Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

26 files changed, 11184 insertions, 0 deletions

diff --git a/memory/build/FdPrintf.cpp b/memory/build/FdPrintf.cpp
new file mode 100644
index 0000000000..272f3d0db8
--- /dev/null
+++ b/memory/build/FdPrintf.cpp
@@ -0,0 +1,200 @@
+/* -*- 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 <cstdarg>
+
+#ifdef _WIN32
+#  include <windows.h>
+#else
+#  include <unistd.h>
+#endif
+#include <cmath>
+#include <cstring>
+#include "mozilla/Assertions.h"
+#include "mozilla/Unused.h"
+#include "FdPrintf.h"
+
+/* Template class allowing a limited number of increments on a value */
+template <typename T>
+class CheckedIncrement {
+ public:
+  CheckedIncrement(T aValue, size_t aMaxIncrement)
+      : mValue(aValue), mMaxIncrement(aMaxIncrement) {}
+
+  T operator++(int) {
+    if (!mMaxIncrement) {
+      MOZ_CRASH("overflow detected");
+    }
+    mMaxIncrement--;
+    return mValue++;
+  }
+
+  T& operator++() {
+    (*this)++;
+    return mValue;
+  }
+
+  void advance(T end) {
+    // Only makes sense if T is a pointer type.
+    size_t diff = end - mValue;
+    if (diff > mMaxIncrement) {
+      MOZ_CRASH("overflow detected");
+    }
+    mMaxIncrement -= diff;
+    mValue = end;
+  }
+
+  void rewind(T pos) {
+    size_t diff = mValue - pos;
+    mMaxIncrement += diff;
+    mValue = pos;
+  }
+
+  operator T() { return mValue; }
+  T value() { return mValue; }
+
+ private:
+  T mValue;
+  size_t mMaxIncrement;
+};
+
+template <typename T>
+static unsigned NumDigits(T n) {
+  if (n < 1) {
+    // We want one digit, it will be 0.
+    return 1;
+  }
+
+  double l = log10(static_cast<double>(n));
+  double cl = ceil(l);
+  return l == cl ? unsigned(cl) + 1 : unsigned(cl);
+}
+
+static void LeftPad(CheckedIncrement<char*>& b, size_t pad) {
+  while (pad-- > 0) {
+    *(b++) = ' ';
+  }
+}
+
+// Write the digits into the buffer.
+static void WriteDigits(CheckedIncrement<char*>& b, size_t i,
+                        size_t num_digits) {
+  size_t x = pow(10, double(num_digits - 1));
+  do {
+    *(b++) = "0123456789"[(i / x) % 10];
+    x /= 10;
+  } while (x > 0);
+}
+
+void FdPrintf(intptr_t aFd, const char* aFormat, ...) {
+  if (aFd == 0) {
+    return;
+  }
+  char buf[256];
+  CheckedIncrement<char*> b(buf, sizeof(buf));
+  CheckedIncrement<const char*> f(aFormat, strlen(aFormat) + 1);
+  va_list ap;
+  va_start(ap, aFormat);
+  while (true) {
+    switch (*f) {
+      case '\0':
+        goto out;
+
+      case '%': {
+        // The start of the format specifier is used if this specifier is
+        // invalid.
+        const char* start = f;
+
+        // Read the field width
+        f++;
+        char* end = nullptr;
+        size_t width = strtoul(f, &end, 10);
+        // If strtol can't find a number that's okay, that means 0 in our
+        // case, but we must advance f).
+        f.advance(end);
+
+        switch (*f) {
+          case 'z': {
+            if (*(++f) == 'u') {
+              size_t i = va_arg(ap, size_t);
+
+              size_t num_digits = NumDigits(i);
+              LeftPad(b, width > num_digits ? width - num_digits : 0);
+              WriteDigits(b, i, num_digits);
+            } else {
+              // If the format specifier is unknown then write out '%' and
+              // rewind to the beginning of the specifier causing it to be
+              // printed normally.
+              *(b++) = '%';
+              f.rewind(start);
+            }
+            break;
+          }
+
+          case 'p': {
+            intptr_t ptr = va_arg(ap, intptr_t);
+            *(b++) = '0';
+            *(b++) = 'x';
+            int x = sizeof(intptr_t) * 8;
+            bool wrote_msb = false;
+            do {
+              x -= 4;
+              size_t hex_digit = ptr >> x & 0xf;
+              if (hex_digit || wrote_msb) {
+                *(b++) = "0123456789abcdef"[hex_digit];
+                wrote_msb = true;
+              }
+            } while (x > 0);
+            if (!wrote_msb) {
+              *(b++) = '0';
+            }
+            break;
+          }
+
+          case 's': {
+            const char* str = va_arg(ap, const char*);
+            size_t len = strlen(str);
+
+            LeftPad(b, width > len ? width - len : 0);
+
+            while (*str) {
+              *(b++) = *(str++);
+            }
+
+            break;
+          }
+
+          case '%':
+            // Print a single raw '%'.
+            *(b++) = '%';
+            break;
+
+          default:
+            // If the format specifier is unknown then write out '%' and
+            // rewind to the beginning of the specifier causing it to be
+            // printed normally.
+            *(b++) = '%';
+            f.rewind(start);
+            break;
+        }
+        break;
+      }
+      default:
+        *(b++) = *f;
+        break;
+    }
+    f++;
+  }
+out:
+#ifdef _WIN32
+  // See comment in FdPrintf.h as to why WriteFile is used.
+  DWORD written;
+  WriteFile(reinterpret_cast<HANDLE>(aFd), buf, b - buf, &written, nullptr);
+#else
+  MOZ_UNUSED(write(aFd, buf, b - buf));
+#endif
+  va_end(ap);
+}
diff --git a/memory/build/FdPrintf.h b/memory/build/FdPrintf.h
new file mode 100644
index 0000000000..257084243b
--- /dev/null
+++ b/memory/build/FdPrintf.h
@@ -0,0 +1,27 @@
+/* -*- 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/. */
+
+#ifndef __FdPrintf_h__
+#define __FdPrintf_h__
+
+/* We can't use libc's (f)printf because it would reenter in replace_malloc,
+ * So use a custom and simplified version.  Only %p, %zu, %s and %% are
+ * supported, %zu, %s, support width specifiers.
+ *
+ * /!\ This function used a fixed-size internal buffer. The caller is
+ * expected to not use a format string that may overflow.
+ * The aFd argument is a file descriptor on UNIX and a native win32 file
+ * handle on Windows (from CreateFile). We can't use the windows POSIX
+ * APIs is that they don't support O_APPEND in a multi-process-safe way,
+ * while CreateFile does.
+ */
+void FdPrintf(intptr_t aFd, const char* aFormat, ...)
+#ifdef __GNUC__
+    __attribute__((format(printf, 2, 3)))
+#endif
+    ;
+
+#endif /* __FdPrintf_h__ */
diff --git a/memory/build/Makefile.in b/memory/build/Makefile.in
new file mode 100644
index 0000000000..1ddd1121be
--- /dev/null
+++ b/memory/build/Makefile.in
@@ -0,0 +1,9 @@
+# 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/.
+
+# Workaround for alignment problems in gcov code. See
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1413570#c2.
+ifeq ($(TARGET_CPU),x86)
+PROFILE_GEN_CFLAGS += -mno-sse2
+endif
diff --git a/memory/build/Mutex.cpp b/memory/build/Mutex.cpp
new file mode 100644
index 0000000000..1450210293
--- /dev/null
+++ b/memory/build/Mutex.cpp
@@ -0,0 +1,26 @@
+/* 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 "Mutex.h"
+
+#include <errno.h>
+
+#include "mozilla/Assertions.h"
+
+bool Mutex::TryLock() {
+#if defined(XP_WIN)
+  return !!TryEnterCriticalSection(&mMutex);
+#elif defined(XP_DARWIN)
+  return os_unfair_lock_trylock(&mMutex);
+#else
+  switch (pthread_mutex_trylock(&mMutex)) {
+    case 0:
+      return true;
+    case EBUSY:
+      return false;
+    default:
+      MOZ_CRASH("pthread_mutex_trylock error.");
+  }
+#endif
+}
diff --git a/memory/build/Mutex.h b/memory/build/Mutex.h
new file mode 100644
index 0000000000..f360084f64
--- /dev/null
+++ b/memory/build/Mutex.h
@@ -0,0 +1,263 @@
+/* -*- 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/. */
+
+#ifndef Mutex_h
+#define Mutex_h
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#else
+#  include <pthread.h>
+#endif
+#if defined(XP_DARWIN)
+#  include <os/lock.h>
+#endif
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ThreadSafety.h"
+
+#if defined(XP_DARWIN)
+// For information about the following undocumented flags and functions see
+// https://github.com/apple/darwin-xnu/blob/main/bsd/sys/ulock.h and
+// https://github.com/apple/darwin-libplatform/blob/main/private/os/lock_private.h
+#  define OS_UNFAIR_LOCK_DATA_SYNCHRONIZATION (0x00010000)
+#  define OS_UNFAIR_LOCK_ADAPTIVE_SPIN (0x00040000)
+
+extern "C" {
+
+typedef uint32_t os_unfair_lock_options_t;
+OS_UNFAIR_LOCK_AVAILABILITY
+OS_EXPORT OS_NOTHROW OS_NONNULL_ALL void os_unfair_lock_lock_with_options(
+    os_unfair_lock_t lock, os_unfair_lock_options_t options);
+}
+#endif  // defined(XP_DARWIN)
+
+// Mutexes based on spinlocks.  We can't use normal pthread spinlocks in all
+// places, because they require malloc()ed memory, which causes bootstrapping
+// issues in some cases.  We also can't use constructors, because for statics,
+// they would fire after the first use of malloc, resetting the locks.
+struct MOZ_CAPABILITY("mutex") Mutex {
+#if defined(XP_WIN)
+  CRITICAL_SECTION mMutex;
+#elif defined(XP_DARWIN)
+  os_unfair_lock mMutex;
+#else
+  pthread_mutex_t mMutex;
+#endif
+
+  // Initializes a mutex. Returns whether initialization succeeded.
+  inline bool Init() {
+#if defined(XP_WIN)
+    if (!InitializeCriticalSectionAndSpinCount(&mMutex, 5000)) {
+      return false;
+    }
+#elif defined(XP_DARWIN)
+    mMutex = OS_UNFAIR_LOCK_INIT;
+#elif defined(XP_LINUX) && !defined(ANDROID)
+    pthread_mutexattr_t attr;
+    if (pthread_mutexattr_init(&attr) != 0) {
+      return false;
+    }
+    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
+    if (pthread_mutex_init(&mMutex, &attr) != 0) {
+      pthread_mutexattr_destroy(&attr);
+      return false;
+    }
+    pthread_mutexattr_destroy(&attr);
+#else
+    if (pthread_mutex_init(&mMutex, nullptr) != 0) {
+      return false;
+    }
+#endif
+    return true;
+  }
+
+  inline void Lock() MOZ_CAPABILITY_ACQUIRE() {
+#if defined(XP_WIN)
+    EnterCriticalSection(&mMutex);
+#elif defined(XP_DARWIN)
+    // We rely on a non-public function to improve performance here.
+    // The OS_UNFAIR_LOCK_DATA_SYNCHRONIZATION flag informs the kernel that
+    // the calling thread is able to make progress even in absence of actions
+    // from other threads and the OS_UNFAIR_LOCK_ADAPTIVE_SPIN one causes the
+    // kernel to spin on a contested lock if the owning thread is running on
+    // the same physical core (presumably only on x86 CPUs given that ARM
+    // macs don't have cores capable of SMT).
+    os_unfair_lock_lock_with_options(
+        &mMutex,
+        OS_UNFAIR_LOCK_DATA_SYNCHRONIZATION | OS_UNFAIR_LOCK_ADAPTIVE_SPIN);
+#else
+    pthread_mutex_lock(&mMutex);
+#endif
+  }
+
+  [[nodiscard]] bool TryLock() MOZ_TRY_ACQUIRE(true);
+
+  inline void Unlock() MOZ_CAPABILITY_RELEASE() {
+#if defined(XP_WIN)
+    LeaveCriticalSection(&mMutex);
+#elif defined(XP_DARWIN)
+    os_unfair_lock_unlock(&mMutex);
+#else
+    pthread_mutex_unlock(&mMutex);
+#endif
+  }
+
+#if defined(XP_DARWIN)
+  static bool SpinInKernelSpace();
+  static const bool gSpinInKernelSpace;
+#endif  // XP_DARWIN
+};
+
+// Mutex that can be used for static initialization.
+// On Windows, CRITICAL_SECTION requires a function call to be initialized,
+// but for the initialization lock, a static initializer calling the
+// function would be called too late. We need no-function-call
+// initialization, which SRWLock provides.
+// Ideally, we'd use the same type of locks everywhere, but SRWLocks
+// everywhere incur a performance penalty. See bug 1418389.
+#if defined(XP_WIN)
+struct MOZ_CAPABILITY("mutex") StaticMutex {
+  SRWLOCK mMutex;
+
+  inline void Lock() MOZ_CAPABILITY_ACQUIRE() {
+    AcquireSRWLockExclusive(&mMutex);
+  }
+
+  inline void Unlock() MOZ_CAPABILITY_RELEASE() {
+    ReleaseSRWLockExclusive(&mMutex);
+  }
+};
+
+// Normally, we'd use a constexpr constructor, but MSVC likes to create
+// static initializers anyways.
+#  define STATIC_MUTEX_INIT SRWLOCK_INIT
+
+#else
+typedef Mutex StaticMutex;
+
+#  if defined(XP_DARWIN)
+#    define STATIC_MUTEX_INIT OS_UNFAIR_LOCK_INIT
+#  elif defined(XP_LINUX) && !defined(ANDROID)
+#    define STATIC_MUTEX_INIT PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+#  else
+#    define STATIC_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
+#  endif
+
+#endif
+
+#ifdef XP_WIN
+typedef DWORD ThreadId;
+inline ThreadId GetThreadId() { return GetCurrentThreadId(); }
+#else
+typedef pthread_t ThreadId;
+inline ThreadId GetThreadId() { return pthread_self(); }
+#endif
+
+class MOZ_CAPABILITY("mutex") MaybeMutex : public Mutex {
+ public:
+  enum DoLock {
+    MUST_LOCK,
+    AVOID_LOCK_UNSAFE,
+  };
+
+  bool Init(DoLock aDoLock) {
+    mDoLock = aDoLock;
+#ifdef MOZ_DEBUG
+    mThreadId = GetThreadId();
+#endif
+    return Mutex::Init();
+  }
+
+#ifndef XP_WIN
+  // Re initialise after fork(), assumes that mDoLock is already initialised.
+  void Reinit(pthread_t aForkingThread) {
+    if (mDoLock == MUST_LOCK) {
+      Mutex::Init();
+      return;
+    }
+#  ifdef MOZ_DEBUG
+    // If this is an eluded lock we can only safely re-initialise it if the
+    // thread that called fork is the one that owns the lock.
+    if (pthread_equal(mThreadId, aForkingThread)) {
+      mThreadId = GetThreadId();
+      Mutex::Init();
+    } else {
+      // We can't guantee that whatever resource this lock protects (probably a
+      // jemalloc arena) is in a consistent state.
+      mDeniedAfterFork = true;
+    }
+#  endif
+  }
+#endif
+
+  inline void Lock() MOZ_CAPABILITY_ACQUIRE() {
+    if (ShouldLock()) {
+      Mutex::Lock();
+    }
+  }
+
+  inline void Unlock() MOZ_CAPABILITY_RELEASE() {
+    if (ShouldLock()) {
+      Mutex::Unlock();
+    }
+  }
+
+  // Return true if we can use this resource from this thread, either because
+  // we'll use the lock or because this is the only thread that will access the
+  // protected resource.
+#ifdef MOZ_DEBUG
+  bool SafeOnThisThread() const {
+    return mDoLock == MUST_LOCK || GetThreadId() == mThreadId;
+  }
+#endif
+
+  bool LockIsEnabled() const { return mDoLock == MUST_LOCK; }
+
+ private:
+  bool ShouldLock() {
+#ifndef XP_WIN
+    MOZ_ASSERT(!mDeniedAfterFork);
+#endif
+
+    if (mDoLock == MUST_LOCK) {
+      return true;
+    }
+
+    MOZ_ASSERT(GetThreadId() == mThreadId);
+    return false;
+  }
+
+  DoLock mDoLock;
+#ifdef MOZ_DEBUG
+  ThreadId mThreadId;
+#  ifndef XP_WIN
+  bool mDeniedAfterFork = false;
+#  endif
+#endif
+};
+
+template <typename T>
+struct MOZ_SCOPED_CAPABILITY MOZ_RAII AutoLock {
+  explicit AutoLock(T& aMutex) MOZ_CAPABILITY_ACQUIRE(aMutex) : mMutex(aMutex) {
+    mMutex.Lock();
+  }
+
+  ~AutoLock() MOZ_CAPABILITY_RELEASE() { mMutex.Unlock(); }
+
+  AutoLock(const AutoLock&) = delete;
+  AutoLock(AutoLock&&) = delete;
+
+ private:
+  T& mMutex;
+};
+
+using MutexAutoLock = AutoLock<Mutex>;
+
+using MaybeMutexAutoLock = AutoLock<MaybeMutex>;
+
+#endif
diff --git a/memory/build/PHC.cpp b/memory/build/PHC.cpp
new file mode 100644
index 0000000000..94cb5596a5
--- /dev/null
+++ b/memory/build/PHC.cpp
@@ -0,0 +1,1837 @@
+/* -*- 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/. */
+
+// PHC is a probabilistic heap checker. A tiny fraction of randomly chosen heap
+// allocations are subject to some expensive checking via the use of OS page
+// access protection. A failed check triggers a crash, whereupon useful
+// information about the failure is put into the crash report. The cost and
+// coverage for each user is minimal, but spread over the entire user base the
+// coverage becomes significant.
+//
+// The idea comes from Chromium, where it is called GWP-ASAN. (Firefox uses PHC
+// as the name because GWP-ASAN is long, awkward, and doesn't have any
+// particular meaning.)
+//
+// In the current implementation up to 64 allocations per process can become
+// PHC allocations. These allocations must be page-sized or smaller. Each PHC
+// allocation gets its own page, and when the allocation is freed its page is
+// marked inaccessible until the page is reused for another allocation. This
+// means that a use-after-free defect (which includes double-frees) will be
+// caught if the use occurs before the page is reused for another allocation.
+// The crash report will contain stack traces for the allocation site, the free
+// site, and the use-after-free site, which is often enough to diagnose the
+// defect.
+//
+// Also, each PHC allocation is followed by a guard page. The PHC allocation is
+// positioned so that its end abuts the guard page (or as close as possible,
+// given alignment constraints). This means that a bounds violation at the end
+// of the allocation (overflow) will be caught. The crash report will contain
+// stack traces for the allocation site and the bounds violation use site,
+// which is often enough to diagnose the defect.
+//
+// (A bounds violation at the start of the allocation (underflow) will not be
+// caught, unless it is sufficiently large to hit the preceding allocation's
+// guard page, which is not that likely. It would be possible to look more
+// assiduously for underflow by randomly placing some allocations at the end of
+// the page and some at the start of the page, and GWP-ASAN does this. PHC does
+// not, however, because overflow is likely to be much more common than
+// underflow in practice.)
+//
+// We use a simple heuristic to categorize a guard page access as overflow or
+// underflow: if the address falls in the lower half of the guard page, we
+// assume it is overflow, otherwise we assume it is underflow. More
+// sophisticated heuristics are possible, but this one is very simple, and it is
+// likely that most overflows/underflows in practice are very close to the page
+// boundary.
+//
+// The design space for the randomization strategy is large. The current
+// implementation has a large random delay before it starts operating, and a
+// small random delay between each PHC allocation attempt. Each freed PHC
+// allocation is quarantined for a medium random delay before being reused, in
+// order to increase the chance of catching UAFs.
+//
+// The basic cost of PHC's operation is as follows.
+//
+// - The physical memory cost is 64 pages plus some metadata (including stack
+//   traces) for each page. This amounts to 256 KiB per process on
+//   architectures with 4 KiB pages and 1024 KiB on macOS/AArch64 which uses
+//   16 KiB pages.
+//
+// - The virtual memory cost is the physical memory cost plus the guard pages:
+//   another 64 pages. This amounts to another 256 KiB per process on
+//   architectures with 4 KiB pages and 1024 KiB on macOS/AArch64 which uses
+//   16 KiB pages. PHC is currently only enabled on 64-bit platforms so the
+//   impact of the virtual memory usage is negligible.
+//
+// - Every allocation requires a size check and a decrement-and-check of an
+//   atomic counter. When the counter reaches zero a PHC allocation can occur,
+//   which involves marking a page as accessible and getting a stack trace for
+//   the allocation site. Otherwise, mozjemalloc performs the allocation.
+//
+// - Every deallocation requires a range check on the pointer to see if it
+//   involves a PHC allocation. (The choice to only do PHC allocations that are
+//   a page or smaller enables this range check, because the 64 pages are
+//   contiguous. Allowing larger allocations would make this more complicated,
+//   and we definitely don't want something as slow as a hash table lookup on
+//   every deallocation.) PHC deallocations involve marking a page as
+//   inaccessible and getting a stack trace for the deallocation site.
+//
+// Note that calls to realloc(), free(), and malloc_usable_size() will
+// immediately crash if the given pointer falls within a page allocation's
+// page, but does not point to the start of the allocation itself.
+//
+//   void* p = malloc(64);
+//   free(p + 1);     // p+1 doesn't point to the allocation start; crash
+//
+// Such crashes will not have the PHC fields in the crash report.
+//
+// PHC-specific tests can be run with the following commands:
+// - gtests: `./mach gtest '*PHC*'`
+// - xpcshell-tests: `./mach test toolkit/crashreporter/test/unit`
+//   - This runs some non-PHC tests as well.
+
+#include "PHC.h"
+
+#include <stdlib.h>
+#include <time.h>
+
+#include <algorithm>
+
+#ifdef XP_WIN
+#  include <process.h>
+#else
+#  include <sys/mman.h>
+#  include <sys/types.h>
+#  include <pthread.h>
+#  include <unistd.h>
+#endif
+
+#include "mozjemalloc.h"
+
+#include "mozjemalloc.h"
+#include "FdPrintf.h"
+#include "Mutex.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/StackWalk.h"
+#include "mozilla/ThreadLocal.h"
+#include "mozilla/XorShift128PlusRNG.h"
+
+using namespace mozilla;
+
+//---------------------------------------------------------------------------
+// Utilities
+//---------------------------------------------------------------------------
+
+#ifdef ANDROID
+// Android doesn't have pthread_atfork defined in pthread.h.
+extern "C" MOZ_EXPORT int pthread_atfork(void (*)(void), void (*)(void),
+                                         void (*)(void));
+#endif
+
+#ifndef DISALLOW_COPY_AND_ASSIGN
+#  define DISALLOW_COPY_AND_ASSIGN(T) \
+    T(const T&);                      \
+    void operator=(const T&)
+#endif
+
+// This class provides infallible operations for the small number of heap
+// allocations that PHC does for itself. It would be nice if we could use the
+// InfallibleAllocPolicy from mozalloc, but PHC cannot use mozalloc.
+class InfallibleAllocPolicy {
+ public:
+  static void AbortOnFailure(const void* aP) {
+    if (!aP) {
+      MOZ_CRASH("PHC failed to allocate");
+    }
+  }
+
+  template <class T>
+  static T* new_() {
+    void* p = MozJemalloc::malloc(sizeof(T));
+    AbortOnFailure(p);
+    return new (p) T;
+  }
+};
+
+//---------------------------------------------------------------------------
+// Stack traces
+//---------------------------------------------------------------------------
+
+// This code is similar to the equivalent code within DMD.
+
+class StackTrace : public phc::StackTrace {
+ public:
+  StackTrace() = default;
+
+  void Clear() { mLength = 0; }
+
+  void Fill();
+
+ private:
+  static void StackWalkCallback(uint32_t aFrameNumber, void* aPc, void* aSp,
+                                void* aClosure) {
+    StackTrace* st = (StackTrace*)aClosure;
+    MOZ_ASSERT(st->mLength < kMaxFrames);
+    st->mPcs[st->mLength] = aPc;
+    st->mLength++;
+    MOZ_ASSERT(st->mLength == aFrameNumber);
+  }
+};
+
+// WARNING WARNING WARNING: this function must only be called when GMut::sMutex
+// is *not* locked, otherwise we might get deadlocks.
+//
+// How? On Windows, MozStackWalk() can lock a mutex, M, from the shared library
+// loader. Another thread might call malloc() while holding M locked (when
+// loading a shared library) and try to lock GMut::sMutex, causing a deadlock.
+// So GMut::sMutex can't be locked during the call to MozStackWalk(). (For
+// details, see https://bugzilla.mozilla.org/show_bug.cgi?id=374829#c8. On
+// Linux, something similar can happen; see bug 824340. So we just disallow it
+// on all platforms.)
+//
+// In DMD, to avoid this problem we temporarily unlock the equivalent mutex for
+// the MozStackWalk() call. But that's grotty, and things are a bit different
+// here, so we just require that stack traces be obtained before locking
+// GMut::sMutex.
+//
+// Unfortunately, there is no reliable way at compile-time or run-time to ensure
+// this pre-condition. Hence this large comment.
+//
+void StackTrace::Fill() {
+  mLength = 0;
+
+// These ifdefs should be kept in sync with the conditions in
+// phc_implies_frame_pointers in build/moz.configure/memory.configure
+#if defined(XP_WIN) && defined(_M_IX86)
+  // This avoids MozStackWalk(), which causes unusably slow startup on Win32
+  // when it is called during static initialization (see bug 1241684).
+  //
+  // This code is cribbed from the Gecko Profiler, which also uses
+  // FramePointerStackWalk() on Win32: Registers::SyncPopulate() for the
+  // frame pointer, and GetStackTop() for the stack end.
+  CONTEXT context;
+  RtlCaptureContext(&context);
+  void** fp = reinterpret_cast<void**>(context.Ebp);
+
+  PNT_TIB pTib = reinterpret_cast<PNT_TIB>(NtCurrentTeb());
+  void* stackEnd = static_cast<void*>(pTib->StackBase);
+  FramePointerStackWalk(StackWalkCallback, kMaxFrames, this, fp, stackEnd);
+#elif defined(XP_DARWIN)
+  // This avoids MozStackWalk(), which has become unusably slow on Mac due to
+  // changes in libunwind.
+  //
+  // This code is cribbed from the Gecko Profiler, which also uses
+  // FramePointerStackWalk() on Mac: Registers::SyncPopulate() for the frame
+  // pointer, and GetStackTop() for the stack end.
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wframe-address"
+  void** fp = reinterpret_cast<void**>(__builtin_frame_address(1));
+#  pragma GCC diagnostic pop
+  void* stackEnd = pthread_get_stackaddr_np(pthread_self());
+  FramePointerStackWalk(StackWalkCallback, kMaxFrames, this, fp, stackEnd);
+#else
+  MozStackWalk(StackWalkCallback, nullptr, kMaxFrames, this);
+#endif
+}
+
+//---------------------------------------------------------------------------
+// Logging
+//---------------------------------------------------------------------------
+
+// Change this to 1 to enable some PHC logging. Useful for debugging.
+#define PHC_LOGGING 0
+
+#if PHC_LOGGING
+
+static size_t GetPid() { return size_t(getpid()); }
+
+static size_t GetTid() {
+#  if defined(XP_WIN)
+  return size_t(GetCurrentThreadId());
+#  else
+  return size_t(pthread_self());
+#  endif
+}
+
+#  if defined(XP_WIN)
+#    define LOG_STDERR \
+      reinterpret_cast<intptr_t>(GetStdHandle(STD_ERROR_HANDLE))
+#  else
+#    define LOG_STDERR 2
+#  endif
+#  define LOG(fmt, ...)                                                \
+    FdPrintf(LOG_STDERR, "PHC[%zu,%zu,~%zu] " fmt, GetPid(), GetTid(), \
+             size_t(GAtomic::Now()), ##__VA_ARGS__)
+
+#else
+
+#  define LOG(fmt, ...)
+
+#endif  // PHC_LOGGING
+
+//---------------------------------------------------------------------------
+// Global state
+//---------------------------------------------------------------------------
+
+// Throughout this entire file time is measured as the number of sub-page
+// allocations performed (by PHC and mozjemalloc combined). `Time` is 64-bit
+// because we could have more than 2**32 allocations in a long-running session.
+// `Delay` is 32-bit because the delays used within PHC are always much smaller
+// than 2**32.
+using Time = uint64_t;   // A moment in time.
+using Delay = uint32_t;  // A time duration.
+
+// PHC only runs if the page size is 4 KiB; anything more is uncommon and would
+// use too much memory. So we hardwire this size for all platforms but macOS
+// on ARM processors. For the latter we make an exception because the minimum
+// page size supported is 16KiB so there's no way to go below that.
+static const size_t kPageSize =
+#if defined(XP_DARWIN) && defined(__aarch64__)
+    16384
+#else
+    4096
+#endif
+    ;
+
+// We align the PHC area to a multiple of the jemalloc and JS GC chunk size
+// (both use 1MB aligned chunks) so that their address computations don't lead
+// from non-PHC memory into PHC memory causing misleading PHC stacks to be
+// attached to a crash report.
+static const size_t kPhcAlign = 1024 * 1024;
+
+static_assert(IsPowerOfTwo(kPhcAlign));
+static_assert((kPhcAlign % kPageSize) == 0);
+
+// There are two kinds of page.
+// - Allocation pages, from which allocations are made.
+// - Guard pages, which are never touched by PHC.
+//
+// These page kinds are interleaved; each allocation page has a guard page on
+// either side.
+#ifdef EARLY_BETA_OR_EARLIER
+static const size_t kNumAllocPages = kPageSize == 4096 ? 4096 : 1024;
+#else
+// This will use between 82KiB and 1.1MiB per process (depending on how many
+// objects are currently allocated).  We will tune this in the future.
+static const size_t kNumAllocPages = kPageSize == 4096 ? 256 : 64;
+#endif
+static const size_t kNumAllPages = kNumAllocPages * 2 + 1;
+
+// The total size of the allocation pages and guard pages.
+static const size_t kAllPagesSize = kNumAllPages * kPageSize;
+
+// jemalloc adds a guard page to the end of our allocation, see the comment in
+// AllocAllPages() for more information.
+static const size_t kAllPagesJemallocSize = kAllPagesSize - kPageSize;
+
+// The default state for PHC.  Either Enabled or OnlyFree.
+#define DEFAULT_STATE mozilla::phc::OnlyFree
+
+// The maximum time.
+static const Time kMaxTime = ~(Time(0));
+
+// Truncate aRnd to the range (1 .. aAvgDelay*2). If aRnd is random, this
+// results in an average value of aAvgDelay + 0.5, which is close enough to
+// aAvgDelay. aAvgDelay must be a power-of-two for speed.
+constexpr Delay Rnd64ToDelay(Delay aAvgDelay, uint64_t aRnd) {
+  MOZ_ASSERT(IsPowerOfTwo(aAvgDelay), "must be a power of two");
+
+  return (aRnd & (uint64_t(aAvgDelay) * 2 - 1)) + 1;
+}
+
+static Delay CheckProbability(int64_t aProb) {
+  // Limit delays calculated from prefs to 0x80000000, this is the largest
+  // power-of-two that fits in a Delay since it is a uint32_t.
+  // The minimum is 2 that way not every allocation goes straight to PHC.
+  return RoundUpPow2(
+      std::min(std::max(aProb, int64_t(2)), int64_t(0x80000000)));
+}
+
+// Maps a pointer to a PHC-specific structure:
+// - Nothing
+// - A guard page (it is unspecified which one)
+// - An allocation page (with an index < kNumAllocPages)
+//
+// The standard way of handling a PtrKind is to check IsNothing(), and if that
+// fails, to check IsGuardPage(), and if that fails, to call AllocPage().
+class PtrKind {
+ private:
+  enum class Tag : uint8_t {
+    Nothing,
+    GuardPage,
+    AllocPage,
+  };
+
+  Tag mTag;
+  uintptr_t mIndex;  // Only used if mTag == Tag::AllocPage.
+
+ public:
+  // Detect what a pointer points to. This constructor must be fast because it
+  // is called for every call to free(), realloc(), malloc_usable_size(), and
+  // jemalloc_ptr_info().
+  PtrKind(const void* aPtr, const uint8_t* aPagesStart,
+          const uint8_t* aPagesLimit) {
+    if (!(aPagesStart <= aPtr && aPtr < aPagesLimit)) {
+      mTag = Tag::Nothing;
+    } else {
+      uintptr_t offset = static_cast<const uint8_t*>(aPtr) - aPagesStart;
+      uintptr_t allPageIndex = offset / kPageSize;
+      MOZ_ASSERT(allPageIndex < kNumAllPages);
+      if (allPageIndex & 1) {
+        // Odd-indexed pages are allocation pages.
+        uintptr_t allocPageIndex = allPageIndex / 2;
+        MOZ_ASSERT(allocPageIndex < kNumAllocPages);
+        mTag = Tag::AllocPage;
+        mIndex = allocPageIndex;
+      } else {
+        // Even-numbered pages are guard pages.
+        mTag = Tag::GuardPage;
+      }
+    }
+  }
+
+  bool IsNothing() const { return mTag == Tag::Nothing; }
+  bool IsGuardPage() const { return mTag == Tag::GuardPage; }
+
+  // This should only be called after IsNothing() and IsGuardPage() have been
+  // checked and failed.
+  uintptr_t AllocPageIndex() const {
+    MOZ_RELEASE_ASSERT(mTag == Tag::AllocPage);
+    return mIndex;
+  }
+};
+
+// Shared, atomic, mutable global state.
+class GAtomic {
+ public:
+  static void Init(Delay aFirstDelay) {
+    sAllocDelay = aFirstDelay;
+
+    LOG("Initial sAllocDelay <- %zu\n", size_t(aFirstDelay));
+  }
+
+  static Time Now() { return sNow; }
+
+  static void IncrementNow() { sNow++; }
+
+  // Decrements the delay and returns the decremented value.
+  static int32_t DecrementDelay() { return --sAllocDelay; }
+
+  static void SetAllocDelay(Delay aAllocDelay) { sAllocDelay = aAllocDelay; }
+
+  static bool AllocDelayHasWrapped(Delay aAvgAllocDelay,
+                                   Delay aAvgFirstAllocDelay) {
+    // Delay is unsigned so we can't test for less that zero.  Instead test if
+    // it has wrapped around by comparing with the maximum value we ever use.
+    return sAllocDelay > 2 * std::max(aAvgAllocDelay, aAvgFirstAllocDelay);
+  }
+
+ private:
+  // The current time. Relaxed semantics because it's primarily used for
+  // determining if an allocation can be recycled yet and therefore it doesn't
+  // need to be exact.
+  static Atomic<Time, Relaxed> sNow;
+
+  // Delay until the next attempt at a page allocation. See the comment in
+  // MaybePageAlloc() for an explanation of why it uses ReleaseAcquire
+  // semantics.
+  static Atomic<Delay, ReleaseAcquire> sAllocDelay;
+};
+
+Atomic<Time, Relaxed> GAtomic::sNow;
+Atomic<Delay, ReleaseAcquire> GAtomic::sAllocDelay;
+
+// Shared, immutable global state. Initialized by replace_init() and never
+// changed after that. replace_init() runs early enough that no synchronization
+// is needed.
+class GConst {
+ private:
+  // The bounds of the allocated pages.
+  uint8_t* const mPagesStart;
+  uint8_t* const mPagesLimit;
+
+  // Allocates the allocation pages and the guard pages, contiguously.
+  uint8_t* AllocAllPages() {
+    // The memory allocated here is never freed, because it would happen at
+    // process termination when it would be of little use.
+
+    // We can rely on jemalloc's behaviour that when it allocates memory aligned
+    // with its own chunk size it will over-allocate and guarantee that the
+    // memory after the end of our allocation, but before the next chunk, is
+    // decommitted and inaccessible. Elsewhere in PHC we assume that we own
+    // that page (so that memory errors in it get caught by PHC) but here we
+    // use kAllPagesJemallocSize which subtracts jemalloc's guard page.
+    void* pages = MozJemalloc::memalign(kPhcAlign, kAllPagesJemallocSize);
+    if (!pages) {
+      MOZ_CRASH();
+    }
+
+    // Make the pages inaccessible.
+#ifdef XP_WIN
+    if (!VirtualFree(pages, kAllPagesJemallocSize, MEM_DECOMMIT)) {
+      MOZ_CRASH("VirtualFree failed");
+    }
+#else
+    if (mmap(pages, kAllPagesJemallocSize, PROT_NONE,
+             MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) == MAP_FAILED) {
+      MOZ_CRASH("mmap failed");
+    }
+#endif
+
+    return static_cast<uint8_t*>(pages);
+  }
+
+ public:
+  GConst()
+      : mPagesStart(AllocAllPages()), mPagesLimit(mPagesStart + kAllPagesSize) {
+    LOG("AllocAllPages at %p..%p\n", mPagesStart, mPagesLimit);
+  }
+
+  class PtrKind PtrKind(const void* aPtr) {
+    class PtrKind pk(aPtr, mPagesStart, mPagesLimit);
+    return pk;
+  }
+
+  bool IsInFirstGuardPage(const void* aPtr) {
+    return mPagesStart <= aPtr && aPtr < mPagesStart + kPageSize;
+  }
+
+  // Get the address of the allocation page referred to via an index. Used when
+  // marking the page as accessible/inaccessible.
+  uint8_t* AllocPagePtr(uintptr_t aIndex) {
+    MOZ_ASSERT(aIndex < kNumAllocPages);
+    // Multiply by two and add one to account for allocation pages *and* guard
+    // pages.
+    return mPagesStart + (2 * aIndex + 1) * kPageSize;
+  }
+};
+
+static GConst* gConst;
+
+// This type is used as a proof-of-lock token, to make it clear which functions
+// require sMutex to be locked.
+using GMutLock = const MutexAutoLock&;
+
+// Shared, mutable global state. Protected by sMutex; all accessing functions
+// take a GMutLock as proof that sMutex is held.
+class GMut {
+  enum class AllocPageState {
+    NeverAllocated = 0,
+    InUse = 1,
+    Freed = 2,
+  };
+
+  // Metadata for each allocation page.
+  class AllocPageInfo {
+   public:
+    AllocPageInfo()
+        : mState(AllocPageState::NeverAllocated),
+          mBaseAddr(nullptr),
+          mReuseTime(0) {}
+
+    // The current allocation page state.
+    AllocPageState mState;
+
+    // The arena that the allocation is nominally from. This isn't meaningful
+    // within PHC, which has no arenas. But it is necessary for reallocation of
+    // page allocations as normal allocations, such as in this code:
+    //
+    //   p = moz_arena_malloc(arenaId, 4096);
+    //   realloc(p, 8192);
+    //
+    // The realloc is more than one page, and thus too large for PHC to handle.
+    // Therefore, if PHC handles the first allocation, it must ask mozjemalloc
+    // to allocate the 8192 bytes in the correct arena, and to do that, it must
+    // call MozJemalloc::moz_arena_malloc with the correct arenaId under the
+    // covers. Therefore it must record that arenaId.
+    //
+    // This field is also needed for jemalloc_ptr_info() to work, because it
+    // also returns the arena ID (but only in debug builds).
+    //
+    // - NeverAllocated: must be 0.
+    // - InUse | Freed: can be any valid arena ID value.
+    Maybe<arena_id_t> mArenaId;
+
+    // The starting address of the allocation. Will not be the same as the page
+    // address unless the allocation is a full page.
+    // - NeverAllocated: must be 0.
+    // - InUse | Freed: must be within the allocation page.
+    uint8_t* mBaseAddr;
+
+    // Usable size is computed as the number of bytes between the pointer and
+    // the end of the allocation page. This might be bigger than the requested
+    // size, especially if an outsized alignment is requested.
+    size_t UsableSize() const {
+      return mState == AllocPageState::NeverAllocated
+                 ? 0
+                 : kPageSize - (reinterpret_cast<uintptr_t>(mBaseAddr) &
+                                (kPageSize - 1));
+    }
+
+    // The internal fragmentation for this allocation.
+    size_t FragmentationBytes() const {
+      MOZ_ASSERT(kPageSize >= UsableSize());
+      return mState == AllocPageState::InUse ? kPageSize - UsableSize() : 0;
+    }
+
+    // The allocation stack.
+    // - NeverAllocated: Nothing.
+    // - InUse | Freed: Some.
+    Maybe<StackTrace> mAllocStack;
+
+    // The free stack.
+    // - NeverAllocated | InUse: Nothing.
+    // - Freed: Some.
+    Maybe<StackTrace> mFreeStack;
+
+    // The time at which the page is available for reuse, as measured against
+    // GAtomic::sNow. When the page is in use this value will be kMaxTime.
+    // - NeverAllocated: must be 0.
+    // - InUse: must be kMaxTime.
+    // - Freed: must be > 0 and < kMaxTime.
+    Time mReuseTime;
+  };
+
+ public:
+  // The mutex that protects the other members.
+  static Mutex sMutex MOZ_UNANNOTATED;
+
+  GMut() : mRNG(RandomSeed<0>(), RandomSeed<1>()) { sMutex.Init(); }
+
+  uint64_t Random64(GMutLock) { return mRNG.next(); }
+
+  bool IsPageInUse(GMutLock, uintptr_t aIndex) {
+    return mAllocPages[aIndex].mState == AllocPageState::InUse;
+  }
+
+  // Is the page free? And if so, has enough time passed that we can use it?
+  bool IsPageAllocatable(GMutLock, uintptr_t aIndex, Time aNow) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+    return page.mState != AllocPageState::InUse && aNow >= page.mReuseTime;
+  }
+
+  // Get the address of the allocation page referred to via an index. Used
+  // when checking pointers against page boundaries.
+  uint8_t* AllocPageBaseAddr(GMutLock, uintptr_t aIndex) {
+    return mAllocPages[aIndex].mBaseAddr;
+  }
+
+  Maybe<arena_id_t> PageArena(GMutLock aLock, uintptr_t aIndex) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+    AssertAllocPageInUse(aLock, page);
+
+    return page.mArenaId;
+  }
+
+  size_t PageUsableSize(GMutLock aLock, uintptr_t aIndex) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+    AssertAllocPageInUse(aLock, page);
+
+    return page.UsableSize();
+  }
+
+  // The total fragmentation in PHC
+  size_t FragmentationBytes() const {
+    size_t sum = 0;
+    for (const auto& page : mAllocPages) {
+      sum += page.FragmentationBytes();
+    }
+    return sum;
+  }
+
+  void SetPageInUse(GMutLock aLock, uintptr_t aIndex,
+                    const Maybe<arena_id_t>& aArenaId, uint8_t* aBaseAddr,
+                    const StackTrace& aAllocStack) {
+    AllocPageInfo& page = mAllocPages[aIndex];
+    AssertAllocPageNotInUse(aLock, page);
+
+    page.mState = AllocPageState::InUse;
+    page.mArenaId = aArenaId;
+    page.mBaseAddr = aBaseAddr;
+    page.mAllocStack = Some(aAllocStack);
+    page.mFreeStack = Nothing();
+    page.mReuseTime = kMaxTime;
+  }
+
+#if PHC_LOGGING
+  Time GetFreeTime(uintptr_t aIndex) const { return mFreeTime[aIndex]; }
+#endif
+
+  void ResizePageInUse(GMutLock aLock, uintptr_t aIndex,
+                       const Maybe<arena_id_t>& aArenaId, uint8_t* aNewBaseAddr,
+                       const StackTrace& aAllocStack) {
+    AllocPageInfo& page = mAllocPages[aIndex];
+    AssertAllocPageInUse(aLock, page);
+
+    // page.mState is not changed.
+    if (aArenaId.isSome()) {
+      // Crash if the arenas don't match.
+      MOZ_RELEASE_ASSERT(page.mArenaId == aArenaId);
+    }
+    page.mBaseAddr = aNewBaseAddr;
+    // We could just keep the original alloc stack, but the realloc stack is
+    // more recent and therefore seems more useful.
+    page.mAllocStack = Some(aAllocStack);
+    // page.mFreeStack is not changed.
+    // page.mReuseTime is not changed.
+  };
+
+  void SetPageFreed(GMutLock aLock, uintptr_t aIndex,
+                    const Maybe<arena_id_t>& aArenaId,
+                    const StackTrace& aFreeStack, Delay aReuseDelay) {
+    AllocPageInfo& page = mAllocPages[aIndex];
+    AssertAllocPageInUse(aLock, page);
+
+    page.mState = AllocPageState::Freed;
+
+    // page.mArenaId is left unchanged, for jemalloc_ptr_info() calls that
+    // occur after freeing (e.g. in the PtrInfo test in TestJemalloc.cpp).
+    if (aArenaId.isSome()) {
+      // Crash if the arenas don't match.
+      MOZ_RELEASE_ASSERT(page.mArenaId == aArenaId);
+    }
+
+    // page.musableSize is left unchanged, for reporting on UAF, and for
+    // jemalloc_ptr_info() calls that occur after freeing (e.g. in the PtrInfo
+    // test in TestJemalloc.cpp).
+
+    // page.mAllocStack is left unchanged, for reporting on UAF.
+
+    page.mFreeStack = Some(aFreeStack);
+    Time now = GAtomic::Now();
+#if PHC_LOGGING
+    mFreeTime[aIndex] = now;
+#endif
+    page.mReuseTime = now + aReuseDelay;
+  }
+
+  static void CrashOnGuardPage(void* aPtr) {
+    // An operation on a guard page? This is a bounds violation. Deliberately
+    // touch the page in question to cause a crash that triggers the usual PHC
+    // machinery.
+    LOG("CrashOnGuardPage(%p), bounds violation\n", aPtr);
+    *static_cast<uint8_t*>(aPtr) = 0;
+    MOZ_CRASH("unreachable");
+  }
+
+  void EnsureValidAndInUse(GMutLock, void* aPtr, uintptr_t aIndex)
+      MOZ_REQUIRES(sMutex) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+
+    // The pointer must point to the start of the allocation.
+    MOZ_RELEASE_ASSERT(page.mBaseAddr == aPtr);
+
+    if (page.mState == AllocPageState::Freed) {
+      LOG("EnsureValidAndInUse(%p), use-after-free\n", aPtr);
+      // An operation on a freed page? This is a particular kind of
+      // use-after-free. Deliberately touch the page in question, in order to
+      // cause a crash that triggers the usual PHC machinery. But unlock sMutex
+      // first, because that self-same PHC machinery needs to re-lock it, and
+      // the crash causes non-local control flow so sMutex won't be unlocked
+      // the normal way in the caller.
+      sMutex.Unlock();
+      *static_cast<uint8_t*>(aPtr) = 0;
+      MOZ_CRASH("unreachable");
+    }
+  }
+
+  // This expects GMUt::sMutex to be locked but can't check it with a parameter
+  // since we try-lock it.
+  void FillAddrInfo(uintptr_t aIndex, const void* aBaseAddr, bool isGuardPage,
+                    phc::AddrInfo& aOut) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+    if (isGuardPage) {
+      aOut.mKind = phc::AddrInfo::Kind::GuardPage;
+    } else {
+      switch (page.mState) {
+        case AllocPageState::NeverAllocated:
+          aOut.mKind = phc::AddrInfo::Kind::NeverAllocatedPage;
+          break;
+
+        case AllocPageState::InUse:
+          aOut.mKind = phc::AddrInfo::Kind::InUsePage;
+          break;
+
+        case AllocPageState::Freed:
+          aOut.mKind = phc::AddrInfo::Kind::FreedPage;
+          break;
+
+        default:
+          MOZ_CRASH();
+      }
+    }
+    aOut.mBaseAddr = page.mBaseAddr;
+    aOut.mUsableSize = page.UsableSize();
+    aOut.mAllocStack = page.mAllocStack;
+    aOut.mFreeStack = page.mFreeStack;
+  }
+
+  void FillJemallocPtrInfo(GMutLock, const void* aPtr, uintptr_t aIndex,
+                           jemalloc_ptr_info_t* aInfo) {
+    const AllocPageInfo& page = mAllocPages[aIndex];
+    switch (page.mState) {
+      case AllocPageState::NeverAllocated:
+        break;
+
+      case AllocPageState::InUse: {
+        // Only return TagLiveAlloc if the pointer is within the bounds of the
+        // allocation's usable size.
+        uint8_t* base = page.mBaseAddr;
+        uint8_t* limit = base + page.UsableSize();
+        if (base <= aPtr && aPtr < limit) {
+          *aInfo = {TagLiveAlloc, page.mBaseAddr, page.UsableSize(),
+                    page.mArenaId.valueOr(0)};
+          return;
+        }
+        break;
+      }
+
+      case AllocPageState::Freed: {
+        // Only return TagFreedAlloc if the pointer is within the bounds of the
+        // former allocation's usable size.
+        uint8_t* base = page.mBaseAddr;
+        uint8_t* limit = base + page.UsableSize();
+        if (base <= aPtr && aPtr < limit) {
+          *aInfo = {TagFreedAlloc, page.mBaseAddr, page.UsableSize(),
+                    page.mArenaId.valueOr(0)};
+          return;
+        }
+        break;
+      }
+
+      default:
+        MOZ_CRASH();
+    }
+
+    // Pointers into guard pages will end up here, as will pointers into
+    // allocation pages that aren't within the allocation's bounds.
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+  }
+
+#ifndef XP_WIN
+  static void prefork() MOZ_NO_THREAD_SAFETY_ANALYSIS { sMutex.Lock(); }
+  static void postfork_parent() MOZ_NO_THREAD_SAFETY_ANALYSIS {
+    sMutex.Unlock();
+  }
+  static void postfork_child() { sMutex.Init(); }
+#endif
+
+#if PHC_LOGGING
+  void IncPageAllocHits(GMutLock) { mPageAllocHits++; }
+  void IncPageAllocMisses(GMutLock) { mPageAllocMisses++; }
+#else
+  void IncPageAllocHits(GMutLock) {}
+  void IncPageAllocMisses(GMutLock) {}
+#endif
+
+  phc::PHCStats GetPageStats(GMutLock) {
+    phc::PHCStats stats;
+
+    for (const auto& page : mAllocPages) {
+      stats.mSlotsAllocated += page.mState == AllocPageState::InUse ? 1 : 0;
+      stats.mSlotsFreed += page.mState == AllocPageState::Freed ? 1 : 0;
+    }
+    stats.mSlotsUnused =
+        kNumAllocPages - stats.mSlotsAllocated - stats.mSlotsFreed;
+
+    return stats;
+  }
+
+#if PHC_LOGGING
+  size_t PageAllocHits(GMutLock) { return mPageAllocHits; }
+  size_t PageAllocAttempts(GMutLock) {
+    return mPageAllocHits + mPageAllocMisses;
+  }
+
+  // This is an integer because FdPrintf only supports integer printing.
+  size_t PageAllocHitRate(GMutLock) {
+    return mPageAllocHits * 100 / (mPageAllocHits + mPageAllocMisses);
+  }
+#endif
+
+  // Should we make new PHC allocations?
+  bool ShouldMakeNewAllocations() const {
+    return mPhcState == mozilla::phc::Enabled;
+  }
+
+  using PHCState = mozilla::phc::PHCState;
+  void SetState(PHCState aState) {
+    if (mPhcState != PHCState::Enabled && aState == PHCState::Enabled) {
+      MutexAutoLock lock(GMut::sMutex);
+      GAtomic::Init(Rnd64ToDelay(mAvgFirstAllocDelay, Random64(lock)));
+    }
+
+    mPhcState = aState;
+  }
+
+  void SetProbabilities(int64_t aAvgDelayFirst, int64_t aAvgDelayNormal,
+                        int64_t aAvgDelayPageReuse) {
+    MutexAutoLock lock(GMut::sMutex);
+
+    mAvgFirstAllocDelay = CheckProbability(aAvgDelayFirst);
+    mAvgAllocDelay = CheckProbability(aAvgDelayNormal);
+    mAvgPageReuseDelay = CheckProbability(aAvgDelayPageReuse);
+  }
+
+ private:
+  template <int N>
+  uint64_t RandomSeed() {
+    // An older version of this code used RandomUint64() here, but on Mac that
+    // function uses arc4random(), which can allocate, which would cause
+    // re-entry, which would be bad. So we just use time() and a local variable
+    // address. These are mediocre sources of entropy, but good enough for PHC.
+    static_assert(N == 0 || N == 1, "must be 0 or 1");
+    uint64_t seed;
+    if (N == 0) {
+      time_t t = time(nullptr);
+      seed = t ^ (t << 32);
+    } else {
+      seed = uintptr_t(&seed) ^ (uintptr_t(&seed) << 32);
+    }
+    return seed;
+  }
+
+  void AssertAllocPageInUse(GMutLock, const AllocPageInfo& aPage) {
+    MOZ_ASSERT(aPage.mState == AllocPageState::InUse);
+    // There is nothing to assert about aPage.mArenaId.
+    MOZ_ASSERT(aPage.mBaseAddr);
+    MOZ_ASSERT(aPage.UsableSize() > 0);
+    MOZ_ASSERT(aPage.mAllocStack.isSome());
+    MOZ_ASSERT(aPage.mFreeStack.isNothing());
+    MOZ_ASSERT(aPage.mReuseTime == kMaxTime);
+  }
+
+  void AssertAllocPageNotInUse(GMutLock, const AllocPageInfo& aPage) {
+    // We can assert a lot about `NeverAllocated` pages, but not much about
+    // `Freed` pages.
+#ifdef DEBUG
+    bool isFresh = aPage.mState == AllocPageState::NeverAllocated;
+    MOZ_ASSERT(isFresh || aPage.mState == AllocPageState::Freed);
+    MOZ_ASSERT_IF(isFresh, aPage.mArenaId == Nothing());
+    MOZ_ASSERT(isFresh == (aPage.mBaseAddr == nullptr));
+    MOZ_ASSERT(isFresh == (aPage.mAllocStack.isNothing()));
+    MOZ_ASSERT(isFresh == (aPage.mFreeStack.isNothing()));
+    MOZ_ASSERT(aPage.mReuseTime != kMaxTime);
+#endif
+  }
+
+  // RNG for deciding which allocations to treat specially. It doesn't need to
+  // be high quality.
+  //
+  // This is a raw pointer for the reason explained in the comment above
+  // GMut's constructor. Don't change it to UniquePtr or anything like that.
+  non_crypto::XorShift128PlusRNG mRNG;
+
+  AllocPageInfo mAllocPages[kNumAllocPages];
+#if PHC_LOGGING
+  Time mFreeTime[kNumAllocPages];
+
+  // How many allocations that could have been page allocs actually were? As
+  // constrained kNumAllocPages. If the hit ratio isn't close to 100% it's
+  // likely that the global constants are poorly chosen.
+  size_t mPageAllocHits = 0;
+  size_t mPageAllocMisses = 0;
+#endif
+
+  // This will only ever be updated from one thread.  The other threads should
+  // eventually get the update.
+  Atomic<PHCState, Relaxed> mPhcState =
+      Atomic<PHCState, Relaxed>(DEFAULT_STATE);
+
+  // The average delay before doing any page allocations at the start of a
+  // process. Note that roughly 1 million allocations occur in the main process
+  // while starting the browser. The delay range is 1..gAvgFirstAllocDelay*2.
+  Delay mAvgFirstAllocDelay = 64 * 1024;
+
+  // The average delay until the next attempted page allocation, once we get
+  // past the first delay. The delay range is 1..kAvgAllocDelay*2.
+  Delay mAvgAllocDelay = 16 * 1024;
+
+  // The average delay before reusing a freed page. Should be significantly
+  // larger than kAvgAllocDelay, otherwise there's not much point in having it.
+  // The delay range is (kAvgAllocDelay / 2)..(kAvgAllocDelay / 2 * 3). This is
+  // different to the other delay ranges in not having a minimum of 1, because
+  // that's such a short delay that there is a high likelihood of bad stacks in
+  // any crash report.
+  Delay mAvgPageReuseDelay = 256 * 1024;
+
+ public:
+  Delay GetAvgAllocDelay(const MutexAutoLock&) { return mAvgAllocDelay; }
+  Delay GetAvgFirstAllocDelay(const MutexAutoLock&) {
+    return mAvgFirstAllocDelay;
+  }
+  Delay GetAvgPageReuseDelay(const MutexAutoLock&) {
+    return mAvgPageReuseDelay;
+  }
+};
+
+Mutex GMut::sMutex;
+
+static GMut* gMut;
+
+// When PHC wants to crash we first have to unlock so that the crash reporter
+// can call into PHC to lockup its pointer. That also means that before calling
+// PHCCrash please ensure that state is consistent.  Because this can report an
+// arbitrary string, use of it must be reviewed by Firefox data stewards.
+static void PHCCrash(GMutLock, const char* aMessage)
+    MOZ_REQUIRES(GMut::sMutex) {
+  GMut::sMutex.Unlock();
+  MOZ_CRASH_UNSAFE(aMessage);
+}
+
+// On MacOS, 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)
+#  define PHC_THREAD_LOCAL(T) MOZ_THREAD_LOCAL(T)
+#else
+#  define PHC_THREAD_LOCAL(T) \
+    detail::ThreadLocal<T, detail::ThreadLocalKeyStorage>
+#endif
+
+// Thread-local state.
+class GTls {
+ public:
+  GTls(const GTls&) = delete;
+
+  const GTls& operator=(const GTls&) = delete;
+
+  // When true, PHC does as little as possible.
+  //
+  // (a) It does not allocate any new page allocations.
+  //
+  // (b) It avoids doing any operations that might call malloc/free/etc., which
+  //     would cause re-entry into PHC. (In practice, MozStackWalk() is the
+  //     only such operation.) Note that calls to the functions in MozJemalloc
+  //     are ok.
+  //
+  // For example, replace_malloc() will just fall back to mozjemalloc. However,
+  // operations involving existing allocations are more complex, because those
+  // existing allocations may be page allocations. For example, if
+  // replace_free() is passed a page allocation on a PHC-disabled thread, it
+  // will free the page allocation in the usual way, but it will get a dummy
+  // freeStack in order to avoid calling MozStackWalk(), as per (b) above.
+  //
+  // This single disabling mechanism has two distinct uses.
+  //
+  // - It's used to prevent re-entry into PHC, which can cause correctness
+  //   problems. For example, consider this sequence.
+  //
+  //   1. enter replace_free()
+  //   2. which calls PageFree()
+  //   3. which calls MozStackWalk()
+  //   4. which locks a mutex M, and then calls malloc
+  //   5. enter replace_malloc()
+  //   6. which calls MaybePageAlloc()
+  //   7. which calls MozStackWalk()
+  //   8. which (re)locks a mutex M --> deadlock
+  //
+  //   We avoid this sequence by "disabling" the thread in PageFree() (at step
+  //   2), which causes MaybePageAlloc() to fail, avoiding the call to
+  //   MozStackWalk() (at step 7).
+  //
+  //   In practice, realloc or free of a PHC allocation is unlikely on a thread
+  //   that is disabled because of this use: MozStackWalk() will probably only
+  //   realloc/free allocations that it allocated itself, but those won't be
+  //   page allocations because PHC is disabled before calling MozStackWalk().
+  //
+  //   (Note that MaybePageAlloc() could safely do a page allocation so long as
+  //   it avoided calling MozStackWalk() by getting a dummy allocStack. But it
+  //   wouldn't be useful, and it would prevent the second use below.)
+  //
+  // - It's used to prevent PHC allocations in some tests that rely on
+  //   mozjemalloc's exact allocation behaviour, which PHC does not replicate
+  //   exactly. (Note that (b) isn't necessary for this use -- MozStackWalk()
+  //   could be safely called -- but it is necessary for the first use above.)
+  //
+
+  static void Init() {
+    if (!tlsIsDisabled.init()) {
+      MOZ_CRASH();
+    }
+  }
+
+  static void DisableOnCurrentThread() {
+    MOZ_ASSERT(!GTls::tlsIsDisabled.get());
+    tlsIsDisabled.set(true);
+  }
+
+  static void EnableOnCurrentThread() {
+    MOZ_ASSERT(GTls::tlsIsDisabled.get());
+    MutexAutoLock lock(GMut::sMutex);
+    Delay avg_delay = gMut->GetAvgAllocDelay(lock);
+    Delay avg_first_delay = gMut->GetAvgFirstAllocDelay(lock);
+    if (GAtomic::AllocDelayHasWrapped(avg_delay, avg_first_delay)) {
+      GAtomic::SetAllocDelay(Rnd64ToDelay(avg_delay, gMut->Random64(lock)));
+    }
+    tlsIsDisabled.set(false);
+  }
+
+  static bool IsDisabledOnCurrentThread() { return tlsIsDisabled.get(); }
+
+ private:
+  static PHC_THREAD_LOCAL(bool) tlsIsDisabled;
+};
+
+PHC_THREAD_LOCAL(bool) GTls::tlsIsDisabled;
+
+class AutoDisableOnCurrentThread {
+ public:
+  AutoDisableOnCurrentThread(const AutoDisableOnCurrentThread&) = delete;
+
+  const AutoDisableOnCurrentThread& operator=(
+      const AutoDisableOnCurrentThread&) = delete;
+
+  explicit AutoDisableOnCurrentThread() { GTls::DisableOnCurrentThread(); }
+  ~AutoDisableOnCurrentThread() { GTls::EnableOnCurrentThread(); }
+};
+
+//---------------------------------------------------------------------------
+// Initialisation
+//---------------------------------------------------------------------------
+
+// WARNING: this function runs *very* early -- before all static initializers
+// have run. For this reason, non-scalar globals (gConst, gMut) are allocated
+// dynamically (so we can guarantee their construction in this function) rather
+// than statically. GAtomic and GTls contain simple static data that doesn't
+// involve static initializers so they don't need to be allocated dynamically.
+static bool phc_init() {
+  if (GetKernelPageSize() != kPageSize) {
+    return false;
+  }
+
+  // gConst and gMut are never freed. They live for the life of the process.
+  gConst = InfallibleAllocPolicy::new_<GConst>();
+
+  GTls::Init();
+  gMut = InfallibleAllocPolicy::new_<GMut>();
+
+#ifndef XP_WIN
+  // Avoid deadlocks when forking by acquiring our state lock prior to forking
+  // and releasing it after forking. See |LogAlloc|'s |replace_init| for
+  // in-depth details.
+  pthread_atfork(GMut::prefork, GMut::postfork_parent, GMut::postfork_child);
+#endif
+
+  return true;
+}
+
+static inline bool maybe_init() {
+  static bool sInitSuccess = []() { return phc_init(); }();
+  return sInitSuccess;
+}
+
+//---------------------------------------------------------------------------
+// Page allocation operations
+//---------------------------------------------------------------------------
+
+// Attempt a page allocation if the time and the size are right. Allocated
+// memory is zeroed if aZero is true. On failure, the caller should attempt a
+// normal allocation via MozJemalloc. Can be called in a context where
+// GMut::sMutex is locked.
+static void* MaybePageAlloc(const Maybe<arena_id_t>& aArenaId, size_t aReqSize,
+                            size_t aAlignment, bool aZero) {
+  MOZ_ASSERT(IsPowerOfTwo(aAlignment));
+
+  if (!maybe_init()) {
+    return nullptr;
+  }
+
+  if (aReqSize > kPageSize) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(gMut);
+  if (!gMut->ShouldMakeNewAllocations()) {
+    return nullptr;
+  }
+
+  GAtomic::IncrementNow();
+
+  // Decrement the delay. If it's zero, we do a page allocation and reset the
+  // delay to a random number. Because the assignment to the random number isn't
+  // atomic w.r.t. the decrement, we might have a sequence like this:
+  //
+  //     Thread 1                      Thread 2           Thread 3
+  //     --------                      --------           --------
+  // (a) newDelay = --sAllocDelay (-> 0)
+  // (b)                               --sAllocDelay (-> -1)
+  // (c) (newDelay != 0) fails
+  // (d)                                                  --sAllocDelay (-> -2)
+  // (e) sAllocDelay = new_random_number()
+  //
+  // It's critical that sAllocDelay has ReleaseAcquire semantics, because that
+  // guarantees that exactly one thread will see sAllocDelay have the value 0.
+  // (Relaxed semantics wouldn't guarantee that.)
+  //
+  // Note that sAllocDelay is unsigned and we expect that it will wrap after
+  // being decremented "below" zero. It must be unsigned so that IsPowerOfTwo()
+  // can work on some Delay values.
+  //
+  // Finally, note that the decrements that occur between (a) and (e) above are
+  // effectively ignored, because (e) clobbers them. This shouldn't be a
+  // problem; it effectively just adds a little more randomness to
+  // new_random_number(). An early version of this code tried to account for
+  // these decrements by doing `sAllocDelay += new_random_number()`. However, if
+  // new_random_value() is small, the number of decrements between (a) and (e)
+  // can easily exceed it, whereupon sAllocDelay ends up negative after
+  // `sAllocDelay += new_random_number()`, and the zero-check never succeeds
+  // again. (At least, not until sAllocDelay wraps around on overflow, which
+  // would take a very long time indeed.)
+  //
+  int32_t newDelay = GAtomic::DecrementDelay();
+  if (newDelay != 0) {
+    return nullptr;
+  }
+
+  if (GTls::IsDisabledOnCurrentThread()) {
+    return nullptr;
+  }
+
+  // Disable on this thread *before* getting the stack trace.
+  AutoDisableOnCurrentThread disable;
+
+  // Get the stack trace *before* locking the mutex. If we return nullptr then
+  // it was a waste, but it's not so frequent, and doing a stack walk while
+  // the mutex is locked is problematic (see the big comment on
+  // StackTrace::Fill() for details).
+  StackTrace allocStack;
+  allocStack.Fill();
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  Time now = GAtomic::Now();
+  Delay newAllocDelay =
+      Rnd64ToDelay(gMut->GetAvgAllocDelay(lock), gMut->Random64(lock));
+
+  // We start at a random page alloc and wrap around, to ensure pages get even
+  // amounts of use.
+  uint8_t* ptr = nullptr;
+  uint8_t* pagePtr = nullptr;
+  for (uintptr_t n = 0, i = size_t(gMut->Random64(lock)) % kNumAllocPages;
+       n < kNumAllocPages; n++, i = (i + 1) % kNumAllocPages) {
+    if (!gMut->IsPageAllocatable(lock, i, now)) {
+      continue;
+    }
+
+#if PHC_LOGGING
+    Time lifetime = 0;
+#endif
+    pagePtr = gConst->AllocPagePtr(i);
+    MOZ_ASSERT(pagePtr);
+    bool ok =
+#ifdef XP_WIN
+        !!VirtualAlloc(pagePtr, kPageSize, MEM_COMMIT, PAGE_READWRITE);
+#else
+        mprotect(pagePtr, kPageSize, PROT_READ | PROT_WRITE) == 0;
+#endif
+
+    if (!ok) {
+      pagePtr = nullptr;
+      continue;
+    }
+
+    size_t usableSize = MozJemalloc::malloc_good_size(aReqSize);
+    MOZ_ASSERT(usableSize > 0);
+
+    // Put the allocation as close to the end of the page as possible,
+    // allowing for alignment requirements.
+    ptr = pagePtr + kPageSize - usableSize;
+    if (aAlignment != 1) {
+      ptr = reinterpret_cast<uint8_t*>(
+          (reinterpret_cast<uintptr_t>(ptr) & ~(aAlignment - 1)));
+    }
+
+#if PHC_LOGGING
+    Time then = gMut->GetFreeTime(i);
+    lifetime = then != 0 ? now - then : 0;
+#endif
+
+    gMut->SetPageInUse(lock, i, aArenaId, ptr, allocStack);
+
+    if (aZero) {
+      memset(ptr, 0, usableSize);
+    } else {
+#ifdef DEBUG
+      memset(ptr, kAllocJunk, usableSize);
+#endif
+    }
+
+    gMut->IncPageAllocHits(lock);
+#if PHC_LOGGING
+    phc::PHCStats stats = gMut->GetPageStats(lock);
+#endif
+    LOG("PageAlloc(%zu, %zu) -> %p[%zu]/%p (%zu) (z%zu), sAllocDelay <- %zu, "
+        "fullness %zu/%zu/%zu, hits %zu/%zu (%zu%%), lifetime %zu\n",
+        aReqSize, aAlignment, pagePtr, i, ptr, usableSize, size_t(aZero),
+        size_t(newAllocDelay), stats.mSlotsAllocated, stats.mSlotsFreed,
+        kNumAllocPages, gMut->PageAllocHits(lock),
+        gMut->PageAllocAttempts(lock), gMut->PageAllocHitRate(lock), lifetime);
+    break;
+  }
+
+  if (!pagePtr) {
+    // No pages are available, or VirtualAlloc/mprotect failed.
+    gMut->IncPageAllocMisses(lock);
+#if PHC_LOGGING
+    phc::PHCStats stats = gMut->GetPageStats(lock);
+#endif
+    LOG("No PageAlloc(%zu, %zu), sAllocDelay <- %zu, fullness %zu/%zu/%zu, "
+        "hits %zu/%zu (%zu%%)\n",
+        aReqSize, aAlignment, size_t(newAllocDelay), stats.mSlotsAllocated,
+        stats.mSlotsFreed, kNumAllocPages, gMut->PageAllocHits(lock),
+        gMut->PageAllocAttempts(lock), gMut->PageAllocHitRate(lock));
+  }
+
+  // Set the new alloc delay.
+  GAtomic::SetAllocDelay(newAllocDelay);
+
+  return ptr;
+}
+
+static void FreePage(GMutLock aLock, uintptr_t aIndex,
+                     const Maybe<arena_id_t>& aArenaId,
+                     const StackTrace& aFreeStack, Delay aReuseDelay)
+    MOZ_REQUIRES(GMut::sMutex) {
+  void* pagePtr = gConst->AllocPagePtr(aIndex);
+
+#ifdef XP_WIN
+  if (!VirtualFree(pagePtr, kPageSize, MEM_DECOMMIT)) {
+    PHCCrash(aLock, "VirtualFree failed");
+  }
+#else
+  if (mmap(pagePtr, kPageSize, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON,
+           -1, 0) == MAP_FAILED) {
+    PHCCrash(aLock, "mmap failed");
+  }
+#endif
+
+  gMut->SetPageFreed(aLock, aIndex, aArenaId, aFreeStack, aReuseDelay);
+}
+
+//---------------------------------------------------------------------------
+// replace-malloc machinery
+//---------------------------------------------------------------------------
+
+// This handles malloc, moz_arena_malloc, and realloc-with-a-nullptr.
+MOZ_ALWAYS_INLINE static void* PageMalloc(const Maybe<arena_id_t>& aArenaId,
+                                          size_t aReqSize) {
+  void* ptr = MaybePageAlloc(aArenaId, aReqSize, /* aAlignment */ 1,
+                             /* aZero */ false);
+  return ptr ? ptr
+             : (aArenaId.isSome()
+                    ? MozJemalloc::moz_arena_malloc(*aArenaId, aReqSize)
+                    : MozJemalloc::malloc(aReqSize));
+}
+
+inline void* MozJemallocPHC::malloc(size_t aReqSize) {
+  return PageMalloc(Nothing(), aReqSize);
+}
+
+static Delay ReuseDelay(GMutLock aLock) {
+  Delay avg_reuse_delay = gMut->GetAvgPageReuseDelay(aLock);
+  return (avg_reuse_delay / 2) +
+         Rnd64ToDelay(avg_reuse_delay / 2, gMut->Random64(aLock));
+}
+
+// This handles both calloc and moz_arena_calloc.
+MOZ_ALWAYS_INLINE static void* PageCalloc(const Maybe<arena_id_t>& aArenaId,
+                                          size_t aNum, size_t aReqSize) {
+  CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aNum) * aReqSize;
+  if (!checkedSize.isValid()) {
+    return nullptr;
+  }
+
+  void* ptr = MaybePageAlloc(aArenaId, checkedSize.value(), /* aAlignment */ 1,
+                             /* aZero */ true);
+  return ptr ? ptr
+             : (aArenaId.isSome()
+                    ? MozJemalloc::moz_arena_calloc(*aArenaId, aNum, aReqSize)
+                    : MozJemalloc::calloc(aNum, aReqSize));
+}
+
+inline void* MozJemallocPHC::calloc(size_t aNum, size_t aReqSize) {
+  return PageCalloc(Nothing(), aNum, aReqSize);
+}
+
+// This function handles both realloc and moz_arena_realloc.
+//
+// As always, realloc is complicated, and doubly so when there are two
+// different kinds of allocations in play. Here are the possible transitions,
+// and what we do in practice.
+//
+// - normal-to-normal: This is straightforward and obviously necessary.
+//
+// - normal-to-page: This is disallowed because it would require getting the
+//   arenaId of the normal allocation, which isn't possible in non-DEBUG builds
+//   for security reasons.
+//
+// - page-to-page: This is done whenever possible, i.e. whenever the new size
+//   is less than or equal to 4 KiB. This choice counterbalances the
+//   disallowing of normal-to-page allocations, in order to avoid biasing
+//   towards or away from page allocations. It always occurs in-place.
+//
+// - page-to-normal: this is done only when necessary, i.e. only when the new
+//   size is greater than 4 KiB. This choice naturally flows from the
+//   prior choice on page-to-page transitions.
+//
+// In summary: realloc doesn't change the allocation kind unless it must.
+//
+MOZ_ALWAYS_INLINE static void* MaybePageRealloc(
+    const Maybe<arena_id_t>& aArenaId, void* aOldPtr, size_t aNewSize) {
+  if (!aOldPtr) {
+    // Null pointer. Treat like malloc(aNewSize).
+    return PageMalloc(aArenaId, aNewSize);
+  }
+
+  if (!maybe_init()) {
+    return nullptr;
+  }
+
+  PtrKind pk = gConst->PtrKind(aOldPtr);
+  if (pk.IsNothing()) {
+    // A normal-to-normal transition.
+    return nullptr;
+  }
+
+  if (pk.IsGuardPage()) {
+    GMut::CrashOnGuardPage(aOldPtr);
+  }
+
+  // At this point we know we have an allocation page.
+  uintptr_t index = pk.AllocPageIndex();
+
+  // A page-to-something transition.
+
+  // Note that `disable` has no effect unless it is emplaced below.
+  Maybe<AutoDisableOnCurrentThread> disable;
+  // Get the stack trace *before* locking the mutex.
+  StackTrace stack;
+  if (GTls::IsDisabledOnCurrentThread()) {
+    // PHC is disabled on this thread. Leave the stack empty.
+  } else {
+    // Disable on this thread *before* getting the stack trace.
+    disable.emplace();
+    stack.Fill();
+  }
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  // Check for realloc() of a freed block.
+  gMut->EnsureValidAndInUse(lock, aOldPtr, index);
+
+  if (aNewSize <= kPageSize && gMut->ShouldMakeNewAllocations()) {
+    // A page-to-page transition. Just keep using the page allocation. We do
+    // this even if the thread is disabled, because it doesn't create a new
+    // page allocation. Note that ResizePageInUse() checks aArenaId.
+    //
+    // Move the bytes with memmove(), because the old allocation and the new
+    // allocation overlap. Move the usable size rather than the requested size,
+    // because the user might have used malloc_usable_size() and filled up the
+    // usable size.
+    size_t oldUsableSize = gMut->PageUsableSize(lock, index);
+    size_t newUsableSize = MozJemalloc::malloc_good_size(aNewSize);
+    uint8_t* pagePtr = gConst->AllocPagePtr(index);
+    uint8_t* newPtr = pagePtr + kPageSize - newUsableSize;
+    memmove(newPtr, aOldPtr, std::min(oldUsableSize, aNewSize));
+    gMut->ResizePageInUse(lock, index, aArenaId, newPtr, stack);
+    LOG("PageRealloc-Reuse(%p, %zu) -> %p\n", aOldPtr, aNewSize, newPtr);
+    return newPtr;
+  }
+
+  // A page-to-normal transition (with the new size greater than page-sized).
+  // (Note that aArenaId is checked below.)
+  void* newPtr;
+  if (aArenaId.isSome()) {
+    newPtr = MozJemalloc::moz_arena_malloc(*aArenaId, aNewSize);
+  } else {
+    Maybe<arena_id_t> oldArenaId = gMut->PageArena(lock, index);
+    newPtr = (oldArenaId.isSome()
+                  ? MozJemalloc::moz_arena_malloc(*oldArenaId, aNewSize)
+                  : MozJemalloc::malloc(aNewSize));
+  }
+  if (!newPtr) {
+    return nullptr;
+  }
+
+  Delay reuseDelay = ReuseDelay(lock);
+
+  // Copy the usable size rather than the requested size, because the user
+  // might have used malloc_usable_size() and filled up the usable size. Note
+  // that FreePage() checks aArenaId (via SetPageFreed()).
+  size_t oldUsableSize = gMut->PageUsableSize(lock, index);
+  memcpy(newPtr, aOldPtr, std::min(oldUsableSize, aNewSize));
+  FreePage(lock, index, aArenaId, stack, reuseDelay);
+  LOG("PageRealloc-Free(%p[%zu], %zu) -> %p, %zu delay, reuse at ~%zu\n",
+      aOldPtr, index, aNewSize, newPtr, size_t(reuseDelay),
+      size_t(GAtomic::Now()) + reuseDelay);
+
+  return newPtr;
+}
+
+MOZ_ALWAYS_INLINE static void* PageRealloc(const Maybe<arena_id_t>& aArenaId,
+                                           void* aOldPtr, size_t aNewSize) {
+  void* ptr = MaybePageRealloc(aArenaId, aOldPtr, aNewSize);
+
+  return ptr ? ptr
+             : (aArenaId.isSome() ? MozJemalloc::moz_arena_realloc(
+                                        *aArenaId, aOldPtr, aNewSize)
+                                  : MozJemalloc::realloc(aOldPtr, aNewSize));
+}
+
+inline void* MozJemallocPHC::realloc(void* aOldPtr, size_t aNewSize) {
+  return PageRealloc(Nothing(), aOldPtr, aNewSize);
+}
+
+// This handles both free and moz_arena_free.
+MOZ_ALWAYS_INLINE static bool MaybePageFree(const Maybe<arena_id_t>& aArenaId,
+                                            void* aPtr) {
+  if (!maybe_init()) {
+    return false;
+  }
+
+  PtrKind pk = gConst->PtrKind(aPtr);
+  if (pk.IsNothing()) {
+    // Not a page allocation.
+    return false;
+  }
+
+  if (pk.IsGuardPage()) {
+    GMut::CrashOnGuardPage(aPtr);
+  }
+
+  // At this point we know we have an allocation page.
+  uintptr_t index = pk.AllocPageIndex();
+
+  // Note that `disable` has no effect unless it is emplaced below.
+  Maybe<AutoDisableOnCurrentThread> disable;
+  // Get the stack trace *before* locking the mutex.
+  StackTrace freeStack;
+  if (GTls::IsDisabledOnCurrentThread()) {
+    // PHC is disabled on this thread. Leave the stack empty.
+  } else {
+    // Disable on this thread *before* getting the stack trace.
+    disable.emplace();
+    freeStack.Fill();
+  }
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  // Check for a double-free.
+  gMut->EnsureValidAndInUse(lock, aPtr, index);
+
+  // Note that FreePage() checks aArenaId (via SetPageFreed()).
+  Delay reuseDelay = ReuseDelay(lock);
+  FreePage(lock, index, aArenaId, freeStack, reuseDelay);
+
+#if PHC_LOGGING
+  phc::PHCStats stats = gMut->GetPageStats(lock);
+#endif
+  LOG("PageFree(%p[%zu]), %zu delay, reuse at ~%zu, fullness %zu/%zu/%zu\n",
+      aPtr, index, size_t(reuseDelay), size_t(GAtomic::Now()) + reuseDelay,
+      stats.mSlotsAllocated, stats.mSlotsFreed, kNumAllocPages);
+
+  return true;
+}
+
+MOZ_ALWAYS_INLINE static void PageFree(const Maybe<arena_id_t>& aArenaId,
+                                       void* aPtr) {
+  bool res = MaybePageFree(aArenaId, aPtr);
+  if (!res) {
+    aArenaId.isSome() ? MozJemalloc::moz_arena_free(*aArenaId, aPtr)
+                      : MozJemalloc::free(aPtr);
+  }
+}
+
+inline void MozJemallocPHC::free(void* aPtr) { PageFree(Nothing(), aPtr); }
+
+// This handles memalign and moz_arena_memalign.
+MOZ_ALWAYS_INLINE static void* PageMemalign(const Maybe<arena_id_t>& aArenaId,
+                                            size_t aAlignment,
+                                            size_t aReqSize) {
+  MOZ_RELEASE_ASSERT(IsPowerOfTwo(aAlignment));
+
+  // PHC can't satisfy an alignment greater than a page size, so fall back to
+  // mozjemalloc in that case.
+  void* ptr = nullptr;
+  if (aAlignment <= kPageSize) {
+    ptr = MaybePageAlloc(aArenaId, aReqSize, aAlignment, /* aZero */ false);
+  }
+  return ptr ? ptr
+             : (aArenaId.isSome()
+                    ? MozJemalloc::moz_arena_memalign(*aArenaId, aAlignment,
+                                                      aReqSize)
+                    : MozJemalloc::memalign(aAlignment, aReqSize));
+}
+
+inline void* MozJemallocPHC::memalign(size_t aAlignment, size_t aReqSize) {
+  return PageMemalign(Nothing(), aAlignment, aReqSize);
+}
+
+inline size_t MozJemallocPHC::malloc_usable_size(usable_ptr_t aPtr) {
+  if (!maybe_init()) {
+    return MozJemalloc::malloc_usable_size(aPtr);
+  }
+
+  PtrKind pk = gConst->PtrKind(aPtr);
+  if (pk.IsNothing()) {
+    // Not a page allocation. Measure it normally.
+    return MozJemalloc::malloc_usable_size(aPtr);
+  }
+
+  if (pk.IsGuardPage()) {
+    GMut::CrashOnGuardPage(const_cast<void*>(aPtr));
+  }
+
+  // At this point we know aPtr lands within an allocation page, due to the
+  // math done in the PtrKind constructor. But if aPtr points to memory
+  // before the base address of the allocation, we return 0.
+  uintptr_t index = pk.AllocPageIndex();
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  void* pageBaseAddr = gMut->AllocPageBaseAddr(lock, index);
+
+  if (MOZ_UNLIKELY(aPtr < pageBaseAddr)) {
+    return 0;
+  }
+
+  return gMut->PageUsableSize(lock, index);
+}
+
+static size_t metadata_size() {
+  return MozJemalloc::malloc_usable_size(gConst) +
+         MozJemalloc::malloc_usable_size(gMut);
+}
+
+inline void MozJemallocPHC::jemalloc_stats_internal(
+    jemalloc_stats_t* aStats, jemalloc_bin_stats_t* aBinStats) {
+  MozJemalloc::jemalloc_stats_internal(aStats, aBinStats);
+
+  if (!maybe_init()) {
+    // If we're not initialised, then we're not using any additional memory and
+    // have nothing to add to the report.
+    return;
+  }
+
+  // We allocate our memory from jemalloc so it has already counted our memory
+  // usage within "mapped" and "allocated", we must subtract the memory we
+  // allocated from jemalloc from allocated before adding in only the parts that
+  // we have allocated out to Firefox.
+
+  aStats->allocated -= kAllPagesJemallocSize;
+
+  size_t allocated = 0;
+  {
+    MutexAutoLock lock(GMut::sMutex);
+
+    // Add usable space of in-use allocations to `allocated`.
+    for (size_t i = 0; i < kNumAllocPages; i++) {
+      if (gMut->IsPageInUse(lock, i)) {
+        allocated += gMut->PageUsableSize(lock, i);
+      }
+    }
+  }
+  aStats->allocated += allocated;
+
+  // guards is the gap between `allocated` and `mapped`. In some ways this
+  // almost fits into aStats->wasted since it feels like wasted memory. However
+  // wasted should only include committed memory and these guard pages are
+  // uncommitted. Therefore we don't include it anywhere.
+  // size_t guards = mapped - allocated;
+
+  // aStats.page_cache and aStats.bin_unused are left unchanged because PHC
+  // doesn't have anything corresponding to those.
+
+  // The metadata is stored in normal heap allocations, so they're measured by
+  // mozjemalloc as `allocated`. Move them into `bookkeeping`.
+  // They're also reported under explicit/heap-overhead/phc/fragmentation in
+  // about:memory.
+  size_t bookkeeping = metadata_size();
+  aStats->allocated -= bookkeeping;
+  aStats->bookkeeping += bookkeeping;
+}
+
+inline void MozJemallocPHC::jemalloc_ptr_info(const void* aPtr,
+                                              jemalloc_ptr_info_t* aInfo) {
+  if (!maybe_init()) {
+    return MozJemalloc::jemalloc_ptr_info(aPtr, aInfo);
+  }
+
+  // We need to implement this properly, because various code locations do
+  // things like checking that allocations are in the expected arena.
+  PtrKind pk = gConst->PtrKind(aPtr);
+  if (pk.IsNothing()) {
+    // Not a page allocation.
+    return MozJemalloc::jemalloc_ptr_info(aPtr, aInfo);
+  }
+
+  if (pk.IsGuardPage()) {
+    // Treat a guard page as unknown because there's no better alternative.
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+    return;
+  }
+
+  // At this point we know we have an allocation page.
+  uintptr_t index = pk.AllocPageIndex();
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  gMut->FillJemallocPtrInfo(lock, aPtr, index, aInfo);
+#if DEBUG
+  LOG("JemallocPtrInfo(%p[%zu]) -> {%zu, %p, %zu, %zu}\n", aPtr, index,
+      size_t(aInfo->tag), aInfo->addr, aInfo->size, aInfo->arenaId);
+#else
+  LOG("JemallocPtrInfo(%p[%zu]) -> {%zu, %p, %zu}\n", aPtr, index,
+      size_t(aInfo->tag), aInfo->addr, aInfo->size);
+#endif
+}
+
+inline void* MozJemallocPHC::moz_arena_malloc(arena_id_t aArenaId,
+                                              size_t aReqSize) {
+  return PageMalloc(Some(aArenaId), aReqSize);
+}
+
+inline void* MozJemallocPHC::moz_arena_calloc(arena_id_t aArenaId, size_t aNum,
+                                              size_t aReqSize) {
+  return PageCalloc(Some(aArenaId), aNum, aReqSize);
+}
+
+inline void* MozJemallocPHC::moz_arena_realloc(arena_id_t aArenaId,
+                                               void* aOldPtr, size_t aNewSize) {
+  return PageRealloc(Some(aArenaId), aOldPtr, aNewSize);
+}
+
+inline void MozJemallocPHC::moz_arena_free(arena_id_t aArenaId, void* aPtr) {
+  return PageFree(Some(aArenaId), aPtr);
+}
+
+inline void* MozJemallocPHC::moz_arena_memalign(arena_id_t aArenaId,
+                                                size_t aAlignment,
+                                                size_t aReqSize) {
+  return PageMemalign(Some(aArenaId), aAlignment, aReqSize);
+}
+
+namespace mozilla::phc {
+
+bool IsPHCAllocation(const void* aPtr, AddrInfo* aOut) {
+  if (!maybe_init()) {
+    return false;
+  }
+
+  PtrKind pk = gConst->PtrKind(aPtr);
+  if (pk.IsNothing()) {
+    return false;
+  }
+
+  bool isGuardPage = false;
+  if (pk.IsGuardPage()) {
+    if ((uintptr_t(aPtr) % kPageSize) < (kPageSize / 2)) {
+      // The address is in the lower half of a guard page, so it's probably an
+      // overflow. But first check that it is not on the very first guard
+      // page, in which case it cannot be an overflow, and we ignore it.
+      if (gConst->IsInFirstGuardPage(aPtr)) {
+        return false;
+      }
+
+      // Get the allocation page preceding this guard page.
+      pk = gConst->PtrKind(static_cast<const uint8_t*>(aPtr) - kPageSize);
+
+    } else {
+      // The address is in the upper half of a guard page, so it's probably an
+      // underflow. Get the allocation page following this guard page.
+      pk = gConst->PtrKind(static_cast<const uint8_t*>(aPtr) + kPageSize);
+    }
+
+    // Make a note of the fact that we hit a guard page.
+    isGuardPage = true;
+  }
+
+  // At this point we know we have an allocation page.
+  uintptr_t index = pk.AllocPageIndex();
+
+  if (aOut) {
+    if (GMut::sMutex.TryLock()) {
+      gMut->FillAddrInfo(index, aPtr, isGuardPage, *aOut);
+      LOG("IsPHCAllocation: %zu, %p, %zu, %zu, %zu\n", size_t(aOut->mKind),
+          aOut->mBaseAddr, aOut->mUsableSize,
+          aOut->mAllocStack.isSome() ? aOut->mAllocStack->mLength : 0,
+          aOut->mFreeStack.isSome() ? aOut->mFreeStack->mLength : 0);
+      GMut::sMutex.Unlock();
+    } else {
+      LOG("IsPHCAllocation: PHC is locked\n");
+      aOut->mPhcWasLocked = true;
+    }
+  }
+  return true;
+}
+
+void DisablePHCOnCurrentThread() {
+  GTls::DisableOnCurrentThread();
+  LOG("DisablePHCOnCurrentThread: %zu\n", 0ul);
+}
+
+void ReenablePHCOnCurrentThread() {
+  GTls::EnableOnCurrentThread();
+  LOG("ReenablePHCOnCurrentThread: %zu\n", 0ul);
+}
+
+bool IsPHCEnabledOnCurrentThread() {
+  bool enabled = !GTls::IsDisabledOnCurrentThread();
+  LOG("IsPHCEnabledOnCurrentThread: %zu\n", size_t(enabled));
+  return enabled;
+}
+
+void PHCMemoryUsage(MemoryUsage& aMemoryUsage) {
+  if (!maybe_init()) {
+    aMemoryUsage = MemoryUsage();
+    return;
+  }
+
+  aMemoryUsage.mMetadataBytes = metadata_size();
+  if (gMut) {
+    MutexAutoLock lock(GMut::sMutex);
+    aMemoryUsage.mFragmentationBytes = gMut->FragmentationBytes();
+  } else {
+    aMemoryUsage.mFragmentationBytes = 0;
+  }
+}
+
+void GetPHCStats(PHCStats& aStats) {
+  if (!maybe_init()) {
+    aStats = PHCStats();
+    return;
+  }
+
+  MutexAutoLock lock(GMut::sMutex);
+
+  aStats = gMut->GetPageStats(lock);
+}
+
+// Enable or Disable PHC at runtime.  If PHC is disabled it will still trap
+// bad uses of previous allocations, but won't track any new allocations.
+void SetPHCState(PHCState aState) {
+  if (!maybe_init()) {
+    return;
+  }
+
+  gMut->SetState(aState);
+}
+
+void SetPHCProbabilities(int64_t aAvgDelayFirst, int64_t aAvgDelayNormal,
+                         int64_t aAvgDelayPageReuse) {
+  if (!maybe_init()) {
+    return;
+  }
+
+  gMut->SetProbabilities(aAvgDelayFirst, aAvgDelayNormal, aAvgDelayPageReuse);
+}
+
+}  // namespace mozilla::phc
diff --git a/memory/build/PHC.h b/memory/build/PHC.h
new file mode 100644
index 0000000000..78820a5cf3
--- /dev/null
+++ b/memory/build/PHC.h
@@ -0,0 +1,160 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=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/. */
+
+#ifndef PHC_h
+#define PHC_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Maybe.h"
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "mozmemory_wrap.h"
+
+namespace mozilla {
+namespace phc {
+
+// Note: a stack trace may have no frames due to a collection problem.
+//
+// Also note: a more compact stack trace representation could be achieved with
+// some effort.
+struct StackTrace {
+ public:
+  static const size_t kMaxFrames = 16;
+
+  // The number of PCs in the stack trace.
+  size_t mLength;
+
+  // The PCs in the stack trace. Only the first mLength are initialized.
+  const void* mPcs[kMaxFrames];
+
+ public:
+  StackTrace() : mLength(0) {}
+};
+
+// Info from PHC about an address in memory.
+class AddrInfo {
+ public:
+  enum class Kind {
+    // The address is not in PHC-managed memory.
+    Unknown = 0,
+
+    // The address is within a PHC page that has never been allocated. A crash
+    // involving such an address is unlikely in practice, because it would
+    // require the crash to happen quite early.
+    NeverAllocatedPage = 1,
+
+    // The address is within a PHC page that is in use.
+    InUsePage = 2,
+
+    // The address is within a PHC page that has been allocated and then freed.
+    // A crash involving such an address most likely indicates a
+    // use-after-free. (A sufficiently wild write -- e.g. a large buffer
+    // overflow -- could also trigger it, but this is less likely.)
+    FreedPage = 3,
+
+    // The address is within a PHC guard page. A crash involving such an
+    // address most likely indicates a buffer overflow. (Again, a sufficiently
+    // wild write could unluckily trigger it, but this is less likely.)
+    GuardPage = 4,
+  };
+
+  // The page kind.
+  Kind mKind;
+
+  // The starting address of the allocation.
+  // - Unknown | NeverAllocatedPage: nullptr.
+  // - InUsePage | FreedPage: the address of the allocation within the page.
+  // - GuardPage: the mBaseAddr value from the preceding allocation page.
+  const void* mBaseAddr;
+
+  // The usable size, which could be bigger than the requested size.
+  // - Unknown | NeverAllocatePage: 0.
+  // - InUsePage | FreedPage: the usable size of the allocation within the page.
+  // - GuardPage: the mUsableSize value from the preceding allocation page.
+  size_t mUsableSize;
+
+  // The allocation stack.
+  // - Unknown | NeverAllocatedPage: Nothing.
+  // - InUsePage | FreedPage: Some.
+  // - GuardPage: the mAllocStack value from the preceding allocation page.
+  mozilla::Maybe<StackTrace> mAllocStack;
+
+  // The free stack.
+  // - Unknown | NeverAllocatedPage | InUsePage: Nothing.
+  // - FreedPage: Some.
+  // - GuardPage: the mFreeStack value from the preceding allocation page.
+  mozilla::Maybe<StackTrace> mFreeStack;
+
+  // True if PHC was locked and therefore we couldn't retrive some infomation.
+  bool mPhcWasLocked = false;
+
+  // Default to no PHC info.
+  AddrInfo() : mKind(Kind::Unknown), mBaseAddr(nullptr), mUsableSize(0) {}
+};
+
+// Global instance that is retrieved by the process generating the crash report
+extern AddrInfo gAddrInfo;
+
+// If this is a PHC-handled address, return true, and if an AddrInfo is
+// provided, fill in all of its fields. Otherwise, return false and leave
+// AddrInfo unchanged.
+MOZ_JEMALLOC_API bool IsPHCAllocation(const void*, AddrInfo*);
+
+// Disable PHC allocations on the current thread. Only useful for tests. Note
+// that PHC deallocations will still occur as needed.
+MOZ_JEMALLOC_API void DisablePHCOnCurrentThread();
+
+// Re-enable PHC allocations on the current thread. Only useful for tests.
+MOZ_JEMALLOC_API void ReenablePHCOnCurrentThread();
+
+// Test whether PHC allocations are enabled on the current thread. Only
+// useful for tests.
+MOZ_JEMALLOC_API bool IsPHCEnabledOnCurrentThread();
+
+// PHC has three different states:
+//  * Not compiled in
+//  * OnlyFree         - The memory allocator is hooked but new allocations
+//                       requests will be forwarded to mozjemalloc, free() will
+//                       correctly free any PHC allocations and realloc() will
+//                       "move" PHC allocations to mozjemalloc allocations.
+//  * Enabled          - Full use.
+enum PHCState {
+  OnlyFree,
+  Enabled,
+};
+
+MOZ_JEMALLOC_API void SetPHCState(PHCState aState);
+
+MOZ_JEMALLOC_API void SetPHCProbabilities(int64_t aAvgDelayFirst,
+                                          int64_t aAvgDelayNormal,
+                                          int64_t aAvgDelayPageReuse);
+
+struct MemoryUsage {
+  // The amount of memory used for PHC metadata, eg information about each
+  // allocation including stacks.
+  size_t mMetadataBytes = 0;
+
+  // The amount of memory lost due to rounding allocation sizes up to the
+  // nearest page.  AKA internal fragmentation.
+  size_t mFragmentationBytes = 0;
+};
+
+MOZ_JEMALLOC_API void PHCMemoryUsage(MemoryUsage& aMemoryUsage);
+
+struct PHCStats {
+  size_t mSlotsAllocated = 0;
+  size_t mSlotsFreed = 0;
+  size_t mSlotsUnused = 0;
+};
+
+// Return PHC memory usage information by filling in the supplied structure.
+MOZ_JEMALLOC_API void GetPHCStats(PHCStats& aStats);
+
+}  // namespace phc
+}  // namespace mozilla
+
+#endif /* PHC_h */
diff --git a/memory/build/Utils.h b/memory/build/Utils.h
new file mode 100644
index 0000000000..b1a05e7ae3
--- /dev/null
+++ b/memory/build/Utils.h
@@ -0,0 +1,115 @@
+/* -*- 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/. */
+
+#ifndef Utils_h
+#define Utils_h
+
+#include <type_traits>
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/TemplateLib.h"
+
+// Helper for log2 of powers of 2 at compile time.
+template <size_t N>
+struct Log2 : mozilla::tl::CeilingLog2<N> {
+  using mozilla::tl::CeilingLog2<N>::value;
+  static_assert(1ULL << value == N, "Number is not a power of 2");
+};
+#define LOG2(N) Log2<N>::value
+
+enum class Order {
+  eLess = -1,
+  eEqual = 0,
+  eGreater = 1,
+};
+
+// Compare two integers. Returns whether the first integer is Less,
+// Equal or Greater than the second integer.
+template <typename T>
+Order CompareInt(T aValue1, T aValue2) {
+  static_assert(std::is_integral_v<T>, "Type must be integral");
+  if (aValue1 < aValue2) {
+    return Order::eLess;
+  }
+  if (aValue1 > aValue2) {
+    return Order::eGreater;
+  }
+  return Order::eEqual;
+}
+
+// Compare two addresses. Returns whether the first address is Less,
+// Equal or Greater than the second address.
+template <typename T>
+Order CompareAddr(T* aAddr1, T* aAddr2) {
+  return CompareInt(uintptr_t(aAddr1), uintptr_t(aAddr2));
+}
+
+// Helper for (fast) comparison of fractions without involving divisions or
+// floats.
+class Fraction {
+ public:
+  explicit constexpr Fraction(size_t aNumerator, size_t aDenominator)
+      : mNumerator(aNumerator), mDenominator(aDenominator) {}
+
+  MOZ_IMPLICIT constexpr Fraction(long double aValue)
+      // We use an arbitrary power of two as denominator that provides enough
+      // precision for our use case.
+      : mNumerator(aValue * 4096), mDenominator(4096) {}
+
+  inline bool operator<(const Fraction& aOther) const {
+#ifndef MOZ_DEBUG
+    // We are comparing A / B < C / D, with all A, B, C and D being positive
+    // numbers. Multiplying both sides with B * D, we have:
+    // (A * B * D) / B < (C * B * D) / D, which can then be simplified as
+    // A * D < C * B. When can thus compare our fractions without actually
+    // doing any division.
+    // This however assumes the multiplied quantities are small enough not
+    // to overflow the multiplication. We use CheckedInt on debug builds
+    // to enforce the assumption.
+    return mNumerator * aOther.mDenominator < aOther.mNumerator * mDenominator;
+#else
+    mozilla::CheckedInt<size_t> numerator(mNumerator);
+    mozilla::CheckedInt<size_t> denominator(mDenominator);
+    // value() asserts when the multiplication overflowed.
+    size_t lhs = (numerator * aOther.mDenominator).value();
+    size_t rhs = (aOther.mNumerator * denominator).value();
+    return lhs < rhs;
+#endif
+  }
+
+  inline bool operator>(const Fraction& aOther) const { return aOther < *this; }
+
+  inline bool operator>=(const Fraction& aOther) const {
+    return !(*this < aOther);
+  }
+
+  inline bool operator<=(const Fraction& aOther) const {
+    return !(*this > aOther);
+  }
+
+  inline bool operator==(const Fraction& aOther) const {
+#ifndef MOZ_DEBUG
+    // Same logic as operator<
+    return mNumerator * aOther.mDenominator == aOther.mNumerator * mDenominator;
+#else
+    mozilla::CheckedInt<size_t> numerator(mNumerator);
+    mozilla::CheckedInt<size_t> denominator(mDenominator);
+    size_t lhs = (numerator * aOther.mDenominator).value();
+    size_t rhs = (aOther.mNumerator * denominator).value();
+    return lhs == rhs;
+#endif
+  }
+
+  inline bool operator!=(const Fraction& aOther) const {
+    return !(*this == aOther);
+  }
+
+ private:
+  size_t mNumerator;
+  size_t mDenominator;
+};
+
+#endif
diff --git a/memory/build/fallback.cpp b/memory/build/fallback.cpp
new file mode 100644
index 0000000000..6f1791bed9
--- /dev/null
+++ b/memory/build/fallback.cpp
@@ -0,0 +1,40 @@
+/* -*- 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 "mozmemory.h"
+#include "mozjemalloc.h"
+#include <stdlib.h>
+
+#ifndef HAVE_MEMALIGN
+MOZ_MEMORY_API void* memalign(size_t aAlignment, size_t aSize) {
+#  ifdef XP_WIN
+  return _aligned_malloc(aSize, aAlignment);
+#  else
+  void* ret;
+  if (posix_memalign(&ret, aAlignment, aSize) != 0) {
+    return nullptr;
+  }
+  return ret;
+#  endif
+}
+#endif
+
+struct SystemMalloc {
+#define MALLOC_DECL(name, return_type, ...)                                \
+  static inline return_type name(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
+    return ::name(ARGS_HELPER(ARGS, ##__VA_ARGS__));                       \
+  }
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#include "malloc_decls.h"
+};
+
+#define MALLOC_DECL(name, return_type, ...)                                   \
+  MOZ_JEMALLOC_API return_type name(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
+    return DummyArenaAllocator<SystemMalloc>::name(                           \
+        ARGS_HELPER(ARGS, ##__VA_ARGS__));                                    \
+  }
+#define MALLOC_FUNCS MALLOC_FUNCS_ARENA
+#include "malloc_decls.h"
diff --git a/memory/build/malloc_decls.h b/memory/build/malloc_decls.h
new file mode 100644
index 0000000000..ec56344a37
--- /dev/null
+++ b/memory/build/malloc_decls.h
@@ -0,0 +1,161 @@
+/* -*- 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/. */
+
+// Helper header to declare all the supported malloc functions.
+// MALLOC_DECL arguments are:
+//   - function name
+//   - return type
+//   - argument types
+
+#ifndef malloc_decls_h
+#  define malloc_decls_h
+
+#  include "mozjemalloc_types.h"
+
+#  define MALLOC_FUNCS_MALLOC_BASE 1
+#  define MALLOC_FUNCS_MALLOC_EXTRA 2
+#  define MALLOC_FUNCS_MALLOC \
+    (MALLOC_FUNCS_MALLOC_BASE | MALLOC_FUNCS_MALLOC_EXTRA)
+#  define MALLOC_FUNCS_JEMALLOC 4
+#  define MALLOC_FUNCS_ARENA_BASE 8
+#  define MALLOC_FUNCS_ARENA_ALLOC 16
+#  define MALLOC_FUNCS_ARENA \
+    (MALLOC_FUNCS_ARENA_BASE | MALLOC_FUNCS_ARENA_ALLOC)
+#  define MALLOC_FUNCS_ALL \
+    (MALLOC_FUNCS_MALLOC | MALLOC_FUNCS_JEMALLOC | MALLOC_FUNCS_ARENA)
+
+#endif  // malloc_decls_h
+
+#ifndef MALLOC_FUNCS
+#  define MALLOC_FUNCS MALLOC_FUNCS_ALL
+#endif
+
+#ifdef MALLOC_DECL
+// NOTHROW_MALLOC_DECL is intended for functions where the standard library
+// declares the functions in question as `throw()`.  Not all platforms
+// consistent declare certain functions as `throw()`, though.
+
+// Bionic and OS X don't seem to care about `throw()`ness.
+#  if defined(ANDROID) || defined(XP_DARWIN)
+#    undef NOTHROW_MALLOC_DECL
+#    define NOTHROW_MALLOC_DECL MALLOC_DECL
+// Some places don't care about the distinction.
+#  elif !defined(NOTHROW_MALLOC_DECL)
+#    define NOTHROW_MALLOC_DECL MALLOC_DECL
+#  endif
+
+#  if MALLOC_FUNCS & MALLOC_FUNCS_MALLOC_BASE
+MALLOC_DECL(malloc, void*, size_t)
+MALLOC_DECL(calloc, void*, size_t, size_t)
+MALLOC_DECL(realloc, void*, void*, size_t)
+NOTHROW_MALLOC_DECL(free, void, void*)
+NOTHROW_MALLOC_DECL(memalign, void*, size_t, size_t)
+#  endif
+#  if MALLOC_FUNCS & MALLOC_FUNCS_MALLOC_EXTRA
+NOTHROW_MALLOC_DECL(posix_memalign, int, void**, size_t, size_t)
+NOTHROW_MALLOC_DECL(aligned_alloc, void*, size_t, size_t)
+NOTHROW_MALLOC_DECL(valloc, void*, size_t)
+NOTHROW_MALLOC_DECL(malloc_usable_size, size_t, usable_ptr_t)
+MALLOC_DECL(malloc_good_size, size_t, size_t)
+#  endif
+
+#  if MALLOC_FUNCS & MALLOC_FUNCS_JEMALLOC
+// The 2nd argument points to an optional array exactly
+// jemalloc_stats_num_bins() long to be filled in (if non-null).
+// This must only be called on the main thread.
+MALLOC_DECL(jemalloc_stats_internal, void, jemalloc_stats_t*,
+            jemalloc_bin_stats_t*)
+
+// Return the size of the jemalloc_bin_stats_t array.
+MALLOC_DECL(jemalloc_stats_num_bins, size_t)
+
+// Tell jemalloc this is the main thread. jemalloc will use this to validate
+// that main thread only arenas are only used on the main thread.
+MALLOC_DECL(jemalloc_set_main_thread, void)
+
+// On some operating systems (Mac), we use madvise(MADV_FREE) to hand pages
+// back to the operating system.  On Mac, the operating system doesn't take
+// this memory back immediately; instead, the OS takes it back only when the
+// machine is running out of physical memory.
+//
+// This is great from the standpoint of efficiency, but it makes measuring our
+// actual RSS difficult, because pages which we've MADV_FREE'd shouldn't count
+// against our RSS.
+//
+// This function explicitly purges any MADV_FREE'd pages from physical memory,
+// causing our reported RSS match the amount of memory we're actually using.
+//
+// Note that this call is expensive in two ways.  First, it may be slow to
+// execute, because it may make a number of slow syscalls to free memory.  This
+// function holds the big jemalloc locks, so basically all threads are blocked
+// while this function runs.
+//
+// This function is also expensive in that the next time we go to access a page
+// which we've just explicitly decommitted, the operating system has to attach
+// to it a physical page!  If we hadn't run this function, the OS would have
+// less work to do.
+//
+// If MALLOC_DOUBLE_PURGE is not defined, this function does nothing.
+//
+// It may only be used from the main thread.
+MALLOC_DECL(jemalloc_purge_freed_pages, void)
+
+// Free all unused dirty pages in all arenas. Calling this function will slow
+// down subsequent allocations so it is recommended to use it only when
+// memory needs to be reclaimed at all costs (see bug 805855). This function
+// provides functionality similar to mallctl("arenas.purge") in jemalloc 3.
+// It may only be used from the main thread.
+MALLOC_DECL(jemalloc_free_dirty_pages, void)
+
+// Opt in or out of a thread local arena (bool argument is whether to opt-in
+// (true) or out (false)).
+MALLOC_DECL(jemalloc_thread_local_arena, void, bool)
+
+// Provide information about any allocation enclosing the given address.
+MALLOC_DECL(jemalloc_ptr_info, void, const void*, jemalloc_ptr_info_t*)
+#  endif
+
+#  if MALLOC_FUNCS & MALLOC_FUNCS_ARENA_BASE
+
+// Creates a separate arena, and returns its id, valid to use with moz_arena_*
+// functions. A helper is provided in mozmemory.h that doesn't take any
+// arena_params_t: moz_create_arena.
+MALLOC_DECL(moz_create_arena_with_params, arena_id_t, arena_params_t*)
+
+// Dispose of the given arena. Subsequent uses of the arena will crash.
+// Passing an invalid id (inexistent or already disposed) to this function
+// will crash. The arena must be empty prior to calling this function.
+MALLOC_DECL(moz_dispose_arena, void, arena_id_t)
+
+// Set the default modifier for mMaxDirty. The value is the number of shifts
+// applied to the value. Positive value is handled as <<, negative >>.
+// Arenas may override the default modifier.
+MALLOC_DECL(moz_set_max_dirty_page_modifier, void, int32_t)
+
+#  endif
+
+#  if MALLOC_FUNCS & MALLOC_FUNCS_ARENA_ALLOC
+// Same as the functions without the moz_arena_ prefix, but using arenas
+// created with moz_create_arena.
+// The contract, even if not enforced at runtime in some configurations,
+// is that moz_arena_realloc and moz_arena_free will crash if the given
+// arena doesn't own the given pointer. All functions will crash if the
+// arena id is invalid.
+// Although discouraged, plain realloc and free can still be used on
+// pointers allocated with these functions. Realloc will properly keep
+// new pointers in the same arena as the original.
+MALLOC_DECL(moz_arena_malloc, void*, arena_id_t, size_t)
+MALLOC_DECL(moz_arena_calloc, void*, arena_id_t, size_t, size_t)
+MALLOC_DECL(moz_arena_realloc, void*, arena_id_t, void*, size_t)
+MALLOC_DECL(moz_arena_free, void, arena_id_t, void*)
+MALLOC_DECL(moz_arena_memalign, void*, arena_id_t, size_t, size_t)
+#  endif
+
+#endif  // MALLOC_DECL
+
+#undef NOTHROW_MALLOC_DECL
+#undef MALLOC_DECL
+#undef MALLOC_FUNCS
diff --git a/memory/build/moz.build b/memory/build/moz.build
new file mode 100644
index 0000000000..da67977330
--- /dev/null
+++ b/memory/build/moz.build
@@ -0,0 +1,68 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+EXPORTS += [
+    "malloc_decls.h",
+    "mozjemalloc_types.h",
+    "mozmemory.h",
+    "mozmemory_utils.h",
+    "mozmemory_wrap.h",
+    "PHC.h",
+]
+
+LIBRARY_DEFINES["MOZ_HAS_MOZGLUE"] = True
+DEFINES["MOZ_MEMORY_IMPL"] = True
+
+if CONFIG["MOZ_REPLACE_MALLOC"]:
+    EXPORTS += [
+        "replace_malloc.h",
+        "replace_malloc_bridge.h",
+    ]
+
+if CONFIG["MOZ_PHC"]:
+    DEFINES["MOZ_PHC"] = True
+    UNIFIED_SOURCES += [
+        "FdPrintf.cpp",
+        # PHC.cpp is #included in mozjemalloc.cpp
+    ]
+
+if CONFIG["MOZ_MEMORY"]:
+    UNIFIED_SOURCES += [
+        "mozjemalloc.cpp",
+        "mozmemory_wrap.cpp",
+        "Mutex.cpp",
+    ]
+else:
+    UNIFIED_SOURCES += [
+        "fallback.cpp",
+    ]
+
+if CONFIG["OS_TARGET"] == "Darwin" and (
+    CONFIG["MOZ_REPLACE_MALLOC"] or CONFIG["MOZ_MEMORY"]
+):
+    SOURCES += [
+        "zone.c",
+    ]
+
+Library("memory")
+
+if CONFIG["OS_TARGET"] == "Android" and CONFIG["CC_TYPE"] == "clang":
+    CXXFLAGS += [
+        "-Wno-tautological-pointer-compare",
+    ]
+
+if CONFIG["MOZ_BUILD_APP"] != "memory":
+    FINAL_LIBRARY = "mozglue"
+
+if CONFIG["MOZ_REPLACE_MALLOC_STATIC"]:
+    DEFINES["MOZ_REPLACE_MALLOC_STATIC"] = True
+
+DisableStlWrapping()
+
+if CONFIG["CC_TYPE"] == "clang-cl":
+    AllowCompilerWarnings()  # workaround for bug 1090497
+
+TEST_DIRS += ["test"]
diff --git a/memory/build/mozjemalloc.cpp b/memory/build/mozjemalloc.cpp
new file mode 100644
index 0000000000..7a8211747f
--- /dev/null
+++ b/memory/build/mozjemalloc.cpp
@@ -0,0 +1,5397 @@
+/* -*- 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/. */
+
+// Portions of this file were originally under the following license:
+//
+// Copyright (C) 2006-2008 Jason Evans <jasone@FreeBSD.org>.
+// All rights reserved.
+// Copyright (C) 2007-2017 Mozilla Foundation.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1. Redistributions of source code must retain the above copyright
+//    notice(s), this list of conditions and the following disclaimer as
+//    the first lines of this file unmodified other than the possible
+//    addition of one or more copyright notices.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice(s), this list of conditions and the following disclaimer in
+//    the documentation and/or other materials provided with the
+//    distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+// PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// *****************************************************************************
+//
+// This allocator implementation is designed to provide scalable performance
+// for multi-threaded programs on multi-processor systems.  The following
+// features are included for this purpose:
+//
+//   + Multiple arenas are used if there are multiple CPUs, which reduces lock
+//     contention and cache sloshing.
+//
+//   + Cache line sharing between arenas is avoided for internal data
+//     structures.
+//
+//   + Memory is managed in chunks and runs (chunks can be split into runs),
+//     rather than as individual pages.  This provides a constant-time
+//     mechanism for associating allocations with particular arenas.
+//
+// Allocation requests are rounded up to the nearest size class, and no record
+// of the original request size is maintained.  Allocations are broken into
+// categories according to size class.  Assuming runtime defaults, the size
+// classes in each category are as follows (for x86, x86_64 and Apple Silicon):
+//
+//   |=========================================================|
+//   | Category | Subcategory    |     x86 |  x86_64 | Mac ARM |
+//   |---------------------------+---------+---------+---------|
+//   | Word size                 |  32 bit |  64 bit |  64 bit |
+//   | Page size                 |    4 Kb |    4 Kb |   16 Kb |
+//   |=========================================================|
+//   | Small    | Tiny           |    4/-w |      -w |       - |
+//   |          |                |       8 |    8/-w |       8 |
+//   |          |----------------+---------|---------|---------|
+//   |          | Quantum-spaced |      16 |      16 |      16 |
+//   |          |                |      32 |      32 |      32 |
+//   |          |                |      48 |      48 |      48 |
+//   |          |                |     ... |     ... |     ... |
+//   |          |                |     480 |     480 |     480 |
+//   |          |                |     496 |     496 |     496 |
+//   |          |----------------+---------|---------|---------|
+//   |          | Quantum-wide-  |     512 |     512 |     512 |
+//   |          | spaced         |     768 |     768 |     768 |
+//   |          |                |     ... |     ... |     ... |
+//   |          |                |    3584 |    3584 |    3584 |
+//   |          |                |    3840 |    3840 |    3840 |
+//   |          |----------------+---------|---------|---------|
+//   |          | Sub-page       |       - |       - |    4096 |
+//   |          |                |       - |       - |    8 kB |
+//   |=========================================================|
+//   | Large                     |    4 kB |    4 kB |       - |
+//   |                           |    8 kB |    8 kB |       - |
+//   |                           |   12 kB |   12 kB |       - |
+//   |                           |   16 kB |   16 kB |   16 kB |
+//   |                           |     ... |     ... |       - |
+//   |                           |   32 kB |   32 kB |   32 kB |
+//   |                           |     ... |     ... |     ... |
+//   |                           | 1008 kB | 1008 kB | 1008 kB |
+//   |                           | 1012 kB | 1012 kB |       - |
+//   |                           | 1016 kB | 1016 kB |       - |
+//   |                           | 1020 kB | 1020 kB |       - |
+//   |=========================================================|
+//   | Huge                      |    1 MB |    1 MB |    1 MB |
+//   |                           |    2 MB |    2 MB |    2 MB |
+//   |                           |    3 MB |    3 MB |    3 MB |
+//   |                           |     ... |     ... |     ... |
+//   |=========================================================|
+//
+// Legend:
+//   n:    Size class exists for this platform.
+//   n/-w: This size class doesn't exist on Windows (see kMinTinyClass).
+//   -:    This size class doesn't exist for this platform.
+//   ...:  Size classes follow a pattern here.
+//
+// NOTE: Due to Mozilla bug 691003, we cannot reserve less than one word for an
+// allocation on Linux or Mac.  So on 32-bit *nix, the smallest bucket size is
+// 4 bytes, and on 64-bit, the smallest bucket size is 8 bytes.
+//
+// A different mechanism is used for each category:
+//
+//   Small : Each size class is segregated into its own set of runs.  Each run
+//           maintains a bitmap of which regions are free/allocated.
+//
+//   Large : Each allocation is backed by a dedicated run.  Metadata are stored
+//           in the associated arena chunk header maps.
+//
+//   Huge : Each allocation is backed by a dedicated contiguous set of chunks.
+//          Metadata are stored in a separate red-black tree.
+//
+// *****************************************************************************
+
+#include "mozmemory_wrap.h"
+#include "mozjemalloc.h"
+#include "mozjemalloc_types.h"
+
+#include <cstring>
+#include <cerrno>
+#include <optional>
+#include <type_traits>
+#ifdef XP_WIN
+#  include <io.h>
+#  include <windows.h>
+#else
+#  include <sys/mman.h>
+#  include <unistd.h>
+#endif
+#ifdef XP_DARWIN
+#  include <libkern/OSAtomic.h>
+#  include <mach/mach_init.h>
+#  include <mach/vm_map.h>
+#endif
+
+#include "mozilla/Atomics.h"
+#include "mozilla/Alignment.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/DoublyLinkedList.h"
+#include "mozilla/HelperMacros.h"
+#include "mozilla/Likely.h"
+#include "mozilla/Literals.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/RandomNum.h"
+// Note: MozTaggedAnonymousMmap() could call an LD_PRELOADed mmap
+// instead of the one defined here; use only MozTagAnonymousMemory().
+#include "mozilla/TaggedAnonymousMemory.h"
+#include "mozilla/ThreadLocal.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/XorShift128PlusRNG.h"
+#include "mozilla/fallible.h"
+#include "rb.h"
+#include "Mutex.h"
+#include "PHC.h"
+#include "Utils.h"
+
+#if defined(XP_WIN)
+#  include "mozmemory_utils.h"
+#endif
+
+// For GetGeckoProcessType(), when it's used.
+#if defined(XP_WIN) && !defined(JS_STANDALONE)
+#  include "mozilla/ProcessType.h"
+#endif
+
+using namespace mozilla;
+
+// On Linux, we use madvise(MADV_DONTNEED) to release memory back to the
+// operating system.  If we release 1MB of live pages with MADV_DONTNEED, our
+// RSS will decrease by 1MB (almost) immediately.
+//
+// On Mac, we use madvise(MADV_FREE).  Unlike MADV_DONTNEED on Linux, MADV_FREE
+// on Mac doesn't cause the OS to release the specified pages immediately; the
+// OS keeps them in our process until the machine comes under memory pressure.
+//
+// It's therefore difficult to measure the process's RSS on Mac, since, in the
+// absence of memory pressure, the contribution from the heap to RSS will not
+// decrease due to our madvise calls.
+//
+// We therefore define MALLOC_DOUBLE_PURGE on Mac.  This causes jemalloc to
+// track which pages have been MADV_FREE'd.  You can then call
+// jemalloc_purge_freed_pages(), which will force the OS to release those
+// MADV_FREE'd pages, making the process's RSS reflect its true memory usage.
+//
+// The jemalloc_purge_freed_pages definition in memory/build/mozmemory.h needs
+// to be adjusted if MALLOC_DOUBLE_PURGE is ever enabled on Linux.
+
+#ifdef XP_DARWIN
+#  define MALLOC_DOUBLE_PURGE
+#endif
+
+#ifdef XP_WIN
+#  define MALLOC_DECOMMIT
+#endif
+
+// Define MALLOC_RUNTIME_CONFIG depending on MOZ_DEBUG. Overriding this as
+// a build option allows us to build mozjemalloc/firefox without runtime asserts
+// but with runtime configuration. Making some testing easier.
+
+#ifdef MOZ_DEBUG
+#  define MALLOC_RUNTIME_CONFIG
+#endif
+
+// When MALLOC_STATIC_PAGESIZE is defined, the page size is fixed at
+// compile-time for better performance, as opposed to determined at
+// runtime. Some platforms can have different page sizes at runtime
+// depending on kernel configuration, so they are opted out by default.
+// Debug builds are opted out too, for test coverage.
+#ifndef MALLOC_RUNTIME_CONFIG
+#  if !defined(__ia64__) && !defined(__sparc__) && !defined(__mips__) &&       \
+      !defined(__aarch64__) && !defined(__powerpc__) && !defined(XP_MACOSX) && \
+      !defined(__loongarch__)
+#    define MALLOC_STATIC_PAGESIZE 1
+#  endif
+#endif
+
+#ifdef XP_WIN
+#  define STDERR_FILENO 2
+
+// Implement getenv without using malloc.
+static char mozillaMallocOptionsBuf[64];
+
+#  define getenv xgetenv
+static char* getenv(const char* name) {
+  if (GetEnvironmentVariableA(name, mozillaMallocOptionsBuf,
+                              sizeof(mozillaMallocOptionsBuf)) > 0) {
+    return mozillaMallocOptionsBuf;
+  }
+
+  return nullptr;
+}
+#endif
+
+#ifndef XP_WIN
+// Newer Linux systems support MADV_FREE, but we're not supporting
+// that properly. bug #1406304.
+#  if defined(XP_LINUX) && defined(MADV_FREE)
+#    undef MADV_FREE
+#  endif
+#  ifndef MADV_FREE
+#    define MADV_FREE MADV_DONTNEED
+#  endif
+#endif
+
+// Some tools, such as /dev/dsp wrappers, LD_PRELOAD libraries that
+// happen to override mmap() and call dlsym() from their overridden
+// mmap(). The problem is that dlsym() calls malloc(), and this ends
+// up in a dead lock in jemalloc.
+// On these systems, we prefer to directly use the system call.
+// We do that for Linux systems and kfreebsd with GNU userland.
+// Note sanity checks are not done (alignment of offset, ...) because
+// the uses of mmap are pretty limited, in jemalloc.
+//
+// On Alpha, glibc has a bug that prevents syscall() to work for system
+// calls with 6 arguments.
+#if (defined(XP_LINUX) && !defined(__alpha__)) || \
+    (defined(__FreeBSD_kernel__) && defined(__GLIBC__))
+#  include <sys/syscall.h>
+#  if defined(SYS_mmap) || defined(SYS_mmap2)
+static inline void* _mmap(void* addr, size_t length, int prot, int flags,
+                          int fd, off_t offset) {
+// S390 only passes one argument to the mmap system call, which is a
+// pointer to a structure containing the arguments.
+#    ifdef __s390__
+  struct {
+    void* addr;
+    size_t length;
+    long prot;
+    long flags;
+    long fd;
+    off_t offset;
+  } args = {addr, length, prot, flags, fd, offset};
+  return (void*)syscall(SYS_mmap, &args);
+#    else
+#      if defined(ANDROID) && defined(__aarch64__) && defined(SYS_mmap2)
+  // Android NDK defines SYS_mmap2 for AArch64 despite it not supporting mmap2.
+#        undef SYS_mmap2
+#      endif
+#      ifdef SYS_mmap2
+  return (void*)syscall(SYS_mmap2, addr, length, prot, flags, fd, offset >> 12);
+#      else
+  return (void*)syscall(SYS_mmap, addr, length, prot, flags, fd, offset);
+#      endif
+#    endif
+}
+#    define mmap _mmap
+#    define munmap(a, l) syscall(SYS_munmap, a, l)
+#  endif
+#endif
+
+// ***************************************************************************
+// Structures for chunk headers for chunks used for non-huge allocations.
+
+struct arena_t;
+
+// Each element of the chunk map corresponds to one page within the chunk.
+struct arena_chunk_map_t {
+  // Linkage for run trees.  There are two disjoint uses:
+  //
+  // 1) arena_t's tree or available runs.
+  // 2) arena_run_t conceptually uses this linkage for in-use non-full
+  //    runs, rather than directly embedding linkage.
+  RedBlackTreeNode<arena_chunk_map_t> link;
+
+  // Run address (or size) and various flags are stored together.  The bit
+  // layout looks like (assuming 32-bit system):
+  //
+  //   ???????? ???????? ????---- -mckdzla
+  //
+  // ? : Unallocated: Run address for first/last pages, unset for internal
+  //                  pages.
+  //     Small: Run address.
+  //     Large: Run size for first page, unset for trailing pages.
+  // - : Unused.
+  // m : MADV_FREE/MADV_DONTNEED'ed?
+  // c : decommitted?
+  // k : key?
+  // d : dirty?
+  // z : zeroed?
+  // l : large?
+  // a : allocated?
+  //
+  // Following are example bit patterns for the three types of runs.
+  //
+  // r : run address
+  // s : run size
+  // x : don't care
+  // - : 0
+  // [cdzla] : bit set
+  //
+  //   Unallocated:
+  //     ssssssss ssssssss ssss---- --c-----
+  //     xxxxxxxx xxxxxxxx xxxx---- ----d---
+  //     ssssssss ssssssss ssss---- -----z--
+  //
+  //   Small:
+  //     rrrrrrrr rrrrrrrr rrrr---- -------a
+  //     rrrrrrrr rrrrrrrr rrrr---- -------a
+  //     rrrrrrrr rrrrrrrr rrrr---- -------a
+  //
+  //   Large:
+  //     ssssssss ssssssss ssss---- ------la
+  //     -------- -------- -------- ------la
+  //     -------- -------- -------- ------la
+  size_t bits;
+
+// Note that CHUNK_MAP_DECOMMITTED's meaning varies depending on whether
+// MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are defined.
+//
+// If MALLOC_DECOMMIT is defined, a page which is CHUNK_MAP_DECOMMITTED must be
+// re-committed with pages_commit() before it may be touched.  If
+// MALLOC_DECOMMIT is defined, MALLOC_DOUBLE_PURGE may not be defined.
+//
+// If neither MALLOC_DECOMMIT nor MALLOC_DOUBLE_PURGE is defined, pages which
+// are madvised (with either MADV_DONTNEED or MADV_FREE) are marked with
+// CHUNK_MAP_MADVISED.
+//
+// Otherwise, if MALLOC_DECOMMIT is not defined and MALLOC_DOUBLE_PURGE is
+// defined, then a page which is madvised is marked as CHUNK_MAP_MADVISED.
+// When it's finally freed with jemalloc_purge_freed_pages, the page is marked
+// as CHUNK_MAP_DECOMMITTED.
+#define CHUNK_MAP_MADVISED ((size_t)0x40U)
+#define CHUNK_MAP_DECOMMITTED ((size_t)0x20U)
+#define CHUNK_MAP_MADVISED_OR_DECOMMITTED \
+  (CHUNK_MAP_MADVISED | CHUNK_MAP_DECOMMITTED)
+#define CHUNK_MAP_KEY ((size_t)0x10U)
+#define CHUNK_MAP_DIRTY ((size_t)0x08U)
+#define CHUNK_MAP_ZEROED ((size_t)0x04U)
+#define CHUNK_MAP_LARGE ((size_t)0x02U)
+#define CHUNK_MAP_ALLOCATED ((size_t)0x01U)
+};
+
+// Arena chunk header.
+struct arena_chunk_t {
+  // Arena that owns the chunk.
+  arena_t* arena;
+
+  // Linkage for the arena's tree of dirty chunks.
+  RedBlackTreeNode<arena_chunk_t> link_dirty;
+
+#ifdef MALLOC_DOUBLE_PURGE
+  // If we're double-purging, we maintain a linked list of chunks which
+  // have pages which have been madvise(MADV_FREE)'d but not explicitly
+  // purged.
+  //
+  // We're currently lazy and don't remove a chunk from this list when
+  // all its madvised pages are recommitted.
+  DoublyLinkedListElement<arena_chunk_t> chunks_madvised_elem;
+#endif
+
+  // Number of dirty pages.
+  size_t ndirty;
+
+  // Map of pages within chunk that keeps track of free/large/small.
+  arena_chunk_map_t map[1];  // Dynamically sized.
+};
+
+// ***************************************************************************
+// Constants defining allocator size classes and behavior.
+
+// Maximum size of L1 cache line.  This is used to avoid cache line aliasing,
+// so over-estimates are okay (up to a point), but under-estimates will
+// negatively affect performance.
+static const size_t kCacheLineSize = 64;
+
+// Our size classes are inclusive ranges of memory sizes.  By describing the
+// minimums and how memory is allocated in each range the maximums can be
+// calculated.
+
+// Smallest size class to support.  On Windows the smallest allocation size
+// must be 8 bytes on 32-bit, 16 bytes on 64-bit.  On Linux and Mac, even
+// malloc(1) must reserve a word's worth of memory (see Mozilla bug 691003).
+#ifdef XP_WIN
+static const size_t kMinTinyClass = sizeof(void*) * 2;
+#else
+static const size_t kMinTinyClass = sizeof(void*);
+#endif
+
+// Maximum tiny size class.
+static const size_t kMaxTinyClass = 8;
+
+// Smallest quantum-spaced size classes. It could actually also be labelled a
+// tiny allocation, and is spaced as such from the largest tiny size class.
+// Tiny classes being powers of 2, this is twice as large as the largest of
+// them.
+static const size_t kMinQuantumClass = kMaxTinyClass * 2;
+static const size_t kMinQuantumWideClass = 512;
+static const size_t kMinSubPageClass = 4_KiB;
+
+// Amount (quantum) separating quantum-spaced size classes.
+static const size_t kQuantum = 16;
+static const size_t kQuantumMask = kQuantum - 1;
+static const size_t kQuantumWide = 256;
+static const size_t kQuantumWideMask = kQuantumWide - 1;
+
+static const size_t kMaxQuantumClass = kMinQuantumWideClass - kQuantum;
+static const size_t kMaxQuantumWideClass = kMinSubPageClass - kQuantumWide;
+
+// We can optimise some divisions to shifts if these are powers of two.
+static_assert(mozilla::IsPowerOfTwo(kQuantum),
+              "kQuantum is not a power of two");
+static_assert(mozilla::IsPowerOfTwo(kQuantumWide),
+              "kQuantumWide is not a power of two");
+
+static_assert(kMaxQuantumClass % kQuantum == 0,
+              "kMaxQuantumClass is not a multiple of kQuantum");
+static_assert(kMaxQuantumWideClass % kQuantumWide == 0,
+              "kMaxQuantumWideClass is not a multiple of kQuantumWide");
+static_assert(kQuantum < kQuantumWide,
+              "kQuantum must be smaller than kQuantumWide");
+static_assert(mozilla::IsPowerOfTwo(kMinSubPageClass),
+              "kMinSubPageClass is not a power of two");
+
+// Number of (2^n)-spaced tiny classes.
+static const size_t kNumTinyClasses =
+    LOG2(kMaxTinyClass) - LOG2(kMinTinyClass) + 1;
+
+// Number of quantum-spaced classes.  We add kQuantum(Max) before subtracting to
+// avoid underflow when a class is empty (Max<Min).
+static const size_t kNumQuantumClasses =
+    (kMaxQuantumClass + kQuantum - kMinQuantumClass) / kQuantum;
+static const size_t kNumQuantumWideClasses =
+    (kMaxQuantumWideClass + kQuantumWide - kMinQuantumWideClass) / kQuantumWide;
+
+// Size and alignment of memory chunks that are allocated by the OS's virtual
+// memory system.
+static const size_t kChunkSize = 1_MiB;
+static const size_t kChunkSizeMask = kChunkSize - 1;
+
+#ifdef MALLOC_STATIC_PAGESIZE
+// VM page size. It must divide the runtime CPU page size or the code
+// will abort.
+// Platform specific page size conditions copied from js/public/HeapAPI.h
+#  if defined(__powerpc64__)
+static const size_t gPageSize = 64_KiB;
+#  elif defined(__loongarch64)
+static const size_t gPageSize = 16_KiB;
+#  else
+static const size_t gPageSize = 4_KiB;
+#  endif
+static const size_t gRealPageSize = gPageSize;
+
+#else
+// When MALLOC_OPTIONS contains one or several `P`s, the page size used
+// across the allocator is multiplied by 2 for each `P`, but we also keep
+// the real page size for code paths that need it. gPageSize is thus a
+// power of two greater or equal to gRealPageSize.
+static size_t gRealPageSize;
+static size_t gPageSize;
+#endif
+
+#ifdef MALLOC_STATIC_PAGESIZE
+#  define DECLARE_GLOBAL(type, name)
+#  define DEFINE_GLOBALS
+#  define END_GLOBALS
+#  define DEFINE_GLOBAL(type) static const type
+#  define GLOBAL_LOG2 LOG2
+#  define GLOBAL_ASSERT_HELPER1(x) static_assert(x, #x)
+#  define GLOBAL_ASSERT_HELPER2(x, y) static_assert(x, y)
+#  define GLOBAL_ASSERT(...)                                               \
+    MACRO_CALL(                                                            \
+        MOZ_PASTE_PREFIX_AND_ARG_COUNT(GLOBAL_ASSERT_HELPER, __VA_ARGS__), \
+        (__VA_ARGS__))
+#  define GLOBAL_CONSTEXPR constexpr
+#else
+#  define DECLARE_GLOBAL(type, name) static type name;
+#  define DEFINE_GLOBALS static void DefineGlobals() {
+#  define END_GLOBALS }
+#  define DEFINE_GLOBAL(type)
+#  define GLOBAL_LOG2 FloorLog2
+#  define GLOBAL_ASSERT MOZ_RELEASE_ASSERT
+#  define GLOBAL_CONSTEXPR
+#endif
+
+DECLARE_GLOBAL(size_t, gMaxSubPageClass)
+DECLARE_GLOBAL(uint8_t, gNumSubPageClasses)
+DECLARE_GLOBAL(uint8_t, gPageSize2Pow)
+DECLARE_GLOBAL(size_t, gPageSizeMask)
+DECLARE_GLOBAL(size_t, gChunkNumPages)
+DECLARE_GLOBAL(size_t, gChunkHeaderNumPages)
+DECLARE_GLOBAL(size_t, gMaxLargeClass)
+
+DEFINE_GLOBALS
+
+// Largest sub-page size class, or zero if there are none
+DEFINE_GLOBAL(size_t)
+gMaxSubPageClass = gPageSize / 2 >= kMinSubPageClass ? gPageSize / 2 : 0;
+
+// Max size class for bins.
+#define gMaxBinClass \
+  (gMaxSubPageClass ? gMaxSubPageClass : kMaxQuantumWideClass)
+
+// Number of sub-page bins.
+DEFINE_GLOBAL(uint8_t)
+gNumSubPageClasses = []() GLOBAL_CONSTEXPR -> uint8_t {
+  if GLOBAL_CONSTEXPR (gMaxSubPageClass != 0) {
+    return FloorLog2(gMaxSubPageClass) - LOG2(kMinSubPageClass) + 1;
+  }
+  return 0;
+}();
+
+DEFINE_GLOBAL(uint8_t) gPageSize2Pow = GLOBAL_LOG2(gPageSize);
+DEFINE_GLOBAL(size_t) gPageSizeMask = gPageSize - 1;
+
+// Number of pages in a chunk.
+DEFINE_GLOBAL(size_t) gChunkNumPages = kChunkSize >> gPageSize2Pow;
+
+// Number of pages necessary for a chunk header plus a guard page.
+DEFINE_GLOBAL(size_t)
+gChunkHeaderNumPages =
+    1 + (((sizeof(arena_chunk_t) +
+           sizeof(arena_chunk_map_t) * (gChunkNumPages - 1) + gPageSizeMask) &
+          ~gPageSizeMask) >>
+         gPageSize2Pow);
+
+// One chunk, minus the header, minus a guard page
+DEFINE_GLOBAL(size_t)
+gMaxLargeClass =
+    kChunkSize - gPageSize - (gChunkHeaderNumPages << gPageSize2Pow);
+
+// Various sanity checks that regard configuration.
+GLOBAL_ASSERT(1ULL << gPageSize2Pow == gPageSize,
+              "Page size is not a power of two");
+GLOBAL_ASSERT(kQuantum >= sizeof(void*));
+GLOBAL_ASSERT(kQuantum <= kQuantumWide);
+GLOBAL_ASSERT(!kNumQuantumWideClasses ||
+              kQuantumWide <= (kMinSubPageClass - kMaxQuantumClass));
+
+GLOBAL_ASSERT(kQuantumWide <= kMaxQuantumClass);
+
+GLOBAL_ASSERT(gMaxSubPageClass >= kMinSubPageClass || gMaxSubPageClass == 0);
+GLOBAL_ASSERT(gMaxLargeClass >= gMaxSubPageClass);
+GLOBAL_ASSERT(kChunkSize >= gPageSize);
+GLOBAL_ASSERT(kQuantum * 4 <= kChunkSize);
+
+END_GLOBALS
+
+// Recycle at most 128 MiB of chunks. This means we retain at most
+// 6.25% of the process address space on a 32-bit OS for later use.
+static const size_t gRecycleLimit = 128_MiB;
+
+// The current amount of recycled bytes, updated atomically.
+static Atomic<size_t, ReleaseAcquire> gRecycledSize;
+
+// Maximum number of dirty pages per arena.
+#define DIRTY_MAX_DEFAULT (1U << 8)
+
+static size_t opt_dirty_max = DIRTY_MAX_DEFAULT;
+
+// Return the smallest chunk multiple that is >= s.
+#define CHUNK_CEILING(s) (((s) + kChunkSizeMask) & ~kChunkSizeMask)
+
+// Return the smallest cacheline multiple that is >= s.
+#define CACHELINE_CEILING(s) \
+  (((s) + (kCacheLineSize - 1)) & ~(kCacheLineSize - 1))
+
+// Return the smallest quantum multiple that is >= a.
+#define QUANTUM_CEILING(a) (((a) + (kQuantumMask)) & ~(kQuantumMask))
+#define QUANTUM_WIDE_CEILING(a) \
+  (((a) + (kQuantumWideMask)) & ~(kQuantumWideMask))
+
+// Return the smallest sub page-size  that is >= a.
+#define SUBPAGE_CEILING(a) (RoundUpPow2(a))
+
+// Return the smallest pagesize multiple that is >= s.
+#define PAGE_CEILING(s) (((s) + gPageSizeMask) & ~gPageSizeMask)
+
+// Number of all the small-allocated classes
+#define NUM_SMALL_CLASSES                                          \
+  (kNumTinyClasses + kNumQuantumClasses + kNumQuantumWideClasses + \
+   gNumSubPageClasses)
+
+// ***************************************************************************
+// MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are mutually exclusive.
+#if defined(MALLOC_DECOMMIT) && defined(MALLOC_DOUBLE_PURGE)
+#  error MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are mutually exclusive.
+#endif
+
+static void* base_alloc(size_t aSize);
+
+// Set to true once the allocator has been initialized.
+#if defined(_MSC_VER) && !defined(__clang__)
+// MSVC may create a static initializer for an Atomic<bool>, which may actually
+// run after `malloc_init` has been called once, which triggers multiple
+// initializations.
+// We work around the problem by not using an Atomic<bool> at all. There is a
+// theoretical problem with using `malloc_initialized` non-atomically, but
+// practically, this is only true if `malloc_init` is never called before
+// threads are created.
+static bool malloc_initialized;
+#else
+static Atomic<bool, MemoryOrdering::ReleaseAcquire> malloc_initialized;
+#endif
+
+static StaticMutex gInitLock MOZ_UNANNOTATED = {STATIC_MUTEX_INIT};
+
+// ***************************************************************************
+// Statistics data structures.
+
+struct arena_stats_t {
+  // Number of bytes currently mapped.
+  size_t mapped;
+
+  // Current number of committed pages.
+  size_t committed;
+
+  // Per-size-category statistics.
+  size_t allocated_small;
+
+  size_t allocated_large;
+};
+
+// ***************************************************************************
+// Extent data structures.
+
+enum ChunkType {
+  UNKNOWN_CHUNK,
+  ZEROED_CHUNK,    // chunk only contains zeroes.
+  ARENA_CHUNK,     // used to back arena runs created by arena_t::AllocRun.
+  HUGE_CHUNK,      // used to back huge allocations (e.g. arena_t::MallocHuge).
+  RECYCLED_CHUNK,  // chunk has been stored for future use by chunk_recycle.
+};
+
+// Tree of extents.
+struct extent_node_t {
+  union {
+    // Linkage for the size/address-ordered tree for chunk recycling.
+    RedBlackTreeNode<extent_node_t> mLinkBySize;
+    // Arena id for huge allocations. It's meant to match mArena->mId,
+    // which only holds true when the arena hasn't been disposed of.
+    arena_id_t mArenaId;
+  };
+
+  // Linkage for the address-ordered tree.
+  RedBlackTreeNode<extent_node_t> mLinkByAddr;
+
+  // Pointer to the extent that this tree node is responsible for.
+  void* mAddr;
+
+  // Total region size.
+  size_t mSize;
+
+  union {
+    // What type of chunk is there; used for chunk recycling.
+    ChunkType mChunkType;
+
+    // A pointer to the associated arena, for huge allocations.
+    arena_t* mArena;
+  };
+};
+
+struct ExtentTreeSzTrait {
+  static RedBlackTreeNode<extent_node_t>& GetTreeNode(extent_node_t* aThis) {
+    return aThis->mLinkBySize;
+  }
+
+  static inline Order Compare(extent_node_t* aNode, extent_node_t* aOther) {
+    Order ret = CompareInt(aNode->mSize, aOther->mSize);
+    return (ret != Order::eEqual) ? ret
+                                  : CompareAddr(aNode->mAddr, aOther->mAddr);
+  }
+};
+
+struct ExtentTreeTrait {
+  static RedBlackTreeNode<extent_node_t>& GetTreeNode(extent_node_t* aThis) {
+    return aThis->mLinkByAddr;
+  }
+
+  static inline Order Compare(extent_node_t* aNode, extent_node_t* aOther) {
+    return CompareAddr(aNode->mAddr, aOther->mAddr);
+  }
+};
+
+struct ExtentTreeBoundsTrait : public ExtentTreeTrait {
+  static inline Order Compare(extent_node_t* aKey, extent_node_t* aNode) {
+    uintptr_t key_addr = reinterpret_cast<uintptr_t>(aKey->mAddr);
+    uintptr_t node_addr = reinterpret_cast<uintptr_t>(aNode->mAddr);
+    size_t node_size = aNode->mSize;
+
+    // Is aKey within aNode?
+    if (node_addr <= key_addr && key_addr < node_addr + node_size) {
+      return Order::eEqual;
+    }
+
+    return CompareAddr(aKey->mAddr, aNode->mAddr);
+  }
+};
+
+// Describe size classes to which allocations are rounded up to.
+// TODO: add large and huge types when the arena allocation code
+// changes in a way that allows it to be beneficial.
+class SizeClass {
+ public:
+  enum ClassType {
+    Tiny,
+    Quantum,
+    QuantumWide,
+    SubPage,
+    Large,
+  };
+
+  explicit inline SizeClass(size_t aSize) {
+    if (aSize <= kMaxTinyClass) {
+      mType = Tiny;
+      mSize = std::max(RoundUpPow2(aSize), kMinTinyClass);
+    } else if (aSize <= kMaxQuantumClass) {
+      mType = Quantum;
+      mSize = QUANTUM_CEILING(aSize);
+    } else if (aSize <= kMaxQuantumWideClass) {
+      mType = QuantumWide;
+      mSize = QUANTUM_WIDE_CEILING(aSize);
+    } else if (aSize <= gMaxSubPageClass) {
+      mType = SubPage;
+      mSize = SUBPAGE_CEILING(aSize);
+    } else if (aSize <= gMaxLargeClass) {
+      mType = Large;
+      mSize = PAGE_CEILING(aSize);
+    } else {
+      MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Invalid size");
+    }
+  }
+
+  SizeClass& operator=(const SizeClass& aOther) = default;
+
+  bool operator==(const SizeClass& aOther) { return aOther.mSize == mSize; }
+
+  size_t Size() { return mSize; }
+
+  ClassType Type() { return mType; }
+
+  SizeClass Next() { return SizeClass(mSize + 1); }
+
+ private:
+  ClassType mType;
+  size_t mSize;
+};
+
+// Fast division
+//
+// During deallocation we want to divide by the size class.  This class
+// provides a routine and sets up a constant as follows.
+//
+// To divide by a number D that is not a power of two we multiply by (2^17 /
+// D) and then right shift by 17 positions.
+//
+//   X / D
+//
+// becomes
+//
+//   (X * m) >> p
+//
+// Where m is calculated during the FastDivisor constructor similarly to:
+//
+//   m = 2^p / D
+//
+template <typename T>
+class FastDivisor {
+ private:
+  // The shift amount (p) is chosen to minimise the size of m while
+  // working for divisors up to 65536 in steps of 16.  I arrived at 17
+  // experimentally.  I wanted a low number to minimise the range of m
+  // so it can fit in a uint16_t, 16 didn't work but 17 worked perfectly.
+  //
+  // We'd need to increase this if we allocated memory on smaller boundaries
+  // than 16.
+  static const unsigned p = 17;
+
+  // We can fit the inverted divisor in 16 bits, but we template it here for
+  // convenience.
+  T m;
+
+ public:
+  // Needed so mBins can be constructed.
+  FastDivisor() : m(0) {}
+
+  FastDivisor(unsigned div, unsigned max) {
+    MOZ_ASSERT(div <= max);
+
+    // divide_inv_shift is large enough.
+    MOZ_ASSERT((1U << p) >= div);
+
+    // The calculation here for m is formula 26 from Section
+    // 10-9 "Unsigned Division by Divisors >= 1" in
+    // Henry S. Warren, Jr.'s Hacker's Delight, 2nd Ed.
+    unsigned m_ = ((1U << p) + div - 1 - (((1U << p) - 1) % div)) / div;
+
+    // Make sure that max * m does not overflow.
+    MOZ_DIAGNOSTIC_ASSERT(max < UINT_MAX / m_);
+
+    MOZ_ASSERT(m_ <= std::numeric_limits<T>::max());
+    m = static_cast<T>(m_);
+
+    // Initialisation made m non-zero.
+    MOZ_ASSERT(m);
+
+    // Test that all the divisions in the range we expected would work.
+#ifdef MOZ_DEBUG
+    for (unsigned num = 0; num < max; num += div) {
+      MOZ_ASSERT(num / div == divide(num));
+    }
+#endif
+  }
+
+  // Note that this always occurs in uint32_t regardless of m's type.  If m is
+  // a uint16_t it will be zero-extended before the multiplication.  We also use
+  // uint32_t rather than something that could possibly be larger because it is
+  // most-likely the cheapest multiplication.
+  inline uint32_t divide(uint32_t num) const {
+    // Check that m was initialised.
+    MOZ_ASSERT(m);
+    return (num * m) >> p;
+  }
+};
+
+template <typename T>
+unsigned inline operator/(unsigned num, FastDivisor<T> divisor) {
+  return divisor.divide(num);
+}
+
+// ***************************************************************************
+// Radix tree data structures.
+//
+// The number of bits passed to the template is the number of significant bits
+// in an address to do a radix lookup with.
+//
+// An address is looked up by splitting it in kBitsPerLevel bit chunks, except
+// the most significant bits, where the bit chunk is kBitsAtLevel1 which can be
+// different if Bits is not a multiple of kBitsPerLevel.
+//
+// With e.g. sizeof(void*)=4, Bits=16 and kBitsPerLevel=8, an address is split
+// like the following:
+// 0x12345678 -> mRoot[0x12][0x34]
+template <size_t Bits>
+class AddressRadixTree {
+// Size of each radix tree node (as a power of 2).
+// This impacts tree depth.
+#ifdef HAVE_64BIT_BUILD
+  static const size_t kNodeSize = kCacheLineSize;
+#else
+  static const size_t kNodeSize = 16_KiB;
+#endif
+  static const size_t kBitsPerLevel = LOG2(kNodeSize) - LOG2(sizeof(void*));
+  static const size_t kBitsAtLevel1 =
+      (Bits % kBitsPerLevel) ? Bits % kBitsPerLevel : kBitsPerLevel;
+  static const size_t kHeight = (Bits + kBitsPerLevel - 1) / kBitsPerLevel;
+  static_assert(kBitsAtLevel1 + (kHeight - 1) * kBitsPerLevel == Bits,
+                "AddressRadixTree parameters don't work out");
+
+  Mutex mLock MOZ_UNANNOTATED;
+  void** mRoot;
+
+ public:
+  bool Init();
+
+  inline void* Get(void* aAddr);
+
+  // Returns whether the value was properly set.
+  inline bool Set(void* aAddr, void* aValue);
+
+  inline bool Unset(void* aAddr) { return Set(aAddr, nullptr); }
+
+ private:
+  inline void** GetSlot(void* aAddr, bool aCreate = false);
+};
+
+// ***************************************************************************
+// Arena data structures.
+
+struct arena_bin_t;
+
+struct ArenaChunkMapLink {
+  static RedBlackTreeNode<arena_chunk_map_t>& GetTreeNode(
+      arena_chunk_map_t* aThis) {
+    return aThis->link;
+  }
+};
+
+struct ArenaRunTreeTrait : public ArenaChunkMapLink {
+  static inline Order Compare(arena_chunk_map_t* aNode,
+                              arena_chunk_map_t* aOther) {
+    MOZ_ASSERT(aNode);
+    MOZ_ASSERT(aOther);
+    return CompareAddr(aNode, aOther);
+  }
+};
+
+struct ArenaAvailTreeTrait : public ArenaChunkMapLink {
+  static inline Order Compare(arena_chunk_map_t* aNode,
+                              arena_chunk_map_t* aOther) {
+    size_t size1 = aNode->bits & ~gPageSizeMask;
+    size_t size2 = aOther->bits & ~gPageSizeMask;
+    Order ret = CompareInt(size1, size2);
+    return (ret != Order::eEqual)
+               ? ret
+               : CompareAddr((aNode->bits & CHUNK_MAP_KEY) ? nullptr : aNode,
+                             aOther);
+  }
+};
+
+struct ArenaDirtyChunkTrait {
+  static RedBlackTreeNode<arena_chunk_t>& GetTreeNode(arena_chunk_t* aThis) {
+    return aThis->link_dirty;
+  }
+
+  static inline Order Compare(arena_chunk_t* aNode, arena_chunk_t* aOther) {
+    MOZ_ASSERT(aNode);
+    MOZ_ASSERT(aOther);
+    return CompareAddr(aNode, aOther);
+  }
+};
+
+#ifdef MALLOC_DOUBLE_PURGE
+namespace mozilla {
+
+template <>
+struct GetDoublyLinkedListElement<arena_chunk_t> {
+  static DoublyLinkedListElement<arena_chunk_t>& Get(arena_chunk_t* aThis) {
+    return aThis->chunks_madvised_elem;
+  }
+};
+}  // namespace mozilla
+#endif
+
+struct arena_run_t {
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+  uint32_t mMagic;
+#  define ARENA_RUN_MAGIC 0x384adf93
+
+  // On 64-bit platforms, having the arena_bin_t pointer following
+  // the mMagic field means there's padding between both fields, making
+  // the run header larger than necessary.
+  // But when MOZ_DIAGNOSTIC_ASSERT_ENABLED is not set, starting the
+  // header with this field followed by the arena_bin_t pointer yields
+  // the same padding. We do want the mMagic field to appear first, so
+  // depending whether MOZ_DIAGNOSTIC_ASSERT_ENABLED is set or not, we
+  // move some field to avoid padding.
+
+  // Number of free regions in run.
+  unsigned mNumFree;
+#endif
+
+  // Bin this run is associated with.
+  arena_bin_t* mBin;
+
+  // Index of first element that might have a free region.
+  unsigned mRegionsMinElement;
+
+#if !defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+  // Number of free regions in run.
+  unsigned mNumFree;
+#endif
+
+  // Bitmask of in-use regions (0: in use, 1: free).
+  unsigned mRegionsMask[1];  // Dynamically sized.
+};
+
+struct arena_bin_t {
+  // Current run being used to service allocations of this bin's size
+  // class.
+  arena_run_t* mCurrentRun;
+
+  // Tree of non-full runs.  This tree is used when looking for an
+  // existing run when mCurrentRun is no longer usable.  We choose the
+  // non-full run that is lowest in memory; this policy tends to keep
+  // objects packed well, and it can also help reduce the number of
+  // almost-empty chunks.
+  RedBlackTree<arena_chunk_map_t, ArenaRunTreeTrait> mNonFullRuns;
+
+  // Bin's size class.
+  size_t mSizeClass;
+
+  // Total number of regions in a run for this bin's size class.
+  uint32_t mRunNumRegions;
+
+  // Number of elements in a run's mRegionsMask for this bin's size class.
+  uint32_t mRunNumRegionsMask;
+
+  // Offset of first region in a run for this bin's size class.
+  uint32_t mRunFirstRegionOffset;
+
+  // Current number of runs in this bin, full or otherwise.
+  uint32_t mNumRuns;
+
+  // A constant for fast division by size class.  This value is 16 bits wide so
+  // it is placed last.
+  FastDivisor<uint16_t> mSizeDivisor;
+
+  // Total number of pages in a run for this bin's size class.
+  uint8_t mRunSizePages;
+
+  // Amount of overhead runs are allowed to have.
+  static constexpr double kRunOverhead = 1.6_percent;
+  static constexpr double kRunRelaxedOverhead = 2.4_percent;
+
+  // Initialize a bin for the given size class.
+  // The generated run sizes, for a page size of 4 KiB, are:
+  //   size|run       size|run       size|run       size|run
+  //  class|size     class|size     class|size     class|size
+  //     4   4 KiB      8   4 KiB     16   4 KiB     32   4 KiB
+  //    48   4 KiB     64   4 KiB     80   4 KiB     96   4 KiB
+  //   112   4 KiB    128   8 KiB    144   4 KiB    160   8 KiB
+  //   176   4 KiB    192   4 KiB    208   8 KiB    224   4 KiB
+  //   240   8 KiB    256  16 KiB    272   8 KiB    288   4 KiB
+  //   304  12 KiB    320  12 KiB    336   4 KiB    352   8 KiB
+  //   368   4 KiB    384   8 KiB    400  20 KiB    416  16 KiB
+  //   432  12 KiB    448   4 KiB    464  16 KiB    480   8 KiB
+  //   496  20 KiB    512  32 KiB    768  16 KiB   1024  64 KiB
+  //  1280  24 KiB   1536  32 KiB   1792  16 KiB   2048 128 KiB
+  //  2304  16 KiB   2560  48 KiB   2816  36 KiB   3072  64 KiB
+  //  3328  36 KiB   3584  32 KiB   3840  64 KiB
+  inline void Init(SizeClass aSizeClass);
+};
+
+// We try to keep the above structure aligned with common cache lines sizes,
+// often that's 64 bytes on x86 and ARM, we don't make assumptions for other
+// architectures.
+#if defined(__x86_64__) || defined(__aarch64__)
+// On 64bit platforms this structure is often 48 bytes
+// long, which means every other array element will be properly aligned.
+static_assert(sizeof(arena_bin_t) == 48);
+#elif defined(__x86__) || defined(__arm__)
+static_assert(sizeof(arena_bin_t) == 32);
+#endif
+
+struct arena_t {
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+  uint32_t mMagic;
+#  define ARENA_MAGIC 0x947d3d24
+#endif
+
+  // Linkage for the tree of arenas by id.
+  RedBlackTreeNode<arena_t> mLink;
+
+  // Arena id, that we keep away from the beginning of the struct so that
+  // free list pointers in TypedBaseAlloc<arena_t> don't overflow in it,
+  // and it keeps the value it had after the destructor.
+  arena_id_t mId;
+
+  // All operations on this arena require that lock be locked.  The MaybeMutex
+  // class well elude locking if the arena is accessed from a single thread
+  // only.
+  MaybeMutex mLock MOZ_UNANNOTATED;
+
+  arena_stats_t mStats;
+
+ private:
+  // Tree of dirty-page-containing chunks this arena manages.
+  RedBlackTree<arena_chunk_t, ArenaDirtyChunkTrait> mChunksDirty;
+
+#ifdef MALLOC_DOUBLE_PURGE
+  // Head of a linked list of MADV_FREE'd-page-containing chunks this
+  // arena manages.
+  DoublyLinkedList<arena_chunk_t> mChunksMAdvised;
+#endif
+
+  // In order to avoid rapid chunk allocation/deallocation when an arena
+  // oscillates right on the cusp of needing a new chunk, cache the most
+  // recently freed chunk.  The spare is left in the arena's chunk trees
+  // until it is deleted.
+  //
+  // There is one spare chunk per arena, rather than one spare total, in
+  // order to avoid interactions between multiple threads that could make
+  // a single spare inadequate.
+  arena_chunk_t* mSpare;
+
+  // A per-arena opt-in to randomize the offset of small allocations
+  bool mRandomizeSmallAllocations;
+
+  // Whether this is a private arena. Multiple public arenas are just a
+  // performance optimization and not a safety feature.
+  //
+  // Since, for example, we don't want thread-local arenas to grow too much, we
+  // use the default arena for bigger allocations. We use this member to allow
+  // realloc() to switch out of our arena if needed (which is not allowed for
+  // private arenas for security).
+  bool mIsPrivate;
+
+  // A pseudorandom number generator. Initially null, it gets initialized
+  // on first use to avoid recursive malloc initialization (e.g. on OSX
+  // arc4random allocates memory).
+  mozilla::non_crypto::XorShift128PlusRNG* mPRNG;
+
+ public:
+  // Current count of pages within unused runs that are potentially
+  // dirty, and for which madvise(... MADV_FREE) has not been called.  By
+  // tracking this, we can institute a limit on how much dirty unused
+  // memory is mapped for each arena.
+  size_t mNumDirty;
+
+  // Maximum value allowed for mNumDirty.
+  size_t mMaxDirty;
+
+  int32_t mMaxDirtyIncreaseOverride;
+  int32_t mMaxDirtyDecreaseOverride;
+
+ private:
+  // Size/address-ordered tree of this arena's available runs.  This tree
+  // is used for first-best-fit run allocation.
+  RedBlackTree<arena_chunk_map_t, ArenaAvailTreeTrait> mRunsAvail;
+
+ public:
+  // mBins is used to store rings of free regions of the following sizes,
+  // assuming a 16-byte quantum, 4kB pagesize, and default MALLOC_OPTIONS.
+  //
+  //  | mBins[i] | size |
+  //  +----------+------+
+  //  |       0  |    2 |
+  //  |       1  |    4 |
+  //  |       2  |    8 |
+  //  +----------+------+
+  //  |       3  |   16 |
+  //  |       4  |   32 |
+  //  |       5  |   48 |
+  //  |       6  |   64 |
+  //  |          :      :
+  //  |          :      :
+  //  |      33  |  496 |
+  //  |      34  |  512 |
+  //  +----------+------+
+  //  |      35  |  768 |
+  //  |      36  | 1024 |
+  //  |          :      :
+  //  |          :      :
+  //  |      46  | 3584 |
+  //  |      47  | 3840 |
+  //  +----------+------+
+  arena_bin_t mBins[1];  // Dynamically sized.
+
+  explicit arena_t(arena_params_t* aParams, bool aIsPrivate);
+  ~arena_t();
+
+ private:
+  void InitChunk(arena_chunk_t* aChunk);
+
+  // This may return a chunk that should be destroyed with chunk_dealloc outside
+  // of the arena lock.  It is not the same chunk as was passed in (since that
+  // chunk now becomes mSpare).
+  [[nodiscard]] arena_chunk_t* DeallocChunk(arena_chunk_t* aChunk);
+
+  arena_run_t* AllocRun(size_t aSize, bool aLarge, bool aZero);
+
+  arena_chunk_t* DallocRun(arena_run_t* aRun, bool aDirty);
+
+  [[nodiscard]] bool SplitRun(arena_run_t* aRun, size_t aSize, bool aLarge,
+                              bool aZero);
+
+  void TrimRunHead(arena_chunk_t* aChunk, arena_run_t* aRun, size_t aOldSize,
+                   size_t aNewSize);
+
+  void TrimRunTail(arena_chunk_t* aChunk, arena_run_t* aRun, size_t aOldSize,
+                   size_t aNewSize, bool dirty);
+
+  arena_run_t* GetNonFullBinRun(arena_bin_t* aBin);
+
+  inline uint8_t FindFreeBitInMask(uint32_t aMask, uint32_t& aRng);
+
+  inline void* ArenaRunRegAlloc(arena_run_t* aRun, arena_bin_t* aBin);
+
+  inline void* MallocSmall(size_t aSize, bool aZero);
+
+  void* MallocLarge(size_t aSize, bool aZero);
+
+  void* MallocHuge(size_t aSize, bool aZero);
+
+  void* PallocLarge(size_t aAlignment, size_t aSize, size_t aAllocSize);
+
+  void* PallocHuge(size_t aSize, size_t aAlignment, bool aZero);
+
+  void RallocShrinkLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
+                         size_t aOldSize);
+
+  bool RallocGrowLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
+                       size_t aOldSize);
+
+  void* RallocSmallOrLarge(void* aPtr, size_t aSize, size_t aOldSize);
+
+  void* RallocHuge(void* aPtr, size_t aSize, size_t aOldSize);
+
+ public:
+  inline void* Malloc(size_t aSize, bool aZero);
+
+  void* Palloc(size_t aAlignment, size_t aSize);
+
+  // This may return a chunk that should be destroyed with chunk_dealloc outside
+  // of the arena lock.  It is not the same chunk as was passed in (since that
+  // chunk now becomes mSpare).
+  [[nodiscard]] inline arena_chunk_t* DallocSmall(arena_chunk_t* aChunk,
+                                                  void* aPtr,
+                                                  arena_chunk_map_t* aMapElm);
+
+  [[nodiscard]] arena_chunk_t* DallocLarge(arena_chunk_t* aChunk, void* aPtr);
+
+  void* Ralloc(void* aPtr, size_t aSize, size_t aOldSize);
+
+  size_t EffectiveMaxDirty();
+
+  // Passing one means purging all.
+  void Purge(size_t aMaxDirty);
+
+  void HardPurge();
+
+  bool IsMainThreadOnly() const { return !mLock.LockIsEnabled(); }
+
+  void* operator new(size_t aCount) = delete;
+
+  void* operator new(size_t aCount, const fallible_t&) noexcept;
+
+  void operator delete(void*);
+};
+
+struct ArenaTreeTrait {
+  static RedBlackTreeNode<arena_t>& GetTreeNode(arena_t* aThis) {
+    return aThis->mLink;
+  }
+
+  static inline Order Compare(arena_t* aNode, arena_t* aOther) {
+    MOZ_ASSERT(aNode);
+    MOZ_ASSERT(aOther);
+    return CompareInt(aNode->mId, aOther->mId);
+  }
+};
+
+// Bookkeeping for all the arenas used by the allocator.
+// Arenas are separated in two categories:
+// - "private" arenas, used through the moz_arena_* API
+// - all the other arenas: the default arena, and thread-local arenas,
+//   used by the standard API.
+class ArenaCollection {
+ public:
+  bool Init() {
+    mArenas.Init();
+    mPrivateArenas.Init();
+    mMainThreadArenas.Init();
+    arena_params_t params;
+    // The main arena allows more dirty pages than the default for other arenas.
+    params.mMaxDirty = opt_dirty_max;
+    mDefaultArena =
+        mLock.Init() ? CreateArena(/* aIsPrivate = */ false, &params) : nullptr;
+    return bool(mDefaultArena);
+  }
+
+  inline arena_t* GetById(arena_id_t aArenaId, bool aIsPrivate);
+
+  arena_t* CreateArena(bool aIsPrivate, arena_params_t* aParams);
+
+  void DisposeArena(arena_t* aArena) {
+    MutexAutoLock lock(mLock);
+    Tree& tree =
+        aArena->IsMainThreadOnly() ? mMainThreadArenas : mPrivateArenas;
+
+    MOZ_RELEASE_ASSERT(tree.Search(aArena), "Arena not in tree");
+    tree.Remove(aArena);
+    delete aArena;
+  }
+
+  void SetDefaultMaxDirtyPageModifier(int32_t aModifier) {
+    mDefaultMaxDirtyPageModifier = aModifier;
+  }
+  int32_t DefaultMaxDirtyPageModifier() { return mDefaultMaxDirtyPageModifier; }
+
+  using Tree = RedBlackTree<arena_t, ArenaTreeTrait>;
+
+  struct Iterator : Tree::Iterator {
+    explicit Iterator(Tree* aTree, Tree* aSecondTree,
+                      Tree* aThirdTree = nullptr)
+        : Tree::Iterator(aTree),
+          mSecondTree(aSecondTree),
+          mThirdTree(aThirdTree) {}
+
+    Item<Iterator> begin() {
+      return Item<Iterator>(this, *Tree::Iterator::begin());
+    }
+
+    Item<Iterator> end() { return Item<Iterator>(this, nullptr); }
+
+    arena_t* Next() {
+      arena_t* result = Tree::Iterator::Next();
+      if (!result && mSecondTree) {
+        new (this) Iterator(mSecondTree, mThirdTree);
+        result = *Tree::Iterator::begin();
+      }
+      return result;
+    }
+
+   private:
+    Tree* mSecondTree;
+    Tree* mThirdTree;
+  };
+
+  Iterator iter() {
+    if (IsOnMainThreadWeak()) {
+      return Iterator(&mArenas, &mPrivateArenas, &mMainThreadArenas);
+    }
+    return Iterator(&mArenas, &mPrivateArenas);
+  }
+
+  inline arena_t* GetDefault() { return mDefaultArena; }
+
+  Mutex mLock MOZ_UNANNOTATED;
+
+  // We're running on the main thread which is set by a call to SetMainThread().
+  bool IsOnMainThread() const {
+    return mMainThreadId.isSome() && mMainThreadId.value() == GetThreadId();
+  }
+
+  // We're running on the main thread or SetMainThread() has never been called.
+  bool IsOnMainThreadWeak() const {
+    return mMainThreadId.isNothing() || IsOnMainThread();
+  }
+
+  // After a fork set the new thread ID in the child.
+  void PostForkFixMainThread() {
+    if (mMainThreadId.isSome()) {
+      // Only if the main thread has been defined.
+      mMainThreadId = Some(GetThreadId());
+    }
+  }
+
+  void SetMainThread() {
+    MutexAutoLock lock(mLock);
+    MOZ_ASSERT(mMainThreadId.isNothing());
+    mMainThreadId = Some(GetThreadId());
+  }
+
+ private:
+  const static arena_id_t MAIN_THREAD_ARENA_BIT = 0x1;
+
+  inline arena_t* GetByIdInternal(Tree& aTree, arena_id_t aArenaId);
+
+  arena_id_t MakeRandArenaId(bool aIsMainThreadOnly) const;
+  static bool ArenaIdIsMainThreadOnly(arena_id_t aArenaId) {
+    return aArenaId & MAIN_THREAD_ARENA_BIT;
+  }
+
+  arena_t* mDefaultArena;
+  arena_id_t mLastPublicArenaId;
+
+  // Accessing mArenas and mPrivateArenas can only be done while holding mLock.
+  // Since mMainThreadArenas can only be used from the main thread, it can be
+  // accessed without a lock which is why it is a seperate tree.
+  Tree mArenas;
+  Tree mPrivateArenas;
+  Tree mMainThreadArenas;
+  Atomic<int32_t, MemoryOrdering::Relaxed> mDefaultMaxDirtyPageModifier;
+  Maybe<ThreadId> mMainThreadId;
+};
+
+static ArenaCollection gArenas;
+
+// ******
+// Chunks.
+static AddressRadixTree<(sizeof(void*) << 3) - LOG2(kChunkSize)> gChunkRTree;
+
+// Protects chunk-related data structures.
+static Mutex chunks_mtx;
+
+// Trees of chunks that were previously allocated (trees differ only in node
+// ordering).  These are used when allocating chunks, in an attempt to re-use
+// address space.  Depending on function, different tree orderings are needed,
+// which is why there are two trees with the same contents.
+static RedBlackTree<extent_node_t, ExtentTreeSzTrait> gChunksBySize
+    MOZ_GUARDED_BY(chunks_mtx);
+static RedBlackTree<extent_node_t, ExtentTreeTrait> gChunksByAddress
+    MOZ_GUARDED_BY(chunks_mtx);
+
+// Protects huge allocation-related data structures.
+static Mutex huge_mtx;
+
+// Tree of chunks that are stand-alone huge allocations.
+static RedBlackTree<extent_node_t, ExtentTreeTrait> huge
+    MOZ_GUARDED_BY(huge_mtx);
+
+// Huge allocation statistics.
+static size_t huge_allocated MOZ_GUARDED_BY(huge_mtx);
+static size_t huge_mapped MOZ_GUARDED_BY(huge_mtx);
+
+// **************************
+// base (internal allocation).
+
+static Mutex base_mtx;
+
+// Current pages that are being used for internal memory allocations.  These
+// pages are carved up in cacheline-size quanta, so that there is no chance of
+// false cache line sharing.
+static void* base_pages MOZ_GUARDED_BY(base_mtx);
+static void* base_next_addr MOZ_GUARDED_BY(base_mtx);
+static void* base_next_decommitted MOZ_GUARDED_BY(base_mtx);
+// Address immediately past base_pages.
+static void* base_past_addr MOZ_GUARDED_BY(base_mtx);
+static size_t base_mapped MOZ_GUARDED_BY(base_mtx);
+static size_t base_committed MOZ_GUARDED_BY(base_mtx);
+
+// ******
+// Arenas.
+
+// The arena associated with the current thread (per
+// jemalloc_thread_local_arena) On OSX, __thread/thread_local circles back
+// calling malloc to allocate storage on first access on each thread, which
+// leads to an infinite loop, but pthread-based TLS somehow doesn't have this
+// problem.
+#if !defined(XP_DARWIN)
+static MOZ_THREAD_LOCAL(arena_t*) thread_arena;
+#else
+static detail::ThreadLocal<arena_t*, detail::ThreadLocalKeyStorage>
+    thread_arena;
+#endif
+
+// *****************************
+// Runtime configuration options.
+
+#ifdef MALLOC_RUNTIME_CONFIG
+#  define MALLOC_RUNTIME_VAR static
+#else
+#  define MALLOC_RUNTIME_VAR static const
+#endif
+
+enum PoisonType {
+  NONE,
+  SOME,
+  ALL,
+};
+
+MALLOC_RUNTIME_VAR bool opt_junk = false;
+MALLOC_RUNTIME_VAR bool opt_zero = false;
+
+#ifdef EARLY_BETA_OR_EARLIER
+MALLOC_RUNTIME_VAR PoisonType opt_poison = ALL;
+#else
+MALLOC_RUNTIME_VAR PoisonType opt_poison = SOME;
+#endif
+
+MALLOC_RUNTIME_VAR size_t opt_poison_size = kCacheLineSize * 4;
+
+static bool opt_randomize_small = true;
+
+// ***************************************************************************
+// Begin forward declarations.
+
+static void* chunk_alloc(size_t aSize, size_t aAlignment, bool aBase);
+static void chunk_dealloc(void* aChunk, size_t aSize, ChunkType aType);
+#ifdef MOZ_DEBUG
+static void chunk_assert_zero(void* aPtr, size_t aSize);
+#endif
+static void huge_dalloc(void* aPtr, arena_t* aArena);
+static bool malloc_init_hard();
+
+#ifndef XP_WIN
+#  ifdef XP_DARWIN
+#    define FORK_HOOK extern "C"
+#  else
+#    define FORK_HOOK static
+#  endif
+FORK_HOOK void _malloc_prefork(void);
+FORK_HOOK void _malloc_postfork_parent(void);
+FORK_HOOK void _malloc_postfork_child(void);
+#endif
+
+// End forward declarations.
+// ***************************************************************************
+
+// FreeBSD's pthreads implementation calls malloc(3), so the malloc
+// implementation has to take pains to avoid infinite recursion during
+// initialization.
+// Returns whether the allocator was successfully initialized.
+static inline bool malloc_init() {
+  if (!malloc_initialized) {
+    return malloc_init_hard();
+  }
+  return true;
+}
+
+static void _malloc_message(const char* p) {
+#if !defined(XP_WIN)
+#  define _write write
+#endif
+  // Pretend to check _write() errors to suppress gcc warnings about
+  // warn_unused_result annotations in some versions of glibc headers.
+  if (_write(STDERR_FILENO, p, (unsigned int)strlen(p)) < 0) {
+    return;
+  }
+}
+
+template <typename... Args>
+static void _malloc_message(const char* p, Args... args) {
+  _malloc_message(p);
+  _malloc_message(args...);
+}
+
+#ifdef ANDROID
+// Android's pthread.h does not declare pthread_atfork() until SDK 21.
+extern "C" MOZ_EXPORT int pthread_atfork(void (*)(void), void (*)(void),
+                                         void (*)(void));
+#endif
+
+// ***************************************************************************
+// Begin Utility functions/macros.
+
+// Return the chunk address for allocation address a.
+static inline arena_chunk_t* GetChunkForPtr(const void* aPtr) {
+  return (arena_chunk_t*)(uintptr_t(aPtr) & ~kChunkSizeMask);
+}
+
+// Return the chunk offset of address a.
+static inline size_t GetChunkOffsetForPtr(const void* aPtr) {
+  return (size_t)(uintptr_t(aPtr) & kChunkSizeMask);
+}
+
+static inline const char* _getprogname(void) { return "<jemalloc>"; }
+
+static inline void MaybePoison(void* aPtr, size_t aSize) {
+  size_t size;
+  switch (opt_poison) {
+    case NONE:
+      return;
+    case SOME:
+      size = std::min(aSize, opt_poison_size);
+      break;
+    case ALL:
+      size = aSize;
+      break;
+  }
+  MOZ_ASSERT(size != 0 && size <= aSize);
+  memset(aPtr, kAllocPoison, size);
+}
+
+// Fill the given range of memory with zeroes or junk depending on opt_junk and
+// opt_zero.
+static inline void ApplyZeroOrJunk(void* aPtr, size_t aSize) {
+  if (opt_junk) {
+    memset(aPtr, kAllocJunk, aSize);
+  } else if (opt_zero) {
+    memset(aPtr, 0, aSize);
+  }
+}
+
+// On Windows, delay crashing on OOM.
+#ifdef XP_WIN
+
+// Implementation of VirtualAlloc wrapper (bug 1716727).
+namespace MozAllocRetries {
+
+// Maximum retry count on OOM.
+constexpr size_t kMaxAttempts = 10;
+// Minimum delay time between retries. (The actual delay time may be larger. See
+// Microsoft's documentation for ::Sleep() for details.)
+constexpr size_t kDelayMs = 50;
+
+using StallSpecs = ::mozilla::StallSpecs;
+
+static constexpr StallSpecs maxStall = {.maxAttempts = kMaxAttempts,
+                                        .delayMs = kDelayMs};
+
+static inline StallSpecs GetStallSpecs() {
+#  if defined(JS_STANDALONE)
+  // GetGeckoProcessType() isn't available in this configuration. (SpiderMonkey
+  // on Windows mostly skips this in favor of directly calling ::VirtualAlloc(),
+  // though, so it's probably not going to matter whether we stall here or not.)
+  return maxStall;
+#  else
+  switch (GetGeckoProcessType()) {
+    // For the main process, stall for the maximum permissible time period. (The
+    // main process is the most important one to keep alive.)
+    case GeckoProcessType::GeckoProcessType_Default:
+      return maxStall;
+
+    // For all other process types, stall for at most half as long.
+    default:
+      return {.maxAttempts = maxStall.maxAttempts / 2,
+              .delayMs = maxStall.delayMs};
+  }
+#  endif
+}
+
+// Drop-in wrapper around VirtualAlloc. When out of memory, may attempt to stall
+// and retry rather than returning immediately, in hopes that the page file is
+// about to be expanded by Windows.
+//
+// Ref:
+// https://docs.microsoft.com/en-us/troubleshoot/windows-client/performance/slow-page-file-growth-memory-allocation-errors
+[[nodiscard]] void* MozVirtualAlloc(LPVOID lpAddress, SIZE_T dwSize,
+                                    DWORD flAllocationType, DWORD flProtect) {
+  DWORD const lastError = ::GetLastError();
+
+  constexpr auto IsOOMError = [] {
+    switch (::GetLastError()) {
+      // This is the usual error result from VirtualAlloc for OOM.
+      case ERROR_COMMITMENT_LIMIT:
+      // Although rare, this has also been observed in low-memory situations.
+      // (Presumably this means Windows can't allocate enough kernel-side space
+      // for its own internal representation of the process's virtual address
+      // space.)
+      case ERROR_NOT_ENOUGH_MEMORY:
+        return true;
+    }
+    return false;
+  };
+
+  {
+    void* ptr = ::VirtualAlloc(lpAddress, dwSize, flAllocationType, flProtect);
+    if (MOZ_LIKELY(ptr)) return ptr;
+
+    // We can't do anything for errors other than OOM...
+    if (!IsOOMError()) return nullptr;
+    // ... or if this wasn't a request to commit memory in the first place.
+    // (This function has no strategy for resolving MEM_RESERVE failures.)
+    if (!(flAllocationType & MEM_COMMIT)) return nullptr;
+  }
+
+  // Retry as many times as desired (possibly zero).
+  const StallSpecs stallSpecs = GetStallSpecs();
+
+  const auto ret =
+      stallSpecs.StallAndRetry(&::Sleep, [&]() -> std::optional<void*> {
+        void* ptr =
+            ::VirtualAlloc(lpAddress, dwSize, flAllocationType, flProtect);
+
+        if (ptr) {
+          // The OOM status has been handled, and should not be reported to
+          // telemetry.
+          if (IsOOMError()) {
+            ::SetLastError(lastError);
+          }
+          return ptr;
+        }
+
+        // Failure for some reason other than OOM.
+        if (!IsOOMError()) {
+          return nullptr;
+        }
+
+        return std::nullopt;
+      });
+
+  return ret.value_or(nullptr);
+}
+}  // namespace MozAllocRetries
+
+using MozAllocRetries::MozVirtualAlloc;
+
+namespace mozilla {
+MOZ_JEMALLOC_API StallSpecs GetAllocatorStallSpecs() {
+  return ::MozAllocRetries::GetStallSpecs();
+}
+}  // namespace mozilla
+
+#endif  // XP_WIN
+
+// ***************************************************************************
+
+static inline void pages_decommit(void* aAddr, size_t aSize) {
+#ifdef XP_WIN
+  // The region starting at addr may have been allocated in multiple calls
+  // to VirtualAlloc and recycled, so decommitting the entire region in one
+  // go may not be valid. However, since we allocate at least a chunk at a
+  // time, we may touch any region in chunksized increments.
+  size_t pages_size = std::min(aSize, kChunkSize - GetChunkOffsetForPtr(aAddr));
+  while (aSize > 0) {
+    // This will cause Access Violation on read and write and thus act as a
+    // guard page or region as well.
+    if (!VirtualFree(aAddr, pages_size, MEM_DECOMMIT)) {
+      MOZ_CRASH();
+    }
+    aAddr = (void*)((uintptr_t)aAddr + pages_size);
+    aSize -= pages_size;
+    pages_size = std::min(aSize, kChunkSize);
+  }
+#else
+  if (mmap(aAddr, aSize, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1,
+           0) == MAP_FAILED) {
+    // We'd like to report the OOM for our tooling, but we can't allocate
+    // memory at this point, so avoid the use of printf.
+    const char out_of_mappings[] =
+        "[unhandlable oom] Failed to mmap, likely no more mappings "
+        "available " __FILE__ " : " MOZ_STRINGIFY(__LINE__);
+    if (errno == ENOMEM) {
+#  ifndef ANDROID
+      fputs(out_of_mappings, stderr);
+      fflush(stderr);
+#  endif
+      MOZ_CRASH_ANNOTATE(out_of_mappings);
+    }
+    MOZ_REALLY_CRASH(__LINE__);
+  }
+  MozTagAnonymousMemory(aAddr, aSize, "jemalloc-decommitted");
+#endif
+}
+
+// Commit pages. Returns whether pages were committed.
+[[nodiscard]] static inline bool pages_commit(void* aAddr, size_t aSize) {
+#ifdef XP_WIN
+  // The region starting at addr may have been allocated in multiple calls
+  // to VirtualAlloc and recycled, so committing the entire region in one
+  // go may not be valid. However, since we allocate at least a chunk at a
+  // time, we may touch any region in chunksized increments.
+  size_t pages_size = std::min(aSize, kChunkSize - GetChunkOffsetForPtr(aAddr));
+  while (aSize > 0) {
+    if (!MozVirtualAlloc(aAddr, pages_size, MEM_COMMIT, PAGE_READWRITE)) {
+      return false;
+    }
+    aAddr = (void*)((uintptr_t)aAddr + pages_size);
+    aSize -= pages_size;
+    pages_size = std::min(aSize, kChunkSize);
+  }
+#else
+  if (mmap(aAddr, aSize, PROT_READ | PROT_WRITE,
+           MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) == MAP_FAILED) {
+    return false;
+  }
+  MozTagAnonymousMemory(aAddr, aSize, "jemalloc");
+#endif
+  return true;
+}
+
+static bool base_pages_alloc(size_t minsize) MOZ_REQUIRES(base_mtx) {
+  size_t csize;
+  size_t pminsize;
+
+  MOZ_ASSERT(minsize != 0);
+  csize = CHUNK_CEILING(minsize);
+  base_pages = chunk_alloc(csize, kChunkSize, true);
+  if (!base_pages) {
+    return true;
+  }
+  base_next_addr = base_pages;
+  base_past_addr = (void*)((uintptr_t)base_pages + csize);
+  // Leave enough pages for minsize committed, since otherwise they would
+  // have to be immediately recommitted.
+  pminsize = PAGE_CEILING(minsize);
+  base_next_decommitted = (void*)((uintptr_t)base_pages + pminsize);
+  if (pminsize < csize) {
+    pages_decommit(base_next_decommitted, csize - pminsize);
+  }
+  base_mapped += csize;
+  base_committed += pminsize;
+
+  return false;
+}
+
+static void* base_alloc(size_t aSize) {
+  void* ret;
+  size_t csize;
+
+  // Round size up to nearest multiple of the cacheline size.
+  csize = CACHELINE_CEILING(aSize);
+
+  MutexAutoLock lock(base_mtx);
+  // Make sure there's enough space for the allocation.
+  if ((uintptr_t)base_next_addr + csize > (uintptr_t)base_past_addr) {
+    if (base_pages_alloc(csize)) {
+      return nullptr;
+    }
+  }
+  // Allocate.
+  ret = base_next_addr;
+  base_next_addr = (void*)((uintptr_t)base_next_addr + csize);
+  // Make sure enough pages are committed for the new allocation.
+  if ((uintptr_t)base_next_addr > (uintptr_t)base_next_decommitted) {
+    void* pbase_next_addr = (void*)(PAGE_CEILING((uintptr_t)base_next_addr));
+
+    if (!pages_commit(
+            base_next_decommitted,
+            (uintptr_t)pbase_next_addr - (uintptr_t)base_next_decommitted)) {
+      return nullptr;
+    }
+
+    base_committed +=
+        (uintptr_t)pbase_next_addr - (uintptr_t)base_next_decommitted;
+    base_next_decommitted = pbase_next_addr;
+  }
+
+  return ret;
+}
+
+static void* base_calloc(size_t aNumber, size_t aSize) {
+  void* ret = base_alloc(aNumber * aSize);
+  if (ret) {
+    memset(ret, 0, aNumber * aSize);
+  }
+  return ret;
+}
+
+// A specialization of the base allocator with a free list.
+template <typename T>
+struct TypedBaseAlloc {
+  static T* sFirstFree;
+
+  static size_t size_of() { return sizeof(T); }
+
+  static T* alloc() {
+    T* ret;
+
+    base_mtx.Lock();
+    if (sFirstFree) {
+      ret = sFirstFree;
+      sFirstFree = *(T**)ret;
+      base_mtx.Unlock();
+    } else {
+      base_mtx.Unlock();
+      ret = (T*)base_alloc(size_of());
+    }
+
+    return ret;
+  }
+
+  static void dealloc(T* aNode) {
+    MutexAutoLock lock(base_mtx);
+    *(T**)aNode = sFirstFree;
+    sFirstFree = aNode;
+  }
+};
+
+using ExtentAlloc = TypedBaseAlloc<extent_node_t>;
+
+template <>
+extent_node_t* ExtentAlloc::sFirstFree = nullptr;
+
+template <>
+arena_t* TypedBaseAlloc<arena_t>::sFirstFree = nullptr;
+
+template <>
+size_t TypedBaseAlloc<arena_t>::size_of() {
+  // Allocate enough space for trailing bins.
+  return sizeof(arena_t) + (sizeof(arena_bin_t) * (NUM_SMALL_CLASSES - 1));
+}
+
+template <typename T>
+struct BaseAllocFreePolicy {
+  void operator()(T* aPtr) { TypedBaseAlloc<T>::dealloc(aPtr); }
+};
+
+using UniqueBaseNode =
+    UniquePtr<extent_node_t, BaseAllocFreePolicy<extent_node_t>>;
+
+// End Utility functions/macros.
+// ***************************************************************************
+// Begin chunk management functions.
+
+#ifdef XP_WIN
+
+static void* pages_map(void* aAddr, size_t aSize) {
+  void* ret = nullptr;
+  ret = MozVirtualAlloc(aAddr, aSize, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+  return ret;
+}
+
+static void pages_unmap(void* aAddr, size_t aSize) {
+  if (VirtualFree(aAddr, 0, MEM_RELEASE) == 0) {
+    _malloc_message(_getprogname(), ": (malloc) Error in VirtualFree()\n");
+  }
+}
+#else
+
+static void pages_unmap(void* aAddr, size_t aSize) {
+  if (munmap(aAddr, aSize) == -1) {
+    char buf[64];
+
+    if (strerror_r(errno, buf, sizeof(buf)) == 0) {
+      _malloc_message(_getprogname(), ": (malloc) Error in munmap(): ", buf,
+                      "\n");
+    }
+  }
+}
+
+static void* pages_map(void* aAddr, size_t aSize) {
+  void* ret;
+#  if defined(__ia64__) || \
+      (defined(__sparc__) && defined(__arch64__) && defined(__linux__))
+  // The JS engine assumes that all allocated pointers have their high 17 bits
+  // clear, which ia64's mmap doesn't support directly. However, we can emulate
+  // it by passing mmap an "addr" parameter with those bits clear. The mmap will
+  // return that address, or the nearest available memory above that address,
+  // providing a near-guarantee that those bits are clear. If they are not, we
+  // return nullptr below to indicate out-of-memory.
+  //
+  // The addr is chosen as 0x0000070000000000, which still allows about 120TB of
+  // virtual address space.
+  //
+  // See Bug 589735 for more information.
+  bool check_placement = true;
+  if (!aAddr) {
+    aAddr = (void*)0x0000070000000000;
+    check_placement = false;
+  }
+#  endif
+
+#  if defined(__sparc__) && defined(__arch64__) && defined(__linux__)
+  const uintptr_t start = 0x0000070000000000ULL;
+  const uintptr_t end = 0x0000800000000000ULL;
+
+  // Copied from js/src/gc/Memory.cpp and adapted for this source
+  uintptr_t hint;
+  void* region = MAP_FAILED;
+  for (hint = start; region == MAP_FAILED && hint + aSize <= end;
+       hint += kChunkSize) {
+    region = mmap((void*)hint, aSize, PROT_READ | PROT_WRITE,
+                  MAP_PRIVATE | MAP_ANON, -1, 0);
+    if (region != MAP_FAILED) {
+      if (((size_t)region + (aSize - 1)) & 0xffff800000000000) {
+        if (munmap(region, aSize)) {
+          MOZ_ASSERT(errno == ENOMEM);
+        }
+        region = MAP_FAILED;
+      }
+    }
+  }
+  ret = region;
+#  else
+  // We don't use MAP_FIXED here, because it can cause the *replacement*
+  // of existing mappings, and we only want to create new mappings.
+  ret =
+      mmap(aAddr, aSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+  MOZ_ASSERT(ret);
+#  endif
+  if (ret == MAP_FAILED) {
+    ret = nullptr;
+  }
+#  if defined(__ia64__) || \
+      (defined(__sparc__) && defined(__arch64__) && defined(__linux__))
+  // If the allocated memory doesn't have its upper 17 bits clear, consider it
+  // as out of memory.
+  else if ((long long)ret & 0xffff800000000000) {
+    munmap(ret, aSize);
+    ret = nullptr;
+  }
+  // If the caller requested a specific memory location, verify that's what mmap
+  // returned.
+  else if (check_placement && ret != aAddr) {
+#  else
+  else if (aAddr && ret != aAddr) {
+#  endif
+    // We succeeded in mapping memory, but not in the right place.
+    pages_unmap(ret, aSize);
+    ret = nullptr;
+  }
+  if (ret) {
+    MozTagAnonymousMemory(ret, aSize, "jemalloc");
+  }
+
+#  if defined(__ia64__) || \
+      (defined(__sparc__) && defined(__arch64__) && defined(__linux__))
+  MOZ_ASSERT(!ret || (!check_placement && ret) ||
+             (check_placement && ret == aAddr));
+#  else
+  MOZ_ASSERT(!ret || (!aAddr && ret != aAddr) || (aAddr && ret == aAddr));
+#  endif
+  return ret;
+}
+#endif
+
+#ifdef XP_DARWIN
+#  define VM_COPY_MIN kChunkSize
+static inline void pages_copy(void* dest, const void* src, size_t n) {
+  MOZ_ASSERT((void*)((uintptr_t)dest & ~gPageSizeMask) == dest);
+  MOZ_ASSERT(n >= VM_COPY_MIN);
+  MOZ_ASSERT((void*)((uintptr_t)src & ~gPageSizeMask) == src);
+
+  kern_return_t r = vm_copy(mach_task_self(), (vm_address_t)src, (vm_size_t)n,
+                            (vm_address_t)dest);
+  if (r != KERN_SUCCESS) {
+    MOZ_CRASH("vm_copy() failed");
+  }
+}
+
+#endif
+
+template <size_t Bits>
+bool AddressRadixTree<Bits>::Init() {
+  mLock.Init();
+  mRoot = (void**)base_calloc(1 << kBitsAtLevel1, sizeof(void*));
+  return mRoot;
+}
+
+template <size_t Bits>
+void** AddressRadixTree<Bits>::GetSlot(void* aKey, bool aCreate) {
+  uintptr_t key = reinterpret_cast<uintptr_t>(aKey);
+  uintptr_t subkey;
+  unsigned i, lshift, height, bits;
+  void** node;
+  void** child;
+
+  for (i = lshift = 0, height = kHeight, node = mRoot; i < height - 1;
+       i++, lshift += bits, node = child) {
+    bits = i ? kBitsPerLevel : kBitsAtLevel1;
+    subkey = (key << lshift) >> ((sizeof(void*) << 3) - bits);
+    child = (void**)node[subkey];
+    if (!child && aCreate) {
+      child = (void**)base_calloc(1 << kBitsPerLevel, sizeof(void*));
+      if (child) {
+        node[subkey] = child;
+      }
+    }
+    if (!child) {
+      return nullptr;
+    }
+  }
+
+  // node is a leaf, so it contains values rather than node
+  // pointers.
+  bits = i ? kBitsPerLevel : kBitsAtLevel1;
+  subkey = (key << lshift) >> ((sizeof(void*) << 3) - bits);
+  return &node[subkey];
+}
+
+template <size_t Bits>
+void* AddressRadixTree<Bits>::Get(void* aKey) {
+  void* ret = nullptr;
+
+  void** slot = GetSlot(aKey);
+
+  if (slot) {
+    ret = *slot;
+  }
+#ifdef MOZ_DEBUG
+  MutexAutoLock lock(mLock);
+
+  // Suppose that it were possible for a jemalloc-allocated chunk to be
+  // munmap()ped, followed by a different allocator in another thread re-using
+  // overlapping virtual memory, all without invalidating the cached rtree
+  // value.  The result would be a false positive (the rtree would claim that
+  // jemalloc owns memory that it had actually discarded).  I don't think this
+  // scenario is possible, but the following assertion is a prudent sanity
+  // check.
+  if (!slot) {
+    // In case a slot has been created in the meantime.
+    slot = GetSlot(aKey);
+  }
+  if (slot) {
+    // The MutexAutoLock above should act as a memory barrier, forcing
+    // the compiler to emit a new read instruction for *slot.
+    MOZ_ASSERT(ret == *slot);
+  } else {
+    MOZ_ASSERT(ret == nullptr);
+  }
+#endif
+  return ret;
+}
+
+template <size_t Bits>
+bool AddressRadixTree<Bits>::Set(void* aKey, void* aValue) {
+  MutexAutoLock lock(mLock);
+  void** slot = GetSlot(aKey, /* aCreate = */ true);
+  if (slot) {
+    *slot = aValue;
+  }
+  return slot;
+}
+
+// pages_trim, chunk_alloc_mmap_slow and chunk_alloc_mmap were cherry-picked
+// from upstream jemalloc 3.4.1 to fix Mozilla bug 956501.
+
+// Return the offset between a and the nearest aligned address at or below a.
+#define ALIGNMENT_ADDR2OFFSET(a, alignment) \
+  ((size_t)((uintptr_t)(a) & ((alignment)-1)))
+
+// Return the smallest alignment multiple that is >= s.
+#define ALIGNMENT_CEILING(s, alignment) \
+  (((s) + ((alignment)-1)) & (~((alignment)-1)))
+
+static void* pages_trim(void* addr, size_t alloc_size, size_t leadsize,
+                        size_t size) {
+  void* ret = (void*)((uintptr_t)addr + leadsize);
+
+  MOZ_ASSERT(alloc_size >= leadsize + size);
+#ifdef XP_WIN
+  {
+    void* new_addr;
+
+    pages_unmap(addr, alloc_size);
+    new_addr = pages_map(ret, size);
+    if (new_addr == ret) {
+      return ret;
+    }
+    if (new_addr) {
+      pages_unmap(new_addr, size);
+    }
+    return nullptr;
+  }
+#else
+  {
+    size_t trailsize = alloc_size - leadsize - size;
+
+    if (leadsize != 0) {
+      pages_unmap(addr, leadsize);
+    }
+    if (trailsize != 0) {
+      pages_unmap((void*)((uintptr_t)ret + size), trailsize);
+    }
+    return ret;
+  }
+#endif
+}
+
+static void* chunk_alloc_mmap_slow(size_t size, size_t alignment) {
+  void *ret, *pages;
+  size_t alloc_size, leadsize;
+
+  alloc_size = size + alignment - gRealPageSize;
+  // Beware size_t wrap-around.
+  if (alloc_size < size) {
+    return nullptr;
+  }
+  do {
+    pages = pages_map(nullptr, alloc_size);
+    if (!pages) {
+      return nullptr;
+    }
+    leadsize =
+        ALIGNMENT_CEILING((uintptr_t)pages, alignment) - (uintptr_t)pages;
+    ret = pages_trim(pages, alloc_size, leadsize, size);
+  } while (!ret);
+
+  MOZ_ASSERT(ret);
+  return ret;
+}
+
+static void* chunk_alloc_mmap(size_t size, size_t alignment) {
+  void* ret;
+  size_t offset;
+
+  // Ideally, there would be a way to specify alignment to mmap() (like
+  // NetBSD has), but in the absence of such a feature, we have to work
+  // hard to efficiently create aligned mappings. The reliable, but
+  // slow method is to create a mapping that is over-sized, then trim the
+  // excess. However, that always results in one or two calls to
+  // pages_unmap().
+  //
+  // Optimistically try mapping precisely the right amount before falling
+  // back to the slow method, with the expectation that the optimistic
+  // approach works most of the time.
+  ret = pages_map(nullptr, size);
+  if (!ret) {
+    return nullptr;
+  }
+  offset = ALIGNMENT_ADDR2OFFSET(ret, alignment);
+  if (offset != 0) {
+    pages_unmap(ret, size);
+    return chunk_alloc_mmap_slow(size, alignment);
+  }
+
+  MOZ_ASSERT(ret);
+  return ret;
+}
+
+// Purge and release the pages in the chunk of length `length` at `addr` to
+// the OS.
+// Returns whether the pages are guaranteed to be full of zeroes when the
+// function returns.
+// The force_zero argument explicitly requests that the memory is guaranteed
+// to be full of zeroes when the function returns.
+static bool pages_purge(void* addr, size_t length, bool force_zero) {
+  pages_decommit(addr, length);
+  return true;
+}
+
+static void* chunk_recycle(size_t aSize, size_t aAlignment) {
+  extent_node_t key;
+
+  size_t alloc_size = aSize + aAlignment - kChunkSize;
+  // Beware size_t wrap-around.
+  if (alloc_size < aSize) {
+    return nullptr;
+  }
+  key.mAddr = nullptr;
+  key.mSize = alloc_size;
+  chunks_mtx.Lock();
+  extent_node_t* node = gChunksBySize.SearchOrNext(&key);
+  if (!node) {
+    chunks_mtx.Unlock();
+    return nullptr;
+  }
+  size_t leadsize = ALIGNMENT_CEILING((uintptr_t)node->mAddr, aAlignment) -
+                    (uintptr_t)node->mAddr;
+  MOZ_ASSERT(node->mSize >= leadsize + aSize);
+  size_t trailsize = node->mSize - leadsize - aSize;
+  void* ret = (void*)((uintptr_t)node->mAddr + leadsize);
+
+  // All recycled chunks are zeroed (because they're purged) before being
+  // recycled.
+  MOZ_ASSERT(node->mChunkType == ZEROED_CHUNK);
+
+  // Remove node from the tree.
+  gChunksBySize.Remove(node);
+  gChunksByAddress.Remove(node);
+  if (leadsize != 0) {
+    // Insert the leading space as a smaller chunk.
+    node->mSize = leadsize;
+    gChunksBySize.Insert(node);
+    gChunksByAddress.Insert(node);
+    node = nullptr;
+  }
+  if (trailsize != 0) {
+    // Insert the trailing space as a smaller chunk.
+    if (!node) {
+      // An additional node is required, but
+      // TypedBaseAlloc::alloc() can cause a new base chunk to be
+      // allocated.  Drop chunks_mtx in order to avoid
+      // deadlock, and if node allocation fails, deallocate
+      // the result before returning an error.
+      chunks_mtx.Unlock();
+      node = ExtentAlloc::alloc();
+      if (!node) {
+        chunk_dealloc(ret, aSize, ZEROED_CHUNK);
+        return nullptr;
+      }
+      chunks_mtx.Lock();
+    }
+    node->mAddr = (void*)((uintptr_t)(ret) + aSize);
+    node->mSize = trailsize;
+    node->mChunkType = ZEROED_CHUNK;
+    gChunksBySize.Insert(node);
+    gChunksByAddress.Insert(node);
+    node = nullptr;
+  }
+
+  gRecycledSize -= aSize;
+
+  chunks_mtx.Unlock();
+
+  if (node) {
+    ExtentAlloc::dealloc(node);
+  }
+  if (!pages_commit(ret, aSize)) {
+    return nullptr;
+  }
+
+  return ret;
+}
+
+#ifdef XP_WIN
+// On Windows, calls to VirtualAlloc and VirtualFree must be matched, making it
+// awkward to recycle allocations of varying sizes. Therefore we only allow
+// recycling when the size equals the chunksize, unless deallocation is entirely
+// disabled.
+#  define CAN_RECYCLE(size) ((size) == kChunkSize)
+#else
+#  define CAN_RECYCLE(size) true
+#endif
+
+// Allocates `size` bytes of system memory aligned for `alignment`.
+// `base` indicates whether the memory will be used for the base allocator
+// (e.g. base_alloc).
+// `zeroed` is an outvalue that returns whether the allocated memory is
+// guaranteed to be full of zeroes. It can be omitted when the caller doesn't
+// care about the result.
+static void* chunk_alloc(size_t aSize, size_t aAlignment, bool aBase) {
+  void* ret = nullptr;
+
+  MOZ_ASSERT(aSize != 0);
+  MOZ_ASSERT((aSize & kChunkSizeMask) == 0);
+  MOZ_ASSERT(aAlignment != 0);
+  MOZ_ASSERT((aAlignment & kChunkSizeMask) == 0);
+
+  // Base allocations can't be fulfilled by recycling because of
+  // possible deadlock or infinite recursion.
+  if (CAN_RECYCLE(aSize) && !aBase) {
+    ret = chunk_recycle(aSize, aAlignment);
+  }
+  if (!ret) {
+    ret = chunk_alloc_mmap(aSize, aAlignment);
+  }
+  if (ret && !aBase) {
+    if (!gChunkRTree.Set(ret, ret)) {
+      chunk_dealloc(ret, aSize, UNKNOWN_CHUNK);
+      return nullptr;
+    }
+  }
+
+  MOZ_ASSERT(GetChunkOffsetForPtr(ret) == 0);
+  return ret;
+}
+
+#ifdef MOZ_DEBUG
+static void chunk_assert_zero(void* aPtr, size_t aSize) {
+  size_t i;
+  size_t* p = (size_t*)(uintptr_t)aPtr;
+
+  for (i = 0; i < aSize / sizeof(size_t); i++) {
+    MOZ_ASSERT(p[i] == 0);
+  }
+}
+#endif
+
+static void chunk_record(void* aChunk, size_t aSize, ChunkType aType) {
+  extent_node_t key;
+
+  if (aType != ZEROED_CHUNK) {
+    if (pages_purge(aChunk, aSize, aType == HUGE_CHUNK)) {
+      aType = ZEROED_CHUNK;
+    }
+  }
+
+  // Allocate a node before acquiring chunks_mtx even though it might not
+  // be needed, because TypedBaseAlloc::alloc() may cause a new base chunk to
+  // be allocated, which could cause deadlock if chunks_mtx were already
+  // held.
+  UniqueBaseNode xnode(ExtentAlloc::alloc());
+  // Use xprev to implement conditional deferred deallocation of prev.
+  UniqueBaseNode xprev;
+
+  // RAII deallocates xnode and xprev defined above after unlocking
+  // in order to avoid potential dead-locks
+  MutexAutoLock lock(chunks_mtx);
+  key.mAddr = (void*)((uintptr_t)aChunk + aSize);
+  extent_node_t* node = gChunksByAddress.SearchOrNext(&key);
+  // Try to coalesce forward.
+  if (node && node->mAddr == key.mAddr) {
+    // Coalesce chunk with the following address range.  This does
+    // not change the position within gChunksByAddress, so only
+    // remove/insert from/into gChunksBySize.
+    gChunksBySize.Remove(node);
+    node->mAddr = aChunk;
+    node->mSize += aSize;
+    if (node->mChunkType != aType) {
+      node->mChunkType = RECYCLED_CHUNK;
+    }
+    gChunksBySize.Insert(node);
+  } else {
+    // Coalescing forward failed, so insert a new node.
+    if (!xnode) {
+      // TypedBaseAlloc::alloc() failed, which is an exceedingly
+      // unlikely failure.  Leak chunk; its pages have
+      // already been purged, so this is only a virtual
+      // memory leak.
+      return;
+    }
+    node = xnode.release();
+    node->mAddr = aChunk;
+    node->mSize = aSize;
+    node->mChunkType = aType;
+    gChunksByAddress.Insert(node);
+    gChunksBySize.Insert(node);
+  }
+
+  // Try to coalesce backward.
+  extent_node_t* prev = gChunksByAddress.Prev(node);
+  if (prev && (void*)((uintptr_t)prev->mAddr + prev->mSize) == aChunk) {
+    // Coalesce chunk with the previous address range.  This does
+    // not change the position within gChunksByAddress, so only
+    // remove/insert node from/into gChunksBySize.
+    gChunksBySize.Remove(prev);
+    gChunksByAddress.Remove(prev);
+
+    gChunksBySize.Remove(node);
+    node->mAddr = prev->mAddr;
+    node->mSize += prev->mSize;
+    if (node->mChunkType != prev->mChunkType) {
+      node->mChunkType = RECYCLED_CHUNK;
+    }
+    gChunksBySize.Insert(node);
+
+    xprev.reset(prev);
+  }
+
+  gRecycledSize += aSize;
+}
+
+static void chunk_dealloc(void* aChunk, size_t aSize, ChunkType aType) {
+  MOZ_ASSERT(aChunk);
+  MOZ_ASSERT(GetChunkOffsetForPtr(aChunk) == 0);
+  MOZ_ASSERT(aSize != 0);
+  MOZ_ASSERT((aSize & kChunkSizeMask) == 0);
+
+  gChunkRTree.Unset(aChunk);
+
+  if (CAN_RECYCLE(aSize)) {
+    size_t recycled_so_far = gRecycledSize;
+    // In case some race condition put us above the limit.
+    if (recycled_so_far < gRecycleLimit) {
+      size_t recycle_remaining = gRecycleLimit - recycled_so_far;
+      size_t to_recycle;
+      if (aSize > recycle_remaining) {
+        to_recycle = recycle_remaining;
+        // Drop pages that would overflow the recycle limit
+        pages_trim(aChunk, aSize, 0, to_recycle);
+      } else {
+        to_recycle = aSize;
+      }
+      chunk_record(aChunk, to_recycle, aType);
+      return;
+    }
+  }
+
+  pages_unmap(aChunk, aSize);
+}
+
+#undef CAN_RECYCLE
+
+// End chunk management functions.
+// ***************************************************************************
+// Begin arena.
+
+static inline arena_t* thread_local_arena(bool enabled) {
+  arena_t* arena;
+
+  if (enabled) {
+    // The arena will essentially be leaked if this function is
+    // called with `false`, but it doesn't matter at the moment.
+    // because in practice nothing actually calls this function
+    // with `false`, except maybe at shutdown.
+    arena =
+        gArenas.CreateArena(/* aIsPrivate = */ false, /* aParams = */ nullptr);
+  } else {
+    arena = gArenas.GetDefault();
+  }
+  thread_arena.set(arena);
+  return arena;
+}
+
+inline void MozJemalloc::jemalloc_thread_local_arena(bool aEnabled) {
+  if (malloc_init()) {
+    thread_local_arena(aEnabled);
+  }
+}
+
+// Choose an arena based on a per-thread value.
+static inline arena_t* choose_arena(size_t size) {
+  arena_t* ret = nullptr;
+
+  // We can only use TLS if this is a PIC library, since for the static
+  // library version, libc's malloc is used by TLS allocation, which
+  // introduces a bootstrapping issue.
+
+  if (size > kMaxQuantumClass) {
+    // Force the default arena for larger allocations.
+    ret = gArenas.GetDefault();
+  } else {
+    // Check TLS to see if our thread has requested a pinned arena.
+    ret = thread_arena.get();
+    // If ret is non-null, it must not be in the first page.
+    MOZ_DIAGNOSTIC_ASSERT_IF(ret, (size_t)ret >= gPageSize);
+    if (!ret) {
+      // Nothing in TLS. Pin this thread to the default arena.
+      ret = thread_local_arena(false);
+    }
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(ret);
+  return ret;
+}
+
+inline uint8_t arena_t::FindFreeBitInMask(uint32_t aMask, uint32_t& aRng) {
+  if (mPRNG != nullptr) {
+    if (aRng == UINT_MAX) {
+      aRng = mPRNG->next() % 32;
+    }
+    uint8_t bitIndex;
+    // RotateRight asserts when provided bad input.
+    aMask = aRng ? RotateRight(aMask, aRng)
+                 : aMask;  // Rotate the mask a random number of slots
+    bitIndex = CountTrailingZeroes32(aMask);
+    return (bitIndex + aRng) % 32;
+  }
+  return CountTrailingZeroes32(aMask);
+}
+
+inline void* arena_t::ArenaRunRegAlloc(arena_run_t* aRun, arena_bin_t* aBin) {
+  void* ret;
+  unsigned i, mask, bit, regind;
+  uint32_t rndPos = UINT_MAX;
+
+  MOZ_DIAGNOSTIC_ASSERT(aRun->mMagic == ARENA_RUN_MAGIC);
+  MOZ_ASSERT(aRun->mRegionsMinElement < aBin->mRunNumRegionsMask);
+
+  // Move the first check outside the loop, so that aRun->mRegionsMinElement can
+  // be updated unconditionally, without the possibility of updating it
+  // multiple times.
+  i = aRun->mRegionsMinElement;
+  mask = aRun->mRegionsMask[i];
+  if (mask != 0) {
+    bit = FindFreeBitInMask(mask, rndPos);
+
+    regind = ((i << (LOG2(sizeof(int)) + 3)) + bit);
+    MOZ_ASSERT(regind < aBin->mRunNumRegions);
+    ret = (void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
+                  (aBin->mSizeClass * regind));
+
+    // Clear bit.
+    mask ^= (1U << bit);
+    aRun->mRegionsMask[i] = mask;
+
+    return ret;
+  }
+
+  for (i++; i < aBin->mRunNumRegionsMask; i++) {
+    mask = aRun->mRegionsMask[i];
+    if (mask != 0) {
+      bit = FindFreeBitInMask(mask, rndPos);
+
+      regind = ((i << (LOG2(sizeof(int)) + 3)) + bit);
+      MOZ_ASSERT(regind < aBin->mRunNumRegions);
+      ret = (void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
+                    (aBin->mSizeClass * regind));
+
+      // Clear bit.
+      mask ^= (1U << bit);
+      aRun->mRegionsMask[i] = mask;
+
+      // Make a note that nothing before this element
+      // contains a free region.
+      aRun->mRegionsMinElement = i;  // Low payoff: + (mask == 0);
+
+      return ret;
+    }
+  }
+  // Not reached.
+  MOZ_DIAGNOSTIC_ASSERT(0);
+  return nullptr;
+}
+
+static inline void arena_run_reg_dalloc(arena_run_t* run, arena_bin_t* bin,
+                                        void* ptr, size_t size) {
+  uint32_t diff, regind;
+  unsigned elm, bit;
+
+  MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
+
+  // Avoid doing division with a variable divisor if possible.  Using
+  // actual division here can reduce allocator throughput by over 20%!
+  diff =
+      (uint32_t)((uintptr_t)ptr - (uintptr_t)run - bin->mRunFirstRegionOffset);
+
+  MOZ_ASSERT(diff <=
+             (static_cast<unsigned>(bin->mRunSizePages) << gPageSize2Pow));
+  regind = diff / bin->mSizeDivisor;
+
+  MOZ_DIAGNOSTIC_ASSERT(diff == regind * size);
+  MOZ_DIAGNOSTIC_ASSERT(regind < bin->mRunNumRegions);
+
+  elm = regind >> (LOG2(sizeof(int)) + 3);
+  if (elm < run->mRegionsMinElement) {
+    run->mRegionsMinElement = elm;
+  }
+  bit = regind - (elm << (LOG2(sizeof(int)) + 3));
+  MOZ_RELEASE_ASSERT((run->mRegionsMask[elm] & (1U << bit)) == 0,
+                     "Double-free?");
+  run->mRegionsMask[elm] |= (1U << bit);
+}
+
+bool arena_t::SplitRun(arena_run_t* aRun, size_t aSize, bool aLarge,
+                       bool aZero) {
+  arena_chunk_t* chunk;
+  size_t old_ndirty, run_ind, total_pages, need_pages, rem_pages, i;
+
+  chunk = GetChunkForPtr(aRun);
+  old_ndirty = chunk->ndirty;
+  run_ind = (unsigned)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
+  total_pages = (chunk->map[run_ind].bits & ~gPageSizeMask) >> gPageSize2Pow;
+  need_pages = (aSize >> gPageSize2Pow);
+  MOZ_ASSERT(need_pages > 0);
+  MOZ_ASSERT(need_pages <= total_pages);
+  rem_pages = total_pages - need_pages;
+
+  for (i = 0; i < need_pages; i++) {
+    // Commit decommitted pages if necessary.  If a decommitted
+    // page is encountered, commit all needed adjacent decommitted
+    // pages in one operation, in order to reduce system call
+    // overhead.
+    if (chunk->map[run_ind + i].bits & CHUNK_MAP_MADVISED_OR_DECOMMITTED) {
+      size_t j;
+
+      // Advance i+j to just past the index of the last page
+      // to commit.  Clear CHUNK_MAP_DECOMMITTED and
+      // CHUNK_MAP_MADVISED along the way.
+      for (j = 0; i + j < need_pages && (chunk->map[run_ind + i + j].bits &
+                                         CHUNK_MAP_MADVISED_OR_DECOMMITTED);
+           j++) {
+        // DECOMMITTED and MADVISED are mutually exclusive.
+        MOZ_ASSERT(!(chunk->map[run_ind + i + j].bits & CHUNK_MAP_DECOMMITTED &&
+                     chunk->map[run_ind + i + j].bits & CHUNK_MAP_MADVISED));
+
+        chunk->map[run_ind + i + j].bits &= ~CHUNK_MAP_MADVISED_OR_DECOMMITTED;
+      }
+
+#ifdef MALLOC_DECOMMIT
+      bool committed = pages_commit(
+          (void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)),
+          j << gPageSize2Pow);
+      // pages_commit zeroes pages, so mark them as such if it succeeded.
+      // That's checked further below to avoid manually zeroing the pages.
+      for (size_t k = 0; k < j; k++) {
+        chunk->map[run_ind + i + k].bits |=
+            committed ? CHUNK_MAP_ZEROED : CHUNK_MAP_DECOMMITTED;
+      }
+      if (!committed) {
+        return false;
+      }
+#endif
+
+      mStats.committed += j;
+    }
+  }
+
+  mRunsAvail.Remove(&chunk->map[run_ind]);
+
+  // Keep track of trailing unused pages for later use.
+  if (rem_pages > 0) {
+    chunk->map[run_ind + need_pages].bits =
+        (rem_pages << gPageSize2Pow) |
+        (chunk->map[run_ind + need_pages].bits & gPageSizeMask);
+    chunk->map[run_ind + total_pages - 1].bits =
+        (rem_pages << gPageSize2Pow) |
+        (chunk->map[run_ind + total_pages - 1].bits & gPageSizeMask);
+    mRunsAvail.Insert(&chunk->map[run_ind + need_pages]);
+  }
+
+  for (i = 0; i < need_pages; i++) {
+    // Zero if necessary.
+    if (aZero) {
+      if ((chunk->map[run_ind + i].bits & CHUNK_MAP_ZEROED) == 0) {
+        memset((void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)), 0,
+               gPageSize);
+        // CHUNK_MAP_ZEROED is cleared below.
+      }
+    }
+
+    // Update dirty page accounting.
+    if (chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY) {
+      chunk->ndirty--;
+      mNumDirty--;
+      // CHUNK_MAP_DIRTY is cleared below.
+    }
+
+    // Initialize the chunk map.
+    if (aLarge) {
+      chunk->map[run_ind + i].bits = CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+    } else {
+      chunk->map[run_ind + i].bits = size_t(aRun) | CHUNK_MAP_ALLOCATED;
+    }
+  }
+
+  // Set the run size only in the first element for large runs.  This is
+  // primarily a debugging aid, since the lack of size info for trailing
+  // pages only matters if the application tries to operate on an
+  // interior pointer.
+  if (aLarge) {
+    chunk->map[run_ind].bits |= aSize;
+  }
+
+  if (chunk->ndirty == 0 && old_ndirty > 0) {
+    mChunksDirty.Remove(chunk);
+  }
+  return true;
+}
+
+void arena_t::InitChunk(arena_chunk_t* aChunk) {
+  size_t i;
+  // WARNING: The following relies on !aZeroed meaning "used to be an arena
+  // chunk".
+  // When the chunk we're initializating as an arena chunk is zeroed, we
+  // mark all runs are decommitted and zeroed.
+  // When it is not, which we can assume means it's a recycled arena chunk,
+  // all it can contain is an arena chunk header (which we're overwriting),
+  // and zeroed or poisoned memory (because a recycled arena chunk will
+  // have been emptied before being recycled). In that case, we can get
+  // away with reusing the chunk as-is, marking all runs as madvised.
+
+  size_t flags = CHUNK_MAP_DECOMMITTED | CHUNK_MAP_ZEROED;
+
+  mStats.mapped += kChunkSize;
+
+  aChunk->arena = this;
+
+  // Claim that no pages are in use, since the header is merely overhead.
+  aChunk->ndirty = 0;
+
+  // Initialize the map to contain one maximal free untouched run.
+  arena_run_t* run = (arena_run_t*)(uintptr_t(aChunk) +
+                                    (gChunkHeaderNumPages << gPageSize2Pow));
+
+  // Clear the bits for the real header pages.
+  for (i = 0; i < gChunkHeaderNumPages - 1; i++) {
+    aChunk->map[i].bits = 0;
+  }
+  // Mark the leading guard page (last header page) as decommitted.
+  aChunk->map[i++].bits = CHUNK_MAP_DECOMMITTED;
+
+  // Mark the area usable for runs as available, note size at start and end
+  aChunk->map[i++].bits = gMaxLargeClass | flags;
+  for (; i < gChunkNumPages - 2; i++) {
+    aChunk->map[i].bits = flags;
+  }
+  aChunk->map[gChunkNumPages - 2].bits = gMaxLargeClass | flags;
+
+  // Mark the trailing guard page as decommitted.
+  aChunk->map[gChunkNumPages - 1].bits = CHUNK_MAP_DECOMMITTED;
+
+#ifdef MALLOC_DECOMMIT
+  // Start out decommitted, in order to force a closer correspondence
+  // between dirty pages and committed untouched pages. This includes
+  // leading and trailing guard pages.
+  pages_decommit((void*)(uintptr_t(run) - gPageSize),
+                 gMaxLargeClass + 2 * gPageSize);
+#else
+  // Decommit the last header page (=leading page) as a guard.
+  pages_decommit((void*)(uintptr_t(run) - gPageSize), gPageSize);
+  // Decommit the last page as a guard.
+  pages_decommit((void*)(uintptr_t(aChunk) + kChunkSize - gPageSize),
+                 gPageSize);
+#endif
+
+  mStats.committed += gChunkHeaderNumPages - 1;
+
+  // Insert the run into the tree of available runs.
+  mRunsAvail.Insert(&aChunk->map[gChunkHeaderNumPages]);
+
+#ifdef MALLOC_DOUBLE_PURGE
+  new (&aChunk->chunks_madvised_elem) DoublyLinkedListElement<arena_chunk_t>();
+#endif
+}
+
+arena_chunk_t* arena_t::DeallocChunk(arena_chunk_t* aChunk) {
+  if (mSpare) {
+    if (mSpare->ndirty > 0) {
+      aChunk->arena->mChunksDirty.Remove(mSpare);
+      mNumDirty -= mSpare->ndirty;
+      mStats.committed -= mSpare->ndirty;
+    }
+
+#ifdef MALLOC_DOUBLE_PURGE
+    if (mChunksMAdvised.ElementProbablyInList(mSpare)) {
+      mChunksMAdvised.remove(mSpare);
+    }
+#endif
+
+    mStats.mapped -= kChunkSize;
+    mStats.committed -= gChunkHeaderNumPages - 1;
+  }
+
+  // Remove run from the tree of available runs, so that the arena does not use
+  // it. Dirty page flushing only uses the tree of dirty chunks, so leaving this
+  // chunk in the chunks_* trees is sufficient for that purpose.
+  mRunsAvail.Remove(&aChunk->map[gChunkHeaderNumPages]);
+
+  arena_chunk_t* chunk_dealloc = mSpare;
+  mSpare = aChunk;
+  return chunk_dealloc;
+}
+
+arena_run_t* arena_t::AllocRun(size_t aSize, bool aLarge, bool aZero) {
+  arena_run_t* run;
+  arena_chunk_map_t* mapelm;
+  arena_chunk_map_t key;
+
+  MOZ_ASSERT(aSize <= gMaxLargeClass);
+  MOZ_ASSERT((aSize & gPageSizeMask) == 0);
+
+  // Search the arena's chunks for the lowest best fit.
+  key.bits = aSize | CHUNK_MAP_KEY;
+  mapelm = mRunsAvail.SearchOrNext(&key);
+  if (mapelm) {
+    arena_chunk_t* chunk = GetChunkForPtr(mapelm);
+    size_t pageind =
+        (uintptr_t(mapelm) - uintptr_t(chunk->map)) / sizeof(arena_chunk_map_t);
+
+    run = (arena_run_t*)(uintptr_t(chunk) + (pageind << gPageSize2Pow));
+  } else if (mSpare) {
+    // Use the spare.
+    arena_chunk_t* chunk = mSpare;
+    mSpare = nullptr;
+    run = (arena_run_t*)(uintptr_t(chunk) +
+                         (gChunkHeaderNumPages << gPageSize2Pow));
+    // Insert the run into the tree of available runs.
+    mRunsAvail.Insert(&chunk->map[gChunkHeaderNumPages]);
+  } else {
+    // No usable runs.  Create a new chunk from which to allocate
+    // the run.
+    arena_chunk_t* chunk =
+        (arena_chunk_t*)chunk_alloc(kChunkSize, kChunkSize, false);
+    if (!chunk) {
+      return nullptr;
+    }
+
+    InitChunk(chunk);
+    run = (arena_run_t*)(uintptr_t(chunk) +
+                         (gChunkHeaderNumPages << gPageSize2Pow));
+  }
+  // Update page map.
+  return SplitRun(run, aSize, aLarge, aZero) ? run : nullptr;
+}
+
+size_t arena_t::EffectiveMaxDirty() {
+  int32_t modifier = gArenas.DefaultMaxDirtyPageModifier();
+  if (modifier) {
+    int32_t arenaOverride =
+        modifier > 0 ? mMaxDirtyIncreaseOverride : mMaxDirtyDecreaseOverride;
+    if (arenaOverride) {
+      modifier = arenaOverride;
+    }
+  }
+
+  return modifier >= 0 ? mMaxDirty << modifier : mMaxDirty >> -modifier;
+}
+
+void arena_t::Purge(size_t aMaxDirty) {
+  arena_chunk_t* chunk;
+  size_t i, npages;
+
+#ifdef MOZ_DEBUG
+  size_t ndirty = 0;
+  for (auto chunk : mChunksDirty.iter()) {
+    ndirty += chunk->ndirty;
+  }
+  MOZ_ASSERT(ndirty == mNumDirty);
+#endif
+  MOZ_DIAGNOSTIC_ASSERT(aMaxDirty == 1 || (mNumDirty > aMaxDirty));
+
+  // Iterate downward through chunks until enough dirty memory has been
+  // purged.  Terminate as soon as possible in order to minimize the
+  // number of system calls, even if a chunk has only been partially
+  // purged.
+  while (mNumDirty > (aMaxDirty >> 1)) {
+#ifdef MALLOC_DOUBLE_PURGE
+    bool madvised = false;
+#endif
+    chunk = mChunksDirty.Last();
+    MOZ_DIAGNOSTIC_ASSERT(chunk);
+    // Last page is DECOMMITTED as a guard page.
+    MOZ_ASSERT((chunk->map[gChunkNumPages - 1].bits & CHUNK_MAP_DECOMMITTED) !=
+               0);
+    for (i = gChunkNumPages - 2; chunk->ndirty > 0; i--) {
+      MOZ_DIAGNOSTIC_ASSERT(i >= gChunkHeaderNumPages);
+
+      if (chunk->map[i].bits & CHUNK_MAP_DIRTY) {
+#ifdef MALLOC_DECOMMIT
+        const size_t free_operation = CHUNK_MAP_DECOMMITTED;
+#else
+        const size_t free_operation = CHUNK_MAP_MADVISED;
+#endif
+        MOZ_ASSERT((chunk->map[i].bits & CHUNK_MAP_MADVISED_OR_DECOMMITTED) ==
+                   0);
+        chunk->map[i].bits ^= free_operation | CHUNK_MAP_DIRTY;
+        // Find adjacent dirty run(s).
+        for (npages = 1; i > gChunkHeaderNumPages &&
+                         (chunk->map[i - 1].bits & CHUNK_MAP_DIRTY);
+             npages++) {
+          i--;
+          MOZ_ASSERT((chunk->map[i].bits & CHUNK_MAP_MADVISED_OR_DECOMMITTED) ==
+                     0);
+          chunk->map[i].bits ^= free_operation | CHUNK_MAP_DIRTY;
+        }
+        chunk->ndirty -= npages;
+        mNumDirty -= npages;
+
+#ifdef MALLOC_DECOMMIT
+        pages_decommit((void*)(uintptr_t(chunk) + (i << gPageSize2Pow)),
+                       (npages << gPageSize2Pow));
+#else
+#  ifdef XP_SOLARIS
+        posix_madvise((void*)(uintptr_t(chunk) + (i << gPageSize2Pow)),
+                      (npages << gPageSize2Pow), MADV_FREE);
+#  else
+        madvise((void*)(uintptr_t(chunk) + (i << gPageSize2Pow)),
+                (npages << gPageSize2Pow), MADV_FREE);
+#  endif
+#  ifdef MALLOC_DOUBLE_PURGE
+        madvised = true;
+#  endif
+#endif
+        mStats.committed -= npages;
+
+        if (mNumDirty <= (aMaxDirty >> 1)) {
+          break;
+        }
+      }
+    }
+
+    if (chunk->ndirty == 0) {
+      mChunksDirty.Remove(chunk);
+    }
+#ifdef MALLOC_DOUBLE_PURGE
+    if (madvised) {
+      // The chunk might already be in the list, but this
+      // makes sure it's at the front.
+      if (mChunksMAdvised.ElementProbablyInList(chunk)) {
+        mChunksMAdvised.remove(chunk);
+      }
+      mChunksMAdvised.pushFront(chunk);
+    }
+#endif
+  }
+}
+
+arena_chunk_t* arena_t::DallocRun(arena_run_t* aRun, bool aDirty) {
+  arena_chunk_t* chunk;
+  size_t size, run_ind, run_pages;
+
+  chunk = GetChunkForPtr(aRun);
+  run_ind = (size_t)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
+  MOZ_DIAGNOSTIC_ASSERT(run_ind >= gChunkHeaderNumPages);
+  MOZ_RELEASE_ASSERT(run_ind < gChunkNumPages - 1);
+  if ((chunk->map[run_ind].bits & CHUNK_MAP_LARGE) != 0) {
+    size = chunk->map[run_ind].bits & ~gPageSizeMask;
+    run_pages = (size >> gPageSize2Pow);
+  } else {
+    run_pages = aRun->mBin->mRunSizePages;
+    size = run_pages << gPageSize2Pow;
+  }
+
+  // Mark pages as unallocated in the chunk map.
+  if (aDirty) {
+    size_t i;
+
+    for (i = 0; i < run_pages; i++) {
+      MOZ_DIAGNOSTIC_ASSERT((chunk->map[run_ind + i].bits & CHUNK_MAP_DIRTY) ==
+                            0);
+      chunk->map[run_ind + i].bits = CHUNK_MAP_DIRTY;
+    }
+
+    if (chunk->ndirty == 0) {
+      mChunksDirty.Insert(chunk);
+    }
+    chunk->ndirty += run_pages;
+    mNumDirty += run_pages;
+  } else {
+    size_t i;
+
+    for (i = 0; i < run_pages; i++) {
+      chunk->map[run_ind + i].bits &= ~(CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED);
+    }
+  }
+  chunk->map[run_ind].bits = size | (chunk->map[run_ind].bits & gPageSizeMask);
+  chunk->map[run_ind + run_pages - 1].bits =
+      size | (chunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
+
+  // Try to coalesce forward.
+  if (run_ind + run_pages < gChunkNumPages - 1 &&
+      (chunk->map[run_ind + run_pages].bits & CHUNK_MAP_ALLOCATED) == 0) {
+    size_t nrun_size = chunk->map[run_ind + run_pages].bits & ~gPageSizeMask;
+
+    // Remove successor from tree of available runs; the coalesced run is
+    // inserted later.
+    mRunsAvail.Remove(&chunk->map[run_ind + run_pages]);
+
+    size += nrun_size;
+    run_pages = size >> gPageSize2Pow;
+
+    MOZ_DIAGNOSTIC_ASSERT((chunk->map[run_ind + run_pages - 1].bits &
+                           ~gPageSizeMask) == nrun_size);
+    chunk->map[run_ind].bits =
+        size | (chunk->map[run_ind].bits & gPageSizeMask);
+    chunk->map[run_ind + run_pages - 1].bits =
+        size | (chunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
+  }
+
+  // Try to coalesce backward.
+  if (run_ind > gChunkHeaderNumPages &&
+      (chunk->map[run_ind - 1].bits & CHUNK_MAP_ALLOCATED) == 0) {
+    size_t prun_size = chunk->map[run_ind - 1].bits & ~gPageSizeMask;
+
+    run_ind -= prun_size >> gPageSize2Pow;
+
+    // Remove predecessor from tree of available runs; the coalesced run is
+    // inserted later.
+    mRunsAvail.Remove(&chunk->map[run_ind]);
+
+    size += prun_size;
+    run_pages = size >> gPageSize2Pow;
+
+    MOZ_DIAGNOSTIC_ASSERT((chunk->map[run_ind].bits & ~gPageSizeMask) ==
+                          prun_size);
+    chunk->map[run_ind].bits =
+        size | (chunk->map[run_ind].bits & gPageSizeMask);
+    chunk->map[run_ind + run_pages - 1].bits =
+        size | (chunk->map[run_ind + run_pages - 1].bits & gPageSizeMask);
+  }
+
+  // Insert into tree of available runs, now that coalescing is complete.
+  mRunsAvail.Insert(&chunk->map[run_ind]);
+
+  // Deallocate chunk if it is now completely unused.
+  arena_chunk_t* chunk_dealloc = nullptr;
+  if ((chunk->map[gChunkHeaderNumPages].bits &
+       (~gPageSizeMask | CHUNK_MAP_ALLOCATED)) == gMaxLargeClass) {
+    chunk_dealloc = DeallocChunk(chunk);
+  }
+
+  size_t maxDirty = EffectiveMaxDirty();
+  if (mNumDirty > maxDirty) {
+    Purge(maxDirty);
+  }
+
+  return chunk_dealloc;
+}
+
+void arena_t::TrimRunHead(arena_chunk_t* aChunk, arena_run_t* aRun,
+                          size_t aOldSize, size_t aNewSize) {
+  size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
+  size_t head_npages = (aOldSize - aNewSize) >> gPageSize2Pow;
+
+  MOZ_ASSERT(aOldSize > aNewSize);
+
+  // Update the chunk map so that arena_t::RunDalloc() can treat the
+  // leading run as separately allocated.
+  aChunk->map[pageind].bits =
+      (aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+  aChunk->map[pageind + head_npages].bits =
+      aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+
+#ifdef MOZ_DEBUG
+  arena_chunk_t* no_chunk =
+#endif
+      DallocRun(aRun, false);
+  // This will never release a chunk as there's still at least one allocated
+  // run.
+  MOZ_ASSERT(!no_chunk);
+}
+
+void arena_t::TrimRunTail(arena_chunk_t* aChunk, arena_run_t* aRun,
+                          size_t aOldSize, size_t aNewSize, bool aDirty) {
+  size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
+  size_t npages = aNewSize >> gPageSize2Pow;
+
+  MOZ_ASSERT(aOldSize > aNewSize);
+
+  // Update the chunk map so that arena_t::RunDalloc() can treat the
+  // trailing run as separately allocated.
+  aChunk->map[pageind].bits = aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+  aChunk->map[pageind + npages].bits =
+      (aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+
+#ifdef MOZ_DEBUG
+  arena_chunk_t* no_chunk =
+#endif
+      DallocRun((arena_run_t*)(uintptr_t(aRun) + aNewSize), aDirty);
+
+  // This will never release a chunk as there's still at least one allocated
+  // run.
+  MOZ_ASSERT(!no_chunk);
+}
+
+arena_run_t* arena_t::GetNonFullBinRun(arena_bin_t* aBin) {
+  arena_chunk_map_t* mapelm;
+  arena_run_t* run;
+  unsigned i, remainder;
+
+  // Look for a usable run.
+  mapelm = aBin->mNonFullRuns.First();
+  if (mapelm) {
+    // run is guaranteed to have available space.
+    aBin->mNonFullRuns.Remove(mapelm);
+    run = (arena_run_t*)(mapelm->bits & ~gPageSizeMask);
+    return run;
+  }
+  // No existing runs have any space available.
+
+  // Allocate a new run.
+  run = AllocRun(static_cast<size_t>(aBin->mRunSizePages) << gPageSize2Pow,
+                 false, false);
+  if (!run) {
+    return nullptr;
+  }
+  // Don't initialize if a race in arena_t::RunAlloc() allowed an existing
+  // run to become usable.
+  if (run == aBin->mCurrentRun) {
+    return run;
+  }
+
+  // Initialize run internals.
+  run->mBin = aBin;
+
+  for (i = 0; i < aBin->mRunNumRegionsMask - 1; i++) {
+    run->mRegionsMask[i] = UINT_MAX;
+  }
+  remainder = aBin->mRunNumRegions & ((1U << (LOG2(sizeof(int)) + 3)) - 1);
+  if (remainder == 0) {
+    run->mRegionsMask[i] = UINT_MAX;
+  } else {
+    // The last element has spare bits that need to be unset.
+    run->mRegionsMask[i] =
+        (UINT_MAX >> ((1U << (LOG2(sizeof(int)) + 3)) - remainder));
+  }
+
+  run->mRegionsMinElement = 0;
+
+  run->mNumFree = aBin->mRunNumRegions;
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+  run->mMagic = ARENA_RUN_MAGIC;
+#endif
+
+  aBin->mNumRuns++;
+  return run;
+}
+
+void arena_bin_t::Init(SizeClass aSizeClass) {
+  size_t try_run_size;
+  unsigned try_nregs, try_mask_nelms, try_reg0_offset;
+  // Size of the run header, excluding mRegionsMask.
+  static const size_t kFixedHeaderSize = offsetof(arena_run_t, mRegionsMask);
+
+  MOZ_ASSERT(aSizeClass.Size() <= gMaxBinClass);
+
+  try_run_size = gPageSize;
+
+  mCurrentRun = nullptr;
+  mNonFullRuns.Init();
+  mSizeClass = aSizeClass.Size();
+  mNumRuns = 0;
+
+  // Run size expansion loop.
+  while (true) {
+    try_nregs = ((try_run_size - kFixedHeaderSize) / mSizeClass) +
+                1;  // Counter-act try_nregs-- in loop.
+
+    // The do..while loop iteratively reduces the number of regions until
+    // the run header and the regions no longer overlap.  A closed formula
+    // would be quite messy, since there is an interdependency between the
+    // header's mask length and the number of regions.
+    do {
+      try_nregs--;
+      try_mask_nelms =
+          (try_nregs >> (LOG2(sizeof(int)) + 3)) +
+          ((try_nregs & ((1U << (LOG2(sizeof(int)) + 3)) - 1)) ? 1 : 0);
+      try_reg0_offset = try_run_size - (try_nregs * mSizeClass);
+    } while (kFixedHeaderSize + (sizeof(unsigned) * try_mask_nelms) >
+             try_reg0_offset);
+
+    // Try to keep the run overhead below kRunOverhead.
+    if (Fraction(try_reg0_offset, try_run_size) <= kRunOverhead) {
+      break;
+    }
+
+    // If the overhead is larger than the size class, it means the size class
+    // is small and doesn't align very well with the header. It's desirable to
+    // have smaller run sizes for them, so relax the overhead requirement.
+    if (try_reg0_offset > mSizeClass) {
+      if (Fraction(try_reg0_offset, try_run_size) <= kRunRelaxedOverhead) {
+        break;
+      }
+    }
+
+    // The run header includes one bit per region of the given size. For sizes
+    // small enough, the number of regions is large enough that growing the run
+    // size barely moves the needle for the overhead because of all those bits.
+    // For example, for a size of 8 bytes, adding 4KiB to the run size adds
+    // close to 512 bits to the header, which is 64 bytes.
+    // With such overhead, there is no way to get to the wanted overhead above,
+    // so we give up if the required size for mRegionsMask more than doubles the
+    // size of the run header.
+    if (try_mask_nelms * sizeof(unsigned) >= kFixedHeaderSize) {
+      break;
+    }
+
+    // If next iteration is going to be larger than the largest possible large
+    // size class, then we didn't find a setup where the overhead is small
+    // enough, and we can't do better than the current settings, so just use
+    // that.
+    if (try_run_size + gPageSize > gMaxLargeClass) {
+      break;
+    }
+
+    // Try more aggressive settings.
+    try_run_size += gPageSize;
+  }
+
+  MOZ_ASSERT(kFixedHeaderSize + (sizeof(unsigned) * try_mask_nelms) <=
+             try_reg0_offset);
+  MOZ_ASSERT((try_mask_nelms << (LOG2(sizeof(int)) + 3)) >= try_nregs);
+
+  // Copy final settings.
+  MOZ_ASSERT((try_run_size >> gPageSize2Pow) <= UINT8_MAX);
+  mRunSizePages = static_cast<uint8_t>(try_run_size >> gPageSize2Pow);
+  mRunNumRegions = try_nregs;
+  mRunNumRegionsMask = try_mask_nelms;
+  mRunFirstRegionOffset = try_reg0_offset;
+  mSizeDivisor = FastDivisor<uint16_t>(aSizeClass.Size(), try_run_size);
+}
+
+void* arena_t::MallocSmall(size_t aSize, bool aZero) {
+  void* ret;
+  arena_bin_t* bin;
+  arena_run_t* run;
+  SizeClass sizeClass(aSize);
+  aSize = sizeClass.Size();
+
+  switch (sizeClass.Type()) {
+    case SizeClass::Tiny:
+      bin = &mBins[FloorLog2(aSize / kMinTinyClass)];
+      break;
+    case SizeClass::Quantum:
+      // Although we divide 2 things by kQuantum, the compiler will
+      // reduce `kMinQuantumClass / kQuantum` and `kNumTinyClasses` to a
+      // single constant.
+      bin = &mBins[kNumTinyClasses + (aSize / kQuantum) -
+                   (kMinQuantumClass / kQuantum)];
+      break;
+    case SizeClass::QuantumWide:
+      bin =
+          &mBins[kNumTinyClasses + kNumQuantumClasses + (aSize / kQuantumWide) -
+                 (kMinQuantumWideClass / kQuantumWide)];
+      break;
+    case SizeClass::SubPage:
+      bin =
+          &mBins[kNumTinyClasses + kNumQuantumClasses + kNumQuantumWideClasses +
+                 (FloorLog2(aSize) - LOG2(kMinSubPageClass))];
+      break;
+    default:
+      MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected size class type");
+  }
+  MOZ_DIAGNOSTIC_ASSERT(aSize == bin->mSizeClass);
+
+  {
+    // Before we lock, we determine if we need to randomize the allocation
+    // because if we do, we need to create the PRNG which might require
+    // allocating memory (arc4random on OSX for example) and we need to
+    // avoid the deadlock
+    if (MOZ_UNLIKELY(mRandomizeSmallAllocations && mPRNG == nullptr)) {
+      // This is frustrating. Because the code backing RandomUint64 (arc4random
+      // for example) may allocate memory, and because
+      // mRandomizeSmallAllocations is true and we haven't yet initilized mPRNG,
+      // we would re-enter this same case and cause a deadlock inside e.g.
+      // arc4random.  So we temporarily disable mRandomizeSmallAllocations to
+      // skip this case and then re-enable it
+      mRandomizeSmallAllocations = false;
+      mozilla::Maybe<uint64_t> prngState1 = mozilla::RandomUint64();
+      mozilla::Maybe<uint64_t> prngState2 = mozilla::RandomUint64();
+      void* backing =
+          base_alloc(sizeof(mozilla::non_crypto::XorShift128PlusRNG));
+      mPRNG = new (backing) mozilla::non_crypto::XorShift128PlusRNG(
+          prngState1.valueOr(0), prngState2.valueOr(0));
+      mRandomizeSmallAllocations = true;
+    }
+    MOZ_ASSERT(!mRandomizeSmallAllocations || mPRNG);
+
+    MaybeMutexAutoLock lock(mLock);
+    run = bin->mCurrentRun;
+    if (MOZ_UNLIKELY(!run || run->mNumFree == 0)) {
+      run = bin->mCurrentRun = GetNonFullBinRun(bin);
+    }
+    if (MOZ_UNLIKELY(!run)) {
+      return nullptr;
+    }
+    MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
+    MOZ_DIAGNOSTIC_ASSERT(run->mNumFree > 0);
+    ret = ArenaRunRegAlloc(run, bin);
+    MOZ_DIAGNOSTIC_ASSERT(ret);
+    run->mNumFree--;
+    if (!ret) {
+      return nullptr;
+    }
+
+    mStats.allocated_small += aSize;
+  }
+
+  if (!aZero) {
+    ApplyZeroOrJunk(ret, aSize);
+  } else {
+    memset(ret, 0, aSize);
+  }
+
+  return ret;
+}
+
+void* arena_t::MallocLarge(size_t aSize, bool aZero) {
+  void* ret;
+
+  // Large allocation.
+  aSize = PAGE_CEILING(aSize);
+
+  {
+    MaybeMutexAutoLock lock(mLock);
+    ret = AllocRun(aSize, true, aZero);
+    if (!ret) {
+      return nullptr;
+    }
+    mStats.allocated_large += aSize;
+  }
+
+  if (!aZero) {
+    ApplyZeroOrJunk(ret, aSize);
+  }
+
+  return ret;
+}
+
+void* arena_t::Malloc(size_t aSize, bool aZero) {
+  MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
+  MOZ_ASSERT(aSize != 0);
+
+  if (aSize <= gMaxBinClass) {
+    return MallocSmall(aSize, aZero);
+  }
+  if (aSize <= gMaxLargeClass) {
+    return MallocLarge(aSize, aZero);
+  }
+  return MallocHuge(aSize, aZero);
+}
+
+// Only handles large allocations that require more than page alignment.
+void* arena_t::PallocLarge(size_t aAlignment, size_t aSize, size_t aAllocSize) {
+  void* ret;
+  size_t offset;
+  arena_chunk_t* chunk;
+
+  MOZ_ASSERT((aSize & gPageSizeMask) == 0);
+  MOZ_ASSERT((aAlignment & gPageSizeMask) == 0);
+
+  {
+    MaybeMutexAutoLock lock(mLock);
+    ret = AllocRun(aAllocSize, true, false);
+    if (!ret) {
+      return nullptr;
+    }
+
+    chunk = GetChunkForPtr(ret);
+
+    offset = uintptr_t(ret) & (aAlignment - 1);
+    MOZ_ASSERT((offset & gPageSizeMask) == 0);
+    MOZ_ASSERT(offset < aAllocSize);
+    if (offset == 0) {
+      TrimRunTail(chunk, (arena_run_t*)ret, aAllocSize, aSize, false);
+    } else {
+      size_t leadsize, trailsize;
+
+      leadsize = aAlignment - offset;
+      if (leadsize > 0) {
+        TrimRunHead(chunk, (arena_run_t*)ret, aAllocSize,
+                    aAllocSize - leadsize);
+        ret = (void*)(uintptr_t(ret) + leadsize);
+      }
+
+      trailsize = aAllocSize - leadsize - aSize;
+      if (trailsize != 0) {
+        // Trim trailing space.
+        MOZ_ASSERT(trailsize < aAllocSize);
+        TrimRunTail(chunk, (arena_run_t*)ret, aSize + trailsize, aSize, false);
+      }
+    }
+
+    mStats.allocated_large += aSize;
+  }
+
+  ApplyZeroOrJunk(ret, aSize);
+  return ret;
+}
+
+void* arena_t::Palloc(size_t aAlignment, size_t aSize) {
+  void* ret;
+  size_t ceil_size;
+
+  // Round size up to the nearest multiple of alignment.
+  //
+  // This done, we can take advantage of the fact that for each small
+  // size class, every object is aligned at the smallest power of two
+  // that is non-zero in the base two representation of the size.  For
+  // example:
+  //
+  //   Size |   Base 2 | Minimum alignment
+  //   -----+----------+------------------
+  //     96 |  1100000 |  32
+  //    144 | 10100000 |  32
+  //    192 | 11000000 |  64
+  //
+  // Depending on runtime settings, it is possible that arena_malloc()
+  // will further round up to a power of two, but that never causes
+  // correctness issues.
+  ceil_size = ALIGNMENT_CEILING(aSize, aAlignment);
+
+  // (ceil_size < aSize) protects against the combination of maximal
+  // alignment and size greater than maximal alignment.
+  if (ceil_size < aSize) {
+    // size_t overflow.
+    return nullptr;
+  }
+
+  if (ceil_size <= gPageSize ||
+      (aAlignment <= gPageSize && ceil_size <= gMaxLargeClass)) {
+    ret = Malloc(ceil_size, false);
+  } else {
+    size_t run_size;
+
+    // We can't achieve sub-page alignment, so round up alignment
+    // permanently; it makes later calculations simpler.
+    aAlignment = PAGE_CEILING(aAlignment);
+    ceil_size = PAGE_CEILING(aSize);
+
+    // (ceil_size < aSize) protects against very large sizes within
+    // pagesize of SIZE_T_MAX.
+    //
+    // (ceil_size + aAlignment < ceil_size) protects against the
+    // combination of maximal alignment and ceil_size large enough
+    // to cause overflow.  This is similar to the first overflow
+    // check above, but it needs to be repeated due to the new
+    // ceil_size value, which may now be *equal* to maximal
+    // alignment, whereas before we only detected overflow if the
+    // original size was *greater* than maximal alignment.
+    if (ceil_size < aSize || ceil_size + aAlignment < ceil_size) {
+      // size_t overflow.
+      return nullptr;
+    }
+
+    // Calculate the size of the over-size run that arena_palloc()
+    // would need to allocate in order to guarantee the alignment.
+    if (ceil_size >= aAlignment) {
+      run_size = ceil_size + aAlignment - gPageSize;
+    } else {
+      // It is possible that (aAlignment << 1) will cause
+      // overflow, but it doesn't matter because we also
+      // subtract pagesize, which in the case of overflow
+      // leaves us with a very large run_size.  That causes
+      // the first conditional below to fail, which means
+      // that the bogus run_size value never gets used for
+      // anything important.
+      run_size = (aAlignment << 1) - gPageSize;
+    }
+
+    if (run_size <= gMaxLargeClass) {
+      ret = PallocLarge(aAlignment, ceil_size, run_size);
+    } else if (aAlignment <= kChunkSize) {
+      ret = MallocHuge(ceil_size, false);
+    } else {
+      ret = PallocHuge(ceil_size, aAlignment, false);
+    }
+  }
+
+  MOZ_ASSERT((uintptr_t(ret) & (aAlignment - 1)) == 0);
+  return ret;
+}
+
+class AllocInfo {
+ public:
+  template <bool Validate = false>
+  static inline AllocInfo Get(const void* aPtr) {
+    // If the allocator is not initialized, the pointer can't belong to it.
+    if (Validate && !malloc_initialized) {
+      return AllocInfo();
+    }
+
+    auto chunk = GetChunkForPtr(aPtr);
+    if (Validate) {
+      if (!chunk || !gChunkRTree.Get(chunk)) {
+        return AllocInfo();
+      }
+    }
+
+    if (chunk != aPtr) {
+      MOZ_DIAGNOSTIC_ASSERT(chunk->arena->mMagic == ARENA_MAGIC);
+      size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
+      return GetInChunk(aPtr, chunk, pageind);
+    }
+
+    extent_node_t key;
+
+    // Huge allocation
+    key.mAddr = chunk;
+    MutexAutoLock lock(huge_mtx);
+    extent_node_t* node = huge.Search(&key);
+    if (Validate && !node) {
+      return AllocInfo();
+    }
+    return AllocInfo(node->mSize, node);
+  }
+
+  // Get the allocation information for a pointer we know is within a chunk
+  // (Small or large, not huge).
+  static inline AllocInfo GetInChunk(const void* aPtr, arena_chunk_t* aChunk,
+                                     size_t pageind) {
+    size_t mapbits = aChunk->map[pageind].bits;
+    MOZ_DIAGNOSTIC_ASSERT((mapbits & CHUNK_MAP_ALLOCATED) != 0);
+
+    size_t size;
+    if ((mapbits & CHUNK_MAP_LARGE) == 0) {
+      arena_run_t* run = (arena_run_t*)(mapbits & ~gPageSizeMask);
+      MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
+      size = run->mBin->mSizeClass;
+    } else {
+      size = mapbits & ~gPageSizeMask;
+      MOZ_DIAGNOSTIC_ASSERT(size != 0);
+    }
+
+    return AllocInfo(size, aChunk);
+  }
+
+  // Validate ptr before assuming that it points to an allocation.  Currently,
+  // the following validation is performed:
+  //
+  // + Check that ptr is not nullptr.
+  //
+  // + Check that ptr lies within a mapped chunk.
+  static inline AllocInfo GetValidated(const void* aPtr) {
+    return Get<true>(aPtr);
+  }
+
+  AllocInfo() : mSize(0), mChunk(nullptr) {}
+
+  explicit AllocInfo(size_t aSize, arena_chunk_t* aChunk)
+      : mSize(aSize), mChunk(aChunk) {
+    MOZ_ASSERT(mSize <= gMaxLargeClass);
+  }
+
+  explicit AllocInfo(size_t aSize, extent_node_t* aNode)
+      : mSize(aSize), mNode(aNode) {
+    MOZ_ASSERT(mSize > gMaxLargeClass);
+  }
+
+  size_t Size() { return mSize; }
+
+  arena_t* Arena() {
+    if (mSize <= gMaxLargeClass) {
+      return mChunk->arena;
+    }
+    // Best effort detection that we're not trying to access an already
+    // disposed arena. In the case of a disposed arena, the memory location
+    // pointed by mNode->mArena is either free (but still a valid memory
+    // region, per TypedBaseAlloc<arena_t>), in which case its id was reset,
+    // or has been reallocated for a new region, and its id is very likely
+    // different (per randomness). In both cases, the id is unlikely to
+    // match what it was for the disposed arena.
+    MOZ_RELEASE_ASSERT(mNode->mArenaId == mNode->mArena->mId);
+    return mNode->mArena;
+  }
+
+  bool IsValid() const { return !!mSize; }
+
+ private:
+  size_t mSize;
+  union {
+    // Pointer to the chunk associated with the allocation for small
+    // and large allocations.
+    arena_chunk_t* mChunk;
+
+    // Pointer to the extent node for huge allocations.
+    extent_node_t* mNode;
+  };
+};
+
+inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
+                                           jemalloc_ptr_info_t* aInfo) {
+  arena_chunk_t* chunk = GetChunkForPtr(aPtr);
+
+  // Is the pointer null, or within one chunk's size of null?
+  // Alternatively, if the allocator is not initialized yet, the pointer
+  // can't be known.
+  if (!chunk || !malloc_initialized) {
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+    return;
+  }
+
+  // Look for huge allocations before looking for |chunk| in gChunkRTree.
+  // This is necessary because |chunk| won't be in gChunkRTree if it's
+  // the second or subsequent chunk in a huge allocation.
+  extent_node_t* node;
+  extent_node_t key;
+  {
+    MutexAutoLock lock(huge_mtx);
+    key.mAddr = const_cast<void*>(aPtr);
+    node =
+        reinterpret_cast<RedBlackTree<extent_node_t, ExtentTreeBoundsTrait>*>(
+            &huge)
+            ->Search(&key);
+    if (node) {
+      *aInfo = {TagLiveAlloc, node->mAddr, node->mSize, node->mArena->mId};
+      return;
+    }
+  }
+
+  // It's not a huge allocation. Check if we have a known chunk.
+  if (!gChunkRTree.Get(chunk)) {
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(chunk->arena->mMagic == ARENA_MAGIC);
+
+  // Get the page number within the chunk.
+  size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
+  if (pageind < gChunkHeaderNumPages) {
+    // Within the chunk header.
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+    return;
+  }
+
+  size_t mapbits = chunk->map[pageind].bits;
+
+  if (!(mapbits & CHUNK_MAP_ALLOCATED)) {
+    void* pageaddr = (void*)(uintptr_t(aPtr) & ~gPageSizeMask);
+    *aInfo = {TagFreedPage, pageaddr, gPageSize, chunk->arena->mId};
+    return;
+  }
+
+  if (mapbits & CHUNK_MAP_LARGE) {
+    // It's a large allocation. Only the first page of a large
+    // allocation contains its size, so if the address is not in
+    // the first page, scan back to find the allocation size.
+    size_t size;
+    while (true) {
+      size = mapbits & ~gPageSizeMask;
+      if (size != 0) {
+        break;
+      }
+
+      // The following two return paths shouldn't occur in
+      // practice unless there is heap corruption.
+      pageind--;
+      MOZ_DIAGNOSTIC_ASSERT(pageind >= gChunkHeaderNumPages);
+      if (pageind < gChunkHeaderNumPages) {
+        *aInfo = {TagUnknown, nullptr, 0, 0};
+        return;
+      }
+
+      mapbits = chunk->map[pageind].bits;
+      MOZ_DIAGNOSTIC_ASSERT(mapbits & CHUNK_MAP_LARGE);
+      if (!(mapbits & CHUNK_MAP_LARGE)) {
+        *aInfo = {TagUnknown, nullptr, 0, 0};
+        return;
+      }
+    }
+
+    void* addr = ((char*)chunk) + (pageind << gPageSize2Pow);
+    *aInfo = {TagLiveAlloc, addr, size, chunk->arena->mId};
+    return;
+  }
+
+  // It must be a small allocation.
+  auto run = (arena_run_t*)(mapbits & ~gPageSizeMask);
+  MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
+
+  // The allocation size is stored in the run metadata.
+  size_t size = run->mBin->mSizeClass;
+
+  // Address of the first possible pointer in the run after its headers.
+  uintptr_t reg0_addr = (uintptr_t)run + run->mBin->mRunFirstRegionOffset;
+  if (aPtr < (void*)reg0_addr) {
+    // In the run header.
+    *aInfo = {TagUnknown, nullptr, 0, 0};
+    return;
+  }
+
+  // Position in the run.
+  unsigned regind = ((uintptr_t)aPtr - reg0_addr) / size;
+
+  // Pointer to the allocation's base address.
+  void* addr = (void*)(reg0_addr + regind * size);
+
+  // Check if the allocation has been freed.
+  unsigned elm = regind >> (LOG2(sizeof(int)) + 3);
+  unsigned bit = regind - (elm << (LOG2(sizeof(int)) + 3));
+  PtrInfoTag tag =
+      ((run->mRegionsMask[elm] & (1U << bit))) ? TagFreedAlloc : TagLiveAlloc;
+
+  *aInfo = {tag, addr, size, chunk->arena->mId};
+}
+
+namespace Debug {
+// Helper for debuggers. We don't want it to be inlined and optimized out.
+MOZ_NEVER_INLINE jemalloc_ptr_info_t* jemalloc_ptr_info(const void* aPtr) {
+  static jemalloc_ptr_info_t info;
+  MozJemalloc::jemalloc_ptr_info(aPtr, &info);
+  return &info;
+}
+}  // namespace Debug
+
+arena_chunk_t* arena_t::DallocSmall(arena_chunk_t* aChunk, void* aPtr,
+                                    arena_chunk_map_t* aMapElm) {
+  arena_run_t* run;
+  arena_bin_t* bin;
+  size_t size;
+
+  run = (arena_run_t*)(aMapElm->bits & ~gPageSizeMask);
+  MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
+  bin = run->mBin;
+  size = bin->mSizeClass;
+  MOZ_DIAGNOSTIC_ASSERT(uintptr_t(aPtr) >=
+                        uintptr_t(run) + bin->mRunFirstRegionOffset);
+
+  arena_run_reg_dalloc(run, bin, aPtr, size);
+  run->mNumFree++;
+  arena_chunk_t* dealloc_chunk = nullptr;
+
+  if (run->mNumFree == bin->mRunNumRegions) {
+    // Deallocate run.
+    if (run == bin->mCurrentRun) {
+      bin->mCurrentRun = nullptr;
+    } else if (bin->mRunNumRegions != 1) {
+      size_t run_pageind =
+          (uintptr_t(run) - uintptr_t(aChunk)) >> gPageSize2Pow;
+      arena_chunk_map_t* run_mapelm = &aChunk->map[run_pageind];
+
+      // This block's conditional is necessary because if the
+      // run only contains one region, then it never gets
+      // inserted into the non-full runs tree.
+      MOZ_DIAGNOSTIC_ASSERT(bin->mNonFullRuns.Search(run_mapelm) == run_mapelm);
+      bin->mNonFullRuns.Remove(run_mapelm);
+    }
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+    run->mMagic = 0;
+#endif
+    dealloc_chunk = DallocRun(run, true);
+    bin->mNumRuns--;
+  } else if (run->mNumFree == 1 && run != bin->mCurrentRun) {
+    // Make sure that bin->mCurrentRun always refers to the lowest
+    // non-full run, if one exists.
+    if (!bin->mCurrentRun) {
+      bin->mCurrentRun = run;
+    } else if (uintptr_t(run) < uintptr_t(bin->mCurrentRun)) {
+      // Switch mCurrentRun.
+      if (bin->mCurrentRun->mNumFree > 0) {
+        arena_chunk_t* runcur_chunk = GetChunkForPtr(bin->mCurrentRun);
+        size_t runcur_pageind =
+            (uintptr_t(bin->mCurrentRun) - uintptr_t(runcur_chunk)) >>
+            gPageSize2Pow;
+        arena_chunk_map_t* runcur_mapelm = &runcur_chunk->map[runcur_pageind];
+
+        // Insert runcur.
+        MOZ_DIAGNOSTIC_ASSERT(!bin->mNonFullRuns.Search(runcur_mapelm));
+        bin->mNonFullRuns.Insert(runcur_mapelm);
+      }
+      bin->mCurrentRun = run;
+    } else {
+      size_t run_pageind =
+          (uintptr_t(run) - uintptr_t(aChunk)) >> gPageSize2Pow;
+      arena_chunk_map_t* run_mapelm = &aChunk->map[run_pageind];
+
+      MOZ_DIAGNOSTIC_ASSERT(bin->mNonFullRuns.Search(run_mapelm) == nullptr);
+      bin->mNonFullRuns.Insert(run_mapelm);
+    }
+  }
+  mStats.allocated_small -= size;
+
+  return dealloc_chunk;
+}
+
+arena_chunk_t* arena_t::DallocLarge(arena_chunk_t* aChunk, void* aPtr) {
+  MOZ_DIAGNOSTIC_ASSERT((uintptr_t(aPtr) & gPageSizeMask) == 0);
+  size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
+  size_t size = aChunk->map[pageind].bits & ~gPageSizeMask;
+
+  mStats.allocated_large -= size;
+
+  return DallocRun((arena_run_t*)aPtr, true);
+}
+
+static inline void arena_dalloc(void* aPtr, size_t aOffset, arena_t* aArena) {
+  MOZ_ASSERT(aPtr);
+  MOZ_ASSERT(aOffset != 0);
+  MOZ_ASSERT(GetChunkOffsetForPtr(aPtr) == aOffset);
+
+  auto chunk = (arena_chunk_t*)((uintptr_t)aPtr - aOffset);
+  auto arena = chunk->arena;
+  MOZ_ASSERT(arena);
+  MOZ_DIAGNOSTIC_ASSERT(arena->mMagic == ARENA_MAGIC);
+  MOZ_RELEASE_ASSERT(!aArena || arena == aArena);
+
+  size_t pageind = aOffset >> gPageSize2Pow;
+  if (opt_poison) {
+    AllocInfo info = AllocInfo::GetInChunk(aPtr, chunk, pageind);
+    MOZ_ASSERT(info.IsValid());
+    MaybePoison(aPtr, info.Size());
+  }
+
+  arena_chunk_t* chunk_dealloc_delay = nullptr;
+
+  {
+    MaybeMutexAutoLock lock(arena->mLock);
+    arena_chunk_map_t* mapelm = &chunk->map[pageind];
+    MOZ_RELEASE_ASSERT((mapelm->bits & CHUNK_MAP_DECOMMITTED) == 0,
+                       "Freeing in decommitted page.");
+    MOZ_RELEASE_ASSERT((mapelm->bits & CHUNK_MAP_ALLOCATED) != 0,
+                       "Double-free?");
+    if ((mapelm->bits & CHUNK_MAP_LARGE) == 0) {
+      // Small allocation.
+      chunk_dealloc_delay = arena->DallocSmall(chunk, aPtr, mapelm);
+    } else {
+      // Large allocation.
+      chunk_dealloc_delay = arena->DallocLarge(chunk, aPtr);
+    }
+  }
+
+  if (chunk_dealloc_delay) {
+    chunk_dealloc((void*)chunk_dealloc_delay, kChunkSize, ARENA_CHUNK);
+  }
+}
+
+static inline void idalloc(void* ptr, arena_t* aArena) {
+  size_t offset;
+
+  MOZ_ASSERT(ptr);
+
+  offset = GetChunkOffsetForPtr(ptr);
+  if (offset != 0) {
+    arena_dalloc(ptr, offset, aArena);
+  } else {
+    huge_dalloc(ptr, aArena);
+  }
+}
+
+void arena_t::RallocShrinkLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
+                                size_t aOldSize) {
+  MOZ_ASSERT(aSize < aOldSize);
+
+  // Shrink the run, and make trailing pages available for other
+  // allocations.
+  MaybeMutexAutoLock lock(mLock);
+  TrimRunTail(aChunk, (arena_run_t*)aPtr, aOldSize, aSize, true);
+  mStats.allocated_large -= aOldSize - aSize;
+}
+
+// Returns whether reallocation was successful.
+bool arena_t::RallocGrowLarge(arena_chunk_t* aChunk, void* aPtr, size_t aSize,
+                              size_t aOldSize) {
+  size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
+  size_t npages = aOldSize >> gPageSize2Pow;
+
+  MaybeMutexAutoLock lock(mLock);
+  MOZ_DIAGNOSTIC_ASSERT(aOldSize ==
+                        (aChunk->map[pageind].bits & ~gPageSizeMask));
+
+  // Try to extend the run.
+  MOZ_ASSERT(aSize > aOldSize);
+  if (pageind + npages < gChunkNumPages - 1 &&
+      (aChunk->map[pageind + npages].bits & CHUNK_MAP_ALLOCATED) == 0 &&
+      (aChunk->map[pageind + npages].bits & ~gPageSizeMask) >=
+          aSize - aOldSize) {
+    // The next run is available and sufficiently large.  Split the
+    // following run, then merge the first part with the existing
+    // allocation.
+    if (!SplitRun((arena_run_t*)(uintptr_t(aChunk) +
+                                 ((pageind + npages) << gPageSize2Pow)),
+                  aSize - aOldSize, true, false)) {
+      return false;
+    }
+
+    aChunk->map[pageind].bits = aSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+    aChunk->map[pageind + npages].bits = CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
+
+    mStats.allocated_large += aSize - aOldSize;
+    return true;
+  }
+
+  return false;
+}
+
+void* arena_t::RallocSmallOrLarge(void* aPtr, size_t aSize, size_t aOldSize) {
+  void* ret;
+  size_t copysize;
+  SizeClass sizeClass(aSize);
+
+  // Try to avoid moving the allocation.
+  if (aOldSize <= gMaxLargeClass && sizeClass.Size() == aOldSize) {
+    if (aSize < aOldSize) {
+      MaybePoison((void*)(uintptr_t(aPtr) + aSize), aOldSize - aSize);
+    }
+    return aPtr;
+  }
+  if (sizeClass.Type() == SizeClass::Large && aOldSize > gMaxBinClass &&
+      aOldSize <= gMaxLargeClass) {
+    arena_chunk_t* chunk = GetChunkForPtr(aPtr);
+    if (sizeClass.Size() < aOldSize) {
+      // Fill before shrinking in order to avoid a race.
+      MaybePoison((void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
+      RallocShrinkLarge(chunk, aPtr, sizeClass.Size(), aOldSize);
+      return aPtr;
+    }
+    if (RallocGrowLarge(chunk, aPtr, sizeClass.Size(), aOldSize)) {
+      ApplyZeroOrJunk((void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
+      return aPtr;
+    }
+  }
+
+  // If we get here, then aSize and aOldSize are different enough that we
+  // need to move the object.  In that case, fall back to allocating new
+  // space and copying. Allow non-private arenas to switch arenas.
+  ret = (mIsPrivate ? this : choose_arena(aSize))->Malloc(aSize, false);
+  if (!ret) {
+    return nullptr;
+  }
+
+  // Junk/zero-filling were already done by arena_t::Malloc().
+  copysize = (aSize < aOldSize) ? aSize : aOldSize;
+#ifdef VM_COPY_MIN
+  if (copysize >= VM_COPY_MIN) {
+    pages_copy(ret, aPtr, copysize);
+  } else
+#endif
+  {
+    memcpy(ret, aPtr, copysize);
+  }
+  idalloc(aPtr, this);
+  return ret;
+}
+
+void* arena_t::Ralloc(void* aPtr, size_t aSize, size_t aOldSize) {
+  MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
+  MOZ_ASSERT(aPtr);
+  MOZ_ASSERT(aSize != 0);
+
+  return (aSize <= gMaxLargeClass) ? RallocSmallOrLarge(aPtr, aSize, aOldSize)
+                                   : RallocHuge(aPtr, aSize, aOldSize);
+}
+
+void* arena_t::operator new(size_t aCount, const fallible_t&) noexcept {
+  MOZ_ASSERT(aCount == sizeof(arena_t));
+  return TypedBaseAlloc<arena_t>::alloc();
+}
+
+void arena_t::operator delete(void* aPtr) {
+  TypedBaseAlloc<arena_t>::dealloc((arena_t*)aPtr);
+}
+
+arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
+  unsigned i;
+
+  memset(&mLink, 0, sizeof(mLink));
+  memset(&mStats, 0, sizeof(arena_stats_t));
+  mId = 0;
+
+  // Initialize chunks.
+  mChunksDirty.Init();
+#ifdef MALLOC_DOUBLE_PURGE
+  new (&mChunksMAdvised) DoublyLinkedList<arena_chunk_t>();
+#endif
+  mSpare = nullptr;
+
+  mRandomizeSmallAllocations = opt_randomize_small;
+  MaybeMutex::DoLock doLock = MaybeMutex::MUST_LOCK;
+  if (aParams) {
+    uint32_t randFlags = aParams->mFlags & ARENA_FLAG_RANDOMIZE_SMALL_MASK;
+    switch (randFlags) {
+      case ARENA_FLAG_RANDOMIZE_SMALL_ENABLED:
+        mRandomizeSmallAllocations = true;
+        break;
+      case ARENA_FLAG_RANDOMIZE_SMALL_DISABLED:
+        mRandomizeSmallAllocations = false;
+        break;
+      case ARENA_FLAG_RANDOMIZE_SMALL_DEFAULT:
+      default:
+        break;
+    }
+
+    uint32_t threadFlags = aParams->mFlags & ARENA_FLAG_THREAD_MASK;
+    if (threadFlags == ARENA_FLAG_THREAD_MAIN_THREAD_ONLY) {
+      // At the moment we require that any ARENA_FLAG_THREAD_MAIN_THREAD_ONLY
+      // arenas are created and therefore always accessed by the main thread.
+      // This is for two reasons:
+      //  * it allows jemalloc_stats to read their statistics (we also require
+      //    that jemalloc_stats is only used on the main thread).
+      //  * Only main-thread or threadsafe arenas can be guanteed to be in a
+      //    consistent state after a fork() from the main thread.  If fork()
+      //    occurs off-thread then the new child process cannot use these arenas
+      //    (new children should usually exec() or exit() since other data may
+      //    also be inconsistent).
+      MOZ_ASSERT(gArenas.IsOnMainThread());
+      MOZ_ASSERT(aIsPrivate);
+      doLock = MaybeMutex::AVOID_LOCK_UNSAFE;
+    }
+
+    mMaxDirtyIncreaseOverride = aParams->mMaxDirtyIncreaseOverride;
+    mMaxDirtyDecreaseOverride = aParams->mMaxDirtyDecreaseOverride;
+  } else {
+    mMaxDirtyIncreaseOverride = 0;
+    mMaxDirtyDecreaseOverride = 0;
+  }
+
+  MOZ_RELEASE_ASSERT(mLock.Init(doLock));
+
+  mPRNG = nullptr;
+
+  mIsPrivate = aIsPrivate;
+
+  mNumDirty = 0;
+  // The default maximum amount of dirty pages allowed on arenas is a fraction
+  // of opt_dirty_max.
+  mMaxDirty = (aParams && aParams->mMaxDirty) ? aParams->mMaxDirty
+                                              : (opt_dirty_max / 8);
+
+  mRunsAvail.Init();
+
+  // Initialize bins.
+  SizeClass sizeClass(1);
+
+  for (i = 0;; i++) {
+    arena_bin_t& bin = mBins[i];
+    bin.Init(sizeClass);
+
+    // SizeClass doesn't want sizes larger than gMaxBinClass for now.
+    if (sizeClass.Size() == gMaxBinClass) {
+      break;
+    }
+    sizeClass = sizeClass.Next();
+  }
+  MOZ_ASSERT(i == NUM_SMALL_CLASSES - 1);
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+  mMagic = ARENA_MAGIC;
+#endif
+}
+
+arena_t::~arena_t() {
+  size_t i;
+  MaybeMutexAutoLock lock(mLock);
+  MOZ_RELEASE_ASSERT(!mLink.Left() && !mLink.Right(),
+                     "Arena is still registered");
+  MOZ_RELEASE_ASSERT(!mStats.allocated_small && !mStats.allocated_large,
+                     "Arena is not empty");
+  if (mSpare) {
+    chunk_dealloc(mSpare, kChunkSize, ARENA_CHUNK);
+  }
+  for (i = 0; i < NUM_SMALL_CLASSES; i++) {
+    MOZ_RELEASE_ASSERT(!mBins[i].mNonFullRuns.First(), "Bin is not empty");
+  }
+#ifdef MOZ_DEBUG
+  {
+    MutexAutoLock lock(huge_mtx);
+    // This is an expensive check, so we only do it on debug builds.
+    for (auto node : huge.iter()) {
+      MOZ_RELEASE_ASSERT(node->mArenaId != mId, "Arena has huge allocations");
+    }
+  }
+#endif
+  mId = 0;
+}
+
+arena_t* ArenaCollection::CreateArena(bool aIsPrivate,
+                                      arena_params_t* aParams) {
+  arena_t* ret = new (fallible) arena_t(aParams, aIsPrivate);
+  if (!ret) {
+    // Only reached if there is an OOM error.
+
+    // OOM here is quite inconvenient to propagate, since dealing with it
+    // would require a check for failure in the fast path.  Instead, punt
+    // by using the first arena.
+    // In practice, this is an extremely unlikely failure.
+    _malloc_message(_getprogname(), ": (malloc) Error initializing arena\n");
+
+    return mDefaultArena;
+  }
+
+  MutexAutoLock lock(mLock);
+
+  // For public arenas, it's fine to just use incrementing arena id
+  if (!aIsPrivate) {
+    ret->mId = mLastPublicArenaId++;
+    mArenas.Insert(ret);
+    return ret;
+  }
+
+  // For private arenas, generate a cryptographically-secure random id for the
+  // new arena. If an attacker manages to get control of the process, this
+  // should make it more difficult for them to "guess" the ID of a memory
+  // arena, stopping them from getting data they may want
+  Tree& tree = (ret->IsMainThreadOnly()) ? mMainThreadArenas : mPrivateArenas;
+  arena_id_t arena_id;
+  do {
+    arena_id = MakeRandArenaId(ret->IsMainThreadOnly());
+    // Keep looping until we ensure that the random number we just generated
+    // isn't already in use by another active arena
+  } while (GetByIdInternal(tree, arena_id));
+
+  ret->mId = arena_id;
+  tree.Insert(ret);
+  return ret;
+}
+
+arena_id_t ArenaCollection::MakeRandArenaId(bool aIsMainThreadOnly) const {
+  uint64_t rand;
+  do {
+    mozilla::Maybe<uint64_t> maybeRandomId = mozilla::RandomUint64();
+    MOZ_RELEASE_ASSERT(maybeRandomId.isSome());
+
+    rand = maybeRandomId.value();
+
+    // Set or clear the least significant bit depending on if this is a
+    // main-thread-only arena.  We use this in GetById.
+    if (aIsMainThreadOnly) {
+      rand = rand | MAIN_THREAD_ARENA_BIT;
+    } else {
+      rand = rand & ~MAIN_THREAD_ARENA_BIT;
+    }
+
+    // Avoid 0 as an arena Id. We use 0 for disposed arenas.
+  } while (rand == 0);
+
+  return arena_id_t(rand);
+}
+
+// End arena.
+// ***************************************************************************
+// Begin general internal functions.
+
+void* arena_t::MallocHuge(size_t aSize, bool aZero) {
+  return PallocHuge(aSize, kChunkSize, aZero);
+}
+
+void* arena_t::PallocHuge(size_t aSize, size_t aAlignment, bool aZero) {
+  void* ret;
+  size_t csize;
+  size_t psize;
+  extent_node_t* node;
+
+  // We're going to configure guard pages in the region between the
+  // page-aligned size and the chunk-aligned size, so if those are the same
+  // then we need to force that region into existence.
+  csize = CHUNK_CEILING(aSize + gPageSize);
+  if (csize < aSize) {
+    // size is large enough to cause size_t wrap-around.
+    return nullptr;
+  }
+
+  // Allocate an extent node with which to track the chunk.
+  node = ExtentAlloc::alloc();
+  if (!node) {
+    return nullptr;
+  }
+
+  // Allocate one or more contiguous chunks for this request.
+  ret = chunk_alloc(csize, aAlignment, false);
+  if (!ret) {
+    ExtentAlloc::dealloc(node);
+    return nullptr;
+  }
+  psize = PAGE_CEILING(aSize);
+#ifdef MOZ_DEBUG
+  if (aZero) {
+    chunk_assert_zero(ret, psize);
+  }
+#endif
+
+  // Insert node into huge.
+  node->mAddr = ret;
+  node->mSize = psize;
+  node->mArena = this;
+  node->mArenaId = mId;
+
+  {
+    MutexAutoLock lock(huge_mtx);
+    huge.Insert(node);
+
+    // Although we allocated space for csize bytes, we indicate that we've
+    // allocated only psize bytes.
+    //
+    // If DECOMMIT is defined, this is a reasonable thing to do, since
+    // we'll explicitly decommit the bytes in excess of psize.
+    //
+    // If DECOMMIT is not defined, then we're relying on the OS to be lazy
+    // about how it allocates physical pages to mappings.  If we never
+    // touch the pages in excess of psize, the OS won't allocate a physical
+    // page, and we won't use more than psize bytes of physical memory.
+    //
+    // A correct program will only touch memory in excess of how much it
+    // requested if it first calls malloc_usable_size and finds out how
+    // much space it has to play with.  But because we set node->mSize =
+    // psize above, malloc_usable_size will return psize, not csize, and
+    // the program will (hopefully) never touch bytes in excess of psize.
+    // Thus those bytes won't take up space in physical memory, and we can
+    // reasonably claim we never "allocated" them in the first place.
+    huge_allocated += psize;
+    huge_mapped += csize;
+  }
+
+  pages_decommit((void*)((uintptr_t)ret + psize), csize - psize);
+
+  if (!aZero) {
+    ApplyZeroOrJunk(ret, psize);
+  }
+
+  return ret;
+}
+
+void* arena_t::RallocHuge(void* aPtr, size_t aSize, size_t aOldSize) {
+  void* ret;
+  size_t copysize;
+
+  // Avoid moving the allocation if the size class would not change.
+  if (aOldSize > gMaxLargeClass &&
+      CHUNK_CEILING(aSize + gPageSize) == CHUNK_CEILING(aOldSize + gPageSize)) {
+    size_t psize = PAGE_CEILING(aSize);
+    if (aSize < aOldSize) {
+      MaybePoison((void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
+    }
+    if (psize < aOldSize) {
+      extent_node_t key;
+
+      pages_decommit((void*)((uintptr_t)aPtr + psize), aOldSize - psize);
+
+      // Update recorded size.
+      MutexAutoLock lock(huge_mtx);
+      key.mAddr = const_cast<void*>(aPtr);
+      extent_node_t* node = huge.Search(&key);
+      MOZ_ASSERT(node);
+      MOZ_ASSERT(node->mSize == aOldSize);
+      MOZ_RELEASE_ASSERT(node->mArena == this);
+      huge_allocated -= aOldSize - psize;
+      // No need to change huge_mapped, because we didn't (un)map anything.
+      node->mSize = psize;
+    } else if (psize > aOldSize) {
+      if (!pages_commit((void*)((uintptr_t)aPtr + aOldSize),
+                        psize - aOldSize)) {
+        return nullptr;
+      }
+
+      // We need to update the recorded size if the size increased,
+      // so malloc_usable_size doesn't return a value smaller than
+      // what was requested via realloc().
+      extent_node_t key;
+      MutexAutoLock lock(huge_mtx);
+      key.mAddr = const_cast<void*>(aPtr);
+      extent_node_t* node = huge.Search(&key);
+      MOZ_ASSERT(node);
+      MOZ_ASSERT(node->mSize == aOldSize);
+      MOZ_RELEASE_ASSERT(node->mArena == this);
+      huge_allocated += psize - aOldSize;
+      // No need to change huge_mapped, because we didn't
+      // (un)map anything.
+      node->mSize = psize;
+    }
+
+    if (aSize > aOldSize) {
+      ApplyZeroOrJunk((void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
+    }
+    return aPtr;
+  }
+
+  // If we get here, then aSize and aOldSize are different enough that we
+  // need to use a different size class.  In that case, fall back to allocating
+  // new space and copying. Allow non-private arenas to switch arenas.
+  ret = (mIsPrivate ? this : choose_arena(aSize))->MallocHuge(aSize, false);
+  if (!ret) {
+    return nullptr;
+  }
+
+  copysize = (aSize < aOldSize) ? aSize : aOldSize;
+#ifdef VM_COPY_MIN
+  if (copysize >= VM_COPY_MIN) {
+    pages_copy(ret, aPtr, copysize);
+  } else
+#endif
+  {
+    memcpy(ret, aPtr, copysize);
+  }
+  idalloc(aPtr, this);
+  return ret;
+}
+
+static void huge_dalloc(void* aPtr, arena_t* aArena) {
+  extent_node_t* node;
+  size_t mapped = 0;
+  {
+    extent_node_t key;
+    MutexAutoLock lock(huge_mtx);
+
+    // Extract from tree of huge allocations.
+    key.mAddr = aPtr;
+    node = huge.Search(&key);
+    MOZ_RELEASE_ASSERT(node, "Double-free?");
+    MOZ_ASSERT(node->mAddr == aPtr);
+    MOZ_RELEASE_ASSERT(!aArena || node->mArena == aArena);
+    // See AllocInfo::Arena.
+    MOZ_RELEASE_ASSERT(node->mArenaId == node->mArena->mId);
+    huge.Remove(node);
+
+    mapped = CHUNK_CEILING(node->mSize + gPageSize);
+    huge_allocated -= node->mSize;
+    huge_mapped -= mapped;
+  }
+
+  // Unmap chunk.
+  chunk_dealloc(node->mAddr, mapped, HUGE_CHUNK);
+
+  ExtentAlloc::dealloc(node);
+}
+
+size_t GetKernelPageSize() {
+  static size_t kernel_page_size = ([]() {
+#ifdef XP_WIN
+    SYSTEM_INFO info;
+    GetSystemInfo(&info);
+    return info.dwPageSize;
+#else
+    long result = sysconf(_SC_PAGESIZE);
+    MOZ_ASSERT(result != -1);
+    return result;
+#endif
+  })();
+  return kernel_page_size;
+}
+
+// Returns whether the allocator was successfully initialized.
+static bool malloc_init_hard() {
+  unsigned i;
+  const char* opts;
+
+  AutoLock<StaticMutex> lock(gInitLock);
+
+  if (malloc_initialized) {
+    // Another thread initialized the allocator before this one
+    // acquired gInitLock.
+    return true;
+  }
+
+  if (!thread_arena.init()) {
+    return true;
+  }
+
+  // Get page size and number of CPUs
+  const size_t page_size = GetKernelPageSize();
+  // We assume that the page size is a power of 2.
+  MOZ_ASSERT(IsPowerOfTwo(page_size));
+#ifdef MALLOC_STATIC_PAGESIZE
+  if (gPageSize % page_size) {
+    _malloc_message(
+        _getprogname(),
+        "Compile-time page size does not divide the runtime one.\n");
+    MOZ_CRASH();
+  }
+#else
+  gRealPageSize = gPageSize = page_size;
+#endif
+
+  // Get runtime configuration.
+  if ((opts = getenv("MALLOC_OPTIONS"))) {
+    for (i = 0; opts[i] != '\0'; i++) {
+      // All options are single letters, some take a *prefix* numeric argument.
+
+      // Parse the argument.
+      unsigned prefix_arg = 0;
+      while (opts[i] >= '0' && opts[i] <= '9') {
+        prefix_arg *= 10;
+        prefix_arg += opts[i] - '0';
+        i++;
+      }
+
+      switch (opts[i]) {
+        case 'f':
+          opt_dirty_max >>= prefix_arg ? prefix_arg : 1;
+          break;
+        case 'F':
+          prefix_arg = prefix_arg ? prefix_arg : 1;
+          if (opt_dirty_max == 0) {
+            opt_dirty_max = 1;
+            prefix_arg--;
+          }
+          opt_dirty_max <<= prefix_arg;
+          if (opt_dirty_max == 0) {
+            // If the shift above overflowed all the bits then clamp the result
+            // instead.  If we started with DIRTY_MAX_DEFAULT then this will
+            // always be a power of two so choose the maximum power of two that
+            // fits in a size_t.
+            opt_dirty_max = size_t(1) << (sizeof(size_t) * CHAR_BIT - 1);
+          }
+          break;
+#ifdef MALLOC_RUNTIME_CONFIG
+        case 'j':
+          opt_junk = false;
+          break;
+        case 'J':
+          opt_junk = true;
+          break;
+        case 'q':
+          // The argument selects how much poisoning to do.
+          opt_poison = NONE;
+          break;
+        case 'Q':
+          if (opts[i + 1] == 'Q') {
+            // Maximum poisoning.
+            i++;
+            opt_poison = ALL;
+          } else {
+            opt_poison = SOME;
+            opt_poison_size = kCacheLineSize * prefix_arg;
+          }
+          break;
+        case 'z':
+          opt_zero = false;
+          break;
+        case 'Z':
+          opt_zero = true;
+          break;
+#  ifndef MALLOC_STATIC_PAGESIZE
+        case 'P':
+          MOZ_ASSERT(gPageSize >= 4_KiB);
+          MOZ_ASSERT(gPageSize <= 64_KiB);
+          prefix_arg = prefix_arg ? prefix_arg : 1;
+          gPageSize <<= prefix_arg;
+          // We know that if the shift causes gPageSize to be zero then it's
+          // because it shifted all the bits off.  We didn't start with zero.
+          // Therefore if gPageSize is out of bounds we set it to 64KiB.
+          if (gPageSize < 4_KiB || gPageSize > 64_KiB) {
+            gPageSize = 64_KiB;
+          }
+          break;
+#  endif
+#endif
+        case 'r':
+          opt_randomize_small = false;
+          break;
+        case 'R':
+          opt_randomize_small = true;
+          break;
+        default: {
+          char cbuf[2];
+
+          cbuf[0] = opts[i];
+          cbuf[1] = '\0';
+          _malloc_message(_getprogname(),
+                          ": (malloc) Unsupported character "
+                          "in malloc options: '",
+                          cbuf, "'\n");
+        }
+      }
+    }
+  }
+
+#ifndef MALLOC_STATIC_PAGESIZE
+  DefineGlobals();
+#endif
+  gRecycledSize = 0;
+
+  // Initialize chunks data.
+  chunks_mtx.Init();
+  MOZ_PUSH_IGNORE_THREAD_SAFETY
+  gChunksBySize.Init();
+  gChunksByAddress.Init();
+  MOZ_POP_THREAD_SAFETY
+
+  // Initialize huge allocation data.
+  huge_mtx.Init();
+  MOZ_PUSH_IGNORE_THREAD_SAFETY
+  huge.Init();
+  huge_allocated = 0;
+  huge_mapped = 0;
+  MOZ_POP_THREAD_SAFETY
+
+  // Initialize base allocation data structures.
+  base_mtx.Init();
+  MOZ_PUSH_IGNORE_THREAD_SAFETY
+  base_mapped = 0;
+  base_committed = 0;
+  MOZ_POP_THREAD_SAFETY
+
+  // Initialize arenas collection here.
+  if (!gArenas.Init()) {
+    return false;
+  }
+
+  // Assign the default arena to the initial thread.
+  thread_arena.set(gArenas.GetDefault());
+
+  if (!gChunkRTree.Init()) {
+    return false;
+  }
+
+  malloc_initialized = true;
+
+  // Dummy call so that the function is not removed by dead-code elimination
+  Debug::jemalloc_ptr_info(nullptr);
+
+#if !defined(XP_WIN) && !defined(XP_DARWIN)
+  // Prevent potential deadlock on malloc locks after fork.
+  pthread_atfork(_malloc_prefork, _malloc_postfork_parent,
+                 _malloc_postfork_child);
+#endif
+
+  return true;
+}
+
+// End general internal functions.
+// ***************************************************************************
+// Begin malloc(3)-compatible functions.
+
+// The BaseAllocator class is a helper class that implements the base allocator
+// functions (malloc, calloc, realloc, free, memalign) for a given arena,
+// or an appropriately chosen arena (per choose_arena()) when none is given.
+struct BaseAllocator {
+#define MALLOC_DECL(name, return_type, ...) \
+  inline return_type name(__VA_ARGS__);
+
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#include "malloc_decls.h"
+
+  explicit BaseAllocator(arena_t* aArena) : mArena(aArena) {}
+
+ private:
+  arena_t* mArena;
+};
+
+#define MALLOC_DECL(name, return_type, ...)                  \
+  inline return_type MozJemalloc::name(                      \
+      ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) {              \
+    BaseAllocator allocator(nullptr);                        \
+    return allocator.name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
+  }
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#include "malloc_decls.h"
+
+inline void* BaseAllocator::malloc(size_t aSize) {
+  void* ret;
+  arena_t* arena;
+
+  if (!malloc_init()) {
+    ret = nullptr;
+    goto RETURN;
+  }
+
+  if (aSize == 0) {
+    aSize = 1;
+  }
+  // If mArena is non-null, it must not be in the first page.
+  MOZ_DIAGNOSTIC_ASSERT_IF(mArena, (size_t)mArena >= gPageSize);
+  arena = mArena ? mArena : choose_arena(aSize);
+  ret = arena->Malloc(aSize, /* aZero = */ false);
+
+RETURN:
+  if (!ret) {
+    errno = ENOMEM;
+  }
+
+  return ret;
+}
+
+inline void* BaseAllocator::memalign(size_t aAlignment, size_t aSize) {
+  MOZ_ASSERT(((aAlignment - 1) & aAlignment) == 0);
+
+  if (!malloc_init()) {
+    return nullptr;
+  }
+
+  if (aSize == 0) {
+    aSize = 1;
+  }
+
+  aAlignment = aAlignment < sizeof(void*) ? sizeof(void*) : aAlignment;
+  arena_t* arena = mArena ? mArena : choose_arena(aSize);
+  return arena->Palloc(aAlignment, aSize);
+}
+
+inline void* BaseAllocator::calloc(size_t aNum, size_t aSize) {
+  void* ret;
+
+  if (malloc_init()) {
+    CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aNum) * aSize;
+    if (checkedSize.isValid()) {
+      size_t allocSize = checkedSize.value();
+      if (allocSize == 0) {
+        allocSize = 1;
+      }
+      arena_t* arena = mArena ? mArena : choose_arena(allocSize);
+      ret = arena->Malloc(allocSize, /* aZero = */ true);
+    } else {
+      ret = nullptr;
+    }
+  } else {
+    ret = nullptr;
+  }
+
+  if (!ret) {
+    errno = ENOMEM;
+  }
+
+  return ret;
+}
+
+inline void* BaseAllocator::realloc(void* aPtr, size_t aSize) {
+  void* ret;
+
+  if (aSize == 0) {
+    aSize = 1;
+  }
+
+  if (aPtr) {
+    MOZ_RELEASE_ASSERT(malloc_initialized);
+
+    auto info = AllocInfo::Get(aPtr);
+    auto arena = info.Arena();
+    MOZ_RELEASE_ASSERT(!mArena || arena == mArena);
+    ret = arena->Ralloc(aPtr, aSize, info.Size());
+  } else {
+    if (!malloc_init()) {
+      ret = nullptr;
+    } else {
+      arena_t* arena = mArena ? mArena : choose_arena(aSize);
+      ret = arena->Malloc(aSize, /* aZero = */ false);
+    }
+  }
+
+  if (!ret) {
+    errno = ENOMEM;
+  }
+  return ret;
+}
+
+inline void BaseAllocator::free(void* aPtr) {
+  size_t offset;
+
+  // A version of idalloc that checks for nullptr pointer.
+  offset = GetChunkOffsetForPtr(aPtr);
+  if (offset != 0) {
+    MOZ_RELEASE_ASSERT(malloc_initialized);
+    arena_dalloc(aPtr, offset, mArena);
+  } else if (aPtr) {
+    MOZ_RELEASE_ASSERT(malloc_initialized);
+    huge_dalloc(aPtr, mArena);
+  }
+}
+
+inline int MozJemalloc::posix_memalign(void** aMemPtr, size_t aAlignment,
+                                       size_t aSize) {
+  return AlignedAllocator<memalign>::posix_memalign(aMemPtr, aAlignment, aSize);
+}
+
+inline void* MozJemalloc::aligned_alloc(size_t aAlignment, size_t aSize) {
+  return AlignedAllocator<memalign>::aligned_alloc(aAlignment, aSize);
+}
+
+inline void* MozJemalloc::valloc(size_t aSize) {
+  return AlignedAllocator<memalign>::valloc(aSize);
+}
+
+// End malloc(3)-compatible functions.
+// ***************************************************************************
+// Begin non-standard functions.
+
+// This was added by Mozilla for use by SQLite.
+inline size_t MozJemalloc::malloc_good_size(size_t aSize) {
+  if (aSize <= gMaxLargeClass) {
+    // Small or large
+    aSize = SizeClass(aSize).Size();
+  } else {
+    // Huge.  We use PAGE_CEILING to get psize, instead of using
+    // CHUNK_CEILING to get csize.  This ensures that this
+    // malloc_usable_size(malloc(n)) always matches
+    // malloc_good_size(n).
+    aSize = PAGE_CEILING(aSize);
+  }
+  return aSize;
+}
+
+inline size_t MozJemalloc::malloc_usable_size(usable_ptr_t aPtr) {
+  return AllocInfo::GetValidated(aPtr).Size();
+}
+
+inline void MozJemalloc::jemalloc_stats_internal(
+    jemalloc_stats_t* aStats, jemalloc_bin_stats_t* aBinStats) {
+  size_t non_arena_mapped, chunk_header_size;
+
+  if (!aStats) {
+    return;
+  }
+  if (!malloc_init()) {
+    memset(aStats, 0, sizeof(*aStats));
+    return;
+  }
+  if (aBinStats) {
+    memset(aBinStats, 0, sizeof(jemalloc_bin_stats_t) * NUM_SMALL_CLASSES);
+  }
+
+  // Gather runtime settings.
+  aStats->opt_junk = opt_junk;
+  aStats->opt_zero = opt_zero;
+  aStats->quantum = kQuantum;
+  aStats->quantum_max = kMaxQuantumClass;
+  aStats->quantum_wide = kQuantumWide;
+  aStats->quantum_wide_max = kMaxQuantumWideClass;
+  aStats->subpage_max = gMaxSubPageClass;
+  aStats->large_max = gMaxLargeClass;
+  aStats->chunksize = kChunkSize;
+  aStats->page_size = gPageSize;
+  aStats->dirty_max = opt_dirty_max;
+
+  // Gather current memory usage statistics.
+  aStats->narenas = 0;
+  aStats->mapped = 0;
+  aStats->allocated = 0;
+  aStats->waste = 0;
+  aStats->page_cache = 0;
+  aStats->bookkeeping = 0;
+  aStats->bin_unused = 0;
+
+  non_arena_mapped = 0;
+
+  // Get huge mapped/allocated.
+  {
+    MutexAutoLock lock(huge_mtx);
+    non_arena_mapped += huge_mapped;
+    aStats->allocated += huge_allocated;
+    MOZ_ASSERT(huge_mapped >= huge_allocated);
+  }
+
+  // Get base mapped/allocated.
+  {
+    MutexAutoLock lock(base_mtx);
+    non_arena_mapped += base_mapped;
+    aStats->bookkeeping += base_committed;
+    MOZ_ASSERT(base_mapped >= base_committed);
+  }
+
+  gArenas.mLock.Lock();
+
+  // Stats can only read complete information if its run on the main thread.
+  MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
+
+  // Iterate over arenas.
+  for (auto arena : gArenas.iter()) {
+    // Cannot safely read stats for this arena and therefore stats would be
+    // incomplete.
+    MOZ_ASSERT(arena->mLock.SafeOnThisThread());
+
+    size_t arena_mapped, arena_allocated, arena_committed, arena_dirty, j,
+        arena_unused, arena_headers;
+
+    arena_headers = 0;
+    arena_unused = 0;
+
+    {
+      MaybeMutexAutoLock lock(arena->mLock);
+
+      arena_mapped = arena->mStats.mapped;
+
+      // "committed" counts dirty and allocated memory.
+      arena_committed = arena->mStats.committed << gPageSize2Pow;
+
+      arena_allocated =
+          arena->mStats.allocated_small + arena->mStats.allocated_large;
+
+      arena_dirty = arena->mNumDirty << gPageSize2Pow;
+
+      for (j = 0; j < NUM_SMALL_CLASSES; j++) {
+        arena_bin_t* bin = &arena->mBins[j];
+        size_t bin_unused = 0;
+        size_t num_non_full_runs = 0;
+
+        for (auto mapelm : bin->mNonFullRuns.iter()) {
+          arena_run_t* run = (arena_run_t*)(mapelm->bits & ~gPageSizeMask);
+          bin_unused += run->mNumFree * bin->mSizeClass;
+          num_non_full_runs++;
+        }
+
+        if (bin->mCurrentRun) {
+          bin_unused += bin->mCurrentRun->mNumFree * bin->mSizeClass;
+          num_non_full_runs++;
+        }
+
+        arena_unused += bin_unused;
+        arena_headers += bin->mNumRuns * bin->mRunFirstRegionOffset;
+        if (aBinStats) {
+          aBinStats[j].size = bin->mSizeClass;
+          aBinStats[j].num_non_full_runs += num_non_full_runs;
+          aBinStats[j].num_runs += bin->mNumRuns;
+          aBinStats[j].bytes_unused += bin_unused;
+          size_t bytes_per_run = static_cast<size_t>(bin->mRunSizePages)
+                                 << gPageSize2Pow;
+          aBinStats[j].bytes_total +=
+              bin->mNumRuns * (bytes_per_run - bin->mRunFirstRegionOffset);
+          aBinStats[j].bytes_per_run = bytes_per_run;
+        }
+      }
+    }
+
+    MOZ_ASSERT(arena_mapped >= arena_committed);
+    MOZ_ASSERT(arena_committed >= arena_allocated + arena_dirty);
+
+    aStats->mapped += arena_mapped;
+    aStats->allocated += arena_allocated;
+    aStats->page_cache += arena_dirty;
+    // "waste" is committed memory that is neither dirty nor
+    // allocated.  If you change this definition please update
+    // memory/replace/logalloc/replay/Replay.cpp's jemalloc_stats calculation of
+    // committed.
+    MOZ_ASSERT(arena_committed >=
+               (arena_allocated + arena_dirty + arena_unused + arena_headers));
+    aStats->waste += arena_committed - arena_allocated - arena_dirty -
+                     arena_unused - arena_headers;
+    aStats->bin_unused += arena_unused;
+    aStats->bookkeeping += arena_headers;
+    aStats->narenas++;
+  }
+  gArenas.mLock.Unlock();
+
+  // Account for arena chunk headers in bookkeeping rather than waste.
+  chunk_header_size =
+      ((aStats->mapped / aStats->chunksize) * (gChunkHeaderNumPages - 1))
+      << gPageSize2Pow;
+
+  aStats->mapped += non_arena_mapped;
+  aStats->bookkeeping += chunk_header_size;
+  aStats->waste -= chunk_header_size;
+
+  MOZ_ASSERT(aStats->mapped >= aStats->allocated + aStats->waste +
+                                   aStats->page_cache + aStats->bookkeeping);
+}
+
+inline size_t MozJemalloc::jemalloc_stats_num_bins() {
+  return NUM_SMALL_CLASSES;
+}
+
+inline void MozJemalloc::jemalloc_set_main_thread() {
+  MOZ_ASSERT(malloc_initialized);
+  gArenas.SetMainThread();
+}
+
+#ifdef MALLOC_DOUBLE_PURGE
+
+// Explicitly remove all of this chunk's MADV_FREE'd pages from memory.
+static void hard_purge_chunk(arena_chunk_t* aChunk) {
+  // See similar logic in arena_t::Purge().
+  for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages; i++) {
+    // Find all adjacent pages with CHUNK_MAP_MADVISED set.
+    size_t npages;
+    for (npages = 0; aChunk->map[i + npages].bits & CHUNK_MAP_MADVISED &&
+                     i + npages < gChunkNumPages;
+         npages++) {
+      // Turn off the chunk's MADV_FREED bit and turn on its
+      // DECOMMITTED bit.
+      MOZ_DIAGNOSTIC_ASSERT(
+          !(aChunk->map[i + npages].bits & CHUNK_MAP_DECOMMITTED));
+      aChunk->map[i + npages].bits ^= CHUNK_MAP_MADVISED_OR_DECOMMITTED;
+    }
+
+    // We could use mincore to find out which pages are actually
+    // present, but it's not clear that's better.
+    if (npages > 0) {
+      pages_decommit(((char*)aChunk) + (i << gPageSize2Pow),
+                     npages << gPageSize2Pow);
+      Unused << pages_commit(((char*)aChunk) + (i << gPageSize2Pow),
+                             npages << gPageSize2Pow);
+    }
+    i += npages;
+  }
+}
+
+// Explicitly remove all of this arena's MADV_FREE'd pages from memory.
+void arena_t::HardPurge() {
+  MaybeMutexAutoLock lock(mLock);
+
+  while (!mChunksMAdvised.isEmpty()) {
+    arena_chunk_t* chunk = mChunksMAdvised.popFront();
+    hard_purge_chunk(chunk);
+  }
+}
+
+inline void MozJemalloc::jemalloc_purge_freed_pages() {
+  if (malloc_initialized) {
+    MutexAutoLock lock(gArenas.mLock);
+    MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
+    for (auto arena : gArenas.iter()) {
+      arena->HardPurge();
+    }
+  }
+}
+
+#else  // !defined MALLOC_DOUBLE_PURGE
+
+inline void MozJemalloc::jemalloc_purge_freed_pages() {
+  // Do nothing.
+}
+
+#endif  // defined MALLOC_DOUBLE_PURGE
+
+inline void MozJemalloc::jemalloc_free_dirty_pages(void) {
+  if (malloc_initialized) {
+    MutexAutoLock lock(gArenas.mLock);
+    MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
+    for (auto arena : gArenas.iter()) {
+      MaybeMutexAutoLock arena_lock(arena->mLock);
+      arena->Purge(1);
+    }
+  }
+}
+
+inline arena_t* ArenaCollection::GetByIdInternal(Tree& aTree,
+                                                 arena_id_t aArenaId) {
+  // Use AlignedStorage2 to avoid running the arena_t constructor, while
+  // we only need it as a placeholder for mId.
+  mozilla::AlignedStorage2<arena_t> key;
+  key.addr()->mId = aArenaId;
+  return aTree.Search(key.addr());
+}
+
+inline arena_t* ArenaCollection::GetById(arena_id_t aArenaId, bool aIsPrivate) {
+  if (!malloc_initialized) {
+    return nullptr;
+  }
+
+  Tree* tree = nullptr;
+  if (aIsPrivate) {
+    if (ArenaIdIsMainThreadOnly(aArenaId)) {
+      // Main thread only arena.  Do the lookup here without taking the lock.
+      arena_t* result = GetByIdInternal(mMainThreadArenas, aArenaId);
+      MOZ_RELEASE_ASSERT(result);
+      return result;
+    }
+    tree = &mPrivateArenas;
+  } else {
+    tree = &mArenas;
+  }
+
+  MutexAutoLock lock(mLock);
+  arena_t* result = GetByIdInternal(*tree, aArenaId);
+  MOZ_RELEASE_ASSERT(result);
+  return result;
+}
+
+inline arena_id_t MozJemalloc::moz_create_arena_with_params(
+    arena_params_t* aParams) {
+  if (malloc_init()) {
+    arena_t* arena = gArenas.CreateArena(/* IsPrivate = */ true, aParams);
+    return arena->mId;
+  }
+  return 0;
+}
+
+inline void MozJemalloc::moz_dispose_arena(arena_id_t aArenaId) {
+  arena_t* arena = gArenas.GetById(aArenaId, /* IsPrivate = */ true);
+  MOZ_RELEASE_ASSERT(arena);
+  gArenas.DisposeArena(arena);
+}
+
+inline void MozJemalloc::moz_set_max_dirty_page_modifier(int32_t aModifier) {
+  gArenas.SetDefaultMaxDirtyPageModifier(aModifier);
+}
+
+#define MALLOC_DECL(name, return_type, ...)                          \
+  inline return_type MozJemalloc::moz_arena_##name(                  \
+      arena_id_t aArenaId, ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
+    BaseAllocator allocator(                                         \
+        gArenas.GetById(aArenaId, /* IsPrivate = */ true));          \
+    return allocator.name(ARGS_HELPER(ARGS, ##__VA_ARGS__));         \
+  }
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#include "malloc_decls.h"
+
+// End non-standard functions.
+// ***************************************************************************
+#ifndef XP_WIN
+// Begin library-private functions, used by threading libraries for protection
+// of malloc during fork().  These functions are only called if the program is
+// running in threaded mode, so there is no need to check whether the program
+// is threaded here.
+//
+// Note that the only way to keep the main-thread-only arenas in a consistent
+// state for the child is if fork is called from the main thread only.  Or the
+// child must not use them, eg it should call exec().  We attempt to prevent the
+// child for accessing these arenas by refusing to re-initialise them.
+static pthread_t gForkingThread;
+
+FORK_HOOK
+void _malloc_prefork(void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
+  // Acquire all mutexes in a safe order.
+  gArenas.mLock.Lock();
+  gForkingThread = pthread_self();
+
+  for (auto arena : gArenas.iter()) {
+    if (arena->mLock.LockIsEnabled()) {
+      arena->mLock.Lock();
+    }
+  }
+
+  base_mtx.Lock();
+
+  huge_mtx.Lock();
+}
+
+FORK_HOOK
+void _malloc_postfork_parent(void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
+  // Release all mutexes, now that fork() has completed.
+  huge_mtx.Unlock();
+
+  base_mtx.Unlock();
+
+  for (auto arena : gArenas.iter()) {
+    if (arena->mLock.LockIsEnabled()) {
+      arena->mLock.Unlock();
+    }
+  }
+
+  gArenas.mLock.Unlock();
+}
+
+FORK_HOOK
+void _malloc_postfork_child(void) {
+  // Reinitialize all mutexes, now that fork() has completed.
+  huge_mtx.Init();
+
+  base_mtx.Init();
+
+  for (auto arena : gArenas.iter()) {
+    arena->mLock.Reinit(gForkingThread);
+  }
+
+  gArenas.PostForkFixMainThread();
+  gArenas.mLock.Init();
+}
+#endif  // XP_WIN
+
+// End library-private functions.
+// ***************************************************************************
+#ifdef MOZ_REPLACE_MALLOC
+// Windows doesn't come with weak imports as they are possible with
+// LD_PRELOAD or DYLD_INSERT_LIBRARIES on Linux/OSX. On this platform,
+// the replacement functions are defined as variable pointers to the
+// function resolved with GetProcAddress() instead of weak definitions
+// of functions. On Android, the same needs to happen as well, because
+// the Android linker doesn't handle weak linking with non LD_PRELOADed
+// libraries, but LD_PRELOADing is not very convenient on Android, with
+// the zygote.
+#  ifdef XP_DARWIN
+#    define MOZ_REPLACE_WEAK __attribute__((weak_import))
+#  elif defined(XP_WIN) || defined(ANDROID)
+#    define MOZ_DYNAMIC_REPLACE_INIT
+#    define replace_init replace_init_decl
+#  elif defined(__GNUC__)
+#    define MOZ_REPLACE_WEAK __attribute__((weak))
+#  endif
+
+#  include "replace_malloc.h"
+
+#  define MALLOC_DECL(name, return_type, ...) CanonicalMalloc::name,
+
+// The default malloc table, i.e. plain allocations. It never changes. It's
+// used by init(), and not used after that.
+static const malloc_table_t gDefaultMallocTable = {
+#  include "malloc_decls.h"
+};
+
+// The malloc table installed by init(). It never changes from that point
+// onward. It will be the same as gDefaultMallocTable if no replace-malloc tool
+// is enabled at startup.
+static malloc_table_t gOriginalMallocTable = {
+#  include "malloc_decls.h"
+};
+
+// The malloc table installed by jemalloc_replace_dynamic(). (Read the
+// comments above that function for more details.)
+static malloc_table_t gDynamicMallocTable = {
+#  include "malloc_decls.h"
+};
+
+// This briefly points to gDefaultMallocTable at startup. After that, it points
+// to either gOriginalMallocTable or gDynamicMallocTable. It's atomic to avoid
+// races when switching between tables.
+static Atomic<malloc_table_t const*, mozilla::MemoryOrdering::Relaxed>
+    gMallocTablePtr;
+
+#  ifdef MOZ_DYNAMIC_REPLACE_INIT
+#    undef replace_init
+typedef decltype(replace_init_decl) replace_init_impl_t;
+static replace_init_impl_t* replace_init = nullptr;
+#  endif
+
+#  ifdef XP_WIN
+typedef HMODULE replace_malloc_handle_t;
+
+static replace_malloc_handle_t replace_malloc_handle() {
+  wchar_t replace_malloc_lib[1024];
+  if (GetEnvironmentVariableW(L"MOZ_REPLACE_MALLOC_LIB", replace_malloc_lib,
+                              ArrayLength(replace_malloc_lib)) > 0) {
+    return LoadLibraryW(replace_malloc_lib);
+  }
+  return nullptr;
+}
+
+#    define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
+      (replace_init_impl_t*)GetProcAddress(handle, "replace_init")
+
+#  elif defined(ANDROID)
+#    include <dlfcn.h>
+
+typedef void* replace_malloc_handle_t;
+
+static replace_malloc_handle_t replace_malloc_handle() {
+  const char* replace_malloc_lib = getenv("MOZ_REPLACE_MALLOC_LIB");
+  if (replace_malloc_lib && *replace_malloc_lib) {
+    return dlopen(replace_malloc_lib, RTLD_LAZY);
+  }
+  return nullptr;
+}
+
+#    define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
+      (replace_init_impl_t*)dlsym(handle, "replace_init")
+
+#  endif
+
+static void replace_malloc_init_funcs(malloc_table_t*);
+
+#  ifdef MOZ_REPLACE_MALLOC_STATIC
+extern "C" void logalloc_init(malloc_table_t*, ReplaceMallocBridge**);
+
+extern "C" void dmd_init(malloc_table_t*, ReplaceMallocBridge**);
+#  endif
+
+void phc_init(malloc_table_t*, ReplaceMallocBridge**);
+
+bool Equals(const malloc_table_t& aTable1, const malloc_table_t& aTable2) {
+  return memcmp(&aTable1, &aTable2, sizeof(malloc_table_t)) == 0;
+}
+
+// Below is the malloc implementation overriding jemalloc and calling the
+// replacement functions if they exist.
+static ReplaceMallocBridge* gReplaceMallocBridge = nullptr;
+static void init() {
+  malloc_table_t tempTable = gDefaultMallocTable;
+
+#  ifdef MOZ_DYNAMIC_REPLACE_INIT
+  replace_malloc_handle_t handle = replace_malloc_handle();
+  if (handle) {
+    replace_init = REPLACE_MALLOC_GET_INIT_FUNC(handle);
+  }
+#  endif
+
+  // Set this *before* calling replace_init, otherwise if replace_init calls
+  // malloc() we'll get an infinite loop.
+  gMallocTablePtr = &gDefaultMallocTable;
+
+  // Pass in the default allocator table so replace functions can copy and use
+  // it for their allocations. The replace_init() function should modify the
+  // table if it wants to be active, otherwise leave it unmodified.
+  if (replace_init) {
+    replace_init(&tempTable, &gReplaceMallocBridge);
+  }
+#  ifdef MOZ_REPLACE_MALLOC_STATIC
+  if (Equals(tempTable, gDefaultMallocTable)) {
+    logalloc_init(&tempTable, &gReplaceMallocBridge);
+  }
+#    ifdef MOZ_DMD
+  if (Equals(tempTable, gDefaultMallocTable)) {
+    dmd_init(&tempTable, &gReplaceMallocBridge);
+  }
+#    endif
+#  endif
+  if (!Equals(tempTable, gDefaultMallocTable)) {
+    replace_malloc_init_funcs(&tempTable);
+  }
+  gOriginalMallocTable = tempTable;
+  gMallocTablePtr = &gOriginalMallocTable;
+}
+
+// WARNING WARNING WARNING: this function should be used with extreme care. It
+// is not as general-purpose as it looks. It is currently used by
+// tools/profiler/core/memory_hooks.cpp for counting allocations and probably
+// should not be used for any other purpose.
+//
+// This function allows the original malloc table to be temporarily replaced by
+// a different malloc table. Or, if the argument is nullptr, it switches back to
+// the original malloc table.
+//
+// Limitations:
+//
+// - It is not threadsafe. If multiple threads pass it the same
+//   `replace_init_func` at the same time, there will be data races writing to
+//   the malloc_table_t within that function.
+//
+// - Only one replacement can be installed. No nesting is allowed.
+//
+// - The new malloc table must be able to free allocations made by the original
+//   malloc table, and upon removal the original malloc table must be able to
+//   free allocations made by the new malloc table. This means the new malloc
+//   table can only do simple things like recording extra information, while
+//   delegating actual allocation/free operations to the original malloc table.
+//
+MOZ_JEMALLOC_API void jemalloc_replace_dynamic(
+    jemalloc_init_func replace_init_func) {
+  if (replace_init_func) {
+    malloc_table_t tempTable = gOriginalMallocTable;
+    (*replace_init_func)(&tempTable, &gReplaceMallocBridge);
+    if (!Equals(tempTable, gOriginalMallocTable)) {
+      replace_malloc_init_funcs(&tempTable);
+
+      // Temporarily switch back to the original malloc table. In the
+      // (supported) non-nested case, this is a no-op. But just in case this is
+      // a (unsupported) nested call, it makes the overwriting of
+      // gDynamicMallocTable less racy, because ongoing calls to malloc() and
+      // friends won't go through gDynamicMallocTable.
+      gMallocTablePtr = &gOriginalMallocTable;
+
+      gDynamicMallocTable = tempTable;
+      gMallocTablePtr = &gDynamicMallocTable;
+      // We assume that dynamic replaces don't occur close enough for a
+      // thread to still have old copies of the table pointer when the 2nd
+      // replace occurs.
+    }
+  } else {
+    // Switch back to the original malloc table.
+    gMallocTablePtr = &gOriginalMallocTable;
+  }
+}
+
+#  define MALLOC_DECL(name, return_type, ...)                           \
+    inline return_type ReplaceMalloc::name(                             \
+        ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) {                       \
+      if (MOZ_UNLIKELY(!gMallocTablePtr)) {                             \
+        init();                                                         \
+      }                                                                 \
+      return (*gMallocTablePtr).name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
+    }
+#  include "malloc_decls.h"
+
+MOZ_JEMALLOC_API struct ReplaceMallocBridge* get_bridge(void) {
+  if (MOZ_UNLIKELY(!gMallocTablePtr)) {
+    init();
+  }
+  return gReplaceMallocBridge;
+}
+
+// posix_memalign, aligned_alloc, memalign and valloc all implement some kind
+// of aligned memory allocation. For convenience, a replace-malloc library can
+// skip defining replace_posix_memalign, replace_aligned_alloc and
+// replace_valloc, and default implementations will be automatically derived
+// from replace_memalign.
+static void replace_malloc_init_funcs(malloc_table_t* table) {
+  if (table->posix_memalign == CanonicalMalloc::posix_memalign &&
+      table->memalign != CanonicalMalloc::memalign) {
+    table->posix_memalign =
+        AlignedAllocator<ReplaceMalloc::memalign>::posix_memalign;
+  }
+  if (table->aligned_alloc == CanonicalMalloc::aligned_alloc &&
+      table->memalign != CanonicalMalloc::memalign) {
+    table->aligned_alloc =
+        AlignedAllocator<ReplaceMalloc::memalign>::aligned_alloc;
+  }
+  if (table->valloc == CanonicalMalloc::valloc &&
+      table->memalign != CanonicalMalloc::memalign) {
+    table->valloc = AlignedAllocator<ReplaceMalloc::memalign>::valloc;
+  }
+  if (table->moz_create_arena_with_params ==
+          CanonicalMalloc::moz_create_arena_with_params &&
+      table->malloc != CanonicalMalloc::malloc) {
+#  define MALLOC_DECL(name, ...) \
+    table->name = DummyArenaAllocator<ReplaceMalloc>::name;
+#  define MALLOC_FUNCS MALLOC_FUNCS_ARENA_BASE
+#  include "malloc_decls.h"
+  }
+  if (table->moz_arena_malloc == CanonicalMalloc::moz_arena_malloc &&
+      table->malloc != CanonicalMalloc::malloc) {
+#  define MALLOC_DECL(name, ...) \
+    table->name = DummyArenaAllocator<ReplaceMalloc>::name;
+#  define MALLOC_FUNCS MALLOC_FUNCS_ARENA_ALLOC
+#  include "malloc_decls.h"
+  }
+}
+
+#endif  // MOZ_REPLACE_MALLOC
+// ***************************************************************************
+// Definition of all the _impl functions
+// GENERIC_MALLOC_DECL2_MINGW is only used for the MinGW build, and aliases
+// the malloc funcs (e.g. malloc) to the je_ versions. It does not generate
+// aliases for the other functions (jemalloc and arena functions).
+//
+// We do need aliases for the other mozglue.def-redirected functions though,
+// these are done at the bottom of mozmemory_wrap.cpp
+#define GENERIC_MALLOC_DECL2_MINGW(name, name_impl, return_type, ...) \
+  return_type name(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__))            \
+      __attribute__((alias(MOZ_STRINGIFY(name_impl))));
+
+#define GENERIC_MALLOC_DECL2(attributes, name, name_impl, return_type, ...)  \
+  return_type name_impl(ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) attributes { \
+    return DefaultMalloc::name(ARGS_HELPER(ARGS, ##__VA_ARGS__));            \
+  }
+
+#ifndef __MINGW32__
+#  define GENERIC_MALLOC_DECL(attributes, name, return_type, ...)    \
+    GENERIC_MALLOC_DECL2(attributes, name, name##_impl, return_type, \
+                         ##__VA_ARGS__)
+#else
+#  define GENERIC_MALLOC_DECL(attributes, name, return_type, ...)    \
+    GENERIC_MALLOC_DECL2(attributes, name, name##_impl, return_type, \
+                         ##__VA_ARGS__)                              \
+    GENERIC_MALLOC_DECL2_MINGW(name, name##_impl, return_type, ##__VA_ARGS__)
+#endif
+
+#define NOTHROW_MALLOC_DECL(...) \
+  MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (noexcept(true), __VA_ARGS__))
+#define MALLOC_DECL(...) \
+  MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC
+#include "malloc_decls.h"
+
+#undef GENERIC_MALLOC_DECL
+#define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
+  GENERIC_MALLOC_DECL2(attributes, name, name, return_type, ##__VA_ARGS__)
+
+#define MALLOC_DECL(...) \
+  MOZ_JEMALLOC_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
+#define MALLOC_FUNCS (MALLOC_FUNCS_JEMALLOC | MALLOC_FUNCS_ARENA)
+#include "malloc_decls.h"
+// ***************************************************************************
+
+#ifdef HAVE_DLOPEN
+#  include <dlfcn.h>
+#endif
+
+#if defined(__GLIBC__) && !defined(__UCLIBC__)
+// glibc provides the RTLD_DEEPBIND flag for dlopen which can make it possible
+// to inconsistently reference libc's malloc(3)-compatible functions
+// (bug 493541).
+//
+// These definitions interpose hooks in glibc.  The functions are actually
+// passed an extra argument for the caller return address, which will be
+// ignored.
+
+extern "C" {
+MOZ_EXPORT void (*__free_hook)(void*) = free_impl;
+MOZ_EXPORT void* (*__malloc_hook)(size_t) = malloc_impl;
+MOZ_EXPORT void* (*__realloc_hook)(void*, size_t) = realloc_impl;
+MOZ_EXPORT void* (*__memalign_hook)(size_t, size_t) = memalign_impl;
+}
+
+#elif defined(RTLD_DEEPBIND)
+// XXX On systems that support RTLD_GROUP or DF_1_GROUP, do their
+// implementations permit similar inconsistencies?  Should STV_SINGLETON
+// visibility be used for interposition where available?
+#  error \
+      "Interposing malloc is unsafe on this system without libc malloc hooks."
+#endif
+
+#ifdef XP_WIN
+MOZ_EXPORT void* _recalloc(void* aPtr, size_t aCount, size_t aSize) {
+  size_t oldsize = aPtr ? AllocInfo::Get(aPtr).Size() : 0;
+  CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aCount) * aSize;
+
+  if (!checkedSize.isValid()) {
+    return nullptr;
+  }
+
+  size_t newsize = checkedSize.value();
+
+  // In order for all trailing bytes to be zeroed, the caller needs to
+  // use calloc(), followed by recalloc().  However, the current calloc()
+  // implementation only zeros the bytes requested, so if recalloc() is
+  // to work 100% correctly, calloc() will need to change to zero
+  // trailing bytes.
+  aPtr = DefaultMalloc::realloc(aPtr, newsize);
+  if (aPtr && oldsize < newsize) {
+    memset((void*)((uintptr_t)aPtr + oldsize), 0, newsize - oldsize);
+  }
+
+  return aPtr;
+}
+
+// This impl of _expand doesn't ever actually expand or shrink blocks: it
+// simply replies that you may continue using a shrunk block.
+MOZ_EXPORT void* _expand(void* aPtr, size_t newsize) {
+  if (AllocInfo::Get(aPtr).Size() >= newsize) {
+    return aPtr;
+  }
+
+  return nullptr;
+}
+
+MOZ_EXPORT size_t _msize(void* aPtr) {
+  return DefaultMalloc::malloc_usable_size(aPtr);
+}
+#endif
+
+#ifdef MOZ_PHC
+// Compile PHC and mozjemalloc together so that PHC can inline mozjemalloc.
+#  include "PHC.cpp"
+#endif
diff --git a/memory/build/mozjemalloc.h b/memory/build/mozjemalloc.h
new file mode 100644
index 0000000000..df3fbc31b3
--- /dev/null
+++ b/memory/build/mozjemalloc.h
@@ -0,0 +1,168 @@
+/* -*- 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/. */
+
+#ifndef mozjemalloc_h
+#define mozjemalloc_h
+
+#include <errno.h>
+
+#include "mozjemalloc_types.h"
+#include "mozilla/MacroArgs.h"
+
+// Macro helpers
+
+#define MACRO_CALL(a, b) a b
+// Can't use macros recursively, so we need another one doing the same as above.
+#define MACRO_CALL2(a, b) a b
+
+#define ARGS_HELPER(name, ...)                                     \
+  MACRO_CALL2(MOZ_PASTE_PREFIX_AND_ARG_COUNT(name, ##__VA_ARGS__), \
+              (__VA_ARGS__))
+#define TYPED_ARGS0()
+#define TYPED_ARGS1(t1) t1 arg1
+#define TYPED_ARGS2(t1, t2) TYPED_ARGS1(t1), t2 arg2
+#define TYPED_ARGS3(t1, t2, t3) TYPED_ARGS2(t1, t2), t3 arg3
+
+#define ARGS0()
+#define ARGS1(t1) arg1
+#define ARGS2(t1, t2) ARGS1(t1), arg2
+#define ARGS3(t1, t2, t3) ARGS2(t1, t2), arg3
+
+#ifdef MOZ_MEMORY
+
+size_t GetKernelPageSize();
+
+// Implement the set of alignment functions in terms of memalign.
+template <void* (*memalign)(size_t, size_t)>
+struct AlignedAllocator {
+  static inline int posix_memalign(void** aMemPtr, size_t aAlignment,
+                                   size_t aSize) {
+    void* result;
+
+    // alignment must be a power of two and a multiple of sizeof(void*)
+    if (((aAlignment - 1) & aAlignment) != 0 || aAlignment < sizeof(void*)) {
+      return EINVAL;
+    }
+
+    // The 0-->1 size promotion is done in the memalign() call below
+    result = memalign(aAlignment, aSize);
+
+    if (!result) {
+      return ENOMEM;
+    }
+
+    *aMemPtr = result;
+    return 0;
+  }
+
+  static inline void* aligned_alloc(size_t aAlignment, size_t aSize) {
+    if (aSize % aAlignment) {
+      return nullptr;
+    }
+    return memalign(aAlignment, aSize);
+  }
+
+  static inline void* valloc(size_t aSize) {
+    return memalign(GetKernelPageSize(), aSize);
+  }
+};
+
+// These classes each implement the same interface.  Writing out the
+// interface for each one rather than using inheritance makes things more
+// explicit.
+//
+// Note: compilers are expected to be able to optimize out `this`.
+
+// The MozJemalloc allocator
+struct MozJemalloc {
+#  define MALLOC_DECL(name, return_type, ...) \
+    static inline return_type name(__VA_ARGS__);
+#  include "malloc_decls.h"
+};
+
+#  ifdef MOZ_PHC
+struct MozJemallocPHC : public MozJemalloc {
+#    define MALLOC_DECL(name, return_type, ...) \
+      static return_type name(__VA_ARGS__);
+#    define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#    include "malloc_decls.h"
+
+  static inline int posix_memalign(void** aMemPtr, size_t aAlignment,
+                                   size_t aSize) {
+    return AlignedAllocator<memalign>::posix_memalign(aMemPtr, aAlignment,
+                                                      aSize);
+  }
+
+  static inline void* aligned_alloc(size_t aAlignment, size_t aSize) {
+    return AlignedAllocator<memalign>::aligned_alloc(aAlignment, aSize);
+  }
+
+  static inline void* valloc(size_t aSize) {
+    return AlignedAllocator<memalign>::valloc(aSize);
+  }
+
+  static size_t malloc_usable_size(usable_ptr_t);
+
+  static void jemalloc_stats_internal(jemalloc_stats_t*, jemalloc_bin_stats_t*);
+
+  static void jemalloc_ptr_info(const void*, jemalloc_ptr_info_t*);
+
+#    define MALLOC_DECL(name, return_type, ...) \
+      static return_type name(__VA_ARGS__);
+#    define MALLOC_FUNCS MALLOC_FUNCS_ARENA_ALLOC
+#    include "malloc_decls.h"
+};
+#  endif
+
+#  ifdef MOZ_REPLACE_MALLOC
+// The replace-malloc allocator
+struct ReplaceMalloc {
+#    define MALLOC_DECL(name, return_type, ...) \
+      static return_type name(__VA_ARGS__);
+#    include "malloc_decls.h"
+};
+#  endif
+
+#  ifdef MOZ_PHC
+using CanonicalMalloc = MozJemallocPHC;
+#  else
+using CanonicalMalloc = MozJemalloc;
+#  endif
+
+#  ifdef MOZ_REPLACE_MALLOC
+using DefaultMalloc = ReplaceMalloc;
+#  else
+using DefaultMalloc = CanonicalMalloc;
+#  endif
+
+// Poison - write "poison" to cells upon deallocation.
+constexpr uint8_t kAllocPoison = 0xe5;
+
+// Junk - write this junk value to freshly allocated cells.
+constexpr uint8_t kAllocJunk = 0xe4;
+
+#endif  // MOZ_MEMORY
+
+// Dummy implementation of the moz_arena_* API, falling back to a given
+// implementation of the base allocator.
+template <typename T>
+struct DummyArenaAllocator {
+  static arena_id_t moz_create_arena_with_params(arena_params_t*) { return 0; }
+
+  static void moz_dispose_arena(arena_id_t) {}
+
+  static void moz_set_max_dirty_page_modifier(int32_t) {}
+
+#define MALLOC_DECL(name, return_type, ...)                 \
+  static return_type moz_arena_##name(                      \
+      arena_id_t, ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) { \
+    return T::name(ARGS_HELPER(ARGS, ##__VA_ARGS__));       \
+  }
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
+#include "malloc_decls.h"
+};
+
+#endif
diff --git a/memory/build/mozjemalloc_types.h b/memory/build/mozjemalloc_types.h
new file mode 100644
index 0000000000..1aff0789d2
--- /dev/null
+++ b/memory/build/mozjemalloc_types.h
@@ -0,0 +1,200 @@
+/* -*- 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/. */
+
+// Portions of this file were originally under the following license:
+//
+// Copyright (C) 2006-2008 Jason Evans <jasone@FreeBSD.org>.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1. Redistributions of source code must retain the above copyright
+//    notice(s), this list of conditions and the following disclaimer as
+//    the first lines of this file unmodified other than the possible
+//    addition of one or more copyright notices.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice(s), this list of conditions and the following disclaimer in
+//    the documentation and/or other materials provided with the
+//    distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+// PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef _JEMALLOC_TYPES_H_
+#define _JEMALLOC_TYPES_H_
+
+#include <stdint.h>
+
+// grab size_t
+#ifdef _MSC_VER
+#  include <crtdefs.h>
+#else
+#  include <stddef.h>
+#endif
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef MALLOC_USABLE_SIZE_CONST_PTR
+#  define MALLOC_USABLE_SIZE_CONST_PTR const
+#endif
+
+typedef MALLOC_USABLE_SIZE_CONST_PTR void* usable_ptr_t;
+
+typedef size_t arena_id_t;
+
+#define ARENA_FLAG_RANDOMIZE_SMALL_MASK 0x3
+#define ARENA_FLAG_RANDOMIZE_SMALL_DEFAULT 0
+#define ARENA_FLAG_RANDOMIZE_SMALL_ENABLED 1
+#define ARENA_FLAG_RANDOMIZE_SMALL_DISABLED 2
+
+// Arenas are usually protected by a lock (ARENA_FLAG_THREAD_SAFE) however some
+// arenas are accessed by only the main thread
+// (ARENA_FLAG_THREAD_MAIN_THREAD_ONLY) and their locking can be skipped.
+#define ARENA_FLAG_THREAD_MASK 0x4
+#define ARENA_FLAG_THREAD_MAIN_THREAD_ONLY 0x4
+#define ARENA_FLAG_THREAD_SAFE 0x0
+
+typedef struct arena_params_s {
+  size_t mMaxDirty;
+  // Arena specific modifiers which override the value passed to
+  // moz_set_max_dirty_page_modifier. If value > 0 is passed to that function,
+  // and mMaxDirtyIncreaseOverride != 0, mMaxDirtyIncreaseOverride will be used
+  // instead, and similarly if value < 0 is passed and mMaxDirtyDecreaseOverride
+  // != 0, mMaxDirtyDecreaseOverride will be used as the modifier.
+  int32_t mMaxDirtyIncreaseOverride;
+  int32_t mMaxDirtyDecreaseOverride;
+
+  uint32_t mFlags;
+
+#ifdef __cplusplus
+  arena_params_s()
+      : mMaxDirty(0),
+        mMaxDirtyIncreaseOverride(0),
+        mMaxDirtyDecreaseOverride(0),
+        mFlags(0) {}
+#endif
+} arena_params_t;
+
+// jemalloc_stats() is not a stable interface.  When using jemalloc_stats_t, be
+// sure that the compiled results of jemalloc.c are in sync with this header
+// file.
+typedef struct {
+  // Run-time configuration settings.
+  bool opt_junk;            // Fill allocated memory with kAllocJunk?
+  bool opt_zero;            // Fill allocated memory with 0x0?
+  size_t narenas;           // Number of arenas.
+  size_t quantum;           // Allocation quantum.
+  size_t quantum_max;       // Max quantum-spaced allocation size.
+  size_t quantum_wide;      // Allocation quantum (QuantuWide).
+  size_t quantum_wide_max;  // Max quantum-wide-spaced allocation size.
+  size_t subpage_max;       // Max subpage allocation size.
+  size_t large_max;         // Max sub-chunksize allocation size.
+  size_t chunksize;         // Size of each virtual memory mapping.
+  size_t page_size;         // Size of pages.
+  size_t dirty_max;         // Max dirty pages per arena.
+
+  // Current memory usage statistics.
+  size_t mapped;       // Bytes mapped (not necessarily committed).
+  size_t allocated;    // Bytes allocated (committed, in use by application).
+  size_t waste;        // Bytes committed, not in use by the
+                       // application, and not intentionally left
+                       // unused (i.e., not dirty).
+  size_t page_cache;   // Committed, unused pages kept around as a
+                       // cache.  (jemalloc calls these "dirty".)
+  size_t bookkeeping;  // Committed bytes used internally by the
+                       // allocator.
+  size_t bin_unused;   // Bytes committed to a bin but currently unused.
+} jemalloc_stats_t;
+
+typedef struct {
+  size_t size;               // The size of objects in this bin, zero if this
+                             // bin stats array entry is unused (no more bins).
+  size_t num_non_full_runs;  // The number of non-full runs
+  size_t num_runs;           // The number of runs in this bin
+  size_t bytes_unused;       // The unallocated bytes across all these bins
+  size_t bytes_total;        // The total storage area for runs in this bin,
+  size_t bytes_per_run;      // The number of bytes per run, including headers.
+} jemalloc_bin_stats_t;
+
+enum PtrInfoTag {
+  // The pointer is not currently known to the allocator.
+  // 'addr', 'size', and 'arenaId' are always 0.
+  TagUnknown,
+
+  // The pointer is within a live allocation.
+  // 'addr', 'size', and 'arenaId' describe the allocation.
+  TagLiveAlloc,
+
+  // The pointer is within a small freed allocation.
+  // 'addr', 'size', and 'arenaId' describe the allocation.
+  TagFreedAlloc,
+
+  // The pointer is within a freed page. Details about the original
+  // allocation, including its size, are not available.
+  // 'addr', 'size', and 'arenaId' describe the page.
+  TagFreedPage,
+};
+
+// The information in jemalloc_ptr_info_t could be represented in a variety of
+// ways. The chosen representation has the following properties.
+// - The number of fields is minimized.
+// - The 'tag' field unambiguously defines the meaning of the subsequent fields.
+// Helper functions are used to group together related categories of tags.
+typedef struct jemalloc_ptr_info_s {
+  enum PtrInfoTag tag;
+  void* addr;   // meaning depends on tag; see above
+  size_t size;  // meaning depends on tag; see above
+
+#ifdef MOZ_DEBUG
+  arena_id_t arenaId;  // meaning depends on tag; see above
+#endif
+
+#ifdef __cplusplus
+  jemalloc_ptr_info_s() = default;
+  jemalloc_ptr_info_s(enum PtrInfoTag aTag, void* aAddr, size_t aSize,
+                      arena_id_t aArenaId)
+      : tag(aTag),
+        addr(aAddr),
+        size(aSize)
+#  ifdef MOZ_DEBUG
+        ,
+        arenaId(aArenaId)
+#  endif
+  {
+  }
+#endif
+} jemalloc_ptr_info_t;
+
+static inline bool jemalloc_ptr_is_live(jemalloc_ptr_info_t* info) {
+  return info->tag == TagLiveAlloc;
+}
+
+static inline bool jemalloc_ptr_is_freed(jemalloc_ptr_info_t* info) {
+  return info->tag == TagFreedAlloc || info->tag == TagFreedPage;
+}
+
+static inline bool jemalloc_ptr_is_freed_page(jemalloc_ptr_info_t* info) {
+  return info->tag == TagFreedPage;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // _JEMALLOC_TYPES_H_
diff --git a/memory/build/mozmemory.h b/memory/build/mozmemory.h
new file mode 100644
index 0000000000..bd009052a0
--- /dev/null
+++ b/memory/build/mozmemory.h
@@ -0,0 +1,81 @@
+/* -*- 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/. */
+
+#ifndef mozmemory_h
+#define mozmemory_h
+
+// This header is meant to be used when the following functions are
+// necessary:
+//   - malloc_good_size (used to be called je_malloc_usable_in_advance)
+//   - jemalloc_stats
+//   - jemalloc_stats_num_bins
+//   - jemalloc_purge_freed_pages
+//   - jemalloc_free_dirty_pages
+//   - jemalloc_thread_local_arena
+//   - jemalloc_ptr_info
+
+#ifdef MALLOC_H
+#  include MALLOC_H
+#endif
+#include "mozmemory_wrap.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Types.h"
+#include "mozjemalloc_types.h"
+#include "stdbool.h"
+
+#ifdef MOZ_MEMORY
+// On OSX, malloc/malloc.h contains the declaration for malloc_good_size,
+// which will call back in jemalloc, through the zone allocator so just use it.
+#  ifndef XP_DARWIN
+MOZ_MEMORY_API size_t malloc_good_size_impl(size_t size);
+
+// Note: the MOZ_GLUE_IN_PROGRAM ifdef below is there to avoid -Werror turning
+// the protective if into errors. MOZ_GLUE_IN_PROGRAM is what triggers MFBT_API
+// to use weak imports.
+static inline size_t _malloc_good_size(size_t size) {
+#    if defined(MOZ_GLUE_IN_PROGRAM) && !defined(IMPL_MFBT)
+  if (!malloc_good_size) return size;
+#    endif
+  return malloc_good_size_impl(size);
+}
+
+#    define malloc_good_size _malloc_good_size
+#  endif
+
+#  define MALLOC_DECL(name, return_type, ...) \
+    MOZ_JEMALLOC_API return_type name(__VA_ARGS__);
+#  define MALLOC_FUNCS MALLOC_FUNCS_JEMALLOC
+#  include "malloc_decls.h"
+
+// jemalloc_stats may only be called on the main thread so that it can access
+// main thread only arenas.
+#  ifdef __cplusplus
+static inline void jemalloc_stats(jemalloc_stats_t* aStats,
+                                  jemalloc_bin_stats_t* aBinStats = nullptr) {
+  jemalloc_stats_internal(aStats, aBinStats);
+}
+#  else
+static inline void jemalloc_stats(jemalloc_stats_t* aStats) {
+  jemalloc_stats_internal(aStats, NULL);
+}
+#  endif
+
+#endif  // MOZ_MEMORY
+
+#define NOTHROW_MALLOC_DECL(name, return_type, ...) \
+  MOZ_JEMALLOC_API return_type name(__VA_ARGS__) noexcept(true);
+#define MALLOC_DECL(name, return_type, ...) \
+  MOZ_JEMALLOC_API return_type name(__VA_ARGS__);
+#define MALLOC_FUNCS MALLOC_FUNCS_ARENA
+#include "malloc_decls.h"
+
+#ifdef __cplusplus
+#  define moz_create_arena() moz_create_arena_with_params(nullptr)
+#else
+#  define moz_create_arena() moz_create_arena_with_params(NULL)
+#endif
+
+#endif  // mozmemory_h
diff --git a/memory/build/mozmemory_utils.h b/memory/build/mozmemory_utils.h
new file mode 100644
index 0000000000..af9e96b4c7
--- /dev/null
+++ b/memory/build/mozmemory_utils.h
@@ -0,0 +1,75 @@
+/* -*- 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/. */
+
+#ifndef mozjemalloc_utils_h
+#define mozjemalloc_utils_h
+
+#include <optional>
+#include <type_traits>
+
+#if defined(MOZ_MEMORY) && defined(XP_WIN)
+#  include "mozmemory_wrap.h"
+#endif
+
+namespace mozilla {
+
+namespace detail {
+// Helper for StallAndRetry error messages.
+template <typename T>
+constexpr bool is_std_optional = false;
+template <typename T>
+constexpr bool is_std_optional<std::optional<T>> = true;
+}  // namespace detail
+
+struct StallSpecs {
+  // Maximum number of retry-attempts before giving up.
+  size_t maxAttempts;
+  // Delay time between successive events.
+  size_t delayMs;
+
+  // Retry a fallible operation until it succeeds or until we've run out of
+  // retries.
+  //
+  // Note that this invokes `aDelayFunc` immediately upon being called! It's
+  // intended for use in the unhappy path, after an initial attempt has failed.
+  //
+  // The function type here may be read:
+  // ```
+  // fn StallAndRetry<R>(
+  //     delay_func: impl Fn(usize) -> (),
+  //     operation: impl Fn() -> Option<R>,
+  // ) -> Option<R>;
+  // ```
+  //
+  template <typename DelayFunc, typename OpFunc>
+  auto StallAndRetry(DelayFunc&& aDelayFunc, OpFunc&& aOperation) const
+      -> decltype(aOperation()) {
+    {
+      // Explicit typecheck for OpFunc, to provide an explicit error message.
+      using detail::is_std_optional;
+      static_assert(is_std_optional<decltype(aOperation())>,
+                    "aOperation() must return std::optional");
+
+      // (clang's existing error messages suffice for aDelayFunc.)
+    }
+
+    for (size_t i = 0; i < maxAttempts; ++i) {
+      aDelayFunc(delayMs);
+      if (const auto opt = aOperation()) {
+        return opt;
+      }
+    }
+    return std::nullopt;
+  }
+};
+
+#if defined(MOZ_MEMORY) && defined(XP_WIN)
+MOZ_JEMALLOC_API StallSpecs GetAllocatorStallSpecs();
+#endif
+
+}  // namespace mozilla
+
+#endif  // mozjemalloc_utils_h
diff --git a/memory/build/mozmemory_wrap.cpp b/memory/build/mozmemory_wrap.cpp
new file mode 100644
index 0000000000..3420fd9693
--- /dev/null
+++ b/memory/build/mozmemory_wrap.cpp
@@ -0,0 +1,145 @@
+/* -*- 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 <string.h>
+#include "mozmemory_wrap.h"
+#include "mozilla/Types.h"
+
+// Declare malloc implementation functions with the right return and
+// argument types.
+#define NOTHROW_MALLOC_DECL(name, return_type, ...) \
+  MOZ_MEMORY_API return_type name##_impl(__VA_ARGS__) noexcept(true);
+#define MALLOC_DECL(name, return_type, ...) \
+  MOZ_MEMORY_API return_type name##_impl(__VA_ARGS__);
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC
+#include "malloc_decls.h"
+
+// strndup and strdup may be defined as macros in string.h, which would
+// clash with the definitions below.
+#undef strndup
+#undef strdup
+
+MOZ_MEMORY_API char* strndup_impl(const char* src, size_t len) {
+  char* dst = (char*)malloc_impl(len + 1);
+  if (dst) {
+    strncpy(dst, src, len);
+    dst[len] = '\0';
+  }
+  return dst;
+}
+
+MOZ_MEMORY_API char* strdup_impl(const char* src) {
+  size_t len = strlen(src);
+  return strndup_impl(src, len);
+}
+
+#ifdef ANDROID
+#  include <stdarg.h>
+#  include <stdio.h>
+
+MOZ_MEMORY_API int vasprintf_impl(char** str, const char* fmt, va_list ap) {
+  char *ptr, *_ptr;
+  int ret;
+
+  if (str == NULL || fmt == NULL) {
+    return -1;
+  }
+
+  ptr = (char*)malloc_impl(128);
+  if (ptr == NULL) {
+    *str = NULL;
+    return -1;
+  }
+
+  ret = vsnprintf(ptr, 128, fmt, ap);
+  if (ret < 0) {
+    free_impl(ptr);
+    *str = NULL;
+    return -1;
+  }
+
+  _ptr = reinterpret_cast<char*>(realloc_impl(ptr, ret + 1));
+  if (_ptr == NULL) {
+    free_impl(ptr);
+    *str = NULL;
+    return -1;
+  }
+
+  *str = _ptr;
+
+  return ret;
+}
+
+MOZ_MEMORY_API int asprintf_impl(char** str, const char* fmt, ...) {
+  int ret;
+  va_list ap;
+  va_start(ap, fmt);
+
+  ret = vasprintf_impl(str, fmt, ap);
+
+  va_end(ap);
+
+  return ret;
+}
+#endif
+
+#ifdef XP_WIN
+#  include <wchar.h>
+
+// We also need to provide our own impl of wcsdup so that we don't ask
+// the CRT for memory from its heap (which will then be unfreeable).
+MOZ_MEMORY_API wchar_t* wcsdup_impl(const wchar_t* src) {
+  size_t len = wcslen(src);
+  wchar_t* dst = (wchar_t*)malloc_impl((len + 1) * sizeof(wchar_t));
+  if (dst) wcsncpy(dst, src, len + 1);
+  return dst;
+}
+
+MOZ_MEMORY_API void* _aligned_malloc_impl(size_t size, size_t alignment) {
+  return memalign_impl(alignment, size);
+}
+
+#  ifdef __MINGW32__
+MOZ_BEGIN_EXTERN_C
+// As in mozjemalloc.cpp, we generate aliases for functions
+// redirected in mozglue.def
+void* _aligned_malloc(size_t size, size_t alignment)
+    __attribute__((alias(MOZ_STRINGIFY(_aligned_malloc_impl))));
+void _aligned_free(void* aPtr) __attribute__((alias(MOZ_STRINGIFY(free_impl))));
+
+char* strndup(const char* src, size_t len)
+    __attribute__((alias(MOZ_STRINGIFY(strdup_impl))));
+char* strdup(const char* src)
+    __attribute__((alias(MOZ_STRINGIFY(strdup_impl))));
+char* _strdup(const char* src)
+    __attribute__((alias(MOZ_STRINGIFY(strdup_impl))));
+wchar_t* wcsdup(const wchar_t* src)
+    __attribute__((alias(MOZ_STRINGIFY(wcsdup_impl))));
+wchar_t* _wcsdup(const wchar_t* src)
+    __attribute__((alias(MOZ_STRINGIFY(wcsdup_impl))));
+
+// jemalloc has _aligned_malloc, and friends. libc++.a contains
+// references to __imp__aligned_malloc (and friends) because it
+// is declared dllimport in the headers.
+//
+// The linker sees jemalloc's _aligned_malloc symbol in our objects,
+// but then libc++.a comes along and needs __imp__aligned_malloc, which
+// pulls in those parts of libucrt.a (or libmsvcrt.a in practice),
+// which define both __imp__aligned_malloc and _aligned_malloc, and
+// this causes a conflict.  (And repeat for each of the symbols defined
+// here.)
+//
+// The fix is to define not only an _aligned_malloc symbol (via an
+// alias), but also define the __imp__aligned_malloc pointer to it.
+// This prevents those parts of libucrt from being pulled in and causing
+// conflicts.
+// This is done with __MINGW_IMP_SYMBOL to handle x86/x64 differences.
+void (*__MINGW_IMP_SYMBOL(_aligned_free))(void*) = _aligned_free;
+void* (*__MINGW_IMP_SYMBOL(_aligned_malloc))(size_t, size_t) = _aligned_malloc;
+char* (*__MINGW_IMP_SYMBOL(_strdup))(const char* src) = _strdup;
+MOZ_END_EXTERN_C
+#  endif
+#endif  // XP_WIN
diff --git a/memory/build/mozmemory_wrap.h b/memory/build/mozmemory_wrap.h
new file mode 100644
index 0000000000..92d0a1176a
--- /dev/null
+++ b/memory/build/mozmemory_wrap.h
@@ -0,0 +1,166 @@
+/* -*- 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/. */
+
+#ifndef mozmemory_wrap_h
+#define mozmemory_wrap_h
+
+// This header contains #defines which tweak the names of various memory
+// allocation functions.
+//
+// There are several types of functions related to memory allocation
+// that are meant to be used publicly by the Gecko codebase:
+//
+// - malloc implementation functions:
+//   - malloc
+//   - posix_memalign
+//   - aligned_alloc
+//   - calloc
+//   - realloc
+//   - free
+//   - memalign
+//   - valloc
+//   - malloc_usable_size
+//   - malloc_good_size
+//   Some of these functions are specific to some systems, but for
+//   convenience, they are treated as being cross-platform, and available
+//   as such.
+//
+// - duplication functions:
+//   - strndup
+//   - strdup
+//   - wcsdup (Windows only)
+//
+// - jemalloc specific functions:
+//   - jemalloc_stats
+//   - jemalloc_stats_num_bins
+//   - jemalloc_purge_freed_pages
+//   - jemalloc_free_dirty_pages
+//   - jemalloc_thread_local_arena
+//   - jemalloc_ptr_info
+//   (these functions are native to mozjemalloc)
+//
+// These functions are all exported as part of libmozglue (see
+// $(topsrcdir)/mozglue/build/Makefile.in), with a few implementation
+// peculiarities:
+//
+// - On Windows, the malloc implementation functions are all prefixed with
+//   "je_", the duplication functions are prefixed with "wrap_", and jemalloc
+//   specific functions are left unprefixed. All these functions are however
+//   aliased when exporting them, such that the resulting mozglue.dll exports
+//   them unprefixed (see $(topsrcdir)/mozglue/build/mozglue.def.in). The
+//   prefixed malloc implementation and duplication functions are not
+//   exported.
+//
+// - On MacOSX, the system libc has a zone allocator, which allows us to
+//   hook custom malloc implementation functions without exporting them.
+//   However, since we want things in Firefox to skip the system zone
+//   allocator, the malloc implementation functions are all exported
+//   unprefixed, as well as duplication functions.
+//   Jemalloc-specific functions are also left unprefixed.
+//
+// - On Android all functions are left unprefixed.
+//
+// - On other systems (mostly Linux), all functions are left unprefixed.
+//
+// On all platforms, C++ allocation functions are also exported.
+//
+// Proper exporting of the various functions is done with the MOZ_MEMORY_API
+// and MOZ_JEMALLOC_API macros. MOZ_MEMORY_API is meant to be used for malloc
+// implementation and duplication functions, while MOZ_JEMALLOC_API is
+// dedicated to jemalloc specific functions.
+//
+//
+// All these functions are meant to be called with no prefix from Gecko code.
+// In most cases, this is because that's how they are available at runtime.
+// However, on Android, this relies on faulty.lib (the custom dynamic linker)
+// resolving mozglue symbols before libc symbols, which is guaranteed by the
+// way faulty.lib works (it respects the DT_NEEDED order, and libc always
+// appears after mozglue ; which we double check when building anyways)
+//
+//
+// Within libmozglue (when MOZ_MEMORY_IMPL is defined), all the functions
+// should be suffixed with "_impl" both for declarations and use.
+// That is, the implementation declaration for e.g. strdup would look like:
+//   char* strdup_impl(const char *)
+// That implementation would call malloc by using "malloc_impl".
+
+#if defined(MOZ_MEMORY_IMPL) && !defined(IMPL_MFBT)
+#  ifdef MFBT_API  // mozilla/Types.h was already included
+#    error mozmemory_wrap.h has to be included before mozilla/Types.h when MOZ_MEMORY_IMPL is set and IMPL_MFBT is not.
+#  endif
+#  define IMPL_MFBT
+#endif
+
+#include "mozilla/Types.h"
+
+#ifndef MOZ_EXTERN_C
+#  ifdef __cplusplus
+#    define MOZ_EXTERN_C extern "C"
+#  else
+#    define MOZ_EXTERN_C
+#  endif
+#endif
+
+#ifdef MOZ_MEMORY_IMPL
+#  define MOZ_JEMALLOC_API MOZ_EXTERN_C MFBT_API
+#  if defined(XP_WIN)
+#    define mozmem_malloc_impl(a) je_##a
+#  else
+#    define MOZ_MEMORY_API MOZ_EXTERN_C MFBT_API
+#  endif
+#endif
+#ifdef XP_WIN
+#  define mozmem_dup_impl(a) wrap_##a
+#endif
+
+#if !defined(MOZ_MEMORY_IMPL)
+#  define MOZ_MEMORY_API MOZ_EXTERN_C MFBT_API
+#  define MOZ_JEMALLOC_API MOZ_EXTERN_C MFBT_API
+#endif
+
+#ifndef MOZ_MEMORY_API
+#  define MOZ_MEMORY_API MOZ_EXTERN_C
+#endif
+#ifndef MOZ_JEMALLOC_API
+#  define MOZ_JEMALLOC_API MOZ_EXTERN_C
+#endif
+
+#ifndef mozmem_malloc_impl
+#  define mozmem_malloc_impl(a) a
+#endif
+#ifndef mozmem_dup_impl
+#  define mozmem_dup_impl(a) a
+#endif
+
+// Malloc implementation functions
+#define malloc_impl mozmem_malloc_impl(malloc)
+#define posix_memalign_impl mozmem_malloc_impl(posix_memalign)
+#define aligned_alloc_impl mozmem_malloc_impl(aligned_alloc)
+#define calloc_impl mozmem_malloc_impl(calloc)
+#define realloc_impl mozmem_malloc_impl(realloc)
+#define free_impl mozmem_malloc_impl(free)
+#define memalign_impl mozmem_malloc_impl(memalign)
+#define valloc_impl mozmem_malloc_impl(valloc)
+#define malloc_usable_size_impl mozmem_malloc_impl(malloc_usable_size)
+#define malloc_good_size_impl mozmem_malloc_impl(malloc_good_size)
+
+// Duplication functions
+#define strndup_impl mozmem_dup_impl(strndup)
+#define strdup_impl mozmem_dup_impl(strdup)
+#ifdef XP_WIN
+#  define wcsdup_impl mozmem_dup_impl(wcsdup)
+#  define _aligned_malloc_impl mozmem_dup_impl(_aligned_malloc)
+#endif
+
+// String functions
+#ifdef ANDROID
+// Bug 801571 and Bug 879668, libstagefright uses vasprintf, causing malloc()/
+// free() to be mismatched between bionic and mozglue implementation.
+#  define vasprintf_impl mozmem_dup_impl(vasprintf)
+#  define asprintf_impl mozmem_dup_impl(asprintf)
+#endif
+
+#endif  // mozmemory_wrap_h
diff --git a/memory/build/rb.h b/memory/build/rb.h
new file mode 100644
index 0000000000..418d206911
--- /dev/null
+++ b/memory/build/rb.h
@@ -0,0 +1,741 @@
+/* -*- 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/. */
+
+// Portions of this file were originally under the following license:
+//
+// Copyright (C) 2008 Jason Evans <jasone@FreeBSD.org>.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1. Redistributions of source code must retain the above copyright
+//    notice(s), this list of conditions and the following disclaimer
+//    unmodified other than the allowable addition of one or more
+//    copyright notices.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice(s), this list of conditions and the following disclaimer in
+//    the documentation and/or other materials provided with the
+//    distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+// PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// ****************************************************************************
+//
+// C++ template implementation of left-leaning red-black trees.
+//
+// All operations are done non-recursively.  Parent pointers are not used, and
+// color bits are stored in the least significant bit of right-child pointers,
+// thus making node linkage as compact as is possible for red-black trees.
+//
+// The RedBlackTree template expects two type arguments: the type of the nodes,
+// containing a RedBlackTreeNode, and a trait providing two methods:
+//  - a GetTreeNode method that returns a reference to the RedBlackTreeNode
+//    corresponding to a given node with the following signature:
+//      static RedBlackTreeNode<T>& GetTreeNode(T*)
+//  - a Compare function with the following signature:
+//      static Order Compare(T* aNode, T* aOther)
+//                              ^^^^^
+//                           or aKey
+//
+// Interpretation of comparision function return values:
+//
+//   Order::eLess: aNode <  aOther
+//   Order::eEqual: aNode == aOther
+//   Order::eGreater: aNode >  aOther
+//
+// In all cases, the aNode or aKey argument is the first argument to the
+// comparison function, which makes it possible to write comparison functions
+// that treat the first argument specially.
+//
+// ***************************************************************************
+
+#ifndef RB_H_
+#define RB_H_
+
+#include "mozilla/Alignment.h"
+#include "mozilla/Assertions.h"
+#include "Utils.h"
+
+enum NodeColor {
+  Black = 0,
+  Red = 1,
+};
+
+// Node structure.
+template <typename T>
+class RedBlackTreeNode {
+  T* mLeft;
+  // The lowest bit is the color
+  T* mRightAndColor;
+
+ public:
+  T* Left() { return mLeft; }
+
+  void SetLeft(T* aValue) { mLeft = aValue; }
+
+  T* Right() {
+    return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(mRightAndColor) &
+                                uintptr_t(~1));
+  }
+
+  void SetRight(T* aValue) {
+    mRightAndColor = reinterpret_cast<T*>(
+        (reinterpret_cast<uintptr_t>(aValue) & uintptr_t(~1)) | Color());
+  }
+
+  NodeColor Color() {
+    return static_cast<NodeColor>(reinterpret_cast<uintptr_t>(mRightAndColor) &
+                                  1);
+  }
+
+  bool IsBlack() { return Color() == NodeColor::Black; }
+
+  bool IsRed() { return Color() == NodeColor::Red; }
+
+  void SetColor(NodeColor aColor) {
+    mRightAndColor = reinterpret_cast<T*>(
+        (reinterpret_cast<uintptr_t>(mRightAndColor) & uintptr_t(~1)) | aColor);
+  }
+};
+
+// Tree structure.
+template <typename T, typename Trait>
+class RedBlackTree {
+ public:
+  void Init() { mRoot = nullptr; }
+
+  T* First(T* aStart = nullptr) { return First(TreeNode(aStart)).Get(); }
+
+  T* Last(T* aStart = nullptr) { return Last(TreeNode(aStart)).Get(); }
+
+  T* Next(T* aNode) { return Next(TreeNode(aNode)).Get(); }
+
+  T* Prev(T* aNode) { return Prev(TreeNode(aNode)).Get(); }
+
+  T* Search(T* aKey) { return Search(TreeNode(aKey)).Get(); }
+
+  // Find a match if it exists. Otherwise, find the next greater node, if one
+  // exists.
+  T* SearchOrNext(T* aKey) { return SearchOrNext(TreeNode(aKey)).Get(); }
+
+  void Insert(T* aNode) { Insert(TreeNode(aNode)); }
+
+  void Remove(T* aNode) { Remove(TreeNode(aNode)); }
+
+  // Helper class to avoid having all the tree traversal code further below
+  // have to use Trait::GetTreeNode and do manual null pointer checks, adding
+  // visual noise. Practically speaking TreeNode(nullptr) acts as a virtual
+  // sentinel, that loops back to itself for Left() and Right() and is always
+  // black.
+  class TreeNode {
+   public:
+    constexpr TreeNode() : mNode(nullptr) {}
+
+    MOZ_IMPLICIT TreeNode(T* aNode) : mNode(aNode) {}
+
+    TreeNode& operator=(TreeNode aOther) {
+      mNode = aOther.mNode;
+      return *this;
+    }
+
+    TreeNode Left() {
+      return TreeNode(mNode ? Trait::GetTreeNode(mNode).Left() : nullptr);
+    }
+
+    void SetLeft(TreeNode aNode) {
+      MOZ_RELEASE_ASSERT(mNode);
+      Trait::GetTreeNode(mNode).SetLeft(aNode.mNode);
+    }
+
+    TreeNode Right() {
+      return TreeNode(mNode ? Trait::GetTreeNode(mNode).Right() : nullptr);
+    }
+
+    void SetRight(TreeNode aNode) {
+      MOZ_RELEASE_ASSERT(mNode);
+      Trait::GetTreeNode(mNode).SetRight(aNode.mNode);
+    }
+
+    NodeColor Color() {
+      return mNode ? Trait::GetTreeNode(mNode).Color() : NodeColor::Black;
+    }
+
+    bool IsRed() { return Color() == NodeColor::Red; }
+
+    bool IsBlack() { return Color() == NodeColor::Black; }
+
+    void SetColor(NodeColor aColor) {
+      MOZ_RELEASE_ASSERT(mNode);
+      Trait::GetTreeNode(mNode).SetColor(aColor);
+    }
+
+    T* Get() { return mNode; }
+
+    MOZ_IMPLICIT operator bool() { return !!mNode; }
+
+    bool operator==(TreeNode& aOther) { return mNode == aOther.mNode; }
+
+   private:
+    T* mNode;
+  };
+
+ private:
+  // Ideally we'd use a TreeNode for mRoot, but we need RedBlackTree to stay
+  // a POD type to avoid a static initializer for gArenas.
+  T* mRoot;
+
+  TreeNode First(TreeNode aStart) {
+    TreeNode ret;
+    for (ret = aStart ? aStart : mRoot; ret.Left(); ret = ret.Left()) {
+    }
+    return ret;
+  }
+
+  TreeNode Last(TreeNode aStart) {
+    TreeNode ret;
+    for (ret = aStart ? aStart : mRoot; ret.Right(); ret = ret.Right()) {
+    }
+    return ret;
+  }
+
+  TreeNode Next(TreeNode aNode) {
+    TreeNode ret;
+    if (aNode.Right()) {
+      ret = First(aNode.Right());
+    } else {
+      TreeNode rbp_n_t = mRoot;
+      MOZ_ASSERT(rbp_n_t);
+      ret = nullptr;
+      while (true) {
+        Order rbp_n_cmp = Trait::Compare(aNode.Get(), rbp_n_t.Get());
+        if (rbp_n_cmp == Order::eLess) {
+          ret = rbp_n_t;
+          rbp_n_t = rbp_n_t.Left();
+        } else if (rbp_n_cmp == Order::eGreater) {
+          rbp_n_t = rbp_n_t.Right();
+        } else {
+          break;
+        }
+        MOZ_ASSERT(rbp_n_t);
+      }
+    }
+    return ret;
+  }
+
+  TreeNode Prev(TreeNode aNode) {
+    TreeNode ret;
+    if (aNode.Left()) {
+      ret = Last(aNode.Left());
+    } else {
+      TreeNode rbp_p_t = mRoot;
+      MOZ_ASSERT(rbp_p_t);
+      ret = nullptr;
+      while (true) {
+        Order rbp_p_cmp = Trait::Compare(aNode.Get(), rbp_p_t.Get());
+        if (rbp_p_cmp == Order::eLess) {
+          rbp_p_t = rbp_p_t.Left();
+        } else if (rbp_p_cmp == Order::eGreater) {
+          ret = rbp_p_t;
+          rbp_p_t = rbp_p_t.Right();
+        } else {
+          break;
+        }
+        MOZ_ASSERT(rbp_p_t);
+      }
+    }
+    return ret;
+  }
+
+  TreeNode Search(TreeNode aKey) {
+    TreeNode ret = mRoot;
+    Order rbp_se_cmp;
+    while (ret && (rbp_se_cmp = Trait::Compare(aKey.Get(), ret.Get())) !=
+                      Order::eEqual) {
+      if (rbp_se_cmp == Order::eLess) {
+        ret = ret.Left();
+      } else {
+        ret = ret.Right();
+      }
+    }
+    return ret;
+  }
+
+  TreeNode SearchOrNext(TreeNode aKey) {
+    TreeNode ret = nullptr;
+    TreeNode rbp_ns_t = mRoot;
+    while (rbp_ns_t) {
+      Order rbp_ns_cmp = Trait::Compare(aKey.Get(), rbp_ns_t.Get());
+      if (rbp_ns_cmp == Order::eLess) {
+        ret = rbp_ns_t;
+        rbp_ns_t = rbp_ns_t.Left();
+      } else if (rbp_ns_cmp == Order::eGreater) {
+        rbp_ns_t = rbp_ns_t.Right();
+      } else {
+        ret = rbp_ns_t;
+        break;
+      }
+    }
+    return ret;
+  }
+
+  void Insert(TreeNode aNode) {
+    // rbp_i_s is only used as a placeholder for its RedBlackTreeNode. Use
+    // AlignedStorage2 to avoid running the TreeNode base class constructor.
+    mozilla::AlignedStorage2<T> rbp_i_s;
+    TreeNode rbp_i_g, rbp_i_p, rbp_i_c, rbp_i_t, rbp_i_u;
+    Order rbp_i_cmp = Order::eEqual;
+    rbp_i_g = nullptr;
+    rbp_i_p = rbp_i_s.addr();
+    rbp_i_p.SetLeft(mRoot);
+    rbp_i_p.SetRight(nullptr);
+    rbp_i_p.SetColor(NodeColor::Black);
+    rbp_i_c = mRoot;
+    // Iteratively search down the tree for the insertion point,
+    // splitting 4-nodes as they are encountered. At the end of each
+    // iteration, rbp_i_g->rbp_i_p->rbp_i_c is a 3-level path down
+    // the tree, assuming a sufficiently deep tree.
+    while (rbp_i_c) {
+      rbp_i_t = rbp_i_c.Left();
+      rbp_i_u = rbp_i_t.Left();
+      if (rbp_i_t.IsRed() && rbp_i_u.IsRed()) {
+        // rbp_i_c is the top of a logical 4-node, so split it.
+        // This iteration does not move down the tree, due to the
+        // disruptiveness of node splitting.
+        //
+        // Rotate right.
+        rbp_i_t = RotateRight(rbp_i_c);
+        // Pass red links up one level.
+        rbp_i_u = rbp_i_t.Left();
+        rbp_i_u.SetColor(NodeColor::Black);
+        if (rbp_i_p.Left() == rbp_i_c) {
+          rbp_i_p.SetLeft(rbp_i_t);
+          rbp_i_c = rbp_i_t;
+        } else {
+          // rbp_i_c was the right child of rbp_i_p, so rotate
+          // left in order to maintain the left-leaning invariant.
+          MOZ_ASSERT(rbp_i_p.Right() == rbp_i_c);
+          rbp_i_p.SetRight(rbp_i_t);
+          rbp_i_u = LeanLeft(rbp_i_p);
+          if (rbp_i_g.Left() == rbp_i_p) {
+            rbp_i_g.SetLeft(rbp_i_u);
+          } else {
+            MOZ_ASSERT(rbp_i_g.Right() == rbp_i_p);
+            rbp_i_g.SetRight(rbp_i_u);
+          }
+          rbp_i_p = rbp_i_u;
+          rbp_i_cmp = Trait::Compare(aNode.Get(), rbp_i_p.Get());
+          if (rbp_i_cmp == Order::eLess) {
+            rbp_i_c = rbp_i_p.Left();
+          } else {
+            MOZ_ASSERT(rbp_i_cmp == Order::eGreater);
+            rbp_i_c = rbp_i_p.Right();
+          }
+          continue;
+        }
+      }
+      rbp_i_g = rbp_i_p;
+      rbp_i_p = rbp_i_c;
+      rbp_i_cmp = Trait::Compare(aNode.Get(), rbp_i_c.Get());
+      if (rbp_i_cmp == Order::eLess) {
+        rbp_i_c = rbp_i_c.Left();
+      } else {
+        MOZ_ASSERT(rbp_i_cmp == Order::eGreater);
+        rbp_i_c = rbp_i_c.Right();
+      }
+    }
+    // rbp_i_p now refers to the node under which to insert.
+    aNode.SetLeft(nullptr);
+    aNode.SetRight(nullptr);
+    aNode.SetColor(NodeColor::Red);
+    if (rbp_i_cmp == Order::eGreater) {
+      rbp_i_p.SetRight(aNode);
+      rbp_i_t = LeanLeft(rbp_i_p);
+      if (rbp_i_g.Left() == rbp_i_p) {
+        rbp_i_g.SetLeft(rbp_i_t);
+      } else if (rbp_i_g.Right() == rbp_i_p) {
+        rbp_i_g.SetRight(rbp_i_t);
+      }
+    } else {
+      rbp_i_p.SetLeft(aNode);
+    }
+    // Update the root and make sure that it is black.
+    TreeNode root = TreeNode(rbp_i_s.addr()).Left();
+    root.SetColor(NodeColor::Black);
+    mRoot = root.Get();
+  }
+
+  void Remove(TreeNode aNode) {
+    // rbp_r_s is only used as a placeholder for its RedBlackTreeNode. Use
+    // AlignedStorage2 to avoid running the TreeNode base class constructor.
+    mozilla::AlignedStorage2<T> rbp_r_s;
+    TreeNode rbp_r_p, rbp_r_c, rbp_r_xp, rbp_r_t, rbp_r_u;
+    Order rbp_r_cmp;
+    rbp_r_p = TreeNode(rbp_r_s.addr());
+    rbp_r_p.SetLeft(mRoot);
+    rbp_r_p.SetRight(nullptr);
+    rbp_r_p.SetColor(NodeColor::Black);
+    rbp_r_c = mRoot;
+    rbp_r_xp = nullptr;
+    // Iterate down the tree, but always transform 2-nodes to 3- or
+    // 4-nodes in order to maintain the invariant that the current
+    // node is not a 2-node. This allows simple deletion once a leaf
+    // is reached. Handle the root specially though, since there may
+    // be no way to convert it from a 2-node to a 3-node.
+    rbp_r_cmp = Trait::Compare(aNode.Get(), rbp_r_c.Get());
+    if (rbp_r_cmp == Order::eLess) {
+      rbp_r_t = rbp_r_c.Left();
+      rbp_r_u = rbp_r_t.Left();
+      if (rbp_r_t.IsBlack() && rbp_r_u.IsBlack()) {
+        // Apply standard transform to prepare for left move.
+        rbp_r_t = MoveRedLeft(rbp_r_c);
+        rbp_r_t.SetColor(NodeColor::Black);
+        rbp_r_p.SetLeft(rbp_r_t);
+        rbp_r_c = rbp_r_t;
+      } else {
+        // Move left.
+        rbp_r_p = rbp_r_c;
+        rbp_r_c = rbp_r_c.Left();
+      }
+    } else {
+      if (rbp_r_cmp == Order::eEqual) {
+        MOZ_ASSERT(aNode == rbp_r_c);
+        if (!rbp_r_c.Right()) {
+          // Delete root node (which is also a leaf node).
+          if (rbp_r_c.Left()) {
+            rbp_r_t = LeanRight(rbp_r_c);
+            rbp_r_t.SetRight(nullptr);
+          } else {
+            rbp_r_t = nullptr;
+          }
+          rbp_r_p.SetLeft(rbp_r_t);
+        } else {
+          // This is the node we want to delete, but we will
+          // instead swap it with its successor and delete the
+          // successor. Record enough information to do the
+          // swap later. rbp_r_xp is the aNode's parent.
+          rbp_r_xp = rbp_r_p;
+          rbp_r_cmp = Order::eGreater;  // Note that deletion is incomplete.
+        }
+      }
+      if (rbp_r_cmp == Order::eGreater) {
+        if (rbp_r_c.Right().Left().IsBlack()) {
+          rbp_r_t = rbp_r_c.Left();
+          if (rbp_r_t.IsRed()) {
+            // Standard transform.
+            rbp_r_t = MoveRedRight(rbp_r_c);
+          } else {
+            // Root-specific transform.
+            rbp_r_c.SetColor(NodeColor::Red);
+            rbp_r_u = rbp_r_t.Left();
+            if (rbp_r_u.IsRed()) {
+              rbp_r_u.SetColor(NodeColor::Black);
+              rbp_r_t = RotateRight(rbp_r_c);
+              rbp_r_u = RotateLeft(rbp_r_c);
+              rbp_r_t.SetRight(rbp_r_u);
+            } else {
+              rbp_r_t.SetColor(NodeColor::Red);
+              rbp_r_t = RotateLeft(rbp_r_c);
+            }
+          }
+          rbp_r_p.SetLeft(rbp_r_t);
+          rbp_r_c = rbp_r_t;
+        } else {
+          // Move right.
+          rbp_r_p = rbp_r_c;
+          rbp_r_c = rbp_r_c.Right();
+        }
+      }
+    }
+    if (rbp_r_cmp != Order::eEqual) {
+      while (true) {
+        MOZ_ASSERT(rbp_r_p);
+        rbp_r_cmp = Trait::Compare(aNode.Get(), rbp_r_c.Get());
+        if (rbp_r_cmp == Order::eLess) {
+          rbp_r_t = rbp_r_c.Left();
+          if (!rbp_r_t) {
+            // rbp_r_c now refers to the successor node to
+            // relocate, and rbp_r_xp/aNode refer to the
+            // context for the relocation.
+            if (rbp_r_xp.Left() == aNode) {
+              rbp_r_xp.SetLeft(rbp_r_c);
+            } else {
+              MOZ_ASSERT(rbp_r_xp.Right() == (aNode));
+              rbp_r_xp.SetRight(rbp_r_c);
+            }
+            rbp_r_c.SetLeft(aNode.Left());
+            rbp_r_c.SetRight(aNode.Right());
+            rbp_r_c.SetColor(aNode.Color());
+            if (rbp_r_p.Left() == rbp_r_c) {
+              rbp_r_p.SetLeft(nullptr);
+            } else {
+              MOZ_ASSERT(rbp_r_p.Right() == rbp_r_c);
+              rbp_r_p.SetRight(nullptr);
+            }
+            break;
+          }
+          rbp_r_u = rbp_r_t.Left();
+          if (rbp_r_t.IsBlack() && rbp_r_u.IsBlack()) {
+            rbp_r_t = MoveRedLeft(rbp_r_c);
+            if (rbp_r_p.Left() == rbp_r_c) {
+              rbp_r_p.SetLeft(rbp_r_t);
+            } else {
+              rbp_r_p.SetRight(rbp_r_t);
+            }
+            rbp_r_c = rbp_r_t;
+          } else {
+            rbp_r_p = rbp_r_c;
+            rbp_r_c = rbp_r_c.Left();
+          }
+        } else {
+          // Check whether to delete this node (it has to be
+          // the correct node and a leaf node).
+          if (rbp_r_cmp == Order::eEqual) {
+            MOZ_ASSERT(aNode == rbp_r_c);
+            if (!rbp_r_c.Right()) {
+              // Delete leaf node.
+              if (rbp_r_c.Left()) {
+                rbp_r_t = LeanRight(rbp_r_c);
+                rbp_r_t.SetRight(nullptr);
+              } else {
+                rbp_r_t = nullptr;
+              }
+              if (rbp_r_p.Left() == rbp_r_c) {
+                rbp_r_p.SetLeft(rbp_r_t);
+              } else {
+                rbp_r_p.SetRight(rbp_r_t);
+              }
+              break;
+            }
+            // This is the node we want to delete, but we
+            // will instead swap it with its successor
+            // and delete the successor. Record enough
+            // information to do the swap later.
+            // rbp_r_xp is aNode's parent.
+            rbp_r_xp = rbp_r_p;
+          }
+          rbp_r_t = rbp_r_c.Right();
+          rbp_r_u = rbp_r_t.Left();
+          if (rbp_r_u.IsBlack()) {
+            rbp_r_t = MoveRedRight(rbp_r_c);
+            if (rbp_r_p.Left() == rbp_r_c) {
+              rbp_r_p.SetLeft(rbp_r_t);
+            } else {
+              rbp_r_p.SetRight(rbp_r_t);
+            }
+            rbp_r_c = rbp_r_t;
+          } else {
+            rbp_r_p = rbp_r_c;
+            rbp_r_c = rbp_r_c.Right();
+          }
+        }
+      }
+    }
+    // Update root.
+    mRoot = TreeNode(rbp_r_s.addr()).Left().Get();
+    aNode.SetLeft(nullptr);
+    aNode.SetRight(nullptr);
+    aNode.SetColor(NodeColor::Black);
+  }
+
+  TreeNode RotateLeft(TreeNode aNode) {
+    TreeNode node = aNode.Right();
+    aNode.SetRight(node.Left());
+    node.SetLeft(aNode);
+    return node;
+  }
+
+  TreeNode RotateRight(TreeNode aNode) {
+    TreeNode node = aNode.Left();
+    aNode.SetLeft(node.Right());
+    node.SetRight(aNode);
+    return node;
+  }
+
+  TreeNode LeanLeft(TreeNode aNode) {
+    TreeNode node = RotateLeft(aNode);
+    NodeColor color = aNode.Color();
+    node.SetColor(color);
+    aNode.SetColor(NodeColor::Red);
+    return node;
+  }
+
+  TreeNode LeanRight(TreeNode aNode) {
+    TreeNode node = RotateRight(aNode);
+    NodeColor color = aNode.Color();
+    node.SetColor(color);
+    aNode.SetColor(NodeColor::Red);
+    return node;
+  }
+
+  TreeNode MoveRedLeft(TreeNode aNode) {
+    TreeNode node;
+    TreeNode rbp_mrl_t, rbp_mrl_u;
+    rbp_mrl_t = aNode.Left();
+    rbp_mrl_t.SetColor(NodeColor::Red);
+    rbp_mrl_t = aNode.Right();
+    rbp_mrl_u = rbp_mrl_t.Left();
+    if (rbp_mrl_u.IsRed()) {
+      rbp_mrl_u = RotateRight(rbp_mrl_t);
+      aNode.SetRight(rbp_mrl_u);
+      node = RotateLeft(aNode);
+      rbp_mrl_t = aNode.Right();
+      if (rbp_mrl_t.IsRed()) {
+        rbp_mrl_t.SetColor(NodeColor::Black);
+        aNode.SetColor(NodeColor::Red);
+        rbp_mrl_t = RotateLeft(aNode);
+        node.SetLeft(rbp_mrl_t);
+      } else {
+        aNode.SetColor(NodeColor::Black);
+      }
+    } else {
+      aNode.SetColor(NodeColor::Red);
+      node = RotateLeft(aNode);
+    }
+    return node;
+  }
+
+  TreeNode MoveRedRight(TreeNode aNode) {
+    TreeNode node;
+    TreeNode rbp_mrr_t;
+    rbp_mrr_t = aNode.Left();
+    if (rbp_mrr_t.IsRed()) {
+      TreeNode rbp_mrr_u, rbp_mrr_v;
+      rbp_mrr_u = rbp_mrr_t.Right();
+      rbp_mrr_v = rbp_mrr_u.Left();
+      if (rbp_mrr_v.IsRed()) {
+        rbp_mrr_u.SetColor(aNode.Color());
+        rbp_mrr_v.SetColor(NodeColor::Black);
+        rbp_mrr_u = RotateLeft(rbp_mrr_t);
+        aNode.SetLeft(rbp_mrr_u);
+        node = RotateRight(aNode);
+        rbp_mrr_t = RotateLeft(aNode);
+        node.SetRight(rbp_mrr_t);
+      } else {
+        rbp_mrr_t.SetColor(aNode.Color());
+        rbp_mrr_u.SetColor(NodeColor::Red);
+        node = RotateRight(aNode);
+        rbp_mrr_t = RotateLeft(aNode);
+        node.SetRight(rbp_mrr_t);
+      }
+      aNode.SetColor(NodeColor::Red);
+    } else {
+      rbp_mrr_t.SetColor(NodeColor::Red);
+      rbp_mrr_t = rbp_mrr_t.Left();
+      if (rbp_mrr_t.IsRed()) {
+        rbp_mrr_t.SetColor(NodeColor::Black);
+        node = RotateRight(aNode);
+        rbp_mrr_t = RotateLeft(aNode);
+        node.SetRight(rbp_mrr_t);
+      } else {
+        node = RotateLeft(aNode);
+      }
+    }
+    return node;
+  }
+
+  // The iterator simulates recursion via an array of pointers that store the
+  // current path.  This is critical to performance, since a series of calls to
+  // rb_{next,prev}() would require time proportional to (n lg n), whereas this
+  // implementation only requires time proportional to (n).
+  //
+  // Since the iterator caches a path down the tree, any tree modification may
+  // cause the cached path to become invalid. Don't modify the tree during an
+  // iteration.
+
+  // Size the path arrays such that they are always large enough, even if a
+  // tree consumes all of memory.  Since each node must contain a minimum of
+  // two pointers, there can never be more nodes than:
+  //
+  //   1 << ((sizeof(void*)<<3) - (log2(sizeof(void*))+1))
+  //
+  // Since the depth of a tree is limited to 3*lg(#nodes), the maximum depth
+  // is:
+  //
+  //   (3 * ((sizeof(void*)<<3) - (log2(sizeof(void*))+1)))
+  //
+  // This works out to a maximum depth of 87 and 180 for 32- and 64-bit
+  // systems, respectively (approximately 348 and 1440 bytes, respectively).
+ public:
+  class Iterator {
+    TreeNode mPath[3 * ((sizeof(void*) << 3) - (LOG2(sizeof(void*)) + 1))];
+    unsigned mDepth;
+
+   public:
+    explicit Iterator(RedBlackTree<T, Trait>* aTree) : mDepth(0) {
+      // Initialize the path to contain the left spine.
+      if (aTree->mRoot) {
+        TreeNode node;
+        mPath[mDepth++] = aTree->mRoot;
+        while ((node = mPath[mDepth - 1].Left())) {
+          mPath[mDepth++] = node;
+        }
+      }
+    }
+
+    template <typename Iterator>
+    class Item {
+      Iterator* mIterator;
+      T* mItem;
+
+     public:
+      Item(Iterator* aIterator, T* aItem)
+          : mIterator(aIterator), mItem(aItem) {}
+
+      bool operator!=(const Item& aOther) const {
+        return (mIterator != aOther.mIterator) || (mItem != aOther.mItem);
+      }
+
+      T* operator*() const { return mItem; }
+
+      const Item& operator++() {
+        mItem = mIterator->Next();
+        return *this;
+      }
+    };
+
+    Item<Iterator> begin() {
+      return Item<Iterator>(this,
+                            mDepth > 0 ? mPath[mDepth - 1].Get() : nullptr);
+    }
+
+    Item<Iterator> end() { return Item<Iterator>(this, nullptr); }
+
+    T* Next() {
+      TreeNode node;
+      if ((node = mPath[mDepth - 1].Right())) {
+        // The successor is the left-most node in the right subtree.
+        mPath[mDepth++] = node;
+        while ((node = mPath[mDepth - 1].Left())) {
+          mPath[mDepth++] = node;
+        }
+      } else {
+        // The successor is above the current node.  Unwind until a
+        // left-leaning edge is removed from the path, of the path is empty.
+        for (mDepth--; mDepth > 0; mDepth--) {
+          if (mPath[mDepth - 1].Left() == mPath[mDepth]) {
+            break;
+          }
+        }
+      }
+      return mDepth > 0 ? mPath[mDepth - 1].Get() : nullptr;
+    }
+  };
+
+  Iterator iter() { return Iterator(this); }
+};
+
+#endif  // RB_H_
diff --git a/memory/build/replace_malloc.h b/memory/build/replace_malloc.h
new file mode 100644
index 0000000000..9ea3493f99
--- /dev/null
+++ b/memory/build/replace_malloc.h
@@ -0,0 +1,113 @@
+/* -*- 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/. */
+
+#ifndef replace_malloc_h
+#define replace_malloc_h
+
+// The replace_malloc facility allows an external library to replace or
+// supplement the jemalloc implementation.
+//
+// The external library may be hooked by setting one of the following
+// environment variables to the library path:
+//   - LD_PRELOAD on Linux,
+//   - DYLD_INSERT_LIBRARIES on OSX,
+//   - MOZ_REPLACE_MALLOC_LIB on Windows and Android.
+//
+// An initialization function is called before any malloc replacement
+// function, and has the following declaration:
+//
+//   void replace_init(malloc_table_t*, ReplaceMallocBridge**)
+//
+// The malloc_table_t pointer given to that function is a table containing
+// pointers to the original allocator implementation, so that replacement
+// functions can call them back if they need to. The initialization function
+// needs to alter that table to replace the function it wants to replace.
+// If it needs the original implementation, it thus needs a copy of the
+// original table.
+//
+// The ReplaceMallocBridge* pointer is an outparam that allows the
+// replace_init function to return a pointer to its ReplaceMallocBridge
+// (see replace_malloc_bridge.h).
+//
+// The functions to be implemented in the external library are of the form:
+//
+//   void* replace_malloc(size_t size)
+//   {
+//     // Fiddle with the size if necessary.
+//     // orig->malloc doesn't have to be called if the external library
+//     // provides its own allocator, but in this case it will have to
+//     // implement all functions.
+//     void *ptr = orig->malloc(size);
+//     // Do whatever you want with the ptr.
+//     return ptr;
+//   }
+//
+// where "orig" is a pointer to a copy of the table replace_init got.
+//
+// See malloc_decls.h for a list of functions that can be replaced this
+// way. The implementations are all in the form:
+//   return_type replace_name(arguments [,...])
+//
+// They don't all need to be provided.
+//
+// Building a replace-malloc library is like rocket science. It can end up
+// with things blowing up, especially when trying to use complex types, and
+// even more especially when these types come from XPCOM or other parts of the
+// Mozilla codebase.
+// It is recommended to add the following to a replace-malloc implementation's
+// moz.build:
+//   DISABLE_STL_WRAPPING = True # Avoid STL wrapping
+//
+// If your replace-malloc implementation lives under memory/replace, these
+// are taken care of by memory/replace/defs.mk.
+
+#ifdef replace_malloc_bridge_h
+#  error Do not include replace_malloc_bridge.h before replace_malloc.h. \
+  In fact, you only need the latter.
+#endif
+
+#define REPLACE_MALLOC_IMPL
+
+#include "replace_malloc_bridge.h"
+
+// Implementing a replace-malloc library is incompatible with using mozalloc.
+#define MOZ_NO_MOZALLOC 1
+
+#include "mozilla/MacroArgs.h"
+#include "mozilla/Types.h"
+
+MOZ_BEGIN_EXTERN_C
+
+// MOZ_REPLACE_WEAK is only defined in mozjemalloc.cpp. Normally including
+// this header will add function definitions.
+#ifndef MOZ_REPLACE_WEAK
+#  define MOZ_REPLACE_WEAK
+#endif
+
+// When building a replace-malloc library for static linking, we want
+// each to have a different name for their "public" functions.
+// The build system defines MOZ_REPLACE_MALLOC_PREFIX in that case.
+#ifdef MOZ_REPLACE_MALLOC_PREFIX
+#  define replace_init MOZ_CONCAT(MOZ_REPLACE_MALLOC_PREFIX, _init)
+#  define MOZ_REPLACE_PUBLIC
+#else
+#  define MOZ_REPLACE_PUBLIC MOZ_EXPORT
+#endif
+
+struct ReplaceMallocBridge;
+typedef void (*jemalloc_init_func)(malloc_table_t*,
+                                   struct ReplaceMallocBridge**);
+
+// Replace-malloc library initialization function. See top of this file
+MOZ_REPLACE_PUBLIC void replace_init(
+    malloc_table_t*, struct ReplaceMallocBridge**) MOZ_REPLACE_WEAK;
+
+// ensure this is visible and libxul/etc reference it with a weak ref
+MFBT_API void jemalloc_replace_dynamic(jemalloc_init_func);
+
+MOZ_END_EXTERN_C
+
+#endif  // replace_malloc_h
diff --git a/memory/build/replace_malloc_bridge.h b/memory/build/replace_malloc_bridge.h
new file mode 100644
index 0000000000..6a0604d896
--- /dev/null
+++ b/memory/build/replace_malloc_bridge.h
@@ -0,0 +1,212 @@
+/* -*- 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/. */
+
+#ifndef replace_malloc_bridge_h
+#define replace_malloc_bridge_h
+
+// The replace-malloc bridge allows bidirectional method calls between
+// a program and the replace-malloc library that has been loaded for it.
+// In Firefox, this is used to allow method calls between code in libxul
+// and code in the replace-malloc library, without libxul needing to link
+// against that library or vice-versa.
+//
+// Subsystems can add methods for their own need. Replace-malloc libraries
+// can decide to implement those methods or not.
+//
+// Replace-malloc libraries can provide such a bridge by implementing
+// a ReplaceMallocBridge-derived class, and a get_bridge function
+// returning an instance of that class. The default methods in
+// ReplaceMallocBridge are expected to return values that callers would
+// understand as "the bridge doesn't implement this method", so that a
+// replace-malloc library doesn't have to implement all methods.
+//
+// The ReplaceMallocBridge class contains definitions for methods for
+// all replace-malloc libraries. Each library picks the methods it wants
+// to reply to in its ReplaceMallocBridge-derived class instance.
+// All methods of ReplaceMallocBridge must be virtual. Similarly,
+// anything passed as an argument to those methods must be plain data, or
+// an instance of a class with only virtual methods.
+//
+// Binary compatibility is expected to be maintained, such that a newer
+// Firefox can be used with an old replace-malloc library, or an old
+// Firefox can be used with a newer replace-malloc library. As such, only
+// new virtual methods should be added to ReplaceMallocBridge, and
+// each change should have a corresponding bump of the mVersion value.
+// At the same time, each virtual method should have a corresponding
+// wrapper calling the virtual method on the instance from
+// ReplaceMallocBridge::Get(), giving it the version the virtual method
+// was added.
+//
+// Parts that are not relevant to the replace-malloc library end of the
+// bridge are hidden when REPLACE_MALLOC_IMPL is not defined, which is
+// the case when including replace_malloc.h.
+
+struct ReplaceMallocBridge;
+
+#include "mozilla/Types.h"
+
+MOZ_BEGIN_EXTERN_C
+
+#ifndef REPLACE_MALLOC_IMPL
+// Returns the replace-malloc bridge if there is one to be returned.
+MFBT_API ReplaceMallocBridge* get_bridge();
+#endif
+
+// Table of malloc functions.
+//   e.g. void* (*malloc)(size_t), etc.
+
+#define MALLOC_DECL(name, return_type, ...) \
+  typedef return_type(name##_impl_t)(__VA_ARGS__);
+
+#include "malloc_decls.h"
+
+#define MALLOC_DECL(name, return_type, ...) name##_impl_t* name;
+
+typedef struct {
+#include "malloc_decls.h"
+} malloc_table_t;
+
+MOZ_END_EXTERN_C
+
+#ifdef __cplusplus
+
+// Table of malloc hook functions.
+// Those functions are called with the arguments and results of malloc
+// functions after they are called.
+//   e.g. void* (*malloc_hook)(void*, size_t), etc.
+// They can either return the result they're given, or alter it before
+// returning it.
+// The hooks corresponding to functions, like free(void*), that return no
+// value, don't take an extra argument.
+// The table must at least contain a pointer for malloc_hook and free_hook
+// functions. They will be used as fallback if no pointer is given for
+// other allocation functions, like calloc_hook.
+namespace mozilla {
+namespace detail {
+template <typename R, typename... Args>
+struct AllocHookType {
+  using Type = R (*)(R, Args...);
+};
+
+template <typename... Args>
+struct AllocHookType<void, Args...> {
+  using Type = void (*)(Args...);
+};
+
+}  // namespace detail
+}  // namespace mozilla
+
+#  define MALLOC_DECL(name, return_type, ...)                                 \
+    typename mozilla::detail::AllocHookType<return_type, ##__VA_ARGS__>::Type \
+        name##_hook;
+
+typedef struct {
+#  include "malloc_decls.h"
+  // Like free_hook, but called before realloc_hook. free_hook is called
+  // instead of not given.
+  void (*realloc_hook_before)(void* aPtr);
+} malloc_hook_table_t;
+
+namespace mozilla {
+namespace dmd {
+struct DMDFuncs;
+}  // namespace dmd
+
+namespace phc {
+
+class AddrInfo;
+
+}  // namespace phc
+
+// Callbacks to register debug file handles for Poison IO interpose.
+// See Mozilla(|Un)RegisterDebugHandle in xpcom/build/PoisonIOInterposer.h
+struct DebugFdRegistry {
+  virtual void RegisterHandle(intptr_t aFd);
+
+  virtual void UnRegisterHandle(intptr_t aFd);
+};
+}  // namespace mozilla
+
+struct ReplaceMallocBridge {
+  ReplaceMallocBridge() : mVersion(6) {}
+
+  // This method was added in version 1 of the bridge.
+  virtual mozilla::dmd::DMDFuncs* GetDMDFuncs() { return nullptr; }
+
+  // Send a DebugFdRegistry instance to the replace-malloc library so that
+  // it can register/unregister file descriptors whenever needed. The
+  // instance is valid until the process dies.
+  // This method was added in version 2 of the bridge.
+  virtual void InitDebugFd(mozilla::DebugFdRegistry&) {}
+
+  // Register a list of malloc functions and hook functions to the
+  // replace-malloc library so that it can choose to dispatch to them
+  // when needed. The details of what is dispatched when is left to the
+  // replace-malloc library.
+  // Passing a nullptr for either table will unregister a previously
+  // registered table under the same name.
+  // Returns nullptr if registration failed.
+  // If registration succeeded, a table of "pure" malloc functions is
+  // returned. Those "pure" malloc functions won't call hooks.
+  // /!\ Do not rely on registration/unregistration to be instantaneous.
+  // Functions from a previously registered table may still be called for
+  // a brief time after RegisterHook returns.
+  // This method was added in version 3 of the bridge.
+  virtual const malloc_table_t* RegisterHook(
+      const char* aName, const malloc_table_t* aTable,
+      const malloc_hook_table_t* aHookTable) {
+    return nullptr;
+  }
+
+#  ifndef REPLACE_MALLOC_IMPL
+  // Returns the replace-malloc bridge if its version is at least the
+  // requested one.
+  static ReplaceMallocBridge* Get(int aMinimumVersion) {
+    static ReplaceMallocBridge* sSingleton = get_bridge();
+    return (sSingleton && sSingleton->mVersion >= aMinimumVersion) ? sSingleton
+                                                                   : nullptr;
+  }
+#  endif
+
+ protected:
+  const int mVersion;
+};
+
+#  ifndef REPLACE_MALLOC_IMPL
+// Class containing wrappers for calls to ReplaceMallocBridge methods.
+// Those wrappers need to be static methods in a class because compilers
+// complain about unused static global functions, and linkers complain
+// about multiple definitions of non-static global functions.
+// Using a separate class from ReplaceMallocBridge allows the function
+// names to be identical.
+struct ReplaceMalloc {
+  // Don't call this method from performance critical code. Use
+  // mozilla::dmd::DMDFuncs::Get() instead, it has less overhead.
+  static mozilla::dmd::DMDFuncs* GetDMDFuncs() {
+    auto singleton = ReplaceMallocBridge::Get(/* minimumVersion */ 1);
+    return singleton ? singleton->GetDMDFuncs() : nullptr;
+  }
+
+  static void InitDebugFd(mozilla::DebugFdRegistry& aRegistry) {
+    auto singleton = ReplaceMallocBridge::Get(/* minimumVersion */ 2);
+    if (singleton) {
+      singleton->InitDebugFd(aRegistry);
+    }
+  }
+
+  static const malloc_table_t* RegisterHook(
+      const char* aName, const malloc_table_t* aTable,
+      const malloc_hook_table_t* aHookTable) {
+    auto singleton = ReplaceMallocBridge::Get(/* minimumVersion */ 3);
+    return singleton ? singleton->RegisterHook(aName, aTable, aHookTable)
+                     : nullptr;
+  }
+};
+#  endif
+
+#endif  // __cplusplus
+
+#endif  // replace_malloc_bridge_h
diff --git a/memory/build/test/TestMozJemallocUtils.cpp b/memory/build/test/TestMozJemallocUtils.cpp
new file mode 100644
index 0000000000..06a1a3b5a5
--- /dev/null
+++ b/memory/build/test/TestMozJemallocUtils.cpp
@@ -0,0 +1,152 @@
+/* -*- 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/. */
+
+// This is a cppunittest, rather than a gtest, in order to assert that no
+// additional DLL needs to be linked in to use the function(s) tested herein.
+
+#include <algorithm>
+#include <iostream>
+#include <optional>
+#include <sstream>
+#include <type_traits>
+
+#include "mozmemory_utils.h"
+#include "mozilla/Likely.h"
+
+static bool TESTS_FAILED = false;
+
+// Introduce iostream output operators for std::optional, for convenience's
+// sake.
+//
+// (This is technically undefined behavior per [namespace.std], but it's
+// unlikely to have any surprising effects when confined to this compilation
+// unit.)
+namespace std {
+template <typename T>
+std::ostream& operator<<(std::ostream& o, std::optional<T> const& s) {
+  if (s) {
+    return o << "std::optional{" << s.value() << "}";
+  }
+  return o << "std::nullopt";
+}
+std::ostream& operator<<(std::ostream& o, std::nullopt_t const& s) {
+  return o << "std::nullopt";
+}
+}  // namespace std
+
+// EXPECT_EQ
+//
+// Assert that two expressions are equal. Print them, and their values, on
+// failure. (Based on the GTest macro of the same name.)
+template <typename X, typename Y, size_t Xn, size_t Yn>
+void AssertEqualImpl_(X&& x, Y&& y, const char* file, size_t line,
+                      const char (&xStr)[Xn], const char (&yStr)[Yn],
+                      const char* explanation = nullptr) {
+  if (MOZ_LIKELY(x == y)) return;
+
+  TESTS_FAILED = true;
+
+  std::stringstream sstr;
+  sstr << file << ':' << line << ": ";
+  if (explanation) sstr << explanation << "\n\t";
+  sstr << "expected " << xStr << " (" << x << ") == " << yStr << " (" << y
+       << ")\n";
+  std::cerr << sstr.str() << std::flush;
+}
+
+#define EXPECT_EQ(x, y)                                 \
+  do {                                                  \
+    AssertEqualImpl_(x, y, __FILE__, __LINE__, #x, #y); \
+  } while (0)
+
+// STATIC_ASSERT_VALUE_IS_OF_TYPE
+//
+// Assert that a value `v` is of type `t` (ignoring cv-qualification).
+#define STATIC_ASSERT_VALUE_IS_OF_TYPE(v, t) \
+  static_assert(std::is_same_v<std::remove_cv_t<decltype(v)>, t>)
+
+// MockSleep
+//
+// Mock replacement for ::Sleep that merely logs its calls.
+struct MockSleep {
+  size_t calls = 0;
+  size_t sum = 0;
+
+  void operator()(size_t val) {
+    ++calls;
+    sum += val;
+  }
+
+  bool operator==(MockSleep const& that) const {
+    return calls == that.calls && sum == that.sum;
+  }
+};
+std::ostream& operator<<(std::ostream& o, MockSleep const& s) {
+  return o << "MockSleep { count: " << s.calls << ", sum: " << s.sum << " }";
+}
+
+// MockAlloc
+//
+// Mock memory allocation mechanism. Eventually returns a value.
+template <typename T>
+struct MockAlloc {
+  size_t count;
+  T value;
+
+  std::optional<T> operator()() {
+    if (!count--) return value;
+    return std::nullopt;
+  }
+};
+
+int main() {
+  using mozilla::StallSpecs;
+
+  const StallSpecs stall = {.maxAttempts = 10, .delayMs = 50};
+
+  // semantic test: stalls as requested but still yields a value,
+  // up until it doesn't
+  for (size_t i = 0; i < 20; ++i) {
+    MockSleep sleep;
+    auto const ret =
+        stall.StallAndRetry(sleep, MockAlloc<int>{.count = i, .value = 5});
+    STATIC_ASSERT_VALUE_IS_OF_TYPE(ret, std::optional<int>);
+
+    if (i < 10) {
+      EXPECT_EQ(ret, std::optional<int>(5));
+    } else {
+      EXPECT_EQ(ret, std::nullopt);
+    }
+    size_t const expectedCalls = std::min<size_t>(i + 1, 10);
+    EXPECT_EQ(sleep,
+              (MockSleep{.calls = expectedCalls, .sum = 50 * expectedCalls}));
+  }
+
+  // syntactic test: inline capturing lambda is accepted for aOperation
+  {
+    MockSleep sleep;
+    std::optional<int> value{42};
+    auto const ret = stall.StallAndRetry(sleep, [&]() { return value; });
+
+    STATIC_ASSERT_VALUE_IS_OF_TYPE(ret, std::optional<int>);
+    EXPECT_EQ(ret, std::optional(42));
+    EXPECT_EQ(sleep, (MockSleep{.calls = 1, .sum = 50}));
+  }
+
+  // syntactic test: inline capturing lambda is accepted for aDelayFunc
+  {
+    MockSleep sleep;
+    auto const ret =
+        stall.StallAndRetry([&](size_t time) { sleep(time); },
+                            MockAlloc<int>{.count = 0, .value = 105});
+
+    STATIC_ASSERT_VALUE_IS_OF_TYPE(ret, std::optional<int>);
+    EXPECT_EQ(ret, std::optional(105));
+    EXPECT_EQ(sleep, (MockSleep{.calls = 1, .sum = 50}));
+  }
+
+  return TESTS_FAILED ? 1 : 0;
+}
diff --git a/memory/build/test/gtest/TestPHC.cpp b/memory/build/test/gtest/TestPHC.cpp
new file mode 100644
index 0000000000..58d72631cb
--- /dev/null
+++ b/memory/build/test/gtest/TestPHC.cpp
@@ -0,0 +1,415 @@
+/* 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 "gtest/gtest.h"
+
+#include "mozmemory.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/mozalloc.h"
+#include "PHC.h"
+
+using namespace mozilla;
+
+bool PHCInfoEq(phc::AddrInfo& aInfo, phc::AddrInfo::Kind aKind, void* aBaseAddr,
+               size_t aUsableSize, bool aHasAllocStack, bool aHasFreeStack) {
+  return aInfo.mKind == aKind && aInfo.mBaseAddr == aBaseAddr &&
+         aInfo.mUsableSize == aUsableSize &&
+         // Proper stack traces will have at least 3 elements.
+         (aHasAllocStack ? (aInfo.mAllocStack->mLength > 2)
+                         : (aInfo.mAllocStack.isNothing())) &&
+         (aHasFreeStack ? (aInfo.mFreeStack->mLength > 2)
+                        : (aInfo.mFreeStack.isNothing()));
+}
+
+bool JeInfoEq(jemalloc_ptr_info_t& aInfo, PtrInfoTag aTag, void* aAddr,
+              size_t aSize, arena_id_t arenaId) {
+  return aInfo.tag == aTag && aInfo.addr == aAddr && aInfo.size == aSize
+#ifdef MOZ_DEBUG
+         && aInfo.arenaId == arenaId
+#endif
+      ;
+}
+
+uint8_t* GetPHCAllocation(size_t aSize, size_t aAlignment = 1) {
+  // A crude but effective way to get a PHC allocation.
+  for (int i = 0; i < 2000000; i++) {
+    void* p = (aAlignment == 1) ? moz_xmalloc(aSize)
+                                : moz_xmemalign(aAlignment, aSize);
+    if (mozilla::phc::IsPHCAllocation(p, nullptr)) {
+      return (uint8_t*)p;
+    }
+    free(p);
+  }
+  return nullptr;
+}
+
+#if defined(XP_DARWIN) && defined(__aarch64__)
+static const size_t kPageSize = 16384;
+#else
+static const size_t kPageSize = 4096;
+#endif
+
+TEST(PHC, TestPHCAllocations)
+{
+  mozilla::phc::SetPHCState(phc::PHCState::Enabled);
+
+  // First, check that allocations of various sizes all get put at the end of
+  // their page as expected. Also, check their sizes are as expected.
+
+#define ASSERT_POS(n1, n2)                                      \
+  p = (uint8_t*)moz_xrealloc(p, (n1));                          \
+  ASSERT_EQ((reinterpret_cast<uintptr_t>(p) & (kPageSize - 1)), \
+            kPageSize - (n2));                                  \
+  ASSERT_EQ(moz_malloc_usable_size(p), (n2));
+
+  uint8_t* p = GetPHCAllocation(1);
+  if (!p) {
+    MOZ_CRASH("failed to get a PHC allocation");
+  }
+
+  // On Win64 the smallest possible allocation is 16 bytes. On other platforms
+  // it is 8 bytes.
+#if defined(XP_WIN) && defined(HAVE_64BIT_BUILD)
+  ASSERT_POS(8U, 16U);
+#else
+  ASSERT_POS(8U, 8U);
+#endif
+  for (unsigned i = 16; i <= kPageSize; i *= 2) {
+    ASSERT_POS(i, i);
+  }
+
+  free(p);
+
+#undef ASSERT_POS
+
+  // Second, do similar checking with allocations of various alignments. Also
+  // check that their sizes (which are different to allocations with normal
+  // alignment) are the same as the sizes of equivalent non-PHC allocations.
+
+#define ASSERT_ALIGN(a1, a2)                                    \
+  p = (uint8_t*)GetPHCAllocation(8, (a1));                      \
+  ASSERT_EQ((reinterpret_cast<uintptr_t>(p) & (kPageSize - 1)), \
+            kPageSize - (a2));                                  \
+  ASSERT_EQ(moz_malloc_usable_size(p), (a2));                   \
+  free(p);                                                      \
+  p = (uint8_t*)moz_xmemalign((a1), 8);                         \
+  ASSERT_EQ(moz_malloc_usable_size(p), (a2));                   \
+  free(p);
+
+  // On Win64 the smallest possible allocation is 16 bytes. On other platforms
+  // it is 8 bytes.
+#if defined(XP_WIN) && defined(HAVE_64BIT_BUILD)
+  ASSERT_ALIGN(8U, 16U);
+#else
+  ASSERT_ALIGN(8U, 8U);
+#endif
+  for (unsigned i = 16; i <= kPageSize; i *= 2) {
+    ASSERT_ALIGN(i, i);
+  }
+
+#undef ASSERT_ALIGN
+}
+
+static void TestInUseAllocation(uint8_t* aPtr, size_t aSize) {
+  phc::AddrInfo phcInfo;
+  jemalloc_ptr_info_t jeInfo;
+
+  // Test an in-use PHC allocation: first byte within it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::InUsePage, aPtr, aSize,
+                        true, false));
+  ASSERT_EQ(moz_malloc_usable_size(aPtr), aSize);
+  jemalloc_ptr_info(aPtr, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagLiveAlloc, aPtr, aSize, 0));
+
+  // Test an in-use PHC allocation: last byte within it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize - 1, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::InUsePage, aPtr, aSize,
+                        true, false));
+  ASSERT_EQ(moz_malloc_usable_size(aPtr + aSize - 1), aSize);
+  jemalloc_ptr_info(aPtr + aSize - 1, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagLiveAlloc, aPtr, aSize, 0));
+
+  // Test an in-use PHC allocation: last byte before it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr - 1, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::InUsePage, aPtr, aSize,
+                        true, false));
+  ASSERT_EQ(moz_malloc_usable_size(aPtr - 1), 0ul);
+  jemalloc_ptr_info(aPtr - 1, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test an in-use PHC allocation: first byte on its allocation page.
+  ASSERT_TRUE(
+      mozilla::phc::IsPHCAllocation(aPtr + aSize - kPageSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::InUsePage, aPtr, aSize,
+                        true, false));
+  jemalloc_ptr_info(aPtr + aSize - kPageSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test an in-use PHC allocation: first byte in the following guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, false));
+  jemalloc_ptr_info(aPtr + aSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test an in-use PHC allocation: last byte in the lower half of the
+  // following guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize + (kPageSize / 2 - 1),
+                                            &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, false));
+  jemalloc_ptr_info(aPtr + aSize + (kPageSize / 2 - 1), &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test an in-use PHC allocation: last byte in the preceding guard page.
+  ASSERT_TRUE(
+      mozilla::phc::IsPHCAllocation(aPtr + aSize - 1 - kPageSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, false));
+  jemalloc_ptr_info(aPtr + aSize - 1 - kPageSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test an in-use PHC allocation: first byte in the upper half of the
+  // preceding guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(
+      aPtr + aSize - 1 - kPageSize - (kPageSize / 2 - 1), &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, false));
+  jemalloc_ptr_info(aPtr + aSize - 1 - kPageSize - (kPageSize / 2 - 1),
+                    &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+}
+
+static void TestFreedAllocation(uint8_t* aPtr, size_t aSize) {
+  phc::AddrInfo phcInfo;
+  jemalloc_ptr_info_t jeInfo;
+
+  // Test a freed PHC allocation: first byte within it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::FreedPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagFreedAlloc, aPtr, aSize, 0));
+
+  // Test a freed PHC allocation: last byte within it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize - 1, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::FreedPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize - 1, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagFreedAlloc, aPtr, aSize, 0));
+
+  // Test a freed PHC allocation: last byte before it.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr - 1, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::FreedPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr - 1, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test a freed PHC allocation: first byte on its allocation page.
+  ASSERT_TRUE(
+      mozilla::phc::IsPHCAllocation(aPtr + aSize - kPageSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::FreedPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize - kPageSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test a freed PHC allocation: first byte in the following guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test a freed PHC allocation: last byte in the lower half of the following
+  // guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(aPtr + aSize + (kPageSize / 2 - 1),
+                                            &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize + (kPageSize / 2 - 1), &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test a freed PHC allocation: last byte in the preceding guard page.
+  ASSERT_TRUE(
+      mozilla::phc::IsPHCAllocation(aPtr + aSize - 1 - kPageSize, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize - 1 - kPageSize, &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+
+  // Test a freed PHC allocation: first byte in the upper half of the preceding
+  // guard page.
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(
+      aPtr + aSize - 1 - kPageSize - (kPageSize / 2 - 1), &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::GuardPage, aPtr, aSize,
+                        true, true));
+  jemalloc_ptr_info(aPtr + aSize - 1 - kPageSize - (kPageSize / 2 - 1),
+                    &jeInfo);
+  ASSERT_TRUE(JeInfoEq(jeInfo, TagUnknown, nullptr, 0, 0));
+}
+
+TEST(PHC, TestPHCInfo)
+{
+  mozilla::phc::SetPHCState(phc::PHCState::Enabled);
+
+  int stackVar;
+  phc::AddrInfo phcInfo;
+
+  // Test a default AddrInfo.
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::Unknown, nullptr, 0ul,
+                        false, false));
+
+  // Test some non-PHC allocation addresses.
+  ASSERT_FALSE(mozilla::phc::IsPHCAllocation(nullptr, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::Unknown, nullptr, 0,
+                        false, false));
+  ASSERT_FALSE(mozilla::phc::IsPHCAllocation(&stackVar, &phcInfo));
+  ASSERT_TRUE(PHCInfoEq(phcInfo, phc::AddrInfo::Kind::Unknown, nullptr, 0,
+                        false, false));
+
+  uint8_t* p = GetPHCAllocation(32);
+  if (!p) {
+    MOZ_CRASH("failed to get a PHC allocation");
+  }
+
+  TestInUseAllocation(p, 32);
+
+  free(p);
+
+  TestFreedAllocation(p, 32);
+
+  // There are no tests for `mKind == NeverAllocatedPage` because it's not
+  // possible to reliably get ahold of such a page.
+}
+
+TEST(PHC, TestPHCDisablingThread)
+{
+  mozilla::phc::SetPHCState(phc::PHCState::Enabled);
+
+  uint8_t* p = GetPHCAllocation(32);
+  uint8_t* q = GetPHCAllocation(32);
+  if (!p || !q) {
+    MOZ_CRASH("failed to get a PHC allocation");
+  }
+
+  ASSERT_TRUE(mozilla::phc::IsPHCEnabledOnCurrentThread());
+  mozilla::phc::DisablePHCOnCurrentThread();
+  ASSERT_FALSE(mozilla::phc::IsPHCEnabledOnCurrentThread());
+
+  // Test realloc() on a PHC allocation while PHC is disabled on the thread.
+  uint8_t* p2 = (uint8_t*)realloc(p, 128);
+  // The small realloc is fulfilled within the same page, but it does move.
+  ASSERT_TRUE(p2 == p - 96);
+  ASSERT_TRUE(mozilla::phc::IsPHCAllocation(p2, nullptr));
+  uint8_t* p3 = (uint8_t*)realloc(p2, 2 * kPageSize);
+  // The big realloc is not in-place, and the result is not a PHC allocation.
+  ASSERT_TRUE(p3 != p2);
+  ASSERT_FALSE(mozilla::phc::IsPHCAllocation(p3, nullptr));
+  free(p3);
+
+  // Test free() on a PHC allocation while PHC is disabled on the thread.
+  free(q);
+
+  // These must not be PHC allocations.
+  uint8_t* r = GetPHCAllocation(32);  // This will fail.
+  ASSERT_FALSE(!!r);
+
+  mozilla::phc::ReenablePHCOnCurrentThread();
+  ASSERT_TRUE(mozilla::phc::IsPHCEnabledOnCurrentThread());
+
+  // If it really was reenabled we should be able to get PHC allocations
+  // again.
+  uint8_t* s = GetPHCAllocation(32);  // This should succeed.
+  ASSERT_TRUE(!!s);
+  free(s);
+}
+
+TEST(PHC, TestPHCDisablingGlobal)
+{
+  mozilla::phc::SetPHCState(phc::PHCState::Enabled);
+
+  uint8_t* p1 = GetPHCAllocation(32);
+  uint8_t* p2 = GetPHCAllocation(32);
+  uint8_t* q = GetPHCAllocation(32);
+  if (!p1 || !p2 || !q) {
+    MOZ_CRASH("failed to get a PHC allocation");
+  }
+
+  mozilla::phc::SetPHCState(phc::PHCState::OnlyFree);
+
+  // Test realloc() on a PHC allocation while PHC is disabled on the thread.
+  uint8_t* p3 = (uint8_t*)realloc(p1, 128);
+  // The small realloc is evicted from PHC because in "OnlyFree" state PHC
+  // tries to reduce its memory impact.
+  ASSERT_TRUE(p3 != p1);
+  ASSERT_FALSE(mozilla::phc::IsPHCAllocation(p3, nullptr));
+  free(p3);
+  uint8_t* p4 = (uint8_t*)realloc(p2, 2 * kPageSize);
+  // The big realloc is not in-place, and the result is not a PHC
+  // allocation, regardless of PHC's state.
+  ASSERT_TRUE(p4 != p2);
+  ASSERT_FALSE(mozilla::phc::IsPHCAllocation(p4, nullptr));
+  free(p4);
+
+  // Test free() on a PHC allocation while PHC is disabled on the thread.
+  free(q);
+
+  // These must not be PHC allocations.
+  uint8_t* r = GetPHCAllocation(32);  // This will fail.
+  ASSERT_FALSE(!!r);
+
+  mozilla::phc::SetPHCState(phc::PHCState::Enabled);
+
+  // If it really was reenabled we should be able to get PHC allocations
+  // again.
+  uint8_t* s = GetPHCAllocation(32);  // This should succeed.
+  ASSERT_TRUE(!!s);
+  free(s);
+}
+
+// This test is disabled for now, see Bug 1845017 and Bug 1845655.
+// TEST(PHC, TestPHCExhaustion)
+// {
+void DisabledPHCExhaustionTest() {
+  // PHC hardcodes the amount of allocations to track.
+#if defined(XP_DARWIN) && defined(__aarch64__)
+  const unsigned NUM_ALLOCATIONS = 1024;
+#else
+  const unsigned NUM_ALLOCATIONS = 4096;
+#endif
+  uint8_t* allocations[NUM_ALLOCATIONS];
+  const unsigned REQUIRED_ALLOCATIONS = NUM_ALLOCATIONS - 50;
+
+  unsigned last_allocation;
+  for (unsigned i = 0; i < NUM_ALLOCATIONS; i++) {
+    allocations[i] = GetPHCAllocation(128);
+    last_allocation = i;
+    if (i < REQUIRED_ALLOCATIONS) {
+      // Assert that the first REQUIRED_ALLOCATIONS work.  We require only
+      // REQUIRED_ALLOCATIONS rather than NUM_ALLOCATIONS because sometimes
+      // some PHC slots are used before the test begins.
+      ASSERT_TRUE(allocations[i]);
+    } else if (!allocations[i]) {
+      // Break the loop if an allocation fails to move to the next phase.
+      last_allocation--;
+      break;
+    }
+    TestInUseAllocation(allocations[i], 128);
+  }
+
+  // We should now fail to get an allocation.
+  ASSERT_FALSE(GetPHCAllocation(128));
+
+  for (unsigned i = 0; i <= last_allocation; i++) {
+    free(allocations[i]);
+    TestFreedAllocation(allocations[i], 128);
+  }
+
+  // And now that we've released those allocations we should be able to get
+  // new allocations again.
+  uint8_t* r = GetPHCAllocation(128);
+  ASSERT_TRUE(!!r);
+  free(r);
+}
diff --git a/memory/build/test/gtest/moz.build b/memory/build/test/gtest/moz.build
new file mode 100644
index 0000000000..82ccaaf9c6
--- /dev/null
+++ b/memory/build/test/gtest/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+UNIFIED_SOURCES += [
+    "TestPHC.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "../../",
+]
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/memory/build/test/moz.build b/memory/build/test/moz.build
new file mode 100644
index 0000000000..d93cc48c65
--- /dev/null
+++ b/memory/build/test/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+# We don't link these tests against mozglue, but we do use the STL. Avoid the
+# implicit linking of `__imp_moz_xalloc` in our STL wrappers.
+DisableStlWrapping()
+
+# Important: for these tests to be run, they also need to be added
+# to testing/cppunittest.ini.
+CppUnitTests(
+    [
+        "TestMozJemallocUtils",
+    ]
+)
+# The gtests won't work in a SpiderMonkey-only build or a build without
+# jemalloc.
+if CONFIG["MOZ_PHC"]:
+    TEST_DIRS += ["gtest"]
diff --git a/memory/build/zone.c b/memory/build/zone.c
new file mode 100644
index 0000000000..7311ccf27b
--- /dev/null
+++ b/memory/build/zone.c
@@ -0,0 +1,377 @@
+/* -*- 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 "mozmemory_wrap.h"
+
+#include <stdlib.h>
+#include <mach/mach_types.h>
+#include "mozilla/Assertions.h"
+
+// Malloc implementation functions are MOZ_MEMORY_API, and jemalloc
+// specific functions MOZ_JEMALLOC_API; see mozmemory_wrap.h
+
+#define MALLOC_DECL(name, return_type, ...) \
+  MOZ_MEMORY_API return_type name##_impl(__VA_ARGS__);
+#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC
+#include "malloc_decls.h"
+
+#define MALLOC_DECL(name, return_type, ...) \
+  MOZ_JEMALLOC_API return_type name##_impl(__VA_ARGS__);
+#define MALLOC_FUNCS MALLOC_FUNCS_JEMALLOC
+#include "malloc_decls.h"
+
+// Definitions of the following structs in malloc/malloc.h might be too old
+// for the built binary to run on newer versions of OSX. So use the newest
+// possible version of those structs.
+
+typedef struct _malloc_zone_t {
+  void* reserved1;
+  void* reserved2;
+  size_t (*size)(struct _malloc_zone_t*, const void*);
+  void* (*malloc)(struct _malloc_zone_t*, size_t);
+  void* (*calloc)(struct _malloc_zone_t*, size_t, size_t);
+  void* (*valloc)(struct _malloc_zone_t*, size_t);
+  void (*free)(struct _malloc_zone_t*, void*);
+  void* (*realloc)(struct _malloc_zone_t*, void*, size_t);
+  void (*destroy)(struct _malloc_zone_t*);
+  const char* zone_name;
+  unsigned (*batch_malloc)(struct _malloc_zone_t*, size_t, void**, unsigned);
+  void (*batch_free)(struct _malloc_zone_t*, void**, unsigned);
+  struct malloc_introspection_t* introspect;
+  unsigned version;
+  void* (*memalign)(struct _malloc_zone_t*, size_t, size_t);
+  void (*free_definite_size)(struct _malloc_zone_t*, void*, size_t);
+  size_t (*pressure_relief)(struct _malloc_zone_t*, size_t);
+} malloc_zone_t;
+
+typedef struct {
+  vm_address_t address;
+  vm_size_t size;
+} vm_range_t;
+
+typedef struct malloc_statistics_t {
+  unsigned blocks_in_use;
+  size_t size_in_use;
+  size_t max_size_in_use;
+  size_t size_allocated;
+} malloc_statistics_t;
+
+typedef kern_return_t memory_reader_t(task_t, vm_address_t, vm_size_t, void**);
+
+typedef void vm_range_recorder_t(task_t, void*, unsigned type, vm_range_t*,
+                                 unsigned);
+
+typedef struct malloc_introspection_t {
+  kern_return_t (*enumerator)(task_t, void*, unsigned, vm_address_t,
+                              memory_reader_t, vm_range_recorder_t);
+  size_t (*good_size)(malloc_zone_t*, size_t);
+  boolean_t (*check)(malloc_zone_t*);
+  void (*print)(malloc_zone_t*, boolean_t);
+  void (*log)(malloc_zone_t*, void*);
+  void (*force_lock)(malloc_zone_t*);
+  void (*force_unlock)(malloc_zone_t*);
+  void (*statistics)(malloc_zone_t*, malloc_statistics_t*);
+  boolean_t (*zone_locked)(malloc_zone_t*);
+  boolean_t (*enable_discharge_checking)(malloc_zone_t*);
+  boolean_t (*disable_discharge_checking)(malloc_zone_t*);
+  void (*discharge)(malloc_zone_t*, void*);
+#ifdef __BLOCKS__
+  void (*enumerate_discharged_pointers)(malloc_zone_t*, void (^)(void*, void*));
+#else
+  void* enumerate_unavailable_without_blocks;
+#endif
+  void (*reinit_lock)(malloc_zone_t*);
+} malloc_introspection_t;
+
+extern kern_return_t malloc_get_all_zones(task_t, memory_reader_t,
+                                          vm_address_t**, unsigned*);
+
+extern malloc_zone_t* malloc_default_zone(void);
+
+extern void malloc_zone_register(malloc_zone_t* zone);
+
+extern void malloc_zone_unregister(malloc_zone_t* zone);
+
+extern malloc_zone_t* malloc_default_purgeable_zone(void);
+
+extern malloc_zone_t* malloc_zone_from_ptr(const void* ptr);
+
+extern void malloc_zone_free(malloc_zone_t* zone, void* ptr);
+
+extern void* malloc_zone_realloc(malloc_zone_t* zone, void* ptr, size_t size);
+
+// The following is a OSX zone allocator implementation.
+// /!\ WARNING. It assumes the underlying malloc implementation's
+// malloc_usable_size returns 0 when the given pointer is not owned by
+// the allocator. Sadly, OSX does call zone_size with pointers not
+// owned by the allocator.
+
+static size_t zone_size(malloc_zone_t* zone, const void* ptr) {
+  return malloc_usable_size_impl(ptr);
+}
+
+static void* zone_malloc(malloc_zone_t* zone, size_t size) {
+  return malloc_impl(size);
+}
+
+static void* zone_calloc(malloc_zone_t* zone, size_t num, size_t size) {
+  return calloc_impl(num, size);
+}
+
+static void* zone_realloc(malloc_zone_t* zone, void* ptr, size_t size) {
+  if (malloc_usable_size_impl(ptr)) return realloc_impl(ptr, size);
+
+  // Sometimes, system libraries call malloc_zone_* functions with the wrong
+  // zone (e.g. CoreFoundation does). In that case, we need to find the real
+  // one. We can't call libSystem's realloc directly because we're exporting
+  // realloc from libmozglue and we'd pick that one, so we manually find the
+  // right zone and realloc with it.
+  malloc_zone_t* real_zone = malloc_zone_from_ptr(ptr);
+  // The system allocator crashes voluntarily by default when a pointer can't
+  // be traced back to a zone. Do the same.
+  MOZ_RELEASE_ASSERT(real_zone);
+  MOZ_RELEASE_ASSERT(real_zone != zone);
+  return malloc_zone_realloc(real_zone, ptr, size);
+}
+
+static void other_zone_free(malloc_zone_t* original_zone, void* ptr) {
+  // Sometimes, system libraries call malloc_zone_* functions with the wrong
+  // zone (e.g. CoreFoundation does). In that case, we need to find the real
+  // one. We can't call libSystem's free directly because we're exporting
+  // free from libmozglue and we'd pick that one, so we manually find the
+  // right zone and free with it.
+  if (!ptr) {
+    return;
+  }
+  malloc_zone_t* zone = malloc_zone_from_ptr(ptr);
+  // The system allocator crashes voluntarily by default when a pointer can't
+  // be traced back to a zone. Do the same.
+  MOZ_RELEASE_ASSERT(zone);
+  MOZ_RELEASE_ASSERT(zone != original_zone);
+  return malloc_zone_free(zone, ptr);
+}
+
+static void zone_free(malloc_zone_t* zone, void* ptr) {
+  if (malloc_usable_size_impl(ptr)) {
+    free_impl(ptr);
+    return;
+  }
+  other_zone_free(zone, ptr);
+}
+
+static void zone_free_definite_size(malloc_zone_t* zone, void* ptr,
+                                    size_t size) {
+  size_t current_size = malloc_usable_size_impl(ptr);
+  if (current_size) {
+    MOZ_ASSERT(current_size == size);
+    free_impl(ptr);
+    return;
+  }
+  other_zone_free(zone, ptr);
+}
+
+static void* zone_memalign(malloc_zone_t* zone, size_t alignment, size_t size) {
+  void* ptr;
+  if (posix_memalign_impl(&ptr, alignment, size) == 0) return ptr;
+  return NULL;
+}
+
+static void* zone_valloc(malloc_zone_t* zone, size_t size) {
+  return valloc_impl(size);
+}
+
+static void zone_destroy(malloc_zone_t* zone) {
+  // This function should never be called.
+  MOZ_CRASH();
+}
+
+static unsigned zone_batch_malloc(malloc_zone_t* zone, size_t size,
+                                  void** results, unsigned num_requested) {
+  unsigned i;
+
+  for (i = 0; i < num_requested; i++) {
+    results[i] = malloc_impl(size);
+    if (!results[i]) break;
+  }
+
+  return i;
+}
+
+static void zone_batch_free(malloc_zone_t* zone, void** to_be_freed,
+                            unsigned num_to_be_freed) {
+  unsigned i;
+
+  for (i = 0; i < num_to_be_freed; i++) {
+    zone_free(zone, to_be_freed[i]);
+    to_be_freed[i] = NULL;
+  }
+}
+
+static size_t zone_pressure_relief(malloc_zone_t* zone, size_t goal) {
+  return 0;
+}
+
+static size_t zone_good_size(malloc_zone_t* zone, size_t size) {
+  return malloc_good_size_impl(size);
+}
+
+static kern_return_t zone_enumerator(task_t task, void* data,
+                                     unsigned type_mask,
+                                     vm_address_t zone_address,
+                                     memory_reader_t reader,
+                                     vm_range_recorder_t recorder) {
+  return KERN_SUCCESS;
+}
+
+static boolean_t zone_check(malloc_zone_t* zone) { return true; }
+
+static void zone_print(malloc_zone_t* zone, boolean_t verbose) {}
+
+static void zone_log(malloc_zone_t* zone, void* address) {}
+
+extern void _malloc_prefork(void);
+extern void _malloc_postfork_child(void);
+
+static void zone_force_lock(malloc_zone_t* zone) {
+  // /!\ This calls into mozjemalloc. It works because we're linked in the
+  // same library.
+  _malloc_prefork();
+}
+
+static void zone_force_unlock(malloc_zone_t* zone) {
+  // /!\ This calls into mozjemalloc. It works because we're linked in the
+  // same library.
+  _malloc_postfork_child();
+}
+
+static void zone_statistics(malloc_zone_t* zone, malloc_statistics_t* stats) {
+  // We make no effort to actually fill the values
+  stats->blocks_in_use = 0;
+  stats->size_in_use = 0;
+  stats->max_size_in_use = 0;
+  stats->size_allocated = 0;
+}
+
+static boolean_t zone_locked(malloc_zone_t* zone) {
+  // Pretend no lock is being held
+  return false;
+}
+
+static void zone_reinit_lock(malloc_zone_t* zone) {
+  // As of OSX 10.12, this function is only used when force_unlock would
+  // be used if the zone version were < 9. So just use force_unlock.
+  zone_force_unlock(zone);
+}
+
+static malloc_zone_t zone;
+static struct malloc_introspection_t zone_introspect;
+
+static malloc_zone_t* get_default_zone() {
+  malloc_zone_t** zones = NULL;
+  unsigned int num_zones = 0;
+
+  // On OSX 10.12, malloc_default_zone returns a special zone that is not
+  // present in the list of registered zones. That zone uses a "lite zone"
+  // if one is present (apparently enabled when malloc stack logging is
+  // enabled), or the first registered zone otherwise. In practice this
+  // means unless malloc stack logging is enabled, the first registered
+  // zone is the default.
+  // So get the list of zones to get the first one, instead of relying on
+  // malloc_default_zone.
+  if (KERN_SUCCESS !=
+      malloc_get_all_zones(0, NULL, (vm_address_t**)&zones, &num_zones)) {
+    // Reset the value in case the failure happened after it was set.
+    num_zones = 0;
+  }
+  if (num_zones) {
+    return zones[0];
+  }
+  return malloc_default_zone();
+}
+
+__attribute__((constructor)) static void register_zone(void) {
+  malloc_zone_t* default_zone = get_default_zone();
+
+  zone.size = zone_size;
+  zone.malloc = zone_malloc;
+  zone.calloc = zone_calloc;
+  zone.valloc = zone_valloc;
+  zone.free = zone_free;
+  zone.realloc = zone_realloc;
+  zone.destroy = zone_destroy;
+#ifdef MOZ_REPLACE_MALLOC
+  zone.zone_name = "replace_malloc_zone";
+#else
+  zone.zone_name = "jemalloc_zone";
+#endif
+  zone.batch_malloc = zone_batch_malloc;
+  zone.batch_free = zone_batch_free;
+  zone.introspect = &zone_introspect;
+  zone.version = 9;
+  zone.memalign = zone_memalign;
+  zone.free_definite_size = zone_free_definite_size;
+  zone.pressure_relief = zone_pressure_relief;
+  zone_introspect.enumerator = zone_enumerator;
+  zone_introspect.good_size = zone_good_size;
+  zone_introspect.check = zone_check;
+  zone_introspect.print = zone_print;
+  zone_introspect.log = zone_log;
+  zone_introspect.force_lock = zone_force_lock;
+  zone_introspect.force_unlock = zone_force_unlock;
+  zone_introspect.statistics = zone_statistics;
+  zone_introspect.zone_locked = zone_locked;
+  zone_introspect.enable_discharge_checking = NULL;
+  zone_introspect.disable_discharge_checking = NULL;
+  zone_introspect.discharge = NULL;
+#ifdef __BLOCKS__
+  zone_introspect.enumerate_discharged_pointers = NULL;
+#else
+  zone_introspect.enumerate_unavailable_without_blocks = NULL;
+#endif
+  zone_introspect.reinit_lock = zone_reinit_lock;
+
+  // The default purgeable zone is created lazily by OSX's libc.  It uses
+  // the default zone when it is created for "small" allocations
+  // (< 15 KiB), but assumes the default zone is a scalable_zone.  This
+  // obviously fails when the default zone is the jemalloc zone, so
+  // malloc_default_purgeable_zone is called beforehand so that the
+  // default purgeable zone is created when the default zone is still
+  // a scalable_zone.
+  malloc_zone_t* purgeable_zone = malloc_default_purgeable_zone();
+
+  // There is a problem related to the above with the system nano zone, which
+  // is hard to work around from here, and that is instead worked around by
+  // disabling the nano zone through an environment variable
+  // (MallocNanoZone=0). In Firefox, we do that through
+  // browser/app/macbuild/Contents/Info.plist.in.
+
+  // Register the custom zone.  At this point it won't be the default.
+  malloc_zone_register(&zone);
+
+  do {
+    // Unregister and reregister the default zone.  On OSX >= 10.6,
+    // unregistering takes the last registered zone and places it at the
+    // location of the specified zone.  Unregistering the default zone thus
+    // makes the last registered one the default.  On OSX < 10.6,
+    // unregistering shifts all registered zones.  The first registered zone
+    // then becomes the default.
+    malloc_zone_unregister(default_zone);
+    malloc_zone_register(default_zone);
+
+    // On OSX 10.6, having the default purgeable zone appear before the default
+    // zone makes some things crash because it thinks it owns the default
+    // zone allocated pointers. We thus unregister/re-register it in order to
+    // ensure it's always after the default zone. On OSX < 10.6, as
+    // unregistering shifts registered zones, this simply removes the purgeable
+    // zone from the list and adds it back at the end, after the default zone.
+    // On OSX >= 10.6, unregistering replaces the purgeable zone with the last
+    // registered zone above, i.e the default zone. Registering it again then
+    // puts it at the end, obviously after the default zone.
+    malloc_zone_unregister(purgeable_zone);
+    malloc_zone_register(purgeable_zone);
+    default_zone = get_default_zone();
+  } while (default_zone != &zone);
+}