FLAG_MASK;
1279
1280 ret = cmpxchg((unsigned long *)&list->next,
1281 val | old_flag, val | new_flag);
1282
1283 /* check if the reader took the page */
1284 if ((ret & ~RB_FLAG_MASK) != val)
1285 return RB_PAGE_MOVED;
1286
1287 return ret & RB_FLAG_MASK;
1288}
1289
1290static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1291 struct buffer_page *head,
1292 struct buffer_page *prev,
1293 int old_flag)
1294{
1295 return rb_head_page_set(cpu_buffer, head, prev,
1296 old_flag, RB_PAGE_UPDATE);
1297}
1298
1299static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1300 struct buffer_page *head,
1301 struct buffer_page *prev,
1302 int old_flag)
1303{
1304 return rb_head_page_set(cpu_buffer, head, prev,
1305 old_flag, RB_PAGE_HEAD);
1306}
1307
1308static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1309 struct buffer_page *head,
1310 struct buffer_page *prev,
1311 int old_flag)
1312{
1313 return rb_head_page_set(cpu_buffer, head, prev,
1314 old_flag, RB_PAGE_NORMAL);
1315}
1316
1317static inline void rb_inc_page(struct buffer_page **bpage)
1318{
1319 struct list_head *p = rb_list_head((*bpage)->list.next);
1320
1321 *bpage = list_entry(p, struct buffer_page, list);
1322}
1323
1324static struct buffer_page *
1325rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1326{
1327 struct buffer_page *head;
1328 struct buffer_page *page;
1329 struct list_head *list;
1330 int i;
1331
1332 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1333 return NULL;
1334
1335 /* sanity check */
1336 list = cpu_buffer->pages;
1337 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1338 return NULL;
1339
1340 page = head = cpu_buffer->head_page;
1341 /*
1342 * It is possible that the writer moves the header behind
1343 * where we started, and we miss in one loop.
1344 * A second loop should grab the header, but we'll do
1345 * three loops just because I'm paranoid.
1346 */
1347 for (i = 0; i < 3; i++) {
1348 do {
1349 if (rb_is_head_page(page, page->list.prev)) {
1350 cpu_buffer->head_page = page;
1351 return page;
1352 }
1353 rb_inc_page(&page);
1354 } while (page != head);
1355 }
1356
1357 RB_WARN_ON(cpu_buffer, 1);
1358
1359 return NULL;
1360}
1361
1362static bool rb_head_page_replace(struct buffer_page *old,
1363 struct buffer_page *new)
1364{
1365 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1366 unsigned long val;
1367
1368 val = *ptr & ~RB_FLAG_MASK;
1369 val |= RB_PAGE_HEAD;
1370
1371 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1372}
1373
1374/*
1375 * rb_tail_page_update - move the tail page forward
1376 */
1377static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1378 struct buffer_page *tail_page,
1379 struct buffer_page *next_page)
1380{
1381 unsigned long old_entries;
1382 unsigned long old_write;
1383
1384 /*
1385 * The tail page now needs to be moved forward.
1386 *
1387 * We need to reset the tail page, but without messing
1388 * with possible erasing of data brought in by interrupts
1389 * that have moved the tail page and are currently on it.
1390 *
1391 * We add a counter to the write field to denote this.
1392 */
1393 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1394 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1395
1396 /*
1397 * Just make sure we have seen our old_write and synchronize
1398 * with any interrupts that come in.
1399 */
1400 barrier();
1401
1402 /*
1403 * If the tail page is still the same as what we think
1404 * it is, then it is up to us to update the tail
1405 * pointer.
1406 */
1407 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1408 /* Zero the write counter */
1409 unsigned long val = old_write & ~RB_WRITE_MASK;
1410 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1411
1412 /*
1413 * This will only succeed if an interrupt did
1414 * not come in and change it. In which case, we
1415 * do not want to modify it.
1416 *
1417 * We add (void) to let the compiler know that we do not care
1418 * about the return value of these functions. We use the
1419 * cmpxchg to only update if an interrupt did not already
1420 * do it for us. If the cmpxchg fails, we don't care.
1421 */
1422 (void)local_cmpxchg(&next_page->write, old_write, val);
1423 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1424
1425 /*
1426 * No need to worry about races with clearing out the commit.
1427 * it only can increment when a commit takes place. But that
1428 * only happens in the outer most nested commit.
1429 */
1430 local_set(&next_page->page->commit, 0);
1431
1432 /* Either we update tail_page or an interrupt does */
1433 if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1434 local_inc(&cpu_buffer->pages_touched);
1435 }
1436}
1437
1438static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1439 struct buffer_page *bpage)
1440{
1441 unsigned long val = (unsigned long)bpage;
1442
1443 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1444}
1445
1446/**
1447 * rb_check_pages - integrity check of buffer pages
1448 * @cpu_buffer: CPU buffer with pages to test
1449 *
1450 * As a safety measure we check to make sure the data pages have not
1451 * been corrupted.
1452 *
1453 * Callers of this function need to guarantee that the list of pages doesn't get
1454 * modified during the check. In particular, if it's possible that the function
1455 * is invoked with concurrent readers which can swap in a new reader page then
1456 * the caller should take cpu_buffer->reader_lock.
1457 */
1458static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1459{
1460 struct list_head *head = rb_list_head(cpu_buffer->pages);
1461 struct list_head *tmp;
1462
1463 if (RB_WARN_ON(cpu_buffer,
1464 rb_list_head(rb_list_head(head->next)->prev) != head))
1465 return;
1466
1467 if (RB_WARN_ON(cpu_buffer,
1468 rb_list_head(rb_list_head(head->prev)->next) != head))
1469 return;
1470
1471 for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) {
1472 if (RB_WARN_ON(cpu_buffer,
1473 rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
1474 return;
1475
1476 if (RB_WARN_ON(cpu_buffer,
1477 rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
1478 return;
1479 }
1480}
1481
1482static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1483 long nr_pages, struct list_head *pages)
1484{
1485 struct buffer_page *bpage, *tmp;
1486 bool user_thread = current->mm != NULL;
1487 gfp_t mflags;
1488 long i;
1489
1490 /*
1491 * Check if the available memory is there first.
1492 * Note, si_mem_available() only gives us a rough estimate of available
1493 * memory. It may not be accurate. But we don't care, we just want
1494 * to prevent doing any allocation when it is obvious that it is
1495 * not going to succeed.
1496 */
1497 i = si_mem_available();
1498 if (i < nr_pages)
1499 return -ENOMEM;
1500
1501 /*
1502 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1503 * gracefully without invoking oom-killer and the system is not
1504 * destabilized.
1505 */
1506 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1507
1508 /*
1509 * If a user thread allocates too much, and si_mem_available()
1510 * reports there's enough memory, even though there is not.
1511 * Make sure the OOM killer kills this thread. This can happen
1512 * even with RETRY_MAYFAIL because another task may be doing
1513 * an allocation after this task has taken all memory.
1514 * This is the task the OOM killer needs to take out during this
1515 * loop, even if it was triggered by an allocation somewhere else.
1516 */
1517 if (user_thread)
1518 set_current_oom_origin();
1519 for (i = 0; i < nr_pages; i++) {
1520 struct page *page;
1521
1522 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1523 mflags, cpu_to_node(cpu_buffer->cpu));
1524 if (!bpage)
1525 goto free_pages;
1526
1527 rb_check_bpage(cpu_buffer, bpage);
1528
1529 list_add(&bpage->list, pages);
1530
1531 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
1532 mflags | __GFP_ZERO,
1533 cpu_buffer->buffer->subbuf_order);
1534 if (!page)
1535 goto free_pages;
1536 bpage->page = page_address(page);
1537 bpage->order = cpu_buffer->buffer->subbuf_order;
1538 rb_init_page(bpage->page);
1539
1540 if (user_thread && fatal_signal_pending(current))
1541 goto free_pages;
1542 }
1543 if (user_thread)
1544 clear_current_oom_origin();
1545
1546 return 0;
1547
1548free_pages:
1549 list_for_each_entry_safe(bpage, tmp, pages, list) {
1550 list_del_init(&bpage->list);
1551 free_buffer_page(bpage);
1552 }
1553 if (user_thread)
1554 clear_current_oom_origin();
1555
1556 return -ENOMEM;
1557}
1558
1559static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1560 unsigned long nr_pages)
1561{
1562 LIST_HEAD(pages);
1563
1564 WARN_ON(!nr_pages);
1565
1566 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1567 return -ENOMEM;
1568
1569 /*
1570 * The ring buffer page list is a circular list that does not
1571 * start and end with a list head. All page list items point to
1572 * other pages.
1573 */
1574 cpu_buffer->pages = pages.next;
1575 list_del(&pages);
1576
1577 cpu_buffer->nr_pages = nr_pages;
1578
1579 rb_check_pages(cpu_buffer);
1580
1581 return 0;
1582}
1583
1584static struct ring_buffer_per_cpu *
1585rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1586{
1587 struct ring_buffer_per_cpu *cpu_buffer;
1588 struct buffer_page *bpage;
1589 struct page *page;
1590 int ret;
1591
1592 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1593 GFP_KERNEL, cpu_to_node(cpu));
1594 if (!cpu_buffer)
1595 return NULL;
1596
1597 cpu_buffer->cpu = cpu;
1598 cpu_buffer->buffer = buffer;
1599 raw_spin_lock_init(&cpu_buffer->reader_lock);
1600 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1601 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1602 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1603 init_completion(&cpu_buffer->update_done);
1604 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1605 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1606 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1607
1608 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1609 GFP_KERNEL, cpu_to_node(cpu));
1610 if (!bpage)
1611 goto fail_free_buffer;
1612
1613 rb_check_bpage(cpu_buffer, bpage);
1614
1615 cpu_buffer->reader_page = bpage;
1616
1617 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_ZERO,
1618 cpu_buffer->buffer->subbuf_order);
1619 if (!page)
1620 goto fail_free_reader;
1621 bpage->page = page_address(page);
1622 rb_init_page(bpage->page);
1623
1624 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1625 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1626
1627 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1628 if (ret < 0)
1629 goto fail_free_reader;
1630
1631 cpu_buffer->head_page
1632 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1633 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1634
1635 rb_head_page_activate(cpu_buffer);
1636
1637 return cpu_buffer;
1638
1639 fail_free_reader:
1640 free_buffer_page(cpu_buffer->reader_page);
1641
1642 fail_free_buffer:
1643 kfree(cpu_buffer);
1644 return NULL;
1645}
1646
1647static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1648{
1649 struct list_head *head = cpu_buffer->pages;
1650 struct buffer_page *bpage, *tmp;
1651
1652 irq_work_sync(&cpu_buffer->irq_work.work);
1653
1654 free_buffer_page(cpu_buffer->reader_page);
1655
1656 if (head) {
1657 rb_head_page_deactivate(cpu_buffer);
1658
1659 list_for_each_entry_safe(bpage, tmp, head, list) {
1660 list_del_init(&bpage->list);
1661 free_buffer_page(bpage);
1662 }
1663 bpage = list_entry(head, struct buffer_page, list);
1664 free_buffer_page(bpage);
1665 }
1666
1667 free_page((unsigned long)cpu_buffer->free_page);
1668
1669 kfree(cpu_buffer);
1670}
1671
1672/**
1673 * __ring_buffer_alloc - allocate a new ring_buffer
1674 * @size: the size in bytes per cpu that is needed.
1675 * @flags: attributes to set for the ring buffer.
1676 * @key: ring buffer reader_lock_key.
1677 *
1678 * Currently the only flag that is available is the RB_FL_OVERWRITE
1679 * flag. This flag means that the buffer will overwrite old data
1680 * when the buffer wraps. If this flag is not set, the buffer will
1681 * drop data when the tail hits the head.
1682 */
1683struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1684 struct lock_class_key *key)
1685{
1686 struct trace_buffer *buffer;
1687 long nr_pages;
1688 int bsize;
1689 int cpu;
1690 int ret;
1691
1692 /* keep it in its own cache line */
1693 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1694 GFP_KERNEL);
1695 if (!buffer)
1696 return NULL;
1697
1698 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1699 goto fail_free_buffer;
1700
1701 /* Default buffer page size - one system page */
1702 buffer->subbuf_order = 0;
1703 buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
1704
1705 /* Max payload is buffer page size - header (8bytes) */
1706 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
1707
1708 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
1709 buffer->flags = flags;
1710 buffer->clock = trace_clock_local;
1711 buffer->reader_lock_key = key;
1712
1713 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1714 init_waitqueue_head(&buffer->irq_work.waiters);
1715
1716 /* need at least two pages */
1717 if (nr_pages < 2)
1718 nr_pages = 2;
1719
1720 buffer->cpus = nr_cpu_ids;
1721
1722 bsize = sizeof(void *) * nr_cpu_ids;
1723 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1724 GFP_KERNEL);
1725 if (!buffer->buffers)
1726 goto fail_free_cpumask;
1727
1728 cpu = raw_smp_processor_id();
1729 cpumask_set_cpu(cpu, buffer->cpumask);
1730 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1731 if (!buffer->buffers[cpu])
1732 goto fail_free_buffers;
1733
1734 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1735 if (ret < 0)
1736 goto fail_free_buffers;
1737
1738 mutex_init(&buffer->mutex);
1739
1740 return buffer;
1741
1742 fail_free_buffers:
1743 for_each_buffer_cpu(buffer, cpu) {
1744 if (buffer->buffers[cpu])
1745 rb_free_cpu_buffer(buffer->buffers[cpu]);
1746 }
1747 kfree(buffer->buffers);
1748
1749 fail_free_cpumask:
1750 free_cpumask_var(buffer->cpumask);
1751
1752 fail_free_buffer:
1753 kfree(buffer);
1754 return NULL;
1755}
1756EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1757
1758/**
1759 * ring_buffer_free - free a ring buffer.
1760 * @buffer: the buffer to free.
1761 */
1762void
1763ring_buffer_free(struct trace_buffer *buffer)
1764{
1765 int cpu;
1766
1767 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1768
1769 irq_work_sync(&buffer->irq_work.work);
1770
1771 for_each_buffer_cpu(buffer, cpu)
1772 rb_free_cpu_buffer(buffer->buffers[cpu]);
1773
1774 kfree(buffer->buffers);
1775 free_cpumask_var(buffer->cpumask);
1776
1777 kfree(buffer);
1778}
1779EXPORT_SYMBOL_GPL(ring_buffer_free);
1780
1781void ring_buffer_set_clock(struct trace_buffer *buffer,
1782 u64 (*clock)(void))
1783{
1784 buffer->clock = clock;
1785}
1786
1787void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1788{
1789 buffer->time_stamp_abs = abs;
1790}
1791
1792bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1793{
1794 return buffer->time_stamp_abs;
1795}
1796
1797static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1798
1799static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1800{
1801 return local_read(&bpage->entries) & RB_WRITE_MASK;
1802}
1803
1804static inline unsigned long rb_page_write(struct buffer_page *bpage)
1805{
1806 return local_read(&bpage->write) & RB_WRITE_MASK;
1807}
1808
1809static bool
1810rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1811{
1812 struct list_head *tail_page, *to_remove, *next_page;
1813 struct buffer_page *to_remove_page, *tmp_iter_page;
1814 struct buffer_page *last_page, *first_page;
1815 unsigned long nr_removed;
1816 unsigned long head_bit;
1817 int page_entries;
1818
1819 head_bit = 0;
1820
1821 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1822 atomic_inc(&cpu_buffer->record_disabled);
1823 /*
1824 * We don't race with the readers since we have acquired the reader
1825 * lock. We also don't race with writers after disabling recording.
1826 * This makes it easy to figure out the first and the last page to be
1827 * removed from the list. We unlink all the pages in between including
1828 * the first and last pages. This is done in a busy loop so that we
1829 * lose the least number of traces.
1830 * The pages are freed after we restart recording and unlock readers.
1831 */
1832 tail_page = &cpu_buffer->tail_page->list;
1833
1834 /*
1835 * tail page might be on reader page, we remove the next page
1836 * from the ring buffer
1837 */
1838 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1839 tail_page = rb_list_head(tail_page->next);
1840 to_remove = tail_page;
1841
1842 /* start of pages to remove */
1843 first_page = list_entry(rb_list_head(to_remove->next),
1844 struct buffer_page, list);
1845
1846 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1847 to_remove = rb_list_head(to_remove)->next;
1848 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1849 }
1850 /* Read iterators need to reset themselves when some pages removed */
1851 cpu_buffer->pages_removed += nr_removed;
1852
1853 next_page = rb_list_head(to_remove)->next;
1854
1855 /*
1856 * Now we remove all pages between tail_page and next_page.
1857 * Make sure that we have head_bit value preserved for the
1858 * next page
1859 */
1860 tail_page->next = (struct list_head *)((unsigned long)next_page |
1861 head_bit);
1862 next_page = rb_list_head(next_page);
1863 next_page->prev = tail_page;
1864
1865 /* make sure pages points to a valid page in the ring buffer */
1866 cpu_buffer->pages = next_page;
1867
1868 /* update head page */
1869 if (head_bit)
1870 cpu_buffer->head_page = list_entry(next_page,
1871 struct buffer_page, list);
1872
1873 /* pages are removed, resume tracing and then free the pages */
1874 atomic_dec(&cpu_buffer->record_disabled);
1875 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1876
1877 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1878
1879 /* last buffer page to remove */
1880 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1881 list);
1882 tmp_iter_page = first_page;
1883
1884 do {
1885 cond_resched();
1886
1887 to_remove_page = tmp_iter_page;
1888 rb_inc_page(&tmp_iter_page);
1889
1890 /* update the counters */
1891 page_entries = rb_page_entries(to_remove_page);
1892 if (page_entries) {
1893 /*
1894 * If something was added to this page, it was full
1895 * since it is not the tail page. So we deduct the
1896 * bytes consumed in ring buffer from here.
1897 * Increment overrun to account for the lost events.
1898 */
1899 local_add(page_entries, &cpu_buffer->overrun);
1900 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
1901 local_inc(&cpu_buffer->pages_lost);
1902 }
1903
1904 /*
1905 * We have already removed references to this list item, just
1906 * free up the buffer_page and its page
1907 */
1908 free_buffer_page(to_remove_page);
1909 nr_removed--;
1910
1911 } while (to_remove_page != last_page);
1912
1913 RB_WARN_ON(cpu_buffer, nr_removed);
1914
1915 return nr_removed == 0;
1916}
1917
1918static bool
1919rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1920{
1921 struct list_head *pages = &cpu_buffer->new_pages;
1922 unsigned long flags;
1923 bool success;
1924 int retries;
1925
1926 /* Can be called at early boot up, where interrupts must not been enabled */
1927 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1928 /*
1929 * We are holding the reader lock, so the reader page won't be swapped
1930 * in the ring buffer. Now we are racing with the writer trying to
1931 * move head page and the tail page.
1932 * We are going to adapt the reader page update process where:
1933 * 1. We first splice the start and end of list of new pages between
1934 * the head page and its previous page.
1935 * 2. We cmpxchg the prev_page->next to point from head page to the
1936 * start of new pages list.
1937 * 3. Finally, we update the head->prev to the end of new list.
1938 *
1939 * We will try this process 10 times, to make sure that we don't keep
1940 * spinning.
1941 */
1942 retries = 10;
1943 success = false;
1944 while (retries--) {
1945 struct list_head *head_page, *prev_page;
1946 struct list_head *last_page, *first_page;
1947 struct list_head *head_page_with_bit;
1948 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
1949
1950 if (!hpage)
1951 break;
1952 head_page = &hpage->list;
1953 prev_page = head_page->prev;
1954
1955 first_page = pages->next;
1956 last_page = pages->prev;
1957
1958 head_page_with_bit = (struct list_head *)
1959 ((unsigned long)head_page | RB_PAGE_HEAD);
1960
1961 last_page->next = head_page_with_bit;
1962 first_page->prev = prev_page;
1963
1964 /* caution: head_page_with_bit gets updated on cmpxchg failure */
1965 if (try_cmpxchg(&prev_page->next,
1966 &head_page_with_bit, first_page)) {
1967 /*
1968 * yay, we replaced the page pointer to our new list,
1969 * now, we just have to update to head page's prev
1970 * pointer to point to end of list
1971 */
1972 head_page->prev = last_page;
1973 success = true;
1974 break;
1975 }
1976 }
1977
1978 if (success)
1979 INIT_LIST_HEAD(pages);
1980 /*
1981 * If we weren't successful in adding in new pages, warn and stop
1982 * tracing
1983 */
1984 RB_WARN_ON(cpu_buffer, !success);
1985 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1986
1987 /* free pages if they weren't inserted */
1988 if (!success) {
1989 struct buffer_page *bpage, *tmp;
1990 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1991 list) {
1992 list_del_init(&bpage->list);
1993 free_buffer_page(bpage);
1994 }
1995 }
1996 return success;
1997}
1998
1999static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2000{
2001 bool success;
2002
2003 if (cpu_buffer->nr_pages_to_update > 0)
2004 success = rb_insert_pages(cpu_buffer);
2005 else
2006 success = rb_remove_pages(cpu_buffer,
2007 -cpu_buffer->nr_pages_to_update);
2008
2009 if (success)
2010 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2011}
2012
2013static void update_pages_handler(struct work_struct *work)
2014{
2015 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2016 struct ring_buffer_per_cpu, update_pages_work);
2017 rb_update_pages(cpu_buffer);
2018 complete(&cpu_buffer->update_done);
2019}
2020
2021/**
2022 * ring_buffer_resize - resize the ring buffer
2023 * @buffer: the buffer to resize.
2024 * @size: the new size.
2025 * @cpu_id: the cpu buffer to resize
2026 *
2027 * Minimum size is 2 * buffer->subbuf_size.
2028 *
2029 * Returns 0 on success and < 0 on failure.
2030 */
2031int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2032 int cpu_id)
2033{
2034 struct ring_buffer_per_cpu *cpu_buffer;
2035 unsigned long nr_pages;
2036 int cpu, err;
2037
2038 /*
2039 * Always succeed at resizing a non-existent buffer:
2040 */
2041 if (!buffer)
2042 return 0;
2043
2044 /* Make sure the requested buffer exists */
2045 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2046 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2047 return 0;
2048
2049 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2050
2051 /* we need a minimum of two pages */
2052 if (nr_pages < 2)
2053 nr_pages = 2;
2054
2055 /* prevent another thread from changing buffer sizes */
2056 mutex_lock(&buffer->mutex);
2057 atomic_inc(&buffer->resizing);
2058
2059 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2060 /*
2061 * Don't succeed if resizing is disabled, as a reader might be
2062 * manipulating the ring buffer and is expecting a sane state while
2063 * this is true.
2064 */
2065 for_each_buffer_cpu(buffer, cpu) {
2066 cpu_buffer = buffer->buffers[cpu];
2067 if (atomic_read(&cpu_buffer->resize_disabled)) {
2068 err = -EBUSY;
2069 goto out_err_unlock;
2070 }
2071 }
2072
2073 /* calculate the pages to update */
2074 for_each_buffer_cpu(buffer, cpu) {
2075 cpu_buffer = buffer->buffers[cpu];
2076
2077 cpu_buffer->nr_pages_to_update = nr_pages -
2078 cpu_buffer->nr_pages;
2079 /*
2080 * nothing more to do for removing pages or no update
2081 */
2082 if (cpu_buffer->nr_pages_to_update <= 0)
2083 continue;
2084 /*
2085 * to add pages, make sure all new pages can be
2086 * allocated without receiving ENOMEM
2087 */
2088 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2089 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2090 &cpu_buffer->new_pages)) {
2091 /* not enough memory for new pages */
2092 err = -ENOMEM;
2093 goto out_err;
2094 }
2095
2096 cond_resched();
2097 }
2098
2099 cpus_read_lock();
2100 /*
2101 * Fire off all the required work handlers
2102 * We can't schedule on offline CPUs, but it's not necessary
2103 * since we can change their buffer sizes without any race.
2104 */
2105 for_each_buffer_cpu(buffer, cpu) {
2106 cpu_buffer = buffer->buffers[cpu];
2107 if (!cpu_buffer->nr_pages_to_update)
2108 continue;
2109
2110 /* Can't run something on an offline CPU. */
2111 if (!cpu_online(cpu)) {
2112 rb_update_pages(cpu_buffer);
2113 cpu_buffer->nr_pages_to_update = 0;
2114 } else {
2115 /* Run directly if possible. */
2116 migrate_disable();
2117 if (cpu != smp_processor_id()) {
2118 migrate_enable();
2119 schedule_work_on(cpu,
2120 &cpu_buffer->update_pages_work);
2121 } else {
2122 update_pages_handler(&cpu_buffer->update_pages_work);
2123 migrate_enable();
2124 }
2125 }
2126 }
2127
2128 /* wait for all the updates to complete */
2129 for_each_buffer_cpu(buffer, cpu) {
2130 cpu_buffer = buffer->buffers[cpu];
2131 if (!cpu_buffer->nr_pages_to_update)
2132 continue;
2133
2134 if (cpu_online(cpu))
2135 wait_for_completion(&cpu_buffer->update_done);
2136 cpu_buffer->nr_pages_to_update = 0;
2137 }
2138
2139 cpus_read_unlock();
2140 } else {
2141 cpu_buffer = buffer->buffers[cpu_id];
2142
2143 if (nr_pages == cpu_buffer->nr_pages)
2144 goto out;
2145
2146 /*
2147 * Don't succeed if resizing is disabled, as a reader might be
2148 * manipulating the ring buffer and is expecting a sane state while
2149 * this is true.
2150 */
2151 if (atomic_read(&cpu_buffer->resize_disabled)) {
2152 err = -EBUSY;
2153 goto out_err_unlock;
2154 }
2155
2156 cpu_buffer->nr_pages_to_update = nr_pages -
2157 cpu_buffer->nr_pages;
2158
2159 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2160 if (cpu_buffer->nr_pages_to_update > 0 &&
2161 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2162 &cpu_buffer->new_pages)) {
2163 err = -ENOMEM;
2164 goto out_err;
2165 }
2166
2167 cpus_read_lock();
2168
2169 /* Can't run something on an offline CPU. */
2170 if (!cpu_online(cpu_id))
2171 rb_update_pages(cpu_buffer);
2172 else {
2173 /* Run directly if possible. */
2174 migrate_disable();
2175 if (cpu_id == smp_processor_id()) {
2176 rb_update_pages(cpu_buffer);
2177 migrate_enable();
2178 } else {
2179 migrate_enable();
2180 schedule_work_on(cpu_id,
2181 &cpu_buffer->update_pages_work);
2182 wait_for_completion(&cpu_buffer->update_done);
2183 }
2184 }
2185
2186 cpu_buffer->nr_pages_to_update = 0;
2187 cpus_read_unlock();
2188 }
2189
2190 out:
2191 /*
2192 * The ring buffer resize can happen with the ring buffer
2193 * enabled, so that the update disturbs the tracing as little
2194 * as possible. But if the buffer is disabled, we do not need
2195 * to worry about that, and we can take the time to verify
2196 * that the buffer is not corrupt.
2197 */
2198 if (atomic_read(&buffer->record_disabled)) {
2199 atomic_inc(&buffer->record_disabled);
2200 /*
2201 * Even though the buffer was disabled, we must make sure
2202 * that it is truly disabled before calling rb_check_pages.
2203 * There could have been a race between checking
2204 * record_disable and incrementing it.
2205 */
2206 synchronize_rcu();
2207 for_each_buffer_cpu(buffer, cpu) {
2208 unsigned long flags;
2209
2210 cpu_buffer = buffer->buffers[cpu];
2211 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2212 rb_check_pages(cpu_buffer);
2213 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2214 }
2215 atomic_dec(&buffer->record_disabled);
2216 }
2217
2218 atomic_dec(&buffer->resizing);
2219 mutex_unlock(&buffer->mutex);
2220 return 0;
2221
2222 out_err:
2223 for_each_buffer_cpu(buffer, cpu) {
2224 struct buffer_page *bpage, *tmp;
2225
2226 cpu_buffer = buffer->buffers[cpu];
2227 cpu_buffer->nr_pages_to_update = 0;
2228
2229 if (list_empty(&cpu_buffer->new_pages))
2230 continue;
2231
2232 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2233 list) {
2234 list_del_init(&bpage->list);
2235 free_buffer_page(bpage);
2236 }
2237 }
2238 out_err_unlock:
2239 atomic_dec(&buffer->resizing);
2240 mutex_unlock(&buffer->mutex);
2241 return err;
2242}
2243EXPORT_SYMBOL_GPL(ring_buffer_resize);
2244
2245void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2246{
2247 mutex_lock(&buffer->mutex);
2248 if (val)
2249 buffer->flags |= RB_FL_OVERWRITE;
2250 else
2251 buffer->flags &= ~RB_FL_OVERWRITE;
2252 mutex_unlock(&buffer->mutex);
2253}
2254EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2255
2256static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2257{
2258 return bpage->page->data + index;
2259}
2260
2261static __always_inline struct ring_buffer_event *
2262rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2263{
2264 return __rb_page_index(cpu_buffer->reader_page,
2265 cpu_buffer->reader_page->read);
2266}
2267
2268static struct ring_buffer_event *
2269rb_iter_head_event(struct ring_buffer_iter *iter)
2270{
2271 struct ring_buffer_event *event;
2272 struct buffer_page *iter_head_page = iter->head_page;
2273 unsigned long commit;
2274 unsigned length;
2275
2276 if (iter->head != iter->next_event)
2277 return iter->event;
2278
2279 /*
2280 * When the writer goes across pages, it issues a cmpxchg which
2281 * is a mb(), which will synchronize with the rmb here.
2282 * (see rb_tail_page_update() and __rb_reserve_next())
2283 */
2284 commit = rb_page_commit(iter_head_page);
2285 smp_rmb();
2286
2287 /* An event needs to be at least 8 bytes in size */
2288 if (iter->head > commit - 8)
2289 goto reset;
2290
2291 event = __rb_page_index(iter_head_page, iter->head);
2292 length = rb_event_length(event);
2293
2294 /*
2295 * READ_ONCE() doesn't work on functions and we don't want the
2296 * compiler doing any crazy optimizations with length.
2297 */
2298 barrier();
2299
2300 if ((iter->head + length) > commit || length > iter->event_size)
2301 /* Writer corrupted the read? */
2302 goto reset;
2303
2304 memcpy(iter->event, event, length);
2305 /*
2306 * If the page stamp is still the same after this rmb() then the
2307 * event was safely copied without the writer entering the page.
2308 */
2309 smp_rmb();
2310
2311 /* Make sure the page didn't change since we read this */
2312 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2313 commit > rb_page_commit(iter_head_page))
2314 goto reset;
2315
2316 iter->next_event = iter->head + length;
2317 return iter->event;
2318 reset:
2319 /* Reset to the beginning */
2320 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2321 iter->head = 0;
2322 iter->next_event = 0;
2323 iter->missed_events = 1;
2324 return NULL;
2325}
2326
2327/* Size is determined by what has been committed */
2328static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2329{
2330 return rb_page_commit(bpage);
2331}
2332
2333static __always_inline unsigned
2334rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2335{
2336 return rb_page_commit(cpu_buffer->commit_page);
2337}
2338
2339static __always_inline unsigned
2340rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
2341{
2342 unsigned long addr = (unsigned long)event;
2343
2344 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
2345
2346 return addr - BUF_PAGE_HDR_SIZE;
2347}
2348
2349static void rb_inc_iter(struct ring_buffer_iter *iter)
2350{
2351 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2352
2353 /*
2354 * The iterator could be on the reader page (it starts there).
2355 * But the head could have moved, since the reader was
2356 * found. Check for this case and assign the iterator
2357 * to the head page instead of next.
2358 */
2359 if (iter->head_page == cpu_buffer->reader_page)
2360 iter->head_page = rb_set_head_page(cpu_buffer);
2361 else
2362 rb_inc_page(&iter->head_page);
2363
2364 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2365 iter->head = 0;
2366 iter->next_event = 0;
2367}
2368
2369/*
2370 * rb_handle_head_page - writer hit the head page
2371 *
2372 * Returns: +1 to retry page
2373 * 0 to continue
2374 * -1 on error
2375 */
2376static int
2377rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2378 struct buffer_page *tail_page,
2379 struct buffer_page *next_page)
2380{
2381 struct buffer_page *new_head;
2382 int entries;
2383 int type;
2384 int ret;
2385
2386 entries = rb_page_entries(next_page);
2387
2388 /*
2389 * The hard part is here. We need to move the head
2390 * forward, and protect against both readers on
2391 * other CPUs and writers coming in via interrupts.
2392 */
2393 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2394 RB_PAGE_HEAD);
2395
2396 /*
2397 * type can be one of four:
2398 * NORMAL - an interrupt already moved it for us
2399 * HEAD - we are the first to get here.
2400 * UPDATE - we are the interrupt interrupting
2401 * a current move.
2402 * MOVED - a reader on another CPU moved the next
2403 * pointer to its reader page. Give up
2404 * and try again.
2405 */
2406
2407 switch (type) {
2408 case RB_PAGE_HEAD:
2409 /*
2410 * We changed the head to UPDATE, thus
2411 * it is our responsibility to update
2412 * the counters.
2413 */
2414 local_add(entries, &cpu_buffer->overrun);
2415 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
2416 local_inc(&cpu_buffer->pages_lost);
2417
2418 /*
2419 * The entries will be zeroed out when we move the
2420 * tail page.
2421 */
2422
2423 /* still more to do */
2424 break;
2425
2426 case RB_PAGE_UPDATE:
2427 /*
2428 * This is an interrupt that interrupt the
2429 * previous update. Still more to do.
2430 */
2431 break;
2432 case RB_PAGE_NORMAL:
2433 /*
2434 * An interrupt came in before the update
2435 * and processed this for us.
2436 * Nothing left to do.
2437 */
2438 return 1;
2439 case RB_PAGE_MOVED:
2440 /*
2441 * The reader is on another CPU and just did
2442 * a swap with our next_page.
2443 * Try again.
2444 */
2445 return 1;
2446 default:
2447 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2448 return -1;
2449 }
2450
2451 /*
2452 * Now that we are here, the old head pointer is
2453 * set to UPDATE. This will keep the reader from
2454 * swapping the head page with the reader page.
2455 * The reader (on another CPU) will spin till
2456 * we are finished.
2457 *
2458 * We just need to protect against interrupts
2459 * doing the job. We will set the next pointer
2460 * to HEAD. After that, we set the old pointer
2461 * to NORMAL, but only if it was HEAD before.
2462 * otherwise we are an interrupt, and only
2463 * want the outer most commit to reset it.
2464 */
2465 new_head = next_page;
2466 rb_inc_page(&new_head);
2467
2468 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2469 RB_PAGE_NORMAL);
2470
2471 /*
2472 * Valid returns are:
2473 * HEAD - an interrupt came in and already set it.
2474 * NORMAL - One of two things:
2475 * 1) We really set it.
2476 * 2) A bunch of interrupts came in and moved
2477 * the page forward again.
2478 */
2479 switch (ret) {
2480 case RB_PAGE_HEAD:
2481 case RB_PAGE_NORMAL:
2482 /* OK */
2483 break;
2484 default:
2485 RB_WARN_ON(cpu_buffer, 1);
2486 return -1;
2487 }
2488
2489 /*
2490 * It is possible that an interrupt came in,
2491 * set the head up, then more interrupts came in
2492 * and moved it again. When we get back here,
2493 * the page would have been set to NORMAL but we
2494 * just set it back to HEAD.
2495 *
2496 * How do you detect this? Well, if that happened
2497 * the tail page would have moved.
2498 */
2499 if (ret == RB_PAGE_NORMAL) {
2500 struct buffer_page *buffer_tail_page;
2501
2502 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2503 /*
2504 * If the tail had moved passed next, then we need
2505 * to reset the pointer.
2506 */
2507 if (buffer_tail_page != tail_page &&
2508 buffer_tail_page != next_page)
2509 rb_head_page_set_normal(cpu_buffer, new_head,
2510 next_page,
2511 RB_PAGE_HEAD);
2512 }
2513
2514 /*
2515 * If this was the outer most commit (the one that
2516 * changed the original pointer from HEAD to UPDATE),
2517 * then it is up to us to reset it to NORMAL.
2518 */
2519 if (type == RB_PAGE_HEAD) {
2520 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2521 tail_page,
2522 RB_PAGE_UPDATE);
2523 if (RB_WARN_ON(cpu_buffer,
2524 ret != RB_PAGE_UPDATE))
2525 return -1;
2526 }
2527
2528 return 0;
2529}
2530
2531static inline void
2532rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2533 unsigned long tail, struct rb_event_info *info)
2534{
2535 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
2536 struct buffer_page *tail_page = info->tail_page;
2537 struct ring_buffer_event *event;
2538 unsigned long length = info->length;
2539
2540 /*
2541 * Only the event that crossed the page boundary
2542 * must fill the old tail_page with padding.
2543 */
2544 if (tail >= bsize) {
2545 /*
2546 * If the page was filled, then we still need
2547 * to update the real_end. Reset it to zero
2548 * and the reader will ignore it.
2549 */
2550 if (tail == bsize)
2551 tail_page->real_end = 0;
2552
2553 local_sub(length, &tail_page->write);
2554 return;
2555 }
2556
2557 event = __rb_page_index(tail_page, tail);
2558
2559 /*
2560 * Save the original length to the meta data.
2561 * This will be used by the reader to add lost event
2562 * counter.
2563 */
2564 tail_page->real_end = tail;
2565
2566 /*
2567 * If this event is bigger than the minimum size, then
2568 * we need to be careful that we don't subtract the
2569 * write counter enough to allow another writer to slip
2570 * in on this page.
2571 * We put in a discarded commit instead, to make sure
2572 * that this space is not used again, and this space will
2573 * not be accounted into 'entries_bytes'.
2574 *
2575 * If we are less than the minimum size, we don't need to
2576 * worry about it.
2577 */
2578 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
2579 /* No room for any events */
2580
2581 /* Mark the rest of the page with padding */
2582 rb_event_set_padding(event);
2583
2584 /* Make sure the padding is visible before the write update */
2585 smp_wmb();
2586
2587 /* Set the write back to the previous setting */
2588 local_sub(length, &tail_page->write);
2589 return;
2590 }
2591
2592 /* Put in a discarded event */
2593 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
2594 event->type_len = RINGBUF_TYPE_PADDING;
2595 /* time delta must be non zero */
2596 event->time_delta = 1;
2597
2598 /* account for padding bytes */
2599 local_add(bsize - tail, &cpu_buffer->entries_bytes);
2600
2601 /* Make sure the padding is visible before the tail_page->write update */
2602 smp_wmb();
2603
2604 /* Set write to end of buffer */
2605 length = (tail + length) - bsize;
2606 local_sub(length, &tail_page->write);
2607}
2608
2609static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2610
2611/*
2612 * This is the slow path, force gcc not to inline it.
2613 */
2614static noinline struct ring_buffer_event *
2615rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2616 unsigned long tail, struct rb_event_info *info)
2617{
2618 struct buffer_page *tail_page = info->tail_page;
2619 struct buffer_page *commit_page = cpu_buffer->commit_page;
2620 struct trace_buffer *buffer = cpu_buffer->buffer;
2621 struct buffer_page *next_page;
2622 int ret;
2623
2624 next_page = tail_page;
2625
2626 rb_inc_page(&next_page);
2627
2628 /*
2629 * If for some reason, we had an interrupt storm that made
2630 * it all the way around the buffer, bail, and warn
2631 * about it.
2632 */
2633 if (unlikely(next_page == commit_page)) {
2634 local_inc(&cpu_buffer->commit_overrun);
2635 goto out_reset;
2636 }
2637
2638 /*
2639 * This is where the fun begins!
2640 *
2641 * We are fighting against races between a reader that
2642 * could be on another CPU trying to swap its reader
2643 * page with the buffer head.
2644 *
2645 * We are also fighting against interrupts coming in and
2646 * moving the head or tail on us as well.
2647 *
2648 * If the next page is the head page then we have filled
2649 * the buffer, unless the commit page is still on the
2650 * reader page.
2651 */
2652 if (rb_is_head_page(next_page, &tail_page->list)) {
2653
2654 /*
2655 * If the commit is not on the reader page, then
2656 * move the header page.
2657 */
2658 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2659 /*
2660 * If we are not in overwrite mode,
2661 * this is easy, just stop here.
2662 */
2663 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2664 local_inc(&cpu_buffer->dropped_events);
2665 goto out_reset;
2666 }
2667
2668 ret = rb_handle_head_page(cpu_buffer,
2669 tail_page,
2670 next_page);
2671 if (ret < 0)
2672 goto out_reset;
2673 if (ret)
2674 goto out_again;
2675 } else {
2676 /*
2677 * We need to be careful here too. The
2678 * commit page could still be on the reader
2679 * page. We could have a small buffer, and
2680 * have filled up the buffer with events
2681 * from interrupts and such, and wrapped.
2682 *
2683 * Note, if the tail page is also on the
2684 * reader_page, we let it move out.
2685 */
2686 if (unlikely((cpu_buffer->commit_page !=
2687 cpu_buffer->tail_page) &&
2688 (cpu_buffer->commit_page ==
2689 cpu_buffer->reader_page))) {
2690 local_inc(&cpu_buffer->commit_overrun);
2691 goto out_reset;
2692 }
2693 }
2694 }
2695
2696 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2697
2698 out_again:
2699
2700 rb_reset_tail(cpu_buffer, tail, info);
2701
2702 /* Commit what we have for now. */
2703 rb_end_commit(cpu_buffer);
2704 /* rb_end_commit() decs committing */
2705 local_inc(&cpu_buffer->committing);
2706
2707 /* fail and let the caller try again */
2708 return ERR_PTR(-EAGAIN);
2709
2710 out_reset:
2711 /* reset write */
2712 rb_reset_tail(cpu_buffer, tail, info);
2713
2714 return NULL;
2715}
2716
2717/* Slow path */
2718static struct ring_buffer_event *
2719rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2720 struct ring_buffer_event *event, u64 delta, bool abs)
2721{
2722 if (abs)
2723 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2724 else
2725 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2726
2727 /* Not the first event on the page, or not delta? */
2728 if (abs || rb_event_index(cpu_buffer, event)) {
2729 event->time_delta = delta & TS_MASK;
2730 event->array[0] = delta >> TS_SHIFT;
2731 } else {
2732 /* nope, just zero it */
2733 event->time_delta = 0;
2734 event->array[0] = 0;
2735 }
2736
2737 return skip_time_extend(event);
2738}
2739
2740#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2741static inline bool sched_clock_stable(void)
2742{
2743 return true;
2744}
2745#endif
2746
2747static void
2748rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2749 struct rb_event_info *info)
2750{
2751 u64 write_stamp;
2752
2753 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2754 (unsigned long long)info->delta,
2755 (unsigned long long)info->ts,
2756 (unsigned long long)info->before,
2757 (unsigned long long)info->after,
2758 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
2759 sched_clock_stable() ? "" :
2760 "If you just came from a suspend/resume,\n"
2761 "please switch to the trace global clock:\n"
2762 " echo global > /sys/kernel/tracing/trace_clock\n"
2763 "or add trace_clock=global to the kernel command line\n");
2764}
2765
2766static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2767 struct ring_buffer_event **event,
2768 struct rb_event_info *info,
2769 u64 *delta,
2770 unsigned int *length)
2771{
2772 bool abs = info->add_timestamp &
2773 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2774
2775 if (unlikely(info->delta > (1ULL << 59))) {
2776 /*
2777 * Some timers can use more than 59 bits, and when a timestamp
2778 * is added to the buffer, it will lose those bits.
2779 */
2780 if (abs && (info->ts & TS_MSB)) {
2781 info->delta &= ABS_TS_MASK;
2782
2783 /* did the clock go backwards */
2784 } else if (info->before == info->after && info->before > info->ts) {
2785 /* not interrupted */
2786 static int once;
2787
2788 /*
2789 * This is possible with a recalibrating of the TSC.
2790 * Do not produce a call stack, but just report it.
2791 */
2792 if (!once) {
2793 once++;
2794 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2795 info->before, info->ts);
2796 }
2797 } else
2798 rb_check_timestamp(cpu_buffer, info);
2799 if (!abs)
2800 info->delta = 0;
2801 }
2802 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
2803 *length -= RB_LEN_TIME_EXTEND;
2804 *delta = 0;
2805}
2806
2807/**
2808 * rb_update_event - update event type and data
2809 * @cpu_buffer: The per cpu buffer of the @event
2810 * @event: the event to update
2811 * @info: The info to update the @event with (contains length and delta)
2812 *
2813 * Update the type and data fields of the @event. The length
2814 * is the actual size that is written to the ring buffer,
2815 * and with this, we can determine what to place into the
2816 * data field.
2817 */
2818static void
2819rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2820 struct ring_buffer_event *event,
2821 struct rb_event_info *info)
2822{
2823 unsigned length = info->length;
2824 u64 delta = info->delta;
2825 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2826
2827 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2828 cpu_buffer->event_stamp[nest] = info->ts;
2829
2830 /*
2831 * If we need to add a timestamp, then we
2832 * add it to the start of the reserved space.
2833 */
2834 if (unlikely(info->add_timestamp))
2835 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2836
2837 event->time_delta = delta;
2838 length -= RB_EVNT_HDR_SIZE;
2839 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2840 event->type_len = 0;
2841 event->array[0] = length;
2842 } else
2843 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2844}
2845
2846static unsigned rb_calculate_event_length(unsigned length)
2847{
2848 struct ring_buffer_event event; /* Used only for sizeof array */
2849
2850 /* zero length can cause confusions */
2851 if (!length)
2852 length++;
2853
2854 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2855 length += sizeof(event.array[0]);
2856
2857 length += RB_EVNT_HDR_SIZE;
2858 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2859
2860 /*
2861 * In case the time delta is larger than the 27 bits for it
2862 * in the header, we need to add a timestamp. If another
2863 * event comes in when trying to discard this one to increase
2864 * the length, then the timestamp will be added in the allocated
2865 * space of this event. If length is bigger than the size needed
2866 * for the TIME_EXTEND, then padding has to be used. The events
2867 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2868 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2869 * As length is a multiple of 4, we only need to worry if it
2870 * is 12 (RB_LEN_TIME_EXTEND + 4).
2871 */
2872 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2873 length += RB_ALIGNMENT;
2874
2875 return length;
2876}
2877
2878static inline bool
2879rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2880 struct ring_buffer_event *event)
2881{
2882 unsigned long new_index, old_index;
2883 struct buffer_page *bpage;
2884 unsigned long addr;
2885
2886 new_index = rb_event_index(cpu_buffer, event);
2887 old_index = new_index + rb_event_ts_length(event);
2888 addr = (unsigned long)event;
2889 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
2890
2891 bpage = READ_ONCE(cpu_buffer->tail_page);
2892
2893 /*
2894 * Make sure the tail_page is still the same and
2895 * the next write location is the end of this event
2896 */
2897 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2898 unsigned long write_mask =
2899 local_read(&bpage->write) & ~RB_WRITE_MASK;
2900 unsigned long event_length = rb_event_length(event);
2901
2902 /*
2903 * For the before_stamp to be different than the write_stamp
2904 * to make sure that the next event adds an absolute
2905 * value and does not rely on the saved write stamp, which
2906 * is now going to be bogus.
2907 *
2908 * By setting the before_stamp to zero, the next event
2909 * is not going to use the write_stamp and will instead
2910 * create an absolute timestamp. This means there's no
2911 * reason to update the wirte_stamp!
2912 */
2913 rb_time_set(&cpu_buffer->before_stamp, 0);
2914
2915 /*
2916 * If an event were to come in now, it would see that the
2917 * write_stamp and the before_stamp are different, and assume
2918 * that this event just added itself before updating
2919 * the write stamp. The interrupting event will fix the
2920 * write stamp for us, and use an absolute timestamp.
2921 */
2922
2923 /*
2924 * This is on the tail page. It is possible that
2925 * a write could come in and move the tail page
2926 * and write to the next page. That is fine
2927 * because we just shorten what is on this page.
2928 */
2929 old_index += write_mask;
2930 new_index += write_mask;
2931
2932 /* caution: old_index gets updated on cmpxchg failure */
2933 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
2934 /* update counters */
2935 local_sub(event_length, &cpu_buffer->entries_bytes);
2936 return true;
2937 }
2938 }
2939
2940 /* could not discard */
2941 return false;
2942}
2943
2944static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2945{
2946 local_inc(&cpu_buffer->committing);
2947 local_inc(&cpu_buffer->commits);
2948}
2949
2950static __always_inline void
2951rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2952{
2953 unsigned long max_count;
2954
2955 /*
2956 * We only race with interrupts and NMIs on this CPU.
2957 * If we own the commit event, then we can commit
2958 * all others that interrupted us, since the interruptions
2959 * are in stack format (they finish before they come
2960 * back to us). This allows us to do a simple loop to
2961 * assign the commit to the tail.
2962 */
2963 again:
2964 max_count = cpu_buffer->nr_pages * 100;
2965
2966 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2967 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2968 return;
2969 if (RB_WARN_ON(cpu_buffer,
2970 rb_is_reader_page(cpu_buffer->tail_page)))
2971 return;
2972 /*
2973 * No need for a memory barrier here, as the update
2974 * of the tail_page did it for this page.
2975 */
2976 local_set(&cpu_buffer->commit_page->page->commit,
2977 rb_page_write(cpu_buffer->commit_page));
2978 rb_inc_page(&cpu_buffer->commit_page);
2979 /* add barrier to keep gcc from optimizing too much */
2980 barrier();
2981 }
2982 while (rb_commit_index(cpu_buffer) !=
2983 rb_page_write(cpu_buffer->commit_page)) {
2984
2985 /* Make sure the readers see the content of what is committed. */
2986 smp_wmb();
2987 local_set(&cpu_buffer->commit_page->page->commit,
2988 rb_page_write(cpu_buffer->commit_page));
2989 RB_WARN_ON(cpu_buffer,
2990 local_read(&cpu_buffer->commit_page->page->commit) &
2991 ~RB_WRITE_MASK);
2992 barrier();
2993 }
2994
2995 /* again, keep gcc from optimizing */
2996 barrier();
2997
2998 /*
2999 * If an interrupt came in just after the first while loop
3000 * and pushed the tail page forward, we will be left with
3001 * a dangling commit that will never go forward.
3002 */
3003 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3004 goto again;
3005}
3006
3007static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3008{
3009 unsigned long commits;
3010
3011 if (RB_WARN_ON(cpu_buffer,
3012 !local_read(&cpu_buffer->committing)))
3013 return;
3014
3015 again:
3016 commits = local_read(&cpu_buffer->commits);
3017 /* synchronize with interrupts */
3018 barrier();
3019 if (local_read(&cpu_buffer->committing) == 1)
3020 rb_set_commit_to_write(cpu_buffer);
3021
3022 local_dec(&cpu_buffer->committing);
3023
3024 /* synchronize with interrupts */
3025 barrier();
3026
3027 /*
3028 * Need to account for interrupts coming in between the
3029 * updating of the commit page and the clearing of the
3030 * committing counter.
3031 */
3032 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3033 !local_read(&cpu_buffer->committing)) {
3034 local_inc(&cpu_buffer->committing);
3035 goto again;
3036 }
3037}
3038
3039static inline void rb_event_discard(struct ring_buffer_event *event)
3040{
3041 if (extended_time(event))
3042 event = skip_time_extend(event);
3043
3044 /* array[0] holds the actual length for the discarded event */
3045 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3046 event->type_len = RINGBUF_TYPE_PADDING;
3047 /* time delta must be non zero */
3048 if (!event->time_delta)
3049 event->time_delta = 1;
3050}
3051
3052static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3053{
3054 local_inc(&cpu_buffer->entries);
3055 rb_end_commit(cpu_buffer);
3056}
3057
3058static __always_inline void
3059rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3060{
3061 if (buffer->irq_work.waiters_pending) {
3062 buffer->irq_work.waiters_pending = false;
3063 /* irq_work_queue() supplies it's own memory barriers */
3064 irq_work_queue(&buffer->irq_work.work);
3065 }
3066
3067 if (cpu_buffer->irq_work.waiters_pending) {
3068 cpu_buffer->irq_work.waiters_pending = false;
3069 /* irq_work_queue() supplies it's own memory barriers */
3070 irq_work_queue(&cpu_buffer->irq_work.work);
3071 }
3072
3073 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3074 return;
3075
3076 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3077 return;
3078
3079 if (!cpu_buffer->irq_work.full_waiters_pending)
3080 return;
3081
3082 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3083
3084 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3085 return;
3086
3087 cpu_buffer->irq_work.wakeup_full = true;
3088 cpu_buffer->irq_work.full_waiters_pending = false;
3089 /* irq_work_queue() supplies it's own memory barriers */
3090 irq_work_queue(&cpu_buffer->irq_work.work);
3091}
3092
3093#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3094# define do_ring_buffer_record_recursion() \
3095 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3096#else
3097# define do_ring_buffer_record_recursion() do { } while (0)
3098#endif
3099
3100/*
3101 * The lock and unlock are done within a preempt disable section.
3102 * The current_context per_cpu variable can only be modified
3103 * by the current task between lock and unlock. But it can
3104 * be modified more than once via an interrupt. To pass this
3105 * information from the lock to the unlock without having to
3106 * access the 'in_interrupt()' functions again (which do show
3107 * a bit of overhead in something as critical as function tracing,
3108 * we use a bitmask trick.
3109 *
3110 * bit 1 = NMI context
3111 * bit 2 = IRQ context
3112 * bit 3 = SoftIRQ context
3113 * bit 4 = normal context.
3114 *
3115 * This works because this is the order of contexts that can
3116 * preempt other contexts. A SoftIRQ never preempts an IRQ
3117 * context.
3118 *
3119 * When the context is determined, the corresponding bit is
3120 * checked and set (if it was set, then a recursion of that context
3121 * happened).
3122 *
3123 * On unlock, we need to clear this bit. To do so, just subtract
3124 * 1 from the current_context and AND it to itself.
3125 *
3126 * (binary)
3127 * 101 - 1 = 100
3128 * 101 & 100 = 100 (clearing bit zero)
3129 *
3130 * 1010 - 1 = 1001
3131 * 1010 & 1001 = 1000 (clearing bit 1)
3132 *
3133 * The least significant bit can be cleared this way, and it
3134 * just so happens that it is the same bit corresponding to
3135 * the current context.
3136 *
3137 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3138 * is set when a recursion is detected at the current context, and if
3139 * the TRANSITION bit is already set, it will fail the recursion.
3140 * This is needed because there's a lag between the changing of
3141 * interrupt context and updating the preempt count. In this case,
3142 * a false positive will be found. To handle this, one extra recursion
3143 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3144 * bit is already set, then it is considered a recursion and the function
3145 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3146 *
3147 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3148 * to be cleared. Even if it wasn't the context that set it. That is,
3149 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3150 * is called before preempt_count() is updated, since the check will
3151 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3152 * NMI then comes in, it will set the NMI bit, but when the NMI code
3153 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3154 * and leave the NMI bit set. But this is fine, because the interrupt
3155 * code that set the TRANSITION bit will then clear the NMI bit when it
3156 * calls trace_recursive_unlock(). If another NMI comes in, it will
3157 * set the TRANSITION bit and continue.
3158 *
3159 * Note: The TRANSITION bit only handles a single transition between context.
3160 */
3161
3162static __always_inline bool
3163trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3164{
3165 unsigned int val = cpu_buffer->current_context;
3166 int bit = interrupt_context_level();
3167
3168 bit = RB_CTX_NORMAL - bit;
3169
3170 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3171 /*
3172 * It is possible that this was called by transitioning
3173 * between interrupt context, and preempt_count() has not
3174 * been updated yet. In this case, use the TRANSITION bit.
3175 */
3176 bit = RB_CTX_TRANSITION;
3177 if (val & (1 << (bit + cpu_buffer->nest))) {
3178 do_ring_buffer_record_recursion();
3179 return true;
3180 }
3181 }
3182
3183 val |= (1 << (bit + cpu_buffer->nest));
3184 cpu_buffer->current_context = val;
3185
3186 return false;
3187}
3188
3189static __always_inline void
3190trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3191{
3192 cpu_buffer->current_context &=
3193 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3194}
3195
3196/* The recursive locking above uses 5 bits */
3197#define NESTED_BITS 5
3198
3199/**
3200 * ring_buffer_nest_start - Allow to trace while nested
3201 * @buffer: The ring buffer to modify
3202 *
3203 * The ring buffer has a safety mechanism to prevent recursion.
3204 * But there may be a case where a trace needs to be done while
3205 * tracing something else. In this case, calling this function
3206 * will allow this function to nest within a currently active
3207 * ring_buffer_lock_reserve().
3208 *
3209 * Call this function before calling another ring_buffer_lock_reserve() and
3210 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3211 */
3212void ring_buffer_nest_start(struct trace_buffer *buffer)
3213{
3214 struct ring_buffer_per_cpu *cpu_buffer;
3215 int cpu;
3216
3217 /* Enabled by ring_buffer_nest_end() */
3218 preempt_disable_notrace();
3219 cpu = raw_smp_processor_id();
3220 cpu_buffer = buffer->buffers[cpu];
3221 /* This is the shift value for the above recursive locking */
3222 cpu_buffer->nest += NESTED_BITS;
3223}
3224
3225/**
3226 * ring_buffer_nest_end - Allow to trace while nested
3227 * @buffer: The ring buffer to modify
3228 *
3229 * Must be called after ring_buffer_nest_start() and after the
3230 * ring_buffer_unlock_commit().
3231 */
3232void ring_buffer_nest_end(struct trace_buffer *buffer)
3233{
3234 struct ring_buffer_per_cpu *cpu_buffer;
3235 int cpu;
3236
3237 /* disabled by ring_buffer_nest_start() */
3238 cpu = raw_smp_processor_id();
3239 cpu_buffer = buffer->buffers[cpu];
3240 /* This is the shift value for the above recursive locking */
3241 cpu_buffer->nest -= NESTED_BITS;
3242 preempt_enable_notrace();
3243}
3244
3245/**
3246 * ring_buffer_unlock_commit - commit a reserved
3247 * @buffer: The buffer to commit to
3248 *
3249 * This commits the data to the ring buffer, and releases any locks held.
3250 *
3251 * Must be paired with ring_buffer_lock_reserve.
3252 */
3253int ring_buffer_unlock_commit(struct trace_buffer *buffer)
3254{
3255 struct ring_buffer_per_cpu *cpu_buffer;
3256 int cpu = raw_smp_processor_id();
3257
3258 cpu_buffer = buffer->buffers[cpu];
3259
3260 rb_commit(cpu_buffer);
3261
3262 rb_wakeups(buffer, cpu_buffer);
3263
3264 trace_recursive_unlock(cpu_buffer);
3265
3266 preempt_enable_notrace();
3267
3268 return 0;
3269}
3270EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3271
3272/* Special value to validate all deltas on a page. */
3273#define CHECK_FULL_PAGE 1L
3274
3275#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3276
3277static const char *show_irq_str(int bits)
3278{
3279 const char *type[] = {
3280 ".", // 0
3281 "s", // 1
3282 "h", // 2
3283 "Hs", // 3
3284 "n", // 4
3285 "Ns", // 5
3286 "Nh", // 6
3287 "NHs", // 7
3288 };
3289
3290 return type[bits];
3291}
3292
3293/* Assume this is an trace event */
3294static const char *show_flags(struct ring_buffer_event *event)
3295{
3296 struct trace_entry *entry;
3297 int bits = 0;
3298
3299 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3300 return "X";
3301
3302 entry = ring_buffer_event_data(event);
3303
3304 if (entry->flags & TRACE_FLAG_SOFTIRQ)
3305 bits |= 1;
3306
3307 if (entry->flags & TRACE_FLAG_HARDIRQ)
3308 bits |= 2;
3309
3310 if (entry->flags & TRACE_FLAG_NMI)
3311 bits |= 4;
3312
3313 return show_irq_str(bits);
3314}
3315
3316static const char *show_irq(struct ring_buffer_event *event)
3317{
3318 struct trace_entry *entry;
3319
3320 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3321 return "";
3322
3323 entry = ring_buffer_event_data(event);
3324 if (entry->flags & TRACE_FLAG_IRQS_OFF)
3325 return "d";
3326 return "";
3327}
3328
3329static const char *show_interrupt_level(void)
3330{
3331 unsigned long pc = preempt_count();
3332 unsigned char level = 0;
3333
3334 if (pc & SOFTIRQ_OFFSET)
3335 level |= 1;
3336
3337 if (pc & HARDIRQ_MASK)
3338 level |= 2;
3339
3340 if (pc & NMI_MASK)
3341 level |= 4;
3342
3343 return show_irq_str(level);
3344}
3345
3346static void dump_buffer_page(struct buffer_data_page *bpage,
3347 struct rb_event_info *info,
3348 unsigned long tail)
3349{
3350 struct ring_buffer_event *event;
3351 u64 ts, delta;
3352 int e;
3353
3354 ts = bpage->time_stamp;
3355 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3356
3357 for (e = 0; e < tail; e += rb_event_length(event)) {
3358
3359 event = (struct ring_buffer_event *)(bpage->data + e);
3360
3361 switch (event->type_len) {
3362
3363 case RINGBUF_TYPE_TIME_EXTEND:
3364 delta = rb_event_time_stamp(event);
3365 ts += delta;
3366 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
3367 e, ts, delta);
3368 break;
3369
3370 case RINGBUF_TYPE_TIME_STAMP:
3371 delta = rb_event_time_stamp(event);
3372 ts = rb_fix_abs_ts(delta, ts);
3373 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
3374 e, ts, delta);
3375 break;
3376
3377 case RINGBUF_TYPE_PADDING:
3378 ts += event->time_delta;
3379 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
3380 e, ts, event->time_delta);
3381 break;
3382
3383 case RINGBUF_TYPE_DATA:
3384 ts += event->time_delta;
3385 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
3386 e, ts, event->time_delta,
3387 show_flags(event), show_irq(event));
3388 break;
3389
3390 default:
3391 break;
3392 }
3393 }
3394 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
3395}
3396
3397static DEFINE_PER_CPU(atomic_t, checking);
3398static atomic_t ts_dump;
3399
3400#define buffer_warn_return(fmt, ...) \
3401 do { \
3402 /* If another report is happening, ignore this one */ \
3403 if (atomic_inc_return(&ts_dump) != 1) { \
3404 atomic_dec(&ts_dump); \
3405 goto out; \
3406 } \
3407 atomic_inc(&cpu_buffer->record_disabled); \
3408 pr_warn(fmt, ##__VA_ARGS__); \
3409 dump_buffer_page(bpage, info, tail); \
3410 atomic_dec(&ts_dump); \
3411 /* There's some cases in boot up that this can happen */ \
3412 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
3413 /* Do not re-enable checking */ \
3414 return; \
3415 } while (0)
3416
3417/*
3418 * Check if the current event time stamp matches the deltas on
3419 * the buffer page.
3420 */
3421static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3422 struct rb_event_info *info,
3423 unsigned long tail)
3424{
3425 struct ring_buffer_event *event;
3426 struct buffer_data_page *bpage;
3427 u64 ts, delta;
3428 bool full = false;
3429 int e;
3430
3431 bpage = info->tail_page->page;
3432
3433 if (tail == CHECK_FULL_PAGE) {
3434 full = true;
3435 tail = local_read(&bpage->commit);
3436 } else if (info->add_timestamp &
3437 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3438 /* Ignore events with absolute time stamps */
3439 return;
3440 }
3441
3442 /*
3443 * Do not check the first event (skip possible extends too).
3444 * Also do not check if previous events have not been committed.
3445 */
3446 if (tail <= 8 || tail > local_read(&bpage->commit))
3447 return;
3448
3449 /*
3450 * If this interrupted another event,
3451 */
3452 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3453 goto out;
3454
3455 ts = bpage->time_stamp;
3456
3457 for (e = 0; e < tail; e += rb_event_length(event)) {
3458
3459 event = (struct ring_buffer_event *)(bpage->data + e);
3460
3461 switch (event->type_len) {
3462
3463 case RINGBUF_TYPE_TIME_EXTEND:
3464 delta = rb_event_time_stamp(event);
3465 ts += delta;
3466 break;
3467
3468 case RINGBUF_TYPE_TIME_STAMP:
3469 delta = rb_event_time_stamp(event);
3470 delta = rb_fix_abs_ts(delta, ts);
3471 if (delta < ts) {
3472 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
3473 cpu_buffer->cpu, ts, delta);
3474 }
3475 ts = delta;
3476 break;
3477
3478 case RINGBUF_TYPE_PADDING:
3479 if (event->time_delta == 1)
3480 break;
3481 fallthrough;
3482 case RINGBUF_TYPE_DATA:
3483 ts += event->time_delta;
3484 break;
3485
3486 default:
3487 RB_WARN_ON(cpu_buffer, 1);
3488 }
3489 }
3490 if ((full && ts > info->ts) ||
3491 (!full && ts + info->delta != info->ts)) {
3492 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
3493 cpu_buffer->cpu,
3494 ts + info->delta, info->ts, info->delta,
3495 info->before, info->after,
3496 full ? " (full)" : "", show_interrupt_level());
3497 }
3498out:
3499 atomic_dec(this_cpu_ptr(&checking));
3500}
3501#else
3502static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3503 struct rb_event_info *info,
3504 unsigned long tail)
3505{
3506}
3507#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3508
3509static struct ring_buffer_event *
3510__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3511 struct rb_event_info *info)
3512{
3513 struct ring_buffer_event *event;
3514 struct buffer_page *tail_page;
3515 unsigned long tail, write, w;
3516
3517 /* Don't let the compiler play games with cpu_buffer->tail_page */
3518 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3519
3520 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3521 barrier();
3522 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3523 rb_time_read(&cpu_buffer->write_stamp, &info->after);
3524 barrier();
3525 info->ts = rb_time_stamp(cpu_buffer->buffer);
3526
3527 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3528 info->delta = info->ts;
3529 } else {
3530 /*
3531 * If interrupting an event time update, we may need an
3532 * absolute timestamp.
3533 * Don't bother if this is the start of a new page (w == 0).
3534 */
3535 if (!w) {
3536 /* Use the sub-buffer timestamp */
3537 info->delta = 0;
3538 } else if (unlikely(info->before != info->after)) {
3539 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3540 info->length += RB_LEN_TIME_EXTEND;
3541 } else {
3542 info->delta = info->ts - info->after;
3543 if (unlikely(test_time_stamp(info->delta))) {
3544 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3545 info->length += RB_LEN_TIME_EXTEND;
3546 }
3547 }
3548 }
3549
3550 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3551
3552 /*C*/ write = local_add_return(info->length, &tail_page->write);
3553
3554 /* set write to only the index of the write */
3555 write &= RB_WRITE_MASK;
3556
3557 tail = write - info->length;
3558
3559 /* See if we shot pass the end of this buffer page */
3560 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
3561 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3562 return rb_move_tail(cpu_buffer, tail, info);
3563 }
3564
3565 if (likely(tail == w)) {
3566 /* Nothing interrupted us between A and C */
3567 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3568 /*
3569 * If something came in between C and D, the write stamp
3570 * may now not be in sync. But that's fine as the before_stamp
3571 * will be different and then next event will just be forced
3572 * to use an absolute timestamp.
3573 */
3574 if (likely(!(info->add_timestamp &
3575 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3576 /* This did not interrupt any time update */
3577 info->delta = info->ts - info->after;
3578 else
3579 /* Just use full timestamp for interrupting event */
3580 info->delta = info->ts;
3581 check_buffer(cpu_buffer, info, tail);
3582 } else {
3583 u64 ts;
3584 /* SLOW PATH - Interrupted between A and C */
3585
3586 /* Save the old before_stamp */
3587 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3588
3589 /*
3590 * Read a new timestamp and update the before_stamp to make
3591 * the next event after this one force using an absolute
3592 * timestamp. This is in case an interrupt were to come in
3593 * between E and F.
3594 */
3595 ts = rb_time_stamp(cpu_buffer->buffer);
3596 rb_time_set(&cpu_buffer->before_stamp, ts);
3597
3598 barrier();
3599 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
3600 barrier();
3601 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3602 info->after == info->before && info->after < ts) {
3603 /*
3604 * Nothing came after this event between C and F, it is
3605 * safe to use info->after for the delta as it
3606 * matched info->before and is still valid.
3607 */
3608 info->delta = ts - info->after;
3609 } else {
3610 /*
3611 * Interrupted between C and F:
3612 * Lost the previous events time stamp. Just set the
3613 * delta to zero, and this will be the same time as
3614 * the event this event interrupted. And the events that
3615 * came after this will still be correct (as they would
3616 * have built their delta on the previous event.
3617 */
3618 info->delta = 0;
3619 }
3620 info->ts = ts;
3621 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3622 }
3623
3624 /*
3625 * If this is the first commit on the page, then it has the same
3626 * timestamp as the page itself.
3627 */
3628 if (unlikely(!tail && !(info->add_timestamp &
3629 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3630 info->delta = 0;
3631
3632 /* We reserved something on the buffer */
3633
3634 event = __rb_page_index(tail_page, tail);
3635 rb_update_event(cpu_buffer, event, info);
3636
3637 local_inc(&tail_page->entries);
3638
3639 /*
3640 * If this is the first commit on the page, then update
3641 * its timestamp.
3642 */
3643 if (unlikely(!tail))
3644 tail_page->page->time_stamp = info->ts;
3645
3646 /* account for these added bytes */
3647 local_add(info->length, &cpu_buffer->entries_bytes);
3648
3649 return event;
3650}
3651
3652static __always_inline struct ring_buffer_event *
3653rb_reserve_next_event(struct trace_buffer *buffer,
3654 struct ring_buffer_per_cpu *cpu_buffer,
3655 unsigned long length)
3656{
3657 struct ring_buffer_event *event;
3658 struct rb_event_info info;
3659 int nr_loops = 0;
3660 int add_ts_default;
3661
3662 /* ring buffer does cmpxchg, make sure it is safe in NMI context */
3663 if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
3664 (unlikely(in_nmi()))) {
3665 return NULL;
3666 }
3667
3668 rb_start_commit(cpu_buffer);
3669 /* The commit page can not change after this */
3670
3671#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3672 /*
3673 * Due to the ability to swap a cpu buffer from a buffer
3674 * it is possible it was swapped before we committed.
3675 * (committing stops a swap). We check for it here and
3676 * if it happened, we have to fail the write.
3677 */
3678 barrier();
3679 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3680 local_dec(&cpu_buffer->committing);
3681 local_dec(&cpu_buffer->commits);
3682 return NULL;
3683 }
3684#endif
3685
3686 info.length = rb_calculate_event_length(length);
3687
3688 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3689 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3690 info.length += RB_LEN_TIME_EXTEND;
3691 if (info.length > cpu_buffer->buffer->max_data_size)
3692 goto out_fail;
3693 } else {
3694 add_ts_default = RB_ADD_STAMP_NONE;
3695 }
3696
3697 again:
3698 info.add_timestamp = add_ts_default;
3699 info.delta = 0;
3700
3701 /*
3702 * We allow for interrupts to reenter here and do a trace.
3703 * If one does, it will cause this original code to loop
3704 * back here. Even with heavy interrupts happening, this
3705 * should only happen a few times in a row. If this happens
3706 * 1000 times in a row, there must be either an interrupt
3707 * storm or we have something buggy.
3708 * Bail!
3709 */
3710 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3711 goto out_fail;
3712
3713 event = __rb_reserve_next(cpu_buffer, &info);
3714
3715 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3716 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3717 info.length -= RB_LEN_TIME_EXTEND;
3718 goto again;
3719 }
3720
3721 if (likely(event))
3722 return event;
3723 out_fail:
3724 rb_end_commit(cpu_buffer);
3725 return NULL;
3726}
3727
3728/**
3729 * ring_buffer_lock_reserve - reserve a part of the buffer
3730 * @buffer: the ring buffer to reserve from
3731 * @length: the length of the data to reserve (excluding event header)
3732 *
3733 * Returns a reserved event on the ring buffer to copy directly to.
3734 * The user of this interface will need to get the body to write into
3735 * and can use the ring_buffer_event_data() interface.
3736 *
3737 * The length is the length of the data needed, not the event length
3738 * which also includes the event header.
3739 *
3740 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3741 * If NULL is returned, then nothing has been allocated or locked.
3742 */
3743struct ring_buffer_event *
3744ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3745{
3746 struct ring_buffer_per_cpu *cpu_buffer;
3747 struct ring_buffer_event *event;
3748 int cpu;
3749
3750 /* If we are tracing schedule, we don't want to recurse */
3751 preempt_disable_notrace();
3752
3753 if (unlikely(atomic_read(&buffer->record_disabled)))
3754 goto out;
3755
3756 cpu = raw_smp_processor_id();
3757
3758 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3759 goto out;
3760
3761 cpu_buffer = buffer->buffers[cpu];
3762
3763 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3764 goto out;
3765
3766 if (unlikely(length > buffer->max_data_size))
3767 goto out;
3768
3769 if (unlikely(trace_recursive_lock(cpu_buffer)))
3770 goto out;
3771
3772 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3773 if (!event)
3774 goto out_unlock;
3775
3776 return event;
3777
3778 out_unlock:
3779 trace_recursive_unlock(cpu_buffer);
3780 out:
3781 preempt_enable_notrace();
3782 return NULL;
3783}
3784EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3785
3786/*
3787 * Decrement the entries to the page that an event is on.
3788 * The event does not even need to exist, only the pointer
3789 * to the page it is on. This may only be called before the commit
3790 * takes place.
3791 */
3792static inline void
3793rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3794 struct ring_buffer_event *event)
3795{
3796 unsigned long addr = (unsigned long)event;
3797 struct buffer_page *bpage = cpu_buffer->commit_page;
3798 struct buffer_page *start;
3799
3800 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3801
3802 /* Do the likely case first */
3803 if (likely(bpage->page == (void *)addr)) {
3804 local_dec(&bpage->entries);
3805 return;
3806 }
3807
3808 /*
3809 * Because the commit page may be on the reader page we
3810 * start with the next page and check the end loop there.
3811 */
3812 rb_inc_page(&bpage);
3813 start = bpage;
3814 do {
3815 if (bpage->page == (void *)addr) {
3816 local_dec(&bpage->entries);
3817 return;
3818 }
3819 rb_inc_page(&bpage);
3820 } while (bpage != start);
3821
3822 /* commit not part of this buffer?? */
3823 RB_WARN_ON(cpu_buffer, 1);
3824}
3825
3826/**
3827 * ring_buffer_discard_commit - discard an event that has not been committed
3828 * @buffer: the ring buffer
3829 * @event: non committed event to discard
3830 *
3831 * Sometimes an event that is in the ring buffer needs to be ignored.
3832 * This function lets the user discard an event in the ring buffer
3833 * and then that event will not be read later.
3834 *
3835 * This function only works if it is called before the item has been
3836 * committed. It will try to free the event from the ring buffer
3837 * if another event has not been added behind it.
3838 *
3839 * If another event has been added behind it, it will set the event
3840 * up as discarded, and perform the commit.
3841 *
3842 * If this function is called, do not call ring_buffer_unlock_commit on
3843 * the event.
3844 */
3845void ring_buffer_discard_commit(struct trace_buffer *buffer,
3846 struct ring_buffer_event *event)
3847{
3848 struct ring_buffer_per_cpu *cpu_buffer;
3849 int cpu;
3850
3851 /* The event is discarded regardless */
3852 rb_event_discard(event);
3853
3854 cpu = smp_processor_id();
3855 cpu_buffer = buffer->buffers[cpu];
3856
3857 /*
3858 * This must only be called if the event has not been
3859 * committed yet. Thus we can assume that preemption
3860 * is still disabled.
3861 */
3862 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3863
3864 rb_decrement_entry(cpu_buffer, event);
3865 if (rb_try_to_discard(cpu_buffer, event))
3866 goto out;
3867
3868 out:
3869 rb_end_commit(cpu_buffer);
3870
3871 trace_recursive_unlock(cpu_buffer);
3872
3873 preempt_enable_notrace();
3874
3875}
3876EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3877
3878/**
3879 * ring_buffer_write - write data to the buffer without reserving
3880 * @buffer: The ring buffer to write to.
3881 * @length: The length of the data being written (excluding the event header)
3882 * @data: The data to write to the buffer.
3883 *
3884 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3885 * one function. If you already have the data to write to the buffer, it
3886 * may be easier to simply call this function.
3887 *
3888 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3889 * and not the length of the event which would hold the header.
3890 */
3891int ring_buffer_write(struct trace_buffer *buffer,
3892 unsigned long length,
3893 void *data)
3894{
3895 struct ring_buffer_per_cpu *cpu_buffer;
3896 struct ring_buffer_event *event;
3897 void *body;
3898 int ret = -EBUSY;
3899 int cpu;
3900
3901 preempt_disable_notrace();
3902
3903 if (atomic_read(&buffer->record_disabled))
3904 goto out;
3905
3906 cpu = raw_smp_processor_id();
3907
3908 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3909 goto out;
3910
3911 cpu_buffer = buffer->buffers[cpu];
3912
3913 if (atomic_read(&cpu_buffer->record_disabled))
3914 goto out;
3915
3916 if (length > buffer->max_data_size)
3917 goto out;
3918
3919 if (unlikely(trace_recursive_lock(cpu_buffer)))
3920 goto out;
3921
3922 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3923 if (!event)
3924 goto out_unlock;
3925
3926 body = rb_event_data(event);
3927
3928 memcpy(body, data, length);
3929
3930 rb_commit(cpu_buffer);
3931
3932 rb_wakeups(buffer, cpu_buffer);
3933
3934 ret = 0;
3935
3936 out_unlock:
3937 trace_recursive_unlock(cpu_buffer);
3938
3939 out:
3940 preempt_enable_notrace();
3941
3942 return ret;
3943}
3944EXPORT_SYMBOL_GPL(ring_buffer_write);
3945
3946static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3947{
3948 struct buffer_page *reader = cpu_buffer->reader_page;
3949 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3950 struct buffer_page *commit = cpu_buffer->commit_page;
3951
3952 /* In case of error, head will be NULL */
3953 if (unlikely(!head))
3954 return true;
3955
3956 /* Reader should exhaust content in reader page */
3957 if (reader->read != rb_page_commit(reader))
3958 return false;
3959
3960 /*
3961 * If writers are committing on the reader page, knowing all
3962 * committed content has been read, the ring buffer is empty.
3963 */
3964 if (commit == reader)
3965 return true;
3966
3967 /*
3968 * If writers are committing on a page other than reader page
3969 * and head page, there should always be content to read.
3970 */
3971 if (commit != head)
3972 return false;
3973
3974 /*
3975 * Writers are committing on the head page, we just need
3976 * to care about there're committed data, and the reader will
3977 * swap reader page with head page when it is to read data.
3978 */
3979 return rb_page_commit(commit) == 0;
3980}
3981
3982/**
3983 * ring_buffer_record_disable - stop all writes into the buffer
3984 * @buffer: The ring buffer to stop writes to.
3985 *
3986 * This prevents all writes to the buffer. Any attempt to write
3987 * to the buffer after this will fail and return NULL.
3988 *
3989 * The caller should call synchronize_rcu() after this.
3990 */
3991void ring_buffer_record_disable(struct trace_buffer *buffer)
3992{
3993 atomic_inc(&buffer->record_disabled);
3994}
3995EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3996
3997/**
3998 * ring_buffer_record_enable - enable writes to the buffer
3999 * @buffer: The ring buffer to enable writes
4000 *
4001 * Note, multiple disables will need the same number of enables
4002 * to truly enable the writing (much like preempt_disable).
4003 */
4004void ring_buffer_record_enable(struct trace_buffer *buffer)
4005{
4006 atomic_dec(&buffer->record_disabled);
4007}
4008EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4009
4010/**
4011 * ring_buffer_record_off - stop all writes into the buffer
4012 * @buffer: The ring buffer to stop writes to.
4013 *
4014 * This prevents all writes to the buffer. Any attempt to write
4015 * to the buffer after this will fail and return NULL.
4016 *
4017 * This is different than ring_buffer_record_disable() as
4018 * it works like an on/off switch, where as the disable() version
4019 * must be paired with a enable().
4020 */
4021void ring_buffer_record_off(struct trace_buffer *buffer)
4022{
4023 unsigned int rd;
4024 unsigned int new_rd;
4025
4026 rd = atomic_read(&buffer->record_disabled);
4027 do {
4028 new_rd = rd | RB_BUFFER_OFF;
4029 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4030}
4031EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4032
4033/**
4034 * ring_buffer_record_on - restart writes into the buffer
4035 * @buffer: The ring buffer to start writes to.
4036 *
4037 * This enables all writes to the buffer that was disabled by
4038 * ring_buffer_record_off().
4039 *
4040 * This is different than ring_buffer_record_enable() as
4041 * it works like an on/off switch, where as the enable() version
4042 * must be paired with a disable().
4043 */
4044void ring_buffer_record_on(struct trace_buffer *buffer)
4045{
4046 unsigned int rd;
4047 unsigned int new_rd;
4048
4049 rd = atomic_read(&buffer->record_disabled);
4050 do {
4051 new_rd = rd & ~RB_BUFFER_OFF;
4052 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4053}
4054EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4055
4056/**
4057 * ring_buffer_record_is_on - return true if the ring buffer can write
4058 * @buffer: The ring buffer to see if write is enabled
4059 *
4060 * Returns true if the ring buffer is in a state that it accepts writes.
4061 */
4062bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4063{
4064 return !atomic_read(&buffer->record_disabled);
4065}
4066
4067/**
4068 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4069 * @buffer: The ring buffer to see if write is set enabled
4070 *
4071 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4072 * Note that this does NOT mean it is in a writable state.
4073 *
4074 * It may return true when the ring buffer has been disabled by
4075 * ring_buffer_record_disable(), as that is a temporary disabling of
4076 * the ring buffer.
4077 */
4078bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4079{
4080 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4081}
4082
4083/**
4084 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4085 * @buffer: The ring buffer to stop writes to.
4086 * @cpu: The CPU buffer to stop
4087 *
4088 * This prevents all writes to the buffer. Any attempt to write
4089 * to the buffer after this will fail and return NULL.
4090 *
4091 * The caller should call synchronize_rcu() after this.
4092 */
4093void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4094{
4095 struct ring_buffer_per_cpu *cpu_buffer;
4096
4097 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4098 return;
4099
4100 cpu_buffer = buffer->buffers[cpu];
4101 atomic_inc(&cpu_buffer->record_disabled);
4102}
4103EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4104
4105/**
4106 * ring_buffer_record_enable_cpu - enable writes to the buffer
4107 * @buffer: The ring buffer to enable writes
4108 * @cpu: The CPU to enable.
4109 *
4110 * Note, multiple disables will need the same number of enables
4111 * to truly enable the writing (much like preempt_disable).
4112 */
4113void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4114{
4115 struct ring_buffer_per_cpu *cpu_buffer;
4116
4117 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4118 return;
4119
4120 cpu_buffer = buffer->buffers[cpu];
4121 atomic_dec(&cpu_buffer->record_disabled);
4122}
4123EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4124
4125/*
4126 * The total entries in the ring buffer is the running counter
4127 * of entries entered into the ring buffer, minus the sum of
4128 * the entries read from the ring buffer and the number of
4129 * entries that were overwritten.
4130 */
4131static inline unsigned long
4132rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4133{
4134 return local_read(&cpu_buffer->entries) -
4135 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4136}
4137
4138/**
4139 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4140 * @buffer: The ring buffer
4141 * @cpu: The per CPU buffer to read from.
4142 */
4143u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4144{
4145 unsigned long flags;
4146 struct ring_buffer_per_cpu *cpu_buffer;
4147 struct buffer_page *bpage;
4148 u64 ret = 0;
4149
4150 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4151 return 0;
4152
4153 cpu_buffer = buffer->buffers[cpu];
4154 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4155 /*
4156 * if the tail is on reader_page, oldest time stamp is on the reader
4157 * page
4158 */
4159 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4160 bpage = cpu_buffer->reader_page;
4161 else
4162 bpage = rb_set_head_page(cpu_buffer);
4163 if (bpage)
4164 ret = bpage->page->time_stamp;
4165 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4166
4167 return ret;
4168}
4169EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4170
4171/**
4172 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4173 * @buffer: The ring buffer
4174 * @cpu: The per CPU buffer to read from.
4175 */
4176unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4177{
4178 struct ring_buffer_per_cpu *cpu_buffer;
4179 unsigned long ret;
4180
4181 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4182 return 0;
4183
4184 cpu_buffer = buffer->buffers[cpu];
4185 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4186
4187 return ret;
4188}
4189EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4190
4191/**
4192 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4193 * @buffer: The ring buffer
4194 * @cpu: The per CPU buffer to get the entries from.
4195 */
4196unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4197{
4198 struct ring_buffer_per_cpu *cpu_buffer;
4199
4200 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4201 return 0;
4202
4203 cpu_buffer = buffer->buffers[cpu];
4204
4205 return rb_num_of_entries(cpu_buffer);
4206}
4207EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4208
4209/**
4210 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4211 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4212 * @buffer: The ring buffer
4213 * @cpu: The per CPU buffer to get the number of overruns from
4214 */
4215unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4216{
4217 struct ring_buffer_per_cpu *cpu_buffer;
4218 unsigned long ret;
4219
4220 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4221 return 0;
4222
4223 cpu_buffer = buffer->buffers[cpu];
4224 ret = local_read(&cpu_buffer->overrun);
4225
4226 return ret;
4227}
4228EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4229
4230/**
4231 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4232 * commits failing due to the buffer wrapping around while there are uncommitted
4233 * events, such as during an interrupt storm.
4234 * @buffer: The ring buffer
4235 * @cpu: The per CPU buffer to get the number of overruns from
4236 */
4237unsigned long
4238ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4239{
4240 struct ring_buffer_per_cpu *cpu_buffer;
4241 unsigned long ret;
4242
4243 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4244 return 0;
4245
4246 cpu_buffer = buffer->buffers[cpu];
4247 ret = local_read(&cpu_buffer->commit_overrun);
4248
4249 return ret;
4250}
4251EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4252
4253/**
4254 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4255 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4256 * @buffer: The ring buffer
4257 * @cpu: The per CPU buffer to get the number of overruns from
4258 */
4259unsigned long
4260ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4261{
4262 struct ring_buffer_per_cpu *cpu_buffer;
4263 unsigned long ret;
4264
4265 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4266 return 0;
4267
4268 cpu_buffer = buffer->buffers[cpu];
4269 ret = local_read(&cpu_buffer->dropped_events);
4270
4271 return ret;
4272}
4273EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4274
4275/**
4276 * ring_buffer_read_events_cpu - get the number of events successfully read
4277 * @buffer: The ring buffer
4278 * @cpu: The per CPU buffer to get the number of events read
4279 */
4280unsigned long
4281ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4282{
4283 struct ring_buffer_per_cpu *cpu_buffer;
4284
4285 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4286 return 0;
4287
4288 cpu_buffer = buffer->buffers[cpu];
4289 return cpu_buffer->read;
4290}
4291EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4292
4293/**
4294 * ring_buffer_entries - get the number of entries in a buffer
4295 * @buffer: The ring buffer
4296 *
4297 * Returns the total number of entries in the ring buffer
4298 * (all CPU entries)
4299 */
4300unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4301{
4302 struct ring_buffer_per_cpu *cpu_buffer;
4303 unsigned long entries = 0;
4304 int cpu;
4305
4306 /* if you care about this being correct, lock the buffer */
4307 for_each_buffer_cpu(buffer, cpu) {
4308 cpu_buffer = buffer->buffers[cpu];
4309 entries += rb_num_of_entries(cpu_buffer);
4310 }
4311
4312 return entries;
4313}
4314EXPORT_SYMBOL_GPL(ring_buffer_entries);
4315
4316/**
4317 * ring_buffer_overruns - get the number of overruns in buffer
4318 * @buffer: The ring buffer
4319 *
4320 * Returns the total number of overruns in the ring buffer
4321 * (all CPU entries)
4322 */
4323unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4324{
4325 struct ring_buffer_per_cpu *cpu_buffer;
4326 unsigned long overruns = 0;
4327 int cpu;
4328
4329 /* if you care about this being correct, lock the buffer */
4330 for_each_buffer_cpu(buffer, cpu) {
4331 cpu_buffer = buffer->buffers[cpu];
4332 overruns += local_read(&cpu_buffer->overrun);
4333 }
4334
4335 return overruns;
4336}
4337EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4338
4339static void rb_iter_reset(struct ring_buffer_iter *iter)
4340{
4341 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4342
4343 /* Iterator usage is expected to have record disabled */
4344 iter->head_page = cpu_buffer->reader_page;
4345 iter->head = cpu_buffer->reader_page->read;
4346 iter->next_event = iter->head;
4347
4348 iter->cache_reader_page = iter->head_page;
4349 iter->cache_read = cpu_buffer->read;
4350 iter->cache_pages_removed = cpu_buffer->pages_removed;
4351
4352 if (iter->head) {
4353 iter->read_stamp = cpu_buffer->read_stamp;
4354 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4355 } else {
4356 iter->read_stamp = iter->head_page->page->time_stamp;
4357 iter->page_stamp = iter->read_stamp;
4358 }
4359}
4360
4361/**
4362 * ring_buffer_iter_reset - reset an iterator
4363 * @iter: The iterator to reset
4364 *
4365 * Resets the iterator, so that it will start from the beginning
4366 * again.
4367 */
4368void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4369{
4370 struct ring_buffer_per_cpu *cpu_buffer;
4371 unsigned long flags;
4372
4373 if (!iter)
4374 return;
4375
4376 cpu_buffer = iter->cpu_buffer;
4377
4378 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4379 rb_iter_reset(iter);
4380 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4381}
4382EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4383
4384/**
4385 * ring_buffer_iter_empty - check if an iterator has no more to read
4386 * @iter: The iterator to check
4387 */
4388int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4389{
4390 struct ring_buffer_per_cpu *cpu_buffer;
4391 struct buffer_page *reader;
4392 struct buffer_page *head_page;
4393 struct buffer_page *commit_page;
4394 struct buffer_page *curr_commit_page;
4395 unsigned commit;
4396 u64 curr_commit_ts;
4397 u64 commit_ts;
4398
4399 cpu_buffer = iter->cpu_buffer;
4400 reader = cpu_buffer->reader_page;
4401 head_page = cpu_buffer->head_page;
4402 commit_page = READ_ONCE(cpu_buffer->commit_page);
4403 commit_ts = commit_page->page->time_stamp;
4404
4405 /*
4406 * When the writer goes across pages, it issues a cmpxchg which
4407 * is a mb(), which will synchronize with the rmb here.
4408 * (see rb_tail_page_update())
4409 */
4410 smp_rmb();
4411 commit = rb_page_commit(commit_page);
4412 /* We want to make sure that the commit page doesn't change */
4413 smp_rmb();
4414
4415 /* Make sure commit page didn't change */
4416 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4417 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4418
4419 /* If the commit page changed, then there's more data */
4420 if (curr_commit_page != commit_page ||
4421 curr_commit_ts != commit_ts)
4422 return 0;
4423
4424 /* Still racy, as it may return a false positive, but that's OK */
4425 return ((iter->head_page == commit_page && iter->head >= commit) ||
4426 (iter->head_page == reader && commit_page == head_page &&
4427 head_page->read == commit &&
4428 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4429}
4430EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4431
4432static void
4433rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4434 struct ring_buffer_event *event)
4435{
4436 u64 delta;
4437
4438 switch (event->type_len) {
4439 case RINGBUF_TYPE_PADDING:
4440 return;
4441
4442 case RINGBUF_TYPE_TIME_EXTEND:
4443 delta = rb_event_time_stamp(event);
4444 cpu_buffer->read_stamp += delta;
4445 return;
4446
4447 case RINGBUF_TYPE_TIME_STAMP:
4448 delta = rb_event_time_stamp(event);
4449 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
4450 cpu_buffer->read_stamp = delta;
4451 return;
4452
4453 case RINGBUF_TYPE_DATA:
4454 cpu_buffer->read_stamp += event->time_delta;
4455 return;
4456
4457 default:
4458 RB_WARN_ON(cpu_buffer, 1);
4459 }
4460}
4461
4462static void
4463rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4464 struct ring_buffer_event *event)
4465{
4466 u64 delta;
4467
4468 switch (event->type_len) {
4469 case RINGBUF_TYPE_PADDING:
4470 return;
4471
4472 case RINGBUF_TYPE_TIME_EXTEND:
4473 delta = rb_event_time_stamp(event);
4474 iter->read_stamp += delta;
4475 return;
4476
4477 case RINGBUF_TYPE_TIME_STAMP:
4478 delta = rb_event_time_stamp(event);
4479 delta = rb_fix_abs_ts(delta, iter->read_stamp);
4480 iter->read_stamp = delta;
4481 return;
4482
4483 case RINGBUF_TYPE_DATA:
4484 iter->read_stamp += event->time_delta;
4485 return;
4486
4487 default:
4488 RB_WARN_ON(iter->cpu_buffer, 1);
4489 }
4490}
4491
4492static struct buffer_page *
4493rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4494{
4495 struct buffer_page *reader = NULL;
4496 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
4497 unsigned long overwrite;
4498 unsigned long flags;
4499 int nr_loops = 0;
4500 bool ret;
4501
4502 local_irq_save(flags);
4503 arch_spin_lock(&cpu_buffer->lock);
4504
4505 again:
4506 /*
4507 * This should normally only loop twice. But because the
4508 * start of the reader inserts an empty page, it causes
4509 * a case where we will loop three times. There should be no
4510 * reason to loop four times (that I know of).
4511 */
4512 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4513 reader = NULL;
4514 goto out;
4515 }
4516
4517 reader = cpu_buffer->reader_page;
4518
4519 /* If there's more to read, return this page */
4520 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4521 goto out;
4522
4523 /* Never should we have an index greater than the size */
4524 if (RB_WARN_ON(cpu_buffer,
4525 cpu_buffer->reader_page->read > rb_page_size(reader)))
4526 goto out;
4527
4528 /* check if we caught up to the tail */
4529 reader = NULL;
4530 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4531 goto out;
4532
4533 /* Don't bother swapping if the ring buffer is empty */
4534 if (rb_num_of_entries(cpu_buffer) == 0)
4535 goto out;
4536
4537 /*
4538 * Reset the reader page to size zero.
4539 */
4540 local_set(&cpu_buffer->reader_page->write, 0);
4541 local_set(&cpu_buffer->reader_page->entries, 0);
4542 local_set(&cpu_buffer->reader_page->page->commit, 0);
4543 cpu_buffer->reader_page->real_end = 0;
4544
4545 spin:
4546 /*
4547 * Splice the empty reader page into the list around the head.
4548 */
4549 reader = rb_set_head_page(cpu_buffer);
4550 if (!reader)
4551 goto out;
4552 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4553 cpu_buffer->reader_page->list.prev = reader->list.prev;
4554
4555 /*
4556 * cpu_buffer->pages just needs to point to the buffer, it
4557 * has no specific buffer page to point to. Lets move it out
4558 * of our way so we don't accidentally swap it.
4559 */
4560 cpu_buffer->pages = reader->list.prev;
4561
4562 /* The reader page will be pointing to the new head */
4563 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4564
4565 /*
4566 * We want to make sure we read the overruns after we set up our
4567 * pointers to the next object. The writer side does a
4568 * cmpxchg to cross pages which acts as the mb on the writer
4569 * side. Note, the reader will constantly fail the swap
4570 * while the writer is updating the pointers, so this
4571 * guarantees that the overwrite recorded here is the one we
4572 * want to compare with the last_overrun.
4573 */
4574 smp_mb();
4575 overwrite = local_read(&(cpu_buffer->overrun));
4576
4577 /*
4578 * Here's the tricky part.
4579 *
4580 * We need to move the pointer past the header page.
4581 * But we can only do that if a writer is not currently
4582 * moving it. The page before the header page has the
4583 * flag bit '1' set if it is pointing to the page we want.
4584 * but if the writer is in the process of moving it
4585 * than it will be '2' or already moved '0'.
4586 */
4587
4588 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4589
4590 /*
4591 * If we did not convert it, then we must try again.
4592 */
4593 if (!ret)
4594 goto spin;
4595
4596 /*
4597 * Yay! We succeeded in replacing the page.
4598 *
4599 * Now make the new head point back to the reader page.
4600 */
4601 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4602 rb_inc_page(&cpu_buffer->head_page);
4603
4604 local_inc(&cpu_buffer->pages_read);
4605
4606 /* Finally update the reader page to the new head */
4607 cpu_buffer->reader_page = reader;
4608 cpu_buffer->reader_page->read = 0;
4609
4610 if (overwrite != cpu_buffer->last_overrun) {
4611 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4612 cpu_buffer->last_overrun = overwrite;
4613 }
4614
4615 goto again;
4616
4617 out:
4618 /* Update the read_stamp on the first event */
4619 if (reader && reader->read == 0)
4620 cpu_buffer->read_stamp = reader->page->time_stamp;
4621
4622 arch_spin_unlock(&cpu_buffer->lock);
4623 local_irq_restore(flags);
4624
4625 /*
4626 * The writer has preempt disable, wait for it. But not forever
4627 * Although, 1 second is pretty much "forever"
4628 */
4629#define USECS_WAIT 1000000
4630 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4631 /* If the write is past the end of page, a writer is still updating it */
4632 if (likely(!reader || rb_page_write(reader) <= bsize))
4633 break;
4634
4635 udelay(1);
4636
4637 /* Get the latest version of the reader write value */
4638 smp_rmb();
4639 }
4640
4641 /* The writer is not moving forward? Something is wrong */
4642 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4643 reader = NULL;
4644
4645 /*
4646 * Make sure we see any padding after the write update
4647 * (see rb_reset_tail()).
4648 *
4649 * In addition, a writer may be writing on the reader page
4650 * if the page has not been fully filled, so the read barrier
4651 * is also needed to make sure we see the content of what is
4652 * committed by the writer (see rb_set_commit_to_write()).
4653 */
4654 smp_rmb();
4655
4656
4657 return reader;
4658}
4659
4660static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4661{
4662 struct ring_buffer_event *event;
4663 struct buffer_page *reader;
4664 unsigned length;
4665
4666 reader = rb_get_reader_page(cpu_buffer);
4667
4668 /* This function should not be called when buffer is empty */
4669 if (RB_WARN_ON(cpu_buffer, !reader))
4670 return;
4671
4672 event = rb_reader_event(cpu_buffer);
4673
4674 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4675 cpu_buffer->read++;
4676
4677 rb_update_read_stamp(cpu_buffer, event);
4678
4679 length = rb_event_length(event);
4680 cpu_buffer->reader_page->read += length;
4681 cpu_buffer->read_bytes += length;
4682}
4683
4684static void rb_advance_iter(struct ring_buffer_iter *iter)
4685{
4686 struct ring_buffer_per_cpu *cpu_buffer;
4687
4688 cpu_buffer = iter->cpu_buffer;
4689
4690 /* If head == next_event then we need to jump to the next event */
4691 if (iter->head == iter->next_event) {
4692 /* If the event gets overwritten again, there's nothing to do */
4693 if (rb_iter_head_event(iter) == NULL)
4694 return;
4695 }
4696
4697 iter->head = iter->next_event;
4698
4699 /*
4700 * Check if we are at the end of the buffer.
4701 */
4702 if (iter->next_event >= rb_page_size(iter->head_page)) {
4703 /* discarded commits can make the page empty */
4704 if (iter->head_page == cpu_buffer->commit_page)
4705 return;
4706 rb_inc_iter(iter);
4707 return;
4708 }
4709
4710 rb_update_iter_read_stamp(iter, iter->event);
4711}
4712
4713static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4714{
4715 return cpu_buffer->lost_events;
4716}
4717
4718static struct ring_buffer_event *
4719rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4720 unsigned long *lost_events)
4721{
4722 struct ring_buffer_event *event;
4723 struct buffer_page *reader;
4724 int nr_loops = 0;
4725
4726 if (ts)
4727 *ts = 0;
4728 again:
4729 /*
4730 * We repeat when a time extend is encountered.
4731 * Since the time extend is always attached to a data event,
4732 * we should never loop more than once.
4733 * (We never hit the following condition more than twice).
4734 */
4735 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4736 return NULL;
4737
4738 reader = rb_get_reader_page(cpu_buffer);
4739 if (!reader)
4740 return NULL;
4741
4742 event = rb_reader_event(cpu_buffer);
4743
4744 switch (event->type_len) {
4745 case RINGBUF_TYPE_PADDING:
4746 if (rb_null_event(event))
4747 RB_WARN_ON(cpu_buffer, 1);
4748 /*
4749 * Because the writer could be discarding every
4750 * event it creates (which would probably be bad)
4751 * if we were to go back to "again" then we may never
4752 * catch up, and will trigger the warn on, or lock
4753 * the box. Return the padding, and we will release
4754 * the current locks, and try again.
4755 */
4756 return event;
4757
4758 case RINGBUF_TYPE_TIME_EXTEND:
4759 /* Internal data, OK to advance */
4760 rb_advance_reader(cpu_buffer);
4761 goto again;
4762
4763 case RINGBUF_TYPE_TIME_STAMP:
4764 if (ts) {
4765 *ts = rb_event_time_stamp(event);
4766 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
4767 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4768 cpu_buffer->cpu, ts);
4769 }
4770 /* Internal data, OK to advance */
4771 rb_advance_reader(cpu_buffer);
4772 goto again;
4773
4774 case RINGBUF_TYPE_DATA:
4775 if (ts && !(*ts)) {
4776 *ts = cpu_buffer->read_stamp + event->time_delta;
4777 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4778 cpu_buffer->cpu, ts);
4779 }
4780 if (lost_events)
4781 *lost_events = rb_lost_events(cpu_buffer);
4782 return event;
4783
4784 default:
4785 RB_WARN_ON(cpu_buffer, 1);
4786 }
4787
4788 return NULL;
4789}
4790EXPORT_SYMBOL_GPL(ring_buffer_peek);
4791
4792static struct ring_buffer_event *
4793rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4794{
4795 struct trace_buffer *buffer;
4796 struct ring_buffer_per_cpu *cpu_buffer;
4797 struct ring_buffer_event *event;
4798 int nr_loops = 0;
4799
4800 if (ts)
4801 *ts = 0;
4802
4803 cpu_buffer = iter->cpu_buffer;
4804 buffer = cpu_buffer->buffer;
4805
4806 /*
4807 * Check if someone performed a consuming read to the buffer
4808 * or removed some pages from the buffer. In these cases,
4809 * iterator was invalidated and we need to reset it.
4810 */
4811 if (unlikely(iter->cache_read != cpu_buffer->read ||
4812 iter->cache_reader_page != cpu_buffer->reader_page ||
4813 iter->cache_pages_removed != cpu_buffer->pages_removed))
4814 rb_iter_reset(iter);
4815
4816 again:
4817 if (ring_buffer_iter_empty(iter))
4818 return NULL;
4819
4820 /*
4821 * As the writer can mess with what the iterator is trying
4822 * to read, just give up if we fail to get an event after
4823 * three tries. The iterator is not as reliable when reading
4824 * the ring buffer with an active write as the consumer is.
4825 * Do not warn if the three failures is reached.
4826 */
4827 if (++nr_loops > 3)
4828 return NULL;
4829
4830 if (rb_per_cpu_empty(cpu_buffer))
4831 return NULL;
4832
4833 if (iter->head >= rb_page_size(iter->head_page)) {
4834 rb_inc_iter(iter);
4835 goto again;
4836 }
4837
4838 event = rb_iter_head_event(iter);
4839 if (!event)
4840 goto again;
4841
4842 switch (event->type_len) {
4843 case RINGBUF_TYPE_PADDING:
4844 if (rb_null_event(event)) {
4845 rb_inc_iter(iter);
4846 goto again;
4847 }
4848 rb_advance_iter(iter);
4849 return event;
4850
4851 case RINGBUF_TYPE_TIME_EXTEND:
4852 /* Internal data, OK to advance */
4853 rb_advance_iter(iter);
4854 goto again;
4855
4856 case RINGBUF_TYPE_TIME_STAMP:
4857 if (ts) {
4858 *ts = rb_event_time_stamp(event);
4859 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
4860 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4861 cpu_buffer->cpu, ts);
4862 }
4863 /* Internal data, OK to advance */
4864 rb_advance_iter(iter);
4865 goto again;
4866
4867 case RINGBUF_TYPE_DATA:
4868 if (ts && !(*ts)) {
4869 *ts = iter->read_stamp + event->time_delta;
4870 ring_buffer_normalize_time_stamp(buffer,
4871 cpu_buffer->cpu, ts);
4872 }
4873 return event;
4874
4875 default:
4876 RB_WARN_ON(cpu_buffer, 1);
4877 }
4878
4879 return NULL;
4880}
4881EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4882
4883static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4884{
4885 if (likely(!in_nmi())) {
4886 raw_spin_lock(&cpu_buffer->reader_lock);
4887 return true;
4888 }
4889
4890 /*
4891 * If an NMI die dumps out the content of the ring buffer
4892 * trylock must be used to prevent a deadlock if the NMI
4893 * preempted a task that holds the ring buffer locks. If
4894 * we get the lock then all is fine, if not, then continue
4895 * to do the read, but this can corrupt the ring buffer,
4896 * so it must be permanently disabled from future writes.
4897 * Reading from NMI is a oneshot deal.
4898 */
4899 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4900 return true;
4901
4902 /* Continue without locking, but disable the ring buffer */
4903 atomic_inc(&cpu_buffer->record_disabled);
4904 return false;
4905}
4906
4907static inline void
4908rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4909{
4910 if (likely(locked))
4911 raw_spin_unlock(&cpu_buffer->reader_lock);
4912}
4913
4914/**
4915 * ring_buffer_peek - peek at the next event to be read
4916 * @buffer: The ring buffer to read
4917 * @cpu: The cpu to peak at
4918 * @ts: The timestamp counter of this event.
4919 * @lost_events: a variable to store if events were lost (may be NULL)
4920 *
4921 * This will return the event that will be read next, but does
4922 * not consume the data.
4923 */
4924struct ring_buffer_event *
4925ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4926 unsigned long *lost_events)
4927{
4928 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4929 struct ring_buffer_event *event;
4930 unsigned long flags;
4931 bool dolock;
4932
4933 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4934 return NULL;
4935
4936 again:
4937 local_irq_save(flags);
4938 dolock = rb_reader_lock(cpu_buffer);
4939 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4940 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4941 rb_advance_reader(cpu_buffer);
4942 rb_reader_unlock(cpu_buffer, dolock);
4943 local_irq_restore(flags);
4944
4945 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4946 goto again;
4947
4948 return event;
4949}
4950
4951/** ring_buffer_iter_dropped - report if there are dropped events
4952 * @iter: The ring buffer iterator
4953 *
4954 * Returns true if there was dropped events since the last peek.
4955 */
4956bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4957{
4958 bool ret = iter->missed_events != 0;
4959
4960 iter->missed_events = 0;
4961 return ret;
4962}
4963EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4964
4965/**
4966 * ring_buffer_iter_peek - peek at the next event to be read
4967 * @iter: The ring buffer iterator
4968 * @ts: The timestamp counter of this event.
4969 *
4970 * This will return the event that will be read next, but does
4971 * not increment the iterator.
4972 */
4973struct ring_buffer_event *
4974ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4975{
4976 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4977 struct ring_buffer_event *event;
4978 unsigned long flags;
4979
4980 again:
4981 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4982 event = rb_iter_peek(iter, ts);
4983 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4984
4985 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4986 goto again;
4987
4988 return event;
4989}
4990
4991/**
4992 * ring_buffer_consume - return an event and consume it
4993 * @buffer: The ring buffer to get the next event from
4994 * @cpu: the cpu to read the buffer from
4995 * @ts: a variable to store the timestamp (may be NULL)
4996 * @lost_events: a variable to store if events were lost (may be NULL)
4997 *
4998 * Returns the next event in the ring buffer, and that event is consumed.
4999 * Meaning, that sequential reads will keep returning a different event,
5000 * and eventually empty the ring buffer if the producer is slower.
5001 */
5002struct ring_buffer_event *
5003ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5004 unsigned long *lost_events)
5005{
5006 struct ring_buffer_per_cpu *cpu_buffer;
5007 struct ring_buffer_event *event = NULL;
5008 unsigned long flags;
5009 bool dolock;
5010
5011 again:
5012 /* might be called in atomic */
5013 preempt_disable();
5014
5015 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5016 goto out;
5017
5018 cpu_buffer = buffer->buffers[cpu];
5019 local_irq_save(flags);
5020 dolock = rb_reader_lock(cpu_buffer);
5021
5022 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5023 if (event) {
5024 cpu_buffer->lost_events = 0;
5025 rb_advance_reader(cpu_buffer);
5026 }
5027
5028 rb_reader_unlock(cpu_buffer, dolock);
5029 local_irq_restore(flags);
5030
5031 out:
5032 preempt_enable();
5033
5034 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5035 goto again;
5036
5037 return event;
5038}
5039EXPORT_SYMBOL_GPL(ring_buffer_consume);
5040
5041/**
5042 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5043 * @buffer: The ring buffer to read from
5044 * @cpu: The cpu buffer to iterate over
5045 * @flags: gfp flags to use for memory allocation
5046 *
5047 * This performs the initial preparations necessary to iterate
5048 * through the buffer. Memory is allocated, buffer recording
5049 * is disabled, and the iterator pointer is returned to the caller.
5050 *
5051 * Disabling buffer recording prevents the reading from being
5052 * corrupted. This is not a consuming read, so a producer is not
5053 * expected.
5054 *
5055 * After a sequence of ring_buffer_read_prepare calls, the user is
5056 * expected to make at least one call to ring_buffer_read_prepare_sync.
5057 * Afterwards, ring_buffer_read_start is invoked to get things going
5058 * for real.
5059 *
5060 * This overall must be paired with ring_buffer_read_finish.
5061 */
5062struct ring_buffer_iter *
5063ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5064{
5065 struct ring_buffer_per_cpu *cpu_buffer;
5066 struct ring_buffer_iter *iter;
5067
5068 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5069 return NULL;
5070
5071 iter = kzalloc(sizeof(*iter), flags);
5072 if (!iter)
5073 return NULL;
5074
5075 /* Holds the entire event: data and meta data */
5076 iter->event_size = buffer->subbuf_size;
5077 iter->event = kmalloc(iter->event_size, flags);
5078 if (!iter->event) {
5079 kfree(iter);
5080 return NULL;
5081 }
5082
5083 cpu_buffer = buffer->buffers[cpu];
5084
5085 iter->cpu_buffer = cpu_buffer;
5086
5087 atomic_inc(&cpu_buffer->resize_disabled);
5088
5089 return iter;
5090}
5091EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5092
5093/**
5094 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5095 *
5096 * All previously invoked ring_buffer_read_prepare calls to prepare
5097 * iterators will be synchronized. Afterwards, read_buffer_read_start
5098 * calls on those iterators are allowed.
5099 */
5100void
5101ring_buffer_read_prepare_sync(void)
5102{
5103 synchronize_rcu();
5104}
5105EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5106
5107/**
5108 * ring_buffer_read_start - start a non consuming read of the buffer
5109 * @iter: The iterator returned by ring_buffer_read_prepare
5110 *
5111 * This finalizes the startup of an iteration through the buffer.
5112 * The iterator comes from a call to ring_buffer_read_prepare and
5113 * an intervening ring_buffer_read_prepare_sync must have been
5114 * performed.
5115 *
5116 * Must be paired with ring_buffer_read_finish.
5117 */
5118void
5119ring_buffer_read_start(struct ring_buffer_iter *iter)
5120{
5121 struct ring_buffer_per_cpu *cpu_buffer;
5122 unsigned long flags;
5123
5124 if (!iter)
5125 return;
5126
5127 cpu_buffer = iter->cpu_buffer;
5128
5129 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5130 arch_spin_lock(&cpu_buffer->lock);
5131 rb_iter_reset(iter);
5132 arch_spin_unlock(&cpu_buffer->lock);
5133 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5134}
5135EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5136
5137/**
5138 * ring_buffer_read_finish - finish reading the iterator of the buffer
5139 * @iter: The iterator retrieved by ring_buffer_start
5140 *
5141 * This re-enables the recording to the buffer, and frees the
5142 * iterator.
5143 */
5144void
5145ring_buffer_read_finish(struct ring_buffer_iter *iter)
5146{
5147 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5148 unsigned long flags;
5149
5150 /*
5151 * Ring buffer is disabled from recording, here's a good place
5152 * to check the integrity of the ring buffer.
5153 * Must prevent readers from trying to read, as the check
5154 * clears the HEAD page and readers require it.
5155 */
5156 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5157 rb_check_pages(cpu_buffer);
5158 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5159
5160 atomic_dec(&cpu_buffer->resize_disabled);
5161 kfree(iter->event);
5162 kfree(iter);
5163}
5164EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5165
5166/**
5167 * ring_buffer_iter_advance - advance the iterator to the next location
5168 * @iter: The ring buffer iterator
5169 *
5170 * Move the location of the iterator such that the next read will
5171 * be the next location of the iterator.
5172 */
5173void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5174{
5175 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5176 unsigned long flags;
5177
5178 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5179
5180 rb_advance_iter(iter);
5181
5182 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5183}
5184EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5185
5186/**
5187 * ring_buffer_size - return the size of the ring buffer (in bytes)
5188 * @buffer: The ring buffer.
5189 * @cpu: The CPU to get ring buffer size from.
5190 */
5191unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5192{
5193 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5194 return 0;
5195
5196 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5197}
5198EXPORT_SYMBOL_GPL(ring_buffer_size);
5199
5200/**
5201 * ring_buffer_max_event_size - return the max data size of an event
5202 * @buffer: The ring buffer.
5203 *
5204 * Returns the maximum size an event can be.
5205 */
5206unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5207{
5208 /* If abs timestamp is requested, events have a timestamp too */
5209 if (ring_buffer_time_stamp_abs(buffer))
5210 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5211 return buffer->max_data_size;
5212}
5213EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5214
5215static void rb_clear_buffer_page(struct buffer_page *page)
5216{
5217 local_set(&page->write, 0);
5218 local_set(&page->entries, 0);
5219 rb_init_page(page->page);
5220 page->read = 0;
5221}
5222
5223static void
5224rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5225{
5226 struct buffer_page *page;
5227
5228 rb_head_page_deactivate(cpu_buffer);
5229
5230 cpu_buffer->head_page
5231 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5232 rb_clear_buffer_page(cpu_buffer->head_page);
5233 list_for_each_entry(page, cpu_buffer->pages, list) {
5234 rb_clear_buffer_page(page);
5235 }
5236
5237 cpu_buffer->tail_page = cpu_buffer->head_page;
5238 cpu_buffer->commit_page = cpu_buffer->head_page;
5239
5240 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5241 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5242 rb_clear_buffer_page(cpu_buffer->reader_page);
5243
5244 local_set(&cpu_buffer->entries_bytes, 0);
5245 local_set(&cpu_buffer->overrun, 0);
5246 local_set(&cpu_buffer->commit_overrun, 0);
5247 local_set(&cpu_buffer->dropped_events, 0);
5248 local_set(&cpu_buffer->entries, 0);
5249 local_set(&cpu_buffer->committing, 0);
5250 local_set(&cpu_buffer->commits, 0);
5251 local_set(&cpu_buffer->pages_touched, 0);
5252 local_set(&cpu_buffer->pages_lost, 0);
5253 local_set(&cpu_buffer->pages_read, 0);
5254 cpu_buffer->last_pages_touch = 0;
5255 cpu_buffer->shortest_full = 0;
5256 cpu_buffer->read = 0;
5257 cpu_buffer->read_bytes = 0;
5258
5259 rb_time_set(&cpu_buffer->write_stamp, 0);
5260 rb_time_set(&cpu_buffer->before_stamp, 0);
5261
5262 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5263
5264 cpu_buffer->lost_events = 0;
5265 cpu_buffer->last_overrun = 0;
5266
5267 rb_head_page_activate(cpu_buffer);
5268 cpu_buffer->pages_removed = 0;
5269}
5270
5271/* Must have disabled the cpu buffer then done a synchronize_rcu */
5272static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5273{
5274 unsigned long flags;
5275
5276 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5277
5278 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5279 goto out;
5280
5281 arch_spin_lock(&cpu_buffer->lock);
5282
5283 rb_reset_cpu(cpu_buffer);
5284
5285 arch_spin_unlock(&cpu_buffer->lock);
5286
5287 out:
5288 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5289}
5290
5291/**
5292 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5293 * @buffer: The ring buffer to reset a per cpu buffer of
5294 * @cpu: The CPU buffer to be reset
5295 */
5296void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5297{
5298 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5299
5300 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5301 return;
5302
5303 /* prevent another thread from changing buffer sizes */
5304 mutex_lock(&buffer->mutex);
5305
5306 atomic_inc(&cpu_buffer->resize_disabled);
5307 atomic_inc(&cpu_buffer->record_disabled);
5308
5309 /* Make sure all commits have finished */
5310 synchronize_rcu();
5311
5312 reset_disabled_cpu_buffer(cpu_buffer);
5313
5314 atomic_dec(&cpu_buffer->record_disabled);
5315 atomic_dec(&cpu_buffer->resize_disabled);
5316
5317 mutex_unlock(&buffer->mutex);
5318}
5319EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5320
5321/* Flag to ensure proper resetting of atomic variables */
5322#define RESET_BIT (1 << 30)
5323
5324/**
5325 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5326 * @buffer: The ring buffer to reset a per cpu buffer of
5327 */
5328void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5329{
5330 struct ring_buffer_per_cpu *cpu_buffer;
5331 int cpu;
5332
5333 /* prevent another thread from changing buffer sizes */
5334 mutex_lock(&buffer->mutex);
5335
5336 for_each_online_buffer_cpu(buffer, cpu) {
5337 cpu_buffer = buffer->buffers[cpu];
5338
5339 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
5340 atomic_inc(&cpu_buffer->record_disabled);
5341 }
5342
5343 /* Make sure all commits have finished */
5344 synchronize_rcu();
5345
5346 for_each_buffer_cpu(buffer, cpu) {
5347 cpu_buffer = buffer->buffers[cpu];
5348
5349 /*
5350 * If a CPU came online during the synchronize_rcu(), then
5351 * ignore it.
5352 */
5353 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
5354 continue;
5355
5356 reset_disabled_cpu_buffer(cpu_buffer);
5357
5358 atomic_dec(&cpu_buffer->record_disabled);
5359 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
5360 }
5361
5362 mutex_unlock(&buffer->mutex);
5363}
5364
5365/**
5366 * ring_buffer_reset - reset a ring buffer
5367 * @buffer: The ring buffer to reset all cpu buffers
5368 */
5369void ring_buffer_reset(struct trace_buffer *buffer)
5370{
5371 struct ring_buffer_per_cpu *cpu_buffer;
5372 int cpu;
5373
5374 /* prevent another thread from changing buffer sizes */
5375 mutex_lock(&buffer->mutex);
5376
5377 for_each_buffer_cpu(buffer, cpu) {
5378 cpu_buffer = buffer->buffers[cpu];
5379
5380 atomic_inc(&cpu_buffer->resize_disabled);
5381 atomic_inc(&cpu_buffer->record_disabled);
5382 }
5383
5384 /* Make sure all commits have finished */
5385 synchronize_rcu();
5386
5387 for_each_buffer_cpu(buffer, cpu) {
5388 cpu_buffer = buffer->buffers[cpu];
5389
5390 reset_disabled_cpu_buffer(cpu_buffer);
5391
5392 atomic_dec(&cpu_buffer->record_disabled);
5393 atomic_dec(&cpu_buffer->resize_disabled);
5394 }
5395
5396 mutex_unlock(&buffer->mutex);
5397}
5398EXPORT_SYMBOL_GPL(ring_buffer_reset);
5399
5400/**
5401 * ring_buffer_empty - is the ring buffer empty?
5402 * @buffer: The ring buffer to test
5403 */
5404bool ring_buffer_empty(struct trace_buffer *buffer)
5405{
5406 struct ring_buffer_per_cpu *cpu_buffer;
5407 unsigned long flags;
5408 bool dolock;
5409 bool ret;
5410 int cpu;
5411
5412 /* yes this is racy, but if you don't like the race, lock the buffer */
5413 for_each_buffer_cpu(buffer, cpu) {
5414 cpu_buffer = buffer->buffers[cpu];
5415 local_irq_save(flags);
5416 dolock = rb_reader_lock(cpu_buffer);
5417 ret = rb_per_cpu_empty(cpu_buffer);
5418 rb_reader_unlock(cpu_buffer, dolock);
5419 local_irq_restore(flags);
5420
5421 if (!ret)
5422 return false;
5423 }
5424
5425 return true;
5426}
5427EXPORT_SYMBOL_GPL(ring_buffer_empty);
5428
5429/**
5430 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5431 * @buffer: The ring buffer
5432 * @cpu: The CPU buffer to test
5433 */
5434bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5435{
5436 struct ring_buffer_per_cpu *cpu_buffer;
5437 unsigned long flags;
5438 bool dolock;
5439 bool ret;
5440
5441 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5442 return true;
5443
5444 cpu_buffer = buffer->buffers[cpu];
5445 local_irq_save(flags);
5446 dolock = rb_reader_lock(cpu_buffer);
5447 ret = rb_per_cpu_empty(cpu_buffer);
5448 rb_reader_unlock(cpu_buffer, dolock);
5449 local_irq_restore(flags);
5450
5451 return ret;
5452}
5453EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5454
5455#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5456/**
5457 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5458 * @buffer_a: One buffer to swap with
5459 * @buffer_b: The other buffer to swap with
5460 * @cpu: the CPU of the buffers to swap
5461 *
5462 * This function is useful for tracers that want to take a "snapshot"
5463 * of a CPU buffer and has another back up buffer lying around.
5464 * it is expected that the tracer handles the cpu buffer not being
5465 * used at the moment.
5466 */
5467int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5468 struct trace_buffer *buffer_b, int cpu)
5469{
5470 struct ring_buffer_per_cpu *cpu_buffer_a;
5471 struct ring_buffer_per_cpu *cpu_buffer_b;
5472 int ret = -EINVAL;
5473
5474 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5475 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5476 goto out;
5477
5478 cpu_buffer_a = buffer_a->buffers[cpu];
5479 cpu_buffer_b = buffer_b->buffers[cpu];
5480
5481 /* At least make sure the two buffers are somewhat the same */
5482 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5483 goto out;
5484
5485 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
5486 goto out;
5487
5488 ret = -EAGAIN;
5489
5490 if (atomic_read(&buffer_a->record_disabled))
5491 goto out;
5492
5493 if (atomic_read(&buffer_b->record_disabled))
5494 goto out;
5495
5496 if (atomic_read(&cpu_buffer_a->record_disabled))
5497 goto out;
5498
5499 if (atomic_read(&cpu_buffer_b->record_disabled))
5500 goto out;
5501
5502 /*
5503 * We can't do a synchronize_rcu here because this
5504 * function can be called in atomic context.
5505 * Normally this will be called from the same CPU as cpu.
5506 * If not it's up to the caller to protect this.
5507 */
5508 atomic_inc(&cpu_buffer_a->record_disabled);
5509 atomic_inc(&cpu_buffer_b->record_disabled);
5510
5511 ret = -EBUSY;
5512 if (local_read(&cpu_buffer_a->committing))
5513 goto out_dec;
5514 if (local_read(&cpu_buffer_b->committing))
5515 goto out_dec;
5516
5517 /*
5518 * When resize is in progress, we cannot swap it because
5519 * it will mess the state of the cpu buffer.
5520 */
5521 if (atomic_read(&buffer_a->resizing))
5522 goto out_dec;
5523 if (atomic_read(&buffer_b->resizing))
5524 goto out_dec;
5525
5526 buffer_a->buffers[cpu] = cpu_buffer_b;
5527 buffer_b->buffers[cpu] = cpu_buffer_a;
5528
5529 cpu_buffer_b->buffer = buffer_a;
5530 cpu_buffer_a->buffer = buffer_b;
5531
5532 ret = 0;
5533
5534out_dec:
5535 atomic_dec(&cpu_buffer_a->record_disabled);
5536 atomic_dec(&cpu_buffer_b->record_disabled);
5537out:
5538 return ret;
5539}
5540EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5541#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5542
5543/**
5544 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5545 * @buffer: the buffer to allocate for.
5546 * @cpu: the cpu buffer to allocate.
5547 *
5548 * This function is used in conjunction with ring_buffer_read_page.
5549 * When reading a full page from the ring buffer, these functions
5550 * can be used to speed up the process. The calling function should
5551 * allocate a few pages first with this function. Then when it
5552 * needs to get pages from the ring buffer, it passes the result
5553 * of this function into ring_buffer_read_page, which will swap
5554 * the page that was allocated, with the read page of the buffer.
5555 *
5556 * Returns:
5557 * The page allocated, or ERR_PTR
5558 */
5559struct buffer_data_read_page *
5560ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5561{
5562 struct ring_buffer_per_cpu *cpu_buffer;
5563 struct buffer_data_read_page *bpage = NULL;
5564 unsigned long flags;
5565 struct page *page;
5566
5567 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5568 return ERR_PTR(-ENODEV);
5569
5570 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
5571 if (!bpage)
5572 return ERR_PTR(-ENOMEM);
5573
5574 bpage->order = buffer->subbuf_order;
5575 cpu_buffer = buffer->buffers[cpu];
5576 local_irq_save(flags);
5577 arch_spin_lock(&cpu_buffer->lock);
5578
5579 if (cpu_buffer->free_page) {
5580 bpage->data = cpu_buffer->free_page;
5581 cpu_buffer->free_page = NULL;
5582 }
5583
5584 arch_spin_unlock(&cpu_buffer->lock);
5585 local_irq_restore(flags);
5586
5587 if (bpage->data)
5588 goto out;
5589
5590 page = alloc_pages_node(cpu_to_node(cpu),
5591 GFP_KERNEL | __GFP_NORETRY | __GFP_ZERO,
5592 cpu_buffer->buffer->subbuf_order);
5593 if (!page) {
5594 kfree(bpage);
5595 return ERR_PTR(-ENOMEM);
5596 }
5597
5598 bpage->data = page_address(page);
5599
5600 out:
5601 rb_init_page(bpage->data);
5602
5603 return bpage;
5604}
5605EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5606
5607/**
5608 * ring_buffer_free_read_page - free an allocated read page
5609 * @buffer: the buffer the page was allocate for
5610 * @cpu: the cpu buffer the page came from
5611 * @data_page: the page to free
5612 *
5613 * Free a page allocated from ring_buffer_alloc_read_page.
5614 */
5615void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
5616 struct buffer_data_read_page *data_page)
5617{
5618 struct ring_buffer_per_cpu *cpu_buffer;
5619 struct buffer_data_page *bpage = data_page->data;
5620 struct page *page = virt_to_page(bpage);
5621 unsigned long flags;
5622
5623 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
5624 return;
5625
5626 cpu_buffer = buffer->buffers[cpu];
5627
5628 /*
5629 * If the page is still in use someplace else, or order of the page
5630 * is different from the subbuffer order of the buffer -
5631 * we can't reuse it
5632 */
5633 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
5634 goto out;
5635
5636 local_irq_save(flags);
5637 arch_spin_lock(&cpu_buffer->lock);
5638
5639 if (!cpu_buffer->free_page) {
5640 cpu_buffer->free_page = bpage;
5641 bpage = NULL;
5642 }
5643
5644 arch_spin_unlock(&cpu_buffer->lock);
5645 local_irq_restore(flags);
5646
5647 out:
5648 free_pages((unsigned long)bpage, data_page->order);
5649 kfree(data_page);
5650}
5651EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5652
5653/**
5654 * ring_buffer_read_page - extract a page from the ring buffer
5655 * @buffer: buffer to extract from
5656 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5657 * @len: amount to extract
5658 * @cpu: the cpu of the buffer to extract
5659 * @full: should the extraction only happen when the page is full.
5660 *
5661 * This function will pull out a page from the ring buffer and consume it.
5662 * @data_page must be the address of the variable that was returned
5663 * from ring_buffer_alloc_read_page. This is because the page might be used
5664 * to swap with a page in the ring buffer.
5665 *
5666 * for example:
5667 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5668 * if (IS_ERR(rpage))
5669 * return PTR_ERR(rpage);
5670 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
5671 * if (ret >= 0)
5672 * process_page(ring_buffer_read_page_data(rpage), ret);
5673 * ring_buffer_free_read_page(buffer, cpu, rpage);
5674 *
5675 * When @full is set, the function will not return true unless
5676 * the writer is off the reader page.
5677 *
5678 * Note: it is up to the calling functions to handle sleeps and wakeups.
5679 * The ring buffer can be used anywhere in the kernel and can not
5680 * blindly call wake_up. The layer that uses the ring buffer must be
5681 * responsible for that.
5682 *
5683 * Returns:
5684 * >=0 if data has been transferred, returns the offset of consumed data.
5685 * <0 if no data has been transferred.
5686 */
5687int ring_buffer_read_page(struct trace_buffer *buffer,
5688 struct buffer_data_read_page *data_page,
5689 size_t len, int cpu, int full)
5690{
5691 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5692 struct ring_buffer_event *event;
5693 struct buffer_data_page *bpage;
5694 struct buffer_page *reader;
5695 unsigned long missed_events;
5696 unsigned long flags;
5697 unsigned int commit;
5698 unsigned int read;
5699 u64 save_timestamp;
5700 int ret = -1;
5701
5702 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5703 goto out;
5704
5705 /*
5706 * If len is not big enough to hold the page header, then
5707 * we can not copy anything.
5708 */
5709 if (len <= BUF_PAGE_HDR_SIZE)
5710 goto out;
5711
5712 len -= BUF_PAGE_HDR_SIZE;
5713
5714 if (!data_page || !data_page->data)
5715 goto out;
5716 if (data_page->order != buffer->subbuf_order)
5717 goto out;
5718
5719 bpage = data_page->data;
5720 if (!bpage)
5721 goto out;
5722
5723 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5724
5725 reader = rb_get_reader_page(cpu_buffer);
5726 if (!reader)
5727 goto out_unlock;
5728
5729 event = rb_reader_event(cpu_buffer);
5730
5731 read = reader->read;
5732 commit = rb_page_commit(reader);
5733
5734 /* Check if any events were dropped */
5735 missed_events = cpu_buffer->lost_events;
5736
5737 /*
5738 * If this page has been partially read or
5739 * if len is not big enough to read the rest of the page or
5740 * a writer is still on the page, then
5741 * we must copy the data from the page to the buffer.
5742 * Otherwise, we can simply swap the page with the one passed in.
5743 */
5744 if (read || (len < (commit - read)) ||
5745 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5746 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5747 unsigned int rpos = read;
5748 unsigned int pos = 0;
5749 unsigned int size;
5750
5751 /*
5752 * If a full page is expected, this can still be returned
5753 * if there's been a previous partial read and the
5754 * rest of the page can be read and the commit page is off
5755 * the reader page.
5756 */
5757 if (full &&
5758 (!read || (len < (commit - read)) ||
5759 cpu_buffer->reader_page == cpu_buffer->commit_page))
5760 goto out_unlock;
5761
5762 if (len > (commit - read))
5763 len = (commit - read);
5764
5765 /* Always keep the time extend and data together */
5766 size = rb_event_ts_length(event);
5767
5768 if (len < size)
5769 goto out_unlock;
5770
5771 /* save the current timestamp, since the user will need it */
5772 save_timestamp = cpu_buffer->read_stamp;
5773
5774 /* Need to copy one event at a time */
5775 do {
5776 /* We need the size of one event, because
5777 * rb_advance_reader only advances by one event,
5778 * whereas rb_event_ts_length may include the size of
5779 * one or two events.
5780 * We have already ensured there's enough space if this
5781 * is a time extend. */
5782 size = rb_event_length(event);
5783 memcpy(bpage->data + pos, rpage->data + rpos, size);
5784
5785 len -= size;
5786
5787 rb_advance_reader(cpu_buffer);
5788 rpos = reader->read;
5789 pos += size;
5790
5791 if (rpos >= commit)
5792 break;
5793
5794 event = rb_reader_event(cpu_buffer);
5795 /* Always keep the time extend and data together */
5796 size = rb_event_ts_length(event);
5797 } while (len >= size);
5798
5799 /* update bpage */
5800 local_set(&bpage->commit, pos);
5801 bpage->time_stamp = save_timestamp;
5802
5803 /* we copied everything to the beginning */
5804 read = 0;
5805 } else {
5806 /* update the entry counter */
5807 cpu_buffer->read += rb_page_entries(reader);
5808 cpu_buffer->read_bytes += rb_page_commit(reader);
5809
5810 /* swap the pages */
5811 rb_init_page(bpage);
5812 bpage = reader->page;
5813 reader->page = data_page->data;
5814 local_set(&reader->write, 0);
5815 local_set(&reader->entries, 0);
5816 reader->read = 0;
5817 data_page->data = bpage;
5818
5819 /*
5820 * Use the real_end for the data size,
5821 * This gives us a chance to store the lost events
5822 * on the page.
5823 */
5824 if (reader->real_end)
5825 local_set(&bpage->commit, reader->real_end);
5826 }
5827 ret = read;
5828
5829 cpu_buffer->lost_events = 0;
5830
5831 commit = local_read(&bpage->commit);
5832 /*
5833 * Set a flag in the commit field if we lost events
5834 */
5835 if (missed_events) {
5836 /* If there is room at the end of the page to save the
5837 * missed events, then record it there.
5838 */
5839 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
5840 memcpy(&bpage->data[commit], &missed_events,
5841 sizeof(missed_events));
5842 local_add(RB_MISSED_STORED, &bpage->commit);
5843 commit += sizeof(missed_events);
5844 }
5845 local_add(RB_MISSED_EVENTS, &bpage->commit);
5846 }
5847
5848 /*
5849 * This page may be off to user land. Zero it out here.
5850 */
5851 if (commit < buffer->subbuf_size)
5852 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
5853
5854 out_unlock:
5855 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5856
5857 out:
5858 return ret;
5859}
5860EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5861
5862/**
5863 * ring_buffer_read_page_data - get pointer to the data in the page.
5864 * @page: the page to get the data from
5865 *
5866 * Returns pointer to the actual data in this page.
5867 */
5868void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
5869{
5870 return page->data;
5871}
5872EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
5873
5874/**
5875 * ring_buffer_subbuf_size_get - get size of the sub buffer.
5876 * @buffer: the buffer to get the sub buffer size from
5877 *
5878 * Returns size of the sub buffer, in bytes.
5879 */
5880int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
5881{
5882 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
5883}
5884EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
5885
5886/**
5887 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
5888 * @buffer: The ring_buffer to get the system sub page order from
5889 *
5890 * By default, one ring buffer sub page equals to one system page. This parameter
5891 * is configurable, per ring buffer. The size of the ring buffer sub page can be
5892 * extended, but must be an order of system page size.
5893 *
5894 * Returns the order of buffer sub page size, in system pages:
5895 * 0 means the sub buffer size is 1 system page and so forth.
5896 * In case of an error < 0 is returned.
5897 */
5898int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
5899{
5900 if (!buffer)
5901 return -EINVAL;
5902
5903 return buffer->subbuf_order;
5904}
5905EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
5906
5907/**
5908 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
5909 * @buffer: The ring_buffer to set the new page size.
5910 * @order: Order of the system pages in one sub buffer page
5911 *
5912 * By default, one ring buffer pages equals to one system page. This API can be
5913 * used to set new size of the ring buffer page. The size must be order of
5914 * system page size, that's why the input parameter @order is the order of
5915 * system pages that are allocated for one ring buffer page:
5916 * 0 - 1 system page
5917 * 1 - 2 system pages
5918 * 3 - 4 system pages
5919 * ...
5920 *
5921 * Returns 0 on success or < 0 in case of an error.
5922 */
5923int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
5924{
5925 struct ring_buffer_per_cpu *cpu_buffer;
5926 struct buffer_page *bpage, *tmp;
5927 int old_order, old_size;
5928 int nr_pages;
5929 int psize;
5930 int err;
5931 int cpu;
5932
5933 if (!buffer || order < 0)
5934 return -EINVAL;
5935
5936 if (buffer->subbuf_order == order)
5937 return 0;
5938
5939 psize = (1 << order) * PAGE_SIZE;
5940 if (psize <= BUF_PAGE_HDR_SIZE)
5941 return -EINVAL;
5942
5943 /* Size of a subbuf cannot be greater than the write counter */
5944 if (psize > RB_WRITE_MASK + 1)
5945 return -EINVAL;
5946
5947 old_order = buffer->subbuf_order;
5948 old_size = buffer->subbuf_size;
5949
5950 /* prevent another thread from changing buffer sizes */
5951 mutex_lock(&buffer->mutex);
5952 atomic_inc(&buffer->record_disabled);
5953
5954 /* Make sure all commits have finished */
5955 synchronize_rcu();
5956
5957 buffer->subbuf_order = order;
5958 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
5959
5960 /* Make sure all new buffers are allocated, before deleting the old ones */
5961 for_each_buffer_cpu(buffer, cpu) {
5962
5963 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5964 continue;
5965
5966 cpu_buffer = buffer->buffers[cpu];
5967
5968 /* Update the number of pages to match the new size */
5969 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
5970 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
5971
5972 /* we need a minimum of two pages */
5973 if (nr_pages < 2)
5974 nr_pages = 2;
5975
5976 cpu_buffer->nr_pages_to_update = nr_pages;
5977
5978 /* Include the reader page */
5979 nr_pages++;
5980
5981 /* Allocate the new size buffer */
5982 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5983 if (__rb_allocate_pages(cpu_buffer, nr_pages,
5984 &cpu_buffer->new_pages)) {
5985 /* not enough memory for new pages */
5986 err = -ENOMEM;
5987 goto error;
5988 }
5989 }
5990
5991 for_each_buffer_cpu(buffer, cpu) {
5992
5993 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5994 continue;
5995
5996 cpu_buffer = buffer->buffers[cpu];
5997
5998 /* Clear the head bit to make the link list normal to read */
5999 rb_head_page_deactivate(cpu_buffer);
6000
6001 /* Now walk the list and free all the old sub buffers */
6002 list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) {
6003 list_del_init(&bpage->list);
6004 free_buffer_page(bpage);
6005 }
6006 /* The above loop stopped an the last page needing to be freed */
6007 bpage = list_entry(cpu_buffer->pages, struct buffer_page, list);
6008 free_buffer_page(bpage);
6009
6010 /* Free the current reader page */
6011 free_buffer_page(cpu_buffer->reader_page);
6012
6013 /* One page was allocated for the reader page */
6014 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6015 struct buffer_page, list);
6016 list_del_init(&cpu_buffer->reader_page->list);
6017
6018 /* The cpu_buffer pages are a link list with no head */
6019 cpu_buffer->pages = cpu_buffer->new_pages.next;
6020 cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev;
6021 cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next;
6022
6023 /* Clear the new_pages list */
6024 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6025
6026 cpu_buffer->head_page
6027 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6028 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6029
6030 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6031 cpu_buffer->nr_pages_to_update = 0;
6032
6033 free_pages((unsigned long)cpu_buffer->free_page, old_order);
6034 cpu_buffer->free_page = NULL;
6035
6036 rb_head_page_activate(cpu_buffer);
6037
6038 rb_check_pages(cpu_buffer);
6039 }
6040
6041 atomic_dec(&buffer->record_disabled);
6042 mutex_unlock(&buffer->mutex);
6043
6044 return 0;
6045
6046error:
6047 buffer->subbuf_order = old_order;
6048 buffer->subbuf_size = old_size;
6049
6050 atomic_dec(&buffer->record_disabled);
6051 mutex_unlock(&buffer->mutex);
6052
6053 for_each_buffer_cpu(buffer, cpu) {
6054 cpu_buffer = buffer->buffers[cpu];
6055
6056 if (!cpu_buffer->nr_pages_to_update)
6057 continue;
6058
6059 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6060 list_del_init(&bpage->list);
6061 free_buffer_page(bpage);
6062 }
6063 }
6064
6065 return err;
6066}
6067EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6068
6069/*
6070 * We only allocate new buffers, never free them if the CPU goes down.
6071 * If we were to free the buffer, then the user would lose any trace that was in
6072 * the buffer.
6073 */
6074int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
6075{
6076 struct trace_buffer *buffer;
6077 long nr_pages_same;
6078 int cpu_i;
6079 unsigned long nr_pages;
6080
6081 buffer = container_of(node, struct trace_buffer, node);
6082 if (cpumask_test_cpu(cpu, buffer->cpumask))
6083 return 0;
6084
6085 nr_pages = 0;
6086 nr_pages_same = 1;
6087 /* check if all cpu sizes are same */
6088 for_each_buffer_cpu(buffer, cpu_i) {
6089 /* fill in the size from first enabled cpu */
6090 if (nr_pages == 0)
6091 nr_pages = buffer->buffers[cpu_i]->nr_pages;
6092 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
6093 nr_pages_same = 0;
6094 break;
6095 }
6096 }
6097 /* allocate minimum pages, user can later expand it */
6098 if (!nr_pages_same)
6099 nr_pages = 2;
6100 buffer->buffers[cpu] =
6101 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
6102 if (!buffer->buffers[cpu]) {
6103 WARN(1, "failed to allocate ring buffer on CPU %u\n",
6104 cpu);
6105 return -ENOMEM;
6106 }
6107 smp_wmb();
6108 cpumask_set_cpu(cpu, buffer->cpumask);
6109 return 0;
6110}
6111
6112#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
6113/*
6114 * This is a basic integrity check of the ring buffer.
6115 * Late in the boot cycle this test will run when configured in.
6116 * It will kick off a thread per CPU that will go into a loop
6117 * writing to the per cpu ring buffer various sizes of data.
6118 * Some of the data will be large items, some small.
6119 *
6120 * Another thread is created that goes into a spin, sending out
6121 * IPIs to the other CPUs to also write into the ring buffer.
6122 * this is to test the nesting ability of the buffer.
6123 *
6124 * Basic stats are recorded and reported. If something in the
6125 * ring buffer should happen that's not expected, a big warning
6126 * is displayed and all ring buffers are disabled.
6127 */
6128static struct task_struct *rb_threads[NR_CPUS] __initdata;
6129
6130struct rb_test_data {
6131 struct trace_buffer *buffer;
6132 unsigned long events;
6133 unsigned long bytes_written;
6134 unsigned long bytes_alloc;
6135 unsigned long bytes_dropped;
6136 unsigned long events_nested;
6137 unsigned long bytes_written_nested;
6138 unsigned long bytes_alloc_nested;
6139 unsigned long bytes_dropped_nested;
6140 int min_size_nested;
6141 int max_size_nested;
6142 int max_size;
6143 int min_size;
6144 int cpu;
6145 int cnt;
6146};
6147
6148static struct rb_test_data rb_data[NR_CPUS] __initdata;
6149
6150/* 1 meg per cpu */
6151#define RB_TEST_BUFFER_SIZE 1048576
6152
6153static char rb_string[] __initdata =
6154 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
6155 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
6156 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
6157
6158static bool rb_test_started __initdata;
6159
6160struct rb_item {
6161 int size;
6162 char str[];
6163};
6164
6165static __init int rb_write_something(struct rb_test_data *data, bool nested)
6166{
6167 struct ring_buffer_event *event;
6168 struct rb_item *item;
6169 bool started;
6170 int event_len;
6171 int size;
6172 int len;
6173 int cnt;
6174
6175 /* Have nested writes different that what is written */
6176 cnt = data->cnt + (nested ? 27 : 0);
6177
6178 /* Multiply cnt by ~e, to make some unique increment */
6179 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
6180
6181 len = size + sizeof(struct rb_item);
6182
6183 started = rb_test_started;
6184 /* read rb_test_started before checking buffer enabled */
6185 smp_rmb();
6186
6187 event = ring_buffer_lock_reserve(data->buffer, len);
6188 if (!event) {
6189 /* Ignore dropped events before test starts. */
6190 if (started) {
6191 if (nested)
6192 data->bytes_dropped += len;
6193 else
6194 data->bytes_dropped_nested += len;
6195 }
6196 return len;
6197 }
6198
6199 event_len = ring_buffer_event_length(event);
6200
6201 if (RB_WARN_ON(data->buffer, event_len < len))
6202 goto out;
6203
6204 item = ring_buffer_event_data(event);
6205 item->size = size;
6206 memcpy(item->str, rb_string, size);
6207
6208 if (nested) {
6209 data->bytes_alloc_nested += event_len;
6210 data->bytes_written_nested += len;
6211 data->events_nested++;
6212 if (!data->min_size_nested || len < data->min_size_nested)
6213 data->min_size_nested = len;
6214 if (len > data->max_size_nested)
6215 data->max_size_nested = len;
6216 } else {
6217 data->bytes_alloc += event_len;
6218 data->bytes_written += len;
6219 data->events++;
6220 if (!data->min_size || len < data->min_size)
6221 data->max_size = len;
6222 if (len > data->max_size)
6223 data->max_size = len;
6224 }
6225
6226 out:
6227 ring_buffer_unlock_commit(data->buffer);
6228
6229 return 0;
6230}
6231
6232static __init int rb_test(void *arg)
6233{
6234 struct rb_test_data *data = arg;
6235
6236 while (!kthread_should_stop()) {
6237 rb_write_something(data, false);
6238 data->cnt++;
6239
6240 set_current_state(TASK_INTERRUPTIBLE);
6241 /* Now sleep between a min of 100-300us and a max of 1ms */
6242 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
6243 }
6244
6245 return 0;
6246}
6247
6248static __init void rb_ipi(void *ignore)
6249{
6250 struct rb_test_data *data;
6251 int cpu = smp_processor_id();
6252
6253 data = &rb_data[cpu];
6254 rb_write_something(data, true);
6255}
6256
6257static __init int rb_hammer_test(void *arg)
6258{
6259 while (!kthread_should_stop()) {
6260
6261 /* Send an IPI to all cpus to write data! */
6262 smp_call_function(rb_ipi, NULL, 1);
6263 /* No sleep, but for non preempt, let others run */
6264 schedule();
6265 }
6266
6267 return 0;
6268}
6269
6270static __init int test_ringbuffer(void)
6271{
6272 struct task_struct *rb_hammer;
6273 struct trace_buffer *buffer;
6274 int cpu;
6275 int ret = 0;
6276
6277 if (security_locked_down(LOCKDOWN_TRACEFS)) {
6278 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6279 return 0;
6280 }
6281
6282 pr_info("Running ring buffer tests...\n");
6283
6284 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6285 if (WARN_ON(!buffer))
6286 return 0;
6287
6288 /* Disable buffer so that threads can't write to it yet */
6289 ring_buffer_record_off(buffer);
6290
6291 for_each_online_cpu(cpu) {
6292 rb_data[cpu].buffer = buffer;
6293 rb_data[cpu].cpu = cpu;
6294 rb_data[cpu].cnt = cpu;
6295 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
6296 cpu, "rbtester/%u");
6297 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6298 pr_cont("FAILED\n");
6299 ret = PTR_ERR(rb_threads[cpu]);
6300 goto out_free;
6301 }
6302 }
6303
6304 /* Now create the rb hammer! */
6305 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6306 if (WARN_ON(IS_ERR(rb_hammer))) {
6307 pr_cont("FAILED\n");
6308 ret = PTR_ERR(rb_hammer);
6309 goto out_free;
6310 }
6311
6312 ring_buffer_record_on(buffer);
6313 /*
6314 * Show buffer is enabled before setting rb_test_started.
6315 * Yes there's a small race window where events could be
6316 * dropped and the thread wont catch it. But when a ring
6317 * buffer gets enabled, there will always be some kind of
6318 * delay before other CPUs see it. Thus, we don't care about
6319 * those dropped events. We care about events dropped after
6320 * the threads see that the buffer is active.
6321 */
6322 smp_wmb();
6323 rb_test_started = true;
6324
6325 set_current_state(TASK_INTERRUPTIBLE);
6326 /* Just run for 10 seconds */;
6327 schedule_timeout(10 * HZ);
6328
6329 kthread_stop(rb_hammer);
6330
6331 out_free:
6332 for_each_online_cpu(cpu) {
6333 if (!rb_threads[cpu])
6334 break;
6335 kthread_stop(rb_threads[cpu]);
6336 }
6337 if (ret) {
6338 ring_buffer_free(buffer);
6339 return ret;
6340 }
6341
6342 /* Report! */
6343 pr_info("finished\n");
6344 for_each_online_cpu(cpu) {
6345 struct ring_buffer_event *event;
6346 struct rb_test_data *data = &rb_data[cpu];
6347 struct rb_item *item;
6348 unsigned long total_events;
6349 unsigned long total_dropped;
6350 unsigned long total_written;
6351 unsigned long total_alloc;
6352 unsigned long total_read = 0;
6353 unsigned long total_size = 0;
6354 unsigned long total_len = 0;
6355 unsigned long total_lost = 0;
6356 unsigned long lost;
6357 int big_event_size;
6358 int small_event_size;
6359
6360 ret = -1;
6361
6362 total_events = data->events + data->events_nested;
6363 total_written = data->bytes_written + data->bytes_written_nested;
6364 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6365 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6366
6367 big_event_size = data->max_size + data->max_size_nested;
6368 small_event_size = data->min_size + data->min_size_nested;
6369
6370 pr_info("CPU %d:\n", cpu);
6371 pr_info(" events: %ld\n", total_events);
6372 pr_info(" dropped bytes: %ld\n", total_dropped);
6373 pr_info(" alloced bytes: %ld\n", total_alloc);
6374 pr_info(" written bytes: %ld\n", total_written);
6375 pr_info(" biggest event: %d\n", big_event_size);
6376 pr_info(" smallest event: %d\n", small_event_size);
6377
6378 if (RB_WARN_ON(buffer, total_dropped))
6379 break;
6380
6381 ret = 0;
6382
6383 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6384 total_lost += lost;
6385 item = ring_buffer_event_data(event);
6386 total_len += ring_buffer_event_length(event);
6387 total_size += item->size + sizeof(struct rb_item);
6388 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
6389 pr_info("FAILED!\n");
6390 pr_info("buffer had: %.*s\n", item->size, item->str);
6391 pr_info("expected: %.*s\n", item->size, rb_string);
6392 RB_WARN_ON(buffer, 1);
6393 ret = -1;
6394 break;
6395 }
6396 total_read++;
6397 }
6398 if (ret)
6399 break;
6400
6401 ret = -1;
6402
6403 pr_info(" read events: %ld\n", total_read);
6404 pr_info(" lost events: %ld\n", total_lost);
6405 pr_info(" total events: %ld\n", total_lost + total_read);
6406 pr_info(" recorded len bytes: %ld\n", total_len);
6407 pr_info(" recorded size bytes: %ld\n", total_size);
6408 if (total_lost) {
6409 pr_info(" With dropped events, record len and size may not match\n"
6410 " alloced and written from above\n");
6411 } else {
6412 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6413 total_size != total_written))
6414 break;
6415 }
6416 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6417 break;
6418
6419 ret = 0;
6420 }
6421 if (!ret)
6422 pr_info("Ring buffer PASSED!\n");
6423
6424 ring_buffer_free(buffer);
6425 return 0;
6426}
6427
6428late_initcall(test_ringbuffer);
6429#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */