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/* -*- 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
/* API for getting a stack trace of the C/C++ stack on the current thread */
#include "mozilla/ArrayUtils.h"
#include "mozilla/Atomics.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() : mSkipUntilAddr(0) {}
static uintptr_t AddressFromPC(const void* aPC) {
#ifdef __arm__
// On 32-bit ARM, mask off the thumb bit to get the instruction address.
return uintptr_t(aPC) & ~1;
#else
return uintptr_t(aPC);
#endif
}
bool ShouldSkipPC(void* aPC) {
// Skip frames until we encounter the one we were initialized with,
// and then never skip again.
uintptr_t instructionAddress = AddressFromPC(aPC);
if (mSkipUntilAddr != 0) {
if (mSkipUntilAddr != instructionAddress) {
return true;
}
mSkipUntilAddr = 0;
}
return false;
}
explicit FrameSkipper(const void* aPC) : mSkipUntilAddr(AddressFromPC(aPC)) {}
private:
uintptr_t mSkipUntilAddr;
};
#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
// DbgHelp functions are not thread-safe and should therefore be protected by
// using this critical section. Only use the critical section after a
// successful call to InitializeDbgHelp().
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() {
auto previousValue = sStackWalkSuppressions--;
// example in which this occured.
MOZ_RELEASE_ASSERT(previousValue);
}
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);
}
enum class DbgHelpInitFlags : bool {
BasicInit,
WithSymbolSupport,
};
// This function ensures that DbgHelp.dll is loaded in the current process,
// and initializes the gDbgHelpCS critical section that we use to protect calls
// to DbgHelp functions. If DbgHelpInitFlags::WithSymbolSupport is set, we
// additionally call the symbol initialization functions from DbgHelp so that
// symbol-related functions can be used.
//
// This function is thread-safe and reentrancy-safe. In debug and fuzzing
// builds, MOZ_ASSERT and MOZ_CRASH walk the stack to print it before actually
// crashing. Hence *any* MOZ_ASSERT or MOZ_CRASH failure reached from
// Such failures can occur indirectly when we load dbghelp.dll, because we
// override various Microsoft-internal functions that are called upon DLL
// loading.
[[nodiscard]] static bool InitializeDbgHelp(
DbgHelpInitFlags aInitFlags = DbgHelpInitFlags::BasicInit) {
// In the code below, it is only safe to reach MOZ_ASSERT or MOZ_CRASH while
// sInitializationThreadId is set to the current thread id.
static Atomic<DWORD> sInitializationThreadId{0};
DWORD currentThreadId = ::GetCurrentThreadId();
// This code relies on Windows never giving us a current thread ID of zero.
// We make this assumption explicit, by failing if that should ever occur.
if (!currentThreadId) {
return false;
}
if (sInitializationThreadId == currentThreadId) {
// This is a reentrant call and we must abort here.
return false;
}
static const bool sHasInitializedDbgHelp = [currentThreadId]() {
sInitializationThreadId = currentThreadId;
::InitializeCriticalSection(&gDbgHelpCS);
bool dbgHelpLoaded = static_cast<bool>(::LoadLibraryW(L"dbghelp.dll"));
MOZ_ASSERT(dbgHelpLoaded);
sInitializationThreadId = 0;
return dbgHelpLoaded;
}();
// If we don't need symbol initialization, we are done. If we need it, we
// can only proceed if DbgHelp initialization was successful.
if (aInitFlags == DbgHelpInitFlags::BasicInit || !sHasInitializedDbgHelp) {
return sHasInitializedDbgHelp;
}
static const bool sHasInitializedSymbols = [currentThreadId]() {
sInitializationThreadId = currentThreadId;
EnterCriticalSection(&gDbgHelpCS);
SymSetOptions(SYMOPT_LOAD_LINES | SYMOPT_UNDNAME);
bool symbolsInitialized = SymInitialize(GetCurrentProcess(), nullptr, TRUE);
/* XXX At some point we need to arrange to call SymCleanup */
LeaveCriticalSection(&gDbgHelpCS);
if (!symbolsInitialized) {
PrintError("SymInitialize");
}
MOZ_ASSERT(symbolsInitialized);
sInitializationThreadId = 0;
return symbolsInitialized;
}();
return sHasInitializedSymbols;
}
// 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) {
# if defined(_M_IX86)
if (!InitializeDbgHelp()) {
return;
}
# endif
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;
}
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(IMAGE_FILE_MACHINE_I386, ::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.
* 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
// 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;
}
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 (!InitializeDbgHelp(DbgHelpInitFlags::WithSymbolSupport)) {
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
//
// Changes to to OS/Architecture support here should be reflected in
// build/moz.configure/memory.configure
#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.
//
// Changes to to OS/Architecture support here should be reflected in
// build/moz.configure/memory.configure
# 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
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
// - 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);
}
}