root/kernel/events/ring_buffer.c

DEFINITIONS

1. perf_output_wakeup
2. perf_output_get_handle
3. perf_output_put_handle
4. ring_buffer_has_space
5. __perf_output_begin
6. perf_output_begin_forward
7. perf_output_begin_backward
8. perf_output_begin
9. perf_output_copy
10. perf_output_skip
11. perf_output_end
12. ring_buffer_init
13. perf_aux_output_flag
14. perf_aux_output_begin
15. rb_need_aux_wakeup
16. perf_aux_output_end
17. perf_aux_output_skip
18. perf_get_aux
19. rb_alloc_aux_page
20. rb_free_aux_page
21. __rb_free_aux
22. rb_alloc_aux
23. rb_free_aux
24. __perf_mmap_to_page
25. perf_mmap_alloc_page
26. rb_alloc
27. perf_mmap_free_page
28. rb_free
29. data_page_nr
30. __perf_mmap_to_page
31. perf_mmap_unmark_page
32. rb_free_work
33. rb_free
34. rb_alloc
35. perf_mmap_to_page

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