Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

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

1 files changed, 1063 insertions, 0 deletions

diff --git a/mozglue/misc/StackWalk.cpp b/mozglue/misc/StackWalk.cpp
new file mode 100644
index 0000000000..307715b170
--- /dev/null
+++ b/mozglue/misc/StackWalk.cpp
@@ -0,0 +1,1063 @@
+/* -*- 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/. */
+
+/* API for getting a stack trace of the C/C++ stack on the current thread */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/StackWalk.h"
+#ifdef XP_WIN
+#  include "mozilla/StackWalkThread.h"
+#  include <io.h>
+#else
+#  include <unistd.h>
+#endif
+#include "mozilla/Sprintf.h"
+
+#include <string.h>
+
+#if defined(ANDROID) && defined(MOZ_LINKER)
+#  include "Linker.h"
+#  include <android/log.h>
+#endif
+
+using namespace mozilla;
+
+// for _Unwind_Backtrace from libcxxrt or libunwind
+// cxxabi.h from libcxxrt implicitly includes unwind.h first
+#if defined(HAVE__UNWIND_BACKTRACE) && !defined(_GNU_SOURCE)
+#  define _GNU_SOURCE
+#endif
+
+#if defined(HAVE_DLOPEN) || defined(XP_DARWIN)
+#  include <dlfcn.h>
+#endif
+
+#if (defined(XP_DARWIN) && \
+     (defined(__i386) || defined(__ppc__) || defined(HAVE__UNWIND_BACKTRACE)))
+#  define MOZ_STACKWALK_SUPPORTS_MACOSX 1
+#else
+#  define MOZ_STACKWALK_SUPPORTS_MACOSX 0
+#endif
+
+#if (defined(linux) &&                                            \
+     ((defined(__GNUC__) && (defined(__i386) || defined(PPC))) || \
+      defined(HAVE__UNWIND_BACKTRACE)))
+#  define MOZ_STACKWALK_SUPPORTS_LINUX 1
+#else
+#  define MOZ_STACKWALK_SUPPORTS_LINUX 0
+#endif
+
+#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1)
+#  define HAVE___LIBC_STACK_END 1
+#else
+#  define HAVE___LIBC_STACK_END 0
+#endif
+
+#if HAVE___LIBC_STACK_END
+extern MOZ_EXPORT void* __libc_stack_end;  // from ld-linux.so
+#endif
+
+#ifdef ANDROID
+#  include <algorithm>
+#  include <unistd.h>
+#  include <pthread.h>
+#endif
+
+class FrameSkipper {
+ public:
+  constexpr FrameSkipper() : mPc(0) {}
+  bool ShouldSkipPC(void* aPC) {
+    // Skip frames until we encounter the one we were initialized with,
+    // and then never skip again.
+    if (mPc != 0) {
+      if (mPc != uintptr_t(aPC)) {
+        return true;
+      }
+      mPc = 0;
+    }
+    return false;
+  }
+  explicit FrameSkipper(const void* aPc) : mPc(uintptr_t(aPc)) {}
+
+ private:
+  uintptr_t mPc;
+};
+
+#ifdef XP_WIN
+
+#  include <windows.h>
+#  include <process.h>
+#  include <stdio.h>
+#  include <malloc.h>
+#  include "mozilla/ArrayUtils.h"
+#  include "mozilla/Atomics.h"
+#  include "mozilla/StackWalk_windows.h"
+#  include "mozilla/WindowsVersion.h"
+
+#  include <imagehlp.h>
+// We need a way to know if we are building for WXP (or later), as if we are, we
+// need to use the newer 64-bit APIs. API_VERSION_NUMBER seems to fit the bill.
+// A value of 9 indicates we want to use the new APIs.
+#  if API_VERSION_NUMBER < 9
+#    error Too old imagehlp.h
+#  endif
+
+CRITICAL_SECTION gDbgHelpCS;
+
+#  if defined(_M_AMD64) || defined(_M_ARM64)
+// Because various Win64 APIs acquire function-table locks, we need a way of
+// preventing stack walking while those APIs are being called. Otherwise, the
+// stack walker may suspend a thread holding such a lock, and deadlock when the
+// stack unwind code attempts to wait for that lock.
+//
+// We're using an atomic counter rather than a critical section because we
+// don't require mutual exclusion with the stack walker. If the stack walker
+// determines that it's safe to start unwinding the suspended thread (i.e.
+// there are no suppressions when the unwind begins), then it's safe to
+// continue unwinding that thread even if other threads request suppressions
+// in the meantime, because we can't deadlock with those other threads.
+//
+// XXX: This global variable is a larger-than-necessary hammer. A more scoped
+// solution would be to maintain a counter per thread, but then it would be
+// more difficult for WalkStackMain64 to read the suspended thread's counter.
+static Atomic<size_t> sStackWalkSuppressions;
+
+void SuppressStackWalking() { ++sStackWalkSuppressions; }
+
+void DesuppressStackWalking() { --sStackWalkSuppressions; }
+
+MFBT_API
+AutoSuppressStackWalking::AutoSuppressStackWalking() { SuppressStackWalking(); }
+
+MFBT_API
+AutoSuppressStackWalking::~AutoSuppressStackWalking() {
+  DesuppressStackWalking();
+}
+
+static uint8_t* sJitCodeRegionStart;
+static size_t sJitCodeRegionSize;
+uint8_t* sMsMpegJitCodeRegionStart;
+size_t sMsMpegJitCodeRegionSize;
+
+MFBT_API void RegisterJitCodeRegion(uint8_t* aStart, size_t aSize) {
+  // Currently we can only handle one JIT code region at a time
+  MOZ_RELEASE_ASSERT(!sJitCodeRegionStart);
+
+  sJitCodeRegionStart = aStart;
+  sJitCodeRegionSize = aSize;
+}
+
+MFBT_API void UnregisterJitCodeRegion(uint8_t* aStart, size_t aSize) {
+  // Currently we can only handle one JIT code region at a time
+  MOZ_RELEASE_ASSERT(sJitCodeRegionStart && sJitCodeRegionStart == aStart &&
+                     sJitCodeRegionSize == aSize);
+
+  sJitCodeRegionStart = nullptr;
+  sJitCodeRegionSize = 0;
+}
+
+#  endif  // _M_AMD64 || _M_ARM64
+
+// Routine to print an error message to standard error.
+static void PrintError(const char* aPrefix) {
+  LPSTR lpMsgBuf;
+  DWORD lastErr = GetLastError();
+  FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+                     FORMAT_MESSAGE_IGNORE_INSERTS,
+                 nullptr, lastErr,
+                 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),  // Default language
+                 (LPSTR)&lpMsgBuf, 0, nullptr);
+  fprintf(stderr, "### ERROR: %s: %s", aPrefix,
+          lpMsgBuf ? lpMsgBuf : "(null)\n");
+  fflush(stderr);
+  LocalFree(lpMsgBuf);
+}
+
+static void InitializeDbgHelpCriticalSection() {
+  static bool initialized = false;
+  if (initialized) {
+    return;
+  }
+  ::InitializeCriticalSection(&gDbgHelpCS);
+  initialized = true;
+}
+
+// Wrapper around a reference to a CONTEXT, to simplify access to main
+// platform-specific execution registers.
+// It also avoids using CONTEXT* nullable pointers.
+class CONTEXTGenericAccessors {
+ public:
+  explicit CONTEXTGenericAccessors(CONTEXT& aCONTEXT) : mCONTEXT(aCONTEXT) {}
+
+  CONTEXT* CONTEXTPtr() { return &mCONTEXT; }
+
+  inline auto& PC() {
+#  if defined(_M_AMD64)
+    return mCONTEXT.Rip;
+#  elif defined(_M_ARM64)
+    return mCONTEXT.Pc;
+#  elif defined(_M_IX86)
+    return mCONTEXT.Eip;
+#  else
+#    error "unknown platform"
+#  endif
+  }
+
+  inline auto& SP() {
+#  if defined(_M_AMD64)
+    return mCONTEXT.Rsp;
+#  elif defined(_M_ARM64)
+    return mCONTEXT.Sp;
+#  elif defined(_M_IX86)
+    return mCONTEXT.Esp;
+#  else
+#    error "unknown platform"
+#  endif
+  }
+
+  inline auto& BP() {
+#  if defined(_M_AMD64)
+    return mCONTEXT.Rbp;
+#  elif defined(_M_ARM64)
+    return mCONTEXT.Fp;
+#  elif defined(_M_IX86)
+    return mCONTEXT.Ebp;
+#  else
+#    error "unknown platform"
+#  endif
+  }
+
+ private:
+  CONTEXT& mCONTEXT;
+};
+
+/**
+ * Walk the stack, translating PC's found into strings and recording the
+ * chain in aBuffer. For this to work properly, the DLLs must be rebased
+ * so that the address in the file agrees with the address in memory.
+ * Otherwise StackWalk will return FALSE when it hits a frame in a DLL
+ * whose in memory address doesn't match its in-file address.
+ */
+
+static void DoMozStackWalkThread(MozWalkStackCallback aCallback,
+                                 const void* aFirstFramePC, uint32_t aMaxFrames,
+                                 void* aClosure, HANDLE aThread,
+                                 CONTEXT* aContext) {
+  InitializeDbgHelpCriticalSection();
+
+  HANDLE targetThread = aThread;
+  bool walkCallingThread;
+  if (!targetThread) {
+    targetThread = ::GetCurrentThread();
+    walkCallingThread = true;
+  } else {
+    DWORD targetThreadId = ::GetThreadId(targetThread);
+    DWORD currentThreadId = ::GetCurrentThreadId();
+    walkCallingThread = (targetThreadId == currentThreadId);
+  }
+
+  // If not already provided, get a context for the specified thread.
+  CONTEXT context_buf;
+  if (!aContext) {
+    memset(&context_buf, 0, sizeof(CONTEXT));
+    context_buf.ContextFlags = CONTEXT_FULL;
+    if (walkCallingThread) {
+      ::RtlCaptureContext(&context_buf);
+    } else if (!GetThreadContext(targetThread, &context_buf)) {
+      return;
+    }
+  }
+  CONTEXTGenericAccessors context{aContext ? *aContext : context_buf};
+
+#  if defined(_M_IX86)
+  // Setup initial stack frame to walk from.
+  STACKFRAME64 frame64;
+  memset(&frame64, 0, sizeof(frame64));
+  frame64.AddrPC.Offset = context.PC();
+  frame64.AddrStack.Offset = context.SP();
+  frame64.AddrFrame.Offset = context.BP();
+  frame64.AddrPC.Mode = AddrModeFlat;
+  frame64.AddrStack.Mode = AddrModeFlat;
+  frame64.AddrFrame.Mode = AddrModeFlat;
+  frame64.AddrReturn.Mode = AddrModeFlat;
+#  endif
+
+#  if defined(_M_AMD64) || defined(_M_ARM64)
+  // If there are any active suppressions, then at least one thread (we don't
+  // know which) is holding a lock that can deadlock RtlVirtualUnwind. Since
+  // that thread may be the one that we're trying to unwind, we can't proceed.
+  //
+  // But if there are no suppressions, then our target thread can't be holding
+  // a lock, and it's safe to proceed. By virtue of being suspended, the target
+  // thread can't acquire any new locks during the unwind process, so we only
+  // need to do this check once. After that, sStackWalkSuppressions can be
+  // changed by other threads while we're unwinding, and that's fine because
+  // we can't deadlock with those threads.
+  if (sStackWalkSuppressions) {
+    return;
+  }
+#  endif
+
+#  if defined(_M_AMD64) || defined(_M_ARM64)
+  bool firstFrame = true;
+#  endif
+
+  FrameSkipper skipper(aFirstFramePC);
+
+  uint32_t frames = 0;
+
+  // Now walk the stack.
+  while (true) {
+    DWORD64 addr;
+    DWORD64 spaddr;
+
+#  if defined(_M_IX86)
+    // 32-bit frame unwinding.
+    // Debug routines are not threadsafe, so grab the lock.
+    EnterCriticalSection(&gDbgHelpCS);
+    BOOL ok = StackWalk64(
+#    if defined _M_IX86
+        IMAGE_FILE_MACHINE_I386,
+#    endif
+        ::GetCurrentProcess(), targetThread, &frame64, context.CONTEXTPtr(),
+        nullptr,
+        SymFunctionTableAccess64,  // function table access routine
+        SymGetModuleBase64,        // module base routine
+        0);
+    LeaveCriticalSection(&gDbgHelpCS);
+
+    if (ok) {
+      addr = frame64.AddrPC.Offset;
+      spaddr = frame64.AddrStack.Offset;
+    } else {
+      addr = 0;
+      spaddr = 0;
+      if (walkCallingThread) {
+        PrintError("WalkStack64");
+      }
+    }
+
+    if (!ok) {
+      break;
+    }
+
+#  elif defined(_M_AMD64) || defined(_M_ARM64)
+
+    auto currentInstr = context.PC();
+
+    // If we reach a frame in JIT code, we don't have enough information to
+    // unwind, so we have to give up.
+    if (sJitCodeRegionStart && (uint8_t*)currentInstr >= sJitCodeRegionStart &&
+        (uint8_t*)currentInstr < sJitCodeRegionStart + sJitCodeRegionSize) {
+      break;
+    }
+
+    // We must also avoid msmpeg2vdec.dll's JIT region: they don't generate
+    // unwind data, so their JIT unwind callback just throws up its hands and
+    // terminates the process.
+    if (sMsMpegJitCodeRegionStart &&
+        (uint8_t*)currentInstr >= sMsMpegJitCodeRegionStart &&
+        (uint8_t*)currentInstr <
+            sMsMpegJitCodeRegionStart + sMsMpegJitCodeRegionSize) {
+      break;
+    }
+
+    // 64-bit frame unwinding.
+    // Try to look up unwind metadata for the current function.
+    ULONG64 imageBase;
+    PRUNTIME_FUNCTION runtimeFunction =
+        RtlLookupFunctionEntry(currentInstr, &imageBase, NULL);
+
+    if (runtimeFunction) {
+      PVOID dummyHandlerData;
+      ULONG64 dummyEstablisherFrame;
+      RtlVirtualUnwind(UNW_FLAG_NHANDLER, imageBase, currentInstr,
+                       runtimeFunction, context.CONTEXTPtr(), &dummyHandlerData,
+                       &dummyEstablisherFrame, nullptr);
+    } else if (firstFrame) {
+      // Leaf functions can be unwound by hand.
+      context.PC() = *reinterpret_cast<DWORD64*>(context.SP());
+      context.SP() += sizeof(void*);
+    } else {
+      // Something went wrong.
+      break;
+    }
+
+    addr = context.PC();
+    spaddr = context.SP();
+    firstFrame = false;
+#  else
+#    error "unknown platform"
+#  endif
+
+    if (addr == 0) {
+      break;
+    }
+
+    if (skipper.ShouldSkipPC((void*)addr)) {
+      continue;
+    }
+
+    aCallback(++frames, (void*)addr, (void*)spaddr, aClosure);
+
+    if (aMaxFrames != 0 && frames == aMaxFrames) {
+      break;
+    }
+
+#  if defined(_M_IX86)
+    if (frame64.AddrReturn.Offset == 0) {
+      break;
+    }
+#  endif
+  }
+}
+
+MFBT_API void MozStackWalkThread(MozWalkStackCallback aCallback,
+                                 uint32_t aMaxFrames, void* aClosure,
+                                 HANDLE aThread, CONTEXT* aContext) {
+  // We don't pass a aFirstFramePC because we walk the stack for another
+  // thread.
+  DoMozStackWalkThread(aCallback, nullptr, aMaxFrames, aClosure, aThread,
+                       aContext);
+}
+
+MFBT_API void MozStackWalk(MozWalkStackCallback aCallback,
+                           const void* aFirstFramePC, uint32_t aMaxFrames,
+                           void* aClosure) {
+  DoMozStackWalkThread(aCallback, aFirstFramePC ? aFirstFramePC : CallerPC(),
+                       aMaxFrames, aClosure, nullptr, nullptr);
+}
+
+static BOOL CALLBACK callbackEspecial64(PCSTR aModuleName, DWORD64 aModuleBase,
+                                        ULONG aModuleSize, PVOID aUserContext) {
+  BOOL retval = TRUE;
+  DWORD64 addr = *(DWORD64*)aUserContext;
+
+  /*
+   * You'll want to control this if we are running on an
+   *  architecture where the addresses go the other direction.
+   * Not sure this is even a realistic consideration.
+   */
+  const BOOL addressIncreases = TRUE;
+
+  /*
+   * If it falls in side the known range, load the symbols.
+   */
+  if (addressIncreases
+          ? (addr >= aModuleBase && addr <= (aModuleBase + aModuleSize))
+          : (addr <= aModuleBase && addr >= (aModuleBase - aModuleSize))) {
+    retval = !!SymLoadModule64(GetCurrentProcess(), nullptr, (PSTR)aModuleName,
+                               nullptr, aModuleBase, aModuleSize);
+    if (!retval) {
+      PrintError("SymLoadModule64");
+    }
+  }
+
+  return retval;
+}
+
+/*
+ * SymGetModuleInfoEspecial
+ *
+ * Attempt to determine the module information.
+ * Bug 112196 says this DLL may not have been loaded at the time
+ *  SymInitialize was called, and thus the module information
+ *  and symbol information is not available.
+ * This code rectifies that problem.
+ */
+
+// New members were added to IMAGEHLP_MODULE64 (that show up in the
+// Platform SDK that ships with VC8, but not the Platform SDK that ships
+// with VC7.1, i.e., between DbgHelp 6.0 and 6.1), but we don't need to
+// use them, and it's useful to be able to function correctly with the
+// older library.  (Stock Windows XP SP2 seems to ship with dbghelp.dll
+// version 5.1.)  Since Platform SDK version need not correspond to
+// compiler version, and the version number in debughlp.h was NOT bumped
+// when these changes were made, ifdef based on a constant that was
+// added between these versions.
+#  ifdef SSRVOPT_SETCONTEXT
+#    define NS_IMAGEHLP_MODULE64_SIZE                                        \
+      (((offsetof(IMAGEHLP_MODULE64, LoadedPdbName) + sizeof(DWORD64) - 1) / \
+        sizeof(DWORD64)) *                                                   \
+       sizeof(DWORD64))
+#  else
+#    define NS_IMAGEHLP_MODULE64_SIZE sizeof(IMAGEHLP_MODULE64)
+#  endif
+
+BOOL SymGetModuleInfoEspecial64(HANDLE aProcess, DWORD64 aAddr,
+                                PIMAGEHLP_MODULE64 aModuleInfo,
+                                PIMAGEHLP_LINE64 aLineInfo) {
+  BOOL retval = FALSE;
+
+  /*
+   * Init the vars if we have em.
+   */
+  aModuleInfo->SizeOfStruct = NS_IMAGEHLP_MODULE64_SIZE;
+  if (aLineInfo) {
+    aLineInfo->SizeOfStruct = sizeof(IMAGEHLP_LINE64);
+  }
+
+  /*
+   * Give it a go.
+   * It may already be loaded.
+   */
+  retval = SymGetModuleInfo64(aProcess, aAddr, aModuleInfo);
+  if (retval == FALSE) {
+    /*
+     * Not loaded, here's the magic.
+     * Go through all the modules.
+     */
+    // Need to cast to PENUMLOADED_MODULES_CALLBACK64 because the
+    // constness of the first parameter of
+    // PENUMLOADED_MODULES_CALLBACK64 varies over SDK versions (from
+    // non-const to const over time).  See bug 391848 and bug
+    // 415426.
+    BOOL enumRes = EnumerateLoadedModules64(
+        aProcess, (PENUMLOADED_MODULES_CALLBACK64)callbackEspecial64,
+        (PVOID)&aAddr);
+    if (enumRes != FALSE) {
+      /*
+       * One final go.
+       * If it fails, then well, we have other problems.
+       */
+      retval = SymGetModuleInfo64(aProcess, aAddr, aModuleInfo);
+    }
+  }
+
+  /*
+   * If we got module info, we may attempt line info as well.
+   * We will not report failure if this does not work.
+   */
+  if (retval != FALSE && aLineInfo) {
+    DWORD displacement = 0;
+    BOOL lineRes = FALSE;
+    lineRes = SymGetLineFromAddr64(aProcess, aAddr, &displacement, aLineInfo);
+    if (!lineRes) {
+      // Clear out aLineInfo to indicate that it's not valid
+      memset(aLineInfo, 0, sizeof(*aLineInfo));
+    }
+  }
+
+  return retval;
+}
+
+static bool EnsureSymInitialized() {
+  static bool gInitialized = false;
+  bool retStat;
+
+  if (gInitialized) {
+    return gInitialized;
+  }
+
+  InitializeDbgHelpCriticalSection();
+
+  SymSetOptions(SYMOPT_LOAD_LINES | SYMOPT_UNDNAME);
+  retStat = SymInitialize(GetCurrentProcess(), nullptr, TRUE);
+  if (!retStat) {
+    PrintError("SymInitialize");
+  }
+
+  gInitialized = retStat;
+  /* XXX At some point we need to arrange to call SymCleanup */
+
+  return retStat;
+}
+
+MFBT_API bool MozDescribeCodeAddress(void* aPC,
+                                     MozCodeAddressDetails* aDetails) {
+  aDetails->library[0] = '\0';
+  aDetails->loffset = 0;
+  aDetails->filename[0] = '\0';
+  aDetails->lineno = 0;
+  aDetails->function[0] = '\0';
+  aDetails->foffset = 0;
+
+  if (!EnsureSymInitialized()) {
+    return false;
+  }
+
+  HANDLE myProcess = ::GetCurrentProcess();
+  BOOL ok;
+
+  // debug routines are not threadsafe, so grab the lock.
+  EnterCriticalSection(&gDbgHelpCS);
+
+  //
+  // Attempt to load module info before we attempt to resolve the symbol.
+  // This just makes sure we get good info if available.
+  //
+
+  DWORD64 addr = (DWORD64)aPC;
+  IMAGEHLP_MODULE64 modInfo;
+  IMAGEHLP_LINE64 lineInfo;
+  BOOL modInfoRes;
+  modInfoRes = SymGetModuleInfoEspecial64(myProcess, addr, &modInfo, &lineInfo);
+
+  if (modInfoRes) {
+    strncpy(aDetails->library, modInfo.LoadedImageName,
+            sizeof(aDetails->library));
+    aDetails->library[mozilla::ArrayLength(aDetails->library) - 1] = '\0';
+    aDetails->loffset = (char*)aPC - (char*)modInfo.BaseOfImage;
+
+    if (lineInfo.FileName) {
+      strncpy(aDetails->filename, lineInfo.FileName,
+              sizeof(aDetails->filename));
+      aDetails->filename[mozilla::ArrayLength(aDetails->filename) - 1] = '\0';
+      aDetails->lineno = lineInfo.LineNumber;
+    }
+  }
+
+  ULONG64 buffer[(sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR) +
+                  sizeof(ULONG64) - 1) /
+                 sizeof(ULONG64)];
+  PSYMBOL_INFO pSymbol = (PSYMBOL_INFO)buffer;
+  pSymbol->SizeOfStruct = sizeof(SYMBOL_INFO);
+  pSymbol->MaxNameLen = MAX_SYM_NAME;
+
+  DWORD64 displacement;
+  ok = SymFromAddr(myProcess, addr, &displacement, pSymbol);
+
+  if (ok) {
+    strncpy(aDetails->function, pSymbol->Name, sizeof(aDetails->function));
+    aDetails->function[mozilla::ArrayLength(aDetails->function) - 1] = '\0';
+    aDetails->foffset = static_cast<ptrdiff_t>(displacement);
+  }
+
+  LeaveCriticalSection(&gDbgHelpCS);  // release our lock
+  return true;
+}
+
+// i386 or PPC Linux stackwalking code
+#elif HAVE_DLADDR &&                                           \
+    (HAVE__UNWIND_BACKTRACE || MOZ_STACKWALK_SUPPORTS_LINUX || \
+     MOZ_STACKWALK_SUPPORTS_MACOSX)
+
+#  include <stdlib.h>
+#  include <stdio.h>
+
+// On glibc 2.1, the Dl_info api defined in <dlfcn.h> is only exposed
+// if __USE_GNU is defined.  I suppose its some kind of standards
+// adherence thing.
+//
+#  if (__GLIBC_MINOR__ >= 1) && !defined(__USE_GNU)
+#    define __USE_GNU
+#  endif
+
+// This thing is exported by libstdc++
+// Yes, this is a gcc only hack
+#  if defined(MOZ_DEMANGLE_SYMBOLS)
+#    include <cxxabi.h>
+#  endif  // MOZ_DEMANGLE_SYMBOLS
+
+namespace mozilla {
+
+void DemangleSymbol(const char* aSymbol, char* aBuffer, int aBufLen) {
+  aBuffer[0] = '\0';
+
+#  if defined(MOZ_DEMANGLE_SYMBOLS)
+  /* See demangle.h in the gcc source for the voodoo */
+  char* demangled = abi::__cxa_demangle(aSymbol, 0, 0, 0);
+
+  if (demangled) {
+    strncpy(aBuffer, demangled, aBufLen);
+    aBuffer[aBufLen - 1] = '\0';
+    free(demangled);
+  }
+#  endif  // MOZ_DEMANGLE_SYMBOLS
+}
+
+}  // namespace mozilla
+
+// {x86, ppc} x {Linux, Mac} stackwalking code.
+#  if ((defined(__i386) || defined(PPC) || defined(__ppc__)) && \
+       (MOZ_STACKWALK_SUPPORTS_MACOSX || MOZ_STACKWALK_SUPPORTS_LINUX))
+
+static void DoFramePointerStackWalk(MozWalkStackCallback aCallback,
+                                    const void* aFirstFramePC,
+                                    uint32_t aMaxFrames, void* aClosure,
+                                    void** aBp, void* aStackEnd);
+
+MFBT_API void MozStackWalk(MozWalkStackCallback aCallback,
+                           const void* aFirstFramePC, uint32_t aMaxFrames,
+                           void* aClosure) {
+  // Get the frame pointer
+  void** bp = (void**)__builtin_frame_address(0);
+
+  void* stackEnd;
+#    if HAVE___LIBC_STACK_END
+  stackEnd = __libc_stack_end;
+#    elif defined(XP_DARWIN)
+  stackEnd = pthread_get_stackaddr_np(pthread_self());
+#    elif defined(ANDROID)
+  pthread_attr_t sattr;
+  pthread_attr_init(&sattr);
+  pthread_getattr_np(pthread_self(), &sattr);
+  void* stackBase = stackEnd = nullptr;
+  size_t stackSize = 0;
+  if (gettid() != getpid()) {
+    // bionic's pthread_attr_getstack doesn't tell the truth for the main
+    // thread (see bug 846670). So don't use it for the main thread.
+    if (!pthread_attr_getstack(&sattr, &stackBase, &stackSize)) {
+      stackEnd = static_cast<char*>(stackBase) + stackSize;
+    } else {
+      stackEnd = nullptr;
+    }
+  }
+  if (!stackEnd) {
+    // So consider the current frame pointer + an arbitrary size of 8MB
+    // (modulo overflow ; not really arbitrary as it's the default stack
+    // size for the main thread) if pthread_attr_getstack failed for
+    // some reason (or was skipped).
+    static const uintptr_t kMaxStackSize = 8 * 1024 * 1024;
+    uintptr_t maxStackStart = uintptr_t(-1) - kMaxStackSize;
+    uintptr_t stackStart = std::max(maxStackStart, uintptr_t(bp));
+    stackEnd = reinterpret_cast<void*>(stackStart + kMaxStackSize);
+  }
+#    else
+#      error Unsupported configuration
+#    endif
+  DoFramePointerStackWalk(aCallback, aFirstFramePC, aMaxFrames, aClosure, bp,
+                          stackEnd);
+}
+
+#  elif defined(HAVE__UNWIND_BACKTRACE)
+
+// libgcc_s.so symbols _Unwind_Backtrace@@GCC_3.3 and _Unwind_GetIP@@GCC_3.0
+#    include <unwind.h>
+
+struct unwind_info {
+  MozWalkStackCallback callback;
+  FrameSkipper skipper;
+  int maxFrames;
+  int numFrames;
+  void* closure;
+};
+
+static _Unwind_Reason_Code unwind_callback(struct _Unwind_Context* context,
+                                           void* closure) {
+  unwind_info* info = static_cast<unwind_info*>(closure);
+  void* pc = reinterpret_cast<void*>(_Unwind_GetIP(context));
+  // TODO Use something like '_Unwind_GetGR()' to get the stack pointer.
+  if (!info->skipper.ShouldSkipPC(pc)) {
+    info->numFrames++;
+    (*info->callback)(info->numFrames, pc, nullptr, info->closure);
+    if (info->maxFrames != 0 && info->numFrames == info->maxFrames) {
+      // Again, any error code that stops the walk will do.
+      return _URC_FOREIGN_EXCEPTION_CAUGHT;
+    }
+  }
+  return _URC_NO_REASON;
+}
+
+MFBT_API void MozStackWalk(MozWalkStackCallback aCallback,
+                           const void* aFirstFramePC, uint32_t aMaxFrames,
+                           void* aClosure) {
+  unwind_info info;
+  info.callback = aCallback;
+  info.skipper = FrameSkipper(aFirstFramePC ? aFirstFramePC : CallerPC());
+  info.maxFrames = aMaxFrames;
+  info.numFrames = 0;
+  info.closure = aClosure;
+
+  // We ignore the return value from _Unwind_Backtrace. There are three main
+  // reasons for this.
+  // - On ARM/Android bionic's _Unwind_Backtrace usually (always?) returns
+  //   _URC_FAILURE.  See
+  //   https://bugzilla.mozilla.org/show_bug.cgi?id=717853#c110.
+  // - If aMaxFrames != 0, we want to stop early, and the only way to do that
+  //   is to make unwind_callback return something other than _URC_NO_REASON,
+  //   which causes _Unwind_Backtrace to return a non-success code.
+  // - MozStackWalk doesn't have a return value anyway.
+  (void)_Unwind_Backtrace(unwind_callback, &info);
+}
+
+#  endif
+
+bool MFBT_API MozDescribeCodeAddress(void* aPC,
+                                     MozCodeAddressDetails* aDetails) {
+  aDetails->library[0] = '\0';
+  aDetails->loffset = 0;
+  aDetails->filename[0] = '\0';
+  aDetails->lineno = 0;
+  aDetails->function[0] = '\0';
+  aDetails->foffset = 0;
+
+  Dl_info info;
+
+#  if defined(ANDROID) && defined(MOZ_LINKER)
+  int ok = __wrap_dladdr(aPC, &info);
+#  else
+  int ok = dladdr(aPC, &info);
+#  endif
+
+  if (!ok) {
+    return true;
+  }
+
+  strncpy(aDetails->library, info.dli_fname, sizeof(aDetails->library));
+  aDetails->library[mozilla::ArrayLength(aDetails->library) - 1] = '\0';
+  aDetails->loffset = (char*)aPC - (char*)info.dli_fbase;
+
+#  if !defined(XP_FREEBSD)
+  // On FreeBSD, dli_sname is unusably bad, it often returns things like
+  // 'gtk_xtbin_new' or 'XRE_GetBootstrap' instead of long C++ symbols. Just let
+  // GetFunction do the lookup directly in the ELF image.
+
+  const char* symbol = info.dli_sname;
+  if (!symbol || symbol[0] == '\0') {
+    return true;
+  }
+
+  DemangleSymbol(symbol, aDetails->function, sizeof(aDetails->function));
+
+  if (aDetails->function[0] == '\0') {
+    // Just use the mangled symbol if demangling failed.
+    strncpy(aDetails->function, symbol, sizeof(aDetails->function));
+    aDetails->function[mozilla::ArrayLength(aDetails->function) - 1] = '\0';
+  }
+
+  aDetails->foffset = (char*)aPC - (char*)info.dli_saddr;
+#  endif
+
+  return true;
+}
+
+#else  // unsupported platform.
+
+MFBT_API void MozStackWalk(MozWalkStackCallback aCallback,
+                           const void* aFirstFramePC, uint32_t aMaxFrames,
+                           void* aClosure) {}
+
+MFBT_API bool MozDescribeCodeAddress(void* aPC,
+                                     MozCodeAddressDetails* aDetails) {
+  aDetails->library[0] = '\0';
+  aDetails->loffset = 0;
+  aDetails->filename[0] = '\0';
+  aDetails->lineno = 0;
+  aDetails->function[0] = '\0';
+  aDetails->foffset = 0;
+  return false;
+}
+
+#endif
+
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(XP_LINUX)
+
+#  if defined(XP_MACOSX) && defined(__aarch64__)
+// On macOS arm64, system libraries are arm64e binaries, and arm64e can do
+// pointer authentication: The low bits of the pointer are the actual pointer
+// value, and the high bits are an encrypted hash. During stackwalking, we need
+// to strip off this hash. In theory, ptrauth_strip would be the right function
+// to call for this. However, that function is a no-op unless it's called from
+// code which also builds as arm64e - which we do not. So we cannot use it. So
+// for now, we hardcode a mask that seems to work today: 40 bits for the pointer
+// and 24 bits for the hash seems to do the trick. We can worry about
+// dynamically computing the correct mask if this ever stops working.
+const uintptr_t kPointerMask =
+    (uintptr_t(1) << 40) - 1;  // 40 bits pointer, 24 bit PAC
+#  else
+const uintptr_t kPointerMask = ~uintptr_t(0);
+#  endif
+
+MOZ_ASAN_IGNORE
+static void DoFramePointerStackWalk(MozWalkStackCallback aCallback,
+                                    const void* aFirstFramePC,
+                                    uint32_t aMaxFrames, void* aClosure,
+                                    void** aBp, void* aStackEnd) {
+  // Stack walking code courtesy Kipp's "leaky".
+
+  FrameSkipper skipper(aFirstFramePC);
+  uint32_t numFrames = 0;
+
+  // Sanitize the given aBp. Assume that something reasonably close to
+  // but before the stack end is going be a valid frame pointer. Also
+  // check that it is an aligned address. This increases the chances
+  // that if the pointer is not valid (which might happen if the caller
+  // called __builtin_frame_address(1) and its frame is busted for some
+  // reason), we won't read it, leading to a crash. Because the calling
+  // code is not using frame pointers when returning, it might actually
+  // recover just fine.
+  static const uintptr_t kMaxStackSize = 8 * 1024 * 1024;
+  if (uintptr_t(aBp) < uintptr_t(aStackEnd) -
+                           std::min(kMaxStackSize, uintptr_t(aStackEnd)) ||
+      aBp >= aStackEnd || (uintptr_t(aBp) & 3)) {
+    return;
+  }
+
+  while (aBp) {
+    void** next = (void**)*aBp;
+    // aBp may not be a frame pointer on i386 if code was compiled with
+    // -fomit-frame-pointer, so do some sanity checks.
+    // (aBp should be a frame pointer on ppc(64) but checking anyway may help
+    // a little if the stack has been corrupted.)
+    // We don't need to check against the begining of the stack because
+    // we can assume that aBp > sp
+    if (next <= aBp || next >= aStackEnd || (uintptr_t(next) & 3)) {
+      break;
+    }
+#  if (defined(__ppc__) && defined(XP_MACOSX)) || defined(__powerpc64__)
+    // ppc mac or powerpc64 linux
+    void* pc = *(aBp + 2);
+    aBp += 3;
+#  else  // i386 or powerpc32 linux
+    void* pc = *(aBp + 1);
+    aBp += 2;
+#  endif
+
+    // Strip off pointer authentication hash, if present. For now, it looks
+    // like only return addresses require stripping, and stack pointers do
+    // not. This might change in the future.
+    pc = (void*)((uintptr_t)pc & kPointerMask);
+
+    if (!skipper.ShouldSkipPC(pc)) {
+      // Assume that the SP points to the BP of the function
+      // it called. We can't know the exact location of the SP
+      // but this should be sufficient for our use the SP
+      // to order elements on the stack.
+      numFrames++;
+      (*aCallback)(numFrames, pc, aBp, aClosure);
+      if (aMaxFrames != 0 && numFrames == aMaxFrames) {
+        break;
+      }
+    }
+    aBp = next;
+  }
+}
+
+namespace mozilla {
+
+MFBT_API void FramePointerStackWalk(MozWalkStackCallback aCallback,
+                                    uint32_t aMaxFrames, void* aClosure,
+                                    void** aBp, void* aStackEnd) {
+  // We don't pass a aFirstFramePC because we start walking the stack from the
+  // frame at aBp.
+  DoFramePointerStackWalk(aCallback, nullptr, aMaxFrames, aClosure, aBp,
+                          aStackEnd);
+}
+
+}  // namespace mozilla
+
+#else
+
+namespace mozilla {
+MFBT_API void FramePointerStackWalk(MozWalkStackCallback aCallback,
+                                    uint32_t aMaxFrames, void* aClosure,
+                                    void** aBp, void* aStackEnd) {}
+}  // namespace mozilla
+
+#endif
+
+MFBT_API int MozFormatCodeAddressDetails(
+    char* aBuffer, uint32_t aBufferSize, uint32_t aFrameNumber, void* aPC,
+    const MozCodeAddressDetails* aDetails) {
+  return MozFormatCodeAddress(aBuffer, aBufferSize, aFrameNumber, aPC,
+                              aDetails->function, aDetails->library,
+                              aDetails->loffset, aDetails->filename,
+                              aDetails->lineno);
+}
+
+MFBT_API int MozFormatCodeAddress(char* aBuffer, uint32_t aBufferSize,
+                                  uint32_t aFrameNumber, const void* aPC,
+                                  const char* aFunction, const char* aLibrary,
+                                  ptrdiff_t aLOffset, const char* aFileName,
+                                  uint32_t aLineNo) {
+  const char* function = aFunction && aFunction[0] ? aFunction : "???";
+  if (aFileName && aFileName[0]) {
+    // We have a filename and (presumably) a line number. Use them.
+    return SprintfBuf(aBuffer, aBufferSize, "#%02u: %s (%s:%u)", aFrameNumber,
+                      function, aFileName, aLineNo);
+  } else if (aLibrary && aLibrary[0]) {
+    // We have no filename, but we do have a library name. Use it and the
+    // library offset, and print them in a way that `fix_stacks.py` can
+    // post-process.
+    return SprintfBuf(aBuffer, aBufferSize, "#%02u: %s[%s +0x%" PRIxPTR "]",
+                      aFrameNumber, function, aLibrary,
+                      static_cast<uintptr_t>(aLOffset));
+  } else {
+    // We have nothing useful to go on. (The format string is split because
+    // '??)' is a trigraph and causes a warning, sigh.)
+    return SprintfBuf(aBuffer, aBufferSize,
+                      "#%02u: ??? (???:???"
+                      ")",
+                      aFrameNumber);
+  }
+}
+
+static void EnsureWrite(FILE* aStream, const char* aBuf, size_t aLen) {
+#ifdef XP_WIN
+  int fd = _fileno(aStream);
+#else
+  int fd = fileno(aStream);
+#endif
+  while (aLen > 0) {
+#ifdef XP_WIN
+    auto written = _write(fd, aBuf, aLen);
+#else
+    auto written = write(fd, aBuf, aLen);
+#endif
+    if (written <= 0 || size_t(written) > aLen) {
+      break;
+    }
+    aBuf += written;
+    aLen -= written;
+  }
+}
+
+template <int N>
+static int PrintStackFrameBuf(char (&aBuf)[N], uint32_t aFrameNumber, void* aPC,
+                              void* aSP) {
+  MozCodeAddressDetails details;
+  MozDescribeCodeAddress(aPC, &details);
+  int len =
+      MozFormatCodeAddressDetails(aBuf, N - 1, aFrameNumber, aPC, &details);
+  len = std::min(len, N - 2);
+  aBuf[len++] = '\n';
+  aBuf[len] = '\0';
+  return len;
+}
+
+static void PrintStackFrame(uint32_t aFrameNumber, void* aPC, void* aSP,
+                            void* aClosure) {
+  FILE* stream = (FILE*)aClosure;
+  char buf[1025];  // 1024 + 1 for trailing '\n'
+  int len = PrintStackFrameBuf(buf, aFrameNumber, aPC, aSP);
+  fflush(stream);
+  EnsureWrite(stream, buf, len);
+}
+
+static bool WalkTheStackEnabled() {
+  static bool result = [] {
+    char* value = getenv("MOZ_DISABLE_WALKTHESTACK");
+    return !(value && value[0]);
+  }();
+  return result;
+}
+
+MFBT_API void MozWalkTheStack(FILE* aStream, const void* aFirstFramePC,
+                              uint32_t aMaxFrames) {
+  if (WalkTheStackEnabled()) {
+    MozStackWalk(PrintStackFrame, aFirstFramePC ? aFirstFramePC : CallerPC(),
+                 aMaxFrames, aStream);
+  }
+}
+
+static void WriteStackFrame(uint32_t aFrameNumber, void* aPC, void* aSP,
+                            void* aClosure) {
+  auto writer = (void (*)(const char*))aClosure;
+  char buf[1024];
+  PrintStackFrameBuf(buf, aFrameNumber, aPC, aSP);
+  writer(buf);
+}
+
+MFBT_API void MozWalkTheStackWithWriter(void (*aWriter)(const char*),
+                                        const void* aFirstFramePC,
+                                        uint32_t aMaxFrames) {
+  if (WalkTheStackEnabled()) {
+    MozStackWalk(WriteStackFrame, aFirstFramePC ? aFirstFramePC : CallerPC(),
+                 aMaxFrames, (void*)aWriter);
+  }
+}