Add m-esr52 at 52.6.0

1 files changed, 1204 insertions, 0 deletions

diff --git a/mozglue/misc/StackWalk.cpp b/mozglue/misc/StackWalk.cpp
new file mode 100644
index 0000000000..bb23b922a8
--- /dev/null
+++ b/mozglue/misc/StackWalk.cpp
@@ -0,0 +1,1204 @@
+/* -*- 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/Assertions.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/StackWalk.h"
+
+#include <string.h>
+
+using namespace mozilla;
+
+// The presence of this address is the stack must stop the stack walk. If
+// there is no such address, the structure will be {nullptr, true}.
+struct CriticalAddress
+{
+  void* mAddr;
+  bool mInit;
+};
+static CriticalAddress gCriticalAddress;
+
+// 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
+
+#if MOZ_STACKWALK_SUPPORTS_MACOSX
+#include <pthread.h>
+#include <sys/errno.h>
+#ifdef MOZ_WIDGET_COCOA
+#include <CoreServices/CoreServices.h>
+#endif
+
+typedef void
+malloc_logger_t(uint32_t aType,
+                uintptr_t aArg1, uintptr_t aArg2, uintptr_t aArg3,
+                uintptr_t aResult, uint32_t aNumHotFramesToSkip);
+extern malloc_logger_t* malloc_logger;
+
+static void
+stack_callback(uint32_t aFrameNumber, void* aPc, void* aSp, void* aClosure)
+{
+  const char* name = static_cast<char*>(aClosure);
+  Dl_info info;
+
+  // On Leopard dladdr returns the wrong value for "new_sem_from_pool". The
+  // stack shows up as having two pthread_cond_wait$UNIX2003 frames. The
+  // correct one is the first that we find on our way up, so the
+  // following check for gCriticalAddress.mAddr is critical.
+  if (gCriticalAddress.mAddr || dladdr(aPc, &info) == 0  ||
+      !info.dli_sname || strcmp(info.dli_sname, name) != 0) {
+    return;
+  }
+  gCriticalAddress.mAddr = aPc;
+}
+
+static void
+my_malloc_logger(uint32_t aType,
+                 uintptr_t aArg1, uintptr_t aArg2, uintptr_t aArg3,
+                 uintptr_t aResult, uint32_t aNumHotFramesToSkip)
+{
+  static bool once = false;
+  if (once) {
+    return;
+  }
+  once = true;
+
+  // On Leopard dladdr returns the wrong value for "new_sem_from_pool". The
+  // stack shows up as having two pthread_cond_wait$UNIX2003 frames.
+  const char* name = "new_sem_from_pool";
+  MozStackWalk(stack_callback, /* skipFrames */ 0, /* maxFrames */ 0,
+               const_cast<char*>(name), 0, nullptr);
+}
+
+// This is called from NS_LogInit() and from the stack walking functions, but
+// only the first call has any effect.  We need to call this function from both
+// places because it must run before any mutexes are created, and also before
+// any objects whose refcounts we're logging are created.  Running this
+// function during NS_LogInit() ensures that we meet the first criterion, and
+// running this function during the stack walking functions ensures we meet the
+// second criterion.
+MFBT_API void
+StackWalkInitCriticalAddress()
+{
+  if (gCriticalAddress.mInit) {
+    return;
+  }
+  gCriticalAddress.mInit = true;
+  // We must not do work when 'new_sem_from_pool' calls realloc, since
+  // it holds a non-reentrant spin-lock and we will quickly deadlock.
+  // new_sem_from_pool is not directly accessible using dlsym, so
+  // we force a situation where new_sem_from_pool is on the stack and
+  // use dladdr to check the addresses.
+
+  // malloc_logger can be set by external tools like 'Instruments' or 'leaks'
+  malloc_logger_t* old_malloc_logger = malloc_logger;
+  malloc_logger = my_malloc_logger;
+
+  pthread_cond_t cond;
+  int r = pthread_cond_init(&cond, 0);
+  MOZ_ASSERT(r == 0);
+  pthread_mutex_t mutex;
+  r = pthread_mutex_init(&mutex, 0);
+  MOZ_ASSERT(r == 0);
+  r = pthread_mutex_lock(&mutex);
+  MOZ_ASSERT(r == 0);
+  struct timespec abstime = { 0, 1 };
+  r = pthread_cond_timedwait_relative_np(&cond, &mutex, &abstime);
+
+  // restore the previous malloc logger
+  malloc_logger = old_malloc_logger;
+
+  MOZ_ASSERT(r == ETIMEDOUT);
+  r = pthread_mutex_unlock(&mutex);
+  MOZ_ASSERT(r == 0);
+  r = pthread_mutex_destroy(&mutex);
+  MOZ_ASSERT(r == 0);
+  r = pthread_cond_destroy(&cond);
+  MOZ_ASSERT(r == 0);
+}
+
+static bool
+IsCriticalAddress(void* aPC)
+{
+  return gCriticalAddress.mAddr == aPC;
+}
+#else
+static bool
+IsCriticalAddress(void* aPC)
+{
+  return false;
+}
+// We still initialize gCriticalAddress.mInit so that this code behaves
+// the same on all platforms. Otherwise a failure to init would be visible
+// only on OS X.
+MFBT_API void
+StackWalkInitCriticalAddress()
+{
+  gCriticalAddress.mInit = true;
+}
+#endif
+
+#if defined(_WIN32) && (defined(_M_IX86) || defined(_M_AMD64) || defined(_M_IA64)) // WIN32 x86 stack walking code
+
+#include <windows.h>
+#include <process.h>
+#include <stdio.h>
+#include <malloc.h>
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/StackWalk_windows.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
+
+struct WalkStackData
+{
+  // Are we walking the stack of the calling thread? Note that we need to avoid
+  // calling fprintf and friends if this is false, in order to avoid deadlocks.
+  bool walkCallingThread;
+  uint32_t skipFrames;
+  HANDLE thread;
+  HANDLE process;
+  HANDLE eventStart;
+  HANDLE eventEnd;
+  void** pcs;
+  uint32_t pc_size;
+  uint32_t pc_count;
+  uint32_t pc_max;
+  void** sps;
+  uint32_t sp_size;
+  uint32_t sp_count;
+  void* platformData;
+};
+
+DWORD gStackWalkThread;
+CRITICAL_SECTION gDbgHelpCS;
+
+// 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 unsigned int WINAPI WalkStackThread(void* aData);
+
+static bool
+EnsureWalkThreadReady()
+{
+  static bool walkThreadReady = false;
+  static HANDLE stackWalkThread = nullptr;
+  static HANDLE readyEvent = nullptr;
+
+  if (walkThreadReady) {
+    return walkThreadReady;
+  }
+
+  if (!stackWalkThread) {
+    readyEvent = ::CreateEvent(nullptr, FALSE /* auto-reset*/,
+                               FALSE /* initially non-signaled */,
+                               nullptr);
+    if (!readyEvent) {
+      PrintError("CreateEvent");
+      return false;
+    }
+
+    unsigned int threadID;
+    stackWalkThread = (HANDLE)_beginthreadex(nullptr, 0, WalkStackThread,
+                                             (void*)readyEvent, 0, &threadID);
+    if (!stackWalkThread) {
+      PrintError("CreateThread");
+      ::CloseHandle(readyEvent);
+      readyEvent = nullptr;
+      return false;
+    }
+    gStackWalkThread = threadID;
+    ::CloseHandle(stackWalkThread);
+  }
+
+  MOZ_ASSERT((stackWalkThread && readyEvent) ||
+             (!stackWalkThread && !readyEvent));
+
+  // The thread was created. Try to wait an arbitrary amount of time (1 second
+  // should be enough) for its event loop to start before posting events to it.
+  DWORD waitRet = ::WaitForSingleObject(readyEvent, 1000);
+  if (waitRet == WAIT_TIMEOUT) {
+    // We get a timeout if we're called during static initialization because
+    // the thread will only start executing after we return so it couldn't
+    // have signalled the event. If that is the case, give up for now and
+    // try again next time we're called.
+    return false;
+  }
+  ::CloseHandle(readyEvent);
+  stackWalkThread = nullptr;
+  readyEvent = nullptr;
+
+
+  ::InitializeCriticalSection(&gDbgHelpCS);
+
+  return walkThreadReady = true;
+}
+
+static void
+WalkStackMain64(struct WalkStackData* aData)
+{
+  // Get a context for the specified thread.
+  CONTEXT context;
+  if (!aData->platformData) {
+    memset(&context, 0, sizeof(CONTEXT));
+    context.ContextFlags = CONTEXT_FULL;
+    if (!GetThreadContext(aData->thread, &context)) {
+      if (aData->walkCallingThread) {
+        PrintError("GetThreadContext");
+      }
+      return;
+    }
+  } else {
+    context = *static_cast<CONTEXT*>(aData->platformData);
+  }
+
+#if defined(_M_IX86) || defined(_M_IA64)
+  // Setup initial stack frame to walk from.
+  STACKFRAME64 frame64;
+  memset(&frame64, 0, sizeof(frame64));
+#ifdef _M_IX86
+  frame64.AddrPC.Offset    = context.Eip;
+  frame64.AddrStack.Offset = context.Esp;
+  frame64.AddrFrame.Offset = context.Ebp;
+#elif defined _M_IA64
+  frame64.AddrPC.Offset    = context.StIIP;
+  frame64.AddrStack.Offset = context.SP;
+  frame64.AddrFrame.Offset = context.RsBSP;
+#endif
+  frame64.AddrPC.Mode      = AddrModeFlat;
+  frame64.AddrStack.Mode   = AddrModeFlat;
+  frame64.AddrFrame.Mode   = AddrModeFlat;
+  frame64.AddrReturn.Mode  = AddrModeFlat;
+#endif
+
+  // Skip our own stack walking frames.
+  int skip = (aData->walkCallingThread ? 3 : 0) + aData->skipFrames;
+
+  // Now walk the stack.
+  while (true) {
+    DWORD64 addr;
+    DWORD64 spaddr;
+
+#if defined(_M_IX86) || defined(_M_IA64)
+    // 32-bit frame unwinding.
+    // Debug routines are not threadsafe, so grab the lock.
+    EnterCriticalSection(&gDbgHelpCS);
+    BOOL ok = StackWalk64(
+#if defined _M_IA64
+      IMAGE_FILE_MACHINE_IA64,
+#elif defined _M_IX86
+      IMAGE_FILE_MACHINE_I386,
+#endif
+      aData->process,
+      aData->thread,
+      &frame64,
+      &context,
+      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 (aData->walkCallingThread) {
+        PrintError("WalkStack64");
+      }
+    }
+
+    if (!ok) {
+      break;
+    }
+
+#elif defined(_M_AMD64)
+    // 64-bit frame unwinding.
+    // Try to look up unwind metadata for the current function.
+    ULONG64 imageBase;
+    PRUNTIME_FUNCTION runtimeFunction =
+      RtlLookupFunctionEntry(context.Rip, &imageBase, NULL);
+
+    if (!runtimeFunction) {
+      // Alas, this is probably a JIT frame, for which we don't generate unwind
+      // info and so we have to give up.
+      break;
+    }
+
+    PVOID dummyHandlerData;
+    ULONG64 dummyEstablisherFrame;
+    RtlVirtualUnwind(UNW_FLAG_NHANDLER,
+                     imageBase,
+                     context.Rip,
+                     runtimeFunction,
+                     &context,
+                     &dummyHandlerData,
+                     &dummyEstablisherFrame,
+                     nullptr);
+
+    addr = context.Rip;
+    spaddr = context.Rsp;
+
+#else
+#error "unknown platform"
+#endif
+
+    if (addr == 0) {
+      break;
+    }
+
+    if (skip-- > 0) {
+      continue;
+    }
+
+    if (aData->pc_count < aData->pc_size) {
+      aData->pcs[aData->pc_count] = (void*)addr;
+    }
+    ++aData->pc_count;
+
+    if (aData->sp_count < aData->sp_size) {
+      aData->sps[aData->sp_count] = (void*)spaddr;
+    }
+    ++aData->sp_count;
+
+    if (aData->pc_max != 0 && aData->pc_count == aData->pc_max) {
+      break;
+    }
+
+#if defined(_M_IX86) || defined(_M_IA64)
+    if (frame64.AddrReturn.Offset == 0) {
+      break;
+    }
+#endif
+  }
+}
+
+// The JIT needs to allocate executable memory. Because of the inanity of
+// the win64 APIs, this requires locks that stalk walkers also need. Provide
+// another lock to allow synchronization around these resources.
+#ifdef _M_AMD64
+
+struct CriticalSectionAutoInitializer {
+    CRITICAL_SECTION lock;
+
+    CriticalSectionAutoInitializer() {
+      InitializeCriticalSection(&lock);
+    }
+};
+
+static CriticalSectionAutoInitializer gWorkaroundLock;
+
+#endif // _M_AMD64
+
+MFBT_API void
+AcquireStackWalkWorkaroundLock()
+{
+#ifdef _M_AMD64
+  EnterCriticalSection(&gWorkaroundLock.lock);
+#endif
+}
+
+MFBT_API bool
+TryAcquireStackWalkWorkaroundLock()
+{
+#ifdef _M_AMD64
+  return TryEnterCriticalSection(&gWorkaroundLock.lock);
+#else
+  return true;
+#endif
+}
+
+MFBT_API void
+ReleaseStackWalkWorkaroundLock()
+{
+#ifdef _M_AMD64
+  LeaveCriticalSection(&gWorkaroundLock.lock);
+#endif
+}
+
+static unsigned int WINAPI
+WalkStackThread(void* aData)
+{
+  BOOL msgRet;
+  MSG msg;
+
+  // Call PeekMessage to force creation of a message queue so that
+  // other threads can safely post events to us.
+  ::PeekMessage(&msg, nullptr, WM_USER, WM_USER, PM_NOREMOVE);
+
+  // and tell the thread that created us that we're ready.
+  HANDLE readyEvent = (HANDLE)aData;
+  ::SetEvent(readyEvent);
+
+  while ((msgRet = ::GetMessage(&msg, (HWND)-1, 0, 0)) != 0) {
+    if (msgRet == -1) {
+      PrintError("GetMessage");
+    } else {
+      DWORD ret;
+
+      struct WalkStackData* data = (WalkStackData*)msg.lParam;
+      if (!data) {
+        continue;
+      }
+
+      // Don't suspend the calling thread until it's waiting for
+      // us; otherwise the number of frames on the stack could vary.
+      ret = ::WaitForSingleObject(data->eventStart, INFINITE);
+      if (ret != WAIT_OBJECT_0) {
+        PrintError("WaitForSingleObject");
+      }
+
+      // Suspend the calling thread, dump his stack, and then resume him.
+      // He's currently waiting for us to finish so now should be a good time.
+      ret = ::SuspendThread(data->thread);
+      if (ret == -1) {
+        PrintError("ThreadSuspend");
+      } else {
+        WalkStackMain64(data);
+
+        ret = ::ResumeThread(data->thread);
+        if (ret == -1) {
+          PrintError("ThreadResume");
+        }
+      }
+
+      ::SetEvent(data->eventEnd);
+    }
+  }
+
+  return 0;
+}
+
+/**
+ * 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.
+ */
+
+MFBT_API bool
+MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+             uint32_t aMaxFrames, void* aClosure, uintptr_t aThread,
+             void* aPlatformData)
+{
+  StackWalkInitCriticalAddress();
+  static HANDLE myProcess = nullptr;
+  HANDLE myThread;
+  DWORD walkerReturn;
+  struct WalkStackData data;
+
+  if (!EnsureWalkThreadReady()) {
+    return false;
+  }
+
+  HANDLE currentThread = ::GetCurrentThread();
+  HANDLE targetThread =
+    aThread ? reinterpret_cast<HANDLE>(aThread) : currentThread;
+  data.walkCallingThread = (targetThread == currentThread);
+
+  // Have to duplicate handle to get a real handle.
+  if (!myProcess) {
+    if (!::DuplicateHandle(::GetCurrentProcess(),
+                           ::GetCurrentProcess(),
+                           ::GetCurrentProcess(),
+                           &myProcess,
+                           PROCESS_ALL_ACCESS, FALSE, 0)) {
+      if (data.walkCallingThread) {
+        PrintError("DuplicateHandle (process)");
+      }
+      return false;
+    }
+  }
+  if (!::DuplicateHandle(::GetCurrentProcess(),
+                         targetThread,
+                         ::GetCurrentProcess(),
+                         &myThread,
+                         THREAD_ALL_ACCESS, FALSE, 0)) {
+    if (data.walkCallingThread) {
+      PrintError("DuplicateHandle (thread)");
+    }
+    return false;
+  }
+
+  data.skipFrames = aSkipFrames;
+  data.thread = myThread;
+  data.process = myProcess;
+  void* local_pcs[1024];
+  data.pcs = local_pcs;
+  data.pc_count = 0;
+  data.pc_size = ArrayLength(local_pcs);
+  data.pc_max = aMaxFrames;
+  void* local_sps[1024];
+  data.sps = local_sps;
+  data.sp_count = 0;
+  data.sp_size = ArrayLength(local_sps);
+  data.platformData = aPlatformData;
+
+  if (aThread) {
+    // If we're walking the stack of another thread, we don't need to
+    // use a separate walker thread.
+    WalkStackMain64(&data);
+
+    if (data.pc_count > data.pc_size) {
+      data.pcs = (void**)_alloca(data.pc_count * sizeof(void*));
+      data.pc_size = data.pc_count;
+      data.pc_count = 0;
+      data.sps = (void**)_alloca(data.sp_count * sizeof(void*));
+      data.sp_size = data.sp_count;
+      data.sp_count = 0;
+      WalkStackMain64(&data);
+    }
+  } else {
+    data.eventStart = ::CreateEvent(nullptr, FALSE /* auto-reset*/,
+                                    FALSE /* initially non-signaled */, nullptr);
+    data.eventEnd = ::CreateEvent(nullptr, FALSE /* auto-reset*/,
+                                  FALSE /* initially non-signaled */, nullptr);
+
+    ::PostThreadMessage(gStackWalkThread, WM_USER, 0, (LPARAM)&data);
+
+    walkerReturn = ::SignalObjectAndWait(data.eventStart,
+                                         data.eventEnd, INFINITE, FALSE);
+    if (walkerReturn != WAIT_OBJECT_0 && data.walkCallingThread) {
+      PrintError("SignalObjectAndWait (1)");
+    }
+    if (data.pc_count > data.pc_size) {
+      data.pcs = (void**)_alloca(data.pc_count * sizeof(void*));
+      data.pc_size = data.pc_count;
+      data.pc_count = 0;
+      data.sps = (void**)_alloca(data.sp_count * sizeof(void*));
+      data.sp_size = data.sp_count;
+      data.sp_count = 0;
+      ::PostThreadMessage(gStackWalkThread, WM_USER, 0, (LPARAM)&data);
+      walkerReturn = ::SignalObjectAndWait(data.eventStart,
+                                           data.eventEnd, INFINITE, FALSE);
+      if (walkerReturn != WAIT_OBJECT_0 && data.walkCallingThread) {
+        PrintError("SignalObjectAndWait (2)");
+      }
+    }
+
+    ::CloseHandle(data.eventStart);
+    ::CloseHandle(data.eventEnd);
+  }
+
+  ::CloseHandle(myThread);
+
+  for (uint32_t i = 0; i < data.pc_count; ++i) {
+    (*aCallback)(i + 1, data.pcs[i], data.sps[i], aClosure);
+  }
+
+  return data.pc_count != 0;
+}
+
+
+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;
+  }
+
+  if (!EnsureWalkThreadReady()) {
+    return false;
+  }
+
+  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 <string.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
+
+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
+}
+
+// {x86, ppc} x {Linux, Mac} stackwalking code.
+#if ((defined(__i386) || defined(PPC) || defined(__ppc__)) && \
+     (MOZ_STACKWALK_SUPPORTS_MACOSX || MOZ_STACKWALK_SUPPORTS_LINUX))
+
+MFBT_API bool
+MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+             uint32_t aMaxFrames, void* aClosure, uintptr_t aThread,
+             void* aPlatformData)
+{
+  MOZ_ASSERT(!aThread);
+  MOZ_ASSERT(!aPlatformData);
+  StackWalkInitCriticalAddress();
+
+  // 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
+  return FramePointerStackWalk(aCallback, aSkipFrames, 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;
+  int skip;
+  int maxFrames;
+  int numFrames;
+  bool isCriticalAbort;
+  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 (IsCriticalAddress(pc)) {
+    info->isCriticalAbort = true;
+    // We just want to stop the walk, so any error code will do.  Using
+    // _URC_NORMAL_STOP would probably be the most accurate, but it is not
+    // defined on Android for ARM.
+    return _URC_FOREIGN_EXCEPTION_CAUGHT;
+  }
+  if (--info->skip < 0) {
+    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 bool
+MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+             uint32_t aMaxFrames, void* aClosure, uintptr_t aThread,
+             void* aPlatformData)
+{
+  MOZ_ASSERT(!aThread);
+  MOZ_ASSERT(!aPlatformData);
+  StackWalkInitCriticalAddress();
+  unwind_info info;
+  info.callback = aCallback;
+  info.skip = aSkipFrames + 1;
+  info.maxFrames = aMaxFrames;
+  info.numFrames = 0;
+  info.isCriticalAbort = false;
+  info.closure = aClosure;
+
+  (void)_Unwind_Backtrace(unwind_callback, &info);
+
+  // We ignore the return value from _Unwind_Backtrace and instead determine
+  // the outcome from |info|.  There are two 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.
+  if (info.isCriticalAbort) {
+    return false;
+  }
+  return info.numFrames != 0;
+}
+
+#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;
+  int ok = dladdr(aPC, &info);
+  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;
+
+  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;
+  return true;
+}
+
+#else // unsupported platform.
+
+MFBT_API bool
+MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+             uint32_t aMaxFrames, void* aClosure, uintptr_t aThread,
+             void* aPlatformData)
+{
+  MOZ_ASSERT(!aThread);
+  MOZ_ASSERT(!aPlatformData);
+  return false;
+}
+
+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)
+namespace mozilla {
+bool
+FramePointerStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+                      uint32_t aMaxFrames, void* aClosure, void** bp,
+                      void* aStackEnd)
+{
+  // Stack walking code courtesy Kipp's "leaky".
+
+  int32_t skip = aSkipFrames;
+  uint32_t numFrames = 0;
+  while (bp) {
+    void** next = (void**)*bp;
+    // bp may not be a frame pointer on i386 if code was compiled with
+    // -fomit-frame-pointer, so do some sanity checks.
+    // (bp 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 bp > sp
+    if (next <= bp ||
+        next > aStackEnd ||
+        (uintptr_t(next) & 3)) {
+      break;
+    }
+#if (defined(__ppc__) && defined(XP_MACOSX)) || defined(__powerpc64__)
+    // ppc mac or powerpc64 linux
+    void* pc = *(bp + 2);
+    bp += 3;
+#else // i386 or powerpc32 linux
+    void* pc = *(bp + 1);
+    bp += 2;
+#endif
+    if (IsCriticalAddress(pc)) {
+      return false;
+    }
+    if (--skip < 0) {
+      // 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, bp, aClosure);
+      if (aMaxFrames != 0 && numFrames == aMaxFrames) {
+        break;
+      }
+    }
+    bp = next;
+  }
+  return numFrames != 0;
+}
+} // namespace mozilla
+
+#else
+
+namespace mozilla {
+MFBT_API bool
+FramePointerStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
+                      void* aClosure, void** aBp)
+{
+  return false;
+}
+}
+
+#endif
+
+MFBT_API void
+MozFormatCodeAddressDetails(char* aBuffer, uint32_t aBufferSize,
+                            uint32_t aFrameNumber, void* aPC,
+                            const MozCodeAddressDetails* aDetails)
+{
+  MozFormatCodeAddress(aBuffer, aBufferSize,
+                       aFrameNumber, aPC, aDetails->function,
+                       aDetails->library, aDetails->loffset,
+                       aDetails->filename, aDetails->lineno);
+}
+
+MFBT_API void
+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.
+    snprintf(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 scripts like
+    // fix_{linux,macosx}_stacks.py can easily post-process.
+    snprintf(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.)
+    snprintf(aBuffer, aBufferSize,
+             "#%02u: ??? (???:???" ")",
+             aFrameNumber);
+  }
+}