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1/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/ftrace_event.h>
7#include <linux/ring_buffer.h>
8#include <linux/trace_clock.h>
9#include <linux/trace_seq.h>
10#include <linux/spinlock.h>
11#include <linux/irq_work.h>
12#include <linux/debugfs.h>
13#include <linux/uaccess.h>
14#include <linux/hardirq.h>
15#include <linux/kthread.h> /* for self test */
16#include <linux/kmemcheck.h>
17#include <linux/module.h>
18#include <linux/percpu.h>
19#include <linux/mutex.h>
20#include <linux/delay.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/hash.h>
24#include <linux/list.h>
25#include <linux/cpu.h>
26#include <linux/fs.h>
27
28#include <asm/local.h>
29
30static void update_pages_handler(struct work_struct *work);
31
32/*
33 * The ring buffer header is special. We must manually up keep it.
34 */
35int ring_buffer_print_entry_header(struct trace_seq *s)
36{
37 int ret;
38
39 ret = trace_seq_puts(s, "# compressed entry header\n");
40 ret = trace_seq_puts(s, "\ttype_len : 5 bits\n");
41 ret = trace_seq_puts(s, "\ttime_delta : 27 bits\n");
42 ret = trace_seq_puts(s, "\tarray : 32 bits\n");
43 ret = trace_seq_putc(s, '\n');
44 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
45 RINGBUF_TYPE_PADDING);
46 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
47 RINGBUF_TYPE_TIME_EXTEND);
48 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
49 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
50
51 return ret;
52}
53
54/*
55 * The ring buffer is made up of a list of pages. A separate list of pages is
56 * allocated for each CPU. A writer may only write to a buffer that is
57 * associated with the CPU it is currently executing on. A reader may read
58 * from any per cpu buffer.
59 *
60 * The reader is special. For each per cpu buffer, the reader has its own
61 * reader page. When a reader has read the entire reader page, this reader
62 * page is swapped with another page in the ring buffer.
63 *
64 * Now, as long as the writer is off the reader page, the reader can do what
65 * ever it wants with that page. The writer will never write to that page
66 * again (as long as it is out of the ring buffer).
67 *
68 * Here's some silly ASCII art.
69 *
70 * +------+
71 * |reader| RING BUFFER
72 * |page |
73 * +------+ +---+ +---+ +---+
74 * | |-->| |-->| |
75 * +---+ +---+ +---+
76 * ^ |
77 * | |
78 * +---------------+
79 *
80 *
81 * +------+
82 * |reader| RING BUFFER
83 * |page |------------------v
84 * +------+ +---+ +---+ +---+
85 * | |-->| |-->| |
86 * +---+ +---+ +---+
87 * ^ |
88 * | |
89 * +---------------+
90 *
91 *
92 * +------+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
96 * ^ | |-->| |-->| |
97 * | +---+ +---+ +---+
98 * | |
99 * | |
100 * +------------------------------+
101 *
102 *
103 * +------+
104 * |buffer| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
107 * ^ | | | |-->| |
108 * | New +---+ +---+ +---+
109 * | Reader------^ |
110 * | page |
111 * +------------------------------+
112 *
113 *
114 * After we make this swap, the reader can hand this page off to the splice
115 * code and be done with it. It can even allocate a new page if it needs to
116 * and swap that into the ring buffer.
117 *
118 * We will be using cmpxchg soon to make all this lockless.
119 *
120 */
121
122/*
123 * A fast way to enable or disable all ring buffers is to
124 * call tracing_on or tracing_off. Turning off the ring buffers
125 * prevents all ring buffers from being recorded to.
126 * Turning this switch on, makes it OK to write to the
127 * ring buffer, if the ring buffer is enabled itself.
128 *
129 * There's three layers that must be on in order to write
130 * to the ring buffer.
131 *
132 * 1) This global flag must be set.
133 * 2) The ring buffer must be enabled for recording.
134 * 3) The per cpu buffer must be enabled for recording.
135 *
136 * In case of an anomaly, this global flag has a bit set that
137 * will permantly disable all ring buffers.
138 */
139
140/*
141 * Global flag to disable all recording to ring buffers
142 * This has two bits: ON, DISABLED
143 *
144 * ON DISABLED
145 * ---- ----------
146 * 0 0 : ring buffers are off
147 * 1 0 : ring buffers are on
148 * X 1 : ring buffers are permanently disabled
149 */
150
151enum {
152 RB_BUFFERS_ON_BIT = 0,
153 RB_BUFFERS_DISABLED_BIT = 1,
154};
155
156enum {
157 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
158 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
159};
160
161static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
162
163/* Used for individual buffers (after the counter) */
164#define RB_BUFFER_OFF (1 << 20)
165
166#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
167
168/**
169 * tracing_off_permanent - permanently disable ring buffers
170 *
171 * This function, once called, will disable all ring buffers
172 * permanently.
173 */
174void tracing_off_permanent(void)
175{
176 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
177}
178
179#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
180#define RB_ALIGNMENT 4U
181#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
182#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
183
184#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
185# define RB_FORCE_8BYTE_ALIGNMENT 0
186# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
187#else
188# define RB_FORCE_8BYTE_ALIGNMENT 1
189# define RB_ARCH_ALIGNMENT 8U
190#endif
191
192#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
193
194/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
195#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
196
197enum {
198 RB_LEN_TIME_EXTEND = 8,
199 RB_LEN_TIME_STAMP = 16,
200};
201
202#define skip_time_extend(event) \
203 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
204
205static inline int rb_null_event(struct ring_buffer_event *event)
206{
207 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
208}
209
210static void rb_event_set_padding(struct ring_buffer_event *event)
211{
212 /* padding has a NULL time_delta */
213 event->type_len = RINGBUF_TYPE_PADDING;
214 event->time_delta = 0;
215}
216
217static unsigned
218rb_event_data_length(struct ring_buffer_event *event)
219{
220 unsigned length;
221
222 if (event->type_len)
223 length = event->type_len * RB_ALIGNMENT;
224 else
225 length = event->array[0];
226 return length + RB_EVNT_HDR_SIZE;
227}
228
229/*
230 * Return the length of the given event. Will return
231 * the length of the time extend if the event is a
232 * time extend.
233 */
234static inline unsigned
235rb_event_length(struct ring_buffer_event *event)
236{
237 switch (event->type_len) {
238 case RINGBUF_TYPE_PADDING:
239 if (rb_null_event(event))
240 /* undefined */
241 return -1;
242 return event->array[0] + RB_EVNT_HDR_SIZE;
243
244 case RINGBUF_TYPE_TIME_EXTEND:
245 return RB_LEN_TIME_EXTEND;
246
247 case RINGBUF_TYPE_TIME_STAMP:
248 return RB_LEN_TIME_STAMP;
249
250 case RINGBUF_TYPE_DATA:
251 return rb_event_data_length(event);
252 default:
253 BUG();
254 }
255 /* not hit */
256 return 0;
257}
258
259/*
260 * Return total length of time extend and data,
261 * or just the event length for all other events.
262 */
263static inline unsigned
264rb_event_ts_length(struct ring_buffer_event *event)
265{
266 unsigned len = 0;
267
268 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
269 /* time extends include the data event after it */
270 len = RB_LEN_TIME_EXTEND;
271 event = skip_time_extend(event);
272 }
273 return len + rb_event_length(event);
274}
275
276/**
277 * ring_buffer_event_length - return the length of the event
278 * @event: the event to get the length of
279 *
280 * Returns the size of the data load of a data event.
281 * If the event is something other than a data event, it
282 * returns the size of the event itself. With the exception
283 * of a TIME EXTEND, where it still returns the size of the
284 * data load of the data event after it.
285 */
286unsigned ring_buffer_event_length(struct ring_buffer_event *event)
287{
288 unsigned length;
289
290 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
291 event = skip_time_extend(event);
292
293 length = rb_event_length(event);
294 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
295 return length;
296 length -= RB_EVNT_HDR_SIZE;
297 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
298 length -= sizeof(event->array[0]);
299 return length;
300}
301EXPORT_SYMBOL_GPL(ring_buffer_event_length);
302
303/* inline for ring buffer fast paths */
304static void *
305rb_event_data(struct ring_buffer_event *event)
306{
307 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
308 event = skip_time_extend(event);
309 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
310 /* If length is in len field, then array[0] has the data */
311 if (event->type_len)
312 return (void *)&event->array[0];
313 /* Otherwise length is in array[0] and array[1] has the data */
314 return (void *)&event->array[1];
315}
316
317/**
318 * ring_buffer_event_data - return the data of the event
319 * @event: the event to get the data from
320 */
321void *ring_buffer_event_data(struct ring_buffer_event *event)
322{
323 return rb_event_data(event);
324}
325EXPORT_SYMBOL_GPL(ring_buffer_event_data);
326
327#define for_each_buffer_cpu(buffer, cpu) \
328 for_each_cpu(cpu, buffer->cpumask)
329
330#define TS_SHIFT 27
331#define TS_MASK ((1ULL << TS_SHIFT) - 1)
332#define TS_DELTA_TEST (~TS_MASK)
333
334/* Flag when events were overwritten */
335#define RB_MISSED_EVENTS (1 << 31)
336/* Missed count stored at end */
337#define RB_MISSED_STORED (1 << 30)
338
339struct buffer_data_page {
340 u64 time_stamp; /* page time stamp */
341 local_t commit; /* write committed index */
342 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
343};
344
345/*
346 * Note, the buffer_page list must be first. The buffer pages
347 * are allocated in cache lines, which means that each buffer
348 * page will be at the beginning of a cache line, and thus
349 * the least significant bits will be zero. We use this to
350 * add flags in the list struct pointers, to make the ring buffer
351 * lockless.
352 */
353struct buffer_page {
354 struct list_head list; /* list of buffer pages */
355 local_t write; /* index for next write */
356 unsigned read; /* index for next read */
357 local_t entries; /* entries on this page */
358 unsigned long real_end; /* real end of data */
359 struct buffer_data_page *page; /* Actual data page */
360};
361
362/*
363 * The buffer page counters, write and entries, must be reset
364 * atomically when crossing page boundaries. To synchronize this
365 * update, two counters are inserted into the number. One is
366 * the actual counter for the write position or count on the page.
367 *
368 * The other is a counter of updaters. Before an update happens
369 * the update partition of the counter is incremented. This will
370 * allow the updater to update the counter atomically.
371 *
372 * The counter is 20 bits, and the state data is 12.
373 */
374#define RB_WRITE_MASK 0xfffff
375#define RB_WRITE_INTCNT (1 << 20)
376
377static void rb_init_page(struct buffer_data_page *bpage)
378{
379 local_set(&bpage->commit, 0);
380}
381
382/**
383 * ring_buffer_page_len - the size of data on the page.
384 * @page: The page to read
385 *
386 * Returns the amount of data on the page, including buffer page header.
387 */
388size_t ring_buffer_page_len(void *page)
389{
390 return local_read(&((struct buffer_data_page *)page)->commit)
391 + BUF_PAGE_HDR_SIZE;
392}
393
394/*
395 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
396 * this issue out.
397 */
398static void free_buffer_page(struct buffer_page *bpage)
399{
400 free_page((unsigned long)bpage->page);
401 kfree(bpage);
402}
403
404/*
405 * We need to fit the time_stamp delta into 27 bits.
406 */
407static inline int test_time_stamp(u64 delta)
408{
409 if (delta & TS_DELTA_TEST)
410 return 1;
411 return 0;
412}
413
414#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
415
416/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
417#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
418
419int ring_buffer_print_page_header(struct trace_seq *s)
420{
421 struct buffer_data_page field;
422 int ret;
423
424 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
425 "offset:0;\tsize:%u;\tsigned:%u;\n",
426 (unsigned int)sizeof(field.time_stamp),
427 (unsigned int)is_signed_type(u64));
428
429 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
430 "offset:%u;\tsize:%u;\tsigned:%u;\n",
431 (unsigned int)offsetof(typeof(field), commit),
432 (unsigned int)sizeof(field.commit),
433 (unsigned int)is_signed_type(long));
434
435 ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
436 "offset:%u;\tsize:%u;\tsigned:%u;\n",
437 (unsigned int)offsetof(typeof(field), commit),
438 1,
439 (unsigned int)is_signed_type(long));
440
441 ret = trace_seq_printf(s, "\tfield: char data;\t"
442 "offset:%u;\tsize:%u;\tsigned:%u;\n",
443 (unsigned int)offsetof(typeof(field), data),
444 (unsigned int)BUF_PAGE_SIZE,
445 (unsigned int)is_signed_type(char));
446
447 return ret;
448}
449
450struct rb_irq_work {
451 struct irq_work work;
452 wait_queue_head_t waiters;
453 bool waiters_pending;
454};
455
456/*
457 * head_page == tail_page && head == tail then buffer is empty.
458 */
459struct ring_buffer_per_cpu {
460 int cpu;
461 atomic_t record_disabled;
462 struct ring_buffer *buffer;
463 raw_spinlock_t reader_lock; /* serialize readers */
464 arch_spinlock_t lock;
465 struct lock_class_key lock_key;
466 unsigned int nr_pages;
467 struct list_head *pages;
468 struct buffer_page *head_page; /* read from head */
469 struct buffer_page *tail_page; /* write to tail */
470 struct buffer_page *commit_page; /* committed pages */
471 struct buffer_page *reader_page;
472 unsigned long lost_events;
473 unsigned long last_overrun;
474 local_t entries_bytes;
475 local_t entries;
476 local_t overrun;
477 local_t commit_overrun;
478 local_t dropped_events;
479 local_t committing;
480 local_t commits;
481 unsigned long read;
482 unsigned long read_bytes;
483 u64 write_stamp;
484 u64 read_stamp;
485 /* ring buffer pages to update, > 0 to add, < 0 to remove */
486 int nr_pages_to_update;
487 struct list_head new_pages; /* new pages to add */
488 struct work_struct update_pages_work;
489 struct completion update_done;
490
491 struct rb_irq_work irq_work;
492};
493
494struct ring_buffer {
495 unsigned flags;
496 int cpus;
497 atomic_t record_disabled;
498 atomic_t resize_disabled;
499 cpumask_var_t cpumask;
500
501 struct lock_class_key *reader_lock_key;
502
503 struct mutex mutex;
504
505 struct ring_buffer_per_cpu **buffers;
506
507#ifdef CONFIG_HOTPLUG_CPU
508 struct notifier_block cpu_notify;
509#endif
510 u64 (*clock)(void);
511
512 struct rb_irq_work irq_work;
513};
514
515struct ring_buffer_iter {
516 struct ring_buffer_per_cpu *cpu_buffer;
517 unsigned long head;
518 struct buffer_page *head_page;
519 struct buffer_page *cache_reader_page;
520 unsigned long cache_read;
521 u64 read_stamp;
522};
523
524/*
525 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
526 *
527 * Schedules a delayed work to wake up any task that is blocked on the
528 * ring buffer waiters queue.
529 */
530static void rb_wake_up_waiters(struct irq_work *work)
531{
532 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
533
534 wake_up_all(&rbwork->waiters);
535}
536
537/**
538 * ring_buffer_wait - wait for input to the ring buffer
539 * @buffer: buffer to wait on
540 * @cpu: the cpu buffer to wait on
541 *
542 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
543 * as data is added to any of the @buffer's cpu buffers. Otherwise
544 * it will wait for data to be added to a specific cpu buffer.
545 */
546void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
547{
548 struct ring_buffer_per_cpu *cpu_buffer;
549 DEFINE_WAIT(wait);
550 struct rb_irq_work *work;
551
552 /*
553 * Depending on what the caller is waiting for, either any
554 * data in any cpu buffer, or a specific buffer, put the
555 * caller on the appropriate wait queue.
556 */
557 if (cpu == RING_BUFFER_ALL_CPUS)
558 work = &buffer->irq_work;
559 else {
560 cpu_buffer = buffer->buffers[cpu];
561 work = &cpu_buffer->irq_work;
562 }
563
564
565 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
566
567 /*
568 * The events can happen in critical sections where
569 * checking a work queue can cause deadlocks.
570 * After adding a task to the queue, this flag is set
571 * only to notify events to try to wake up the queue
572 * using irq_work.
573 *
574 * We don't clear it even if the buffer is no longer
575 * empty. The flag only causes the next event to run
576 * irq_work to do the work queue wake up. The worse
577 * that can happen if we race with !trace_empty() is that
578 * an event will cause an irq_work to try to wake up
579 * an empty queue.
580 *
581 * There's no reason to protect this flag either, as
582 * the work queue and irq_work logic will do the necessary
583 * synchronization for the wake ups. The only thing
584 * that is necessary is that the wake up happens after
585 * a task has been queued. It's OK for spurious wake ups.
586 */
587 work->waiters_pending = true;
588
589 if ((cpu == RING_BUFFER_ALL_CPUS && ring_buffer_empty(buffer)) ||
590 (cpu != RING_BUFFER_ALL_CPUS && ring_buffer_empty_cpu(buffer, cpu)))
591 schedule();
592
593 finish_wait(&work->waiters, &wait);
594}
595
596/**
597 * ring_buffer_poll_wait - poll on buffer input
598 * @buffer: buffer to wait on
599 * @cpu: the cpu buffer to wait on
600 * @filp: the file descriptor
601 * @poll_table: The poll descriptor
602 *
603 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
604 * as data is added to any of the @buffer's cpu buffers. Otherwise
605 * it will wait for data to be added to a specific cpu buffer.
606 *
607 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
608 * zero otherwise.
609 */
610int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
611 struct file *filp, poll_table *poll_table)
612{
613 struct ring_buffer_per_cpu *cpu_buffer;
614 struct rb_irq_work *work;
615
616 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
617 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
618 return POLLIN | POLLRDNORM;
619
620 if (cpu == RING_BUFFER_ALL_CPUS)
621 work = &buffer->irq_work;
622 else {
623 if (!cpumask_test_cpu(cpu, buffer->cpumask))
624 return -EINVAL;
625
626 cpu_buffer = buffer->buffers[cpu];
627 work = &cpu_buffer->irq_work;
628 }
629
630 work->waiters_pending = true;
631 poll_wait(filp, &work->waiters, poll_table);
632
633 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
634 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
635 return POLLIN | POLLRDNORM;
636 return 0;
637}
638
639/* buffer may be either ring_buffer or ring_buffer_per_cpu */
640#define RB_WARN_ON(b, cond) \
641 ({ \
642 int _____ret = unlikely(cond); \
643 if (_____ret) { \
644 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
645 struct ring_buffer_per_cpu *__b = \
646 (void *)b; \
647 atomic_inc(&__b->buffer->record_disabled); \
648 } else \
649 atomic_inc(&b->record_disabled); \
650 WARN_ON(1); \
651 } \
652 _____ret; \
653 })
654
655/* Up this if you want to test the TIME_EXTENTS and normalization */
656#define DEBUG_SHIFT 0
657
658static inline u64 rb_time_stamp(struct ring_buffer *buffer)
659{
660 /* shift to debug/test normalization and TIME_EXTENTS */
661 return buffer->clock() << DEBUG_SHIFT;
662}
663
664u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
665{
666 u64 time;
667
668 preempt_disable_notrace();
669 time = rb_time_stamp(buffer);
670 preempt_enable_no_resched_notrace();
671
672 return time;
673}
674EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
675
676void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
677 int cpu, u64 *ts)
678{
679 /* Just stupid testing the normalize function and deltas */
680 *ts >>= DEBUG_SHIFT;
681}
682EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
683
684/*
685 * Making the ring buffer lockless makes things tricky.
686 * Although writes only happen on the CPU that they are on,
687 * and they only need to worry about interrupts. Reads can
688 * happen on any CPU.
689 *
690 * The reader page is always off the ring buffer, but when the
691 * reader finishes with a page, it needs to swap its page with
692 * a new one from the buffer. The reader needs to take from
693 * the head (writes go to the tail). But if a writer is in overwrite
694 * mode and wraps, it must push the head page forward.
695 *
696 * Here lies the problem.
697 *
698 * The reader must be careful to replace only the head page, and
699 * not another one. As described at the top of the file in the
700 * ASCII art, the reader sets its old page to point to the next
701 * page after head. It then sets the page after head to point to
702 * the old reader page. But if the writer moves the head page
703 * during this operation, the reader could end up with the tail.
704 *
705 * We use cmpxchg to help prevent this race. We also do something
706 * special with the page before head. We set the LSB to 1.
707 *
708 * When the writer must push the page forward, it will clear the
709 * bit that points to the head page, move the head, and then set
710 * the bit that points to the new head page.
711 *
712 * We also don't want an interrupt coming in and moving the head
713 * page on another writer. Thus we use the second LSB to catch
714 * that too. Thus:
715 *
716 * head->list->prev->next bit 1 bit 0
717 * ------- -------
718 * Normal page 0 0
719 * Points to head page 0 1
720 * New head page 1 0
721 *
722 * Note we can not trust the prev pointer of the head page, because:
723 *
724 * +----+ +-----+ +-----+
725 * | |------>| T |---X--->| N |
726 * | |<------| | | |
727 * +----+ +-----+ +-----+
728 * ^ ^ |
729 * | +-----+ | |
730 * +----------| R |----------+ |
731 * | |<-----------+
732 * +-----+
733 *
734 * Key: ---X--> HEAD flag set in pointer
735 * T Tail page
736 * R Reader page
737 * N Next page
738 *
739 * (see __rb_reserve_next() to see where this happens)
740 *
741 * What the above shows is that the reader just swapped out
742 * the reader page with a page in the buffer, but before it
743 * could make the new header point back to the new page added
744 * it was preempted by a writer. The writer moved forward onto
745 * the new page added by the reader and is about to move forward
746 * again.
747 *
748 * You can see, it is legitimate for the previous pointer of
749 * the head (or any page) not to point back to itself. But only
750 * temporarially.
751 */
752
753#define RB_PAGE_NORMAL 0UL
754#define RB_PAGE_HEAD 1UL
755#define RB_PAGE_UPDATE 2UL
756
757
758#define RB_FLAG_MASK 3UL
759
760/* PAGE_MOVED is not part of the mask */
761#define RB_PAGE_MOVED 4UL
762
763/*
764 * rb_list_head - remove any bit
765 */
766static struct list_head *rb_list_head(struct list_head *list)
767{
768 unsigned long val = (unsigned long)list;
769
770 return (struct list_head *)(val & ~RB_FLAG_MASK);
771}
772
773/*
774 * rb_is_head_page - test if the given page is the head page
775 *
776 * Because the reader may move the head_page pointer, we can
777 * not trust what the head page is (it may be pointing to
778 * the reader page). But if the next page is a header page,
779 * its flags will be non zero.
780 */
781static inline int
782rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
783 struct buffer_page *page, struct list_head *list)
784{
785 unsigned long val;
786
787 val = (unsigned long)list->next;
788
789 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
790 return RB_PAGE_MOVED;
791
792 return val & RB_FLAG_MASK;
793}
794
795/*
796 * rb_is_reader_page
797 *
798 * The unique thing about the reader page, is that, if the
799 * writer is ever on it, the previous pointer never points
800 * back to the reader page.
801 */
802static int rb_is_reader_page(struct buffer_page *page)
803{
804 struct list_head *list = page->list.prev;
805
806 return rb_list_head(list->next) != &page->list;
807}
808
809/*
810 * rb_set_list_to_head - set a list_head to be pointing to head.
811 */
812static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
813 struct list_head *list)
814{
815 unsigned long *ptr;
816
817 ptr = (unsigned long *)&list->next;
818 *ptr |= RB_PAGE_HEAD;
819 *ptr &= ~RB_PAGE_UPDATE;
820}
821
822/*
823 * rb_head_page_activate - sets up head page
824 */
825static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
826{
827 struct buffer_page *head;
828
829 head = cpu_buffer->head_page;
830 if (!head)
831 return;
832
833 /*
834 * Set the previous list pointer to have the HEAD flag.
835 */
836 rb_set_list_to_head(cpu_buffer, head->list.prev);
837}
838
839static void rb_list_head_clear(struct list_head *list)
840{
841 unsigned long *ptr = (unsigned long *)&list->next;
842
843 *ptr &= ~RB_FLAG_MASK;
844}
845
846/*
847 * rb_head_page_dactivate - clears head page ptr (for free list)
848 */
849static void
850rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
851{
852 struct list_head *hd;
853
854 /* Go through the whole list and clear any pointers found. */
855 rb_list_head_clear(cpu_buffer->pages);
856
857 list_for_each(hd, cpu_buffer->pages)
858 rb_list_head_clear(hd);
859}
860
861static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
862 struct buffer_page *head,
863 struct buffer_page *prev,
864 int old_flag, int new_flag)
865{
866 struct list_head *list;
867 unsigned long val = (unsigned long)&head->list;
868 unsigned long ret;
869
870 list = &prev->list;
871
872 val &= ~RB_FLAG_MASK;
873
874 ret = cmpxchg((unsigned long *)&list->next,
875 val | old_flag, val | new_flag);
876
877 /* check if the reader took the page */
878 if ((ret & ~RB_FLAG_MASK) != val)
879 return RB_PAGE_MOVED;
880
881 return ret & RB_FLAG_MASK;
882}
883
884static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
885 struct buffer_page *head,
886 struct buffer_page *prev,
887 int old_flag)
888{
889 return rb_head_page_set(cpu_buffer, head, prev,
890 old_flag, RB_PAGE_UPDATE);
891}
892
893static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
894 struct buffer_page *head,
895 struct buffer_page *prev,
896 int old_flag)
897{
898 return rb_head_page_set(cpu_buffer, head, prev,
899 old_flag, RB_PAGE_HEAD);
900}
901
902static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
903 struct buffer_page *head,
904 struct buffer_page *prev,
905 int old_flag)
906{
907 return rb_head_page_set(cpu_buffer, head, prev,
908 old_flag, RB_PAGE_NORMAL);
909}
910
911static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
912 struct buffer_page **bpage)
913{
914 struct list_head *p = rb_list_head((*bpage)->list.next);
915
916 *bpage = list_entry(p, struct buffer_page, list);
917}
918
919static struct buffer_page *
920rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
921{
922 struct buffer_page *head;
923 struct buffer_page *page;
924 struct list_head *list;
925 int i;
926
927 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
928 return NULL;
929
930 /* sanity check */
931 list = cpu_buffer->pages;
932 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
933 return NULL;
934
935 page = head = cpu_buffer->head_page;
936 /*
937 * It is possible that the writer moves the header behind
938 * where we started, and we miss in one loop.
939 * A second loop should grab the header, but we'll do
940 * three loops just because I'm paranoid.
941 */
942 for (i = 0; i < 3; i++) {
943 do {
944 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
945 cpu_buffer->head_page = page;
946 return page;
947 }
948 rb_inc_page(cpu_buffer, &page);
949 } while (page != head);
950 }
951
952 RB_WARN_ON(cpu_buffer, 1);
953
954 return NULL;
955}
956
957static int rb_head_page_replace(struct buffer_page *old,
958 struct buffer_page *new)
959{
960 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
961 unsigned long val;
962 unsigned long ret;
963
964 val = *ptr & ~RB_FLAG_MASK;
965 val |= RB_PAGE_HEAD;
966
967 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
968
969 return ret == val;
970}
971
972/*
973 * rb_tail_page_update - move the tail page forward
974 *
975 * Returns 1 if moved tail page, 0 if someone else did.
976 */
977static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
978 struct buffer_page *tail_page,
979 struct buffer_page *next_page)
980{
981 struct buffer_page *old_tail;
982 unsigned long old_entries;
983 unsigned long old_write;
984 int ret = 0;
985
986 /*
987 * The tail page now needs to be moved forward.
988 *
989 * We need to reset the tail page, but without messing
990 * with possible erasing of data brought in by interrupts
991 * that have moved the tail page and are currently on it.
992 *
993 * We add a counter to the write field to denote this.
994 */
995 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
996 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
997
998 /*
999 * Just make sure we have seen our old_write and synchronize
1000 * with any interrupts that come in.
1001 */
1002 barrier();
1003
1004 /*
1005 * If the tail page is still the same as what we think
1006 * it is, then it is up to us to update the tail
1007 * pointer.
1008 */
1009 if (tail_page == cpu_buffer->tail_page) {
1010 /* Zero the write counter */
1011 unsigned long val = old_write & ~RB_WRITE_MASK;
1012 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1013
1014 /*
1015 * This will only succeed if an interrupt did
1016 * not come in and change it. In which case, we
1017 * do not want to modify it.
1018 *
1019 * We add (void) to let the compiler know that we do not care
1020 * about the return value of these functions. We use the
1021 * cmpxchg to only update if an interrupt did not already
1022 * do it for us. If the cmpxchg fails, we don't care.
1023 */
1024 (void)local_cmpxchg(&next_page->write, old_write, val);
1025 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1026
1027 /*
1028 * No need to worry about races with clearing out the commit.
1029 * it only can increment when a commit takes place. But that
1030 * only happens in the outer most nested commit.
1031 */
1032 local_set(&next_page->page->commit, 0);
1033
1034 old_tail = cmpxchg(&cpu_buffer->tail_page,
1035 tail_page, next_page);
1036
1037 if (old_tail == tail_page)
1038 ret = 1;
1039 }
1040
1041 return ret;
1042}
1043
1044static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1045 struct buffer_page *bpage)
1046{
1047 unsigned long val = (unsigned long)bpage;
1048
1049 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1050 return 1;
1051
1052 return 0;
1053}
1054
1055/**
1056 * rb_check_list - make sure a pointer to a list has the last bits zero
1057 */
1058static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1059 struct list_head *list)
1060{
1061 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1062 return 1;
1063 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1064 return 1;
1065 return 0;
1066}
1067
1068/**
1069 * rb_check_pages - integrity check of buffer pages
1070 * @cpu_buffer: CPU buffer with pages to test
1071 *
1072 * As a safety measure we check to make sure the data pages have not
1073 * been corrupted.
1074 */
1075static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1076{
1077 struct list_head *head = cpu_buffer->pages;
1078 struct buffer_page *bpage, *tmp;
1079
1080 /* Reset the head page if it exists */
1081 if (cpu_buffer->head_page)
1082 rb_set_head_page(cpu_buffer);
1083
1084 rb_head_page_deactivate(cpu_buffer);
1085
1086 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1087 return -1;
1088 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1089 return -1;
1090
1091 if (rb_check_list(cpu_buffer, head))
1092 return -1;
1093
1094 list_for_each_entry_safe(bpage, tmp, head, list) {
1095 if (RB_WARN_ON(cpu_buffer,
1096 bpage->list.next->prev != &bpage->list))
1097 return -1;
1098 if (RB_WARN_ON(cpu_buffer,
1099 bpage->list.prev->next != &bpage->list))
1100 return -1;
1101 if (rb_check_list(cpu_buffer, &bpage->list))
1102 return -1;
1103 }
1104
1105 rb_head_page_activate(cpu_buffer);
1106
1107 return 0;
1108}
1109
1110static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
1111{
1112 int i;
1113 struct buffer_page *bpage, *tmp;
1114
1115 for (i = 0; i < nr_pages; i++) {
1116 struct page *page;
1117 /*
1118 * __GFP_NORETRY flag makes sure that the allocation fails
1119 * gracefully without invoking oom-killer and the system is
1120 * not destabilized.
1121 */
1122 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1123 GFP_KERNEL | __GFP_NORETRY,
1124 cpu_to_node(cpu));
1125 if (!bpage)
1126 goto free_pages;
1127
1128 list_add(&bpage->list, pages);
1129
1130 page = alloc_pages_node(cpu_to_node(cpu),
1131 GFP_KERNEL | __GFP_NORETRY, 0);
1132 if (!page)
1133 goto free_pages;
1134 bpage->page = page_address(page);
1135 rb_init_page(bpage->page);
1136 }
1137
1138 return 0;
1139
1140free_pages:
1141 list_for_each_entry_safe(bpage, tmp, pages, list) {
1142 list_del_init(&bpage->list);
1143 free_buffer_page(bpage);
1144 }
1145
1146 return -ENOMEM;
1147}
1148
1149static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1150 unsigned nr_pages)
1151{
1152 LIST_HEAD(pages);
1153
1154 WARN_ON(!nr_pages);
1155
1156 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1157 return -ENOMEM;
1158
1159 /*
1160 * The ring buffer page list is a circular list that does not
1161 * start and end with a list head. All page list items point to
1162 * other pages.
1163 */
1164 cpu_buffer->pages = pages.next;
1165 list_del(&pages);
1166
1167 cpu_buffer->nr_pages = nr_pages;
1168
1169 rb_check_pages(cpu_buffer);
1170
1171 return 0;
1172}
1173
1174static struct ring_buffer_per_cpu *
1175rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
1176{
1177 struct ring_buffer_per_cpu *cpu_buffer;
1178 struct buffer_page *bpage;
1179 struct page *page;
1180 int ret;
1181
1182 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1183 GFP_KERNEL, cpu_to_node(cpu));
1184 if (!cpu_buffer)
1185 return NULL;
1186
1187 cpu_buffer->cpu = cpu;
1188 cpu_buffer->buffer = buffer;
1189 raw_spin_lock_init(&cpu_buffer->reader_lock);
1190 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1191 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1192 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1193 init_completion(&cpu_buffer->update_done);
1194 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1195 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1196
1197 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1198 GFP_KERNEL, cpu_to_node(cpu));
1199 if (!bpage)
1200 goto fail_free_buffer;
1201
1202 rb_check_bpage(cpu_buffer, bpage);
1203
1204 cpu_buffer->reader_page = bpage;
1205 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1206 if (!page)
1207 goto fail_free_reader;
1208 bpage->page = page_address(page);
1209 rb_init_page(bpage->page);
1210
1211 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1212 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1213
1214 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1215 if (ret < 0)
1216 goto fail_free_reader;
1217
1218 cpu_buffer->head_page
1219 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1220 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1221
1222 rb_head_page_activate(cpu_buffer);
1223
1224 return cpu_buffer;
1225
1226 fail_free_reader:
1227 free_buffer_page(cpu_buffer->reader_page);
1228
1229 fail_free_buffer:
1230 kfree(cpu_buffer);
1231 return NULL;
1232}
1233
1234static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1235{
1236 struct list_head *head = cpu_buffer->pages;
1237 struct buffer_page *bpage, *tmp;
1238
1239 free_buffer_page(cpu_buffer->reader_page);
1240
1241 rb_head_page_deactivate(cpu_buffer);
1242
1243 if (head) {
1244 list_for_each_entry_safe(bpage, tmp, head, list) {
1245 list_del_init(&bpage->list);
1246 free_buffer_page(bpage);
1247 }
1248 bpage = list_entry(head, struct buffer_page, list);
1249 free_buffer_page(bpage);
1250 }
1251
1252 kfree(cpu_buffer);
1253}
1254
1255#ifdef CONFIG_HOTPLUG_CPU
1256static int rb_cpu_notify(struct notifier_block *self,
1257 unsigned long action, void *hcpu);
1258#endif
1259
1260/**
1261 * __ring_buffer_alloc - allocate a new ring_buffer
1262 * @size: the size in bytes per cpu that is needed.
1263 * @flags: attributes to set for the ring buffer.
1264 *
1265 * Currently the only flag that is available is the RB_FL_OVERWRITE
1266 * flag. This flag means that the buffer will overwrite old data
1267 * when the buffer wraps. If this flag is not set, the buffer will
1268 * drop data when the tail hits the head.
1269 */
1270struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1271 struct lock_class_key *key)
1272{
1273 struct ring_buffer *buffer;
1274 int bsize;
1275 int cpu, nr_pages;
1276
1277 /* keep it in its own cache line */
1278 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1279 GFP_KERNEL);
1280 if (!buffer)
1281 return NULL;
1282
1283 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1284 goto fail_free_buffer;
1285
1286 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1287 buffer->flags = flags;
1288 buffer->clock = trace_clock_local;
1289 buffer->reader_lock_key = key;
1290
1291 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1292 init_waitqueue_head(&buffer->irq_work.waiters);
1293
1294 /* need at least two pages */
1295 if (nr_pages < 2)
1296 nr_pages = 2;
1297
1298 /*
1299 * In case of non-hotplug cpu, if the ring-buffer is allocated
1300 * in early initcall, it will not be notified of secondary cpus.
1301 * In that off case, we need to allocate for all possible cpus.
1302 */
1303#ifdef CONFIG_HOTPLUG_CPU
1304 cpu_notifier_register_begin();
1305 cpumask_copy(buffer->cpumask, cpu_online_mask);
1306#else
1307 cpumask_copy(buffer->cpumask, cpu_possible_mask);
1308#endif
1309 buffer->cpus = nr_cpu_ids;
1310
1311 bsize = sizeof(void *) * nr_cpu_ids;
1312 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1313 GFP_KERNEL);
1314 if (!buffer->buffers)
1315 goto fail_free_cpumask;
1316
1317 for_each_buffer_cpu(buffer, cpu) {
1318 buffer->buffers[cpu] =
1319 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1320 if (!buffer->buffers[cpu])
1321 goto fail_free_buffers;
1322 }
1323
1324#ifdef CONFIG_HOTPLUG_CPU
1325 buffer->cpu_notify.notifier_call = rb_cpu_notify;
1326 buffer->cpu_notify.priority = 0;
1327 __register_cpu_notifier(&buffer->cpu_notify);
1328 cpu_notifier_register_done();
1329#endif
1330
1331 mutex_init(&buffer->mutex);
1332
1333 return buffer;
1334
1335 fail_free_buffers:
1336 for_each_buffer_cpu(buffer, cpu) {
1337 if (buffer->buffers[cpu])
1338 rb_free_cpu_buffer(buffer->buffers[cpu]);
1339 }
1340 kfree(buffer->buffers);
1341
1342 fail_free_cpumask:
1343 free_cpumask_var(buffer->cpumask);
1344#ifdef CONFIG_HOTPLUG_CPU
1345 cpu_notifier_register_done();
1346#endif
1347
1348 fail_free_buffer:
1349 kfree(buffer);
1350 return NULL;
1351}
1352EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1353
1354/**
1355 * ring_buffer_free - free a ring buffer.
1356 * @buffer: the buffer to free.
1357 */
1358void
1359ring_buffer_free(struct ring_buffer *buffer)
1360{
1361 int cpu;
1362
1363#ifdef CONFIG_HOTPLUG_CPU
1364 cpu_notifier_register_begin();
1365 __unregister_cpu_notifier(&buffer->cpu_notify);
1366#endif
1367
1368 for_each_buffer_cpu(buffer, cpu)
1369 rb_free_cpu_buffer(buffer->buffers[cpu]);
1370
1371#ifdef CONFIG_HOTPLUG_CPU
1372 cpu_notifier_register_done();
1373#endif
1374
1375 kfree(buffer->buffers);
1376 free_cpumask_var(buffer->cpumask);
1377
1378 kfree(buffer);
1379}
1380EXPORT_SYMBOL_GPL(ring_buffer_free);
1381
1382void ring_buffer_set_clock(struct ring_buffer *buffer,
1383 u64 (*clock)(void))
1384{
1385 buffer->clock = clock;
1386}
1387
1388static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1389
1390static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1391{
1392 return local_read(&bpage->entries) & RB_WRITE_MASK;
1393}
1394
1395static inline unsigned long rb_page_write(struct buffer_page *bpage)
1396{
1397 return local_read(&bpage->write) & RB_WRITE_MASK;
1398}
1399
1400static int
1401rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
1402{
1403 struct list_head *tail_page, *to_remove, *next_page;
1404 struct buffer_page *to_remove_page, *tmp_iter_page;
1405 struct buffer_page *last_page, *first_page;
1406 unsigned int nr_removed;
1407 unsigned long head_bit;
1408 int page_entries;
1409
1410 head_bit = 0;
1411
1412 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1413 atomic_inc(&cpu_buffer->record_disabled);
1414 /*
1415 * We don't race with the readers since we have acquired the reader
1416 * lock. We also don't race with writers after disabling recording.
1417 * This makes it easy to figure out the first and the last page to be
1418 * removed from the list. We unlink all the pages in between including
1419 * the first and last pages. This is done in a busy loop so that we
1420 * lose the least number of traces.
1421 * The pages are freed after we restart recording and unlock readers.
1422 */
1423 tail_page = &cpu_buffer->tail_page->list;
1424
1425 /*
1426 * tail page might be on reader page, we remove the next page
1427 * from the ring buffer
1428 */
1429 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1430 tail_page = rb_list_head(tail_page->next);
1431 to_remove = tail_page;
1432
1433 /* start of pages to remove */
1434 first_page = list_entry(rb_list_head(to_remove->next),
1435 struct buffer_page, list);
1436
1437 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1438 to_remove = rb_list_head(to_remove)->next;
1439 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1440 }
1441
1442 next_page = rb_list_head(to_remove)->next;
1443
1444 /*
1445 * Now we remove all pages between tail_page and next_page.
1446 * Make sure that we have head_bit value preserved for the
1447 * next page
1448 */
1449 tail_page->next = (struct list_head *)((unsigned long)next_page |
1450 head_bit);
1451 next_page = rb_list_head(next_page);
1452 next_page->prev = tail_page;
1453
1454 /* make sure pages points to a valid page in the ring buffer */
1455 cpu_buffer->pages = next_page;
1456
1457 /* update head page */
1458 if (head_bit)
1459 cpu_buffer->head_page = list_entry(next_page,
1460 struct buffer_page, list);
1461
1462 /*
1463 * change read pointer to make sure any read iterators reset
1464 * themselves
1465 */
1466 cpu_buffer->read = 0;
1467
1468 /* pages are removed, resume tracing and then free the pages */
1469 atomic_dec(&cpu_buffer->record_disabled);
1470 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1471
1472 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1473
1474 /* last buffer page to remove */
1475 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1476 list);
1477 tmp_iter_page = first_page;
1478
1479 do {
1480 to_remove_page = tmp_iter_page;
1481 rb_inc_page(cpu_buffer, &tmp_iter_page);
1482
1483 /* update the counters */
1484 page_entries = rb_page_entries(to_remove_page);
1485 if (page_entries) {
1486 /*
1487 * If something was added to this page, it was full
1488 * since it is not the tail page. So we deduct the
1489 * bytes consumed in ring buffer from here.
1490 * Increment overrun to account for the lost events.
1491 */
1492 local_add(page_entries, &cpu_buffer->overrun);
1493 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1494 }
1495
1496 /*
1497 * We have already removed references to this list item, just
1498 * free up the buffer_page and its page
1499 */
1500 free_buffer_page(to_remove_page);
1501 nr_removed--;
1502
1503 } while (to_remove_page != last_page);
1504
1505 RB_WARN_ON(cpu_buffer, nr_removed);
1506
1507 return nr_removed == 0;
1508}
1509
1510static int
1511rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1512{
1513 struct list_head *pages = &cpu_buffer->new_pages;
1514 int retries, success;
1515
1516 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1517 /*
1518 * We are holding the reader lock, so the reader page won't be swapped
1519 * in the ring buffer. Now we are racing with the writer trying to
1520 * move head page and the tail page.
1521 * We are going to adapt the reader page update process where:
1522 * 1. We first splice the start and end of list of new pages between
1523 * the head page and its previous page.
1524 * 2. We cmpxchg the prev_page->next to point from head page to the
1525 * start of new pages list.
1526 * 3. Finally, we update the head->prev to the end of new list.
1527 *
1528 * We will try this process 10 times, to make sure that we don't keep
1529 * spinning.
1530 */
1531 retries = 10;
1532 success = 0;
1533 while (retries--) {
1534 struct list_head *head_page, *prev_page, *r;
1535 struct list_head *last_page, *first_page;
1536 struct list_head *head_page_with_bit;
1537
1538 head_page = &rb_set_head_page(cpu_buffer)->list;
1539 if (!head_page)
1540 break;
1541 prev_page = head_page->prev;
1542
1543 first_page = pages->next;
1544 last_page = pages->prev;
1545
1546 head_page_with_bit = (struct list_head *)
1547 ((unsigned long)head_page | RB_PAGE_HEAD);
1548
1549 last_page->next = head_page_with_bit;
1550 first_page->prev = prev_page;
1551
1552 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1553
1554 if (r == head_page_with_bit) {
1555 /*
1556 * yay, we replaced the page pointer to our new list,
1557 * now, we just have to update to head page's prev
1558 * pointer to point to end of list
1559 */
1560 head_page->prev = last_page;
1561 success = 1;
1562 break;
1563 }
1564 }
1565
1566 if (success)
1567 INIT_LIST_HEAD(pages);
1568 /*
1569 * If we weren't successful in adding in new pages, warn and stop
1570 * tracing
1571 */
1572 RB_WARN_ON(cpu_buffer, !success);
1573 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1574
1575 /* free pages if they weren't inserted */
1576 if (!success) {
1577 struct buffer_page *bpage, *tmp;
1578 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1579 list) {
1580 list_del_init(&bpage->list);
1581 free_buffer_page(bpage);
1582 }
1583 }
1584 return success;
1585}
1586
1587static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1588{
1589 int success;
1590
1591 if (cpu_buffer->nr_pages_to_update > 0)
1592 success = rb_insert_pages(cpu_buffer);
1593 else
1594 success = rb_remove_pages(cpu_buffer,
1595 -cpu_buffer->nr_pages_to_update);
1596
1597 if (success)
1598 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1599}
1600
1601static void update_pages_handler(struct work_struct *work)
1602{
1603 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1604 struct ring_buffer_per_cpu, update_pages_work);
1605 rb_update_pages(cpu_buffer);
1606 complete(&cpu_buffer->update_done);
1607}
1608
1609/**
1610 * ring_buffer_resize - resize the ring buffer
1611 * @buffer: the buffer to resize.
1612 * @size: the new size.
1613 * @cpu_id: the cpu buffer to resize
1614 *
1615 * Minimum size is 2 * BUF_PAGE_SIZE.
1616 *
1617 * Returns 0 on success and < 0 on failure.
1618 */
1619int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1620 int cpu_id)
1621{
1622 struct ring_buffer_per_cpu *cpu_buffer;
1623 unsigned nr_pages;
1624 int cpu, err = 0;
1625
1626 /*
1627 * Always succeed at resizing a non-existent buffer:
1628 */
1629 if (!buffer)
1630 return size;
1631
1632 /* Make sure the requested buffer exists */
1633 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1634 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1635 return size;
1636
1637 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1638 size *= BUF_PAGE_SIZE;
1639
1640 /* we need a minimum of two pages */
1641 if (size < BUF_PAGE_SIZE * 2)
1642 size = BUF_PAGE_SIZE * 2;
1643
1644 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1645
1646 /*
1647 * Don't succeed if resizing is disabled, as a reader might be
1648 * manipulating the ring buffer and is expecting a sane state while
1649 * this is true.
1650 */
1651 if (atomic_read(&buffer->resize_disabled))
1652 return -EBUSY;
1653
1654 /* prevent another thread from changing buffer sizes */
1655 mutex_lock(&buffer->mutex);
1656
1657 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1658 /* calculate the pages to update */
1659 for_each_buffer_cpu(buffer, cpu) {
1660 cpu_buffer = buffer->buffers[cpu];
1661
1662 cpu_buffer->nr_pages_to_update = nr_pages -
1663 cpu_buffer->nr_pages;
1664 /*
1665 * nothing more to do for removing pages or no update
1666 */
1667 if (cpu_buffer->nr_pages_to_update <= 0)
1668 continue;
1669 /*
1670 * to add pages, make sure all new pages can be
1671 * allocated without receiving ENOMEM
1672 */
1673 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1674 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1675 &cpu_buffer->new_pages, cpu)) {
1676 /* not enough memory for new pages */
1677 err = -ENOMEM;
1678 goto out_err;
1679 }
1680 }
1681
1682 get_online_cpus();
1683 /*
1684 * Fire off all the required work handlers
1685 * We can't schedule on offline CPUs, but it's not necessary
1686 * since we can change their buffer sizes without any race.
1687 */
1688 for_each_buffer_cpu(buffer, cpu) {
1689 cpu_buffer = buffer->buffers[cpu];
1690 if (!cpu_buffer->nr_pages_to_update)
1691 continue;
1692
1693 /* The update must run on the CPU that is being updated. */
1694 preempt_disable();
1695 if (cpu == smp_processor_id() || !cpu_online(cpu)) {
1696 rb_update_pages(cpu_buffer);
1697 cpu_buffer->nr_pages_to_update = 0;
1698 } else {
1699 /*
1700 * Can not disable preemption for schedule_work_on()
1701 * on PREEMPT_RT.
1702 */
1703 preempt_enable();
1704 schedule_work_on(cpu,
1705 &cpu_buffer->update_pages_work);
1706 preempt_disable();
1707 }
1708 preempt_enable();
1709 }
1710
1711 /* wait for all the updates to complete */
1712 for_each_buffer_cpu(buffer, cpu) {
1713 cpu_buffer = buffer->buffers[cpu];
1714 if (!cpu_buffer->nr_pages_to_update)
1715 continue;
1716
1717 if (cpu_online(cpu))
1718 wait_for_completion(&cpu_buffer->update_done);
1719 cpu_buffer->nr_pages_to_update = 0;
1720 }
1721
1722 put_online_cpus();
1723 } else {
1724 /* Make sure this CPU has been intitialized */
1725 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1726 goto out;
1727
1728 cpu_buffer = buffer->buffers[cpu_id];
1729
1730 if (nr_pages == cpu_buffer->nr_pages)
1731 goto out;
1732
1733 cpu_buffer->nr_pages_to_update = nr_pages -
1734 cpu_buffer->nr_pages;
1735
1736 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1737 if (cpu_buffer->nr_pages_to_update > 0 &&
1738 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1739 &cpu_buffer->new_pages, cpu_id)) {
1740 err = -ENOMEM;
1741 goto out_err;
1742 }
1743
1744 get_online_cpus();
1745
1746 preempt_disable();
1747 /* The update must run on the CPU that is being updated. */
1748 if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
1749 rb_update_pages(cpu_buffer);
1750 else {
1751 /*
1752 * Can not disable preemption for schedule_work_on()
1753 * on PREEMPT_RT.
1754 */
1755 preempt_enable();
1756 schedule_work_on(cpu_id,
1757 &cpu_buffer->update_pages_work);
1758 wait_for_completion(&cpu_buffer->update_done);
1759 preempt_disable();
1760 }
1761 preempt_enable();
1762
1763 cpu_buffer->nr_pages_to_update = 0;
1764 put_online_cpus();
1765 }
1766
1767 out:
1768 /*
1769 * The ring buffer resize can happen with the ring buffer
1770 * enabled, so that the update disturbs the tracing as little
1771 * as possible. But if the buffer is disabled, we do not need
1772 * to worry about that, and we can take the time to verify
1773 * that the buffer is not corrupt.
1774 */
1775 if (atomic_read(&buffer->record_disabled)) {
1776 atomic_inc(&buffer->record_disabled);
1777 /*
1778 * Even though the buffer was disabled, we must make sure
1779 * that it is truly disabled before calling rb_check_pages.
1780 * There could have been a race between checking
1781 * record_disable and incrementing it.
1782 */
1783 synchronize_sched();
1784 for_each_buffer_cpu(buffer, cpu) {
1785 cpu_buffer = buffer->buffers[cpu];
1786 rb_check_pages(cpu_buffer);
1787 }
1788 atomic_dec(&buffer->record_disabled);
1789 }
1790
1791 mutex_unlock(&buffer->mutex);
1792 return size;
1793
1794 out_err:
1795 for_each_buffer_cpu(buffer, cpu) {
1796 struct buffer_page *bpage, *tmp;
1797
1798 cpu_buffer = buffer->buffers[cpu];
1799 cpu_buffer->nr_pages_to_update = 0;
1800
1801 if (list_empty(&cpu_buffer->new_pages))
1802 continue;
1803
1804 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1805 list) {
1806 list_del_init(&bpage->list);
1807 free_buffer_page(bpage);
1808 }
1809 }
1810 mutex_unlock(&buffer->mutex);
1811 return err;
1812}
1813EXPORT_SYMBOL_GPL(ring_buffer_resize);
1814
1815void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1816{
1817 mutex_lock(&buffer->mutex);
1818 if (val)
1819 buffer->flags |= RB_FL_OVERWRITE;
1820 else
1821 buffer->flags &= ~RB_FL_OVERWRITE;
1822 mutex_unlock(&buffer->mutex);
1823}
1824EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1825
1826static inline void *
1827__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
1828{
1829 return bpage->data + index;
1830}
1831
1832static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1833{
1834 return bpage->page->data + index;
1835}
1836
1837static inline struct ring_buffer_event *
1838rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1839{
1840 return __rb_page_index(cpu_buffer->reader_page,
1841 cpu_buffer->reader_page->read);
1842}
1843
1844static inline struct ring_buffer_event *
1845rb_iter_head_event(struct ring_buffer_iter *iter)
1846{
1847 return __rb_page_index(iter->head_page, iter->head);
1848}
1849
1850static inline unsigned rb_page_commit(struct buffer_page *bpage)
1851{
1852 return local_read(&bpage->page->commit);
1853}
1854
1855/* Size is determined by what has been committed */
1856static inline unsigned rb_page_size(struct buffer_page *bpage)
1857{
1858 return rb_page_commit(bpage);
1859}
1860
1861static inline unsigned
1862rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1863{
1864 return rb_page_commit(cpu_buffer->commit_page);
1865}
1866
1867static inline unsigned
1868rb_event_index(struct ring_buffer_event *event)
1869{
1870 unsigned long addr = (unsigned long)event;
1871
1872 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1873}
1874
1875static inline int
1876rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1877 struct ring_buffer_event *event)
1878{
1879 unsigned long addr = (unsigned long)event;
1880 unsigned long index;
1881
1882 index = rb_event_index(event);
1883 addr &= PAGE_MASK;
1884
1885 return cpu_buffer->commit_page->page == (void *)addr &&
1886 rb_commit_index(cpu_buffer) == index;
1887}
1888
1889static void
1890rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1891{
1892 unsigned long max_count;
1893
1894 /*
1895 * We only race with interrupts and NMIs on this CPU.
1896 * If we own the commit event, then we can commit
1897 * all others that interrupted us, since the interruptions
1898 * are in stack format (they finish before they come
1899 * back to us). This allows us to do a simple loop to
1900 * assign the commit to the tail.
1901 */
1902 again:
1903 max_count = cpu_buffer->nr_pages * 100;
1904
1905 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1906 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
1907 return;
1908 if (RB_WARN_ON(cpu_buffer,
1909 rb_is_reader_page(cpu_buffer->tail_page)))
1910 return;
1911 local_set(&cpu_buffer->commit_page->page->commit,
1912 rb_page_write(cpu_buffer->commit_page));
1913 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1914 cpu_buffer->write_stamp =
1915 cpu_buffer->commit_page->page->time_stamp;
1916 /* add barrier to keep gcc from optimizing too much */
1917 barrier();
1918 }
1919 while (rb_commit_index(cpu_buffer) !=
1920 rb_page_write(cpu_buffer->commit_page)) {
1921
1922 local_set(&cpu_buffer->commit_page->page->commit,
1923 rb_page_write(cpu_buffer->commit_page));
1924 RB_WARN_ON(cpu_buffer,
1925 local_read(&cpu_buffer->commit_page->page->commit) &
1926 ~RB_WRITE_MASK);
1927 barrier();
1928 }
1929
1930 /* again, keep gcc from optimizing */
1931 barrier();
1932
1933 /*
1934 * If an interrupt came in just after the first while loop
1935 * and pushed the tail page forward, we will be left with
1936 * a dangling commit that will never go forward.
1937 */
1938 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1939 goto again;
1940}
1941
1942static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1943{
1944 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1945 cpu_buffer->reader_page->read = 0;
1946}
1947
1948static void rb_inc_iter(struct ring_buffer_iter *iter)
1949{
1950 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1951
1952 /*
1953 * The iterator could be on the reader page (it starts there).
1954 * But the head could have moved, since the reader was
1955 * found. Check for this case and assign the iterator
1956 * to the head page instead of next.
1957 */
1958 if (iter->head_page == cpu_buffer->reader_page)
1959 iter->head_page = rb_set_head_page(cpu_buffer);
1960 else
1961 rb_inc_page(cpu_buffer, &iter->head_page);
1962
1963 iter->read_stamp = iter->head_page->page->time_stamp;
1964 iter->head = 0;
1965}
1966
1967/* Slow path, do not inline */
1968static noinline struct ring_buffer_event *
1969rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
1970{
1971 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
1972
1973 /* Not the first event on the page? */
1974 if (rb_event_index(event)) {
1975 event->time_delta = delta & TS_MASK;
1976 event->array[0] = delta >> TS_SHIFT;
1977 } else {
1978 /* nope, just zero it */
1979 event->time_delta = 0;
1980 event->array[0] = 0;
1981 }
1982
1983 return skip_time_extend(event);
1984}
1985
1986/**
1987 * rb_update_event - update event type and data
1988 * @event: the even to update
1989 * @type: the type of event
1990 * @length: the size of the event field in the ring buffer
1991 *
1992 * Update the type and data fields of the event. The length
1993 * is the actual size that is written to the ring buffer,
1994 * and with this, we can determine what to place into the
1995 * data field.
1996 */
1997static void
1998rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
1999 struct ring_buffer_event *event, unsigned length,
2000 int add_timestamp, u64 delta)
2001{
2002 /* Only a commit updates the timestamp */
2003 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2004 delta = 0;
2005
2006 /*
2007 * If we need to add a timestamp, then we
2008 * add it to the start of the resevered space.
2009 */
2010 if (unlikely(add_timestamp)) {
2011 event = rb_add_time_stamp(event, delta);
2012 length -= RB_LEN_TIME_EXTEND;
2013 delta = 0;
2014 }
2015
2016 event->time_delta = delta;
2017 length -= RB_EVNT_HDR_SIZE;
2018 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2019 event->type_len = 0;
2020 event->array[0] = length;
2021 } else
2022 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2023}
2024
2025/*
2026 * rb_handle_head_page - writer hit the head page
2027 *
2028 * Returns: +1 to retry page
2029 * 0 to continue
2030 * -1 on error
2031 */
2032static int
2033rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2034 struct buffer_page *tail_page,
2035 struct buffer_page *next_page)
2036{
2037 struct buffer_page *new_head;
2038 int entries;
2039 int type;
2040 int ret;
2041
2042 entries = rb_page_entries(next_page);
2043
2044 /*
2045 * The hard part is here. We need to move the head
2046 * forward, and protect against both readers on
2047 * other CPUs and writers coming in via interrupts.
2048 */
2049 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2050 RB_PAGE_HEAD);
2051
2052 /*
2053 * type can be one of four:
2054 * NORMAL - an interrupt already moved it for us
2055 * HEAD - we are the first to get here.
2056 * UPDATE - we are the interrupt interrupting
2057 * a current move.
2058 * MOVED - a reader on another CPU moved the next
2059 * pointer to its reader page. Give up
2060 * and try again.
2061 */
2062
2063 switch (type) {
2064 case RB_PAGE_HEAD:
2065 /*
2066 * We changed the head to UPDATE, thus
2067 * it is our responsibility to update
2068 * the counters.
2069 */
2070 local_add(entries, &cpu_buffer->overrun);
2071 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2072
2073 /*
2074 * The entries will be zeroed out when we move the
2075 * tail page.
2076 */
2077
2078 /* still more to do */
2079 break;
2080
2081 case RB_PAGE_UPDATE:
2082 /*
2083 * This is an interrupt that interrupt the
2084 * previous update. Still more to do.
2085 */
2086 break;
2087 case RB_PAGE_NORMAL:
2088 /*
2089 * An interrupt came in before the update
2090 * and processed this for us.
2091 * Nothing left to do.
2092 */
2093 return 1;
2094 case RB_PAGE_MOVED:
2095 /*
2096 * The reader is on another CPU and just did
2097 * a swap with our next_page.
2098 * Try again.
2099 */
2100 return 1;
2101 default:
2102 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2103 return -1;
2104 }
2105
2106 /*
2107 * Now that we are here, the old head pointer is
2108 * set to UPDATE. This will keep the reader from
2109 * swapping the head page with the reader page.
2110 * The reader (on another CPU) will spin till
2111 * we are finished.
2112 *
2113 * We just need to protect against interrupts
2114 * doing the job. We will set the next pointer
2115 * to HEAD. After that, we set the old pointer
2116 * to NORMAL, but only if it was HEAD before.
2117 * otherwise we are an interrupt, and only
2118 * want the outer most commit to reset it.
2119 */
2120 new_head = next_page;
2121 rb_inc_page(cpu_buffer, &new_head);
2122
2123 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2124 RB_PAGE_NORMAL);
2125
2126 /*
2127 * Valid returns are:
2128 * HEAD - an interrupt came in and already set it.
2129 * NORMAL - One of two things:
2130 * 1) We really set it.
2131 * 2) A bunch of interrupts came in and moved
2132 * the page forward again.
2133 */
2134 switch (ret) {
2135 case RB_PAGE_HEAD:
2136 case RB_PAGE_NORMAL:
2137 /* OK */
2138 break;
2139 default:
2140 RB_WARN_ON(cpu_buffer, 1);
2141 return -1;
2142 }
2143
2144 /*
2145 * It is possible that an interrupt came in,
2146 * set the head up, then more interrupts came in
2147 * and moved it again. When we get back here,
2148 * the page would have been set to NORMAL but we
2149 * just set it back to HEAD.
2150 *
2151 * How do you detect this? Well, if that happened
2152 * the tail page would have moved.
2153 */
2154 if (ret == RB_PAGE_NORMAL) {
2155 /*
2156 * If the tail had moved passed next, then we need
2157 * to reset the pointer.
2158 */
2159 if (cpu_buffer->tail_page != tail_page &&
2160 cpu_buffer->tail_page != next_page)
2161 rb_head_page_set_normal(cpu_buffer, new_head,
2162 next_page,
2163 RB_PAGE_HEAD);
2164 }
2165
2166 /*
2167 * If this was the outer most commit (the one that
2168 * changed the original pointer from HEAD to UPDATE),
2169 * then it is up to us to reset it to NORMAL.
2170 */
2171 if (type == RB_PAGE_HEAD) {
2172 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2173 tail_page,
2174 RB_PAGE_UPDATE);
2175 if (RB_WARN_ON(cpu_buffer,
2176 ret != RB_PAGE_UPDATE))
2177 return -1;
2178 }
2179
2180 return 0;
2181}
2182
2183static unsigned rb_calculate_event_length(unsigned length)
2184{
2185 struct ring_buffer_event event; /* Used only for sizeof array */
2186
2187 /* zero length can cause confusions */
2188 if (!length)
2189 length = 1;
2190
2191 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2192 length += sizeof(event.array[0]);
2193
2194 length += RB_EVNT_HDR_SIZE;
2195 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2196
2197 return length;
2198}
2199
2200static inline void
2201rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2202 struct buffer_page *tail_page,
2203 unsigned long tail, unsigned long length)
2204{
2205 struct ring_buffer_event *event;
2206
2207 /*
2208 * Only the event that crossed the page boundary
2209 * must fill the old tail_page with padding.
2210 */
2211 if (tail >= BUF_PAGE_SIZE) {
2212 /*
2213 * If the page was filled, then we still need
2214 * to update the real_end. Reset it to zero
2215 * and the reader will ignore it.
2216 */
2217 if (tail == BUF_PAGE_SIZE)
2218 tail_page->real_end = 0;
2219
2220 local_sub(length, &tail_page->write);
2221 return;
2222 }
2223
2224 event = __rb_page_index(tail_page, tail);
2225 kmemcheck_annotate_bitfield(event, bitfield);
2226
2227 /* account for padding bytes */
2228 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2229
2230 /*
2231 * Save the original length to the meta data.
2232 * This will be used by the reader to add lost event
2233 * counter.
2234 */
2235 tail_page->real_end = tail;
2236
2237 /*
2238 * If this event is bigger than the minimum size, then
2239 * we need to be careful that we don't subtract the
2240 * write counter enough to allow another writer to slip
2241 * in on this page.
2242 * We put in a discarded commit instead, to make sure
2243 * that this space is not used again.
2244 *
2245 * If we are less than the minimum size, we don't need to
2246 * worry about it.
2247 */
2248 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2249 /* No room for any events */
2250
2251 /* Mark the rest of the page with padding */
2252 rb_event_set_padding(event);
2253
2254 /* Set the write back to the previous setting */
2255 local_sub(length, &tail_page->write);
2256 return;
2257 }
2258
2259 /* Put in a discarded event */
2260 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2261 event->type_len = RINGBUF_TYPE_PADDING;
2262 /* time delta must be non zero */
2263 event->time_delta = 1;
2264
2265 /* Set write to end of buffer */
2266 length = (tail + length) - BUF_PAGE_SIZE;
2267 local_sub(length, &tail_page->write);
2268}
2269
2270/*
2271 * This is the slow path, force gcc not to inline it.
2272 */
2273static noinline struct ring_buffer_event *
2274rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2275 unsigned long length, unsigned long tail,
2276 struct buffer_page *tail_page, u64 ts)
2277{
2278 struct buffer_page *commit_page = cpu_buffer->commit_page;
2279 struct ring_buffer *buffer = cpu_buffer->buffer;
2280 struct buffer_page *next_page;
2281 int ret;
2282
2283 next_page = tail_page;
2284
2285 rb_inc_page(cpu_buffer, &next_page);
2286
2287 /*
2288 * If for some reason, we had an interrupt storm that made
2289 * it all the way around the buffer, bail, and warn
2290 * about it.
2291 */
2292 if (unlikely(next_page == commit_page)) {
2293 local_inc(&cpu_buffer->commit_overrun);
2294 goto out_reset;
2295 }
2296
2297 /*
2298 * This is where the fun begins!
2299 *
2300 * We are fighting against races between a reader that
2301 * could be on another CPU trying to swap its reader
2302 * page with the buffer head.
2303 *
2304 * We are also fighting against interrupts coming in and
2305 * moving the head or tail on us as well.
2306 *
2307 * If the next page is the head page then we have filled
2308 * the buffer, unless the commit page is still on the
2309 * reader page.
2310 */
2311 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2312
2313 /*
2314 * If the commit is not on the reader page, then
2315 * move the header page.
2316 */
2317 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2318 /*
2319 * If we are not in overwrite mode,
2320 * this is easy, just stop here.
2321 */
2322 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2323 local_inc(&cpu_buffer->dropped_events);
2324 goto out_reset;
2325 }
2326
2327 ret = rb_handle_head_page(cpu_buffer,
2328 tail_page,
2329 next_page);
2330 if (ret < 0)
2331 goto out_reset;
2332 if (ret)
2333 goto out_again;
2334 } else {
2335 /*
2336 * We need to be careful here too. The
2337 * commit page could still be on the reader
2338 * page. We could have a small buffer, and
2339 * have filled up the buffer with events
2340 * from interrupts and such, and wrapped.
2341 *
2342 * Note, if the tail page is also the on the
2343 * reader_page, we let it move out.
2344 */
2345 if (unlikely((cpu_buffer->commit_page !=
2346 cpu_buffer->tail_page) &&
2347 (cpu_buffer->commit_page ==
2348 cpu_buffer->reader_page))) {
2349 local_inc(&cpu_buffer->commit_overrun);
2350 goto out_reset;
2351 }
2352 }
2353 }
2354
2355 ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
2356 if (ret) {
2357 /*
2358 * Nested commits always have zero deltas, so
2359 * just reread the time stamp
2360 */
2361 ts = rb_time_stamp(buffer);
2362 next_page->page->time_stamp = ts;
2363 }
2364
2365 out_again:
2366
2367 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2368
2369 /* fail and let the caller try again */
2370 return ERR_PTR(-EAGAIN);
2371
2372 out_reset:
2373 /* reset write */
2374 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2375
2376 return NULL;
2377}
2378
2379static struct ring_buffer_event *
2380__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2381 unsigned long length, u64 ts,
2382 u64 delta, int add_timestamp)
2383{
2384 struct buffer_page *tail_page;
2385 struct ring_buffer_event *event;
2386 unsigned long tail, write;
2387
2388 /*
2389 * If the time delta since the last event is too big to
2390 * hold in the time field of the event, then we append a
2391 * TIME EXTEND event ahead of the data event.
2392 */
2393 if (unlikely(add_timestamp))
2394 length += RB_LEN_TIME_EXTEND;
2395
2396 tail_page = cpu_buffer->tail_page;
2397 write = local_add_return(length, &tail_page->write);
2398
2399 /* set write to only the index of the write */
2400 write &= RB_WRITE_MASK;
2401 tail = write - length;
2402
2403 /*
2404 * If this is the first commit on the page, then it has the same
2405 * timestamp as the page itself.
2406 */
2407 if (!tail)
2408 delta = 0;
2409
2410 /* See if we shot pass the end of this buffer page */
2411 if (unlikely(write > BUF_PAGE_SIZE))
2412 return rb_move_tail(cpu_buffer, length, tail,
2413 tail_page, ts);
2414
2415 /* We reserved something on the buffer */
2416
2417 event = __rb_page_index(tail_page, tail);
2418 kmemcheck_annotate_bitfield(event, bitfield);
2419 rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
2420
2421 local_inc(&tail_page->entries);
2422
2423 /*
2424 * If this is the first commit on the page, then update
2425 * its timestamp.
2426 */
2427 if (!tail)
2428 tail_page->page->time_stamp = ts;
2429
2430 /* account for these added bytes */
2431 local_add(length, &cpu_buffer->entries_bytes);
2432
2433 return event;
2434}
2435
2436static inline int
2437rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2438 struct ring_buffer_event *event)
2439{
2440 unsigned long new_index, old_index;
2441 struct buffer_page *bpage;
2442 unsigned long index;
2443 unsigned long addr;
2444
2445 new_index = rb_event_index(event);
2446 old_index = new_index + rb_event_ts_length(event);
2447 addr = (unsigned long)event;
2448 addr &= PAGE_MASK;
2449
2450 bpage = cpu_buffer->tail_page;
2451
2452 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2453 unsigned long write_mask =
2454 local_read(&bpage->write) & ~RB_WRITE_MASK;
2455 unsigned long event_length = rb_event_length(event);
2456 /*
2457 * This is on the tail page. It is possible that
2458 * a write could come in and move the tail page
2459 * and write to the next page. That is fine
2460 * because we just shorten what is on this page.
2461 */
2462 old_index += write_mask;
2463 new_index += write_mask;
2464 index = local_cmpxchg(&bpage->write, old_index, new_index);
2465 if (index == old_index) {
2466 /* update counters */
2467 local_sub(event_length, &cpu_buffer->entries_bytes);
2468 return 1;
2469 }
2470 }
2471
2472 /* could not discard */
2473 return 0;
2474}
2475
2476static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2477{
2478 local_inc(&cpu_buffer->committing);
2479 local_inc(&cpu_buffer->commits);
2480}
2481
2482static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2483{
2484 unsigned long commits;
2485
2486 if (RB_WARN_ON(cpu_buffer,
2487 !local_read(&cpu_buffer->committing)))
2488 return;
2489
2490 again:
2491 commits = local_read(&cpu_buffer->commits);
2492 /* synchronize with interrupts */
2493 barrier();
2494 if (local_read(&cpu_buffer->committing) == 1)
2495 rb_set_commit_to_write(cpu_buffer);
2496
2497 local_dec(&cpu_buffer->committing);
2498
2499 /* synchronize with interrupts */
2500 barrier();
2501
2502 /*
2503 * Need to account for interrupts coming in between the
2504 * updating of the commit page and the clearing of the
2505 * committing counter.
2506 */
2507 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2508 !local_read(&cpu_buffer->committing)) {
2509 local_inc(&cpu_buffer->committing);
2510 goto again;
2511 }
2512}
2513
2514static struct ring_buffer_event *
2515rb_reserve_next_event(struct ring_buffer *buffer,
2516 struct ring_buffer_per_cpu *cpu_buffer,
2517 unsigned long length)
2518{
2519 struct ring_buffer_event *event;
2520 u64 ts, delta;
2521 int nr_loops = 0;
2522 int add_timestamp;
2523 u64 diff;
2524
2525 rb_start_commit(cpu_buffer);
2526
2527#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2528 /*
2529 * Due to the ability to swap a cpu buffer from a buffer
2530 * it is possible it was swapped before we committed.
2531 * (committing stops a swap). We check for it here and
2532 * if it happened, we have to fail the write.
2533 */
2534 barrier();
2535 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2536 local_dec(&cpu_buffer->committing);
2537 local_dec(&cpu_buffer->commits);
2538 return NULL;
2539 }
2540#endif
2541
2542 length = rb_calculate_event_length(length);
2543 again:
2544 add_timestamp = 0;
2545 delta = 0;
2546
2547 /*
2548 * We allow for interrupts to reenter here and do a trace.
2549 * If one does, it will cause this original code to loop
2550 * back here. Even with heavy interrupts happening, this
2551 * should only happen a few times in a row. If this happens
2552 * 1000 times in a row, there must be either an interrupt
2553 * storm or we have something buggy.
2554 * Bail!
2555 */
2556 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2557 goto out_fail;
2558
2559 ts = rb_time_stamp(cpu_buffer->buffer);
2560 diff = ts - cpu_buffer->write_stamp;
2561
2562 /* make sure this diff is calculated here */
2563 barrier();
2564
2565 /* Did the write stamp get updated already? */
2566 if (likely(ts >= cpu_buffer->write_stamp)) {
2567 delta = diff;
2568 if (unlikely(test_time_stamp(delta))) {
2569 int local_clock_stable = 1;
2570#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2571 local_clock_stable = sched_clock_stable();
2572#endif
2573 WARN_ONCE(delta > (1ULL << 59),
2574 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2575 (unsigned long long)delta,
2576 (unsigned long long)ts,
2577 (unsigned long long)cpu_buffer->write_stamp,
2578 local_clock_stable ? "" :
2579 "If you just came from a suspend/resume,\n"
2580 "please switch to the trace global clock:\n"
2581 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2582 add_timestamp = 1;
2583 }
2584 }
2585
2586 event = __rb_reserve_next(cpu_buffer, length, ts,
2587 delta, add_timestamp);
2588 if (unlikely(PTR_ERR(event) == -EAGAIN))
2589 goto again;
2590
2591 if (!event)
2592 goto out_fail;
2593
2594 return event;
2595
2596 out_fail:
2597 rb_end_commit(cpu_buffer);
2598 return NULL;
2599}
2600
2601#ifdef CONFIG_TRACING
2602
2603/*
2604 * The lock and unlock are done within a preempt disable section.
2605 * The current_context per_cpu variable can only be modified
2606 * by the current task between lock and unlock. But it can
2607 * be modified more than once via an interrupt. To pass this
2608 * information from the lock to the unlock without having to
2609 * access the 'in_interrupt()' functions again (which do show
2610 * a bit of overhead in something as critical as function tracing,
2611 * we use a bitmask trick.
2612 *
2613 * bit 0 = NMI context
2614 * bit 1 = IRQ context
2615 * bit 2 = SoftIRQ context
2616 * bit 3 = normal context.
2617 *
2618 * This works because this is the order of contexts that can
2619 * preempt other contexts. A SoftIRQ never preempts an IRQ
2620 * context.
2621 *
2622 * When the context is determined, the corresponding bit is
2623 * checked and set (if it was set, then a recursion of that context
2624 * happened).
2625 *
2626 * On unlock, we need to clear this bit. To do so, just subtract
2627 * 1 from the current_context and AND it to itself.
2628 *
2629 * (binary)
2630 * 101 - 1 = 100
2631 * 101 & 100 = 100 (clearing bit zero)
2632 *
2633 * 1010 - 1 = 1001
2634 * 1010 & 1001 = 1000 (clearing bit 1)
2635 *
2636 * The least significant bit can be cleared this way, and it
2637 * just so happens that it is the same bit corresponding to
2638 * the current context.
2639 */
2640static DEFINE_PER_CPU(unsigned int, current_context);
2641
2642static __always_inline int trace_recursive_lock(void)
2643{
2644 unsigned int val = this_cpu_read(current_context);
2645 int bit;
2646
2647 if (in_interrupt()) {
2648 if (in_nmi())
2649 bit = 0;
2650 else if (in_irq())
2651 bit = 1;
2652 else
2653 bit = 2;
2654 } else
2655 bit = 3;
2656
2657 if (unlikely(val & (1 << bit)))
2658 return 1;
2659
2660 val |= (1 << bit);
2661 this_cpu_write(current_context, val);
2662
2663 return 0;
2664}
2665
2666static __always_inline void trace_recursive_unlock(void)
2667{
2668 unsigned int val = this_cpu_read(current_context);
2669
2670 val--;
2671 val &= this_cpu_read(current_context);
2672 this_cpu_write(current_context, val);
2673}
2674
2675#else
2676
2677#define trace_recursive_lock() (0)
2678#define trace_recursive_unlock() do { } while (0)
2679
2680#endif
2681
2682/**
2683 * ring_buffer_lock_reserve - reserve a part of the buffer
2684 * @buffer: the ring buffer to reserve from
2685 * @length: the length of the data to reserve (excluding event header)
2686 *
2687 * Returns a reseverd event on the ring buffer to copy directly to.
2688 * The user of this interface will need to get the body to write into
2689 * and can use the ring_buffer_event_data() interface.
2690 *
2691 * The length is the length of the data needed, not the event length
2692 * which also includes the event header.
2693 *
2694 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2695 * If NULL is returned, then nothing has been allocated or locked.
2696 */
2697struct ring_buffer_event *
2698ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2699{
2700 struct ring_buffer_per_cpu *cpu_buffer;
2701 struct ring_buffer_event *event;
2702 int cpu;
2703
2704 if (ring_buffer_flags != RB_BUFFERS_ON)
2705 return NULL;
2706
2707 /* If we are tracing schedule, we don't want to recurse */
2708 preempt_disable_notrace();
2709
2710 if (atomic_read(&buffer->record_disabled))
2711 goto out_nocheck;
2712
2713 if (trace_recursive_lock())
2714 goto out_nocheck;
2715
2716 cpu = raw_smp_processor_id();
2717
2718 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2719 goto out;
2720
2721 cpu_buffer = buffer->buffers[cpu];
2722
2723 if (atomic_read(&cpu_buffer->record_disabled))
2724 goto out;
2725
2726 if (length > BUF_MAX_DATA_SIZE)
2727 goto out;
2728
2729 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2730 if (!event)
2731 goto out;
2732
2733 return event;
2734
2735 out:
2736 trace_recursive_unlock();
2737
2738 out_nocheck:
2739 preempt_enable_notrace();
2740 return NULL;
2741}
2742EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2743
2744static void
2745rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2746 struct ring_buffer_event *event)
2747{
2748 u64 delta;
2749
2750 /*
2751 * The event first in the commit queue updates the
2752 * time stamp.
2753 */
2754 if (rb_event_is_commit(cpu_buffer, event)) {
2755 /*
2756 * A commit event that is first on a page
2757 * updates the write timestamp with the page stamp
2758 */
2759 if (!rb_event_index(event))
2760 cpu_buffer->write_stamp =
2761 cpu_buffer->commit_page->page->time_stamp;
2762 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2763 delta = event->array[0];
2764 delta <<= TS_SHIFT;
2765 delta += event->time_delta;
2766 cpu_buffer->write_stamp += delta;
2767 } else
2768 cpu_buffer->write_stamp += event->time_delta;
2769 }
2770}
2771
2772static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2773 struct ring_buffer_event *event)
2774{
2775 local_inc(&cpu_buffer->entries);
2776 rb_update_write_stamp(cpu_buffer, event);
2777 rb_end_commit(cpu_buffer);
2778}
2779
2780static __always_inline void
2781rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2782{
2783 if (buffer->irq_work.waiters_pending) {
2784 buffer->irq_work.waiters_pending = false;
2785 /* irq_work_queue() supplies it's own memory barriers */
2786 irq_work_queue(&buffer->irq_work.work);
2787 }
2788
2789 if (cpu_buffer->irq_work.waiters_pending) {
2790 cpu_buffer->irq_work.waiters_pending = false;
2791 /* irq_work_queue() supplies it's own memory barriers */
2792 irq_work_queue(&cpu_buffer->irq_work.work);
2793 }
2794}
2795
2796/**
2797 * ring_buffer_unlock_commit - commit a reserved
2798 * @buffer: The buffer to commit to
2799 * @event: The event pointer to commit.
2800 *
2801 * This commits the data to the ring buffer, and releases any locks held.
2802 *
2803 * Must be paired with ring_buffer_lock_reserve.
2804 */
2805int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2806 struct ring_buffer_event *event)
2807{
2808 struct ring_buffer_per_cpu *cpu_buffer;
2809 int cpu = raw_smp_processor_id();
2810
2811 cpu_buffer = buffer->buffers[cpu];
2812
2813 rb_commit(cpu_buffer, event);
2814
2815 rb_wakeups(buffer, cpu_buffer);
2816
2817 trace_recursive_unlock();
2818
2819 preempt_enable_notrace();
2820
2821 return 0;
2822}
2823EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2824
2825static inline void rb_event_discard(struct ring_buffer_event *event)
2826{
2827 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
2828 event = skip_time_extend(event);
2829
2830 /* array[0] holds the actual length for the discarded event */
2831 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2832 event->type_len = RINGBUF_TYPE_PADDING;
2833 /* time delta must be non zero */
2834 if (!event->time_delta)
2835 event->time_delta = 1;
2836}
2837
2838/*
2839 * Decrement the entries to the page that an event is on.
2840 * The event does not even need to exist, only the pointer
2841 * to the page it is on. This may only be called before the commit
2842 * takes place.
2843 */
2844static inline void
2845rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2846 struct ring_buffer_event *event)
2847{
2848 unsigned long addr = (unsigned long)event;
2849 struct buffer_page *bpage = cpu_buffer->commit_page;
2850 struct buffer_page *start;
2851
2852 addr &= PAGE_MASK;
2853
2854 /* Do the likely case first */
2855 if (likely(bpage->page == (void *)addr)) {
2856 local_dec(&bpage->entries);
2857 return;
2858 }
2859
2860 /*
2861 * Because the commit page may be on the reader page we
2862 * start with the next page and check the end loop there.
2863 */
2864 rb_inc_page(cpu_buffer, &bpage);
2865 start = bpage;
2866 do {
2867 if (bpage->page == (void *)addr) {
2868 local_dec(&bpage->entries);
2869 return;
2870 }
2871 rb_inc_page(cpu_buffer, &bpage);
2872 } while (bpage != start);
2873
2874 /* commit not part of this buffer?? */
2875 RB_WARN_ON(cpu_buffer, 1);
2876}
2877
2878/**
2879 * ring_buffer_commit_discard - discard an event that has not been committed
2880 * @buffer: the ring buffer
2881 * @event: non committed event to discard
2882 *
2883 * Sometimes an event that is in the ring buffer needs to be ignored.
2884 * This function lets the user discard an event in the ring buffer
2885 * and then that event will not be read later.
2886 *
2887 * This function only works if it is called before the the item has been
2888 * committed. It will try to free the event from the ring buffer
2889 * if another event has not been added behind it.
2890 *
2891 * If another event has been added behind it, it will set the event
2892 * up as discarded, and perform the commit.
2893 *
2894 * If this function is called, do not call ring_buffer_unlock_commit on
2895 * the event.
2896 */
2897void ring_buffer_discard_commit(struct ring_buffer *buffer,
2898 struct ring_buffer_event *event)
2899{
2900 struct ring_buffer_per_cpu *cpu_buffer;
2901 int cpu;
2902
2903 /* The event is discarded regardless */
2904 rb_event_discard(event);
2905
2906 cpu = smp_processor_id();
2907 cpu_buffer = buffer->buffers[cpu];
2908
2909 /*
2910 * This must only be called if the event has not been
2911 * committed yet. Thus we can assume that preemption
2912 * is still disabled.
2913 */
2914 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
2915
2916 rb_decrement_entry(cpu_buffer, event);
2917 if (rb_try_to_discard(cpu_buffer, event))
2918 goto out;
2919
2920 /*
2921 * The commit is still visible by the reader, so we
2922 * must still update the timestamp.
2923 */
2924 rb_update_write_stamp(cpu_buffer, event);
2925 out:
2926 rb_end_commit(cpu_buffer);
2927
2928 trace_recursive_unlock();
2929
2930 preempt_enable_notrace();
2931
2932}
2933EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2934
2935/**
2936 * ring_buffer_write - write data to the buffer without reserving
2937 * @buffer: The ring buffer to write to.
2938 * @length: The length of the data being written (excluding the event header)
2939 * @data: The data to write to the buffer.
2940 *
2941 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2942 * one function. If you already have the data to write to the buffer, it
2943 * may be easier to simply call this function.
2944 *
2945 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2946 * and not the length of the event which would hold the header.
2947 */
2948int ring_buffer_write(struct ring_buffer *buffer,
2949 unsigned long length,
2950 void *data)
2951{
2952 struct ring_buffer_per_cpu *cpu_buffer;
2953 struct ring_buffer_event *event;
2954 void *body;
2955 int ret = -EBUSY;
2956 int cpu;
2957
2958 if (ring_buffer_flags != RB_BUFFERS_ON)
2959 return -EBUSY;
2960
2961 preempt_disable_notrace();
2962
2963 if (atomic_read(&buffer->record_disabled))
2964 goto out;
2965
2966 cpu = raw_smp_processor_id();
2967
2968 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2969 goto out;
2970
2971 cpu_buffer = buffer->buffers[cpu];
2972
2973 if (atomic_read(&cpu_buffer->record_disabled))
2974 goto out;
2975
2976 if (length > BUF_MAX_DATA_SIZE)
2977 goto out;
2978
2979 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2980 if (!event)
2981 goto out;
2982
2983 body = rb_event_data(event);
2984
2985 memcpy(body, data, length);
2986
2987 rb_commit(cpu_buffer, event);
2988
2989 rb_wakeups(buffer, cpu_buffer);
2990
2991 ret = 0;
2992 out:
2993 preempt_enable_notrace();
2994
2995 return ret;
2996}
2997EXPORT_SYMBOL_GPL(ring_buffer_write);
2998
2999static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3000{
3001 struct buffer_page *reader = cpu_buffer->reader_page;
3002 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3003 struct buffer_page *commit = cpu_buffer->commit_page;
3004
3005 /* In case of error, head will be NULL */
3006 if (unlikely(!head))
3007 return 1;
3008
3009 return reader->read == rb_page_commit(reader) &&
3010 (commit == reader ||
3011 (commit == head &&
3012 head->read == rb_page_commit(commit)));
3013}
3014
3015/**
3016 * ring_buffer_record_disable - stop all writes into the buffer
3017 * @buffer: The ring buffer to stop writes to.
3018 *
3019 * This prevents all writes to the buffer. Any attempt to write
3020 * to the buffer after this will fail and return NULL.
3021 *
3022 * The caller should call synchronize_sched() after this.
3023 */
3024void ring_buffer_record_disable(struct ring_buffer *buffer)
3025{
3026 atomic_inc(&buffer->record_disabled);
3027}
3028EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3029
3030/**
3031 * ring_buffer_record_enable - enable writes to the buffer
3032 * @buffer: The ring buffer to enable writes
3033 *
3034 * Note, multiple disables will need the same number of enables
3035 * to truly enable the writing (much like preempt_disable).
3036 */
3037void ring_buffer_record_enable(struct ring_buffer *buffer)
3038{
3039 atomic_dec(&buffer->record_disabled);
3040}
3041EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3042
3043/**
3044 * ring_buffer_record_off - stop all writes into the buffer
3045 * @buffer: The ring buffer to stop writes to.
3046 *
3047 * This prevents all writes to the buffer. Any attempt to write
3048 * to the buffer after this will fail and return NULL.
3049 *
3050 * This is different than ring_buffer_record_disable() as
3051 * it works like an on/off switch, where as the disable() version
3052 * must be paired with a enable().
3053 */
3054void ring_buffer_record_off(struct ring_buffer *buffer)
3055{
3056 unsigned int rd;
3057 unsigned int new_rd;
3058
3059 do {
3060 rd = atomic_read(&buffer->record_disabled);
3061 new_rd = rd | RB_BUFFER_OFF;
3062 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3063}
3064EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3065
3066/**
3067 * ring_buffer_record_on - restart writes into the buffer
3068 * @buffer: The ring buffer to start writes to.
3069 *
3070 * This enables all writes to the buffer that was disabled by
3071 * ring_buffer_record_off().
3072 *
3073 * This is different than ring_buffer_record_enable() as
3074 * it works like an on/off switch, where as the enable() version
3075 * must be paired with a disable().
3076 */
3077void ring_buffer_record_on(struct ring_buffer *buffer)
3078{
3079 unsigned int rd;
3080 unsigned int new_rd;
3081
3082 do {
3083 rd = atomic_read(&buffer->record_disabled);
3084 new_rd = rd & ~RB_BUFFER_OFF;
3085 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3086}
3087EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3088
3089/**
3090 * ring_buffer_record_is_on - return true if the ring buffer can write
3091 * @buffer: The ring buffer to see if write is enabled
3092 *
3093 * Returns true if the ring buffer is in a state that it accepts writes.
3094 */
3095int ring_buffer_record_is_on(struct ring_buffer *buffer)
3096{
3097 return !atomic_read(&buffer->record_disabled);
3098}
3099
3100/**
3101 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3102 * @buffer: The ring buffer to stop writes to.
3103 * @cpu: The CPU buffer to stop
3104 *
3105 * This prevents all writes to the buffer. Any attempt to write
3106 * to the buffer after this will fail and return NULL.
3107 *
3108 * The caller should call synchronize_sched() after this.
3109 */
3110void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3111{
3112 struct ring_buffer_per_cpu *cpu_buffer;
3113
3114 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3115 return;
3116
3117 cpu_buffer = buffer->buffers[cpu];
3118 atomic_inc(&cpu_buffer->record_disabled);
3119}
3120EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3121
3122/**
3123 * ring_buffer_record_enable_cpu - enable writes to the buffer
3124 * @buffer: The ring buffer to enable writes
3125 * @cpu: The CPU to enable.
3126 *
3127 * Note, multiple disables will need the same number of enables
3128 * to truly enable the writing (much like preempt_disable).
3129 */
3130void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3131{
3132 struct ring_buffer_per_cpu *cpu_buffer;
3133
3134 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3135 return;
3136
3137 cpu_buffer = buffer->buffers[cpu];
3138 atomic_dec(&cpu_buffer->record_disabled);
3139}
3140EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3141
3142/*
3143 * The total entries in the ring buffer is the running counter
3144 * of entries entered into the ring buffer, minus the sum of
3145 * the entries read from the ring buffer and the number of
3146 * entries that were overwritten.
3147 */
3148static inline unsigned long
3149rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3150{
3151 return local_read(&cpu_buffer->entries) -
3152 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3153}
3154
3155/**
3156 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3157 * @buffer: The ring buffer
3158 * @cpu: The per CPU buffer to read from.
3159 */
3160u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3161{
3162 unsigned long flags;
3163 struct ring_buffer_per_cpu *cpu_buffer;
3164 struct buffer_page *bpage;
3165 u64 ret = 0;
3166
3167 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3168 return 0;
3169
3170 cpu_buffer = buffer->buffers[cpu];
3171 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3172 /*
3173 * if the tail is on reader_page, oldest time stamp is on the reader
3174 * page
3175 */
3176 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3177 bpage = cpu_buffer->reader_page;
3178 else
3179 bpage = rb_set_head_page(cpu_buffer);
3180 if (bpage)
3181 ret = bpage->page->time_stamp;
3182 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3183
3184 return ret;
3185}
3186EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3187
3188/**
3189 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3190 * @buffer: The ring buffer
3191 * @cpu: The per CPU buffer to read from.
3192 */
3193unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3194{
3195 struct ring_buffer_per_cpu *cpu_buffer;
3196 unsigned long ret;
3197
3198 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3199 return 0;
3200
3201 cpu_buffer = buffer->buffers[cpu];
3202 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3203
3204 return ret;
3205}
3206EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3207
3208/**
3209 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3210 * @buffer: The ring buffer
3211 * @cpu: The per CPU buffer to get the entries from.
3212 */
3213unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3214{
3215 struct ring_buffer_per_cpu *cpu_buffer;
3216
3217 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3218 return 0;
3219
3220 cpu_buffer = buffer->buffers[cpu];
3221
3222 return rb_num_of_entries(cpu_buffer);
3223}
3224EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3225
3226/**
3227 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3228 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3229 * @buffer: The ring buffer
3230 * @cpu: The per CPU buffer to get the number of overruns from
3231 */
3232unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3233{
3234 struct ring_buffer_per_cpu *cpu_buffer;
3235 unsigned long ret;
3236
3237 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3238 return 0;
3239
3240 cpu_buffer = buffer->buffers[cpu];
3241 ret = local_read(&cpu_buffer->overrun);
3242
3243 return ret;
3244}
3245EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3246
3247/**
3248 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3249 * commits failing due to the buffer wrapping around while there are uncommitted
3250 * events, such as during an interrupt storm.
3251 * @buffer: The ring buffer
3252 * @cpu: The per CPU buffer to get the number of overruns from
3253 */
3254unsigned long
3255ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3256{
3257 struct ring_buffer_per_cpu *cpu_buffer;
3258 unsigned long ret;
3259
3260 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3261 return 0;
3262
3263 cpu_buffer = buffer->buffers[cpu];
3264 ret = local_read(&cpu_buffer->commit_overrun);
3265
3266 return ret;
3267}
3268EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3269
3270/**
3271 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3272 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3273 * @buffer: The ring buffer
3274 * @cpu: The per CPU buffer to get the number of overruns from
3275 */
3276unsigned long
3277ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3278{
3279 struct ring_buffer_per_cpu *cpu_buffer;
3280 unsigned long ret;
3281
3282 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3283 return 0;
3284
3285 cpu_buffer = buffer->buffers[cpu];
3286 ret = local_read(&cpu_buffer->dropped_events);
3287
3288 return ret;
3289}
3290EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3291
3292/**
3293 * ring_buffer_read_events_cpu - get the number of events successfully read
3294 * @buffer: The ring buffer
3295 * @cpu: The per CPU buffer to get the number of events read
3296 */
3297unsigned long
3298ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3299{
3300 struct ring_buffer_per_cpu *cpu_buffer;
3301
3302 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3303 return 0;
3304
3305 cpu_buffer = buffer->buffers[cpu];
3306 return cpu_buffer->read;
3307}
3308EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3309
3310/**
3311 * ring_buffer_entries - get the number of entries in a buffer
3312 * @buffer: The ring buffer
3313 *
3314 * Returns the total number of entries in the ring buffer
3315 * (all CPU entries)
3316 */
3317unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3318{
3319 struct ring_buffer_per_cpu *cpu_buffer;
3320 unsigned long entries = 0;
3321 int cpu;
3322
3323 /* if you care about this being correct, lock the buffer */
3324 for_each_buffer_cpu(buffer, cpu) {
3325 cpu_buffer = buffer->buffers[cpu];
3326 entries += rb_num_of_entries(cpu_buffer);
3327 }
3328
3329 return entries;
3330}
3331EXPORT_SYMBOL_GPL(ring_buffer_entries);
3332
3333/**
3334 * ring_buffer_overruns - get the number of overruns in buffer
3335 * @buffer: The ring buffer
3336 *
3337 * Returns the total number of overruns in the ring buffer
3338 * (all CPU entries)
3339 */
3340unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3341{
3342 struct ring_buffer_per_cpu *cpu_buffer;
3343 unsigned long overruns = 0;
3344 int cpu;
3345
3346 /* if you care about this being correct, lock the buffer */
3347 for_each_buffer_cpu(buffer, cpu) {
3348 cpu_buffer = buffer->buffers[cpu];
3349 overruns += local_read(&cpu_buffer->overrun);
3350 }
3351
3352 return overruns;
3353}
3354EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3355
3356static void rb_iter_reset(struct ring_buffer_iter *iter)
3357{
3358 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3359
3360 /* Iterator usage is expected to have record disabled */
3361 if (list_empty(&cpu_buffer->reader_page->list)) {
3362 iter->head_page = rb_set_head_page(cpu_buffer);
3363 if (unlikely(!iter->head_page))
3364 return;
3365 iter->head = iter->head_page->read;
3366 } else {
3367 iter->head_page = cpu_buffer->reader_page;
3368 iter->head = cpu_buffer->reader_page->read;
3369 }
3370 if (iter->head)
3371 iter->read_stamp = cpu_buffer->read_stamp;
3372 else
3373 iter->read_stamp = iter->head_page->page->time_stamp;
3374 iter->cache_reader_page = cpu_buffer->reader_page;
3375 iter->cache_read = cpu_buffer->read;
3376}
3377
3378/**
3379 * ring_buffer_iter_reset - reset an iterator
3380 * @iter: The iterator to reset
3381 *
3382 * Resets the iterator, so that it will start from the beginning
3383 * again.
3384 */
3385void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3386{
3387 struct ring_buffer_per_cpu *cpu_buffer;
3388 unsigned long flags;
3389
3390 if (!iter)
3391 return;
3392
3393 cpu_buffer = iter->cpu_buffer;
3394
3395 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3396 rb_iter_reset(iter);
3397 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3398}
3399EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3400
3401/**
3402 * ring_buffer_iter_empty - check if an iterator has no more to read
3403 * @iter: The iterator to check
3404 */
3405int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3406{
3407 struct ring_buffer_per_cpu *cpu_buffer;
3408
3409 cpu_buffer = iter->cpu_buffer;
3410
3411 return iter->head_page == cpu_buffer->commit_page &&
3412 iter->head == rb_commit_index(cpu_buffer);
3413}
3414EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3415
3416static void
3417rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3418 struct ring_buffer_event *event)
3419{
3420 u64 delta;
3421
3422 switch (event->type_len) {
3423 case RINGBUF_TYPE_PADDING:
3424 return;
3425
3426 case RINGBUF_TYPE_TIME_EXTEND:
3427 delta = event->array[0];
3428 delta <<= TS_SHIFT;
3429 delta += event->time_delta;
3430 cpu_buffer->read_stamp += delta;
3431 return;
3432
3433 case RINGBUF_TYPE_TIME_STAMP:
3434 /* FIXME: not implemented */
3435 return;
3436
3437 case RINGBUF_TYPE_DATA:
3438 cpu_buffer->read_stamp += event->time_delta;
3439 return;
3440
3441 default:
3442 BUG();
3443 }
3444 return;
3445}
3446
3447static void
3448rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3449 struct ring_buffer_event *event)
3450{
3451 u64 delta;
3452
3453 switch (event->type_len) {
3454 case RINGBUF_TYPE_PADDING:
3455 return;
3456
3457 case RINGBUF_TYPE_TIME_EXTEND:
3458 delta = event->array[0];
3459 delta <<= TS_SHIFT;
3460 delta += event->time_delta;
3461 iter->read_stamp += delta;
3462 return;
3463
3464 case RINGBUF_TYPE_TIME_STAMP:
3465 /* FIXME: not implemented */
3466 return;
3467
3468 case RINGBUF_TYPE_DATA:
3469 iter->read_stamp += event->time_delta;
3470 return;
3471
3472 default:
3473 BUG();
3474 }
3475 return;
3476}
3477
3478static struct buffer_page *
3479rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3480{
3481 struct buffer_page *reader = NULL;
3482 unsigned long overwrite;
3483 unsigned long flags;
3484 int nr_loops = 0;
3485 int ret;
3486
3487 local_irq_save(flags);
3488 arch_spin_lock(&cpu_buffer->lock);
3489
3490 again:
3491 /*
3492 * This should normally only loop twice. But because the
3493 * start of the reader inserts an empty page, it causes
3494 * a case where we will loop three times. There should be no
3495 * reason to loop four times (that I know of).
3496 */
3497 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3498 reader = NULL;
3499 goto out;
3500 }
3501
3502 reader = cpu_buffer->reader_page;
3503
3504 /* If there's more to read, return this page */
3505 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3506 goto out;
3507
3508 /* Never should we have an index greater than the size */
3509 if (RB_WARN_ON(cpu_buffer,
3510 cpu_buffer->reader_page->read > rb_page_size(reader)))
3511 goto out;
3512
3513 /* check if we caught up to the tail */
3514 reader = NULL;
3515 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3516 goto out;
3517
3518 /* Don't bother swapping if the ring buffer is empty */
3519 if (rb_num_of_entries(cpu_buffer) == 0)
3520 goto out;
3521
3522 /*
3523 * Reset the reader page to size zero.
3524 */
3525 local_set(&cpu_buffer->reader_page->write, 0);
3526 local_set(&cpu_buffer->reader_page->entries, 0);
3527 local_set(&cpu_buffer->reader_page->page->commit, 0);
3528 cpu_buffer->reader_page->real_end = 0;
3529
3530 spin:
3531 /*
3532 * Splice the empty reader page into the list around the head.
3533 */
3534 reader = rb_set_head_page(cpu_buffer);
3535 if (!reader)
3536 goto out;
3537 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3538 cpu_buffer->reader_page->list.prev = reader->list.prev;
3539
3540 /*
3541 * cpu_buffer->pages just needs to point to the buffer, it
3542 * has no specific buffer page to point to. Lets move it out
3543 * of our way so we don't accidentally swap it.
3544 */
3545 cpu_buffer->pages = reader->list.prev;
3546
3547 /* The reader page will be pointing to the new head */
3548 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3549
3550 /*
3551 * We want to make sure we read the overruns after we set up our
3552 * pointers to the next object. The writer side does a
3553 * cmpxchg to cross pages which acts as the mb on the writer
3554 * side. Note, the reader will constantly fail the swap
3555 * while the writer is updating the pointers, so this
3556 * guarantees that the overwrite recorded here is the one we
3557 * want to compare with the last_overrun.
3558 */
3559 smp_mb();
3560 overwrite = local_read(&(cpu_buffer->overrun));
3561
3562 /*
3563 * Here's the tricky part.
3564 *
3565 * We need to move the pointer past the header page.
3566 * But we can only do that if a writer is not currently
3567 * moving it. The page before the header page has the
3568 * flag bit '1' set if it is pointing to the page we want.
3569 * but if the writer is in the process of moving it
3570 * than it will be '2' or already moved '0'.
3571 */
3572
3573 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3574
3575 /*
3576 * If we did not convert it, then we must try again.
3577 */
3578 if (!ret)
3579 goto spin;
3580
3581 /*
3582 * Yeah! We succeeded in replacing the page.
3583 *
3584 * Now make the new head point back to the reader page.
3585 */
3586 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3587 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3588
3589 /* Finally update the reader page to the new head */
3590 cpu_buffer->reader_page = reader;
3591 rb_reset_reader_page(cpu_buffer);
3592
3593 if (overwrite != cpu_buffer->last_overrun) {
3594 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3595 cpu_buffer->last_overrun = overwrite;
3596 }
3597
3598 goto again;
3599
3600 out:
3601 arch_spin_unlock(&cpu_buffer->lock);
3602 local_irq_restore(flags);
3603
3604 return reader;
3605}
3606
3607static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3608{
3609 struct ring_buffer_event *event;
3610 struct buffer_page *reader;
3611 unsigned length;
3612
3613 reader = rb_get_reader_page(cpu_buffer);
3614
3615 /* This function should not be called when buffer is empty */
3616 if (RB_WARN_ON(cpu_buffer, !reader))
3617 return;
3618
3619 event = rb_reader_event(cpu_buffer);
3620
3621 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3622 cpu_buffer->read++;
3623
3624 rb_update_read_stamp(cpu_buffer, event);
3625
3626 length = rb_event_length(event);
3627 cpu_buffer->reader_page->read += length;
3628}
3629
3630static void rb_advance_iter(struct ring_buffer_iter *iter)
3631{
3632 struct ring_buffer_per_cpu *cpu_buffer;
3633 struct ring_buffer_event *event;
3634 unsigned length;
3635
3636 cpu_buffer = iter->cpu_buffer;
3637
3638 /*
3639 * Check if we are at the end of the buffer.
3640 */
3641 if (iter->head >= rb_page_size(iter->head_page)) {
3642 /* discarded commits can make the page empty */
3643 if (iter->head_page == cpu_buffer->commit_page)
3644 return;
3645 rb_inc_iter(iter);
3646 return;
3647 }
3648
3649 event = rb_iter_head_event(iter);
3650
3651 length = rb_event_length(event);
3652
3653 /*
3654 * This should not be called to advance the header if we are
3655 * at the tail of the buffer.
3656 */
3657 if (RB_WARN_ON(cpu_buffer,
3658 (iter->head_page == cpu_buffer->commit_page) &&
3659 (iter->head + length > rb_commit_index(cpu_buffer))))
3660 return;
3661
3662 rb_update_iter_read_stamp(iter, event);
3663
3664 iter->head += length;
3665
3666 /* check for end of page padding */
3667 if ((iter->head >= rb_page_size(iter->head_page)) &&
3668 (iter->head_page != cpu_buffer->commit_page))
3669 rb_inc_iter(iter);
3670}
3671
3672static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3673{
3674 return cpu_buffer->lost_events;
3675}
3676
3677static struct ring_buffer_event *
3678rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3679 unsigned long *lost_events)
3680{
3681 struct ring_buffer_event *event;
3682 struct buffer_page *reader;
3683 int nr_loops = 0;
3684
3685 again:
3686 /*
3687 * We repeat when a time extend is encountered.
3688 * Since the time extend is always attached to a data event,
3689 * we should never loop more than once.
3690 * (We never hit the following condition more than twice).
3691 */
3692 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3693 return NULL;
3694
3695 reader = rb_get_reader_page(cpu_buffer);
3696 if (!reader)
3697 return NULL;
3698
3699 event = rb_reader_event(cpu_buffer);
3700
3701 switch (event->type_len) {
3702 case RINGBUF_TYPE_PADDING:
3703 if (rb_null_event(event))
3704 RB_WARN_ON(cpu_buffer, 1);
3705 /*
3706 * Because the writer could be discarding every
3707 * event it creates (which would probably be bad)
3708 * if we were to go back to "again" then we may never
3709 * catch up, and will trigger the warn on, or lock
3710 * the box. Return the padding, and we will release
3711 * the current locks, and try again.
3712 */
3713 return event;
3714
3715 case RINGBUF_TYPE_TIME_EXTEND:
3716 /* Internal data, OK to advance */
3717 rb_advance_reader(cpu_buffer);
3718 goto again;
3719
3720 case RINGBUF_TYPE_TIME_STAMP:
3721 /* FIXME: not implemented */
3722 rb_advance_reader(cpu_buffer);
3723 goto again;
3724
3725 case RINGBUF_TYPE_DATA:
3726 if (ts) {
3727 *ts = cpu_buffer->read_stamp + event->time_delta;
3728 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3729 cpu_buffer->cpu, ts);
3730 }
3731 if (lost_events)
3732 *lost_events = rb_lost_events(cpu_buffer);
3733 return event;
3734
3735 default:
3736 BUG();
3737 }
3738
3739 return NULL;
3740}
3741EXPORT_SYMBOL_GPL(ring_buffer_peek);
3742
3743static struct ring_buffer_event *
3744rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3745{
3746 struct ring_buffer *buffer;
3747 struct ring_buffer_per_cpu *cpu_buffer;
3748 struct ring_buffer_event *event;
3749 int nr_loops = 0;
3750
3751 cpu_buffer = iter->cpu_buffer;
3752 buffer = cpu_buffer->buffer;
3753
3754 /*
3755 * Check if someone performed a consuming read to
3756 * the buffer. A consuming read invalidates the iterator
3757 * and we need to reset the iterator in this case.
3758 */
3759 if (unlikely(iter->cache_read != cpu_buffer->read ||
3760 iter->cache_reader_page != cpu_buffer->reader_page))
3761 rb_iter_reset(iter);
3762
3763 again:
3764 if (ring_buffer_iter_empty(iter))
3765 return NULL;
3766
3767 /*
3768 * We repeat when a time extend is encountered.
3769 * Since the time extend is always attached to a data event,
3770 * we should never loop more than once.
3771 * (We never hit the following condition more than twice).
3772 */
3773 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3774 return NULL;
3775
3776 if (rb_per_cpu_empty(cpu_buffer))
3777 return NULL;
3778
3779 if (iter->head >= local_read(&iter->head_page->page->commit)) {
3780 rb_inc_iter(iter);
3781 goto again;
3782 }
3783
3784 event = rb_iter_head_event(iter);
3785
3786 switch (event->type_len) {
3787 case RINGBUF_TYPE_PADDING:
3788 if (rb_null_event(event)) {
3789 rb_inc_iter(iter);
3790 goto again;
3791 }
3792 rb_advance_iter(iter);
3793 return event;
3794
3795 case RINGBUF_TYPE_TIME_EXTEND:
3796 /* Internal data, OK to advance */
3797 rb_advance_iter(iter);
3798 goto again;
3799
3800 case RINGBUF_TYPE_TIME_STAMP:
3801 /* FIXME: not implemented */
3802 rb_advance_iter(iter);
3803 goto again;
3804
3805 case RINGBUF_TYPE_DATA:
3806 if (ts) {
3807 *ts = iter->read_stamp + event->time_delta;
3808 ring_buffer_normalize_time_stamp(buffer,
3809 cpu_buffer->cpu, ts);
3810 }
3811 return event;
3812
3813 default:
3814 BUG();
3815 }
3816
3817 return NULL;
3818}
3819EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3820
3821static inline int rb_ok_to_lock(void)
3822{
3823 /*
3824 * If an NMI die dumps out the content of the ring buffer
3825 * do not grab locks. We also permanently disable the ring
3826 * buffer too. A one time deal is all you get from reading
3827 * the ring buffer from an NMI.
3828 */
3829 if (likely(!in_nmi()))
3830 return 1;
3831
3832 tracing_off_permanent();
3833 return 0;
3834}
3835
3836/**
3837 * ring_buffer_peek - peek at the next event to be read
3838 * @buffer: The ring buffer to read
3839 * @cpu: The cpu to peak at
3840 * @ts: The timestamp counter of this event.
3841 * @lost_events: a variable to store if events were lost (may be NULL)
3842 *
3843 * This will return the event that will be read next, but does
3844 * not consume the data.
3845 */
3846struct ring_buffer_event *
3847ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
3848 unsigned long *lost_events)
3849{
3850 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3851 struct ring_buffer_event *event;
3852 unsigned long flags;
3853 int dolock;
3854
3855 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3856 return NULL;
3857
3858 dolock = rb_ok_to_lock();
3859 again:
3860 local_irq_save(flags);
3861 if (dolock)
3862 raw_spin_lock(&cpu_buffer->reader_lock);
3863 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3864 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3865 rb_advance_reader(cpu_buffer);
3866 if (dolock)
3867 raw_spin_unlock(&cpu_buffer->reader_lock);
3868 local_irq_restore(flags);
3869
3870 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3871 goto again;
3872
3873 return event;
3874}
3875
3876/**
3877 * ring_buffer_iter_peek - peek at the next event to be read
3878 * @iter: The ring buffer iterator
3879 * @ts: The timestamp counter of this event.
3880 *
3881 * This will return the event that will be read next, but does
3882 * not increment the iterator.
3883 */
3884struct ring_buffer_event *
3885ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3886{
3887 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3888 struct ring_buffer_event *event;
3889 unsigned long flags;
3890
3891 again:
3892 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3893 event = rb_iter_peek(iter, ts);
3894 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3895
3896 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3897 goto again;
3898
3899 return event;
3900}
3901
3902/**
3903 * ring_buffer_consume - return an event and consume it
3904 * @buffer: The ring buffer to get the next event from
3905 * @cpu: the cpu to read the buffer from
3906 * @ts: a variable to store the timestamp (may be NULL)
3907 * @lost_events: a variable to store if events were lost (may be NULL)
3908 *
3909 * Returns the next event in the ring buffer, and that event is consumed.
3910 * Meaning, that sequential reads will keep returning a different event,
3911 * and eventually empty the ring buffer if the producer is slower.
3912 */
3913struct ring_buffer_event *
3914ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
3915 unsigned long *lost_events)
3916{
3917 struct ring_buffer_per_cpu *cpu_buffer;
3918 struct ring_buffer_event *event = NULL;
3919 unsigned long flags;
3920 int dolock;
3921
3922 dolock = rb_ok_to_lock();
3923
3924 again:
3925 /* might be called in atomic */
3926 preempt_disable();
3927
3928 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3929 goto out;
3930
3931 cpu_buffer = buffer->buffers[cpu];
3932 local_irq_save(flags);
3933 if (dolock)
3934 raw_spin_lock(&cpu_buffer->reader_lock);
3935
3936 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3937 if (event) {
3938 cpu_buffer->lost_events = 0;
3939 rb_advance_reader(cpu_buffer);
3940 }
3941
3942 if (dolock)
3943 raw_spin_unlock(&cpu_buffer->reader_lock);
3944 local_irq_restore(flags);
3945
3946 out:
3947 preempt_enable();
3948
3949 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3950 goto again;
3951
3952 return event;
3953}
3954EXPORT_SYMBOL_GPL(ring_buffer_consume);
3955
3956/**
3957 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3958 * @buffer: The ring buffer to read from
3959 * @cpu: The cpu buffer to iterate over
3960 *
3961 * This performs the initial preparations necessary to iterate
3962 * through the buffer. Memory is allocated, buffer recording
3963 * is disabled, and the iterator pointer is returned to the caller.
3964 *
3965 * Disabling buffer recordng prevents the reading from being
3966 * corrupted. This is not a consuming read, so a producer is not
3967 * expected.
3968 *
3969 * After a sequence of ring_buffer_read_prepare calls, the user is
3970 * expected to make at least one call to ring_buffer_read_prepare_sync.
3971 * Afterwards, ring_buffer_read_start is invoked to get things going
3972 * for real.
3973 *
3974 * This overall must be paired with ring_buffer_read_finish.
3975 */
3976struct ring_buffer_iter *
3977ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
3978{
3979 struct ring_buffer_per_cpu *cpu_buffer;
3980 struct ring_buffer_iter *iter;
3981
3982 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3983 return NULL;
3984
3985 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
3986 if (!iter)
3987 return NULL;
3988
3989 cpu_buffer = buffer->buffers[cpu];
3990
3991 iter->cpu_buffer = cpu_buffer;
3992
3993 atomic_inc(&buffer->resize_disabled);
3994 atomic_inc(&cpu_buffer->record_disabled);
3995
3996 return iter;
3997}
3998EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
3999
4000/**
4001 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4002 *
4003 * All previously invoked ring_buffer_read_prepare calls to prepare
4004 * iterators will be synchronized. Afterwards, read_buffer_read_start
4005 * calls on those iterators are allowed.
4006 */
4007void
4008ring_buffer_read_prepare_sync(void)
4009{
4010 synchronize_sched();
4011}
4012EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4013
4014/**
4015 * ring_buffer_read_start - start a non consuming read of the buffer
4016 * @iter: The iterator returned by ring_buffer_read_prepare
4017 *
4018 * This finalizes the startup of an iteration through the buffer.
4019 * The iterator comes from a call to ring_buffer_read_prepare and
4020 * an intervening ring_buffer_read_prepare_sync must have been
4021 * performed.
4022 *
4023 * Must be paired with ring_buffer_read_finish.
4024 */
4025void
4026ring_buffer_read_start(struct ring_buffer_iter *iter)
4027{
4028 struct ring_buffer_per_cpu *cpu_buffer;
4029 unsigned long flags;
4030
4031 if (!iter)
4032 return;
4033
4034 cpu_buffer = iter->cpu_buffer;
4035
4036 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4037 arch_spin_lock(&cpu_buffer->lock);
4038 rb_iter_reset(iter);
4039 arch_spin_unlock(&cpu_buffer->lock);
4040 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4041}
4042EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4043
4044/**
4045 * ring_buffer_read_finish - finish reading the iterator of the buffer
4046 * @iter: The iterator retrieved by ring_buffer_start
4047 *
4048 * This re-enables the recording to the buffer, and frees the
4049 * iterator.
4050 */
4051void
4052ring_buffer_read_finish(struct ring_buffer_iter *iter)
4053{
4054 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4055 unsigned long flags;
4056
4057 /*
4058 * Ring buffer is disabled from recording, here's a good place
4059 * to check the integrity of the ring buffer.
4060 * Must prevent readers from trying to read, as the check
4061 * clears the HEAD page and readers require it.
4062 */
4063 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4064 rb_check_pages(cpu_buffer);
4065 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4066
4067 atomic_dec(&cpu_buffer->record_disabled);
4068 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4069 kfree(iter);
4070}
4071EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4072
4073/**
4074 * ring_buffer_read - read the next item in the ring buffer by the iterator
4075 * @iter: The ring buffer iterator
4076 * @ts: The time stamp of the event read.
4077 *
4078 * This reads the next event in the ring buffer and increments the iterator.
4079 */
4080struct ring_buffer_event *
4081ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4082{
4083 struct ring_buffer_event *event;
4084 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4085 unsigned long flags;
4086
4087 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4088 again:
4089 event = rb_iter_peek(iter, ts);
4090 if (!event)
4091 goto out;
4092
4093 if (event->type_len == RINGBUF_TYPE_PADDING)
4094 goto again;
4095
4096 rb_advance_iter(iter);
4097 out:
4098 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4099
4100 return event;
4101}
4102EXPORT_SYMBOL_GPL(ring_buffer_read);
4103
4104/**
4105 * ring_buffer_size - return the size of the ring buffer (in bytes)
4106 * @buffer: The ring buffer.
4107 */
4108unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4109{
4110 /*
4111 * Earlier, this method returned
4112 * BUF_PAGE_SIZE * buffer->nr_pages
4113 * Since the nr_pages field is now removed, we have converted this to
4114 * return the per cpu buffer value.
4115 */
4116 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4117 return 0;
4118
4119 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4120}
4121EXPORT_SYMBOL_GPL(ring_buffer_size);
4122
4123static void
4124rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4125{
4126 rb_head_page_deactivate(cpu_buffer);
4127
4128 cpu_buffer->head_page
4129 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4130 local_set(&cpu_buffer->head_page->write, 0);
4131 local_set(&cpu_buffer->head_page->entries, 0);
4132 local_set(&cpu_buffer->head_page->page->commit, 0);
4133
4134 cpu_buffer->head_page->read = 0;
4135
4136 cpu_buffer->tail_page = cpu_buffer->head_page;
4137 cpu_buffer->commit_page = cpu_buffer->head_page;
4138
4139 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4140 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4141 local_set(&cpu_buffer->reader_page->write, 0);
4142 local_set(&cpu_buffer->reader_page->entries, 0);
4143 local_set(&cpu_buffer->reader_page->page->commit, 0);
4144 cpu_buffer->reader_page->read = 0;
4145
4146 local_set(&cpu_buffer->entries_bytes, 0);
4147 local_set(&cpu_buffer->overrun, 0);
4148 local_set(&cpu_buffer->commit_overrun, 0);
4149 local_set(&cpu_buffer->dropped_events, 0);
4150 local_set(&cpu_buffer->entries, 0);
4151 local_set(&cpu_buffer->committing, 0);
4152 local_set(&cpu_buffer->commits, 0);
4153 cpu_buffer->read = 0;
4154 cpu_buffer->read_bytes = 0;
4155
4156 cpu_buffer->write_stamp = 0;
4157 cpu_buffer->read_stamp = 0;
4158
4159 cpu_buffer->lost_events = 0;
4160 cpu_buffer->last_overrun = 0;
4161
4162 rb_head_page_activate(cpu_buffer);
4163}
4164
4165/**
4166 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4167 * @buffer: The ring buffer to reset a per cpu buffer of
4168 * @cpu: The CPU buffer to be reset
4169 */
4170void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4171{
4172 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4173 unsigned long flags;
4174
4175 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4176 return;
4177
4178 atomic_inc(&buffer->resize_disabled);
4179 atomic_inc(&cpu_buffer->record_disabled);
4180
4181 /* Make sure all commits have finished */
4182 synchronize_sched();
4183
4184 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4185
4186 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4187 goto out;
4188
4189 arch_spin_lock(&cpu_buffer->lock);
4190
4191 rb_reset_cpu(cpu_buffer);
4192
4193 arch_spin_unlock(&cpu_buffer->lock);
4194
4195 out:
4196 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4197
4198 atomic_dec(&cpu_buffer->record_disabled);
4199 atomic_dec(&buffer->resize_disabled);
4200}
4201EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4202
4203/**
4204 * ring_buffer_reset - reset a ring buffer
4205 * @buffer: The ring buffer to reset all cpu buffers
4206 */
4207void ring_buffer_reset(struct ring_buffer *buffer)
4208{
4209 int cpu;
4210
4211 for_each_buffer_cpu(buffer, cpu)
4212 ring_buffer_reset_cpu(buffer, cpu);
4213}
4214EXPORT_SYMBOL_GPL(ring_buffer_reset);
4215
4216/**
4217 * rind_buffer_empty - is the ring buffer empty?
4218 * @buffer: The ring buffer to test
4219 */
4220int ring_buffer_empty(struct ring_buffer *buffer)
4221{
4222 struct ring_buffer_per_cpu *cpu_buffer;
4223 unsigned long flags;
4224 int dolock;
4225 int cpu;
4226 int ret;
4227
4228 dolock = rb_ok_to_lock();
4229
4230 /* yes this is racy, but if you don't like the race, lock the buffer */
4231 for_each_buffer_cpu(buffer, cpu) {
4232 cpu_buffer = buffer->buffers[cpu];
4233 local_irq_save(flags);
4234 if (dolock)
4235 raw_spin_lock(&cpu_buffer->reader_lock);
4236 ret = rb_per_cpu_empty(cpu_buffer);
4237 if (dolock)
4238 raw_spin_unlock(&cpu_buffer->reader_lock);
4239 local_irq_restore(flags);
4240
4241 if (!ret)
4242 return 0;
4243 }
4244
4245 return 1;
4246}
4247EXPORT_SYMBOL_GPL(ring_buffer_empty);
4248
4249/**
4250 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4251 * @buffer: The ring buffer
4252 * @cpu: The CPU buffer to test
4253 */
4254int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4255{
4256 struct ring_buffer_per_cpu *cpu_buffer;
4257 unsigned long flags;
4258 int dolock;
4259 int ret;
4260
4261 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4262 return 1;
4263
4264 dolock = rb_ok_to_lock();
4265
4266 cpu_buffer = buffer->buffers[cpu];
4267 local_irq_save(flags);
4268 if (dolock)
4269 raw_spin_lock(&cpu_buffer->reader_lock);
4270 ret = rb_per_cpu_empty(cpu_buffer);
4271 if (dolock)
4272 raw_spin_unlock(&cpu_buffer->reader_lock);
4273 local_irq_restore(flags);
4274
4275 return ret;
4276}
4277EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4278
4279#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4280/**
4281 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4282 * @buffer_a: One buffer to swap with
4283 * @buffer_b: The other buffer to swap with
4284 *
4285 * This function is useful for tracers that want to take a "snapshot"
4286 * of a CPU buffer and has another back up buffer lying around.
4287 * it is expected that the tracer handles the cpu buffer not being
4288 * used at the moment.
4289 */
4290int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4291 struct ring_buffer *buffer_b, int cpu)
4292{
4293 struct ring_buffer_per_cpu *cpu_buffer_a;
4294 struct ring_buffer_per_cpu *cpu_buffer_b;
4295 int ret = -EINVAL;
4296
4297 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4298 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4299 goto out;
4300
4301 cpu_buffer_a = buffer_a->buffers[cpu];
4302 cpu_buffer_b = buffer_b->buffers[cpu];
4303
4304 /* At least make sure the two buffers are somewhat the same */
4305 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4306 goto out;
4307
4308 ret = -EAGAIN;
4309
4310 if (ring_buffer_flags != RB_BUFFERS_ON)
4311 goto out;
4312
4313 if (atomic_read(&buffer_a->record_disabled))
4314 goto out;
4315
4316 if (atomic_read(&buffer_b->record_disabled))
4317 goto out;
4318
4319 if (atomic_read(&cpu_buffer_a->record_disabled))
4320 goto out;
4321
4322 if (atomic_read(&cpu_buffer_b->record_disabled))
4323 goto out;
4324
4325 /*
4326 * We can't do a synchronize_sched here because this
4327 * function can be called in atomic context.
4328 * Normally this will be called from the same CPU as cpu.
4329 * If not it's up to the caller to protect this.
4330 */
4331 atomic_inc(&cpu_buffer_a->record_disabled);
4332 atomic_inc(&cpu_buffer_b->record_disabled);
4333
4334 ret = -EBUSY;
4335 if (local_read(&cpu_buffer_a->committing))
4336 goto out_dec;
4337 if (local_read(&cpu_buffer_b->committing))
4338 goto out_dec;
4339
4340 buffer_a->buffers[cpu] = cpu_buffer_b;
4341 buffer_b->buffers[cpu] = cpu_buffer_a;
4342
4343 cpu_buffer_b->buffer = buffer_a;
4344 cpu_buffer_a->buffer = buffer_b;
4345
4346 ret = 0;
4347
4348out_dec:
4349 atomic_dec(&cpu_buffer_a->record_disabled);
4350 atomic_dec(&cpu_buffer_b->record_disabled);
4351out:
4352 return ret;
4353}
4354EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4355#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4356
4357/**
4358 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4359 * @buffer: the buffer to allocate for.
4360 * @cpu: the cpu buffer to allocate.
4361 *
4362 * This function is used in conjunction with ring_buffer_read_page.
4363 * When reading a full page from the ring buffer, these functions
4364 * can be used to speed up the process. The calling function should
4365 * allocate a few pages first with this function. Then when it
4366 * needs to get pages from the ring buffer, it passes the result
4367 * of this function into ring_buffer_read_page, which will swap
4368 * the page that was allocated, with the read page of the buffer.
4369 *
4370 * Returns:
4371 * The page allocated, or NULL on error.
4372 */
4373void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4374{
4375 struct buffer_data_page *bpage;
4376 struct page *page;
4377
4378 page = alloc_pages_node(cpu_to_node(cpu),
4379 GFP_KERNEL | __GFP_NORETRY, 0);
4380 if (!page)
4381 return NULL;
4382
4383 bpage = page_address(page);
4384
4385 rb_init_page(bpage);
4386
4387 return bpage;
4388}
4389EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4390
4391/**
4392 * ring_buffer_free_read_page - free an allocated read page
4393 * @buffer: the buffer the page was allocate for
4394 * @data: the page to free
4395 *
4396 * Free a page allocated from ring_buffer_alloc_read_page.
4397 */
4398void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
4399{
4400 free_page((unsigned long)data);
4401}
4402EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4403
4404/**
4405 * ring_buffer_read_page - extract a page from the ring buffer
4406 * @buffer: buffer to extract from
4407 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4408 * @len: amount to extract
4409 * @cpu: the cpu of the buffer to extract
4410 * @full: should the extraction only happen when the page is full.
4411 *
4412 * This function will pull out a page from the ring buffer and consume it.
4413 * @data_page must be the address of the variable that was returned
4414 * from ring_buffer_alloc_read_page. This is because the page might be used
4415 * to swap with a page in the ring buffer.
4416 *
4417 * for example:
4418 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4419 * if (!rpage)
4420 * return error;
4421 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4422 * if (ret >= 0)
4423 * process_page(rpage, ret);
4424 *
4425 * When @full is set, the function will not return true unless
4426 * the writer is off the reader page.
4427 *
4428 * Note: it is up to the calling functions to handle sleeps and wakeups.
4429 * The ring buffer can be used anywhere in the kernel and can not
4430 * blindly call wake_up. The layer that uses the ring buffer must be
4431 * responsible for that.
4432 *
4433 * Returns:
4434 * >=0 if data has been transferred, returns the offset of consumed data.
4435 * <0 if no data has been transferred.
4436 */
4437int ring_buffer_read_page(struct ring_buffer *buffer,
4438 void **data_page, size_t len, int cpu, int full)
4439{
4440 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4441 struct ring_buffer_event *event;
4442 struct buffer_data_page *bpage;
4443 struct buffer_page *reader;
4444 unsigned long missed_events;
4445 unsigned long flags;
4446 unsigned int commit;
4447 unsigned int read;
4448 u64 save_timestamp;
4449 int ret = -1;
4450
4451 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4452 goto out;
4453
4454 /*
4455 * If len is not big enough to hold the page header, then
4456 * we can not copy anything.
4457 */
4458 if (len <= BUF_PAGE_HDR_SIZE)
4459 goto out;
4460
4461 len -= BUF_PAGE_HDR_SIZE;
4462
4463 if (!data_page)
4464 goto out;
4465
4466 bpage = *data_page;
4467 if (!bpage)
4468 goto out;
4469
4470 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4471
4472 reader = rb_get_reader_page(cpu_buffer);
4473 if (!reader)
4474 goto out_unlock;
4475
4476 event = rb_reader_event(cpu_buffer);
4477
4478 read = reader->read;
4479 commit = rb_page_commit(reader);
4480
4481 /* Check if any events were dropped */
4482 missed_events = cpu_buffer->lost_events;
4483
4484 /*
4485 * If this page has been partially read or
4486 * if len is not big enough to read the rest of the page or
4487 * a writer is still on the page, then
4488 * we must copy the data from the page to the buffer.
4489 * Otherwise, we can simply swap the page with the one passed in.
4490 */
4491 if (read || (len < (commit - read)) ||
4492 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4493 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4494 unsigned int rpos = read;
4495 unsigned int pos = 0;
4496 unsigned int size;
4497
4498 if (full)
4499 goto out_unlock;
4500
4501 if (len > (commit - read))
4502 len = (commit - read);
4503
4504 /* Always keep the time extend and data together */
4505 size = rb_event_ts_length(event);
4506
4507 if (len < size)
4508 goto out_unlock;
4509
4510 /* save the current timestamp, since the user will need it */
4511 save_timestamp = cpu_buffer->read_stamp;
4512
4513 /* Need to copy one event at a time */
4514 do {
4515 /* We need the size of one event, because
4516 * rb_advance_reader only advances by one event,
4517 * whereas rb_event_ts_length may include the size of
4518 * one or two events.
4519 * We have already ensured there's enough space if this
4520 * is a time extend. */
4521 size = rb_event_length(event);
4522 memcpy(bpage->data + pos, rpage->data + rpos, size);
4523
4524 len -= size;
4525
4526 rb_advance_reader(cpu_buffer);
4527 rpos = reader->read;
4528 pos += size;
4529
4530 if (rpos >= commit)
4531 break;
4532
4533 event = rb_reader_event(cpu_buffer);
4534 /* Always keep the time extend and data together */
4535 size = rb_event_ts_length(event);
4536 } while (len >= size);
4537
4538 /* update bpage */
4539 local_set(&bpage->commit, pos);
4540 bpage->time_stamp = save_timestamp;
4541
4542 /* we copied everything to the beginning */
4543 read = 0;
4544 } else {
4545 /* update the entry counter */
4546 cpu_buffer->read += rb_page_entries(reader);
4547 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4548
4549 /* swap the pages */
4550 rb_init_page(bpage);
4551 bpage = reader->page;
4552 reader->page = *data_page;
4553 local_set(&reader->write, 0);
4554 local_set(&reader->entries, 0);
4555 reader->read = 0;
4556 *data_page = bpage;
4557
4558 /*
4559 * Use the real_end for the data size,
4560 * This gives us a chance to store the lost events
4561 * on the page.
4562 */
4563 if (reader->real_end)
4564 local_set(&bpage->commit, reader->real_end);
4565 }
4566 ret = read;
4567
4568 cpu_buffer->lost_events = 0;
4569
4570 commit = local_read(&bpage->commit);
4571 /*
4572 * Set a flag in the commit field if we lost events
4573 */
4574 if (missed_events) {
4575 /* If there is room at the end of the page to save the
4576 * missed events, then record it there.
4577 */
4578 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4579 memcpy(&bpage->data[commit], &missed_events,
4580 sizeof(missed_events));
4581 local_add(RB_MISSED_STORED, &bpage->commit);
4582 commit += sizeof(missed_events);
4583 }
4584 local_add(RB_MISSED_EVENTS, &bpage->commit);
4585 }
4586
4587 /*
4588 * This page may be off to user land. Zero it out here.
4589 */
4590 if (commit < BUF_PAGE_SIZE)
4591 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4592
4593 out_unlock:
4594 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4595
4596 out:
4597 return ret;
4598}
4599EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4600
4601#ifdef CONFIG_HOTPLUG_CPU
4602static int rb_cpu_notify(struct notifier_block *self,
4603 unsigned long action, void *hcpu)
4604{
4605 struct ring_buffer *buffer =
4606 container_of(self, struct ring_buffer, cpu_notify);
4607 long cpu = (long)hcpu;
4608 int cpu_i, nr_pages_same;
4609 unsigned int nr_pages;
4610
4611 switch (action) {
4612 case CPU_UP_PREPARE:
4613 case CPU_UP_PREPARE_FROZEN:
4614 if (cpumask_test_cpu(cpu, buffer->cpumask))
4615 return NOTIFY_OK;
4616
4617 nr_pages = 0;
4618 nr_pages_same = 1;
4619 /* check if all cpu sizes are same */
4620 for_each_buffer_cpu(buffer, cpu_i) {
4621 /* fill in the size from first enabled cpu */
4622 if (nr_pages == 0)
4623 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4624 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4625 nr_pages_same = 0;
4626 break;
4627 }
4628 }
4629 /* allocate minimum pages, user can later expand it */
4630 if (!nr_pages_same)
4631 nr_pages = 2;
4632 buffer->buffers[cpu] =
4633 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4634 if (!buffer->buffers[cpu]) {
4635 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4636 cpu);
4637 return NOTIFY_OK;
4638 }
4639 smp_wmb();
4640 cpumask_set_cpu(cpu, buffer->cpumask);
4641 break;
4642 case CPU_DOWN_PREPARE:
4643 case CPU_DOWN_PREPARE_FROZEN:
4644 /*
4645 * Do nothing.
4646 * If we were to free the buffer, then the user would
4647 * lose any trace that was in the buffer.
4648 */
4649 break;
4650 default:
4651 break;
4652 }
4653 return NOTIFY_OK;
4654}
4655#endif
4656
4657#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4658/*
4659 * This is a basic integrity check of the ring buffer.
4660 * Late in the boot cycle this test will run when configured in.
4661 * It will kick off a thread per CPU that will go into a loop
4662 * writing to the per cpu ring buffer various sizes of data.
4663 * Some of the data will be large items, some small.
4664 *
4665 * Another thread is created that goes into a spin, sending out
4666 * IPIs to the other CPUs to also write into the ring buffer.
4667 * this is to test the nesting ability of the buffer.
4668 *
4669 * Basic stats are recorded and reported. If something in the
4670 * ring buffer should happen that's not expected, a big warning
4671 * is displayed and all ring buffers are disabled.
4672 */
4673static struct task_struct *rb_threads[NR_CPUS] __initdata;
4674
4675struct rb_test_data {
4676 struct ring_buffer *buffer;
4677 unsigned long events;
4678 unsigned long bytes_written;
4679 unsigned long bytes_alloc;
4680 unsigned long bytes_dropped;
4681 unsigned long events_nested;
4682 unsigned long bytes_written_nested;
4683 unsigned long bytes_alloc_nested;
4684 unsigned long bytes_dropped_nested;
4685 int min_size_nested;
4686 int max_size_nested;
4687 int max_size;
4688 int min_size;
4689 int cpu;
4690 int cnt;
4691};
4692
4693static struct rb_test_data rb_data[NR_CPUS] __initdata;
4694
4695/* 1 meg per cpu */
4696#define RB_TEST_BUFFER_SIZE 1048576
4697
4698static char rb_string[] __initdata =
4699 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4700 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4701 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4702
4703static bool rb_test_started __initdata;
4704
4705struct rb_item {
4706 int size;
4707 char str[];
4708};
4709
4710static __init int rb_write_something(struct rb_test_data *data, bool nested)
4711{
4712 struct ring_buffer_event *event;
4713 struct rb_item *item;
4714 bool started;
4715 int event_len;
4716 int size;
4717 int len;
4718 int cnt;
4719
4720 /* Have nested writes different that what is written */
4721 cnt = data->cnt + (nested ? 27 : 0);
4722
4723 /* Multiply cnt by ~e, to make some unique increment */
4724 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4725
4726 len = size + sizeof(struct rb_item);
4727
4728 started = rb_test_started;
4729 /* read rb_test_started before checking buffer enabled */
4730 smp_rmb();
4731
4732 event = ring_buffer_lock_reserve(data->buffer, len);
4733 if (!event) {
4734 /* Ignore dropped events before test starts. */
4735 if (started) {
4736 if (nested)
4737 data->bytes_dropped += len;
4738 else
4739 data->bytes_dropped_nested += len;
4740 }
4741 return len;
4742 }
4743
4744 event_len = ring_buffer_event_length(event);
4745
4746 if (RB_WARN_ON(data->buffer, event_len < len))
4747 goto out;
4748
4749 item = ring_buffer_event_data(event);
4750 item->size = size;
4751 memcpy(item->str, rb_string, size);
4752
4753 if (nested) {
4754 data->bytes_alloc_nested += event_len;
4755 data->bytes_written_nested += len;
4756 data->events_nested++;
4757 if (!data->min_size_nested || len < data->min_size_nested)
4758 data->min_size_nested = len;
4759 if (len > data->max_size_nested)
4760 data->max_size_nested = len;
4761 } else {
4762 data->bytes_alloc += event_len;
4763 data->bytes_written += len;
4764 data->events++;
4765 if (!data->min_size || len < data->min_size)
4766 data->max_size = len;
4767 if (len > data->max_size)
4768 data->max_size = len;
4769 }
4770
4771 out:
4772 ring_buffer_unlock_commit(data->buffer, event);
4773
4774 return 0;
4775}
4776
4777static __init int rb_test(void *arg)
4778{
4779 struct rb_test_data *data = arg;
4780
4781 while (!kthread_should_stop()) {
4782 rb_write_something(data, false);
4783 data->cnt++;
4784
4785 set_current_state(TASK_INTERRUPTIBLE);
4786 /* Now sleep between a min of 100-300us and a max of 1ms */
4787 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4788 }
4789
4790 return 0;
4791}
4792
4793static __init void rb_ipi(void *ignore)
4794{
4795 struct rb_test_data *data;
4796 int cpu = smp_processor_id();
4797
4798 data = &rb_data[cpu];
4799 rb_write_something(data, true);
4800}
4801
4802static __init int rb_hammer_test(void *arg)
4803{
4804 while (!kthread_should_stop()) {
4805
4806 /* Send an IPI to all cpus to write data! */
4807 smp_call_function(rb_ipi, NULL, 1);
4808 /* No sleep, but for non preempt, let others run */
4809 schedule();
4810 }
4811
4812 return 0;
4813}
4814
4815static __init int test_ringbuffer(void)
4816{
4817 struct task_struct *rb_hammer;
4818 struct ring_buffer *buffer;
4819 int cpu;
4820 int ret = 0;
4821
4822 pr_info("Running ring buffer tests...\n");
4823
4824 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
4825 if (WARN_ON(!buffer))
4826 return 0;
4827
4828 /* Disable buffer so that threads can't write to it yet */
4829 ring_buffer_record_off(buffer);
4830
4831 for_each_online_cpu(cpu) {
4832 rb_data[cpu].buffer = buffer;
4833 rb_data[cpu].cpu = cpu;
4834 rb_data[cpu].cnt = cpu;
4835 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
4836 "rbtester/%d", cpu);
4837 if (WARN_ON(!rb_threads[cpu])) {
4838 pr_cont("FAILED\n");
4839 ret = -1;
4840 goto out_free;
4841 }
4842
4843 kthread_bind(rb_threads[cpu], cpu);
4844 wake_up_process(rb_threads[cpu]);
4845 }
4846
4847 /* Now create the rb hammer! */
4848 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
4849 if (WARN_ON(!rb_hammer)) {
4850 pr_cont("FAILED\n");
4851 ret = -1;
4852 goto out_free;
4853 }
4854
4855 ring_buffer_record_on(buffer);
4856 /*
4857 * Show buffer is enabled before setting rb_test_started.
4858 * Yes there's a small race window where events could be
4859 * dropped and the thread wont catch it. But when a ring
4860 * buffer gets enabled, there will always be some kind of
4861 * delay before other CPUs see it. Thus, we don't care about
4862 * those dropped events. We care about events dropped after
4863 * the threads see that the buffer is active.
4864 */
4865 smp_wmb();
4866 rb_test_started = true;
4867
4868 set_current_state(TASK_INTERRUPTIBLE);
4869 /* Just run for 10 seconds */;
4870 schedule_timeout(10 * HZ);
4871
4872 kthread_stop(rb_hammer);
4873
4874 out_free:
4875 for_each_online_cpu(cpu) {
4876 if (!rb_threads[cpu])
4877 break;
4878 kthread_stop(rb_threads[cpu]);
4879 }
4880 if (ret) {
4881 ring_buffer_free(buffer);
4882 return ret;
4883 }
4884
4885 /* Report! */
4886 pr_info("finished\n");
4887 for_each_online_cpu(cpu) {
4888 struct ring_buffer_event *event;
4889 struct rb_test_data *data = &rb_data[cpu];
4890 struct rb_item *item;
4891 unsigned long total_events;
4892 unsigned long total_dropped;
4893 unsigned long total_written;
4894 unsigned long total_alloc;
4895 unsigned long total_read = 0;
4896 unsigned long total_size = 0;
4897 unsigned long total_len = 0;
4898 unsigned long total_lost = 0;
4899 unsigned long lost;
4900 int big_event_size;
4901 int small_event_size;
4902
4903 ret = -1;
4904
4905 total_events = data->events + data->events_nested;
4906 total_written = data->bytes_written + data->bytes_written_nested;
4907 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
4908 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
4909
4910 big_event_size = data->max_size + data->max_size_nested;
4911 small_event_size = data->min_size + data->min_size_nested;
4912
4913 pr_info("CPU %d:\n", cpu);
4914 pr_info(" events: %ld\n", total_events);
4915 pr_info(" dropped bytes: %ld\n", total_dropped);
4916 pr_info(" alloced bytes: %ld\n", total_alloc);
4917 pr_info(" written bytes: %ld\n", total_written);
4918 pr_info(" biggest event: %d\n", big_event_size);
4919 pr_info(" smallest event: %d\n", small_event_size);
4920
4921 if (RB_WARN_ON(buffer, total_dropped))
4922 break;
4923
4924 ret = 0;
4925
4926 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
4927 total_lost += lost;
4928 item = ring_buffer_event_data(event);
4929 total_len += ring_buffer_event_length(event);
4930 total_size += item->size + sizeof(struct rb_item);
4931 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
4932 pr_info("FAILED!\n");
4933 pr_info("buffer had: %.*s\n", item->size, item->str);
4934 pr_info("expected: %.*s\n", item->size, rb_string);
4935 RB_WARN_ON(buffer, 1);
4936 ret = -1;
4937 break;
4938 }
4939 total_read++;
4940 }
4941 if (ret)
4942 break;
4943
4944 ret = -1;
4945
4946 pr_info(" read events: %ld\n", total_read);
4947 pr_info(" lost events: %ld\n", total_lost);
4948 pr_info(" total events: %ld\n", total_lost + total_read);
4949 pr_info(" recorded len bytes: %ld\n", total_len);
4950 pr_info(" recorded size bytes: %ld\n", total_size);
4951 if (total_lost)
4952 pr_info(" With dropped events, record len and size may not match\n"
4953 " alloced and written from above\n");
4954 if (!total_lost) {
4955 if (RB_WARN_ON(buffer, total_len != total_alloc ||
4956 total_size != total_written))
4957 break;
4958 }
4959 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
4960 break;
4961
4962 ret = 0;
4963 }
4964 if (!ret)
4965 pr_info("Ring buffer PASSED!\n");
4966
4967 ring_buffer_free(buffer);
4968 return 0;
4969}
4970
4971late_initcall(test_ringbuffer);
4972#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 */