mozglue/misc/StackWalk.cpp
author Gerald Squelart <gsquelart@mozilla.com>
Thu, 04 Jul 2019 04:38:16 +0000
changeset 481213 8fed7bc35767fdfab4bac0908ae9b21c08f49e1f
parent 460135 72b7154c2310c2892e2d8eb9cd9d3d0c71cb1de3
child 487843 aff5ac8555913b8383bd3e7edf2da45619a203dd
permissions -rw-r--r--
Bug 1559000 - mozglue's AutoProfilerLabel doesn't need to know about ProfilingStack - r=mstange `ProfilingStack*` happens to be the information that the current Gecko Profiler entry function wants to forward to the exit function, but AutoProfilerLabel does not really need to know about that. Changing it to `void*`, so that we can later use different entry/exit functions that use different context types. Differential Revision: https://phabricator.services.mozilla.com/D34806

/* -*- 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/Attributes.h"
#include "mozilla/IntegerPrintfMacros.h"
#include "mozilla/StackWalk.h"

#include <string.h>

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

#if MOZ_STACKWALK_SUPPORTS_WINDOWS

#  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

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;
  CONTEXT* context;
};

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;

MFBT_API
AutoSuppressStackWalking::AutoSuppressStackWalking() {
  ++sStackWalkSuppressions;
}

MFBT_API
AutoSuppressStackWalking::~AutoSuppressStackWalking() {
  --sStackWalkSuppressions;
}

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;
}

static void WalkStackMain64(struct WalkStackData* aData) {
  // Get a context for the specified thread.
  CONTEXT context_buf;
  CONTEXT* context;
  if (!aData->context) {
    context = &context_buf;
    memset(context, 0, sizeof(CONTEXT));
    context->ContextFlags = CONTEXT_FULL;
    if (aData->walkCallingThread) {
      ::RtlCaptureContext(context);
    } else if (!GetThreadContext(aData->thread, context)) {
      return;
    }
  } else {
    context = aData->context;
  }

#  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

#  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

  // 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) || defined(_M_ARM64)

#    if defined(_M_AMD64)
    auto currentInstr = context->Rip;
#    elif defined(_M_ARM64)
    auto currentInstr = context->Pc;
#    endif

    // 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, &dummyHandlerData,
                       &dummyEstablisherFrame, nullptr);
    } else if (firstFrame) {
      // Leaf functions can be unwound by hand.
#    if defined(_M_AMD64)
      context->Rip = *reinterpret_cast<DWORD64*>(context->Rsp);
      context->Rsp += sizeof(void*);
#    elif defined(_M_ARM64)
      context->Pc = *reinterpret_cast<DWORD64*>(context->Sp);
      context->Sp += sizeof(void*);
#    endif
    } else {
      // Something went wrong.
      break;
    }

#    if defined(_M_AMD64)
    addr = context->Rip;
    spaddr = context->Rsp;
#    elif defined(_M_ARM64)
    addr = context->Pc;
    spaddr = context->Sp;
#    endif
    firstFrame = false;
#  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
  }
}

/**
 * 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 void MozStackWalkThread(MozWalkStackCallback aCallback,
                                 uint32_t aSkipFrames, uint32_t aMaxFrames,
                                 void* aClosure, HANDLE aThread,
                                 CONTEXT* aContext) {
  static HANDLE myProcess = nullptr;
  HANDLE myThread;
  struct WalkStackData data;

  InitializeDbgHelpCriticalSection();

  HANDLE targetThread = aThread;
  if (!aThread) {
    targetThread = ::GetCurrentThread();
    data.walkCallingThread = true;
  } else {
    DWORD threadId = ::GetThreadId(aThread);
    DWORD currentThreadId = ::GetCurrentThreadId();
    data.walkCallingThread = (threadId == currentThreadId);
  }

  // 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;
    }
  }
  if (!::DuplicateHandle(::GetCurrentProcess(), targetThread,
                         ::GetCurrentProcess(), &myThread, THREAD_ALL_ACCESS,
                         FALSE, 0)) {
    if (data.walkCallingThread) {
      PrintError("DuplicateHandle (thread)");
    }
    return;
  }

  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.context = aContext;

  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);
  }

  ::CloseHandle(myThread);

  for (uint32_t i = 0; i < data.pc_count; ++i) {
    (*aCallback)(i + 1, data.pcs[i], data.sps[i], aClosure);
  }
}

MFBT_API void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {
  MozStackWalkThread(aCallback, aSkipFrames, 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 <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 void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           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
  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;
  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->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 void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {
  unwind_info info;
  info.callback = aCallback;
  info.skip = aSkipFrames + 1;
  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;
  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 void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           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)
namespace mozilla {
MOZ_ASAN_BLACKLIST
void FramePointerStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure, void** aBp,
                           void* aStackEnd) {
  // Stack walking code courtesy Kipp's "leaky".

  int32_t skip = aSkipFrames;
  uint32_t numFrames = 0;
  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
    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, aBp, aClosure);
      if (aMaxFrames != 0 && numFrames == aMaxFrames) {
        break;
      }
    }
    aBp = next;
  }
}
}  // namespace mozilla

#else

namespace mozilla {
MFBT_API void FramePointerStackWalk(MozWalkStackCallback aCallback,
                                    uint32_t aSkipFrames, uint32_t aMaxFrames,
                                    void* aClosure, void** aBp,
                                    void* aStackEnd) {}
}  // namespace mozilla

#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);
  }
}