summaryrefslogtreecommitdiffstats
path: root/tools/profiler/core/memory_hooks.cpp
blob: 59e87d607c2b98f3883f34df13441b446b4865b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "memory_hooks.h"

#include "nscore.h"

#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/FastBernoulliTrial.h"
#include "mozilla/IntegerPrintfMacros.h"
#include "mozilla/JSONWriter.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/PlatformMutex.h"
#include "mozilla/ProfilerCounts.h"
#include "mozilla/ThreadLocal.h"

#include "GeckoProfiler.h"
#include "prenv.h"
#include "replace_malloc.h"

#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef XP_WIN
#  include <windows.h>
#  include <process.h>
#else
#  include <pthread.h>
#  include <sys/types.h>
#  include <unistd.h>
#endif

#ifdef ANDROID
#  include <android/log.h>
#endif

// The counters start out as a nullptr, and then get initialized only once. They
// are never destroyed, as it would cause race conditions for the memory hooks
// that use the counters. This helps guard against potentially expensive
// operations like using a mutex.
//
// In addition, this is a raw pointer and not a UniquePtr, as the counter
// machinery will try and de-register itself from the profiler. This could
// happen after the profiler and its PSMutex was already destroyed, resulting in
// a crash.
static ProfilerCounterTotal* sCounter;

// The gBernoulli value starts out as a nullptr, and only gets initialized once.
// It then lives for the entire lifetime of the process. It cannot be deleted
// without additional multi-threaded protections, since if we deleted it during
// profiler_stop then there could be a race between threads already in a
// memory hook that might try to access the value after or during deletion.
static mozilla::FastBernoulliTrial* gBernoulli;

namespace mozilla::profiler {

//---------------------------------------------------------------------------
// Utilities
//---------------------------------------------------------------------------

// Returns true or or false depending on whether the marker was actually added
// or not.
static bool profiler_add_native_allocation_marker(int64_t aSize,
                                                  uintptr_t aMemoryAddress) {
  if (!profiler_thread_is_being_profiled_for_markers(
          profiler_main_thread_id())) {
    return false;
  }

  // Because native allocations may be intercepted anywhere, blocking while
  // locking the profiler mutex here could end up causing a deadlock if another
  // mutex is taken, which the profiler may indirectly need elsewhere.
  // See bug 1642726 for such a scenario.
  // So instead we bail out if the mutex is already locked. Native allocations
  // are statistically sampled anyway, so missing a few because of this is
  // acceptable.
  if (profiler_is_locked_on_current_thread()) {
    return false;
  }

  struct NativeAllocationMarker {
    static constexpr mozilla::Span<const char> MarkerTypeName() {
      return mozilla::MakeStringSpan("Native allocation");
    }
    static void StreamJSONMarkerData(
        mozilla::baseprofiler::SpliceableJSONWriter& aWriter, int64_t aSize,
        uintptr_t aMemoryAddress, ProfilerThreadId aThreadId) {
      aWriter.IntProperty("size", aSize);
      aWriter.IntProperty("memoryAddress",
                          static_cast<int64_t>(aMemoryAddress));
      // Tech note: If `ToNumber()` returns a uint64_t, the conversion to
      // int64_t is "implementation-defined" before C++20. This is acceptable
      // here, because this is a one-way conversion to a unique identifier
      // that's used to visually separate data by thread on the front-end.
      aWriter.IntProperty("threadId",
                          static_cast<int64_t>(aThreadId.ToNumber()));
    }
    static mozilla::MarkerSchema MarkerTypeDisplay() {
      return mozilla::MarkerSchema::SpecialFrontendLocation{};
    }
  };

  profiler_add_marker("Native allocation", geckoprofiler::category::OTHER,
                      {MarkerThreadId::MainThread(), MarkerStack::Capture()},
                      NativeAllocationMarker{}, aSize, aMemoryAddress,
                      profiler_current_thread_id());
  return true;
}

static malloc_table_t gMallocTable;

// This is only needed because of the |const void*| vs |void*| arg mismatch.
static size_t MallocSizeOf(const void* aPtr) {
  return gMallocTable.malloc_usable_size(const_cast<void*>(aPtr));
}

// The values for the Bernoulli trial are taken from DMD. According to DMD:
//
//   In testing, a probability of 0.003 resulted in ~25% of heap blocks getting
//   a stack trace and ~80% of heap bytes getting a stack trace. (This is
//   possible because big heap blocks are more likely to get a stack trace.)
//
//   The random number seeds are arbitrary and were obtained from random.org.
//
// However this value resulted in a lot of slowdown since the profiler stacks
// are pretty heavy to collect. The value was lowered to 10% of the original to
// 0.0003.
static void EnsureBernoulliIsInstalled() {
  if (!gBernoulli) {
    // This is only installed once. See the gBernoulli definition for more
    // information.
    gBernoulli =
        new FastBernoulliTrial(0.0003, 0x8e26eeee166bc8ca, 0x56820f304a9c9ae0);
  }
}

// This class provides infallible allocations (they abort on OOM) like
// mozalloc's InfallibleAllocPolicy, except that memory hooks are bypassed. This
// policy is used by the HashSet.
class InfallibleAllocWithoutHooksPolicy {
  static void ExitOnFailure(const void* aP) {
    if (!aP) {
      MOZ_CRASH("Profiler memory hooks out of memory; aborting");
    }
  }

 public:
  template <typename T>
  static T* maybe_pod_malloc(size_t aNumElems) {
    if (aNumElems & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
      return nullptr;
    }
    return (T*)gMallocTable.malloc(aNumElems * sizeof(T));
  }

  template <typename T>
  static T* maybe_pod_calloc(size_t aNumElems) {
    return (T*)gMallocTable.calloc(aNumElems, sizeof(T));
  }

  template <typename T>
  static T* maybe_pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize) {
    if (aNewSize & mozilla::tl::MulOverflowMask<sizeof(T)>::value) {
      return nullptr;
    }
    return (T*)gMallocTable.realloc(aPtr, aNewSize * sizeof(T));
  }

  template <typename T>
  static T* pod_malloc(size_t aNumElems) {
    T* p = maybe_pod_malloc<T>(aNumElems);
    ExitOnFailure(p);
    return p;
  }

  template <typename T>
  static T* pod_calloc(size_t aNumElems) {
    T* p = maybe_pod_calloc<T>(aNumElems);
    ExitOnFailure(p);
    return p;
  }

  template <typename T>
  static T* pod_realloc(T* aPtr, size_t aOldSize, size_t aNewSize) {
    T* p = maybe_pod_realloc(aPtr, aOldSize, aNewSize);
    ExitOnFailure(p);
    return p;
  }

  template <typename T>
  static void free_(T* aPtr, size_t aSize = 0) {
    gMallocTable.free(aPtr);
  }

  static void reportAllocOverflow() { ExitOnFailure(nullptr); }
  bool checkSimulatedOOM() const { return true; }
};

// We can't use mozilla::Mutex because it causes re-entry into the memory hooks.
// Define a custom implementation here.
class Mutex : private ::mozilla::detail::MutexImpl {
 public:
  Mutex() : ::mozilla::detail::MutexImpl() {}

  void Lock() { ::mozilla::detail::MutexImpl::lock(); }
  void Unlock() { ::mozilla::detail::MutexImpl::unlock(); }
};

class MutexAutoLock {
  MutexAutoLock(const MutexAutoLock&) = delete;
  void operator=(const MutexAutoLock&) = delete;

  Mutex& mMutex;

 public:
  explicit MutexAutoLock(Mutex& aMutex) : mMutex(aMutex) { mMutex.Lock(); }
  ~MutexAutoLock() { mMutex.Unlock(); }
};

//---------------------------------------------------------------------------
// Tracked allocations
//---------------------------------------------------------------------------

// The allocation tracker is shared between multiple threads, and is the
// coordinator for knowing when allocations have been tracked. The mutable
// internal state is protected by a mutex, and managed by the methods.
//
// The tracker knows about all the allocations that we have added to the
// profiler. This way, whenever any given piece of memory is freed, we can see
// if it was previously tracked, and we can track its deallocation.

class AllocationTracker {
  // This type tracks all of the allocations that we have captured. This way, we
  // can see if a deallocation is inside of this set. We want to provide a
  // balanced view into the allocations and deallocations.
  typedef mozilla::HashSet<const void*, mozilla::DefaultHasher<const void*>,
                           InfallibleAllocWithoutHooksPolicy>
      AllocationSet;

 public:
  AllocationTracker() : mAllocations(), mMutex() {}

  void AddMemoryAddress(const void* memoryAddress) {
    MutexAutoLock lock(mMutex);
    if (!mAllocations.put(memoryAddress)) {
      MOZ_CRASH("Out of memory while tracking native allocations.");
    };
  }

  void Reset() {
    MutexAutoLock lock(mMutex);
    mAllocations.clearAndCompact();
  }

  // Returns true when the memory address is found and removed, otherwise that
  // memory address is not being tracked and it returns false.
  bool RemoveMemoryAddressIfFound(const void* memoryAddress) {
    MutexAutoLock lock(mMutex);

    auto ptr = mAllocations.lookup(memoryAddress);
    if (ptr) {
      // The memory was present. It no longer needs to be tracked.
      mAllocations.remove(ptr);
      return true;
    }

    return false;
  }

 private:
  AllocationSet mAllocations;
  Mutex mMutex MOZ_UNANNOTATED;
};

static AllocationTracker* gAllocationTracker;

static void EnsureAllocationTrackerIsInstalled() {
  if (!gAllocationTracker) {
    // This is only installed once.
    gAllocationTracker = new AllocationTracker();
  }
}

//---------------------------------------------------------------------------
// Per-thread blocking of intercepts
//---------------------------------------------------------------------------

// On MacOS, and Linux the first __thread/thread_local access calls malloc,
// which leads to an infinite loop. So we use pthread-based TLS instead, which
// somehow doesn't have this problem.
#if !defined(XP_DARWIN) && !defined(XP_LINUX)
#  define PROFILER_THREAD_LOCAL(T) MOZ_THREAD_LOCAL(T)
#else
#  define PROFILER_THREAD_LOCAL(T) \
    ::mozilla::detail::ThreadLocal<T, ::mozilla::detail::ThreadLocalKeyStorage>
#endif

// This class is used to determine if allocations on this thread should be
// intercepted or not.
// Creating a ThreadIntercept object on the stack will implicitly block nested
// ones. There are other reasons to block: The feature is off, or we're inside a
// profiler function that is locking a mutex.
class MOZ_RAII ThreadIntercept {
  // When set to true, malloc does not intercept additional allocations. This is
  // needed because collecting stacks creates new allocations. When blocked,
  // these allocations are then ignored by the memory hook.
  static PROFILER_THREAD_LOCAL(bool) tlsIsBlocked;

  // This is a quick flag to check and see if the allocations feature is enabled
  // or disabled.
  static mozilla::Atomic<bool, mozilla::Relaxed> sAllocationsFeatureEnabled;

  // True if this ThreadIntercept has set tlsIsBlocked.
  bool mIsBlockingTLS;

  // True if interception is blocked for any reason.
  bool mIsBlocked;

 public:
  static void Init() {
    tlsIsBlocked.infallibleInit();
    // infallibleInit should zero-initialize, which corresponds to `false`.
    MOZ_ASSERT(!tlsIsBlocked.get());
  }

  ThreadIntercept() {
    // If the allocation interception feature is enabled, and the TLS is not
    // blocked yet, we will block the TLS now, and unblock on destruction.
    mIsBlockingTLS = sAllocationsFeatureEnabled && !tlsIsBlocked.get();
    if (mIsBlockingTLS) {
      MOZ_ASSERT(!tlsIsBlocked.get());
      tlsIsBlocked.set(true);
      // Since this is the top-level ThreadIntercept, interceptions are not
      // blocked unless the profiler itself holds a locked mutex, in which case
      // we don't want to intercept allocations that originate from such a
      // profiler call.
      mIsBlocked = profiler_is_locked_on_current_thread();
    } else {
      // The feature is off, or the TLS was already blocked, then we block this
      // interception.
      mIsBlocked = true;
    }
  }

  ~ThreadIntercept() {
    if (mIsBlockingTLS) {
      MOZ_ASSERT(tlsIsBlocked.get());
      tlsIsBlocked.set(false);
    }
  }

  // Is this ThreadIntercept effectively blocked? (Feature is off, or this
  // ThreadIntercept is nested, or we're inside a locked-Profiler function.)
  bool IsBlocked() const { return mIsBlocked; }

  static void EnableAllocationFeature() { sAllocationsFeatureEnabled = true; }

  static void DisableAllocationFeature() { sAllocationsFeatureEnabled = false; }
};

PROFILER_THREAD_LOCAL(bool) ThreadIntercept::tlsIsBlocked;

mozilla::Atomic<bool, mozilla::Relaxed>
    ThreadIntercept::sAllocationsFeatureEnabled(false);

//---------------------------------------------------------------------------
// malloc/free callbacks
//---------------------------------------------------------------------------

static void AllocCallback(void* aPtr, size_t aReqSize) {
  if (!aPtr) {
    return;
  }

  // The first part of this function does not allocate.
  size_t actualSize = gMallocTable.malloc_usable_size(aPtr);
  if (actualSize > 0) {
    sCounter->Add(actualSize);
  }

  ThreadIntercept threadIntercept;
  if (threadIntercept.IsBlocked()) {
    // Either the native allocations feature is not turned on, or we may be
    // recursing into a memory hook, return. We'll still collect counter
    // information about this allocation, but no stack.
    return;
  }

  AUTO_PROFILER_LABEL("AllocCallback", PROFILER);

  // Perform a bernoulli trial, which will return true or false based on its
  // configured probability. It takes into account the byte size so that
  // larger allocations are weighted heavier than smaller allocations.
  MOZ_ASSERT(gBernoulli,
             "gBernoulli must be properly installed for the memory hooks.");
  if (
      // First perform the Bernoulli trial.
      gBernoulli->trial(actualSize) &&
      // Second, attempt to add a marker if the Bernoulli trial passed.
      profiler_add_native_allocation_marker(
          static_cast<int64_t>(actualSize),
          reinterpret_cast<uintptr_t>(aPtr))) {
    MOZ_ASSERT(gAllocationTracker,
               "gAllocationTracker must be properly installed for the memory "
               "hooks.");
    // Only track the memory if the allocation marker was actually added to the
    // profiler.
    gAllocationTracker->AddMemoryAddress(aPtr);
  }

  // We're ignoring aReqSize here
}

static void FreeCallback(void* aPtr) {
  if (!aPtr) {
    return;
  }

  // The first part of this function does not allocate.
  size_t unsignedSize = MallocSizeOf(aPtr);
  int64_t signedSize = -(static_cast<int64_t>(unsignedSize));
  sCounter->Add(signedSize);

  ThreadIntercept threadIntercept;
  if (threadIntercept.IsBlocked()) {
    // Either the native allocations feature is not turned on, or we may be
    // recursing into a memory hook, return. We'll still collect counter
    // information about this allocation, but no stack.
    return;
  }

  AUTO_PROFILER_LABEL("FreeCallback", PROFILER);

  // Perform a bernoulli trial, which will return true or false based on its
  // configured probability. It takes into account the byte size so that
  // larger allocations are weighted heavier than smaller allocations.
  MOZ_ASSERT(
      gAllocationTracker,
      "gAllocationTracker must be properly installed for the memory hooks.");
  if (gAllocationTracker->RemoveMemoryAddressIfFound(aPtr)) {
    // This size here is negative, indicating a deallocation.
    profiler_add_native_allocation_marker(signedSize,
                                          reinterpret_cast<uintptr_t>(aPtr));
  }
}

}  // namespace mozilla::profiler

//---------------------------------------------------------------------------
// malloc/free interception
//---------------------------------------------------------------------------

using namespace mozilla::profiler;

static void* replace_malloc(size_t aSize) {
  // This must be a call to malloc from outside.  Intercept it.
  void* ptr = gMallocTable.malloc(aSize);
  AllocCallback(ptr, aSize);
  return ptr;
}

static void* replace_calloc(size_t aCount, size_t aSize) {
  void* ptr = gMallocTable.calloc(aCount, aSize);
  AllocCallback(ptr, aCount * aSize);
  return ptr;
}

static void* replace_realloc(void* aOldPtr, size_t aSize) {
  // If |aOldPtr| is nullptr, the call is equivalent to |malloc(aSize)|.
  if (!aOldPtr) {
    return replace_malloc(aSize);
  }

  FreeCallback(aOldPtr);
  void* ptr = gMallocTable.realloc(aOldPtr, aSize);
  if (ptr) {
    AllocCallback(ptr, aSize);
  } else {
    // If realloc fails, we undo the prior operations by re-inserting the old
    // pointer into the live block table. We don't have to do anything with the
    // dead block list because the dead block hasn't yet been inserted. The
    // block will end up looking like it was allocated for the first time here,
    // which is untrue, and the slop bytes will be zero, which may be untrue.
    // But this case is rare and doing better isn't worth the effort.
    AllocCallback(aOldPtr, gMallocTable.malloc_usable_size(aOldPtr));
  }
  return ptr;
}

static void* replace_memalign(size_t aAlignment, size_t aSize) {
  void* ptr = gMallocTable.memalign(aAlignment, aSize);
  AllocCallback(ptr, aSize);
  return ptr;
}

static void replace_free(void* aPtr) {
  FreeCallback(aPtr);
  gMallocTable.free(aPtr);
}

static void* replace_moz_arena_malloc(arena_id_t aArena, size_t aSize) {
  void* ptr = gMallocTable.moz_arena_malloc(aArena, aSize);
  AllocCallback(ptr, aSize);
  return ptr;
}

static void* replace_moz_arena_calloc(arena_id_t aArena, size_t aCount,
                                      size_t aSize) {
  void* ptr = gMallocTable.moz_arena_calloc(aArena, aCount, aSize);
  AllocCallback(ptr, aCount * aSize);
  return ptr;
}

static void* replace_moz_arena_realloc(arena_id_t aArena, void* aPtr,
                                       size_t aSize) {
  void* ptr = gMallocTable.moz_arena_realloc(aArena, aPtr, aSize);
  AllocCallback(ptr, aSize);
  return ptr;
}

static void replace_moz_arena_free(arena_id_t aArena, void* aPtr) {
  FreeCallback(aPtr);
  gMallocTable.moz_arena_free(aArena, aPtr);
}

static void* replace_moz_arena_memalign(arena_id_t aArena, size_t aAlignment,
                                        size_t aSize) {
  void* ptr = gMallocTable.moz_arena_memalign(aArena, aAlignment, aSize);
  AllocCallback(ptr, aSize);
  return ptr;
}

// we have to replace these or jemalloc will assume we don't implement any
// of the arena replacements!
static arena_id_t replace_moz_create_arena_with_params(
    arena_params_t* aParams) {
  return gMallocTable.moz_create_arena_with_params(aParams);
}

static void replace_moz_dispose_arena(arena_id_t aArenaId) {
  return gMallocTable.moz_dispose_arena(aArenaId);
}

static void replace_moz_set_max_dirty_page_modifier(int32_t aModifier) {
  return gMallocTable.moz_set_max_dirty_page_modifier(aModifier);
}

// Must come after all the replace_* funcs
void replace_init(malloc_table_t* aMallocTable, ReplaceMallocBridge** aBridge) {
  gMallocTable = *aMallocTable;
#define MALLOC_FUNCS (MALLOC_FUNCS_MALLOC_BASE | MALLOC_FUNCS_ARENA)
#define MALLOC_DECL(name, ...) aMallocTable->name = replace_##name;
#include "malloc_decls.h"
}

void profiler_replace_remove() {}

namespace mozilla::profiler {
//---------------------------------------------------------------------------
// Initialization
//---------------------------------------------------------------------------

BaseProfilerCount* install_memory_hooks() {
  if (!sCounter) {
    sCounter = new ProfilerCounterTotal("malloc", "Memory",
                                        "Amount of allocated memory");
    // Also initialize the ThreadIntercept, even if native allocation tracking
    // won't be turned on. This way the TLS will be initialized.
    ThreadIntercept::Init();
  } else {
    sCounter->Clear();
  }
  jemalloc_replace_dynamic(replace_init);
  return sCounter;
}

// Remove the hooks, but leave the sCounter machinery. Deleting the counter
// would race with any existing memory hooks that are currently running. Rather
// than adding overhead here of mutexes it's cheaper for the performance to just
// leak these values.
void remove_memory_hooks() { jemalloc_replace_dynamic(nullptr); }

void enable_native_allocations() {
  // The bloat log tracks allocations and deallocations. This can conflict
  // with the memory hook machinery, as the bloat log creates its own
  // allocations. This means we can re-enter inside the bloat log machinery. At
  // this time, the bloat log does not know about cannot handle the native
  // allocation feature.
  //
  // At the time of this writing, we hit this assertion:
  // IsIdle(oldState) || IsRead(oldState) in Checker::StartReadOp()
  //
  //    #01: GetBloatEntry(char const*, unsigned int)
  //    #02: NS_LogCtor
  //    #03: profiler_get_backtrace()
  //    #04: profiler_add_native_allocation_marker(long long)
  //    #05: mozilla::profiler::AllocCallback(void*, unsigned long)
  //    #06: replace_calloc(unsigned long, unsigned long)
  //    #07: PLDHashTable::ChangeTable(int)
  //    #08: PLDHashTable::Add(void const*, std::nothrow_t const&)
  //    #09: nsBaseHashtable<nsDepCharHashKey, nsAutoPtr<BloatEntry>, ...
  //    #10: GetBloatEntry(char const*, unsigned int)
  //    #11: NS_LogCtor
  //    #12: profiler_get_backtrace()
  //    ...
  MOZ_ASSERT(!PR_GetEnv("XPCOM_MEM_BLOAT_LOG"),
             "The bloat log feature is not compatible with the native "
             "allocations instrumentation.");

  EnsureBernoulliIsInstalled();
  EnsureAllocationTrackerIsInstalled();
  ThreadIntercept::EnableAllocationFeature();
}

// This is safe to call even if native allocations hasn't been enabled.
void disable_native_allocations() {
  ThreadIntercept::DisableAllocationFeature();
  if (gAllocationTracker) {
    gAllocationTracker->Reset();
  }
}

}  // namespace mozilla::profiler