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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/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/local.h>
31
32/*
33 * The "absolute" timestamp in the buffer is only 59 bits.
34 * If a clock has the 5 MSBs set, it needs to be saved and
35 * reinserted.
36 */
37#define TS_MSB (0xf8ULL << 56)
38#define ABS_TS_MASK (~TS_MSB)
39
40static void update_pages_handler(struct work_struct *work);
41
42/*
43 * The ring buffer header is special. We must manually up keep it.
44 */
45int ring_buffer_print_entry_header(struct trace_seq *s)
46{
47 trace_seq_puts(s, "# compressed entry header\n");
48 trace_seq_puts(s, "\ttype_len : 5 bits\n");
49 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
50 trace_seq_puts(s, "\tarray : 32 bits\n");
51 trace_seq_putc(s, '\n');
52 trace_seq_printf(s, "\tpadding : type == %d\n",
53 RINGBUF_TYPE_PADDING);
54 trace_seq_printf(s, "\ttime_extend : type == %d\n",
55 RINGBUF_TYPE_TIME_EXTEND);
56 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
57 RINGBUF_TYPE_TIME_STAMP);
58 trace_seq_printf(s, "\tdata max type_len == %d\n",
59 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
60
61 return !trace_seq_has_overflowed(s);
62}
63
64/*
65 * The ring buffer is made up of a list of pages. A separate list of pages is
66 * allocated for each CPU. A writer may only write to a buffer that is
67 * associated with the CPU it is currently executing on. A reader may read
68 * from any per cpu buffer.
69 *
70 * The reader is special. For each per cpu buffer, the reader has its own
71 * reader page. When a reader has read the entire reader page, this reader
72 * page is swapped with another page in the ring buffer.
73 *
74 * Now, as long as the writer is off the reader page, the reader can do what
75 * ever it wants with that page. The writer will never write to that page
76 * again (as long as it is out of the ring buffer).
77 *
78 * Here's some silly ASCII art.
79 *
80 * +------+
81 * |reader| RING BUFFER
82 * |page |
83 * +------+ +---+ +---+ +---+
84 * | |-->| |-->| |
85 * +---+ +---+ +---+
86 * ^ |
87 * | |
88 * +---------------+
89 *
90 *
91 * +------+
92 * |reader| RING BUFFER
93 * |page |------------------v
94 * +------+ +---+ +---+ +---+
95 * | |-->| |-->| |
96 * +---+ +---+ +---+
97 * ^ |
98 * | |
99 * +---------------+
100 *
101 *
102 * +------+
103 * |reader| RING BUFFER
104 * |page |------------------v
105 * +------+ +---+ +---+ +---+
106 * ^ | |-->| |-->| |
107 * | +---+ +---+ +---+
108 * | |
109 * | |
110 * +------------------------------+
111 *
112 *
113 * +------+
114 * |buffer| RING BUFFER
115 * |page |------------------v
116 * +------+ +---+ +---+ +---+
117 * ^ | | | |-->| |
118 * | New +---+ +---+ +---+
119 * | Reader------^ |
120 * | page |
121 * +------------------------------+
122 *
123 *
124 * After we make this swap, the reader can hand this page off to the splice
125 * code and be done with it. It can even allocate a new page if it needs to
126 * and swap that into the ring buffer.
127 *
128 * We will be using cmpxchg soon to make all this lockless.
129 *
130 */
131
132/* Used for individual buffers (after the counter) */
133#define RB_BUFFER_OFF (1 << 20)
134
135#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
136
137#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
138#define RB_ALIGNMENT 4U
139#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
140#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
141
142#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
143# define RB_FORCE_8BYTE_ALIGNMENT 0
144# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
145#else
146# define RB_FORCE_8BYTE_ALIGNMENT 1
147# define RB_ARCH_ALIGNMENT 8U
148#endif
149
150#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
151
152/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
153#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
154
155enum {
156 RB_LEN_TIME_EXTEND = 8,
157 RB_LEN_TIME_STAMP = 8,
158};
159
160#define skip_time_extend(event) \
161 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
162
163#define extended_time(event) \
164 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
165
166static inline int rb_null_event(struct ring_buffer_event *event)
167{
168 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
169}
170
171static void rb_event_set_padding(struct ring_buffer_event *event)
172{
173 /* padding has a NULL time_delta */
174 event->type_len = RINGBUF_TYPE_PADDING;
175 event->time_delta = 0;
176}
177
178static unsigned
179rb_event_data_length(struct ring_buffer_event *event)
180{
181 unsigned length;
182
183 if (event->type_len)
184 length = event->type_len * RB_ALIGNMENT;
185 else
186 length = event->array[0];
187 return length + RB_EVNT_HDR_SIZE;
188}
189
190/*
191 * Return the length of the given event. Will return
192 * the length of the time extend if the event is a
193 * time extend.
194 */
195static inline unsigned
196rb_event_length(struct ring_buffer_event *event)
197{
198 switch (event->type_len) {
199 case RINGBUF_TYPE_PADDING:
200 if (rb_null_event(event))
201 /* undefined */
202 return -1;
203 return event->array[0] + RB_EVNT_HDR_SIZE;
204
205 case RINGBUF_TYPE_TIME_EXTEND:
206 return RB_LEN_TIME_EXTEND;
207
208 case RINGBUF_TYPE_TIME_STAMP:
209 return RB_LEN_TIME_STAMP;
210
211 case RINGBUF_TYPE_DATA:
212 return rb_event_data_length(event);
213 default:
214 WARN_ON_ONCE(1);
215 }
216 /* not hit */
217 return 0;
218}
219
220/*
221 * Return total length of time extend and data,
222 * or just the event length for all other events.
223 */
224static inline unsigned
225rb_event_ts_length(struct ring_buffer_event *event)
226{
227 unsigned len = 0;
228
229 if (extended_time(event)) {
230 /* time extends include the data event after it */
231 len = RB_LEN_TIME_EXTEND;
232 event = skip_time_extend(event);
233 }
234 return len + rb_event_length(event);
235}
236
237/**
238 * ring_buffer_event_length - return the length of the event
239 * @event: the event to get the length of
240 *
241 * Returns the size of the data load of a data event.
242 * If the event is something other than a data event, it
243 * returns the size of the event itself. With the exception
244 * of a TIME EXTEND, where it still returns the size of the
245 * data load of the data event after it.
246 */
247unsigned ring_buffer_event_length(struct ring_buffer_event *event)
248{
249 unsigned length;
250
251 if (extended_time(event))
252 event = skip_time_extend(event);
253
254 length = rb_event_length(event);
255 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
256 return length;
257 length -= RB_EVNT_HDR_SIZE;
258 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
259 length -= sizeof(event->array[0]);
260 return length;
261}
262EXPORT_SYMBOL_GPL(ring_buffer_event_length);
263
264/* inline for ring buffer fast paths */
265static __always_inline void *
266rb_event_data(struct ring_buffer_event *event)
267{
268 if (extended_time(event))
269 event = skip_time_extend(event);
270 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
271 /* If length is in len field, then array[0] has the data */
272 if (event->type_len)
273 return (void *)&event->array[0];
274 /* Otherwise length is in array[0] and array[1] has the data */
275 return (void *)&event->array[1];
276}
277
278/**
279 * ring_buffer_event_data - return the data of the event
280 * @event: the event to get the data from
281 */
282void *ring_buffer_event_data(struct ring_buffer_event *event)
283{
284 return rb_event_data(event);
285}
286EXPORT_SYMBOL_GPL(ring_buffer_event_data);
287
288#define for_each_buffer_cpu(buffer, cpu) \
289 for_each_cpu(cpu, buffer->cpumask)
290
291#define for_each_online_buffer_cpu(buffer, cpu) \
292 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
293
294#define TS_SHIFT 27
295#define TS_MASK ((1ULL << TS_SHIFT) - 1)
296#define TS_DELTA_TEST (~TS_MASK)
297
298static u64 rb_event_time_stamp(struct ring_buffer_event *event)
299{
300 u64 ts;
301
302 ts = event->array[0];
303 ts <<= TS_SHIFT;
304 ts += event->time_delta;
305
306 return ts;
307}
308
309/* Flag when events were overwritten */
310#define RB_MISSED_EVENTS (1 << 31)
311/* Missed count stored at end */
312#define RB_MISSED_STORED (1 << 30)
313
314struct buffer_data_page {
315 u64 time_stamp; /* page time stamp */
316 local_t commit; /* write committed index */
317 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
318};
319
320/*
321 * Note, the buffer_page list must be first. The buffer pages
322 * are allocated in cache lines, which means that each buffer
323 * page will be at the beginning of a cache line, and thus
324 * the least significant bits will be zero. We use this to
325 * add flags in the list struct pointers, to make the ring buffer
326 * lockless.
327 */
328struct buffer_page {
329 struct list_head list; /* list of buffer pages */
330 local_t write; /* index for next write */
331 unsigned read; /* index for next read */
332 local_t entries; /* entries on this page */
333 unsigned long real_end; /* real end of data */
334 struct buffer_data_page *page; /* Actual data page */
335};
336
337/*
338 * The buffer page counters, write and entries, must be reset
339 * atomically when crossing page boundaries. To synchronize this
340 * update, two counters are inserted into the number. One is
341 * the actual counter for the write position or count on the page.
342 *
343 * The other is a counter of updaters. Before an update happens
344 * the update partition of the counter is incremented. This will
345 * allow the updater to update the counter atomically.
346 *
347 * The counter is 20 bits, and the state data is 12.
348 */
349#define RB_WRITE_MASK 0xfffff
350#define RB_WRITE_INTCNT (1 << 20)
351
352static void rb_init_page(struct buffer_data_page *bpage)
353{
354 local_set(&bpage->commit, 0);
355}
356
357/*
358 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
359 * this issue out.
360 */
361static void free_buffer_page(struct buffer_page *bpage)
362{
363 free_page((unsigned long)bpage->page);
364 kfree(bpage);
365}
366
367/*
368 * We need to fit the time_stamp delta into 27 bits.
369 */
370static inline int test_time_stamp(u64 delta)
371{
372 if (delta & TS_DELTA_TEST)
373 return 1;
374 return 0;
375}
376
377#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
378
379/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
380#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
381
382int ring_buffer_print_page_header(struct trace_seq *s)
383{
384 struct buffer_data_page field;
385
386 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
387 "offset:0;\tsize:%u;\tsigned:%u;\n",
388 (unsigned int)sizeof(field.time_stamp),
389 (unsigned int)is_signed_type(u64));
390
391 trace_seq_printf(s, "\tfield: local_t commit;\t"
392 "offset:%u;\tsize:%u;\tsigned:%u;\n",
393 (unsigned int)offsetof(typeof(field), commit),
394 (unsigned int)sizeof(field.commit),
395 (unsigned int)is_signed_type(long));
396
397 trace_seq_printf(s, "\tfield: int overwrite;\t"
398 "offset:%u;\tsize:%u;\tsigned:%u;\n",
399 (unsigned int)offsetof(typeof(field), commit),
400 1,
401 (unsigned int)is_signed_type(long));
402
403 trace_seq_printf(s, "\tfield: char data;\t"
404 "offset:%u;\tsize:%u;\tsigned:%u;\n",
405 (unsigned int)offsetof(typeof(field), data),
406 (unsigned int)BUF_PAGE_SIZE,
407 (unsigned int)is_signed_type(char));
408
409 return !trace_seq_has_overflowed(s);
410}
411
412struct rb_irq_work {
413 struct irq_work work;
414 wait_queue_head_t waiters;
415 wait_queue_head_t full_waiters;
416 long wait_index;
417 bool waiters_pending;
418 bool full_waiters_pending;
419 bool wakeup_full;
420};
421
422/*
423 * Structure to hold event state and handle nested events.
424 */
425struct rb_event_info {
426 u64 ts;
427 u64 delta;
428 u64 before;
429 u64 after;
430 unsigned long length;
431 struct buffer_page *tail_page;
432 int add_timestamp;
433};
434
435/*
436 * Used for the add_timestamp
437 * NONE
438 * EXTEND - wants a time extend
439 * ABSOLUTE - the buffer requests all events to have absolute time stamps
440 * FORCE - force a full time stamp.
441 */
442enum {
443 RB_ADD_STAMP_NONE = 0,
444 RB_ADD_STAMP_EXTEND = BIT(1),
445 RB_ADD_STAMP_ABSOLUTE = BIT(2),
446 RB_ADD_STAMP_FORCE = BIT(3)
447};
448/*
449 * Used for which event context the event is in.
450 * TRANSITION = 0
451 * NMI = 1
452 * IRQ = 2
453 * SOFTIRQ = 3
454 * NORMAL = 4
455 *
456 * See trace_recursive_lock() comment below for more details.
457 */
458enum {
459 RB_CTX_TRANSITION,
460 RB_CTX_NMI,
461 RB_CTX_IRQ,
462 RB_CTX_SOFTIRQ,
463 RB_CTX_NORMAL,
464 RB_CTX_MAX
465};
466
467#if BITS_PER_LONG == 32
468#define RB_TIME_32
469#endif
470
471/* To test on 64 bit machines */
472//#define RB_TIME_32
473
474#ifdef RB_TIME_32
475
476struct rb_time_struct {
477 local_t cnt;
478 local_t top;
479 local_t bottom;
480 local_t msb;
481};
482#else
483#include <asm/local64.h>
484struct rb_time_struct {
485 local64_t time;
486};
487#endif
488typedef struct rb_time_struct rb_time_t;
489
490#define MAX_NEST 5
491
492/*
493 * head_page == tail_page && head == tail then buffer is empty.
494 */
495struct ring_buffer_per_cpu {
496 int cpu;
497 atomic_t record_disabled;
498 atomic_t resize_disabled;
499 struct trace_buffer *buffer;
500 raw_spinlock_t reader_lock; /* serialize readers */
501 arch_spinlock_t lock;
502 struct lock_class_key lock_key;
503 struct buffer_data_page *free_page;
504 unsigned long nr_pages;
505 unsigned int current_context;
506 struct list_head *pages;
507 struct buffer_page *head_page; /* read from head */
508 struct buffer_page *tail_page; /* write to tail */
509 struct buffer_page *commit_page; /* committed pages */
510 struct buffer_page *reader_page;
511 unsigned long lost_events;
512 unsigned long last_overrun;
513 unsigned long nest;
514 local_t entries_bytes;
515 local_t entries;
516 local_t overrun;
517 local_t commit_overrun;
518 local_t dropped_events;
519 local_t committing;
520 local_t commits;
521 local_t pages_touched;
522 local_t pages_lost;
523 local_t pages_read;
524 long last_pages_touch;
525 size_t shortest_full;
526 unsigned long read;
527 unsigned long read_bytes;
528 rb_time_t write_stamp;
529 rb_time_t before_stamp;
530 u64 event_stamp[MAX_NEST];
531 u64 read_stamp;
532 /* ring buffer pages to update, > 0 to add, < 0 to remove */
533 long nr_pages_to_update;
534 struct list_head new_pages; /* new pages to add */
535 struct work_struct update_pages_work;
536 struct completion update_done;
537
538 struct rb_irq_work irq_work;
539};
540
541struct trace_buffer {
542 unsigned flags;
543 int cpus;
544 atomic_t record_disabled;
545 cpumask_var_t cpumask;
546
547 struct lock_class_key *reader_lock_key;
548
549 struct mutex mutex;
550
551 struct ring_buffer_per_cpu **buffers;
552
553 struct hlist_node node;
554 u64 (*clock)(void);
555
556 struct rb_irq_work irq_work;
557 bool time_stamp_abs;
558};
559
560struct ring_buffer_iter {
561 struct ring_buffer_per_cpu *cpu_buffer;
562 unsigned long head;
563 unsigned long next_event;
564 struct buffer_page *head_page;
565 struct buffer_page *cache_reader_page;
566 unsigned long cache_read;
567 u64 read_stamp;
568 u64 page_stamp;
569 struct ring_buffer_event *event;
570 int missed_events;
571};
572
573#ifdef RB_TIME_32
574
575/*
576 * On 32 bit machines, local64_t is very expensive. As the ring
577 * buffer doesn't need all the features of a true 64 bit atomic,
578 * on 32 bit, it uses these functions (64 still uses local64_t).
579 *
580 * For the ring buffer, 64 bit required operations for the time is
581 * the following:
582 *
583 * - Reads may fail if it interrupted a modification of the time stamp.
584 * It will succeed if it did not interrupt another write even if
585 * the read itself is interrupted by a write.
586 * It returns whether it was successful or not.
587 *
588 * - Writes always succeed and will overwrite other writes and writes
589 * that were done by events interrupting the current write.
590 *
591 * - A write followed by a read of the same time stamp will always succeed,
592 * but may not contain the same value.
593 *
594 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
595 * Other than that, it acts like a normal cmpxchg.
596 *
597 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
598 * (bottom being the least significant 30 bits of the 60 bit time stamp).
599 *
600 * The two most significant bits of each half holds a 2 bit counter (0-3).
601 * Each update will increment this counter by one.
602 * When reading the top and bottom, if the two counter bits match then the
603 * top and bottom together make a valid 60 bit number.
604 */
605#define RB_TIME_SHIFT 30
606#define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
607#define RB_TIME_MSB_SHIFT 60
608
609static inline int rb_time_cnt(unsigned long val)
610{
611 return (val >> RB_TIME_SHIFT) & 3;
612}
613
614static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
615{
616 u64 val;
617
618 val = top & RB_TIME_VAL_MASK;
619 val <<= RB_TIME_SHIFT;
620 val |= bottom & RB_TIME_VAL_MASK;
621
622 return val;
623}
624
625static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
626{
627 unsigned long top, bottom, msb;
628 unsigned long c;
629
630 /*
631 * If the read is interrupted by a write, then the cnt will
632 * be different. Loop until both top and bottom have been read
633 * without interruption.
634 */
635 do {
636 c = local_read(&t->cnt);
637 top = local_read(&t->top);
638 bottom = local_read(&t->bottom);
639 msb = local_read(&t->msb);
640 } while (c != local_read(&t->cnt));
641
642 *cnt = rb_time_cnt(top);
643
644 /* If top and bottom counts don't match, this interrupted a write */
645 if (*cnt != rb_time_cnt(bottom))
646 return false;
647
648 /* The shift to msb will lose its cnt bits */
649 *ret = rb_time_val(top, bottom) | ((u64)msb << RB_TIME_MSB_SHIFT);
650 return true;
651}
652
653static bool rb_time_read(rb_time_t *t, u64 *ret)
654{
655 unsigned long cnt;
656
657 return __rb_time_read(t, ret, &cnt);
658}
659
660static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
661{
662 return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
663}
664
665static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom,
666 unsigned long *msb)
667{
668 *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
669 *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
670 *msb = (unsigned long)(val >> RB_TIME_MSB_SHIFT);
671}
672
673static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
674{
675 val = rb_time_val_cnt(val, cnt);
676 local_set(t, val);
677}
678
679static void rb_time_set(rb_time_t *t, u64 val)
680{
681 unsigned long cnt, top, bottom, msb;
682
683 rb_time_split(val, &top, &bottom, &msb);
684
685 /* Writes always succeed with a valid number even if it gets interrupted. */
686 do {
687 cnt = local_inc_return(&t->cnt);
688 rb_time_val_set(&t->top, top, cnt);
689 rb_time_val_set(&t->bottom, bottom, cnt);
690 rb_time_val_set(&t->msb, val >> RB_TIME_MSB_SHIFT, cnt);
691 } while (cnt != local_read(&t->cnt));
692}
693
694static inline bool
695rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
696{
697 unsigned long ret;
698
699 ret = local_cmpxchg(l, expect, set);
700 return ret == expect;
701}
702
703static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
704{
705 unsigned long cnt, top, bottom, msb;
706 unsigned long cnt2, top2, bottom2, msb2;
707 u64 val;
708
709 /* The cmpxchg always fails if it interrupted an update */
710 if (!__rb_time_read(t, &val, &cnt2))
711 return false;
712
713 if (val != expect)
714 return false;
715
716 cnt = local_read(&t->cnt);
717 if ((cnt & 3) != cnt2)
718 return false;
719
720 cnt2 = cnt + 1;
721
722 rb_time_split(val, &top, &bottom, &msb);
723 top = rb_time_val_cnt(top, cnt);
724 bottom = rb_time_val_cnt(bottom, cnt);
725
726 rb_time_split(set, &top2, &bottom2, &msb2);
727 top2 = rb_time_val_cnt(top2, cnt2);
728 bottom2 = rb_time_val_cnt(bottom2, cnt2);
729
730 if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
731 return false;
732 if (!rb_time_read_cmpxchg(&t->msb, msb, msb2))
733 return false;
734 if (!rb_time_read_cmpxchg(&t->top, top, top2))
735 return false;
736 if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
737 return false;
738 return true;
739}
740
741#else /* 64 bits */
742
743/* local64_t always succeeds */
744
745static inline bool rb_time_read(rb_time_t *t, u64 *ret)
746{
747 *ret = local64_read(&t->time);
748 return true;
749}
750static void rb_time_set(rb_time_t *t, u64 val)
751{
752 local64_set(&t->time, val);
753}
754
755static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
756{
757 u64 val;
758 val = local64_cmpxchg(&t->time, expect, set);
759 return val == expect;
760}
761#endif
762
763/*
764 * Enable this to make sure that the event passed to
765 * ring_buffer_event_time_stamp() is not committed and also
766 * is on the buffer that it passed in.
767 */
768//#define RB_VERIFY_EVENT
769#ifdef RB_VERIFY_EVENT
770static struct list_head *rb_list_head(struct list_head *list);
771static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
772 void *event)
773{
774 struct buffer_page *page = cpu_buffer->commit_page;
775 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
776 struct list_head *next;
777 long commit, write;
778 unsigned long addr = (unsigned long)event;
779 bool done = false;
780 int stop = 0;
781
782 /* Make sure the event exists and is not committed yet */
783 do {
784 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
785 done = true;
786 commit = local_read(&page->page->commit);
787 write = local_read(&page->write);
788 if (addr >= (unsigned long)&page->page->data[commit] &&
789 addr < (unsigned long)&page->page->data[write])
790 return;
791
792 next = rb_list_head(page->list.next);
793 page = list_entry(next, struct buffer_page, list);
794 } while (!done);
795 WARN_ON_ONCE(1);
796}
797#else
798static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
799 void *event)
800{
801}
802#endif
803
804/*
805 * The absolute time stamp drops the 5 MSBs and some clocks may
806 * require them. The rb_fix_abs_ts() will take a previous full
807 * time stamp, and add the 5 MSB of that time stamp on to the
808 * saved absolute time stamp. Then they are compared in case of
809 * the unlikely event that the latest time stamp incremented
810 * the 5 MSB.
811 */
812static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
813{
814 if (save_ts & TS_MSB) {
815 abs |= save_ts & TS_MSB;
816 /* Check for overflow */
817 if (unlikely(abs < save_ts))
818 abs += 1ULL << 59;
819 }
820 return abs;
821}
822
823static inline u64 rb_time_stamp(struct trace_buffer *buffer);
824
825/**
826 * ring_buffer_event_time_stamp - return the event's current time stamp
827 * @buffer: The buffer that the event is on
828 * @event: the event to get the time stamp of
829 *
830 * Note, this must be called after @event is reserved, and before it is
831 * committed to the ring buffer. And must be called from the same
832 * context where the event was reserved (normal, softirq, irq, etc).
833 *
834 * Returns the time stamp associated with the current event.
835 * If the event has an extended time stamp, then that is used as
836 * the time stamp to return.
837 * In the highly unlikely case that the event was nested more than
838 * the max nesting, then the write_stamp of the buffer is returned,
839 * otherwise current time is returned, but that really neither of
840 * the last two cases should ever happen.
841 */
842u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
843 struct ring_buffer_event *event)
844{
845 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
846 unsigned int nest;
847 u64 ts;
848
849 /* If the event includes an absolute time, then just use that */
850 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
851 ts = rb_event_time_stamp(event);
852 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
853 }
854
855 nest = local_read(&cpu_buffer->committing);
856 verify_event(cpu_buffer, event);
857 if (WARN_ON_ONCE(!nest))
858 goto fail;
859
860 /* Read the current saved nesting level time stamp */
861 if (likely(--nest < MAX_NEST))
862 return cpu_buffer->event_stamp[nest];
863
864 /* Shouldn't happen, warn if it does */
865 WARN_ONCE(1, "nest (%d) greater than max", nest);
866
867 fail:
868 /* Can only fail on 32 bit */
869 if (!rb_time_read(&cpu_buffer->write_stamp, &ts))
870 /* Screw it, just read the current time */
871 ts = rb_time_stamp(cpu_buffer->buffer);
872
873 return ts;
874}
875
876/**
877 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
878 * @buffer: The ring_buffer to get the number of pages from
879 * @cpu: The cpu of the ring_buffer to get the number of pages from
880 *
881 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
882 */
883size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
884{
885 return buffer->buffers[cpu]->nr_pages;
886}
887
888/**
889 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
890 * @buffer: The ring_buffer to get the number of pages from
891 * @cpu: The cpu of the ring_buffer to get the number of pages from
892 *
893 * Returns the number of pages that have content in the ring buffer.
894 */
895size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
896{
897 size_t read;
898 size_t lost;
899 size_t cnt;
900
901 read = local_read(&buffer->buffers[cpu]->pages_read);
902 lost = local_read(&buffer->buffers[cpu]->pages_lost);
903 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
904
905 if (WARN_ON_ONCE(cnt < lost))
906 return 0;
907
908 cnt -= lost;
909
910 /* The reader can read an empty page, but not more than that */
911 if (cnt < read) {
912 WARN_ON_ONCE(read > cnt + 1);
913 return 0;
914 }
915
916 return cnt - read;
917}
918
919static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
920{
921 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
922 size_t nr_pages;
923 size_t dirty;
924
925 nr_pages = cpu_buffer->nr_pages;
926 if (!nr_pages || !full)
927 return true;
928
929 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
930
931 return (dirty * 100) > (full * nr_pages);
932}
933
934/*
935 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
936 *
937 * Schedules a delayed work to wake up any task that is blocked on the
938 * ring buffer waiters queue.
939 */
940static void rb_wake_up_waiters(struct irq_work *work)
941{
942 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
943
944 wake_up_all(&rbwork->waiters);
945 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
946 rbwork->wakeup_full = false;
947 rbwork->full_waiters_pending = false;
948 wake_up_all(&rbwork->full_waiters);
949 }
950}
951
952/**
953 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
954 * @buffer: The ring buffer to wake waiters on
955 *
956 * In the case of a file that represents a ring buffer is closing,
957 * it is prudent to wake up any waiters that are on this.
958 */
959void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
960{
961 struct ring_buffer_per_cpu *cpu_buffer;
962 struct rb_irq_work *rbwork;
963
964 if (!buffer)
965 return;
966
967 if (cpu == RING_BUFFER_ALL_CPUS) {
968
969 /* Wake up individual ones too. One level recursion */
970 for_each_buffer_cpu(buffer, cpu)
971 ring_buffer_wake_waiters(buffer, cpu);
972
973 rbwork = &buffer->irq_work;
974 } else {
975 if (WARN_ON_ONCE(!buffer->buffers))
976 return;
977 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
978 return;
979
980 cpu_buffer = buffer->buffers[cpu];
981 /* The CPU buffer may not have been initialized yet */
982 if (!cpu_buffer)
983 return;
984 rbwork = &cpu_buffer->irq_work;
985 }
986
987 rbwork->wait_index++;
988 /* make sure the waiters see the new index */
989 smp_wmb();
990
991 rb_wake_up_waiters(&rbwork->work);
992}
993
994/**
995 * ring_buffer_wait - wait for input to the ring buffer
996 * @buffer: buffer to wait on
997 * @cpu: the cpu buffer to wait on
998 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
999 *
1000 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1001 * as data is added to any of the @buffer's cpu buffers. Otherwise
1002 * it will wait for data to be added to a specific cpu buffer.
1003 */
1004int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
1005{
1006 struct ring_buffer_per_cpu *cpu_buffer;
1007 DEFINE_WAIT(wait);
1008 struct rb_irq_work *work;
1009 long wait_index;
1010 int ret = 0;
1011
1012 /*
1013 * Depending on what the caller is waiting for, either any
1014 * data in any cpu buffer, or a specific buffer, put the
1015 * caller on the appropriate wait queue.
1016 */
1017 if (cpu == RING_BUFFER_ALL_CPUS) {
1018 work = &buffer->irq_work;
1019 /* Full only makes sense on per cpu reads */
1020 full = 0;
1021 } else {
1022 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1023 return -ENODEV;
1024 cpu_buffer = buffer->buffers[cpu];
1025 work = &cpu_buffer->irq_work;
1026 }
1027
1028 wait_index = READ_ONCE(work->wait_index);
1029
1030 while (true) {
1031 if (full)
1032 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
1033 else
1034 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
1035
1036 /*
1037 * The events can happen in critical sections where
1038 * checking a work queue can cause deadlocks.
1039 * After adding a task to the queue, this flag is set
1040 * only to notify events to try to wake up the queue
1041 * using irq_work.
1042 *
1043 * We don't clear it even if the buffer is no longer
1044 * empty. The flag only causes the next event to run
1045 * irq_work to do the work queue wake up. The worse
1046 * that can happen if we race with !trace_empty() is that
1047 * an event will cause an irq_work to try to wake up
1048 * an empty queue.
1049 *
1050 * There's no reason to protect this flag either, as
1051 * the work queue and irq_work logic will do the necessary
1052 * synchronization for the wake ups. The only thing
1053 * that is necessary is that the wake up happens after
1054 * a task has been queued. It's OK for spurious wake ups.
1055 */
1056 if (full)
1057 work->full_waiters_pending = true;
1058 else
1059 work->waiters_pending = true;
1060
1061 if (signal_pending(current)) {
1062 ret = -EINTR;
1063 break;
1064 }
1065
1066 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
1067 break;
1068
1069 if (cpu != RING_BUFFER_ALL_CPUS &&
1070 !ring_buffer_empty_cpu(buffer, cpu)) {
1071 unsigned long flags;
1072 bool pagebusy;
1073 bool done;
1074
1075 if (!full)
1076 break;
1077
1078 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1079 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
1080 done = !pagebusy && full_hit(buffer, cpu, full);
1081
1082 if (!cpu_buffer->shortest_full ||
1083 cpu_buffer->shortest_full > full)
1084 cpu_buffer->shortest_full = full;
1085 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1086 if (done)
1087 break;
1088 }
1089
1090 schedule();
1091
1092 /* Make sure to see the new wait index */
1093 smp_rmb();
1094 if (wait_index != work->wait_index)
1095 break;
1096 }
1097
1098 if (full)
1099 finish_wait(&work->full_waiters, &wait);
1100 else
1101 finish_wait(&work->waiters, &wait);
1102
1103 return ret;
1104}
1105
1106/**
1107 * ring_buffer_poll_wait - poll on buffer input
1108 * @buffer: buffer to wait on
1109 * @cpu: the cpu buffer to wait on
1110 * @filp: the file descriptor
1111 * @poll_table: The poll descriptor
1112 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
1113 *
1114 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1115 * as data is added to any of the @buffer's cpu buffers. Otherwise
1116 * it will wait for data to be added to a specific cpu buffer.
1117 *
1118 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1119 * zero otherwise.
1120 */
1121__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1122 struct file *filp, poll_table *poll_table, int full)
1123{
1124 struct ring_buffer_per_cpu *cpu_buffer;
1125 struct rb_irq_work *work;
1126
1127 if (cpu == RING_BUFFER_ALL_CPUS) {
1128 work = &buffer->irq_work;
1129 full = 0;
1130 } else {
1131 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1132 return -EINVAL;
1133
1134 cpu_buffer = buffer->buffers[cpu];
1135 work = &cpu_buffer->irq_work;
1136 }
1137
1138 if (full) {
1139 poll_wait(filp, &work->full_waiters, poll_table);
1140 work->full_waiters_pending = true;
1141 } else {
1142 poll_wait(filp, &work->waiters, poll_table);
1143 work->waiters_pending = true;
1144 }
1145
1146 /*
1147 * There's a tight race between setting the waiters_pending and
1148 * checking if the ring buffer is empty. Once the waiters_pending bit
1149 * is set, the next event will wake the task up, but we can get stuck
1150 * if there's only a single event in.
1151 *
1152 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1153 * but adding a memory barrier to all events will cause too much of a
1154 * performance hit in the fast path. We only need a memory barrier when
1155 * the buffer goes from empty to having content. But as this race is
1156 * extremely small, and it's not a problem if another event comes in, we
1157 * will fix it later.
1158 */
1159 smp_mb();
1160
1161 if (full)
1162 return full_hit(buffer, cpu, full) ? EPOLLIN | EPOLLRDNORM : 0;
1163
1164 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1165 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1166 return EPOLLIN | EPOLLRDNORM;
1167 return 0;
1168}
1169
1170/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1171#define RB_WARN_ON(b, cond) \
1172 ({ \
1173 int _____ret = unlikely(cond); \
1174 if (_____ret) { \
1175 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1176 struct ring_buffer_per_cpu *__b = \
1177 (void *)b; \
1178 atomic_inc(&__b->buffer->record_disabled); \
1179 } else \
1180 atomic_inc(&b->record_disabled); \
1181 WARN_ON(1); \
1182 } \
1183 _____ret; \
1184 })
1185
1186/* Up this if you want to test the TIME_EXTENTS and normalization */
1187#define DEBUG_SHIFT 0
1188
1189static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1190{
1191 u64 ts;
1192
1193 /* Skip retpolines :-( */
1194 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1195 ts = trace_clock_local();
1196 else
1197 ts = buffer->clock();
1198
1199 /* shift to debug/test normalization and TIME_EXTENTS */
1200 return ts << DEBUG_SHIFT;
1201}
1202
1203u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1204{
1205 u64 time;
1206
1207 preempt_disable_notrace();
1208 time = rb_time_stamp(buffer);
1209 preempt_enable_notrace();
1210
1211 return time;
1212}
1213EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1214
1215void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1216 int cpu, u64 *ts)
1217{
1218 /* Just stupid testing the normalize function and deltas */
1219 *ts >>= DEBUG_SHIFT;
1220}
1221EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1222
1223/*
1224 * Making the ring buffer lockless makes things tricky.
1225 * Although writes only happen on the CPU that they are on,
1226 * and they only need to worry about interrupts. Reads can
1227 * happen on any CPU.
1228 *
1229 * The reader page is always off the ring buffer, but when the
1230 * reader finishes with a page, it needs to swap its page with
1231 * a new one from the buffer. The reader needs to take from
1232 * the head (writes go to the tail). But if a writer is in overwrite
1233 * mode and wraps, it must push the head page forward.
1234 *
1235 * Here lies the problem.
1236 *
1237 * The reader must be careful to replace only the head page, and
1238 * not another one. As described at the top of the file in the
1239 * ASCII art, the reader sets its old page to point to the next
1240 * page after head. It then sets the page after head to point to
1241 * the old reader page. But if the writer moves the head page
1242 * during this operation, the reader could end up with the tail.
1243 *
1244 * We use cmpxchg to help prevent this race. We also do something
1245 * special with the page before head. We set the LSB to 1.
1246 *
1247 * When the writer must push the page forward, it will clear the
1248 * bit that points to the head page, move the head, and then set
1249 * the bit that points to the new head page.
1250 *
1251 * We also don't want an interrupt coming in and moving the head
1252 * page on another writer. Thus we use the second LSB to catch
1253 * that too. Thus:
1254 *
1255 * head->list->prev->next bit 1 bit 0
1256 * ------- -------
1257 * Normal page 0 0
1258 * Points to head page 0 1
1259 * New head page 1 0
1260 *
1261 * Note we can not trust the prev pointer of the head page, because:
1262 *
1263 * +----+ +-----+ +-----+
1264 * | |------>| T |---X--->| N |
1265 * | |<------| | | |
1266 * +----+ +-----+ +-----+
1267 * ^ ^ |
1268 * | +-----+ | |
1269 * +----------| R |----------+ |
1270 * | |<-----------+
1271 * +-----+
1272 *
1273 * Key: ---X--> HEAD flag set in pointer
1274 * T Tail page
1275 * R Reader page
1276 * N Next page
1277 *
1278 * (see __rb_reserve_next() to see where this happens)
1279 *
1280 * What the above shows is that the reader just swapped out
1281 * the reader page with a page in the buffer, but before it
1282 * could make the new header point back to the new page added
1283 * it was preempted by a writer. The writer moved forward onto
1284 * the new page added by the reader and is about to move forward
1285 * again.
1286 *
1287 * You can see, it is legitimate for the previous pointer of
1288 * the head (or any page) not to point back to itself. But only
1289 * temporarily.
1290 */
1291
1292#define RB_PAGE_NORMAL 0UL
1293#define RB_PAGE_HEAD 1UL
1294#define RB_PAGE_UPDATE 2UL
1295
1296
1297#define RB_FLAG_MASK 3UL
1298
1299/* PAGE_MOVED is not part of the mask */
1300#define RB_PAGE_MOVED 4UL
1301
1302/*
1303 * rb_list_head - remove any bit
1304 */
1305static struct list_head *rb_list_head(struct list_head *list)
1306{
1307 unsigned long val = (unsigned long)list;
1308
1309 return (struct list_head *)(val & ~RB_FLAG_MASK);
1310}
1311
1312/*
1313 * rb_is_head_page - test if the given page is the head page
1314 *
1315 * Because the reader may move the head_page pointer, we can
1316 * not trust what the head page is (it may be pointing to
1317 * the reader page). But if the next page is a header page,
1318 * its flags will be non zero.
1319 */
1320static inline int
1321rb_is_head_page(struct buffer_page *page, struct list_head *list)
1322{
1323 unsigned long val;
1324
1325 val = (unsigned long)list->next;
1326
1327 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1328 return RB_PAGE_MOVED;
1329
1330 return val & RB_FLAG_MASK;
1331}
1332
1333/*
1334 * rb_is_reader_page
1335 *
1336 * The unique thing about the reader page, is that, if the
1337 * writer is ever on it, the previous pointer never points
1338 * back to the reader page.
1339 */
1340static bool rb_is_reader_page(struct buffer_page *page)
1341{
1342 struct list_head *list = page->list.prev;
1343
1344 return rb_list_head(list->next) != &page->list;
1345}
1346
1347/*
1348 * rb_set_list_to_head - set a list_head to be pointing to head.
1349 */
1350static void rb_set_list_to_head(struct list_head *list)
1351{
1352 unsigned long *ptr;
1353
1354 ptr = (unsigned long *)&list->next;
1355 *ptr |= RB_PAGE_HEAD;
1356 *ptr &= ~RB_PAGE_UPDATE;
1357}
1358
1359/*
1360 * rb_head_page_activate - sets up head page
1361 */
1362static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1363{
1364 struct buffer_page *head;
1365
1366 head = cpu_buffer->head_page;
1367 if (!head)
1368 return;
1369
1370 /*
1371 * Set the previous list pointer to have the HEAD flag.
1372 */
1373 rb_set_list_to_head(head->list.prev);
1374}
1375
1376static void rb_list_head_clear(struct list_head *list)
1377{
1378 unsigned long *ptr = (unsigned long *)&list->next;
1379
1380 *ptr &= ~RB_FLAG_MASK;
1381}
1382
1383/*
1384 * rb_head_page_deactivate - clears head page ptr (for free list)
1385 */
1386static void
1387rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1388{
1389 struct list_head *hd;
1390
1391 /* Go through the whole list and clear any pointers found. */
1392 rb_list_head_clear(cpu_buffer->pages);
1393
1394 list_for_each(hd, cpu_buffer->pages)
1395 rb_list_head_clear(hd);
1396}
1397
1398static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1399 struct buffer_page *head,
1400 struct buffer_page *prev,
1401 int old_flag, int new_flag)
1402{
1403 struct list_head *list;
1404 unsigned long val = (unsigned long)&head->list;
1405 unsigned long ret;
1406
1407 list = &prev->list;
1408
1409 val &= ~RB_FLAG_MASK;
1410
1411 ret = cmpxchg((unsigned long *)&list->next,
1412 val | old_flag, val | new_flag);
1413
1414 /* check if the reader took the page */
1415 if ((ret & ~RB_FLAG_MASK) != val)
1416 return RB_PAGE_MOVED;
1417
1418 return ret & RB_FLAG_MASK;
1419}
1420
1421static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1422 struct buffer_page *head,
1423 struct buffer_page *prev,
1424 int old_flag)
1425{
1426 return rb_head_page_set(cpu_buffer, head, prev,
1427 old_flag, RB_PAGE_UPDATE);
1428}
1429
1430static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1431 struct buffer_page *head,
1432 struct buffer_page *prev,
1433 int old_flag)
1434{
1435 return rb_head_page_set(cpu_buffer, head, prev,
1436 old_flag, RB_PAGE_HEAD);
1437}
1438
1439static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1440 struct buffer_page *head,
1441 struct buffer_page *prev,
1442 int old_flag)
1443{
1444 return rb_head_page_set(cpu_buffer, head, prev,
1445 old_flag, RB_PAGE_NORMAL);
1446}
1447
1448static inline void rb_inc_page(struct buffer_page **bpage)
1449{
1450 struct list_head *p = rb_list_head((*bpage)->list.next);
1451
1452 *bpage = list_entry(p, struct buffer_page, list);
1453}
1454
1455static struct buffer_page *
1456rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1457{
1458 struct buffer_page *head;
1459 struct buffer_page *page;
1460 struct list_head *list;
1461 int i;
1462
1463 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1464 return NULL;
1465
1466 /* sanity check */
1467 list = cpu_buffer->pages;
1468 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1469 return NULL;
1470
1471 page = head = cpu_buffer->head_page;
1472 /*
1473 * It is possible that the writer moves the header behind
1474 * where we started, and we miss in one loop.
1475 * A second loop should grab the header, but we'll do
1476 * three loops just because I'm paranoid.
1477 */
1478 for (i = 0; i < 3; i++) {
1479 do {
1480 if (rb_is_head_page(page, page->list.prev)) {
1481 cpu_buffer->head_page = page;
1482 return page;
1483 }
1484 rb_inc_page(&page);
1485 } while (page != head);
1486 }
1487
1488 RB_WARN_ON(cpu_buffer, 1);
1489
1490 return NULL;
1491}
1492
1493static int rb_head_page_replace(struct buffer_page *old,
1494 struct buffer_page *new)
1495{
1496 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1497 unsigned long val;
1498 unsigned long ret;
1499
1500 val = *ptr & ~RB_FLAG_MASK;
1501 val |= RB_PAGE_HEAD;
1502
1503 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1504
1505 return ret == val;
1506}
1507
1508/*
1509 * rb_tail_page_update - move the tail page forward
1510 */
1511static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1512 struct buffer_page *tail_page,
1513 struct buffer_page *next_page)
1514{
1515 unsigned long old_entries;
1516 unsigned long old_write;
1517
1518 /*
1519 * The tail page now needs to be moved forward.
1520 *
1521 * We need to reset the tail page, but without messing
1522 * with possible erasing of data brought in by interrupts
1523 * that have moved the tail page and are currently on it.
1524 *
1525 * We add a counter to the write field to denote this.
1526 */
1527 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1528 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1529
1530 local_inc(&cpu_buffer->pages_touched);
1531 /*
1532 * Just make sure we have seen our old_write and synchronize
1533 * with any interrupts that come in.
1534 */
1535 barrier();
1536
1537 /*
1538 * If the tail page is still the same as what we think
1539 * it is, then it is up to us to update the tail
1540 * pointer.
1541 */
1542 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1543 /* Zero the write counter */
1544 unsigned long val = old_write & ~RB_WRITE_MASK;
1545 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1546
1547 /*
1548 * This will only succeed if an interrupt did
1549 * not come in and change it. In which case, we
1550 * do not want to modify it.
1551 *
1552 * We add (void) to let the compiler know that we do not care
1553 * about the return value of these functions. We use the
1554 * cmpxchg to only update if an interrupt did not already
1555 * do it for us. If the cmpxchg fails, we don't care.
1556 */
1557 (void)local_cmpxchg(&next_page->write, old_write, val);
1558 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1559
1560 /*
1561 * No need to worry about races with clearing out the commit.
1562 * it only can increment when a commit takes place. But that
1563 * only happens in the outer most nested commit.
1564 */
1565 local_set(&next_page->page->commit, 0);
1566
1567 /* Again, either we update tail_page or an interrupt does */
1568 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1569 }
1570}
1571
1572static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1573 struct buffer_page *bpage)
1574{
1575 unsigned long val = (unsigned long)bpage;
1576
1577 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1578 return 1;
1579
1580 return 0;
1581}
1582
1583/**
1584 * rb_check_list - make sure a pointer to a list has the last bits zero
1585 */
1586static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1587 struct list_head *list)
1588{
1589 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1590 return 1;
1591 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1592 return 1;
1593 return 0;
1594}
1595
1596/**
1597 * rb_check_pages - integrity check of buffer pages
1598 * @cpu_buffer: CPU buffer with pages to test
1599 *
1600 * As a safety measure we check to make sure the data pages have not
1601 * been corrupted.
1602 */
1603static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1604{
1605 struct list_head *head = cpu_buffer->pages;
1606 struct buffer_page *bpage, *tmp;
1607
1608 /* Reset the head page if it exists */
1609 if (cpu_buffer->head_page)
1610 rb_set_head_page(cpu_buffer);
1611
1612 rb_head_page_deactivate(cpu_buffer);
1613
1614 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1615 return -1;
1616 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1617 return -1;
1618
1619 if (rb_check_list(cpu_buffer, head))
1620 return -1;
1621
1622 list_for_each_entry_safe(bpage, tmp, head, list) {
1623 if (RB_WARN_ON(cpu_buffer,
1624 bpage->list.next->prev != &bpage->list))
1625 return -1;
1626 if (RB_WARN_ON(cpu_buffer,
1627 bpage->list.prev->next != &bpage->list))
1628 return -1;
1629 if (rb_check_list(cpu_buffer, &bpage->list))
1630 return -1;
1631 }
1632
1633 rb_head_page_activate(cpu_buffer);
1634
1635 return 0;
1636}
1637
1638static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1639 long nr_pages, struct list_head *pages)
1640{
1641 struct buffer_page *bpage, *tmp;
1642 bool user_thread = current->mm != NULL;
1643 gfp_t mflags;
1644 long i;
1645
1646 /*
1647 * Check if the available memory is there first.
1648 * Note, si_mem_available() only gives us a rough estimate of available
1649 * memory. It may not be accurate. But we don't care, we just want
1650 * to prevent doing any allocation when it is obvious that it is
1651 * not going to succeed.
1652 */
1653 i = si_mem_available();
1654 if (i < nr_pages)
1655 return -ENOMEM;
1656
1657 /*
1658 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1659 * gracefully without invoking oom-killer and the system is not
1660 * destabilized.
1661 */
1662 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1663
1664 /*
1665 * If a user thread allocates too much, and si_mem_available()
1666 * reports there's enough memory, even though there is not.
1667 * Make sure the OOM killer kills this thread. This can happen
1668 * even with RETRY_MAYFAIL because another task may be doing
1669 * an allocation after this task has taken all memory.
1670 * This is the task the OOM killer needs to take out during this
1671 * loop, even if it was triggered by an allocation somewhere else.
1672 */
1673 if (user_thread)
1674 set_current_oom_origin();
1675 for (i = 0; i < nr_pages; i++) {
1676 struct page *page;
1677
1678 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1679 mflags, cpu_to_node(cpu_buffer->cpu));
1680 if (!bpage)
1681 goto free_pages;
1682
1683 rb_check_bpage(cpu_buffer, bpage);
1684
1685 list_add(&bpage->list, pages);
1686
1687 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
1688 if (!page)
1689 goto free_pages;
1690 bpage->page = page_address(page);
1691 rb_init_page(bpage->page);
1692
1693 if (user_thread && fatal_signal_pending(current))
1694 goto free_pages;
1695 }
1696 if (user_thread)
1697 clear_current_oom_origin();
1698
1699 return 0;
1700
1701free_pages:
1702 list_for_each_entry_safe(bpage, tmp, pages, list) {
1703 list_del_init(&bpage->list);
1704 free_buffer_page(bpage);
1705 }
1706 if (user_thread)
1707 clear_current_oom_origin();
1708
1709 return -ENOMEM;
1710}
1711
1712static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1713 unsigned long nr_pages)
1714{
1715 LIST_HEAD(pages);
1716
1717 WARN_ON(!nr_pages);
1718
1719 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1720 return -ENOMEM;
1721
1722 /*
1723 * The ring buffer page list is a circular list that does not
1724 * start and end with a list head. All page list items point to
1725 * other pages.
1726 */
1727 cpu_buffer->pages = pages.next;
1728 list_del(&pages);
1729
1730 cpu_buffer->nr_pages = nr_pages;
1731
1732 rb_check_pages(cpu_buffer);
1733
1734 return 0;
1735}
1736
1737static struct ring_buffer_per_cpu *
1738rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1739{
1740 struct ring_buffer_per_cpu *cpu_buffer;
1741 struct buffer_page *bpage;
1742 struct page *page;
1743 int ret;
1744
1745 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1746 GFP_KERNEL, cpu_to_node(cpu));
1747 if (!cpu_buffer)
1748 return NULL;
1749
1750 cpu_buffer->cpu = cpu;
1751 cpu_buffer->buffer = buffer;
1752 raw_spin_lock_init(&cpu_buffer->reader_lock);
1753 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1754 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1755 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1756 init_completion(&cpu_buffer->update_done);
1757 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1758 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1759 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1760
1761 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1762 GFP_KERNEL, cpu_to_node(cpu));
1763 if (!bpage)
1764 goto fail_free_buffer;
1765
1766 rb_check_bpage(cpu_buffer, bpage);
1767
1768 cpu_buffer->reader_page = bpage;
1769 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1770 if (!page)
1771 goto fail_free_reader;
1772 bpage->page = page_address(page);
1773 rb_init_page(bpage->page);
1774
1775 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1776 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1777
1778 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1779 if (ret < 0)
1780 goto fail_free_reader;
1781
1782 cpu_buffer->head_page
1783 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1784 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1785
1786 rb_head_page_activate(cpu_buffer);
1787
1788 return cpu_buffer;
1789
1790 fail_free_reader:
1791 free_buffer_page(cpu_buffer->reader_page);
1792
1793 fail_free_buffer:
1794 kfree(cpu_buffer);
1795 return NULL;
1796}
1797
1798static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1799{
1800 struct list_head *head = cpu_buffer->pages;
1801 struct buffer_page *bpage, *tmp;
1802
1803 free_buffer_page(cpu_buffer->reader_page);
1804
1805 if (head) {
1806 rb_head_page_deactivate(cpu_buffer);
1807
1808 list_for_each_entry_safe(bpage, tmp, head, list) {
1809 list_del_init(&bpage->list);
1810 free_buffer_page(bpage);
1811 }
1812 bpage = list_entry(head, struct buffer_page, list);
1813 free_buffer_page(bpage);
1814 }
1815
1816 kfree(cpu_buffer);
1817}
1818
1819/**
1820 * __ring_buffer_alloc - allocate a new ring_buffer
1821 * @size: the size in bytes per cpu that is needed.
1822 * @flags: attributes to set for the ring buffer.
1823 * @key: ring buffer reader_lock_key.
1824 *
1825 * Currently the only flag that is available is the RB_FL_OVERWRITE
1826 * flag. This flag means that the buffer will overwrite old data
1827 * when the buffer wraps. If this flag is not set, the buffer will
1828 * drop data when the tail hits the head.
1829 */
1830struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1831 struct lock_class_key *key)
1832{
1833 struct trace_buffer *buffer;
1834 long nr_pages;
1835 int bsize;
1836 int cpu;
1837 int ret;
1838
1839 /* keep it in its own cache line */
1840 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1841 GFP_KERNEL);
1842 if (!buffer)
1843 return NULL;
1844
1845 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1846 goto fail_free_buffer;
1847
1848 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1849 buffer->flags = flags;
1850 buffer->clock = trace_clock_local;
1851 buffer->reader_lock_key = key;
1852
1853 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1854 init_waitqueue_head(&buffer->irq_work.waiters);
1855
1856 /* need at least two pages */
1857 if (nr_pages < 2)
1858 nr_pages = 2;
1859
1860 buffer->cpus = nr_cpu_ids;
1861
1862 bsize = sizeof(void *) * nr_cpu_ids;
1863 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1864 GFP_KERNEL);
1865 if (!buffer->buffers)
1866 goto fail_free_cpumask;
1867
1868 cpu = raw_smp_processor_id();
1869 cpumask_set_cpu(cpu, buffer->cpumask);
1870 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1871 if (!buffer->buffers[cpu])
1872 goto fail_free_buffers;
1873
1874 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1875 if (ret < 0)
1876 goto fail_free_buffers;
1877
1878 mutex_init(&buffer->mutex);
1879
1880 return buffer;
1881
1882 fail_free_buffers:
1883 for_each_buffer_cpu(buffer, cpu) {
1884 if (buffer->buffers[cpu])
1885 rb_free_cpu_buffer(buffer->buffers[cpu]);
1886 }
1887 kfree(buffer->buffers);
1888
1889 fail_free_cpumask:
1890 free_cpumask_var(buffer->cpumask);
1891
1892 fail_free_buffer:
1893 kfree(buffer);
1894 return NULL;
1895}
1896EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1897
1898/**
1899 * ring_buffer_free - free a ring buffer.
1900 * @buffer: the buffer to free.
1901 */
1902void
1903ring_buffer_free(struct trace_buffer *buffer)
1904{
1905 int cpu;
1906
1907 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1908
1909 for_each_buffer_cpu(buffer, cpu)
1910 rb_free_cpu_buffer(buffer->buffers[cpu]);
1911
1912 kfree(buffer->buffers);
1913 free_cpumask_var(buffer->cpumask);
1914
1915 kfree(buffer);
1916}
1917EXPORT_SYMBOL_GPL(ring_buffer_free);
1918
1919void ring_buffer_set_clock(struct trace_buffer *buffer,
1920 u64 (*clock)(void))
1921{
1922 buffer->clock = clock;
1923}
1924
1925void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1926{
1927 buffer->time_stamp_abs = abs;
1928}
1929
1930bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1931{
1932 return buffer->time_stamp_abs;
1933}
1934
1935static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1936
1937static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1938{
1939 return local_read(&bpage->entries) & RB_WRITE_MASK;
1940}
1941
1942static inline unsigned long rb_page_write(struct buffer_page *bpage)
1943{
1944 return local_read(&bpage->write) & RB_WRITE_MASK;
1945}
1946
1947static int
1948rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1949{
1950 struct list_head *tail_page, *to_remove, *next_page;
1951 struct buffer_page *to_remove_page, *tmp_iter_page;
1952 struct buffer_page *last_page, *first_page;
1953 unsigned long nr_removed;
1954 unsigned long head_bit;
1955 int page_entries;
1956
1957 head_bit = 0;
1958
1959 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1960 atomic_inc(&cpu_buffer->record_disabled);
1961 /*
1962 * We don't race with the readers since we have acquired the reader
1963 * lock. We also don't race with writers after disabling recording.
1964 * This makes it easy to figure out the first and the last page to be
1965 * removed from the list. We unlink all the pages in between including
1966 * the first and last pages. This is done in a busy loop so that we
1967 * lose the least number of traces.
1968 * The pages are freed after we restart recording and unlock readers.
1969 */
1970 tail_page = &cpu_buffer->tail_page->list;
1971
1972 /*
1973 * tail page might be on reader page, we remove the next page
1974 * from the ring buffer
1975 */
1976 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1977 tail_page = rb_list_head(tail_page->next);
1978 to_remove = tail_page;
1979
1980 /* start of pages to remove */
1981 first_page = list_entry(rb_list_head(to_remove->next),
1982 struct buffer_page, list);
1983
1984 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1985 to_remove = rb_list_head(to_remove)->next;
1986 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1987 }
1988
1989 next_page = rb_list_head(to_remove)->next;
1990
1991 /*
1992 * Now we remove all pages between tail_page and next_page.
1993 * Make sure that we have head_bit value preserved for the
1994 * next page
1995 */
1996 tail_page->next = (struct list_head *)((unsigned long)next_page |
1997 head_bit);
1998 next_page = rb_list_head(next_page);
1999 next_page->prev = tail_page;
2000
2001 /* make sure pages points to a valid page in the ring buffer */
2002 cpu_buffer->pages = next_page;
2003
2004 /* update head page */
2005 if (head_bit)
2006 cpu_buffer->head_page = list_entry(next_page,
2007 struct buffer_page, list);
2008
2009 /*
2010 * change read pointer to make sure any read iterators reset
2011 * themselves
2012 */
2013 cpu_buffer->read = 0;
2014
2015 /* pages are removed, resume tracing and then free the pages */
2016 atomic_dec(&cpu_buffer->record_disabled);
2017 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2018
2019 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
2020
2021 /* last buffer page to remove */
2022 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
2023 list);
2024 tmp_iter_page = first_page;
2025
2026 do {
2027 cond_resched();
2028
2029 to_remove_page = tmp_iter_page;
2030 rb_inc_page(&tmp_iter_page);
2031
2032 /* update the counters */
2033 page_entries = rb_page_entries(to_remove_page);
2034 if (page_entries) {
2035 /*
2036 * If something was added to this page, it was full
2037 * since it is not the tail page. So we deduct the
2038 * bytes consumed in ring buffer from here.
2039 * Increment overrun to account for the lost events.
2040 */
2041 local_add(page_entries, &cpu_buffer->overrun);
2042 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2043 local_inc(&cpu_buffer->pages_lost);
2044 }
2045
2046 /*
2047 * We have already removed references to this list item, just
2048 * free up the buffer_page and its page
2049 */
2050 free_buffer_page(to_remove_page);
2051 nr_removed--;
2052
2053 } while (to_remove_page != last_page);
2054
2055 RB_WARN_ON(cpu_buffer, nr_removed);
2056
2057 return nr_removed == 0;
2058}
2059
2060static int
2061rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
2062{
2063 struct list_head *pages = &cpu_buffer->new_pages;
2064 int retries, success;
2065 unsigned long flags;
2066
2067 /* Can be called at early boot up, where interrupts must not been enabled */
2068 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2069 /*
2070 * We are holding the reader lock, so the reader page won't be swapped
2071 * in the ring buffer. Now we are racing with the writer trying to
2072 * move head page and the tail page.
2073 * We are going to adapt the reader page update process where:
2074 * 1. We first splice the start and end of list of new pages between
2075 * the head page and its previous page.
2076 * 2. We cmpxchg the prev_page->next to point from head page to the
2077 * start of new pages list.
2078 * 3. Finally, we update the head->prev to the end of new list.
2079 *
2080 * We will try this process 10 times, to make sure that we don't keep
2081 * spinning.
2082 */
2083 retries = 10;
2084 success = 0;
2085 while (retries--) {
2086 struct list_head *head_page, *prev_page, *r;
2087 struct list_head *last_page, *first_page;
2088 struct list_head *head_page_with_bit;
2089
2090 head_page = &rb_set_head_page(cpu_buffer)->list;
2091 if (!head_page)
2092 break;
2093 prev_page = head_page->prev;
2094
2095 first_page = pages->next;
2096 last_page = pages->prev;
2097
2098 head_page_with_bit = (struct list_head *)
2099 ((unsigned long)head_page | RB_PAGE_HEAD);
2100
2101 last_page->next = head_page_with_bit;
2102 first_page->prev = prev_page;
2103
2104 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
2105
2106 if (r == head_page_with_bit) {
2107 /*
2108 * yay, we replaced the page pointer to our new list,
2109 * now, we just have to update to head page's prev
2110 * pointer to point to end of list
2111 */
2112 head_page->prev = last_page;
2113 success = 1;
2114 break;
2115 }
2116 }
2117
2118 if (success)
2119 INIT_LIST_HEAD(pages);
2120 /*
2121 * If we weren't successful in adding in new pages, warn and stop
2122 * tracing
2123 */
2124 RB_WARN_ON(cpu_buffer, !success);
2125 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2126
2127 /* free pages if they weren't inserted */
2128 if (!success) {
2129 struct buffer_page *bpage, *tmp;
2130 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2131 list) {
2132 list_del_init(&bpage->list);
2133 free_buffer_page(bpage);
2134 }
2135 }
2136 return success;
2137}
2138
2139static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2140{
2141 int success;
2142
2143 if (cpu_buffer->nr_pages_to_update > 0)
2144 success = rb_insert_pages(cpu_buffer);
2145 else
2146 success = rb_remove_pages(cpu_buffer,
2147 -cpu_buffer->nr_pages_to_update);
2148
2149 if (success)
2150 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2151}
2152
2153static void update_pages_handler(struct work_struct *work)
2154{
2155 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2156 struct ring_buffer_per_cpu, update_pages_work);
2157 rb_update_pages(cpu_buffer);
2158 complete(&cpu_buffer->update_done);
2159}
2160
2161/**
2162 * ring_buffer_resize - resize the ring buffer
2163 * @buffer: the buffer to resize.
2164 * @size: the new size.
2165 * @cpu_id: the cpu buffer to resize
2166 *
2167 * Minimum size is 2 * BUF_PAGE_SIZE.
2168 *
2169 * Returns 0 on success and < 0 on failure.
2170 */
2171int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2172 int cpu_id)
2173{
2174 struct ring_buffer_per_cpu *cpu_buffer;
2175 unsigned long nr_pages;
2176 int cpu, err;
2177
2178 /*
2179 * Always succeed at resizing a non-existent buffer:
2180 */
2181 if (!buffer)
2182 return 0;
2183
2184 /* Make sure the requested buffer exists */
2185 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2186 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2187 return 0;
2188
2189 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
2190
2191 /* we need a minimum of two pages */
2192 if (nr_pages < 2)
2193 nr_pages = 2;
2194
2195 /* prevent another thread from changing buffer sizes */
2196 mutex_lock(&buffer->mutex);
2197
2198
2199 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2200 /*
2201 * Don't succeed if resizing is disabled, as a reader might be
2202 * manipulating the ring buffer and is expecting a sane state while
2203 * this is true.
2204 */
2205 for_each_buffer_cpu(buffer, cpu) {
2206 cpu_buffer = buffer->buffers[cpu];
2207 if (atomic_read(&cpu_buffer->resize_disabled)) {
2208 err = -EBUSY;
2209 goto out_err_unlock;
2210 }
2211 }
2212
2213 /* calculate the pages to update */
2214 for_each_buffer_cpu(buffer, cpu) {
2215 cpu_buffer = buffer->buffers[cpu];
2216
2217 cpu_buffer->nr_pages_to_update = nr_pages -
2218 cpu_buffer->nr_pages;
2219 /*
2220 * nothing more to do for removing pages or no update
2221 */
2222 if (cpu_buffer->nr_pages_to_update <= 0)
2223 continue;
2224 /*
2225 * to add pages, make sure all new pages can be
2226 * allocated without receiving ENOMEM
2227 */
2228 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2229 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2230 &cpu_buffer->new_pages)) {
2231 /* not enough memory for new pages */
2232 err = -ENOMEM;
2233 goto out_err;
2234 }
2235 }
2236
2237 cpus_read_lock();
2238 /*
2239 * Fire off all the required work handlers
2240 * We can't schedule on offline CPUs, but it's not necessary
2241 * since we can change their buffer sizes without any race.
2242 */
2243 for_each_buffer_cpu(buffer, cpu) {
2244 cpu_buffer = buffer->buffers[cpu];
2245 if (!cpu_buffer->nr_pages_to_update)
2246 continue;
2247
2248 /* Can't run something on an offline CPU. */
2249 if (!cpu_online(cpu)) {
2250 rb_update_pages(cpu_buffer);
2251 cpu_buffer->nr_pages_to_update = 0;
2252 } else {
2253 /* Run directly if possible. */
2254 migrate_disable();
2255 if (cpu != smp_processor_id()) {
2256 migrate_enable();
2257 schedule_work_on(cpu,
2258 &cpu_buffer->update_pages_work);
2259 } else {
2260 update_pages_handler(&cpu_buffer->update_pages_work);
2261 migrate_enable();
2262 }
2263 }
2264 }
2265
2266 /* wait for all the updates to complete */
2267 for_each_buffer_cpu(buffer, cpu) {
2268 cpu_buffer = buffer->buffers[cpu];
2269 if (!cpu_buffer->nr_pages_to_update)
2270 continue;
2271
2272 if (cpu_online(cpu))
2273 wait_for_completion(&cpu_buffer->update_done);
2274 cpu_buffer->nr_pages_to_update = 0;
2275 }
2276
2277 cpus_read_unlock();
2278 } else {
2279 cpu_buffer = buffer->buffers[cpu_id];
2280
2281 if (nr_pages == cpu_buffer->nr_pages)
2282 goto out;
2283
2284 /*
2285 * Don't succeed if resizing is disabled, as a reader might be
2286 * manipulating the ring buffer and is expecting a sane state while
2287 * this is true.
2288 */
2289 if (atomic_read(&cpu_buffer->resize_disabled)) {
2290 err = -EBUSY;
2291 goto out_err_unlock;
2292 }
2293
2294 cpu_buffer->nr_pages_to_update = nr_pages -
2295 cpu_buffer->nr_pages;
2296
2297 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2298 if (cpu_buffer->nr_pages_to_update > 0 &&
2299 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2300 &cpu_buffer->new_pages)) {
2301 err = -ENOMEM;
2302 goto out_err;
2303 }
2304
2305 cpus_read_lock();
2306
2307 /* Can't run something on an offline CPU. */
2308 if (!cpu_online(cpu_id))
2309 rb_update_pages(cpu_buffer);
2310 else {
2311 /* Run directly if possible. */
2312 migrate_disable();
2313 if (cpu_id == smp_processor_id()) {
2314 rb_update_pages(cpu_buffer);
2315 migrate_enable();
2316 } else {
2317 migrate_enable();
2318 schedule_work_on(cpu_id,
2319 &cpu_buffer->update_pages_work);
2320 wait_for_completion(&cpu_buffer->update_done);
2321 }
2322 }
2323
2324 cpu_buffer->nr_pages_to_update = 0;
2325 cpus_read_unlock();
2326 }
2327
2328 out:
2329 /*
2330 * The ring buffer resize can happen with the ring buffer
2331 * enabled, so that the update disturbs the tracing as little
2332 * as possible. But if the buffer is disabled, we do not need
2333 * to worry about that, and we can take the time to verify
2334 * that the buffer is not corrupt.
2335 */
2336 if (atomic_read(&buffer->record_disabled)) {
2337 atomic_inc(&buffer->record_disabled);
2338 /*
2339 * Even though the buffer was disabled, we must make sure
2340 * that it is truly disabled before calling rb_check_pages.
2341 * There could have been a race between checking
2342 * record_disable and incrementing it.
2343 */
2344 synchronize_rcu();
2345 for_each_buffer_cpu(buffer, cpu) {
2346 cpu_buffer = buffer->buffers[cpu];
2347 rb_check_pages(cpu_buffer);
2348 }
2349 atomic_dec(&buffer->record_disabled);
2350 }
2351
2352 mutex_unlock(&buffer->mutex);
2353 return 0;
2354
2355 out_err:
2356 for_each_buffer_cpu(buffer, cpu) {
2357 struct buffer_page *bpage, *tmp;
2358
2359 cpu_buffer = buffer->buffers[cpu];
2360 cpu_buffer->nr_pages_to_update = 0;
2361
2362 if (list_empty(&cpu_buffer->new_pages))
2363 continue;
2364
2365 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2366 list) {
2367 list_del_init(&bpage->list);
2368 free_buffer_page(bpage);
2369 }
2370 }
2371 out_err_unlock:
2372 mutex_unlock(&buffer->mutex);
2373 return err;
2374}
2375EXPORT_SYMBOL_GPL(ring_buffer_resize);
2376
2377void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2378{
2379 mutex_lock(&buffer->mutex);
2380 if (val)
2381 buffer->flags |= RB_FL_OVERWRITE;
2382 else
2383 buffer->flags &= ~RB_FL_OVERWRITE;
2384 mutex_unlock(&buffer->mutex);
2385}
2386EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2387
2388static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2389{
2390 return bpage->page->data + index;
2391}
2392
2393static __always_inline struct ring_buffer_event *
2394rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2395{
2396 return __rb_page_index(cpu_buffer->reader_page,
2397 cpu_buffer->reader_page->read);
2398}
2399
2400static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2401{
2402 return local_read(&bpage->page->commit);
2403}
2404
2405static struct ring_buffer_event *
2406rb_iter_head_event(struct ring_buffer_iter *iter)
2407{
2408 struct ring_buffer_event *event;
2409 struct buffer_page *iter_head_page = iter->head_page;
2410 unsigned long commit;
2411 unsigned length;
2412
2413 if (iter->head != iter->next_event)
2414 return iter->event;
2415
2416 /*
2417 * When the writer goes across pages, it issues a cmpxchg which
2418 * is a mb(), which will synchronize with the rmb here.
2419 * (see rb_tail_page_update() and __rb_reserve_next())
2420 */
2421 commit = rb_page_commit(iter_head_page);
2422 smp_rmb();
2423 event = __rb_page_index(iter_head_page, iter->head);
2424 length = rb_event_length(event);
2425
2426 /*
2427 * READ_ONCE() doesn't work on functions and we don't want the
2428 * compiler doing any crazy optimizations with length.
2429 */
2430 barrier();
2431
2432 if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2433 /* Writer corrupted the read? */
2434 goto reset;
2435
2436 memcpy(iter->event, event, length);
2437 /*
2438 * If the page stamp is still the same after this rmb() then the
2439 * event was safely copied without the writer entering the page.
2440 */
2441 smp_rmb();
2442
2443 /* Make sure the page didn't change since we read this */
2444 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2445 commit > rb_page_commit(iter_head_page))
2446 goto reset;
2447
2448 iter->next_event = iter->head + length;
2449 return iter->event;
2450 reset:
2451 /* Reset to the beginning */
2452 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2453 iter->head = 0;
2454 iter->next_event = 0;
2455 iter->missed_events = 1;
2456 return NULL;
2457}
2458
2459/* Size is determined by what has been committed */
2460static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2461{
2462 return rb_page_commit(bpage);
2463}
2464
2465static __always_inline unsigned
2466rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2467{
2468 return rb_page_commit(cpu_buffer->commit_page);
2469}
2470
2471static __always_inline unsigned
2472rb_event_index(struct ring_buffer_event *event)
2473{
2474 unsigned long addr = (unsigned long)event;
2475
2476 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2477}
2478
2479static void rb_inc_iter(struct ring_buffer_iter *iter)
2480{
2481 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2482
2483 /*
2484 * The iterator could be on the reader page (it starts there).
2485 * But the head could have moved, since the reader was
2486 * found. Check for this case and assign the iterator
2487 * to the head page instead of next.
2488 */
2489 if (iter->head_page == cpu_buffer->reader_page)
2490 iter->head_page = rb_set_head_page(cpu_buffer);
2491 else
2492 rb_inc_page(&iter->head_page);
2493
2494 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2495 iter->head = 0;
2496 iter->next_event = 0;
2497}
2498
2499/*
2500 * rb_handle_head_page - writer hit the head page
2501 *
2502 * Returns: +1 to retry page
2503 * 0 to continue
2504 * -1 on error
2505 */
2506static int
2507rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2508 struct buffer_page *tail_page,
2509 struct buffer_page *next_page)
2510{
2511 struct buffer_page *new_head;
2512 int entries;
2513 int type;
2514 int ret;
2515
2516 entries = rb_page_entries(next_page);
2517
2518 /*
2519 * The hard part is here. We need to move the head
2520 * forward, and protect against both readers on
2521 * other CPUs and writers coming in via interrupts.
2522 */
2523 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2524 RB_PAGE_HEAD);
2525
2526 /*
2527 * type can be one of four:
2528 * NORMAL - an interrupt already moved it for us
2529 * HEAD - we are the first to get here.
2530 * UPDATE - we are the interrupt interrupting
2531 * a current move.
2532 * MOVED - a reader on another CPU moved the next
2533 * pointer to its reader page. Give up
2534 * and try again.
2535 */
2536
2537 switch (type) {
2538 case RB_PAGE_HEAD:
2539 /*
2540 * We changed the head to UPDATE, thus
2541 * it is our responsibility to update
2542 * the counters.
2543 */
2544 local_add(entries, &cpu_buffer->overrun);
2545 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2546 local_inc(&cpu_buffer->pages_lost);
2547
2548 /*
2549 * The entries will be zeroed out when we move the
2550 * tail page.
2551 */
2552
2553 /* still more to do */
2554 break;
2555
2556 case RB_PAGE_UPDATE:
2557 /*
2558 * This is an interrupt that interrupt the
2559 * previous update. Still more to do.
2560 */
2561 break;
2562 case RB_PAGE_NORMAL:
2563 /*
2564 * An interrupt came in before the update
2565 * and processed this for us.
2566 * Nothing left to do.
2567 */
2568 return 1;
2569 case RB_PAGE_MOVED:
2570 /*
2571 * The reader is on another CPU and just did
2572 * a swap with our next_page.
2573 * Try again.
2574 */
2575 return 1;
2576 default:
2577 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2578 return -1;
2579 }
2580
2581 /*
2582 * Now that we are here, the old head pointer is
2583 * set to UPDATE. This will keep the reader from
2584 * swapping the head page with the reader page.
2585 * The reader (on another CPU) will spin till
2586 * we are finished.
2587 *
2588 * We just need to protect against interrupts
2589 * doing the job. We will set the next pointer
2590 * to HEAD. After that, we set the old pointer
2591 * to NORMAL, but only if it was HEAD before.
2592 * otherwise we are an interrupt, and only
2593 * want the outer most commit to reset it.
2594 */
2595 new_head = next_page;
2596 rb_inc_page(&new_head);
2597
2598 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2599 RB_PAGE_NORMAL);
2600
2601 /*
2602 * Valid returns are:
2603 * HEAD - an interrupt came in and already set it.
2604 * NORMAL - One of two things:
2605 * 1) We really set it.
2606 * 2) A bunch of interrupts came in and moved
2607 * the page forward again.
2608 */
2609 switch (ret) {
2610 case RB_PAGE_HEAD:
2611 case RB_PAGE_NORMAL:
2612 /* OK */
2613 break;
2614 default:
2615 RB_WARN_ON(cpu_buffer, 1);
2616 return -1;
2617 }
2618
2619 /*
2620 * It is possible that an interrupt came in,
2621 * set the head up, then more interrupts came in
2622 * and moved it again. When we get back here,
2623 * the page would have been set to NORMAL but we
2624 * just set it back to HEAD.
2625 *
2626 * How do you detect this? Well, if that happened
2627 * the tail page would have moved.
2628 */
2629 if (ret == RB_PAGE_NORMAL) {
2630 struct buffer_page *buffer_tail_page;
2631
2632 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2633 /*
2634 * If the tail had moved passed next, then we need
2635 * to reset the pointer.
2636 */
2637 if (buffer_tail_page != tail_page &&
2638 buffer_tail_page != next_page)
2639 rb_head_page_set_normal(cpu_buffer, new_head,
2640 next_page,
2641 RB_PAGE_HEAD);
2642 }
2643
2644 /*
2645 * If this was the outer most commit (the one that
2646 * changed the original pointer from HEAD to UPDATE),
2647 * then it is up to us to reset it to NORMAL.
2648 */
2649 if (type == RB_PAGE_HEAD) {
2650 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2651 tail_page,
2652 RB_PAGE_UPDATE);
2653 if (RB_WARN_ON(cpu_buffer,
2654 ret != RB_PAGE_UPDATE))
2655 return -1;
2656 }
2657
2658 return 0;
2659}
2660
2661static inline void
2662rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2663 unsigned long tail, struct rb_event_info *info)
2664{
2665 struct buffer_page *tail_page = info->tail_page;
2666 struct ring_buffer_event *event;
2667 unsigned long length = info->length;
2668
2669 /*
2670 * Only the event that crossed the page boundary
2671 * must fill the old tail_page with padding.
2672 */
2673 if (tail >= BUF_PAGE_SIZE) {
2674 /*
2675 * If the page was filled, then we still need
2676 * to update the real_end. Reset it to zero
2677 * and the reader will ignore it.
2678 */
2679 if (tail == BUF_PAGE_SIZE)
2680 tail_page->real_end = 0;
2681
2682 local_sub(length, &tail_page->write);
2683 return;
2684 }
2685
2686 event = __rb_page_index(tail_page, tail);
2687
2688 /* account for padding bytes */
2689 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2690
2691 /*
2692 * Save the original length to the meta data.
2693 * This will be used by the reader to add lost event
2694 * counter.
2695 */
2696 tail_page->real_end = tail;
2697
2698 /*
2699 * If this event is bigger than the minimum size, then
2700 * we need to be careful that we don't subtract the
2701 * write counter enough to allow another writer to slip
2702 * in on this page.
2703 * We put in a discarded commit instead, to make sure
2704 * that this space is not used again.
2705 *
2706 * If we are less than the minimum size, we don't need to
2707 * worry about it.
2708 */
2709 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2710 /* No room for any events */
2711
2712 /* Mark the rest of the page with padding */
2713 rb_event_set_padding(event);
2714
2715 /* Make sure the padding is visible before the write update */
2716 smp_wmb();
2717
2718 /* Set the write back to the previous setting */
2719 local_sub(length, &tail_page->write);
2720 return;
2721 }
2722
2723 /* Put in a discarded event */
2724 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2725 event->type_len = RINGBUF_TYPE_PADDING;
2726 /* time delta must be non zero */
2727 event->time_delta = 1;
2728
2729 /* Make sure the padding is visible before the tail_page->write update */
2730 smp_wmb();
2731
2732 /* Set write to end of buffer */
2733 length = (tail + length) - BUF_PAGE_SIZE;
2734 local_sub(length, &tail_page->write);
2735}
2736
2737static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2738
2739/*
2740 * This is the slow path, force gcc not to inline it.
2741 */
2742static noinline struct ring_buffer_event *
2743rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2744 unsigned long tail, struct rb_event_info *info)
2745{
2746 struct buffer_page *tail_page = info->tail_page;
2747 struct buffer_page *commit_page = cpu_buffer->commit_page;
2748 struct trace_buffer *buffer = cpu_buffer->buffer;
2749 struct buffer_page *next_page;
2750 int ret;
2751
2752 next_page = tail_page;
2753
2754 rb_inc_page(&next_page);
2755
2756 /*
2757 * If for some reason, we had an interrupt storm that made
2758 * it all the way around the buffer, bail, and warn
2759 * about it.
2760 */
2761 if (unlikely(next_page == commit_page)) {
2762 local_inc(&cpu_buffer->commit_overrun);
2763 goto out_reset;
2764 }
2765
2766 /*
2767 * This is where the fun begins!
2768 *
2769 * We are fighting against races between a reader that
2770 * could be on another CPU trying to swap its reader
2771 * page with the buffer head.
2772 *
2773 * We are also fighting against interrupts coming in and
2774 * moving the head or tail on us as well.
2775 *
2776 * If the next page is the head page then we have filled
2777 * the buffer, unless the commit page is still on the
2778 * reader page.
2779 */
2780 if (rb_is_head_page(next_page, &tail_page->list)) {
2781
2782 /*
2783 * If the commit is not on the reader page, then
2784 * move the header page.
2785 */
2786 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2787 /*
2788 * If we are not in overwrite mode,
2789 * this is easy, just stop here.
2790 */
2791 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2792 local_inc(&cpu_buffer->dropped_events);
2793 goto out_reset;
2794 }
2795
2796 ret = rb_handle_head_page(cpu_buffer,
2797 tail_page,
2798 next_page);
2799 if (ret < 0)
2800 goto out_reset;
2801 if (ret)
2802 goto out_again;
2803 } else {
2804 /*
2805 * We need to be careful here too. The
2806 * commit page could still be on the reader
2807 * page. We could have a small buffer, and
2808 * have filled up the buffer with events
2809 * from interrupts and such, and wrapped.
2810 *
2811 * Note, if the tail page is also on the
2812 * reader_page, we let it move out.
2813 */
2814 if (unlikely((cpu_buffer->commit_page !=
2815 cpu_buffer->tail_page) &&
2816 (cpu_buffer->commit_page ==
2817 cpu_buffer->reader_page))) {
2818 local_inc(&cpu_buffer->commit_overrun);
2819 goto out_reset;
2820 }
2821 }
2822 }
2823
2824 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2825
2826 out_again:
2827
2828 rb_reset_tail(cpu_buffer, tail, info);
2829
2830 /* Commit what we have for now. */
2831 rb_end_commit(cpu_buffer);
2832 /* rb_end_commit() decs committing */
2833 local_inc(&cpu_buffer->committing);
2834
2835 /* fail and let the caller try again */
2836 return ERR_PTR(-EAGAIN);
2837
2838 out_reset:
2839 /* reset write */
2840 rb_reset_tail(cpu_buffer, tail, info);
2841
2842 return NULL;
2843}
2844
2845/* Slow path */
2846static struct ring_buffer_event *
2847rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2848{
2849 if (abs)
2850 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2851 else
2852 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2853
2854 /* Not the first event on the page, or not delta? */
2855 if (abs || rb_event_index(event)) {
2856 event->time_delta = delta & TS_MASK;
2857 event->array[0] = delta >> TS_SHIFT;
2858 } else {
2859 /* nope, just zero it */
2860 event->time_delta = 0;
2861 event->array[0] = 0;
2862 }
2863
2864 return skip_time_extend(event);
2865}
2866
2867#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2868static inline bool sched_clock_stable(void)
2869{
2870 return true;
2871}
2872#endif
2873
2874static void
2875rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2876 struct rb_event_info *info)
2877{
2878 u64 write_stamp;
2879
2880 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2881 (unsigned long long)info->delta,
2882 (unsigned long long)info->ts,
2883 (unsigned long long)info->before,
2884 (unsigned long long)info->after,
2885 (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2886 sched_clock_stable() ? "" :
2887 "If you just came from a suspend/resume,\n"
2888 "please switch to the trace global clock:\n"
2889 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2890 "or add trace_clock=global to the kernel command line\n");
2891}
2892
2893static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2894 struct ring_buffer_event **event,
2895 struct rb_event_info *info,
2896 u64 *delta,
2897 unsigned int *length)
2898{
2899 bool abs = info->add_timestamp &
2900 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2901
2902 if (unlikely(info->delta > (1ULL << 59))) {
2903 /*
2904 * Some timers can use more than 59 bits, and when a timestamp
2905 * is added to the buffer, it will lose those bits.
2906 */
2907 if (abs && (info->ts & TS_MSB)) {
2908 info->delta &= ABS_TS_MASK;
2909
2910 /* did the clock go backwards */
2911 } else if (info->before == info->after && info->before > info->ts) {
2912 /* not interrupted */
2913 static int once;
2914
2915 /*
2916 * This is possible with a recalibrating of the TSC.
2917 * Do not produce a call stack, but just report it.
2918 */
2919 if (!once) {
2920 once++;
2921 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2922 info->before, info->ts);
2923 }
2924 } else
2925 rb_check_timestamp(cpu_buffer, info);
2926 if (!abs)
2927 info->delta = 0;
2928 }
2929 *event = rb_add_time_stamp(*event, info->delta, abs);
2930 *length -= RB_LEN_TIME_EXTEND;
2931 *delta = 0;
2932}
2933
2934/**
2935 * rb_update_event - update event type and data
2936 * @cpu_buffer: The per cpu buffer of the @event
2937 * @event: the event to update
2938 * @info: The info to update the @event with (contains length and delta)
2939 *
2940 * Update the type and data fields of the @event. The length
2941 * is the actual size that is written to the ring buffer,
2942 * and with this, we can determine what to place into the
2943 * data field.
2944 */
2945static void
2946rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2947 struct ring_buffer_event *event,
2948 struct rb_event_info *info)
2949{
2950 unsigned length = info->length;
2951 u64 delta = info->delta;
2952 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2953
2954 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2955 cpu_buffer->event_stamp[nest] = info->ts;
2956
2957 /*
2958 * If we need to add a timestamp, then we
2959 * add it to the start of the reserved space.
2960 */
2961 if (unlikely(info->add_timestamp))
2962 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2963
2964 event->time_delta = delta;
2965 length -= RB_EVNT_HDR_SIZE;
2966 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2967 event->type_len = 0;
2968 event->array[0] = length;
2969 } else
2970 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2971}
2972
2973static unsigned rb_calculate_event_length(unsigned length)
2974{
2975 struct ring_buffer_event event; /* Used only for sizeof array */
2976
2977 /* zero length can cause confusions */
2978 if (!length)
2979 length++;
2980
2981 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2982 length += sizeof(event.array[0]);
2983
2984 length += RB_EVNT_HDR_SIZE;
2985 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2986
2987 /*
2988 * In case the time delta is larger than the 27 bits for it
2989 * in the header, we need to add a timestamp. If another
2990 * event comes in when trying to discard this one to increase
2991 * the length, then the timestamp will be added in the allocated
2992 * space of this event. If length is bigger than the size needed
2993 * for the TIME_EXTEND, then padding has to be used. The events
2994 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2995 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2996 * As length is a multiple of 4, we only need to worry if it
2997 * is 12 (RB_LEN_TIME_EXTEND + 4).
2998 */
2999 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
3000 length += RB_ALIGNMENT;
3001
3002 return length;
3003}
3004
3005static u64 rb_time_delta(struct ring_buffer_event *event)
3006{
3007 switch (event->type_len) {
3008 case RINGBUF_TYPE_PADDING:
3009 return 0;
3010
3011 case RINGBUF_TYPE_TIME_EXTEND:
3012 return rb_event_time_stamp(event);
3013
3014 case RINGBUF_TYPE_TIME_STAMP:
3015 return 0;
3016
3017 case RINGBUF_TYPE_DATA:
3018 return event->time_delta;
3019 default:
3020 return 0;
3021 }
3022}
3023
3024static inline int
3025rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
3026 struct ring_buffer_event *event)
3027{
3028 unsigned long new_index, old_index;
3029 struct buffer_page *bpage;
3030 unsigned long index;
3031 unsigned long addr;
3032 u64 write_stamp;
3033 u64 delta;
3034
3035 new_index = rb_event_index(event);
3036 old_index = new_index + rb_event_ts_length(event);
3037 addr = (unsigned long)event;
3038 addr &= PAGE_MASK;
3039
3040 bpage = READ_ONCE(cpu_buffer->tail_page);
3041
3042 delta = rb_time_delta(event);
3043
3044 if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
3045 return 0;
3046
3047 /* Make sure the write stamp is read before testing the location */
3048 barrier();
3049
3050 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
3051 unsigned long write_mask =
3052 local_read(&bpage->write) & ~RB_WRITE_MASK;
3053 unsigned long event_length = rb_event_length(event);
3054
3055 /* Something came in, can't discard */
3056 if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
3057 write_stamp, write_stamp - delta))
3058 return 0;
3059
3060 /*
3061 * It's possible that the event time delta is zero
3062 * (has the same time stamp as the previous event)
3063 * in which case write_stamp and before_stamp could
3064 * be the same. In such a case, force before_stamp
3065 * to be different than write_stamp. It doesn't
3066 * matter what it is, as long as its different.
3067 */
3068 if (!delta)
3069 rb_time_set(&cpu_buffer->before_stamp, 0);
3070
3071 /*
3072 * If an event were to come in now, it would see that the
3073 * write_stamp and the before_stamp are different, and assume
3074 * that this event just added itself before updating
3075 * the write stamp. The interrupting event will fix the
3076 * write stamp for us, and use the before stamp as its delta.
3077 */
3078
3079 /*
3080 * This is on the tail page. It is possible that
3081 * a write could come in and move the tail page
3082 * and write to the next page. That is fine
3083 * because we just shorten what is on this page.
3084 */
3085 old_index += write_mask;
3086 new_index += write_mask;
3087 index = local_cmpxchg(&bpage->write, old_index, new_index);
3088 if (index == old_index) {
3089 /* update counters */
3090 local_sub(event_length, &cpu_buffer->entries_bytes);
3091 return 1;
3092 }
3093 }
3094
3095 /* could not discard */
3096 return 0;
3097}
3098
3099static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
3100{
3101 local_inc(&cpu_buffer->committing);
3102 local_inc(&cpu_buffer->commits);
3103}
3104
3105static __always_inline void
3106rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
3107{
3108 unsigned long max_count;
3109
3110 /*
3111 * We only race with interrupts and NMIs on this CPU.
3112 * If we own the commit event, then we can commit
3113 * all others that interrupted us, since the interruptions
3114 * are in stack format (they finish before they come
3115 * back to us). This allows us to do a simple loop to
3116 * assign the commit to the tail.
3117 */
3118 again:
3119 max_count = cpu_buffer->nr_pages * 100;
3120
3121 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
3122 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
3123 return;
3124 if (RB_WARN_ON(cpu_buffer,
3125 rb_is_reader_page(cpu_buffer->tail_page)))
3126 return;
3127 local_set(&cpu_buffer->commit_page->page->commit,
3128 rb_page_write(cpu_buffer->commit_page));
3129 rb_inc_page(&cpu_buffer->commit_page);
3130 /* add barrier to keep gcc from optimizing too much */
3131 barrier();
3132 }
3133 while (rb_commit_index(cpu_buffer) !=
3134 rb_page_write(cpu_buffer->commit_page)) {
3135
3136 local_set(&cpu_buffer->commit_page->page->commit,
3137 rb_page_write(cpu_buffer->commit_page));
3138 RB_WARN_ON(cpu_buffer,
3139 local_read(&cpu_buffer->commit_page->page->commit) &
3140 ~RB_WRITE_MASK);
3141 barrier();
3142 }
3143
3144 /* again, keep gcc from optimizing */
3145 barrier();
3146
3147 /*
3148 * If an interrupt came in just after the first while loop
3149 * and pushed the tail page forward, we will be left with
3150 * a dangling commit that will never go forward.
3151 */
3152 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3153 goto again;
3154}
3155
3156static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3157{
3158 unsigned long commits;
3159
3160 if (RB_WARN_ON(cpu_buffer,
3161 !local_read(&cpu_buffer->committing)))
3162 return;
3163
3164 again:
3165 commits = local_read(&cpu_buffer->commits);
3166 /* synchronize with interrupts */
3167 barrier();
3168 if (local_read(&cpu_buffer->committing) == 1)
3169 rb_set_commit_to_write(cpu_buffer);
3170
3171 local_dec(&cpu_buffer->committing);
3172
3173 /* synchronize with interrupts */
3174 barrier();
3175
3176 /*
3177 * Need to account for interrupts coming in between the
3178 * updating of the commit page and the clearing of the
3179 * committing counter.
3180 */
3181 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3182 !local_read(&cpu_buffer->committing)) {
3183 local_inc(&cpu_buffer->committing);
3184 goto again;
3185 }
3186}
3187
3188static inline void rb_event_discard(struct ring_buffer_event *event)
3189{
3190 if (extended_time(event))
3191 event = skip_time_extend(event);
3192
3193 /* array[0] holds the actual length for the discarded event */
3194 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3195 event->type_len = RINGBUF_TYPE_PADDING;
3196 /* time delta must be non zero */
3197 if (!event->time_delta)
3198 event->time_delta = 1;
3199}
3200
3201static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3202{
3203 local_inc(&cpu_buffer->entries);
3204 rb_end_commit(cpu_buffer);
3205}
3206
3207static __always_inline void
3208rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3209{
3210 if (buffer->irq_work.waiters_pending) {
3211 buffer->irq_work.waiters_pending = false;
3212 /* irq_work_queue() supplies it's own memory barriers */
3213 irq_work_queue(&buffer->irq_work.work);
3214 }
3215
3216 if (cpu_buffer->irq_work.waiters_pending) {
3217 cpu_buffer->irq_work.waiters_pending = false;
3218 /* irq_work_queue() supplies it's own memory barriers */
3219 irq_work_queue(&cpu_buffer->irq_work.work);
3220 }
3221
3222 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3223 return;
3224
3225 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3226 return;
3227
3228 if (!cpu_buffer->irq_work.full_waiters_pending)
3229 return;
3230
3231 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3232
3233 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3234 return;
3235
3236 cpu_buffer->irq_work.wakeup_full = true;
3237 cpu_buffer->irq_work.full_waiters_pending = false;
3238 /* irq_work_queue() supplies it's own memory barriers */
3239 irq_work_queue(&cpu_buffer->irq_work.work);
3240}
3241
3242#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3243# define do_ring_buffer_record_recursion() \
3244 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3245#else
3246# define do_ring_buffer_record_recursion() do { } while (0)
3247#endif
3248
3249/*
3250 * The lock and unlock are done within a preempt disable section.
3251 * The current_context per_cpu variable can only be modified
3252 * by the current task between lock and unlock. But it can
3253 * be modified more than once via an interrupt. To pass this
3254 * information from the lock to the unlock without having to
3255 * access the 'in_interrupt()' functions again (which do show
3256 * a bit of overhead in something as critical as function tracing,
3257 * we use a bitmask trick.
3258 *
3259 * bit 1 = NMI context
3260 * bit 2 = IRQ context
3261 * bit 3 = SoftIRQ context
3262 * bit 4 = normal context.
3263 *
3264 * This works because this is the order of contexts that can
3265 * preempt other contexts. A SoftIRQ never preempts an IRQ
3266 * context.
3267 *
3268 * When the context is determined, the corresponding bit is
3269 * checked and set (if it was set, then a recursion of that context
3270 * happened).
3271 *
3272 * On unlock, we need to clear this bit. To do so, just subtract
3273 * 1 from the current_context and AND it to itself.
3274 *
3275 * (binary)
3276 * 101 - 1 = 100
3277 * 101 & 100 = 100 (clearing bit zero)
3278 *
3279 * 1010 - 1 = 1001
3280 * 1010 & 1001 = 1000 (clearing bit 1)
3281 *
3282 * The least significant bit can be cleared this way, and it
3283 * just so happens that it is the same bit corresponding to
3284 * the current context.
3285 *
3286 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3287 * is set when a recursion is detected at the current context, and if
3288 * the TRANSITION bit is already set, it will fail the recursion.
3289 * This is needed because there's a lag between the changing of
3290 * interrupt context and updating the preempt count. In this case,
3291 * a false positive will be found. To handle this, one extra recursion
3292 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3293 * bit is already set, then it is considered a recursion and the function
3294 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3295 *
3296 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3297 * to be cleared. Even if it wasn't the context that set it. That is,
3298 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3299 * is called before preempt_count() is updated, since the check will
3300 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3301 * NMI then comes in, it will set the NMI bit, but when the NMI code
3302 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3303 * and leave the NMI bit set. But this is fine, because the interrupt
3304 * code that set the TRANSITION bit will then clear the NMI bit when it
3305 * calls trace_recursive_unlock(). If another NMI comes in, it will
3306 * set the TRANSITION bit and continue.
3307 *
3308 * Note: The TRANSITION bit only handles a single transition between context.
3309 */
3310
3311static __always_inline int
3312trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3313{
3314 unsigned int val = cpu_buffer->current_context;
3315 int bit = interrupt_context_level();
3316
3317 bit = RB_CTX_NORMAL - bit;
3318
3319 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3320 /*
3321 * It is possible that this was called by transitioning
3322 * between interrupt context, and preempt_count() has not
3323 * been updated yet. In this case, use the TRANSITION bit.
3324 */
3325 bit = RB_CTX_TRANSITION;
3326 if (val & (1 << (bit + cpu_buffer->nest))) {
3327 do_ring_buffer_record_recursion();
3328 return 1;
3329 }
3330 }
3331
3332 val |= (1 << (bit + cpu_buffer->nest));
3333 cpu_buffer->current_context = val;
3334
3335 return 0;
3336}
3337
3338static __always_inline void
3339trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3340{
3341 cpu_buffer->current_context &=
3342 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3343}
3344
3345/* The recursive locking above uses 5 bits */
3346#define NESTED_BITS 5
3347
3348/**
3349 * ring_buffer_nest_start - Allow to trace while nested
3350 * @buffer: The ring buffer to modify
3351 *
3352 * The ring buffer has a safety mechanism to prevent recursion.
3353 * But there may be a case where a trace needs to be done while
3354 * tracing something else. In this case, calling this function
3355 * will allow this function to nest within a currently active
3356 * ring_buffer_lock_reserve().
3357 *
3358 * Call this function before calling another ring_buffer_lock_reserve() and
3359 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3360 */
3361void ring_buffer_nest_start(struct trace_buffer *buffer)
3362{
3363 struct ring_buffer_per_cpu *cpu_buffer;
3364 int cpu;
3365
3366 /* Enabled by ring_buffer_nest_end() */
3367 preempt_disable_notrace();
3368 cpu = raw_smp_processor_id();
3369 cpu_buffer = buffer->buffers[cpu];
3370 /* This is the shift value for the above recursive locking */
3371 cpu_buffer->nest += NESTED_BITS;
3372}
3373
3374/**
3375 * ring_buffer_nest_end - Allow to trace while nested
3376 * @buffer: The ring buffer to modify
3377 *
3378 * Must be called after ring_buffer_nest_start() and after the
3379 * ring_buffer_unlock_commit().
3380 */
3381void ring_buffer_nest_end(struct trace_buffer *buffer)
3382{
3383 struct ring_buffer_per_cpu *cpu_buffer;
3384 int cpu;
3385
3386 /* disabled by ring_buffer_nest_start() */
3387 cpu = raw_smp_processor_id();
3388 cpu_buffer = buffer->buffers[cpu];
3389 /* This is the shift value for the above recursive locking */
3390 cpu_buffer->nest -= NESTED_BITS;
3391 preempt_enable_notrace();
3392}
3393
3394/**
3395 * ring_buffer_unlock_commit - commit a reserved
3396 * @buffer: The buffer to commit to
3397 * @event: The event pointer to commit.
3398 *
3399 * This commits the data to the ring buffer, and releases any locks held.
3400 *
3401 * Must be paired with ring_buffer_lock_reserve.
3402 */
3403int ring_buffer_unlock_commit(struct trace_buffer *buffer)
3404{
3405 struct ring_buffer_per_cpu *cpu_buffer;
3406 int cpu = raw_smp_processor_id();
3407
3408 cpu_buffer = buffer->buffers[cpu];
3409
3410 rb_commit(cpu_buffer);
3411
3412 rb_wakeups(buffer, cpu_buffer);
3413
3414 trace_recursive_unlock(cpu_buffer);
3415
3416 preempt_enable_notrace();
3417
3418 return 0;
3419}
3420EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3421
3422/* Special value to validate all deltas on a page. */
3423#define CHECK_FULL_PAGE 1L
3424
3425#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3426static void dump_buffer_page(struct buffer_data_page *bpage,
3427 struct rb_event_info *info,
3428 unsigned long tail)
3429{
3430 struct ring_buffer_event *event;
3431 u64 ts, delta;
3432 int e;
3433
3434 ts = bpage->time_stamp;
3435 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3436
3437 for (e = 0; e < tail; e += rb_event_length(event)) {
3438
3439 event = (struct ring_buffer_event *)(bpage->data + e);
3440
3441 switch (event->type_len) {
3442
3443 case RINGBUF_TYPE_TIME_EXTEND:
3444 delta = rb_event_time_stamp(event);
3445 ts += delta;
3446 pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta);
3447 break;
3448
3449 case RINGBUF_TYPE_TIME_STAMP:
3450 delta = rb_event_time_stamp(event);
3451 ts = rb_fix_abs_ts(delta, ts);
3452 pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta);
3453 break;
3454
3455 case RINGBUF_TYPE_PADDING:
3456 ts += event->time_delta;
3457 pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta);
3458 break;
3459
3460 case RINGBUF_TYPE_DATA:
3461 ts += event->time_delta;
3462 pr_warn(" [%lld] delta:%d\n", ts, event->time_delta);
3463 break;
3464
3465 default:
3466 break;
3467 }
3468 }
3469}
3470
3471static DEFINE_PER_CPU(atomic_t, checking);
3472static atomic_t ts_dump;
3473
3474/*
3475 * Check if the current event time stamp matches the deltas on
3476 * the buffer page.
3477 */
3478static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3479 struct rb_event_info *info,
3480 unsigned long tail)
3481{
3482 struct ring_buffer_event *event;
3483 struct buffer_data_page *bpage;
3484 u64 ts, delta;
3485 bool full = false;
3486 int e;
3487
3488 bpage = info->tail_page->page;
3489
3490 if (tail == CHECK_FULL_PAGE) {
3491 full = true;
3492 tail = local_read(&bpage->commit);
3493 } else if (info->add_timestamp &
3494 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3495 /* Ignore events with absolute time stamps */
3496 return;
3497 }
3498
3499 /*
3500 * Do not check the first event (skip possible extends too).
3501 * Also do not check if previous events have not been committed.
3502 */
3503 if (tail <= 8 || tail > local_read(&bpage->commit))
3504 return;
3505
3506 /*
3507 * If this interrupted another event,
3508 */
3509 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3510 goto out;
3511
3512 ts = bpage->time_stamp;
3513
3514 for (e = 0; e < tail; e += rb_event_length(event)) {
3515
3516 event = (struct ring_buffer_event *)(bpage->data + e);
3517
3518 switch (event->type_len) {
3519
3520 case RINGBUF_TYPE_TIME_EXTEND:
3521 delta = rb_event_time_stamp(event);
3522 ts += delta;
3523 break;
3524
3525 case RINGBUF_TYPE_TIME_STAMP:
3526 delta = rb_event_time_stamp(event);
3527 ts = rb_fix_abs_ts(delta, ts);
3528 break;
3529
3530 case RINGBUF_TYPE_PADDING:
3531 if (event->time_delta == 1)
3532 break;
3533 fallthrough;
3534 case RINGBUF_TYPE_DATA:
3535 ts += event->time_delta;
3536 break;
3537
3538 default:
3539 RB_WARN_ON(cpu_buffer, 1);
3540 }
3541 }
3542 if ((full && ts > info->ts) ||
3543 (!full && ts + info->delta != info->ts)) {
3544 /* If another report is happening, ignore this one */
3545 if (atomic_inc_return(&ts_dump) != 1) {
3546 atomic_dec(&ts_dump);
3547 goto out;
3548 }
3549 atomic_inc(&cpu_buffer->record_disabled);
3550 /* There's some cases in boot up that this can happen */
3551 WARN_ON_ONCE(system_state != SYSTEM_BOOTING);
3552 pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n",
3553 cpu_buffer->cpu,
3554 ts + info->delta, info->ts, info->delta,
3555 info->before, info->after,
3556 full ? " (full)" : "");
3557 dump_buffer_page(bpage, info, tail);
3558 atomic_dec(&ts_dump);
3559 /* Do not re-enable checking */
3560 return;
3561 }
3562out:
3563 atomic_dec(this_cpu_ptr(&checking));
3564}
3565#else
3566static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3567 struct rb_event_info *info,
3568 unsigned long tail)
3569{
3570}
3571#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3572
3573static struct ring_buffer_event *
3574__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3575 struct rb_event_info *info)
3576{
3577 struct ring_buffer_event *event;
3578 struct buffer_page *tail_page;
3579 unsigned long tail, write, w;
3580 bool a_ok;
3581 bool b_ok;
3582
3583 /* Don't let the compiler play games with cpu_buffer->tail_page */
3584 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3585
3586 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3587 barrier();
3588 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3589 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3590 barrier();
3591 info->ts = rb_time_stamp(cpu_buffer->buffer);
3592
3593 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3594 info->delta = info->ts;
3595 } else {
3596 /*
3597 * If interrupting an event time update, we may need an
3598 * absolute timestamp.
3599 * Don't bother if this is the start of a new page (w == 0).
3600 */
3601 if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3602 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3603 info->length += RB_LEN_TIME_EXTEND;
3604 } else {
3605 info->delta = info->ts - info->after;
3606 if (unlikely(test_time_stamp(info->delta))) {
3607 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3608 info->length += RB_LEN_TIME_EXTEND;
3609 }
3610 }
3611 }
3612
3613 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3614
3615 /*C*/ write = local_add_return(info->length, &tail_page->write);
3616
3617 /* set write to only the index of the write */
3618 write &= RB_WRITE_MASK;
3619
3620 tail = write - info->length;
3621
3622 /* See if we shot pass the end of this buffer page */
3623 if (unlikely(write > BUF_PAGE_SIZE)) {
3624 /* before and after may now different, fix it up*/
3625 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3626 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3627 if (a_ok && b_ok && info->before != info->after)
3628 (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3629 info->before, info->after);
3630 if (a_ok && b_ok)
3631 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3632 return rb_move_tail(cpu_buffer, tail, info);
3633 }
3634
3635 if (likely(tail == w)) {
3636 u64 save_before;
3637 bool s_ok;
3638
3639 /* Nothing interrupted us between A and C */
3640 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3641 barrier();
3642 /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3643 RB_WARN_ON(cpu_buffer, !s_ok);
3644 if (likely(!(info->add_timestamp &
3645 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3646 /* This did not interrupt any time update */
3647 info->delta = info->ts - info->after;
3648 else
3649 /* Just use full timestamp for interrupting event */
3650 info->delta = info->ts;
3651 barrier();
3652 check_buffer(cpu_buffer, info, tail);
3653 if (unlikely(info->ts != save_before)) {
3654 /* SLOW PATH - Interrupted between C and E */
3655
3656 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3657 RB_WARN_ON(cpu_buffer, !a_ok);
3658
3659 /* Write stamp must only go forward */
3660 if (save_before > info->after) {
3661 /*
3662 * We do not care about the result, only that
3663 * it gets updated atomically.
3664 */
3665 (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3666 info->after, save_before);
3667 }
3668 }
3669 } else {
3670 u64 ts;
3671 /* SLOW PATH - Interrupted between A and C */
3672 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3673 /* Was interrupted before here, write_stamp must be valid */
3674 RB_WARN_ON(cpu_buffer, !a_ok);
3675 ts = rb_time_stamp(cpu_buffer->buffer);
3676 barrier();
3677 /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3678 info->after < ts &&
3679 rb_time_cmpxchg(&cpu_buffer->write_stamp,
3680 info->after, ts)) {
3681 /* Nothing came after this event between C and E */
3682 info->delta = ts - info->after;
3683 } else {
3684 /*
3685 * Interrupted between C and E:
3686 * Lost the previous events time stamp. Just set the
3687 * delta to zero, and this will be the same time as
3688 * the event this event interrupted. And the events that
3689 * came after this will still be correct (as they would
3690 * have built their delta on the previous event.
3691 */
3692 info->delta = 0;
3693 }
3694 info->ts = ts;
3695 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3696 }
3697
3698 /*
3699 * If this is the first commit on the page, then it has the same
3700 * timestamp as the page itself.
3701 */
3702 if (unlikely(!tail && !(info->add_timestamp &
3703 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3704 info->delta = 0;
3705
3706 /* We reserved something on the buffer */
3707
3708 event = __rb_page_index(tail_page, tail);
3709 rb_update_event(cpu_buffer, event, info);
3710
3711 local_inc(&tail_page->entries);
3712
3713 /*
3714 * If this is the first commit on the page, then update
3715 * its timestamp.
3716 */
3717 if (unlikely(!tail))
3718 tail_page->page->time_stamp = info->ts;
3719
3720 /* account for these added bytes */
3721 local_add(info->length, &cpu_buffer->entries_bytes);
3722
3723 return event;
3724}
3725
3726static __always_inline struct ring_buffer_event *
3727rb_reserve_next_event(struct trace_buffer *buffer,
3728 struct ring_buffer_per_cpu *cpu_buffer,
3729 unsigned long length)
3730{
3731 struct ring_buffer_event *event;
3732 struct rb_event_info info;
3733 int nr_loops = 0;
3734 int add_ts_default;
3735
3736 rb_start_commit(cpu_buffer);
3737 /* The commit page can not change after this */
3738
3739#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3740 /*
3741 * Due to the ability to swap a cpu buffer from a buffer
3742 * it is possible it was swapped before we committed.
3743 * (committing stops a swap). We check for it here and
3744 * if it happened, we have to fail the write.
3745 */
3746 barrier();
3747 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3748 local_dec(&cpu_buffer->committing);
3749 local_dec(&cpu_buffer->commits);
3750 return NULL;
3751 }
3752#endif
3753
3754 info.length = rb_calculate_event_length(length);
3755
3756 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3757 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3758 info.length += RB_LEN_TIME_EXTEND;
3759 } else {
3760 add_ts_default = RB_ADD_STAMP_NONE;
3761 }
3762
3763 again:
3764 info.add_timestamp = add_ts_default;
3765 info.delta = 0;
3766
3767 /*
3768 * We allow for interrupts to reenter here and do a trace.
3769 * If one does, it will cause this original code to loop
3770 * back here. Even with heavy interrupts happening, this
3771 * should only happen a few times in a row. If this happens
3772 * 1000 times in a row, there must be either an interrupt
3773 * storm or we have something buggy.
3774 * Bail!
3775 */
3776 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3777 goto out_fail;
3778
3779 event = __rb_reserve_next(cpu_buffer, &info);
3780
3781 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3782 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3783 info.length -= RB_LEN_TIME_EXTEND;
3784 goto again;
3785 }
3786
3787 if (likely(event))
3788 return event;
3789 out_fail:
3790 rb_end_commit(cpu_buffer);
3791 return NULL;
3792}
3793
3794/**
3795 * ring_buffer_lock_reserve - reserve a part of the buffer
3796 * @buffer: the ring buffer to reserve from
3797 * @length: the length of the data to reserve (excluding event header)
3798 *
3799 * Returns a reserved event on the ring buffer to copy directly to.
3800 * The user of this interface will need to get the body to write into
3801 * and can use the ring_buffer_event_data() interface.
3802 *
3803 * The length is the length of the data needed, not the event length
3804 * which also includes the event header.
3805 *
3806 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3807 * If NULL is returned, then nothing has been allocated or locked.
3808 */
3809struct ring_buffer_event *
3810ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3811{
3812 struct ring_buffer_per_cpu *cpu_buffer;
3813 struct ring_buffer_event *event;
3814 int cpu;
3815
3816 /* If we are tracing schedule, we don't want to recurse */
3817 preempt_disable_notrace();
3818
3819 if (unlikely(atomic_read(&buffer->record_disabled)))
3820 goto out;
3821
3822 cpu = raw_smp_processor_id();
3823
3824 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3825 goto out;
3826
3827 cpu_buffer = buffer->buffers[cpu];
3828
3829 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3830 goto out;
3831
3832 if (unlikely(length > BUF_MAX_DATA_SIZE))
3833 goto out;
3834
3835 if (unlikely(trace_recursive_lock(cpu_buffer)))
3836 goto out;
3837
3838 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3839 if (!event)
3840 goto out_unlock;
3841
3842 return event;
3843
3844 out_unlock:
3845 trace_recursive_unlock(cpu_buffer);
3846 out:
3847 preempt_enable_notrace();
3848 return NULL;
3849}
3850EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3851
3852/*
3853 * Decrement the entries to the page that an event is on.
3854 * The event does not even need to exist, only the pointer
3855 * to the page it is on. This may only be called before the commit
3856 * takes place.
3857 */
3858static inline void
3859rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3860 struct ring_buffer_event *event)
3861{
3862 unsigned long addr = (unsigned long)event;
3863 struct buffer_page *bpage = cpu_buffer->commit_page;
3864 struct buffer_page *start;
3865
3866 addr &= PAGE_MASK;
3867
3868 /* Do the likely case first */
3869 if (likely(bpage->page == (void *)addr)) {
3870 local_dec(&bpage->entries);
3871 return;
3872 }
3873
3874 /*
3875 * Because the commit page may be on the reader page we
3876 * start with the next page and check the end loop there.
3877 */
3878 rb_inc_page(&bpage);
3879 start = bpage;
3880 do {
3881 if (bpage->page == (void *)addr) {
3882 local_dec(&bpage->entries);
3883 return;
3884 }
3885 rb_inc_page(&bpage);
3886 } while (bpage != start);
3887
3888 /* commit not part of this buffer?? */
3889 RB_WARN_ON(cpu_buffer, 1);
3890}
3891
3892/**
3893 * ring_buffer_discard_commit - discard an event that has not been committed
3894 * @buffer: the ring buffer
3895 * @event: non committed event to discard
3896 *
3897 * Sometimes an event that is in the ring buffer needs to be ignored.
3898 * This function lets the user discard an event in the ring buffer
3899 * and then that event will not be read later.
3900 *
3901 * This function only works if it is called before the item has been
3902 * committed. It will try to free the event from the ring buffer
3903 * if another event has not been added behind it.
3904 *
3905 * If another event has been added behind it, it will set the event
3906 * up as discarded, and perform the commit.
3907 *
3908 * If this function is called, do not call ring_buffer_unlock_commit on
3909 * the event.
3910 */
3911void ring_buffer_discard_commit(struct trace_buffer *buffer,
3912 struct ring_buffer_event *event)
3913{
3914 struct ring_buffer_per_cpu *cpu_buffer;
3915 int cpu;
3916
3917 /* The event is discarded regardless */
3918 rb_event_discard(event);
3919
3920 cpu = smp_processor_id();
3921 cpu_buffer = buffer->buffers[cpu];
3922
3923 /*
3924 * This must only be called if the event has not been
3925 * committed yet. Thus we can assume that preemption
3926 * is still disabled.
3927 */
3928 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3929
3930 rb_decrement_entry(cpu_buffer, event);
3931 if (rb_try_to_discard(cpu_buffer, event))
3932 goto out;
3933
3934 out:
3935 rb_end_commit(cpu_buffer);
3936
3937 trace_recursive_unlock(cpu_buffer);
3938
3939 preempt_enable_notrace();
3940
3941}
3942EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3943
3944/**
3945 * ring_buffer_write - write data to the buffer without reserving
3946 * @buffer: The ring buffer to write to.
3947 * @length: The length of the data being written (excluding the event header)
3948 * @data: The data to write to the buffer.
3949 *
3950 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3951 * one function. If you already have the data to write to the buffer, it
3952 * may be easier to simply call this function.
3953 *
3954 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3955 * and not the length of the event which would hold the header.
3956 */
3957int ring_buffer_write(struct trace_buffer *buffer,
3958 unsigned long length,
3959 void *data)
3960{
3961 struct ring_buffer_per_cpu *cpu_buffer;
3962 struct ring_buffer_event *event;
3963 void *body;
3964 int ret = -EBUSY;
3965 int cpu;
3966
3967 preempt_disable_notrace();
3968
3969 if (atomic_read(&buffer->record_disabled))
3970 goto out;
3971
3972 cpu = raw_smp_processor_id();
3973
3974 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3975 goto out;
3976
3977 cpu_buffer = buffer->buffers[cpu];
3978
3979 if (atomic_read(&cpu_buffer->record_disabled))
3980 goto out;
3981
3982 if (length > BUF_MAX_DATA_SIZE)
3983 goto out;
3984
3985 if (unlikely(trace_recursive_lock(cpu_buffer)))
3986 goto out;
3987
3988 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3989 if (!event)
3990 goto out_unlock;
3991
3992 body = rb_event_data(event);
3993
3994 memcpy(body, data, length);
3995
3996 rb_commit(cpu_buffer);
3997
3998 rb_wakeups(buffer, cpu_buffer);
3999
4000 ret = 0;
4001
4002 out_unlock:
4003 trace_recursive_unlock(cpu_buffer);
4004
4005 out:
4006 preempt_enable_notrace();
4007
4008 return ret;
4009}
4010EXPORT_SYMBOL_GPL(ring_buffer_write);
4011
4012static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
4013{
4014 struct buffer_page *reader = cpu_buffer->reader_page;
4015 struct buffer_page *head = rb_set_head_page(cpu_buffer);
4016 struct buffer_page *commit = cpu_buffer->commit_page;
4017
4018 /* In case of error, head will be NULL */
4019 if (unlikely(!head))
4020 return true;
4021
4022 /* Reader should exhaust content in reader page */
4023 if (reader->read != rb_page_commit(reader))
4024 return false;
4025
4026 /*
4027 * If writers are committing on the reader page, knowing all
4028 * committed content has been read, the ring buffer is empty.
4029 */
4030 if (commit == reader)
4031 return true;
4032
4033 /*
4034 * If writers are committing on a page other than reader page
4035 * and head page, there should always be content to read.
4036 */
4037 if (commit != head)
4038 return false;
4039
4040 /*
4041 * Writers are committing on the head page, we just need
4042 * to care about there're committed data, and the reader will
4043 * swap reader page with head page when it is to read data.
4044 */
4045 return rb_page_commit(commit) == 0;
4046}
4047
4048/**
4049 * ring_buffer_record_disable - stop all writes into the buffer
4050 * @buffer: The ring buffer to stop writes to.
4051 *
4052 * This prevents all writes to the buffer. Any attempt to write
4053 * to the buffer after this will fail and return NULL.
4054 *
4055 * The caller should call synchronize_rcu() after this.
4056 */
4057void ring_buffer_record_disable(struct trace_buffer *buffer)
4058{
4059 atomic_inc(&buffer->record_disabled);
4060}
4061EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
4062
4063/**
4064 * ring_buffer_record_enable - enable writes to the buffer
4065 * @buffer: The ring buffer to enable writes
4066 *
4067 * Note, multiple disables will need the same number of enables
4068 * to truly enable the writing (much like preempt_disable).
4069 */
4070void ring_buffer_record_enable(struct trace_buffer *buffer)
4071{
4072 atomic_dec(&buffer->record_disabled);
4073}
4074EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4075
4076/**
4077 * ring_buffer_record_off - stop all writes into the buffer
4078 * @buffer: The ring buffer to stop writes to.
4079 *
4080 * This prevents all writes to the buffer. Any attempt to write
4081 * to the buffer after this will fail and return NULL.
4082 *
4083 * This is different than ring_buffer_record_disable() as
4084 * it works like an on/off switch, where as the disable() version
4085 * must be paired with a enable().
4086 */
4087void ring_buffer_record_off(struct trace_buffer *buffer)
4088{
4089 unsigned int rd;
4090 unsigned int new_rd;
4091
4092 do {
4093 rd = atomic_read(&buffer->record_disabled);
4094 new_rd = rd | RB_BUFFER_OFF;
4095 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
4096}
4097EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4098
4099/**
4100 * ring_buffer_record_on - restart writes into the buffer
4101 * @buffer: The ring buffer to start writes to.
4102 *
4103 * This enables all writes to the buffer that was disabled by
4104 * ring_buffer_record_off().
4105 *
4106 * This is different than ring_buffer_record_enable() as
4107 * it works like an on/off switch, where as the enable() version
4108 * must be paired with a disable().
4109 */
4110void ring_buffer_record_on(struct trace_buffer *buffer)
4111{
4112 unsigned int rd;
4113 unsigned int new_rd;
4114
4115 do {
4116 rd = atomic_read(&buffer->record_disabled);
4117 new_rd = rd & ~RB_BUFFER_OFF;
4118 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
4119}
4120EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4121
4122/**
4123 * ring_buffer_record_is_on - return true if the ring buffer can write
4124 * @buffer: The ring buffer to see if write is enabled
4125 *
4126 * Returns true if the ring buffer is in a state that it accepts writes.
4127 */
4128bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4129{
4130 return !atomic_read(&buffer->record_disabled);
4131}
4132
4133/**
4134 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4135 * @buffer: The ring buffer to see if write is set enabled
4136 *
4137 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4138 * Note that this does NOT mean it is in a writable state.
4139 *
4140 * It may return true when the ring buffer has been disabled by
4141 * ring_buffer_record_disable(), as that is a temporary disabling of
4142 * the ring buffer.
4143 */
4144bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4145{
4146 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4147}
4148
4149/**
4150 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4151 * @buffer: The ring buffer to stop writes to.
4152 * @cpu: The CPU buffer to stop
4153 *
4154 * This prevents all writes to the buffer. Any attempt to write
4155 * to the buffer after this will fail and return NULL.
4156 *
4157 * The caller should call synchronize_rcu() after this.
4158 */
4159void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4160{
4161 struct ring_buffer_per_cpu *cpu_buffer;
4162
4163 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4164 return;
4165
4166 cpu_buffer = buffer->buffers[cpu];
4167 atomic_inc(&cpu_buffer->record_disabled);
4168}
4169EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4170
4171/**
4172 * ring_buffer_record_enable_cpu - enable writes to the buffer
4173 * @buffer: The ring buffer to enable writes
4174 * @cpu: The CPU to enable.
4175 *
4176 * Note, multiple disables will need the same number of enables
4177 * to truly enable the writing (much like preempt_disable).
4178 */
4179void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4180{
4181 struct ring_buffer_per_cpu *cpu_buffer;
4182
4183 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4184 return;
4185
4186 cpu_buffer = buffer->buffers[cpu];
4187 atomic_dec(&cpu_buffer->record_disabled);
4188}
4189EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4190
4191/*
4192 * The total entries in the ring buffer is the running counter
4193 * of entries entered into the ring buffer, minus the sum of
4194 * the entries read from the ring buffer and the number of
4195 * entries that were overwritten.
4196 */
4197static inline unsigned long
4198rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4199{
4200 return local_read(&cpu_buffer->entries) -
4201 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4202}
4203
4204/**
4205 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4206 * @buffer: The ring buffer
4207 * @cpu: The per CPU buffer to read from.
4208 */
4209u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4210{
4211 unsigned long flags;
4212 struct ring_buffer_per_cpu *cpu_buffer;
4213 struct buffer_page *bpage;
4214 u64 ret = 0;
4215
4216 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4217 return 0;
4218
4219 cpu_buffer = buffer->buffers[cpu];
4220 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4221 /*
4222 * if the tail is on reader_page, oldest time stamp is on the reader
4223 * page
4224 */
4225 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4226 bpage = cpu_buffer->reader_page;
4227 else
4228 bpage = rb_set_head_page(cpu_buffer);
4229 if (bpage)
4230 ret = bpage->page->time_stamp;
4231 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4232
4233 return ret;
4234}
4235EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4236
4237/**
4238 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
4239 * @buffer: The ring buffer
4240 * @cpu: The per CPU buffer to read from.
4241 */
4242unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4243{
4244 struct ring_buffer_per_cpu *cpu_buffer;
4245 unsigned long ret;
4246
4247 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4248 return 0;
4249
4250 cpu_buffer = buffer->buffers[cpu];
4251 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4252
4253 return ret;
4254}
4255EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4256
4257/**
4258 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4259 * @buffer: The ring buffer
4260 * @cpu: The per CPU buffer to get the entries from.
4261 */
4262unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4263{
4264 struct ring_buffer_per_cpu *cpu_buffer;
4265
4266 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4267 return 0;
4268
4269 cpu_buffer = buffer->buffers[cpu];
4270
4271 return rb_num_of_entries(cpu_buffer);
4272}
4273EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4274
4275/**
4276 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4277 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4278 * @buffer: The ring buffer
4279 * @cpu: The per CPU buffer to get the number of overruns from
4280 */
4281unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4282{
4283 struct ring_buffer_per_cpu *cpu_buffer;
4284 unsigned long ret;
4285
4286 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4287 return 0;
4288
4289 cpu_buffer = buffer->buffers[cpu];
4290 ret = local_read(&cpu_buffer->overrun);
4291
4292 return ret;
4293}
4294EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4295
4296/**
4297 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4298 * commits failing due to the buffer wrapping around while there are uncommitted
4299 * events, such as during an interrupt storm.
4300 * @buffer: The ring buffer
4301 * @cpu: The per CPU buffer to get the number of overruns from
4302 */
4303unsigned long
4304ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4305{
4306 struct ring_buffer_per_cpu *cpu_buffer;
4307 unsigned long ret;
4308
4309 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4310 return 0;
4311
4312 cpu_buffer = buffer->buffers[cpu];
4313 ret = local_read(&cpu_buffer->commit_overrun);
4314
4315 return ret;
4316}
4317EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4318
4319/**
4320 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4321 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4322 * @buffer: The ring buffer
4323 * @cpu: The per CPU buffer to get the number of overruns from
4324 */
4325unsigned long
4326ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4327{
4328 struct ring_buffer_per_cpu *cpu_buffer;
4329 unsigned long ret;
4330
4331 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4332 return 0;
4333
4334 cpu_buffer = buffer->buffers[cpu];
4335 ret = local_read(&cpu_buffer->dropped_events);
4336
4337 return ret;
4338}
4339EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4340
4341/**
4342 * ring_buffer_read_events_cpu - get the number of events successfully read
4343 * @buffer: The ring buffer
4344 * @cpu: The per CPU buffer to get the number of events read
4345 */
4346unsigned long
4347ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4348{
4349 struct ring_buffer_per_cpu *cpu_buffer;
4350
4351 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4352 return 0;
4353
4354 cpu_buffer = buffer->buffers[cpu];
4355 return cpu_buffer->read;
4356}
4357EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4358
4359/**
4360 * ring_buffer_entries - get the number of entries in a buffer
4361 * @buffer: The ring buffer
4362 *
4363 * Returns the total number of entries in the ring buffer
4364 * (all CPU entries)
4365 */
4366unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4367{
4368 struct ring_buffer_per_cpu *cpu_buffer;
4369 unsigned long entries = 0;
4370 int cpu;
4371
4372 /* if you care about this being correct, lock the buffer */
4373 for_each_buffer_cpu(buffer, cpu) {
4374 cpu_buffer = buffer->buffers[cpu];
4375 entries += rb_num_of_entries(cpu_buffer);
4376 }
4377
4378 return entries;
4379}
4380EXPORT_SYMBOL_GPL(ring_buffer_entries);
4381
4382/**
4383 * ring_buffer_overruns - get the number of overruns in buffer
4384 * @buffer: The ring buffer
4385 *
4386 * Returns the total number of overruns in the ring buffer
4387 * (all CPU entries)
4388 */
4389unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4390{
4391 struct ring_buffer_per_cpu *cpu_buffer;
4392 unsigned long overruns = 0;
4393 int cpu;
4394
4395 /* if you care about this being correct, lock the buffer */
4396 for_each_buffer_cpu(buffer, cpu) {
4397 cpu_buffer = buffer->buffers[cpu];
4398 overruns += local_read(&cpu_buffer->overrun);
4399 }
4400
4401 return overruns;
4402}
4403EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4404
4405static void rb_iter_reset(struct ring_buffer_iter *iter)
4406{
4407 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4408
4409 /* Iterator usage is expected to have record disabled */
4410 iter->head_page = cpu_buffer->reader_page;
4411 iter->head = cpu_buffer->reader_page->read;
4412 iter->next_event = iter->head;
4413
4414 iter->cache_reader_page = iter->head_page;
4415 iter->cache_read = cpu_buffer->read;
4416
4417 if (iter->head) {
4418 iter->read_stamp = cpu_buffer->read_stamp;
4419 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4420 } else {
4421 iter->read_stamp = iter->head_page->page->time_stamp;
4422 iter->page_stamp = iter->read_stamp;
4423 }
4424}
4425
4426/**
4427 * ring_buffer_iter_reset - reset an iterator
4428 * @iter: The iterator to reset
4429 *
4430 * Resets the iterator, so that it will start from the beginning
4431 * again.
4432 */
4433void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4434{
4435 struct ring_buffer_per_cpu *cpu_buffer;
4436 unsigned long flags;
4437
4438 if (!iter)
4439 return;
4440
4441 cpu_buffer = iter->cpu_buffer;
4442
4443 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4444 rb_iter_reset(iter);
4445 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4446}
4447EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4448
4449/**
4450 * ring_buffer_iter_empty - check if an iterator has no more to read
4451 * @iter: The iterator to check
4452 */
4453int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4454{
4455 struct ring_buffer_per_cpu *cpu_buffer;
4456 struct buffer_page *reader;
4457 struct buffer_page *head_page;
4458 struct buffer_page *commit_page;
4459 struct buffer_page *curr_commit_page;
4460 unsigned commit;
4461 u64 curr_commit_ts;
4462 u64 commit_ts;
4463
4464 cpu_buffer = iter->cpu_buffer;
4465 reader = cpu_buffer->reader_page;
4466 head_page = cpu_buffer->head_page;
4467 commit_page = cpu_buffer->commit_page;
4468 commit_ts = commit_page->page->time_stamp;
4469
4470 /*
4471 * When the writer goes across pages, it issues a cmpxchg which
4472 * is a mb(), which will synchronize with the rmb here.
4473 * (see rb_tail_page_update())
4474 */
4475 smp_rmb();
4476 commit = rb_page_commit(commit_page);
4477 /* We want to make sure that the commit page doesn't change */
4478 smp_rmb();
4479
4480 /* Make sure commit page didn't change */
4481 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4482 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4483
4484 /* If the commit page changed, then there's more data */
4485 if (curr_commit_page != commit_page ||
4486 curr_commit_ts != commit_ts)
4487 return 0;
4488
4489 /* Still racy, as it may return a false positive, but that's OK */
4490 return ((iter->head_page == commit_page && iter->head >= commit) ||
4491 (iter->head_page == reader && commit_page == head_page &&
4492 head_page->read == commit &&
4493 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4494}
4495EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4496
4497static void
4498rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4499 struct ring_buffer_event *event)
4500{
4501 u64 delta;
4502
4503 switch (event->type_len) {
4504 case RINGBUF_TYPE_PADDING:
4505 return;
4506
4507 case RINGBUF_TYPE_TIME_EXTEND:
4508 delta = rb_event_time_stamp(event);
4509 cpu_buffer->read_stamp += delta;
4510 return;
4511
4512 case RINGBUF_TYPE_TIME_STAMP:
4513 delta = rb_event_time_stamp(event);
4514 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
4515 cpu_buffer->read_stamp = delta;
4516 return;
4517
4518 case RINGBUF_TYPE_DATA:
4519 cpu_buffer->read_stamp += event->time_delta;
4520 return;
4521
4522 default:
4523 RB_WARN_ON(cpu_buffer, 1);
4524 }
4525 return;
4526}
4527
4528static void
4529rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4530 struct ring_buffer_event *event)
4531{
4532 u64 delta;
4533
4534 switch (event->type_len) {
4535 case RINGBUF_TYPE_PADDING:
4536 return;
4537
4538 case RINGBUF_TYPE_TIME_EXTEND:
4539 delta = rb_event_time_stamp(event);
4540 iter->read_stamp += delta;
4541 return;
4542
4543 case RINGBUF_TYPE_TIME_STAMP:
4544 delta = rb_event_time_stamp(event);
4545 delta = rb_fix_abs_ts(delta, iter->read_stamp);
4546 iter->read_stamp = delta;
4547 return;
4548
4549 case RINGBUF_TYPE_DATA:
4550 iter->read_stamp += event->time_delta;
4551 return;
4552
4553 default:
4554 RB_WARN_ON(iter->cpu_buffer, 1);
4555 }
4556 return;
4557}
4558
4559static struct buffer_page *
4560rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4561{
4562 struct buffer_page *reader = NULL;
4563 unsigned long overwrite;
4564 unsigned long flags;
4565 int nr_loops = 0;
4566 int ret;
4567
4568 local_irq_save(flags);
4569 arch_spin_lock(&cpu_buffer->lock);
4570
4571 again:
4572 /*
4573 * This should normally only loop twice. But because the
4574 * start of the reader inserts an empty page, it causes
4575 * a case where we will loop three times. There should be no
4576 * reason to loop four times (that I know of).
4577 */
4578 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4579 reader = NULL;
4580 goto out;
4581 }
4582
4583 reader = cpu_buffer->reader_page;
4584
4585 /* If there's more to read, return this page */
4586 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4587 goto out;
4588
4589 /* Never should we have an index greater than the size */
4590 if (RB_WARN_ON(cpu_buffer,
4591 cpu_buffer->reader_page->read > rb_page_size(reader)))
4592 goto out;
4593
4594 /* check if we caught up to the tail */
4595 reader = NULL;
4596 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4597 goto out;
4598
4599 /* Don't bother swapping if the ring buffer is empty */
4600 if (rb_num_of_entries(cpu_buffer) == 0)
4601 goto out;
4602
4603 /*
4604 * Reset the reader page to size zero.
4605 */
4606 local_set(&cpu_buffer->reader_page->write, 0);
4607 local_set(&cpu_buffer->reader_page->entries, 0);
4608 local_set(&cpu_buffer->reader_page->page->commit, 0);
4609 cpu_buffer->reader_page->real_end = 0;
4610
4611 spin:
4612 /*
4613 * Splice the empty reader page into the list around the head.
4614 */
4615 reader = rb_set_head_page(cpu_buffer);
4616 if (!reader)
4617 goto out;
4618 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4619 cpu_buffer->reader_page->list.prev = reader->list.prev;
4620
4621 /*
4622 * cpu_buffer->pages just needs to point to the buffer, it
4623 * has no specific buffer page to point to. Lets move it out
4624 * of our way so we don't accidentally swap it.
4625 */
4626 cpu_buffer->pages = reader->list.prev;
4627
4628 /* The reader page will be pointing to the new head */
4629 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4630
4631 /*
4632 * We want to make sure we read the overruns after we set up our
4633 * pointers to the next object. The writer side does a
4634 * cmpxchg to cross pages which acts as the mb on the writer
4635 * side. Note, the reader will constantly fail the swap
4636 * while the writer is updating the pointers, so this
4637 * guarantees that the overwrite recorded here is the one we
4638 * want to compare with the last_overrun.
4639 */
4640 smp_mb();
4641 overwrite = local_read(&(cpu_buffer->overrun));
4642
4643 /*
4644 * Here's the tricky part.
4645 *
4646 * We need to move the pointer past the header page.
4647 * But we can only do that if a writer is not currently
4648 * moving it. The page before the header page has the
4649 * flag bit '1' set if it is pointing to the page we want.
4650 * but if the writer is in the process of moving it
4651 * than it will be '2' or already moved '0'.
4652 */
4653
4654 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4655
4656 /*
4657 * If we did not convert it, then we must try again.
4658 */
4659 if (!ret)
4660 goto spin;
4661
4662 /*
4663 * Yay! We succeeded in replacing the page.
4664 *
4665 * Now make the new head point back to the reader page.
4666 */
4667 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4668 rb_inc_page(&cpu_buffer->head_page);
4669
4670 local_inc(&cpu_buffer->pages_read);
4671
4672 /* Finally update the reader page to the new head */
4673 cpu_buffer->reader_page = reader;
4674 cpu_buffer->reader_page->read = 0;
4675
4676 if (overwrite != cpu_buffer->last_overrun) {
4677 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4678 cpu_buffer->last_overrun = overwrite;
4679 }
4680
4681 goto again;
4682
4683 out:
4684 /* Update the read_stamp on the first event */
4685 if (reader && reader->read == 0)
4686 cpu_buffer->read_stamp = reader->page->time_stamp;
4687
4688 arch_spin_unlock(&cpu_buffer->lock);
4689 local_irq_restore(flags);
4690
4691 /*
4692 * The writer has preempt disable, wait for it. But not forever
4693 * Although, 1 second is pretty much "forever"
4694 */
4695#define USECS_WAIT 1000000
4696 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4697 /* If the write is past the end of page, a writer is still updating it */
4698 if (likely(!reader || rb_page_write(reader) <= BUF_PAGE_SIZE))
4699 break;
4700
4701 udelay(1);
4702
4703 /* Get the latest version of the reader write value */
4704 smp_rmb();
4705 }
4706
4707 /* The writer is not moving forward? Something is wrong */
4708 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4709 reader = NULL;
4710
4711 /*
4712 * Make sure we see any padding after the write update
4713 * (see rb_reset_tail())
4714 */
4715 smp_rmb();
4716
4717
4718 return reader;
4719}
4720
4721static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4722{
4723 struct ring_buffer_event *event;
4724 struct buffer_page *reader;
4725 unsigned length;
4726
4727 reader = rb_get_reader_page(cpu_buffer);
4728
4729 /* This function should not be called when buffer is empty */
4730 if (RB_WARN_ON(cpu_buffer, !reader))
4731 return;
4732
4733 event = rb_reader_event(cpu_buffer);
4734
4735 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4736 cpu_buffer->read++;
4737
4738 rb_update_read_stamp(cpu_buffer, event);
4739
4740 length = rb_event_length(event);
4741 cpu_buffer->reader_page->read += length;
4742}
4743
4744static void rb_advance_iter(struct ring_buffer_iter *iter)
4745{
4746 struct ring_buffer_per_cpu *cpu_buffer;
4747
4748 cpu_buffer = iter->cpu_buffer;
4749
4750 /* If head == next_event then we need to jump to the next event */
4751 if (iter->head == iter->next_event) {
4752 /* If the event gets overwritten again, there's nothing to do */
4753 if (rb_iter_head_event(iter) == NULL)
4754 return;
4755 }
4756
4757 iter->head = iter->next_event;
4758
4759 /*
4760 * Check if we are at the end of the buffer.
4761 */
4762 if (iter->next_event >= rb_page_size(iter->head_page)) {
4763 /* discarded commits can make the page empty */
4764 if (iter->head_page == cpu_buffer->commit_page)
4765 return;
4766 rb_inc_iter(iter);
4767 return;
4768 }
4769
4770 rb_update_iter_read_stamp(iter, iter->event);
4771}
4772
4773static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4774{
4775 return cpu_buffer->lost_events;
4776}
4777
4778static struct ring_buffer_event *
4779rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4780 unsigned long *lost_events)
4781{
4782 struct ring_buffer_event *event;
4783 struct buffer_page *reader;
4784 int nr_loops = 0;
4785
4786 if (ts)
4787 *ts = 0;
4788 again:
4789 /*
4790 * We repeat when a time extend is encountered.
4791 * Since the time extend is always attached to a data event,
4792 * we should never loop more than once.
4793 * (We never hit the following condition more than twice).
4794 */
4795 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4796 return NULL;
4797
4798 reader = rb_get_reader_page(cpu_buffer);
4799 if (!reader)
4800 return NULL;
4801
4802 event = rb_reader_event(cpu_buffer);
4803
4804 switch (event->type_len) {
4805 case RINGBUF_TYPE_PADDING:
4806 if (rb_null_event(event))
4807 RB_WARN_ON(cpu_buffer, 1);
4808 /*
4809 * Because the writer could be discarding every
4810 * event it creates (which would probably be bad)
4811 * if we were to go back to "again" then we may never
4812 * catch up, and will trigger the warn on, or lock
4813 * the box. Return the padding, and we will release
4814 * the current locks, and try again.
4815 */
4816 return event;
4817
4818 case RINGBUF_TYPE_TIME_EXTEND:
4819 /* Internal data, OK to advance */
4820 rb_advance_reader(cpu_buffer);
4821 goto again;
4822
4823 case RINGBUF_TYPE_TIME_STAMP:
4824 if (ts) {
4825 *ts = rb_event_time_stamp(event);
4826 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
4827 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4828 cpu_buffer->cpu, ts);
4829 }
4830 /* Internal data, OK to advance */
4831 rb_advance_reader(cpu_buffer);
4832 goto again;
4833
4834 case RINGBUF_TYPE_DATA:
4835 if (ts && !(*ts)) {
4836 *ts = cpu_buffer->read_stamp + event->time_delta;
4837 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4838 cpu_buffer->cpu, ts);
4839 }
4840 if (lost_events)
4841 *lost_events = rb_lost_events(cpu_buffer);
4842 return event;
4843
4844 default:
4845 RB_WARN_ON(cpu_buffer, 1);
4846 }
4847
4848 return NULL;
4849}
4850EXPORT_SYMBOL_GPL(ring_buffer_peek);
4851
4852static struct ring_buffer_event *
4853rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4854{
4855 struct trace_buffer *buffer;
4856 struct ring_buffer_per_cpu *cpu_buffer;
4857 struct ring_buffer_event *event;
4858 int nr_loops = 0;
4859
4860 if (ts)
4861 *ts = 0;
4862
4863 cpu_buffer = iter->cpu_buffer;
4864 buffer = cpu_buffer->buffer;
4865
4866 /*
4867 * Check if someone performed a consuming read to
4868 * the buffer. A consuming read invalidates the iterator
4869 * and we need to reset the iterator in this case.
4870 */
4871 if (unlikely(iter->cache_read != cpu_buffer->read ||
4872 iter->cache_reader_page != cpu_buffer->reader_page))
4873 rb_iter_reset(iter);
4874
4875 again:
4876 if (ring_buffer_iter_empty(iter))
4877 return NULL;
4878
4879 /*
4880 * As the writer can mess with what the iterator is trying
4881 * to read, just give up if we fail to get an event after
4882 * three tries. The iterator is not as reliable when reading
4883 * the ring buffer with an active write as the consumer is.
4884 * Do not warn if the three failures is reached.
4885 */
4886 if (++nr_loops > 3)
4887 return NULL;
4888
4889 if (rb_per_cpu_empty(cpu_buffer))
4890 return NULL;
4891
4892 if (iter->head >= rb_page_size(iter->head_page)) {
4893 rb_inc_iter(iter);
4894 goto again;
4895 }
4896
4897 event = rb_iter_head_event(iter);
4898 if (!event)
4899 goto again;
4900
4901 switch (event->type_len) {
4902 case RINGBUF_TYPE_PADDING:
4903 if (rb_null_event(event)) {
4904 rb_inc_iter(iter);
4905 goto again;
4906 }
4907 rb_advance_iter(iter);
4908 return event;
4909
4910 case RINGBUF_TYPE_TIME_EXTEND:
4911 /* Internal data, OK to advance */
4912 rb_advance_iter(iter);
4913 goto again;
4914
4915 case RINGBUF_TYPE_TIME_STAMP:
4916 if (ts) {
4917 *ts = rb_event_time_stamp(event);
4918 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
4919 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4920 cpu_buffer->cpu, ts);
4921 }
4922 /* Internal data, OK to advance */
4923 rb_advance_iter(iter);
4924 goto again;
4925
4926 case RINGBUF_TYPE_DATA:
4927 if (ts && !(*ts)) {
4928 *ts = iter->read_stamp + event->time_delta;
4929 ring_buffer_normalize_time_stamp(buffer,
4930 cpu_buffer->cpu, ts);
4931 }
4932 return event;
4933
4934 default:
4935 RB_WARN_ON(cpu_buffer, 1);
4936 }
4937
4938 return NULL;
4939}
4940EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4941
4942static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4943{
4944 if (likely(!in_nmi())) {
4945 raw_spin_lock(&cpu_buffer->reader_lock);
4946 return true;
4947 }
4948
4949 /*
4950 * If an NMI die dumps out the content of the ring buffer
4951 * trylock must be used to prevent a deadlock if the NMI
4952 * preempted a task that holds the ring buffer locks. If
4953 * we get the lock then all is fine, if not, then continue
4954 * to do the read, but this can corrupt the ring buffer,
4955 * so it must be permanently disabled from future writes.
4956 * Reading from NMI is a oneshot deal.
4957 */
4958 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4959 return true;
4960
4961 /* Continue without locking, but disable the ring buffer */
4962 atomic_inc(&cpu_buffer->record_disabled);
4963 return false;
4964}
4965
4966static inline void
4967rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4968{
4969 if (likely(locked))
4970 raw_spin_unlock(&cpu_buffer->reader_lock);
4971 return;
4972}
4973
4974/**
4975 * ring_buffer_peek - peek at the next event to be read
4976 * @buffer: The ring buffer to read
4977 * @cpu: The cpu to peak at
4978 * @ts: The timestamp counter of this event.
4979 * @lost_events: a variable to store if events were lost (may be NULL)
4980 *
4981 * This will return the event that will be read next, but does
4982 * not consume the data.
4983 */
4984struct ring_buffer_event *
4985ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4986 unsigned long *lost_events)
4987{
4988 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4989 struct ring_buffer_event *event;
4990 unsigned long flags;
4991 bool dolock;
4992
4993 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4994 return NULL;
4995
4996 again:
4997 local_irq_save(flags);
4998 dolock = rb_reader_lock(cpu_buffer);
4999 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5000 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5001 rb_advance_reader(cpu_buffer);
5002 rb_reader_unlock(cpu_buffer, dolock);
5003 local_irq_restore(flags);
5004
5005 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5006 goto again;
5007
5008 return event;
5009}
5010
5011/** ring_buffer_iter_dropped - report if there are dropped events
5012 * @iter: The ring buffer iterator
5013 *
5014 * Returns true if there was dropped events since the last peek.
5015 */
5016bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
5017{
5018 bool ret = iter->missed_events != 0;
5019
5020 iter->missed_events = 0;
5021 return ret;
5022}
5023EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
5024
5025/**
5026 * ring_buffer_iter_peek - peek at the next event to be read
5027 * @iter: The ring buffer iterator
5028 * @ts: The timestamp counter of this event.
5029 *
5030 * This will return the event that will be read next, but does
5031 * not increment the iterator.
5032 */
5033struct ring_buffer_event *
5034ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5035{
5036 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5037 struct ring_buffer_event *event;
5038 unsigned long flags;
5039
5040 again:
5041 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5042 event = rb_iter_peek(iter, ts);
5043 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5044
5045 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5046 goto again;
5047
5048 return event;
5049}
5050
5051/**
5052 * ring_buffer_consume - return an event and consume it
5053 * @buffer: The ring buffer to get the next event from
5054 * @cpu: the cpu to read the buffer from
5055 * @ts: a variable to store the timestamp (may be NULL)
5056 * @lost_events: a variable to store if events were lost (may be NULL)
5057 *
5058 * Returns the next event in the ring buffer, and that event is consumed.
5059 * Meaning, that sequential reads will keep returning a different event,
5060 * and eventually empty the ring buffer if the producer is slower.
5061 */
5062struct ring_buffer_event *
5063ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5064 unsigned long *lost_events)
5065{
5066 struct ring_buffer_per_cpu *cpu_buffer;
5067 struct ring_buffer_event *event = NULL;
5068 unsigned long flags;
5069 bool dolock;
5070
5071 again:
5072 /* might be called in atomic */
5073 preempt_disable();
5074
5075 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5076 goto out;
5077
5078 cpu_buffer = buffer->buffers[cpu];
5079 local_irq_save(flags);
5080 dolock = rb_reader_lock(cpu_buffer);
5081
5082 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5083 if (event) {
5084 cpu_buffer->lost_events = 0;
5085 rb_advance_reader(cpu_buffer);
5086 }
5087
5088 rb_reader_unlock(cpu_buffer, dolock);
5089 local_irq_restore(flags);
5090
5091 out:
5092 preempt_enable();
5093
5094 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5095 goto again;
5096
5097 return event;
5098}
5099EXPORT_SYMBOL_GPL(ring_buffer_consume);
5100
5101/**
5102 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5103 * @buffer: The ring buffer to read from
5104 * @cpu: The cpu buffer to iterate over
5105 * @flags: gfp flags to use for memory allocation
5106 *
5107 * This performs the initial preparations necessary to iterate
5108 * through the buffer. Memory is allocated, buffer recording
5109 * is disabled, and the iterator pointer is returned to the caller.
5110 *
5111 * Disabling buffer recording prevents the reading from being
5112 * corrupted. This is not a consuming read, so a producer is not
5113 * expected.
5114 *
5115 * After a sequence of ring_buffer_read_prepare calls, the user is
5116 * expected to make at least one call to ring_buffer_read_prepare_sync.
5117 * Afterwards, ring_buffer_read_start is invoked to get things going
5118 * for real.
5119 *
5120 * This overall must be paired with ring_buffer_read_finish.
5121 */
5122struct ring_buffer_iter *
5123ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5124{
5125 struct ring_buffer_per_cpu *cpu_buffer;
5126 struct ring_buffer_iter *iter;
5127
5128 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5129 return NULL;
5130
5131 iter = kzalloc(sizeof(*iter), flags);
5132 if (!iter)
5133 return NULL;
5134
5135 iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
5136 if (!iter->event) {
5137 kfree(iter);
5138 return NULL;
5139 }
5140
5141 cpu_buffer = buffer->buffers[cpu];
5142
5143 iter->cpu_buffer = cpu_buffer;
5144
5145 atomic_inc(&cpu_buffer->resize_disabled);
5146
5147 return iter;
5148}
5149EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5150
5151/**
5152 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5153 *
5154 * All previously invoked ring_buffer_read_prepare calls to prepare
5155 * iterators will be synchronized. Afterwards, read_buffer_read_start
5156 * calls on those iterators are allowed.
5157 */
5158void
5159ring_buffer_read_prepare_sync(void)
5160{
5161 synchronize_rcu();
5162}
5163EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5164
5165/**
5166 * ring_buffer_read_start - start a non consuming read of the buffer
5167 * @iter: The iterator returned by ring_buffer_read_prepare
5168 *
5169 * This finalizes the startup of an iteration through the buffer.
5170 * The iterator comes from a call to ring_buffer_read_prepare and
5171 * an intervening ring_buffer_read_prepare_sync must have been
5172 * performed.
5173 *
5174 * Must be paired with ring_buffer_read_finish.
5175 */
5176void
5177ring_buffer_read_start(struct ring_buffer_iter *iter)
5178{
5179 struct ring_buffer_per_cpu *cpu_buffer;
5180 unsigned long flags;
5181
5182 if (!iter)
5183 return;
5184
5185 cpu_buffer = iter->cpu_buffer;
5186
5187 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5188 arch_spin_lock(&cpu_buffer->lock);
5189 rb_iter_reset(iter);
5190 arch_spin_unlock(&cpu_buffer->lock);
5191 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5192}
5193EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5194
5195/**
5196 * ring_buffer_read_finish - finish reading the iterator of the buffer
5197 * @iter: The iterator retrieved by ring_buffer_start
5198 *
5199 * This re-enables the recording to the buffer, and frees the
5200 * iterator.
5201 */
5202void
5203ring_buffer_read_finish(struct ring_buffer_iter *iter)
5204{
5205 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5206 unsigned long flags;
5207
5208 /*
5209 * Ring buffer is disabled from recording, here's a good place
5210 * to check the integrity of the ring buffer.
5211 * Must prevent readers from trying to read, as the check
5212 * clears the HEAD page and readers require it.
5213 */
5214 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5215 rb_check_pages(cpu_buffer);
5216 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5217
5218 atomic_dec(&cpu_buffer->resize_disabled);
5219 kfree(iter->event);
5220 kfree(iter);
5221}
5222EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5223
5224/**
5225 * ring_buffer_iter_advance - advance the iterator to the next location
5226 * @iter: The ring buffer iterator
5227 *
5228 * Move the location of the iterator such that the next read will
5229 * be the next location of the iterator.
5230 */
5231void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5232{
5233 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5234 unsigned long flags;
5235
5236 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5237
5238 rb_advance_iter(iter);
5239
5240 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5241}
5242EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5243
5244/**
5245 * ring_buffer_size - return the size of the ring buffer (in bytes)
5246 * @buffer: The ring buffer.
5247 * @cpu: The CPU to get ring buffer size from.
5248 */
5249unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5250{
5251 /*
5252 * Earlier, this method returned
5253 * BUF_PAGE_SIZE * buffer->nr_pages
5254 * Since the nr_pages field is now removed, we have converted this to
5255 * return the per cpu buffer value.
5256 */
5257 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5258 return 0;
5259
5260 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
5261}
5262EXPORT_SYMBOL_GPL(ring_buffer_size);
5263
5264static void
5265rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5266{
5267 rb_head_page_deactivate(cpu_buffer);
5268
5269 cpu_buffer->head_page
5270 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5271 local_set(&cpu_buffer->head_page->write, 0);
5272 local_set(&cpu_buffer->head_page->entries, 0);
5273 local_set(&cpu_buffer->head_page->page->commit, 0);
5274
5275 cpu_buffer->head_page->read = 0;
5276
5277 cpu_buffer->tail_page = cpu_buffer->head_page;
5278 cpu_buffer->commit_page = cpu_buffer->head_page;
5279
5280 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5281 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5282 local_set(&cpu_buffer->reader_page->write, 0);
5283 local_set(&cpu_buffer->reader_page->entries, 0);
5284 local_set(&cpu_buffer->reader_page->page->commit, 0);
5285 cpu_buffer->reader_page->read = 0;
5286
5287 local_set(&cpu_buffer->entries_bytes, 0);
5288 local_set(&cpu_buffer->overrun, 0);
5289 local_set(&cpu_buffer->commit_overrun, 0);
5290 local_set(&cpu_buffer->dropped_events, 0);
5291 local_set(&cpu_buffer->entries, 0);
5292 local_set(&cpu_buffer->committing, 0);
5293 local_set(&cpu_buffer->commits, 0);
5294 local_set(&cpu_buffer->pages_touched, 0);
5295 local_set(&cpu_buffer->pages_lost, 0);
5296 local_set(&cpu_buffer->pages_read, 0);
5297 cpu_buffer->last_pages_touch = 0;
5298 cpu_buffer->shortest_full = 0;
5299 cpu_buffer->read = 0;
5300 cpu_buffer->read_bytes = 0;
5301
5302 rb_time_set(&cpu_buffer->write_stamp, 0);
5303 rb_time_set(&cpu_buffer->before_stamp, 0);
5304
5305 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5306
5307 cpu_buffer->lost_events = 0;
5308 cpu_buffer->last_overrun = 0;
5309
5310 rb_head_page_activate(cpu_buffer);
5311}
5312
5313/* Must have disabled the cpu buffer then done a synchronize_rcu */
5314static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5315{
5316 unsigned long flags;
5317
5318 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5319
5320 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5321 goto out;
5322
5323 arch_spin_lock(&cpu_buffer->lock);
5324
5325 rb_reset_cpu(cpu_buffer);
5326
5327 arch_spin_unlock(&cpu_buffer->lock);
5328
5329 out:
5330 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5331}
5332
5333/**
5334 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5335 * @buffer: The ring buffer to reset a per cpu buffer of
5336 * @cpu: The CPU buffer to be reset
5337 */
5338void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5339{
5340 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5341
5342 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5343 return;
5344
5345 /* prevent another thread from changing buffer sizes */
5346 mutex_lock(&buffer->mutex);
5347
5348 atomic_inc(&cpu_buffer->resize_disabled);
5349 atomic_inc(&cpu_buffer->record_disabled);
5350
5351 /* Make sure all commits have finished */
5352 synchronize_rcu();
5353
5354 reset_disabled_cpu_buffer(cpu_buffer);
5355
5356 atomic_dec(&cpu_buffer->record_disabled);
5357 atomic_dec(&cpu_buffer->resize_disabled);
5358
5359 mutex_unlock(&buffer->mutex);
5360}
5361EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5362
5363/**
5364 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5365 * @buffer: The ring buffer to reset a per cpu buffer of
5366 * @cpu: The CPU buffer to be reset
5367 */
5368void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5369{
5370 struct ring_buffer_per_cpu *cpu_buffer;
5371 int cpu;
5372
5373 /* prevent another thread from changing buffer sizes */
5374 mutex_lock(&buffer->mutex);
5375
5376 for_each_online_buffer_cpu(buffer, cpu) {
5377 cpu_buffer = buffer->buffers[cpu];
5378
5379 atomic_inc(&cpu_buffer->resize_disabled);
5380 atomic_inc(&cpu_buffer->record_disabled);
5381 }
5382
5383 /* Make sure all commits have finished */
5384 synchronize_rcu();
5385
5386 for_each_online_buffer_cpu(buffer, cpu) {
5387 cpu_buffer = buffer->buffers[cpu];
5388
5389 reset_disabled_cpu_buffer(cpu_buffer);
5390
5391 atomic_dec(&cpu_buffer->record_disabled);
5392 atomic_dec(&cpu_buffer->resize_disabled);
5393 }
5394
5395 mutex_unlock(&buffer->mutex);
5396}
5397
5398/**
5399 * ring_buffer_reset - reset a ring buffer
5400 * @buffer: The ring buffer to reset all cpu buffers
5401 */
5402void ring_buffer_reset(struct trace_buffer *buffer)
5403{
5404 struct ring_buffer_per_cpu *cpu_buffer;
5405 int cpu;
5406
5407 /* prevent another thread from changing buffer sizes */
5408 mutex_lock(&buffer->mutex);
5409
5410 for_each_buffer_cpu(buffer, cpu) {
5411 cpu_buffer = buffer->buffers[cpu];
5412
5413 atomic_inc(&cpu_buffer->resize_disabled);
5414 atomic_inc(&cpu_buffer->record_disabled);
5415 }
5416
5417 /* Make sure all commits have finished */
5418 synchronize_rcu();
5419
5420 for_each_buffer_cpu(buffer, cpu) {
5421 cpu_buffer = buffer->buffers[cpu];
5422
5423 reset_disabled_cpu_buffer(cpu_buffer);
5424
5425 atomic_dec(&cpu_buffer->record_disabled);
5426 atomic_dec(&cpu_buffer->resize_disabled);
5427 }
5428
5429 mutex_unlock(&buffer->mutex);
5430}
5431EXPORT_SYMBOL_GPL(ring_buffer_reset);
5432
5433/**
5434 * ring_buffer_empty - is the ring buffer empty?
5435 * @buffer: The ring buffer to test
5436 */
5437bool ring_buffer_empty(struct trace_buffer *buffer)
5438{
5439 struct ring_buffer_per_cpu *cpu_buffer;
5440 unsigned long flags;
5441 bool dolock;
5442 int cpu;
5443 int ret;
5444
5445 /* yes this is racy, but if you don't like the race, lock the buffer */
5446 for_each_buffer_cpu(buffer, cpu) {
5447 cpu_buffer = buffer->buffers[cpu];
5448 local_irq_save(flags);
5449 dolock = rb_reader_lock(cpu_buffer);
5450 ret = rb_per_cpu_empty(cpu_buffer);
5451 rb_reader_unlock(cpu_buffer, dolock);
5452 local_irq_restore(flags);
5453
5454 if (!ret)
5455 return false;
5456 }
5457
5458 return true;
5459}
5460EXPORT_SYMBOL_GPL(ring_buffer_empty);
5461
5462/**
5463 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5464 * @buffer: The ring buffer
5465 * @cpu: The CPU buffer to test
5466 */
5467bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5468{
5469 struct ring_buffer_per_cpu *cpu_buffer;
5470 unsigned long flags;
5471 bool dolock;
5472 int ret;
5473
5474 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5475 return true;
5476
5477 cpu_buffer = buffer->buffers[cpu];
5478 local_irq_save(flags);
5479 dolock = rb_reader_lock(cpu_buffer);
5480 ret = rb_per_cpu_empty(cpu_buffer);
5481 rb_reader_unlock(cpu_buffer, dolock);
5482 local_irq_restore(flags);
5483
5484 return ret;
5485}
5486EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5487
5488#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5489/**
5490 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5491 * @buffer_a: One buffer to swap with
5492 * @buffer_b: The other buffer to swap with
5493 * @cpu: the CPU of the buffers to swap
5494 *
5495 * This function is useful for tracers that want to take a "snapshot"
5496 * of a CPU buffer and has another back up buffer lying around.
5497 * it is expected that the tracer handles the cpu buffer not being
5498 * used at the moment.
5499 */
5500int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5501 struct trace_buffer *buffer_b, int cpu)
5502{
5503 struct ring_buffer_per_cpu *cpu_buffer_a;
5504 struct ring_buffer_per_cpu *cpu_buffer_b;
5505 int ret = -EINVAL;
5506
5507 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5508 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5509 goto out;
5510
5511 cpu_buffer_a = buffer_a->buffers[cpu];
5512 cpu_buffer_b = buffer_b->buffers[cpu];
5513
5514 /* At least make sure the two buffers are somewhat the same */
5515 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5516 goto out;
5517
5518 ret = -EAGAIN;
5519
5520 if (atomic_read(&buffer_a->record_disabled))
5521 goto out;
5522
5523 if (atomic_read(&buffer_b->record_disabled))
5524 goto out;
5525
5526 if (atomic_read(&cpu_buffer_a->record_disabled))
5527 goto out;
5528
5529 if (atomic_read(&cpu_buffer_b->record_disabled))
5530 goto out;
5531
5532 /*
5533 * We can't do a synchronize_rcu here because this
5534 * function can be called in atomic context.
5535 * Normally this will be called from the same CPU as cpu.
5536 * If not it's up to the caller to protect this.
5537 */
5538 atomic_inc(&cpu_buffer_a->record_disabled);
5539 atomic_inc(&cpu_buffer_b->record_disabled);
5540
5541 ret = -EBUSY;
5542 if (local_read(&cpu_buffer_a->committing))
5543 goto out_dec;
5544 if (local_read(&cpu_buffer_b->committing))
5545 goto out_dec;
5546
5547 buffer_a->buffers[cpu] = cpu_buffer_b;
5548 buffer_b->buffers[cpu] = cpu_buffer_a;
5549
5550 cpu_buffer_b->buffer = buffer_a;
5551 cpu_buffer_a->buffer = buffer_b;
5552
5553 ret = 0;
5554
5555out_dec:
5556 atomic_dec(&cpu_buffer_a->record_disabled);
5557 atomic_dec(&cpu_buffer_b->record_disabled);
5558out:
5559 return ret;
5560}
5561EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5562#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5563
5564/**
5565 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5566 * @buffer: the buffer to allocate for.
5567 * @cpu: the cpu buffer to allocate.
5568 *
5569 * This function is used in conjunction with ring_buffer_read_page.
5570 * When reading a full page from the ring buffer, these functions
5571 * can be used to speed up the process. The calling function should
5572 * allocate a few pages first with this function. Then when it
5573 * needs to get pages from the ring buffer, it passes the result
5574 * of this function into ring_buffer_read_page, which will swap
5575 * the page that was allocated, with the read page of the buffer.
5576 *
5577 * Returns:
5578 * The page allocated, or ERR_PTR
5579 */
5580void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5581{
5582 struct ring_buffer_per_cpu *cpu_buffer;
5583 struct buffer_data_page *bpage = NULL;
5584 unsigned long flags;
5585 struct page *page;
5586
5587 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5588 return ERR_PTR(-ENODEV);
5589
5590 cpu_buffer = buffer->buffers[cpu];
5591 local_irq_save(flags);
5592 arch_spin_lock(&cpu_buffer->lock);
5593
5594 if (cpu_buffer->free_page) {
5595 bpage = cpu_buffer->free_page;
5596 cpu_buffer->free_page = NULL;
5597 }
5598
5599 arch_spin_unlock(&cpu_buffer->lock);
5600 local_irq_restore(flags);
5601
5602 if (bpage)
5603 goto out;
5604
5605 page = alloc_pages_node(cpu_to_node(cpu),
5606 GFP_KERNEL | __GFP_NORETRY, 0);
5607 if (!page)
5608 return ERR_PTR(-ENOMEM);
5609
5610 bpage = page_address(page);
5611
5612 out:
5613 rb_init_page(bpage);
5614
5615 return bpage;
5616}
5617EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5618
5619/**
5620 * ring_buffer_free_read_page - free an allocated read page
5621 * @buffer: the buffer the page was allocate for
5622 * @cpu: the cpu buffer the page came from
5623 * @data: the page to free
5624 *
5625 * Free a page allocated from ring_buffer_alloc_read_page.
5626 */
5627void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5628{
5629 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5630 struct buffer_data_page *bpage = data;
5631 struct page *page = virt_to_page(bpage);
5632 unsigned long flags;
5633
5634 /* If the page is still in use someplace else, we can't reuse it */
5635 if (page_ref_count(page) > 1)
5636 goto out;
5637
5638 local_irq_save(flags);
5639 arch_spin_lock(&cpu_buffer->lock);
5640
5641 if (!cpu_buffer->free_page) {
5642 cpu_buffer->free_page = bpage;
5643 bpage = NULL;
5644 }
5645
5646 arch_spin_unlock(&cpu_buffer->lock);
5647 local_irq_restore(flags);
5648
5649 out:
5650 free_page((unsigned long)bpage);
5651}
5652EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5653
5654/**
5655 * ring_buffer_read_page - extract a page from the ring buffer
5656 * @buffer: buffer to extract from
5657 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5658 * @len: amount to extract
5659 * @cpu: the cpu of the buffer to extract
5660 * @full: should the extraction only happen when the page is full.
5661 *
5662 * This function will pull out a page from the ring buffer and consume it.
5663 * @data_page must be the address of the variable that was returned
5664 * from ring_buffer_alloc_read_page. This is because the page might be used
5665 * to swap with a page in the ring buffer.
5666 *
5667 * for example:
5668 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5669 * if (IS_ERR(rpage))
5670 * return PTR_ERR(rpage);
5671 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5672 * if (ret >= 0)
5673 * process_page(rpage, ret);
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 void **data_page, size_t len, int cpu, int full)
5689{
5690 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5691 struct ring_buffer_event *event;
5692 struct buffer_data_page *bpage;
5693 struct buffer_page *reader;
5694 unsigned long missed_events;
5695 unsigned long flags;
5696 unsigned int commit;
5697 unsigned int read;
5698 u64 save_timestamp;
5699 int ret = -1;
5700
5701 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5702 goto out;
5703
5704 /*
5705 * If len is not big enough to hold the page header, then
5706 * we can not copy anything.
5707 */
5708 if (len <= BUF_PAGE_HDR_SIZE)
5709 goto out;
5710
5711 len -= BUF_PAGE_HDR_SIZE;
5712
5713 if (!data_page)
5714 goto out;
5715
5716 bpage = *data_page;
5717 if (!bpage)
5718 goto out;
5719
5720 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5721
5722 reader = rb_get_reader_page(cpu_buffer);
5723 if (!reader)
5724 goto out_unlock;
5725
5726 event = rb_reader_event(cpu_buffer);
5727
5728 read = reader->read;
5729 commit = rb_page_commit(reader);
5730
5731 /* Check if any events were dropped */
5732 missed_events = cpu_buffer->lost_events;
5733
5734 /*
5735 * If this page has been partially read or
5736 * if len is not big enough to read the rest of the page or
5737 * a writer is still on the page, then
5738 * we must copy the data from the page to the buffer.
5739 * Otherwise, we can simply swap the page with the one passed in.
5740 */
5741 if (read || (len < (commit - read)) ||
5742 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5743 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5744 unsigned int rpos = read;
5745 unsigned int pos = 0;
5746 unsigned int size;
5747
5748 /*
5749 * If a full page is expected, this can still be returned
5750 * if there's been a previous partial read and the
5751 * rest of the page can be read and the commit page is off
5752 * the reader page.
5753 */
5754 if (full &&
5755 (!read || (len < (commit - read)) ||
5756 cpu_buffer->reader_page == cpu_buffer->commit_page))
5757 goto out_unlock;
5758
5759 if (len > (commit - read))
5760 len = (commit - read);
5761
5762 /* Always keep the time extend and data together */
5763 size = rb_event_ts_length(event);
5764
5765 if (len < size)
5766 goto out_unlock;
5767
5768 /* save the current timestamp, since the user will need it */
5769 save_timestamp = cpu_buffer->read_stamp;
5770
5771 /* Need to copy one event at a time */
5772 do {
5773 /* We need the size of one event, because
5774 * rb_advance_reader only advances by one event,
5775 * whereas rb_event_ts_length may include the size of
5776 * one or two events.
5777 * We have already ensured there's enough space if this
5778 * is a time extend. */
5779 size = rb_event_length(event);
5780 memcpy(bpage->data + pos, rpage->data + rpos, size);
5781
5782 len -= size;
5783
5784 rb_advance_reader(cpu_buffer);
5785 rpos = reader->read;
5786 pos += size;
5787
5788 if (rpos >= commit)
5789 break;
5790
5791 event = rb_reader_event(cpu_buffer);
5792 /* Always keep the time extend and data together */
5793 size = rb_event_ts_length(event);
5794 } while (len >= size);
5795
5796 /* update bpage */
5797 local_set(&bpage->commit, pos);
5798 bpage->time_stamp = save_timestamp;
5799
5800 /* we copied everything to the beginning */
5801 read = 0;
5802 } else {
5803 /* update the entry counter */
5804 cpu_buffer->read += rb_page_entries(reader);
5805 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5806
5807 /* swap the pages */
5808 rb_init_page(bpage);
5809 bpage = reader->page;
5810 reader->page = *data_page;
5811 local_set(&reader->write, 0);
5812 local_set(&reader->entries, 0);
5813 reader->read = 0;
5814 *data_page = bpage;
5815
5816 /*
5817 * Use the real_end for the data size,
5818 * This gives us a chance to store the lost events
5819 * on the page.
5820 */
5821 if (reader->real_end)
5822 local_set(&bpage->commit, reader->real_end);
5823 }
5824 ret = read;
5825
5826 cpu_buffer->lost_events = 0;
5827
5828 commit = local_read(&bpage->commit);
5829 /*
5830 * Set a flag in the commit field if we lost events
5831 */
5832 if (missed_events) {
5833 /* If there is room at the end of the page to save the
5834 * missed events, then record it there.
5835 */
5836 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5837 memcpy(&bpage->data[commit], &missed_events,
5838 sizeof(missed_events));
5839 local_add(RB_MISSED_STORED, &bpage->commit);
5840 commit += sizeof(missed_events);
5841 }
5842 local_add(RB_MISSED_EVENTS, &bpage->commit);
5843 }
5844
5845 /*
5846 * This page may be off to user land. Zero it out here.
5847 */
5848 if (commit < BUF_PAGE_SIZE)
5849 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5850
5851 out_unlock:
5852 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5853
5854 out:
5855 return ret;
5856}
5857EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5858
5859/*
5860 * We only allocate new buffers, never free them if the CPU goes down.
5861 * If we were to free the buffer, then the user would lose any trace that was in
5862 * the buffer.
5863 */
5864int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5865{
5866 struct trace_buffer *buffer;
5867 long nr_pages_same;
5868 int cpu_i;
5869 unsigned long nr_pages;
5870
5871 buffer = container_of(node, struct trace_buffer, node);
5872 if (cpumask_test_cpu(cpu, buffer->cpumask))
5873 return 0;
5874
5875 nr_pages = 0;
5876 nr_pages_same = 1;
5877 /* check if all cpu sizes are same */
5878 for_each_buffer_cpu(buffer, cpu_i) {
5879 /* fill in the size from first enabled cpu */
5880 if (nr_pages == 0)
5881 nr_pages = buffer->buffers[cpu_i]->nr_pages;
5882 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5883 nr_pages_same = 0;
5884 break;
5885 }
5886 }
5887 /* allocate minimum pages, user can later expand it */
5888 if (!nr_pages_same)
5889 nr_pages = 2;
5890 buffer->buffers[cpu] =
5891 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5892 if (!buffer->buffers[cpu]) {
5893 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5894 cpu);
5895 return -ENOMEM;
5896 }
5897 smp_wmb();
5898 cpumask_set_cpu(cpu, buffer->cpumask);
5899 return 0;
5900}
5901
5902#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5903/*
5904 * This is a basic integrity check of the ring buffer.
5905 * Late in the boot cycle this test will run when configured in.
5906 * It will kick off a thread per CPU that will go into a loop
5907 * writing to the per cpu ring buffer various sizes of data.
5908 * Some of the data will be large items, some small.
5909 *
5910 * Another thread is created that goes into a spin, sending out
5911 * IPIs to the other CPUs to also write into the ring buffer.
5912 * this is to test the nesting ability of the buffer.
5913 *
5914 * Basic stats are recorded and reported. If something in the
5915 * ring buffer should happen that's not expected, a big warning
5916 * is displayed and all ring buffers are disabled.
5917 */
5918static struct task_struct *rb_threads[NR_CPUS] __initdata;
5919
5920struct rb_test_data {
5921 struct trace_buffer *buffer;
5922 unsigned long events;
5923 unsigned long bytes_written;
5924 unsigned long bytes_alloc;
5925 unsigned long bytes_dropped;
5926 unsigned long events_nested;
5927 unsigned long bytes_written_nested;
5928 unsigned long bytes_alloc_nested;
5929 unsigned long bytes_dropped_nested;
5930 int min_size_nested;
5931 int max_size_nested;
5932 int max_size;
5933 int min_size;
5934 int cpu;
5935 int cnt;
5936};
5937
5938static struct rb_test_data rb_data[NR_CPUS] __initdata;
5939
5940/* 1 meg per cpu */
5941#define RB_TEST_BUFFER_SIZE 1048576
5942
5943static char rb_string[] __initdata =
5944 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5945 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5946 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5947
5948static bool rb_test_started __initdata;
5949
5950struct rb_item {
5951 int size;
5952 char str[];
5953};
5954
5955static __init int rb_write_something(struct rb_test_data *data, bool nested)
5956{
5957 struct ring_buffer_event *event;
5958 struct rb_item *item;
5959 bool started;
5960 int event_len;
5961 int size;
5962 int len;
5963 int cnt;
5964
5965 /* Have nested writes different that what is written */
5966 cnt = data->cnt + (nested ? 27 : 0);
5967
5968 /* Multiply cnt by ~e, to make some unique increment */
5969 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5970
5971 len = size + sizeof(struct rb_item);
5972
5973 started = rb_test_started;
5974 /* read rb_test_started before checking buffer enabled */
5975 smp_rmb();
5976
5977 event = ring_buffer_lock_reserve(data->buffer, len);
5978 if (!event) {
5979 /* Ignore dropped events before test starts. */
5980 if (started) {
5981 if (nested)
5982 data->bytes_dropped += len;
5983 else
5984 data->bytes_dropped_nested += len;
5985 }
5986 return len;
5987 }
5988
5989 event_len = ring_buffer_event_length(event);
5990
5991 if (RB_WARN_ON(data->buffer, event_len < len))
5992 goto out;
5993
5994 item = ring_buffer_event_data(event);
5995 item->size = size;
5996 memcpy(item->str, rb_string, size);
5997
5998 if (nested) {
5999 data->bytes_alloc_nested += event_len;
6000 data->bytes_written_nested += len;
6001 data->events_nested++;
6002 if (!data->min_size_nested || len < data->min_size_nested)
6003 data->min_size_nested = len;
6004 if (len > data->max_size_nested)
6005 data->max_size_nested = len;
6006 } else {
6007 data->bytes_alloc += event_len;
6008 data->bytes_written += len;
6009 data->events++;
6010 if (!data->min_size || len < data->min_size)
6011 data->max_size = len;
6012 if (len > data->max_size)
6013 data->max_size = len;
6014 }
6015
6016 out:
6017 ring_buffer_unlock_commit(data->buffer);
6018
6019 return 0;
6020}
6021
6022static __init int rb_test(void *arg)
6023{
6024 struct rb_test_data *data = arg;
6025
6026 while (!kthread_should_stop()) {
6027 rb_write_something(data, false);
6028 data->cnt++;
6029
6030 set_current_state(TASK_INTERRUPTIBLE);
6031 /* Now sleep between a min of 100-300us and a max of 1ms */
6032 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
6033 }
6034
6035 return 0;
6036}
6037
6038static __init void rb_ipi(void *ignore)
6039{
6040 struct rb_test_data *data;
6041 int cpu = smp_processor_id();
6042
6043 data = &rb_data[cpu];
6044 rb_write_something(data, true);
6045}
6046
6047static __init int rb_hammer_test(void *arg)
6048{
6049 while (!kthread_should_stop()) {
6050
6051 /* Send an IPI to all cpus to write data! */
6052 smp_call_function(rb_ipi, NULL, 1);
6053 /* No sleep, but for non preempt, let others run */
6054 schedule();
6055 }
6056
6057 return 0;
6058}
6059
6060static __init int test_ringbuffer(void)
6061{
6062 struct task_struct *rb_hammer;
6063 struct trace_buffer *buffer;
6064 int cpu;
6065 int ret = 0;
6066
6067 if (security_locked_down(LOCKDOWN_TRACEFS)) {
6068 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6069 return 0;
6070 }
6071
6072 pr_info("Running ring buffer tests...\n");
6073
6074 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6075 if (WARN_ON(!buffer))
6076 return 0;
6077
6078 /* Disable buffer so that threads can't write to it yet */
6079 ring_buffer_record_off(buffer);
6080
6081 for_each_online_cpu(cpu) {
6082 rb_data[cpu].buffer = buffer;
6083 rb_data[cpu].cpu = cpu;
6084 rb_data[cpu].cnt = cpu;
6085 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
6086 cpu, "rbtester/%u");
6087 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6088 pr_cont("FAILED\n");
6089 ret = PTR_ERR(rb_threads[cpu]);
6090 goto out_free;
6091 }
6092 }
6093
6094 /* Now create the rb hammer! */
6095 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6096 if (WARN_ON(IS_ERR(rb_hammer))) {
6097 pr_cont("FAILED\n");
6098 ret = PTR_ERR(rb_hammer);
6099 goto out_free;
6100 }
6101
6102 ring_buffer_record_on(buffer);
6103 /*
6104 * Show buffer is enabled before setting rb_test_started.
6105 * Yes there's a small race window where events could be
6106 * dropped and the thread wont catch it. But when a ring
6107 * buffer gets enabled, there will always be some kind of
6108 * delay before other CPUs see it. Thus, we don't care about
6109 * those dropped events. We care about events dropped after
6110 * the threads see that the buffer is active.
6111 */
6112 smp_wmb();
6113 rb_test_started = true;
6114
6115 set_current_state(TASK_INTERRUPTIBLE);
6116 /* Just run for 10 seconds */;
6117 schedule_timeout(10 * HZ);
6118
6119 kthread_stop(rb_hammer);
6120
6121 out_free:
6122 for_each_online_cpu(cpu) {
6123 if (!rb_threads[cpu])
6124 break;
6125 kthread_stop(rb_threads[cpu]);
6126 }
6127 if (ret) {
6128 ring_buffer_free(buffer);
6129 return ret;
6130 }
6131
6132 /* Report! */
6133 pr_info("finished\n");
6134 for_each_online_cpu(cpu) {
6135 struct ring_buffer_event *event;
6136 struct rb_test_data *data = &rb_data[cpu];
6137 struct rb_item *item;
6138 unsigned long total_events;
6139 unsigned long total_dropped;
6140 unsigned long total_written;
6141 unsigned long total_alloc;
6142 unsigned long total_read = 0;
6143 unsigned long total_size = 0;
6144 unsigned long total_len = 0;
6145 unsigned long total_lost = 0;
6146 unsigned long lost;
6147 int big_event_size;
6148 int small_event_size;
6149
6150 ret = -1;
6151
6152 total_events = data->events + data->events_nested;
6153 total_written = data->bytes_written + data->bytes_written_nested;
6154 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6155 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6156
6157 big_event_size = data->max_size + data->max_size_nested;
6158 small_event_size = data->min_size + data->min_size_nested;
6159
6160 pr_info("CPU %d:\n", cpu);
6161 pr_info(" events: %ld\n", total_events);
6162 pr_info(" dropped bytes: %ld\n", total_dropped);
6163 pr_info(" alloced bytes: %ld\n", total_alloc);
6164 pr_info(" written bytes: %ld\n", total_written);
6165 pr_info(" biggest event: %d\n", big_event_size);
6166 pr_info(" smallest event: %d\n", small_event_size);
6167
6168 if (RB_WARN_ON(buffer, total_dropped))
6169 break;
6170
6171 ret = 0;
6172
6173 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6174 total_lost += lost;
6175 item = ring_buffer_event_data(event);
6176 total_len += ring_buffer_event_length(event);
6177 total_size += item->size + sizeof(struct rb_item);
6178 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
6179 pr_info("FAILED!\n");
6180 pr_info("buffer had: %.*s\n", item->size, item->str);
6181 pr_info("expected: %.*s\n", item->size, rb_string);
6182 RB_WARN_ON(buffer, 1);
6183 ret = -1;
6184 break;
6185 }
6186 total_read++;
6187 }
6188 if (ret)
6189 break;
6190
6191 ret = -1;
6192
6193 pr_info(" read events: %ld\n", total_read);
6194 pr_info(" lost events: %ld\n", total_lost);
6195 pr_info(" total events: %ld\n", total_lost + total_read);
6196 pr_info(" recorded len bytes: %ld\n", total_len);
6197 pr_info(" recorded size bytes: %ld\n", total_size);
6198 if (total_lost) {
6199 pr_info(" With dropped events, record len and size may not match\n"
6200 " alloced and written from above\n");
6201 } else {
6202 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6203 total_size != total_written))
6204 break;
6205 }
6206 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6207 break;
6208
6209 ret = 0;
6210 }
6211 if (!ret)
6212 pr_info("Ring buffer PASSED!\n");
6213
6214 ring_buffer_free(buffer);
6215 return 0;
6216}
6217
6218late_initcall(test_ringbuffer);
6219#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/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 */