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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Performance events ring-buffer code:
4 *
5 * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
6 * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
7 * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
8 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
9 */
10
11#include <linux/perf_event.h>
12#include <linux/vmalloc.h>
13#include <linux/slab.h>
14#include <linux/circ_buf.h>
15#include <linux/poll.h>
16#include <linux/nospec.h>
17
18#include "internal.h"
19
20static void perf_output_wakeup(struct perf_output_handle *handle)
21{
22 atomic_set(&handle->rb->poll, EPOLLIN);
23
24 handle->event->pending_wakeup = 1;
25
26 if (*perf_event_fasync(handle->event) && !handle->event->pending_kill)
27 handle->event->pending_kill = POLL_IN;
28
29 irq_work_queue(&handle->event->pending_irq);
30}
31
32/*
33 * We need to ensure a later event_id doesn't publish a head when a former
34 * event isn't done writing. However since we need to deal with NMIs we
35 * cannot fully serialize things.
36 *
37 * We only publish the head (and generate a wakeup) when the outer-most
38 * event completes.
39 */
40static void perf_output_get_handle(struct perf_output_handle *handle)
41{
42 struct perf_buffer *rb = handle->rb;
43
44 preempt_disable();
45
46 /*
47 * Avoid an explicit LOAD/STORE such that architectures with memops
48 * can use them.
49 */
50 (*(volatile unsigned int *)&rb->nest)++;
51 handle->wakeup = local_read(&rb->wakeup);
52}
53
54static void perf_output_put_handle(struct perf_output_handle *handle)
55{
56 struct perf_buffer *rb = handle->rb;
57 unsigned long head;
58 unsigned int nest;
59
60 /*
61 * If this isn't the outermost nesting, we don't have to update
62 * @rb->user_page->data_head.
63 */
64 nest = READ_ONCE(rb->nest);
65 if (nest > 1) {
66 WRITE_ONCE(rb->nest, nest - 1);
67 goto out;
68 }
69
70again:
71 /*
72 * In order to avoid publishing a head value that goes backwards,
73 * we must ensure the load of @rb->head happens after we've
74 * incremented @rb->nest.
75 *
76 * Otherwise we can observe a @rb->head value before one published
77 * by an IRQ/NMI happening between the load and the increment.
78 */
79 barrier();
80 head = local_read(&rb->head);
81
82 /*
83 * IRQ/NMI can happen here and advance @rb->head, causing our
84 * load above to be stale.
85 */
86
87 /*
88 * Since the mmap() consumer (userspace) can run on a different CPU:
89 *
90 * kernel user
91 *
92 * if (LOAD ->data_tail) { LOAD ->data_head
93 * (A) smp_rmb() (C)
94 * STORE $data LOAD $data
95 * smp_wmb() (B) smp_mb() (D)
96 * STORE ->data_head STORE ->data_tail
97 * }
98 *
99 * Where A pairs with D, and B pairs with C.
100 *
101 * In our case (A) is a control dependency that separates the load of
102 * the ->data_tail and the stores of $data. In case ->data_tail
103 * indicates there is no room in the buffer to store $data we do not.
104 *
105 * D needs to be a full barrier since it separates the data READ
106 * from the tail WRITE.
107 *
108 * For B a WMB is sufficient since it separates two WRITEs, and for C
109 * an RMB is sufficient since it separates two READs.
110 *
111 * See perf_output_begin().
112 */
113 smp_wmb(); /* B, matches C */
114 WRITE_ONCE(rb->user_page->data_head, head);
115
116 /*
117 * We must publish the head before decrementing the nest count,
118 * otherwise an IRQ/NMI can publish a more recent head value and our
119 * write will (temporarily) publish a stale value.
120 */
121 barrier();
122 WRITE_ONCE(rb->nest, 0);
123
124 /*
125 * Ensure we decrement @rb->nest before we validate the @rb->head.
126 * Otherwise we cannot be sure we caught the 'last' nested update.
127 */
128 barrier();
129 if (unlikely(head != local_read(&rb->head))) {
130 WRITE_ONCE(rb->nest, 1);
131 goto again;
132 }
133
134 if (handle->wakeup != local_read(&rb->wakeup))
135 perf_output_wakeup(handle);
136
137out:
138 preempt_enable();
139}
140
141static __always_inline bool
142ring_buffer_has_space(unsigned long head, unsigned long tail,
143 unsigned long data_size, unsigned int size,
144 bool backward)
145{
146 if (!backward)
147 return CIRC_SPACE(head, tail, data_size) >= size;
148 else
149 return CIRC_SPACE(tail, head, data_size) >= size;
150}
151
152static __always_inline int
153__perf_output_begin(struct perf_output_handle *handle,
154 struct perf_sample_data *data,
155 struct perf_event *event, unsigned int size,
156 bool backward)
157{
158 struct perf_buffer *rb;
159 unsigned long tail, offset, head;
160 int have_lost, page_shift;
161 struct {
162 struct perf_event_header header;
163 u64 id;
164 u64 lost;
165 } lost_event;
166
167 rcu_read_lock();
168 /*
169 * For inherited events we send all the output towards the parent.
170 */
171 if (event->parent)
172 event = event->parent;
173
174 rb = rcu_dereference(event->rb);
175 if (unlikely(!rb))
176 goto out;
177
178 if (unlikely(rb->paused)) {
179 if (rb->nr_pages) {
180 local_inc(&rb->lost);
181 atomic64_inc(&event->lost_samples);
182 }
183 goto out;
184 }
185
186 handle->rb = rb;
187 handle->event = event;
188
189 have_lost = local_read(&rb->lost);
190 if (unlikely(have_lost)) {
191 size += sizeof(lost_event);
192 if (event->attr.sample_id_all)
193 size += event->id_header_size;
194 }
195
196 perf_output_get_handle(handle);
197
198 offset = local_read(&rb->head);
199 do {
200 head = offset;
201 tail = READ_ONCE(rb->user_page->data_tail);
202 if (!rb->overwrite) {
203 if (unlikely(!ring_buffer_has_space(head, tail,
204 perf_data_size(rb),
205 size, backward)))
206 goto fail;
207 }
208
209 /*
210 * The above forms a control dependency barrier separating the
211 * @tail load above from the data stores below. Since the @tail
212 * load is required to compute the branch to fail below.
213 *
214 * A, matches D; the full memory barrier userspace SHOULD issue
215 * after reading the data and before storing the new tail
216 * position.
217 *
218 * See perf_output_put_handle().
219 */
220
221 if (!backward)
222 head += size;
223 else
224 head -= size;
225 } while (!local_try_cmpxchg(&rb->head, &offset, head));
226
227 if (backward) {
228 offset = head;
229 head = (u64)(-head);
230 }
231
232 /*
233 * We rely on the implied barrier() by local_cmpxchg() to ensure
234 * none of the data stores below can be lifted up by the compiler.
235 */
236
237 if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
238 local_add(rb->watermark, &rb->wakeup);
239
240 page_shift = PAGE_SHIFT + page_order(rb);
241
242 handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
243 offset &= (1UL << page_shift) - 1;
244 handle->addr = rb->data_pages[handle->page] + offset;
245 handle->size = (1UL << page_shift) - offset;
246
247 if (unlikely(have_lost)) {
248 lost_event.header.size = sizeof(lost_event);
249 lost_event.header.type = PERF_RECORD_LOST;
250 lost_event.header.misc = 0;
251 lost_event.id = event->id;
252 lost_event.lost = local_xchg(&rb->lost, 0);
253
254 /* XXX mostly redundant; @data is already fully initializes */
255 perf_event_header__init_id(&lost_event.header, data, event);
256 perf_output_put(handle, lost_event);
257 perf_event__output_id_sample(event, handle, data);
258 }
259
260 return 0;
261
262fail:
263 local_inc(&rb->lost);
264 atomic64_inc(&event->lost_samples);
265 perf_output_put_handle(handle);
266out:
267 rcu_read_unlock();
268
269 return -ENOSPC;
270}
271
272int perf_output_begin_forward(struct perf_output_handle *handle,
273 struct perf_sample_data *data,
274 struct perf_event *event, unsigned int size)
275{
276 return __perf_output_begin(handle, data, event, size, false);
277}
278
279int perf_output_begin_backward(struct perf_output_handle *handle,
280 struct perf_sample_data *data,
281 struct perf_event *event, unsigned int size)
282{
283 return __perf_output_begin(handle, data, event, size, true);
284}
285
286int perf_output_begin(struct perf_output_handle *handle,
287 struct perf_sample_data *data,
288 struct perf_event *event, unsigned int size)
289{
290
291 return __perf_output_begin(handle, data, event, size,
292 unlikely(is_write_backward(event)));
293}
294
295unsigned int perf_output_copy(struct perf_output_handle *handle,
296 const void *buf, unsigned int len)
297{
298 return __output_copy(handle, buf, len);
299}
300
301unsigned int perf_output_skip(struct perf_output_handle *handle,
302 unsigned int len)
303{
304 return __output_skip(handle, NULL, len);
305}
306
307void perf_output_end(struct perf_output_handle *handle)
308{
309 perf_output_put_handle(handle);
310 rcu_read_unlock();
311}
312
313static void
314ring_buffer_init(struct perf_buffer *rb, long watermark, int flags)
315{
316 long max_size = perf_data_size(rb);
317
318 if (watermark)
319 rb->watermark = min(max_size, watermark);
320
321 if (!rb->watermark)
322 rb->watermark = max_size / 2;
323
324 if (flags & RING_BUFFER_WRITABLE)
325 rb->overwrite = 0;
326 else
327 rb->overwrite = 1;
328
329 refcount_set(&rb->refcount, 1);
330
331 INIT_LIST_HEAD(&rb->event_list);
332 spin_lock_init(&rb->event_lock);
333
334 /*
335 * perf_output_begin() only checks rb->paused, therefore
336 * rb->paused must be true if we have no pages for output.
337 */
338 if (!rb->nr_pages)
339 rb->paused = 1;
340
341 mutex_init(&rb->aux_mutex);
342}
343
344void perf_aux_output_flag(struct perf_output_handle *handle, u64 flags)
345{
346 /*
347 * OVERWRITE is determined by perf_aux_output_end() and can't
348 * be passed in directly.
349 */
350 if (WARN_ON_ONCE(flags & PERF_AUX_FLAG_OVERWRITE))
351 return;
352
353 handle->aux_flags |= flags;
354}
355EXPORT_SYMBOL_GPL(perf_aux_output_flag);
356
357/*
358 * This is called before hardware starts writing to the AUX area to
359 * obtain an output handle and make sure there's room in the buffer.
360 * When the capture completes, call perf_aux_output_end() to commit
361 * the recorded data to the buffer.
362 *
363 * The ordering is similar to that of perf_output_{begin,end}, with
364 * the exception of (B), which should be taken care of by the pmu
365 * driver, since ordering rules will differ depending on hardware.
366 *
367 * Call this from pmu::start(); see the comment in perf_aux_output_end()
368 * about its use in pmu callbacks. Both can also be called from the PMI
369 * handler if needed.
370 */
371void *perf_aux_output_begin(struct perf_output_handle *handle,
372 struct perf_event *event)
373{
374 struct perf_event *output_event = event;
375 unsigned long aux_head, aux_tail;
376 struct perf_buffer *rb;
377 unsigned int nest;
378
379 if (output_event->parent)
380 output_event = output_event->parent;
381
382 /*
383 * Since this will typically be open across pmu::add/pmu::del, we
384 * grab ring_buffer's refcount instead of holding rcu read lock
385 * to make sure it doesn't disappear under us.
386 */
387 rb = ring_buffer_get(output_event);
388 if (!rb)
389 return NULL;
390
391 if (!rb_has_aux(rb))
392 goto err;
393
394 /*
395 * If aux_mmap_count is zero, the aux buffer is in perf_mmap_close(),
396 * about to get freed, so we leave immediately.
397 *
398 * Checking rb::aux_mmap_count and rb::refcount has to be done in
399 * the same order, see perf_mmap_close. Otherwise we end up freeing
400 * aux pages in this path, which is a bug, because in_atomic().
401 */
402 if (!atomic_read(&rb->aux_mmap_count))
403 goto err;
404
405 if (!refcount_inc_not_zero(&rb->aux_refcount))
406 goto err;
407
408 nest = READ_ONCE(rb->aux_nest);
409 /*
410 * Nesting is not supported for AUX area, make sure nested
411 * writers are caught early
412 */
413 if (WARN_ON_ONCE(nest))
414 goto err_put;
415
416 WRITE_ONCE(rb->aux_nest, nest + 1);
417
418 aux_head = rb->aux_head;
419
420 handle->rb = rb;
421 handle->event = event;
422 handle->head = aux_head;
423 handle->size = 0;
424 handle->aux_flags = 0;
425
426 /*
427 * In overwrite mode, AUX data stores do not depend on aux_tail,
428 * therefore (A) control dependency barrier does not exist. The
429 * (B) <-> (C) ordering is still observed by the pmu driver.
430 */
431 if (!rb->aux_overwrite) {
432 aux_tail = READ_ONCE(rb->user_page->aux_tail);
433 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
434 if (aux_head - aux_tail < perf_aux_size(rb))
435 handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
436
437 /*
438 * handle->size computation depends on aux_tail load; this forms a
439 * control dependency barrier separating aux_tail load from aux data
440 * store that will be enabled on successful return
441 */
442 if (!handle->size) { /* A, matches D */
443 event->pending_disable = smp_processor_id();
444 perf_output_wakeup(handle);
445 WRITE_ONCE(rb->aux_nest, 0);
446 goto err_put;
447 }
448 }
449
450 return handle->rb->aux_priv;
451
452err_put:
453 /* can't be last */
454 rb_free_aux(rb);
455
456err:
457 ring_buffer_put(rb);
458 handle->event = NULL;
459
460 return NULL;
461}
462EXPORT_SYMBOL_GPL(perf_aux_output_begin);
463
464static __always_inline bool rb_need_aux_wakeup(struct perf_buffer *rb)
465{
466 if (rb->aux_overwrite)
467 return false;
468
469 if (rb->aux_head - rb->aux_wakeup >= rb->aux_watermark) {
470 rb->aux_wakeup = rounddown(rb->aux_head, rb->aux_watermark);
471 return true;
472 }
473
474 return false;
475}
476
477/*
478 * Commit the data written by hardware into the ring buffer by adjusting
479 * aux_head and posting a PERF_RECORD_AUX into the perf buffer. It is the
480 * pmu driver's responsibility to observe ordering rules of the hardware,
481 * so that all the data is externally visible before this is called.
482 *
483 * Note: this has to be called from pmu::stop() callback, as the assumption
484 * of the AUX buffer management code is that after pmu::stop(), the AUX
485 * transaction must be stopped and therefore drop the AUX reference count.
486 */
487void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
488{
489 bool wakeup = !!(handle->aux_flags & PERF_AUX_FLAG_TRUNCATED);
490 struct perf_buffer *rb = handle->rb;
491 unsigned long aux_head;
492
493 /* in overwrite mode, driver provides aux_head via handle */
494 if (rb->aux_overwrite) {
495 handle->aux_flags |= PERF_AUX_FLAG_OVERWRITE;
496
497 aux_head = handle->head;
498 rb->aux_head = aux_head;
499 } else {
500 handle->aux_flags &= ~PERF_AUX_FLAG_OVERWRITE;
501
502 aux_head = rb->aux_head;
503 rb->aux_head += size;
504 }
505
506 /*
507 * Only send RECORD_AUX if we have something useful to communicate
508 *
509 * Note: the OVERWRITE records by themselves are not considered
510 * useful, as they don't communicate any *new* information,
511 * aside from the short-lived offset, that becomes history at
512 * the next event sched-in and therefore isn't useful.
513 * The userspace that needs to copy out AUX data in overwrite
514 * mode should know to use user_page::aux_head for the actual
515 * offset. So, from now on we don't output AUX records that
516 * have *only* OVERWRITE flag set.
517 */
518 if (size || (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE))
519 perf_event_aux_event(handle->event, aux_head, size,
520 handle->aux_flags);
521
522 WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
523 if (rb_need_aux_wakeup(rb))
524 wakeup = true;
525
526 if (wakeup) {
527 if (handle->aux_flags & PERF_AUX_FLAG_TRUNCATED)
528 handle->event->pending_disable = smp_processor_id();
529 perf_output_wakeup(handle);
530 }
531
532 handle->event = NULL;
533
534 WRITE_ONCE(rb->aux_nest, 0);
535 /* can't be last */
536 rb_free_aux(rb);
537 ring_buffer_put(rb);
538}
539EXPORT_SYMBOL_GPL(perf_aux_output_end);
540
541/*
542 * Skip over a given number of bytes in the AUX buffer, due to, for example,
543 * hardware's alignment constraints.
544 */
545int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
546{
547 struct perf_buffer *rb = handle->rb;
548
549 if (size > handle->size)
550 return -ENOSPC;
551
552 rb->aux_head += size;
553
554 WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
555 if (rb_need_aux_wakeup(rb)) {
556 perf_output_wakeup(handle);
557 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
558 }
559
560 handle->head = rb->aux_head;
561 handle->size -= size;
562
563 return 0;
564}
565EXPORT_SYMBOL_GPL(perf_aux_output_skip);
566
567void *perf_get_aux(struct perf_output_handle *handle)
568{
569 /* this is only valid between perf_aux_output_begin and *_end */
570 if (!handle->event)
571 return NULL;
572
573 return handle->rb->aux_priv;
574}
575EXPORT_SYMBOL_GPL(perf_get_aux);
576
577/*
578 * Copy out AUX data from an AUX handle.
579 */
580long perf_output_copy_aux(struct perf_output_handle *aux_handle,
581 struct perf_output_handle *handle,
582 unsigned long from, unsigned long to)
583{
584 struct perf_buffer *rb = aux_handle->rb;
585 unsigned long tocopy, remainder, len = 0;
586 void *addr;
587
588 from &= (rb->aux_nr_pages << PAGE_SHIFT) - 1;
589 to &= (rb->aux_nr_pages << PAGE_SHIFT) - 1;
590
591 do {
592 tocopy = PAGE_SIZE - offset_in_page(from);
593 if (to > from)
594 tocopy = min(tocopy, to - from);
595 if (!tocopy)
596 break;
597
598 addr = rb->aux_pages[from >> PAGE_SHIFT];
599 addr += offset_in_page(from);
600
601 remainder = perf_output_copy(handle, addr, tocopy);
602 if (remainder)
603 return -EFAULT;
604
605 len += tocopy;
606 from += tocopy;
607 from &= (rb->aux_nr_pages << PAGE_SHIFT) - 1;
608 } while (to != from);
609
610 return len;
611}
612
613#define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
614
615static struct page *rb_alloc_aux_page(int node, int order)
616{
617 struct page *page;
618
619 if (order > MAX_PAGE_ORDER)
620 order = MAX_PAGE_ORDER;
621
622 do {
623 page = alloc_pages_node(node, PERF_AUX_GFP, order);
624 } while (!page && order--);
625
626 if (page && order) {
627 /*
628 * Communicate the allocation size to the driver:
629 * if we managed to secure a high-order allocation,
630 * set its first page's private to this order;
631 * !PagePrivate(page) means it's just a normal page.
632 */
633 split_page(page, order);
634 SetPagePrivate(page);
635 set_page_private(page, order);
636 }
637
638 return page;
639}
640
641static void rb_free_aux_page(struct perf_buffer *rb, int idx)
642{
643 struct page *page = virt_to_page(rb->aux_pages[idx]);
644
645 ClearPagePrivate(page);
646 page->mapping = NULL;
647 __free_page(page);
648}
649
650static void __rb_free_aux(struct perf_buffer *rb)
651{
652 int pg;
653
654 /*
655 * Should never happen, the last reference should be dropped from
656 * perf_mmap_close() path, which first stops aux transactions (which
657 * in turn are the atomic holders of aux_refcount) and then does the
658 * last rb_free_aux().
659 */
660 WARN_ON_ONCE(in_atomic());
661
662 if (rb->aux_priv) {
663 rb->free_aux(rb->aux_priv);
664 rb->free_aux = NULL;
665 rb->aux_priv = NULL;
666 }
667
668 if (rb->aux_nr_pages) {
669 for (pg = 0; pg < rb->aux_nr_pages; pg++)
670 rb_free_aux_page(rb, pg);
671
672 kfree(rb->aux_pages);
673 rb->aux_nr_pages = 0;
674 }
675}
676
677int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
678 pgoff_t pgoff, int nr_pages, long watermark, int flags)
679{
680 bool overwrite = !(flags & RING_BUFFER_WRITABLE);
681 int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
682 int ret = -ENOMEM, max_order;
683
684 if (!has_aux(event))
685 return -EOPNOTSUPP;
686
687 if (nr_pages <= 0)
688 return -EINVAL;
689
690 if (!overwrite) {
691 /*
692 * Watermark defaults to half the buffer, and so does the
693 * max_order, to aid PMU drivers in double buffering.
694 */
695 if (!watermark)
696 watermark = min_t(unsigned long,
697 U32_MAX,
698 (unsigned long)nr_pages << (PAGE_SHIFT - 1));
699
700 /*
701 * Use aux_watermark as the basis for chunking to
702 * help PMU drivers honor the watermark.
703 */
704 max_order = get_order(watermark);
705 } else {
706 /*
707 * We need to start with the max_order that fits in nr_pages,
708 * not the other way around, hence ilog2() and not get_order.
709 */
710 max_order = ilog2(nr_pages);
711 watermark = 0;
712 }
713
714 /*
715 * kcalloc_node() is unable to allocate buffer if the size is larger
716 * than: PAGE_SIZE << MAX_PAGE_ORDER; directly bail out in this case.
717 */
718 if (get_order((unsigned long)nr_pages * sizeof(void *)) > MAX_PAGE_ORDER)
719 return -ENOMEM;
720 rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL,
721 node);
722 if (!rb->aux_pages)
723 return -ENOMEM;
724
725 rb->free_aux = event->pmu->free_aux;
726 for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;) {
727 struct page *page;
728 int last, order;
729
730 order = min(max_order, ilog2(nr_pages - rb->aux_nr_pages));
731 page = rb_alloc_aux_page(node, order);
732 if (!page)
733 goto out;
734
735 for (last = rb->aux_nr_pages + (1 << page_private(page));
736 last > rb->aux_nr_pages; rb->aux_nr_pages++)
737 rb->aux_pages[rb->aux_nr_pages] = page_address(page++);
738 }
739
740 /*
741 * In overwrite mode, PMUs that don't support SG may not handle more
742 * than one contiguous allocation, since they rely on PMI to do double
743 * buffering. In this case, the entire buffer has to be one contiguous
744 * chunk.
745 */
746 if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) &&
747 overwrite) {
748 struct page *page = virt_to_page(rb->aux_pages[0]);
749
750 if (page_private(page) != max_order)
751 goto out;
752 }
753
754 rb->aux_priv = event->pmu->setup_aux(event, rb->aux_pages, nr_pages,
755 overwrite);
756 if (!rb->aux_priv)
757 goto out;
758
759 ret = 0;
760
761 /*
762 * aux_pages (and pmu driver's private data, aux_priv) will be
763 * referenced in both producer's and consumer's contexts, thus
764 * we keep a refcount here to make sure either of the two can
765 * reference them safely.
766 */
767 refcount_set(&rb->aux_refcount, 1);
768
769 rb->aux_overwrite = overwrite;
770 rb->aux_watermark = watermark;
771
772out:
773 if (!ret)
774 rb->aux_pgoff = pgoff;
775 else
776 __rb_free_aux(rb);
777
778 return ret;
779}
780
781void rb_free_aux(struct perf_buffer *rb)
782{
783 if (refcount_dec_and_test(&rb->aux_refcount))
784 __rb_free_aux(rb);
785}
786
787#ifndef CONFIG_PERF_USE_VMALLOC
788
789/*
790 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
791 */
792
793static struct page *
794__perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
795{
796 if (pgoff > rb->nr_pages)
797 return NULL;
798
799 if (pgoff == 0)
800 return virt_to_page(rb->user_page);
801
802 return virt_to_page(rb->data_pages[pgoff - 1]);
803}
804
805static void *perf_mmap_alloc_page(int cpu)
806{
807 struct page *page;
808 int node;
809
810 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
811 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
812 if (!page)
813 return NULL;
814
815 return page_address(page);
816}
817
818static void perf_mmap_free_page(void *addr)
819{
820 struct page *page = virt_to_page(addr);
821
822 page->mapping = NULL;
823 __free_page(page);
824}
825
826struct perf_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
827{
828 struct perf_buffer *rb;
829 unsigned long size;
830 int i, node;
831
832 size = sizeof(struct perf_buffer);
833 size += nr_pages * sizeof(void *);
834
835 if (order_base_2(size) > PAGE_SHIFT+MAX_PAGE_ORDER)
836 goto fail;
837
838 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
839 rb = kzalloc_node(size, GFP_KERNEL, node);
840 if (!rb)
841 goto fail;
842
843 rb->user_page = perf_mmap_alloc_page(cpu);
844 if (!rb->user_page)
845 goto fail_user_page;
846
847 for (i = 0; i < nr_pages; i++) {
848 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
849 if (!rb->data_pages[i])
850 goto fail_data_pages;
851 }
852
853 rb->nr_pages = nr_pages;
854
855 ring_buffer_init(rb, watermark, flags);
856
857 return rb;
858
859fail_data_pages:
860 for (i--; i >= 0; i--)
861 perf_mmap_free_page(rb->data_pages[i]);
862
863 perf_mmap_free_page(rb->user_page);
864
865fail_user_page:
866 kfree(rb);
867
868fail:
869 return NULL;
870}
871
872void rb_free(struct perf_buffer *rb)
873{
874 int i;
875
876 perf_mmap_free_page(rb->user_page);
877 for (i = 0; i < rb->nr_pages; i++)
878 perf_mmap_free_page(rb->data_pages[i]);
879 kfree(rb);
880}
881
882#else
883static struct page *
884__perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
885{
886 /* The '>' counts in the user page. */
887 if (pgoff > data_page_nr(rb))
888 return NULL;
889
890 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
891}
892
893static void perf_mmap_unmark_page(void *addr)
894{
895 struct page *page = vmalloc_to_page(addr);
896
897 page->mapping = NULL;
898}
899
900static void rb_free_work(struct work_struct *work)
901{
902 struct perf_buffer *rb;
903 void *base;
904 int i, nr;
905
906 rb = container_of(work, struct perf_buffer, work);
907 nr = data_page_nr(rb);
908
909 base = rb->user_page;
910 /* The '<=' counts in the user page. */
911 for (i = 0; i <= nr; i++)
912 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
913
914 vfree(base);
915 kfree(rb);
916}
917
918void rb_free(struct perf_buffer *rb)
919{
920 schedule_work(&rb->work);
921}
922
923struct perf_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
924{
925 struct perf_buffer *rb;
926 unsigned long size;
927 void *all_buf;
928 int node;
929
930 size = sizeof(struct perf_buffer);
931 size += sizeof(void *);
932
933 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
934 rb = kzalloc_node(size, GFP_KERNEL, node);
935 if (!rb)
936 goto fail;
937
938 INIT_WORK(&rb->work, rb_free_work);
939
940 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
941 if (!all_buf)
942 goto fail_all_buf;
943
944 rb->user_page = all_buf;
945 rb->data_pages[0] = all_buf + PAGE_SIZE;
946 if (nr_pages) {
947 rb->nr_pages = 1;
948 rb->page_order = ilog2(nr_pages);
949 }
950
951 ring_buffer_init(rb, watermark, flags);
952
953 return rb;
954
955fail_all_buf:
956 kfree(rb);
957
958fail:
959 return NULL;
960}
961
962#endif
963
964struct page *
965perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
966{
967 if (rb->aux_nr_pages) {
968 /* above AUX space */
969 if (pgoff > rb->aux_pgoff + rb->aux_nr_pages)
970 return NULL;
971
972 /* AUX space */
973 if (pgoff >= rb->aux_pgoff) {
974 int aux_pgoff = array_index_nospec(pgoff - rb->aux_pgoff, rb->aux_nr_pages);
975 return virt_to_page(rb->aux_pages[aux_pgoff]);
976 }
977 }
978
979 return __perf_mmap_to_page(rb, pgoff);
980}
1/*
2 * Performance events ring-buffer code:
3 *
4 * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
5 * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
6 * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
7 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
8 *
9 * For licensing details see kernel-base/COPYING
10 */
11
12#include <linux/perf_event.h>
13#include <linux/vmalloc.h>
14#include <linux/slab.h>
15#include <linux/circ_buf.h>
16#include <linux/poll.h>
17#include <linux/nospec.h>
18
19#include "internal.h"
20
21static void perf_output_wakeup(struct perf_output_handle *handle)
22{
23 atomic_set(&handle->rb->poll, EPOLLIN);
24
25 handle->event->pending_wakeup = 1;
26 irq_work_queue(&handle->event->pending);
27}
28
29/*
30 * We need to ensure a later event_id doesn't publish a head when a former
31 * event isn't done writing. However since we need to deal with NMIs we
32 * cannot fully serialize things.
33 *
34 * We only publish the head (and generate a wakeup) when the outer-most
35 * event completes.
36 */
37static void perf_output_get_handle(struct perf_output_handle *handle)
38{
39 struct ring_buffer *rb = handle->rb;
40
41 preempt_disable();
42 local_inc(&rb->nest);
43 handle->wakeup = local_read(&rb->wakeup);
44}
45
46static void perf_output_put_handle(struct perf_output_handle *handle)
47{
48 struct ring_buffer *rb = handle->rb;
49 unsigned long head;
50
51again:
52 head = local_read(&rb->head);
53
54 /*
55 * IRQ/NMI can happen here, which means we can miss a head update.
56 */
57
58 if (!local_dec_and_test(&rb->nest))
59 goto out;
60
61 /*
62 * Since the mmap() consumer (userspace) can run on a different CPU:
63 *
64 * kernel user
65 *
66 * if (LOAD ->data_tail) { LOAD ->data_head
67 * (A) smp_rmb() (C)
68 * STORE $data LOAD $data
69 * smp_wmb() (B) smp_mb() (D)
70 * STORE ->data_head STORE ->data_tail
71 * }
72 *
73 * Where A pairs with D, and B pairs with C.
74 *
75 * In our case (A) is a control dependency that separates the load of
76 * the ->data_tail and the stores of $data. In case ->data_tail
77 * indicates there is no room in the buffer to store $data we do not.
78 *
79 * D needs to be a full barrier since it separates the data READ
80 * from the tail WRITE.
81 *
82 * For B a WMB is sufficient since it separates two WRITEs, and for C
83 * an RMB is sufficient since it separates two READs.
84 *
85 * See perf_output_begin().
86 */
87 smp_wmb(); /* B, matches C */
88 rb->user_page->data_head = head;
89
90 /*
91 * Now check if we missed an update -- rely on previous implied
92 * compiler barriers to force a re-read.
93 */
94 if (unlikely(head != local_read(&rb->head))) {
95 local_inc(&rb->nest);
96 goto again;
97 }
98
99 if (handle->wakeup != local_read(&rb->wakeup))
100 perf_output_wakeup(handle);
101
102out:
103 preempt_enable();
104}
105
106static bool __always_inline
107ring_buffer_has_space(unsigned long head, unsigned long tail,
108 unsigned long data_size, unsigned int size,
109 bool backward)
110{
111 if (!backward)
112 return CIRC_SPACE(head, tail, data_size) >= size;
113 else
114 return CIRC_SPACE(tail, head, data_size) >= size;
115}
116
117static int __always_inline
118__perf_output_begin(struct perf_output_handle *handle,
119 struct perf_event *event, unsigned int size,
120 bool backward)
121{
122 struct ring_buffer *rb;
123 unsigned long tail, offset, head;
124 int have_lost, page_shift;
125 struct {
126 struct perf_event_header header;
127 u64 id;
128 u64 lost;
129 } lost_event;
130
131 rcu_read_lock();
132 /*
133 * For inherited events we send all the output towards the parent.
134 */
135 if (event->parent)
136 event = event->parent;
137
138 rb = rcu_dereference(event->rb);
139 if (unlikely(!rb))
140 goto out;
141
142 if (unlikely(rb->paused)) {
143 if (rb->nr_pages)
144 local_inc(&rb->lost);
145 goto out;
146 }
147
148 handle->rb = rb;
149 handle->event = event;
150
151 have_lost = local_read(&rb->lost);
152 if (unlikely(have_lost)) {
153 size += sizeof(lost_event);
154 if (event->attr.sample_id_all)
155 size += event->id_header_size;
156 }
157
158 perf_output_get_handle(handle);
159
160 do {
161 tail = READ_ONCE(rb->user_page->data_tail);
162 offset = head = local_read(&rb->head);
163 if (!rb->overwrite) {
164 if (unlikely(!ring_buffer_has_space(head, tail,
165 perf_data_size(rb),
166 size, backward)))
167 goto fail;
168 }
169
170 /*
171 * The above forms a control dependency barrier separating the
172 * @tail load above from the data stores below. Since the @tail
173 * load is required to compute the branch to fail below.
174 *
175 * A, matches D; the full memory barrier userspace SHOULD issue
176 * after reading the data and before storing the new tail
177 * position.
178 *
179 * See perf_output_put_handle().
180 */
181
182 if (!backward)
183 head += size;
184 else
185 head -= size;
186 } while (local_cmpxchg(&rb->head, offset, head) != offset);
187
188 if (backward) {
189 offset = head;
190 head = (u64)(-head);
191 }
192
193 /*
194 * We rely on the implied barrier() by local_cmpxchg() to ensure
195 * none of the data stores below can be lifted up by the compiler.
196 */
197
198 if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
199 local_add(rb->watermark, &rb->wakeup);
200
201 page_shift = PAGE_SHIFT + page_order(rb);
202
203 handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
204 offset &= (1UL << page_shift) - 1;
205 handle->addr = rb->data_pages[handle->page] + offset;
206 handle->size = (1UL << page_shift) - offset;
207
208 if (unlikely(have_lost)) {
209 struct perf_sample_data sample_data;
210
211 lost_event.header.size = sizeof(lost_event);
212 lost_event.header.type = PERF_RECORD_LOST;
213 lost_event.header.misc = 0;
214 lost_event.id = event->id;
215 lost_event.lost = local_xchg(&rb->lost, 0);
216
217 perf_event_header__init_id(&lost_event.header,
218 &sample_data, event);
219 perf_output_put(handle, lost_event);
220 perf_event__output_id_sample(event, handle, &sample_data);
221 }
222
223 return 0;
224
225fail:
226 local_inc(&rb->lost);
227 perf_output_put_handle(handle);
228out:
229 rcu_read_unlock();
230
231 return -ENOSPC;
232}
233
234int perf_output_begin_forward(struct perf_output_handle *handle,
235 struct perf_event *event, unsigned int size)
236{
237 return __perf_output_begin(handle, event, size, false);
238}
239
240int perf_output_begin_backward(struct perf_output_handle *handle,
241 struct perf_event *event, unsigned int size)
242{
243 return __perf_output_begin(handle, event, size, true);
244}
245
246int perf_output_begin(struct perf_output_handle *handle,
247 struct perf_event *event, unsigned int size)
248{
249
250 return __perf_output_begin(handle, event, size,
251 unlikely(is_write_backward(event)));
252}
253
254unsigned int perf_output_copy(struct perf_output_handle *handle,
255 const void *buf, unsigned int len)
256{
257 return __output_copy(handle, buf, len);
258}
259
260unsigned int perf_output_skip(struct perf_output_handle *handle,
261 unsigned int len)
262{
263 return __output_skip(handle, NULL, len);
264}
265
266void perf_output_end(struct perf_output_handle *handle)
267{
268 perf_output_put_handle(handle);
269 rcu_read_unlock();
270}
271
272static void
273ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
274{
275 long max_size = perf_data_size(rb);
276
277 if (watermark)
278 rb->watermark = min(max_size, watermark);
279
280 if (!rb->watermark)
281 rb->watermark = max_size / 2;
282
283 if (flags & RING_BUFFER_WRITABLE)
284 rb->overwrite = 0;
285 else
286 rb->overwrite = 1;
287
288 atomic_set(&rb->refcount, 1);
289
290 INIT_LIST_HEAD(&rb->event_list);
291 spin_lock_init(&rb->event_lock);
292
293 /*
294 * perf_output_begin() only checks rb->paused, therefore
295 * rb->paused must be true if we have no pages for output.
296 */
297 if (!rb->nr_pages)
298 rb->paused = 1;
299}
300
301void perf_aux_output_flag(struct perf_output_handle *handle, u64 flags)
302{
303 /*
304 * OVERWRITE is determined by perf_aux_output_end() and can't
305 * be passed in directly.
306 */
307 if (WARN_ON_ONCE(flags & PERF_AUX_FLAG_OVERWRITE))
308 return;
309
310 handle->aux_flags |= flags;
311}
312EXPORT_SYMBOL_GPL(perf_aux_output_flag);
313
314/*
315 * This is called before hardware starts writing to the AUX area to
316 * obtain an output handle and make sure there's room in the buffer.
317 * When the capture completes, call perf_aux_output_end() to commit
318 * the recorded data to the buffer.
319 *
320 * The ordering is similar to that of perf_output_{begin,end}, with
321 * the exception of (B), which should be taken care of by the pmu
322 * driver, since ordering rules will differ depending on hardware.
323 *
324 * Call this from pmu::start(); see the comment in perf_aux_output_end()
325 * about its use in pmu callbacks. Both can also be called from the PMI
326 * handler if needed.
327 */
328void *perf_aux_output_begin(struct perf_output_handle *handle,
329 struct perf_event *event)
330{
331 struct perf_event *output_event = event;
332 unsigned long aux_head, aux_tail;
333 struct ring_buffer *rb;
334
335 if (output_event->parent)
336 output_event = output_event->parent;
337
338 /*
339 * Since this will typically be open across pmu::add/pmu::del, we
340 * grab ring_buffer's refcount instead of holding rcu read lock
341 * to make sure it doesn't disappear under us.
342 */
343 rb = ring_buffer_get(output_event);
344 if (!rb)
345 return NULL;
346
347 if (!rb_has_aux(rb))
348 goto err;
349
350 /*
351 * If aux_mmap_count is zero, the aux buffer is in perf_mmap_close(),
352 * about to get freed, so we leave immediately.
353 *
354 * Checking rb::aux_mmap_count and rb::refcount has to be done in
355 * the same order, see perf_mmap_close. Otherwise we end up freeing
356 * aux pages in this path, which is a bug, because in_atomic().
357 */
358 if (!atomic_read(&rb->aux_mmap_count))
359 goto err;
360
361 if (!atomic_inc_not_zero(&rb->aux_refcount))
362 goto err;
363
364 /*
365 * Nesting is not supported for AUX area, make sure nested
366 * writers are caught early
367 */
368 if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))
369 goto err_put;
370
371 aux_head = rb->aux_head;
372
373 handle->rb = rb;
374 handle->event = event;
375 handle->head = aux_head;
376 handle->size = 0;
377 handle->aux_flags = 0;
378
379 /*
380 * In overwrite mode, AUX data stores do not depend on aux_tail,
381 * therefore (A) control dependency barrier does not exist. The
382 * (B) <-> (C) ordering is still observed by the pmu driver.
383 */
384 if (!rb->aux_overwrite) {
385 aux_tail = READ_ONCE(rb->user_page->aux_tail);
386 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
387 if (aux_head - aux_tail < perf_aux_size(rb))
388 handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
389
390 /*
391 * handle->size computation depends on aux_tail load; this forms a
392 * control dependency barrier separating aux_tail load from aux data
393 * store that will be enabled on successful return
394 */
395 if (!handle->size) { /* A, matches D */
396 event->pending_disable = 1;
397 perf_output_wakeup(handle);
398 local_set(&rb->aux_nest, 0);
399 goto err_put;
400 }
401 }
402
403 return handle->rb->aux_priv;
404
405err_put:
406 /* can't be last */
407 rb_free_aux(rb);
408
409err:
410 ring_buffer_put(rb);
411 handle->event = NULL;
412
413 return NULL;
414}
415EXPORT_SYMBOL_GPL(perf_aux_output_begin);
416
417static bool __always_inline rb_need_aux_wakeup(struct ring_buffer *rb)
418{
419 if (rb->aux_overwrite)
420 return false;
421
422 if (rb->aux_head - rb->aux_wakeup >= rb->aux_watermark) {
423 rb->aux_wakeup = rounddown(rb->aux_head, rb->aux_watermark);
424 return true;
425 }
426
427 return false;
428}
429
430/*
431 * Commit the data written by hardware into the ring buffer by adjusting
432 * aux_head and posting a PERF_RECORD_AUX into the perf buffer. It is the
433 * pmu driver's responsibility to observe ordering rules of the hardware,
434 * so that all the data is externally visible before this is called.
435 *
436 * Note: this has to be called from pmu::stop() callback, as the assumption
437 * of the AUX buffer management code is that after pmu::stop(), the AUX
438 * transaction must be stopped and therefore drop the AUX reference count.
439 */
440void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
441{
442 bool wakeup = !!(handle->aux_flags & PERF_AUX_FLAG_TRUNCATED);
443 struct ring_buffer *rb = handle->rb;
444 unsigned long aux_head;
445
446 /* in overwrite mode, driver provides aux_head via handle */
447 if (rb->aux_overwrite) {
448 handle->aux_flags |= PERF_AUX_FLAG_OVERWRITE;
449
450 aux_head = handle->head;
451 rb->aux_head = aux_head;
452 } else {
453 handle->aux_flags &= ~PERF_AUX_FLAG_OVERWRITE;
454
455 aux_head = rb->aux_head;
456 rb->aux_head += size;
457 }
458
459 if (size || handle->aux_flags) {
460 /*
461 * Only send RECORD_AUX if we have something useful to communicate
462 */
463
464 perf_event_aux_event(handle->event, aux_head, size,
465 handle->aux_flags);
466 }
467
468 rb->user_page->aux_head = rb->aux_head;
469 if (rb_need_aux_wakeup(rb))
470 wakeup = true;
471
472 if (wakeup) {
473 if (handle->aux_flags & PERF_AUX_FLAG_TRUNCATED)
474 handle->event->pending_disable = 1;
475 perf_output_wakeup(handle);
476 }
477
478 handle->event = NULL;
479
480 local_set(&rb->aux_nest, 0);
481 /* can't be last */
482 rb_free_aux(rb);
483 ring_buffer_put(rb);
484}
485EXPORT_SYMBOL_GPL(perf_aux_output_end);
486
487/*
488 * Skip over a given number of bytes in the AUX buffer, due to, for example,
489 * hardware's alignment constraints.
490 */
491int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
492{
493 struct ring_buffer *rb = handle->rb;
494
495 if (size > handle->size)
496 return -ENOSPC;
497
498 rb->aux_head += size;
499
500 rb->user_page->aux_head = rb->aux_head;
501 if (rb_need_aux_wakeup(rb)) {
502 perf_output_wakeup(handle);
503 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
504 }
505
506 handle->head = rb->aux_head;
507 handle->size -= size;
508
509 return 0;
510}
511EXPORT_SYMBOL_GPL(perf_aux_output_skip);
512
513void *perf_get_aux(struct perf_output_handle *handle)
514{
515 /* this is only valid between perf_aux_output_begin and *_end */
516 if (!handle->event)
517 return NULL;
518
519 return handle->rb->aux_priv;
520}
521EXPORT_SYMBOL_GPL(perf_get_aux);
522
523#define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
524
525static struct page *rb_alloc_aux_page(int node, int order)
526{
527 struct page *page;
528
529 if (order > MAX_ORDER)
530 order = MAX_ORDER;
531
532 do {
533 page = alloc_pages_node(node, PERF_AUX_GFP, order);
534 } while (!page && order--);
535
536 if (page && order) {
537 /*
538 * Communicate the allocation size to the driver:
539 * if we managed to secure a high-order allocation,
540 * set its first page's private to this order;
541 * !PagePrivate(page) means it's just a normal page.
542 */
543 split_page(page, order);
544 SetPagePrivate(page);
545 set_page_private(page, order);
546 }
547
548 return page;
549}
550
551static void rb_free_aux_page(struct ring_buffer *rb, int idx)
552{
553 struct page *page = virt_to_page(rb->aux_pages[idx]);
554
555 ClearPagePrivate(page);
556 page->mapping = NULL;
557 __free_page(page);
558}
559
560static void __rb_free_aux(struct ring_buffer *rb)
561{
562 int pg;
563
564 /*
565 * Should never happen, the last reference should be dropped from
566 * perf_mmap_close() path, which first stops aux transactions (which
567 * in turn are the atomic holders of aux_refcount) and then does the
568 * last rb_free_aux().
569 */
570 WARN_ON_ONCE(in_atomic());
571
572 if (rb->aux_priv) {
573 rb->free_aux(rb->aux_priv);
574 rb->free_aux = NULL;
575 rb->aux_priv = NULL;
576 }
577
578 if (rb->aux_nr_pages) {
579 for (pg = 0; pg < rb->aux_nr_pages; pg++)
580 rb_free_aux_page(rb, pg);
581
582 kfree(rb->aux_pages);
583 rb->aux_nr_pages = 0;
584 }
585}
586
587int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
588 pgoff_t pgoff, int nr_pages, long watermark, int flags)
589{
590 bool overwrite = !(flags & RING_BUFFER_WRITABLE);
591 int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
592 int ret = -ENOMEM, max_order = 0;
593
594 if (!has_aux(event))
595 return -EOPNOTSUPP;
596
597 if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
598 /*
599 * We need to start with the max_order that fits in nr_pages,
600 * not the other way around, hence ilog2() and not get_order.
601 */
602 max_order = ilog2(nr_pages);
603
604 /*
605 * PMU requests more than one contiguous chunks of memory
606 * for SW double buffering
607 */
608 if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_SW_DOUBLEBUF) &&
609 !overwrite) {
610 if (!max_order)
611 return -EINVAL;
612
613 max_order--;
614 }
615 }
616
617 rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
618 if (!rb->aux_pages)
619 return -ENOMEM;
620
621 rb->free_aux = event->pmu->free_aux;
622 for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;) {
623 struct page *page;
624 int last, order;
625
626 order = min(max_order, ilog2(nr_pages - rb->aux_nr_pages));
627 page = rb_alloc_aux_page(node, order);
628 if (!page)
629 goto out;
630
631 for (last = rb->aux_nr_pages + (1 << page_private(page));
632 last > rb->aux_nr_pages; rb->aux_nr_pages++)
633 rb->aux_pages[rb->aux_nr_pages] = page_address(page++);
634 }
635
636 /*
637 * In overwrite mode, PMUs that don't support SG may not handle more
638 * than one contiguous allocation, since they rely on PMI to do double
639 * buffering. In this case, the entire buffer has to be one contiguous
640 * chunk.
641 */
642 if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) &&
643 overwrite) {
644 struct page *page = virt_to_page(rb->aux_pages[0]);
645
646 if (page_private(page) != max_order)
647 goto out;
648 }
649
650 rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
651 overwrite);
652 if (!rb->aux_priv)
653 goto out;
654
655 ret = 0;
656
657 /*
658 * aux_pages (and pmu driver's private data, aux_priv) will be
659 * referenced in both producer's and consumer's contexts, thus
660 * we keep a refcount here to make sure either of the two can
661 * reference them safely.
662 */
663 atomic_set(&rb->aux_refcount, 1);
664
665 rb->aux_overwrite = overwrite;
666 rb->aux_watermark = watermark;
667
668 if (!rb->aux_watermark && !rb->aux_overwrite)
669 rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);
670
671out:
672 if (!ret)
673 rb->aux_pgoff = pgoff;
674 else
675 __rb_free_aux(rb);
676
677 return ret;
678}
679
680void rb_free_aux(struct ring_buffer *rb)
681{
682 if (atomic_dec_and_test(&rb->aux_refcount))
683 __rb_free_aux(rb);
684}
685
686#ifndef CONFIG_PERF_USE_VMALLOC
687
688/*
689 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
690 */
691
692static struct page *
693__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
694{
695 if (pgoff > rb->nr_pages)
696 return NULL;
697
698 if (pgoff == 0)
699 return virt_to_page(rb->user_page);
700
701 return virt_to_page(rb->data_pages[pgoff - 1]);
702}
703
704static void *perf_mmap_alloc_page(int cpu)
705{
706 struct page *page;
707 int node;
708
709 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
710 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
711 if (!page)
712 return NULL;
713
714 return page_address(page);
715}
716
717struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
718{
719 struct ring_buffer *rb;
720 unsigned long size;
721 int i;
722
723 size = sizeof(struct ring_buffer);
724 size += nr_pages * sizeof(void *);
725
726 rb = kzalloc(size, GFP_KERNEL);
727 if (!rb)
728 goto fail;
729
730 rb->user_page = perf_mmap_alloc_page(cpu);
731 if (!rb->user_page)
732 goto fail_user_page;
733
734 for (i = 0; i < nr_pages; i++) {
735 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
736 if (!rb->data_pages[i])
737 goto fail_data_pages;
738 }
739
740 rb->nr_pages = nr_pages;
741
742 ring_buffer_init(rb, watermark, flags);
743
744 return rb;
745
746fail_data_pages:
747 for (i--; i >= 0; i--)
748 free_page((unsigned long)rb->data_pages[i]);
749
750 free_page((unsigned long)rb->user_page);
751
752fail_user_page:
753 kfree(rb);
754
755fail:
756 return NULL;
757}
758
759static void perf_mmap_free_page(unsigned long addr)
760{
761 struct page *page = virt_to_page((void *)addr);
762
763 page->mapping = NULL;
764 __free_page(page);
765}
766
767void rb_free(struct ring_buffer *rb)
768{
769 int i;
770
771 perf_mmap_free_page((unsigned long)rb->user_page);
772 for (i = 0; i < rb->nr_pages; i++)
773 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
774 kfree(rb);
775}
776
777#else
778static int data_page_nr(struct ring_buffer *rb)
779{
780 return rb->nr_pages << page_order(rb);
781}
782
783static struct page *
784__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
785{
786 /* The '>' counts in the user page. */
787 if (pgoff > data_page_nr(rb))
788 return NULL;
789
790 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
791}
792
793static void perf_mmap_unmark_page(void *addr)
794{
795 struct page *page = vmalloc_to_page(addr);
796
797 page->mapping = NULL;
798}
799
800static void rb_free_work(struct work_struct *work)
801{
802 struct ring_buffer *rb;
803 void *base;
804 int i, nr;
805
806 rb = container_of(work, struct ring_buffer, work);
807 nr = data_page_nr(rb);
808
809 base = rb->user_page;
810 /* The '<=' counts in the user page. */
811 for (i = 0; i <= nr; i++)
812 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
813
814 vfree(base);
815 kfree(rb);
816}
817
818void rb_free(struct ring_buffer *rb)
819{
820 schedule_work(&rb->work);
821}
822
823struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
824{
825 struct ring_buffer *rb;
826 unsigned long size;
827 void *all_buf;
828
829 size = sizeof(struct ring_buffer);
830 size += sizeof(void *);
831
832 rb = kzalloc(size, GFP_KERNEL);
833 if (!rb)
834 goto fail;
835
836 INIT_WORK(&rb->work, rb_free_work);
837
838 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
839 if (!all_buf)
840 goto fail_all_buf;
841
842 rb->user_page = all_buf;
843 rb->data_pages[0] = all_buf + PAGE_SIZE;
844 if (nr_pages) {
845 rb->nr_pages = 1;
846 rb->page_order = ilog2(nr_pages);
847 }
848
849 ring_buffer_init(rb, watermark, flags);
850
851 return rb;
852
853fail_all_buf:
854 kfree(rb);
855
856fail:
857 return NULL;
858}
859
860#endif
861
862struct page *
863perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
864{
865 if (rb->aux_nr_pages) {
866 /* above AUX space */
867 if (pgoff > rb->aux_pgoff + rb->aux_nr_pages)
868 return NULL;
869
870 /* AUX space */
871 if (pgoff >= rb->aux_pgoff) {
872 int aux_pgoff = array_index_nospec(pgoff - rb->aux_pgoff, rb->aux_nr_pages);
873 return virt_to_page(rb->aux_pages[aux_pgoff]);
874 }
875 }
876
877 return __perf_mmap_to_page(rb, pgoff);
878}