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//===- Signals.cpp - Signal Handling support --------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines some helpful functions for dealing with the possibility of
// Unix signals occurring while your program is running.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/Signals.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/FileUtilities.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/FormatAdapters.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/raw_ostream.h"
#include <vector>
//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only TRULY operating system
//=== independent code.
//===----------------------------------------------------------------------===//
using namespace llvm;
// Use explicit storage to avoid accessing cl::opt in a signal handler.
static bool DisableSymbolicationFlag = false;
static cl::opt<bool, true>
DisableSymbolication("disable-symbolication",
cl::desc("Disable symbolizing crash backtraces."),
cl::location(DisableSymbolicationFlag), cl::Hidden);
constexpr char DisableSymbolizationEnv[] = "LLVM_DISABLE_SYMBOLIZATION";
constexpr char LLVMSymbolizerPathEnv[] = "LLVM_SYMBOLIZER_PATH";
// Callbacks to run in signal handler must be lock-free because a signal handler
// could be running as we add new callbacks. We don't add unbounded numbers of
// callbacks, an array is therefore sufficient.
struct CallbackAndCookie {
sys::SignalHandlerCallback Callback;
void *Cookie;
enum class Status { Empty, Initializing, Initialized, Executing };
std::atomic<Status> Flag;
};
static constexpr size_t MaxSignalHandlerCallbacks = 8;
static CallbackAndCookie CallBacksToRun[MaxSignalHandlerCallbacks];
// Signal-safe.
void sys::RunSignalHandlers() {
for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
auto &RunMe = CallBacksToRun[I];
auto Expected = CallbackAndCookie::Status::Initialized;
auto Desired = CallbackAndCookie::Status::Executing;
if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
continue;
(*RunMe.Callback)(RunMe.Cookie);
RunMe.Callback = nullptr;
RunMe.Cookie = nullptr;
RunMe.Flag.store(CallbackAndCookie::Status::Empty);
}
}
// Signal-safe.
static void insertSignalHandler(sys::SignalHandlerCallback FnPtr,
void *Cookie) {
for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
auto &SetMe = CallBacksToRun[I];
auto Expected = CallbackAndCookie::Status::Empty;
auto Desired = CallbackAndCookie::Status::Initializing;
if (!SetMe.Flag.compare_exchange_strong(Expected, Desired))
continue;
SetMe.Callback = FnPtr;
SetMe.Cookie = Cookie;
SetMe.Flag.store(CallbackAndCookie::Status::Initialized);
return;
}
report_fatal_error("too many signal callbacks already registered");
}
static bool findModulesAndOffsets(void **StackTrace, int Depth,
const char **Modules, intptr_t *Offsets,
const char *MainExecutableName,
StringSaver &StrPool);
/// Format a pointer value as hexadecimal. Zero pad it out so its always the
/// same width.
static FormattedNumber format_ptr(void *PC) {
// Each byte is two hex digits plus 2 for the 0x prefix.
unsigned PtrWidth = 2 + 2 * sizeof(void *);
return format_hex((uint64_t)PC, PtrWidth);
}
/// Helper that launches llvm-symbolizer and symbolizes a backtrace.
LLVM_ATTRIBUTE_USED
static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace,
int Depth, llvm::raw_ostream &OS) {
if (DisableSymbolicationFlag || getenv(DisableSymbolizationEnv))
return false;
// Don't recursively invoke the llvm-symbolizer binary.
if (Argv0.find("llvm-symbolizer") != std::string::npos)
return false;
// FIXME: Subtract necessary number from StackTrace entries to turn return addresses
// into actual instruction addresses.
// Use llvm-symbolizer tool to symbolize the stack traces. First look for it
// alongside our binary, then in $PATH.
ErrorOr<std::string> LLVMSymbolizerPathOrErr = std::error_code();
if (const char *Path = getenv(LLVMSymbolizerPathEnv)) {
LLVMSymbolizerPathOrErr = sys::findProgramByName(Path);
} else if (!Argv0.empty()) {
StringRef Parent = llvm::sys::path::parent_path(Argv0);
if (!Parent.empty())
LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer", Parent);
}
if (!LLVMSymbolizerPathOrErr)
LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer");
if (!LLVMSymbolizerPathOrErr)
return false;
const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
// If we don't know argv0 or the address of main() at this point, try
// to guess it anyway (it's possible on some platforms).
std::string MainExecutableName =
sys::fs::exists(Argv0) ? (std::string)std::string(Argv0)
: sys::fs::getMainExecutable(nullptr, nullptr);
BumpPtrAllocator Allocator;
StringSaver StrPool(Allocator);
std::vector<const char *> Modules(Depth, nullptr);
std::vector<intptr_t> Offsets(Depth, 0);
if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
MainExecutableName.c_str(), StrPool))
return false;
int InputFD;
SmallString<32> InputFile, OutputFile;
sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
FileRemover InputRemover(InputFile.c_str());
FileRemover OutputRemover(OutputFile.c_str());
{
raw_fd_ostream Input(InputFD, true);
for (int i = 0; i < Depth; i++) {
if (Modules[i])
Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
}
}
Optional<StringRef> Redirects[] = {StringRef(InputFile),
StringRef(OutputFile), StringRef("")};
StringRef Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
#ifdef _WIN32
// Pass --relative-address on Windows so that we don't
// have to add ImageBase from PE file.
// FIXME: Make this the default for llvm-symbolizer.
"--relative-address",
#endif
"--demangle"};
int RunResult =
sys::ExecuteAndWait(LLVMSymbolizerPath, Args, None, Redirects);
if (RunResult != 0)
return false;
// This report format is based on the sanitizer stack trace printer. See
// sanitizer_stacktrace_printer.cc in compiler-rt.
auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
if (!OutputBuf)
return false;
StringRef Output = OutputBuf.get()->getBuffer();
SmallVector<StringRef, 32> Lines;
Output.split(Lines, "\n");
auto CurLine = Lines.begin();
int frame_no = 0;
for (int i = 0; i < Depth; i++) {
auto PrintLineHeader = [&]() {
OS << right_justify(formatv("#{0}", frame_no++).str(),
std::log10(Depth) + 2)
<< ' ' << format_ptr(StackTrace[i]) << ' ';
};
if (!Modules[i]) {
PrintLineHeader();
OS << '\n';
continue;
}
// Read pairs of lines (function name and file/line info) until we
// encounter empty line.
for (;;) {
if (CurLine == Lines.end())
return false;
StringRef FunctionName = *CurLine++;
if (FunctionName.empty())
break;
PrintLineHeader();
if (!FunctionName.startswith("??"))
OS << FunctionName << ' ';
if (CurLine == Lines.end())
return false;
StringRef FileLineInfo = *CurLine++;
if (!FileLineInfo.startswith("??"))
OS << FileLineInfo;
else
OS << "(" << Modules[i] << '+' << format_hex(Offsets[i], 0) << ")";
OS << "\n";
}
}
return true;
}
// Include the platform-specific parts of this class.
#ifdef LLVM_ON_UNIX
#include "Unix/Signals.inc"
#endif
#ifdef _WIN32
#include "Windows/Signals.inc"
#endif
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