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