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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 <pzijlstr@redhat.com>
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
17#include "internal.h"
18
19static void perf_output_wakeup(struct perf_output_handle *handle)
20{
21 atomic_set(&handle->rb->poll, POLL_IN);
22
23 handle->event->pending_wakeup = 1;
24 irq_work_queue(&handle->event->pending);
25}
26
27/*
28 * We need to ensure a later event_id doesn't publish a head when a former
29 * event isn't done writing. However since we need to deal with NMIs we
30 * cannot fully serialize things.
31 *
32 * We only publish the head (and generate a wakeup) when the outer-most
33 * event completes.
34 */
35static void perf_output_get_handle(struct perf_output_handle *handle)
36{
37 struct ring_buffer *rb = handle->rb;
38
39 preempt_disable();
40 local_inc(&rb->nest);
41 handle->wakeup = local_read(&rb->wakeup);
42}
43
44static void perf_output_put_handle(struct perf_output_handle *handle)
45{
46 struct ring_buffer *rb = handle->rb;
47 unsigned long head;
48
49again:
50 head = local_read(&rb->head);
51
52 /*
53 * IRQ/NMI can happen here, which means we can miss a head update.
54 */
55
56 if (!local_dec_and_test(&rb->nest))
57 goto out;
58
59 /*
60 * Since the mmap() consumer (userspace) can run on a different CPU:
61 *
62 * kernel user
63 *
64 * if (LOAD ->data_tail) { LOAD ->data_head
65 * (A) smp_rmb() (C)
66 * STORE $data LOAD $data
67 * smp_wmb() (B) smp_mb() (D)
68 * STORE ->data_head STORE ->data_tail
69 * }
70 *
71 * Where A pairs with D, and B pairs with C.
72 *
73 * In our case (A) is a control dependency that separates the load of
74 * the ->data_tail and the stores of $data. In case ->data_tail
75 * indicates there is no room in the buffer to store $data we do not.
76 *
77 * D needs to be a full barrier since it separates the data READ
78 * from the tail WRITE.
79 *
80 * For B a WMB is sufficient since it separates two WRITEs, and for C
81 * an RMB is sufficient since it separates two READs.
82 *
83 * See perf_output_begin().
84 */
85 smp_wmb(); /* B, matches C */
86 rb->user_page->data_head = head;
87
88 /*
89 * Now check if we missed an update -- rely on previous implied
90 * compiler barriers to force a re-read.
91 */
92 if (unlikely(head != local_read(&rb->head))) {
93 local_inc(&rb->nest);
94 goto again;
95 }
96
97 if (handle->wakeup != local_read(&rb->wakeup))
98 perf_output_wakeup(handle);
99
100out:
101 preempt_enable();
102}
103
104int perf_output_begin(struct perf_output_handle *handle,
105 struct perf_event *event, unsigned int size)
106{
107 struct ring_buffer *rb;
108 unsigned long tail, offset, head;
109 int have_lost, page_shift;
110 struct {
111 struct perf_event_header header;
112 u64 id;
113 u64 lost;
114 } lost_event;
115
116 rcu_read_lock();
117 /*
118 * For inherited events we send all the output towards the parent.
119 */
120 if (event->parent)
121 event = event->parent;
122
123 rb = rcu_dereference(event->rb);
124 if (unlikely(!rb))
125 goto out;
126
127 if (unlikely(!rb->nr_pages))
128 goto out;
129
130 handle->rb = rb;
131 handle->event = event;
132
133 have_lost = local_read(&rb->lost);
134 if (unlikely(have_lost)) {
135 size += sizeof(lost_event);
136 if (event->attr.sample_id_all)
137 size += event->id_header_size;
138 }
139
140 perf_output_get_handle(handle);
141
142 do {
143 tail = ACCESS_ONCE(rb->user_page->data_tail);
144 offset = head = local_read(&rb->head);
145 if (!rb->overwrite &&
146 unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
147 goto fail;
148
149 /*
150 * The above forms a control dependency barrier separating the
151 * @tail load above from the data stores below. Since the @tail
152 * load is required to compute the branch to fail below.
153 *
154 * A, matches D; the full memory barrier userspace SHOULD issue
155 * after reading the data and before storing the new tail
156 * position.
157 *
158 * See perf_output_put_handle().
159 */
160
161 head += size;
162 } while (local_cmpxchg(&rb->head, offset, head) != offset);
163
164 /*
165 * We rely on the implied barrier() by local_cmpxchg() to ensure
166 * none of the data stores below can be lifted up by the compiler.
167 */
168
169 if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
170 local_add(rb->watermark, &rb->wakeup);
171
172 page_shift = PAGE_SHIFT + page_order(rb);
173
174 handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
175 offset &= (1UL << page_shift) - 1;
176 handle->addr = rb->data_pages[handle->page] + offset;
177 handle->size = (1UL << page_shift) - offset;
178
179 if (unlikely(have_lost)) {
180 struct perf_sample_data sample_data;
181
182 lost_event.header.size = sizeof(lost_event);
183 lost_event.header.type = PERF_RECORD_LOST;
184 lost_event.header.misc = 0;
185 lost_event.id = event->id;
186 lost_event.lost = local_xchg(&rb->lost, 0);
187
188 perf_event_header__init_id(&lost_event.header,
189 &sample_data, event);
190 perf_output_put(handle, lost_event);
191 perf_event__output_id_sample(event, handle, &sample_data);
192 }
193
194 return 0;
195
196fail:
197 local_inc(&rb->lost);
198 perf_output_put_handle(handle);
199out:
200 rcu_read_unlock();
201
202 return -ENOSPC;
203}
204
205unsigned int perf_output_copy(struct perf_output_handle *handle,
206 const void *buf, unsigned int len)
207{
208 return __output_copy(handle, buf, len);
209}
210
211unsigned int perf_output_skip(struct perf_output_handle *handle,
212 unsigned int len)
213{
214 return __output_skip(handle, NULL, len);
215}
216
217void perf_output_end(struct perf_output_handle *handle)
218{
219 perf_output_put_handle(handle);
220 rcu_read_unlock();
221}
222
223static void
224ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
225{
226 long max_size = perf_data_size(rb);
227
228 if (watermark)
229 rb->watermark = min(max_size, watermark);
230
231 if (!rb->watermark)
232 rb->watermark = max_size / 2;
233
234 if (flags & RING_BUFFER_WRITABLE)
235 rb->overwrite = 0;
236 else
237 rb->overwrite = 1;
238
239 atomic_set(&rb->refcount, 1);
240
241 INIT_LIST_HEAD(&rb->event_list);
242 spin_lock_init(&rb->event_lock);
243}
244
245#ifndef CONFIG_PERF_USE_VMALLOC
246
247/*
248 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
249 */
250
251struct page *
252perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
253{
254 if (pgoff > rb->nr_pages)
255 return NULL;
256
257 if (pgoff == 0)
258 return virt_to_page(rb->user_page);
259
260 return virt_to_page(rb->data_pages[pgoff - 1]);
261}
262
263static void *perf_mmap_alloc_page(int cpu)
264{
265 struct page *page;
266 int node;
267
268 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
269 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
270 if (!page)
271 return NULL;
272
273 return page_address(page);
274}
275
276struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
277{
278 struct ring_buffer *rb;
279 unsigned long size;
280 int i;
281
282 size = sizeof(struct ring_buffer);
283 size += nr_pages * sizeof(void *);
284
285 rb = kzalloc(size, GFP_KERNEL);
286 if (!rb)
287 goto fail;
288
289 rb->user_page = perf_mmap_alloc_page(cpu);
290 if (!rb->user_page)
291 goto fail_user_page;
292
293 for (i = 0; i < nr_pages; i++) {
294 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
295 if (!rb->data_pages[i])
296 goto fail_data_pages;
297 }
298
299 rb->nr_pages = nr_pages;
300
301 ring_buffer_init(rb, watermark, flags);
302
303 return rb;
304
305fail_data_pages:
306 for (i--; i >= 0; i--)
307 free_page((unsigned long)rb->data_pages[i]);
308
309 free_page((unsigned long)rb->user_page);
310
311fail_user_page:
312 kfree(rb);
313
314fail:
315 return NULL;
316}
317
318static void perf_mmap_free_page(unsigned long addr)
319{
320 struct page *page = virt_to_page((void *)addr);
321
322 page->mapping = NULL;
323 __free_page(page);
324}
325
326void rb_free(struct ring_buffer *rb)
327{
328 int i;
329
330 perf_mmap_free_page((unsigned long)rb->user_page);
331 for (i = 0; i < rb->nr_pages; i++)
332 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
333 kfree(rb);
334}
335
336#else
337static int data_page_nr(struct ring_buffer *rb)
338{
339 return rb->nr_pages << page_order(rb);
340}
341
342struct page *
343perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
344{
345 /* The '>' counts in the user page. */
346 if (pgoff > data_page_nr(rb))
347 return NULL;
348
349 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
350}
351
352static void perf_mmap_unmark_page(void *addr)
353{
354 struct page *page = vmalloc_to_page(addr);
355
356 page->mapping = NULL;
357}
358
359static void rb_free_work(struct work_struct *work)
360{
361 struct ring_buffer *rb;
362 void *base;
363 int i, nr;
364
365 rb = container_of(work, struct ring_buffer, work);
366 nr = data_page_nr(rb);
367
368 base = rb->user_page;
369 /* The '<=' counts in the user page. */
370 for (i = 0; i <= nr; i++)
371 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
372
373 vfree(base);
374 kfree(rb);
375}
376
377void rb_free(struct ring_buffer *rb)
378{
379 schedule_work(&rb->work);
380}
381
382struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
383{
384 struct ring_buffer *rb;
385 unsigned long size;
386 void *all_buf;
387
388 size = sizeof(struct ring_buffer);
389 size += sizeof(void *);
390
391 rb = kzalloc(size, GFP_KERNEL);
392 if (!rb)
393 goto fail;
394
395 INIT_WORK(&rb->work, rb_free_work);
396
397 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
398 if (!all_buf)
399 goto fail_all_buf;
400
401 rb->user_page = all_buf;
402 rb->data_pages[0] = all_buf + PAGE_SIZE;
403 rb->page_order = ilog2(nr_pages);
404 rb->nr_pages = !!nr_pages;
405
406 ring_buffer_init(rb, watermark, flags);
407
408 return rb;
409
410fail_all_buf:
411 kfree(rb);
412
413fail:
414 return NULL;
415}
416
417#endif
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}