lib/Support/Signals.cpp

   1 //===- Signals.cpp - Signal Handling support --------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines some helpful functions for dealing with the possibility of
  10 // Unix signals occurring while your program is running.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/Signals.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/Config/llvm-config.h"
  18 #include "llvm/Support/ErrorOr.h"
  19 #include "llvm/Support/FileSystem.h"
  20 #include "llvm/Support/FileUtilities.h"
  21 #include "llvm/Support/Format.h"
  22 #include "llvm/Support/FormatVariadic.h"
  23 #include "llvm/Support/FormatAdapters.h"
  24 #include "llvm/Support/ManagedStatic.h"
  25 #include "llvm/Support/MemoryBuffer.h"
  26 #include "llvm/Support/Mutex.h"
  27 #include "llvm/Support/Program.h"
  28 #include "llvm/Support/StringSaver.h"
  29 #include "llvm/Support/raw_ostream.h"
  30 #include "llvm/Support/Options.h"
  31 #include <vector>
  32
  33 //===----------------------------------------------------------------------===//
  34 //=== WARNING: Implementation here must contain only TRULY operating system
  35 //===          independent code.
  36 //===----------------------------------------------------------------------===//
  37
  38 using namespace llvm;
  39
  40 // Use explicit storage to avoid accessing cl::opt in a signal handler.
  41 static bool DisableSymbolicationFlag = false;
  42 static cl::opt<bool, true>
  43     DisableSymbolication("disable-symbolication",
  44                          cl::desc("Disable symbolizing crash backtraces."),
  45                          cl::location(DisableSymbolicationFlag), cl::Hidden);
  46
  47 // Callbacks to run in signal handler must be lock-free because a signal handler
  48 // could be running as we add new callbacks. We don't add unbounded numbers of
  49 // callbacks, an array is therefore sufficient.
  50 struct CallbackAndCookie {
  51   sys::SignalHandlerCallback Callback;
  52   void *Cookie;
  53   enum class Status { Empty, Initializing, Initialized, Executing };
  54   std::atomic<Status> Flag;
  55 };
  56 static constexpr size_t MaxSignalHandlerCallbacks = 8;
  57 static CallbackAndCookie CallBacksToRun[MaxSignalHandlerCallbacks];
  58
  59 // Signal-safe.
  60 void sys::RunSignalHandlers() {
  61   for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
  62     auto &RunMe = CallBacksToRun[I];
  63     auto Expected = CallbackAndCookie::Status::Initialized;
  64     auto Desired = CallbackAndCookie::Status::Executing;
  65     if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
  66       continue;
  67     (*RunMe.Callback)(RunMe.Cookie);
  68     RunMe.Callback = nullptr;
  69     RunMe.Cookie = nullptr;
  70     RunMe.Flag.store(CallbackAndCookie::Status::Empty);
  71   }
  72 }
  73
  74 // Signal-safe.
  75 static void insertSignalHandler(sys::SignalHandlerCallback FnPtr,
  76                                 void *Cookie) {
  77   for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
  78     auto &SetMe = CallBacksToRun[I];
  79     auto Expected = CallbackAndCookie::Status::Empty;
  80     auto Desired = CallbackAndCookie::Status::Initializing;
  81     if (!SetMe.Flag.compare_exchange_strong(Expected, Desired))
  82       continue;
  83     SetMe.Callback = FnPtr;
  84     SetMe.Cookie = Cookie;
  85     SetMe.Flag.store(CallbackAndCookie::Status::Initialized);
  86     return;
  87   }
  88   report_fatal_error("too many signal callbacks already registered");
  89 }
  90
  91 static bool findModulesAndOffsets(void **StackTrace, int Depth,
  92                                   const char **Modules, intptr_t *Offsets,
  93                                   const char *MainExecutableName,
  94                                   StringSaver &StrPool);
  95
  96 /// Format a pointer value as hexadecimal. Zero pad it out so its always the
  97 /// same width.
  98 static FormattedNumber format_ptr(void *PC) {
  99   // Each byte is two hex digits plus 2 for the 0x prefix.
 100   unsigned PtrWidth = 2 + 2 * sizeof(void *);
 101   return format_hex((uint64_t)PC, PtrWidth);
 102 }
 103
 104 /// Helper that launches llvm-symbolizer and symbolizes a backtrace.
 105 LLVM_ATTRIBUTE_USED
 106 static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace,
 107                                       int Depth, llvm::raw_ostream &OS) {
 108   if (DisableSymbolicationFlag)
 109     return false;
 110
 111   // Don't recursively invoke the llvm-symbolizer binary.
 112   if (Argv0.find("llvm-symbolizer") != std::string::npos)
 113     return false;
 114
 115   // FIXME: Subtract necessary number from StackTrace entries to turn return addresses
 116   // into actual instruction addresses.
 117   // Use llvm-symbolizer tool to symbolize the stack traces. First look for it
 118   // alongside our binary, then in $PATH.
 119   ErrorOr<std::string> LLVMSymbolizerPathOrErr = std::error_code();
 120   if (!Argv0.empty()) {
 121     StringRef Parent = llvm::sys::path::parent_path(Argv0);
 122     if (!Parent.empty())
 123       LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer", Parent);
 124   }
 125   if (!LLVMSymbolizerPathOrErr)
 126     LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer");
 127   if (!LLVMSymbolizerPathOrErr)
 128     return false;
 129   const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
 130
 131   // If we don't know argv0 or the address of main() at this point, try
 132   // to guess it anyway (it's possible on some platforms).
 133   std::string MainExecutableName =
 134       sys::fs::exists(Argv0) ? (std::string)Argv0
 135                              : sys::fs::getMainExecutable(nullptr, nullptr);
 136   BumpPtrAllocator Allocator;
 137   StringSaver StrPool(Allocator);
 138   std::vector<const char *> Modules(Depth, nullptr);
 139   std::vector<intptr_t> Offsets(Depth, 0);
 140   if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
 141                              MainExecutableName.c_str(), StrPool))
 142     return false;
 143   int InputFD;
 144   SmallString<32> InputFile, OutputFile;
 145   sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
 146   sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
 147   FileRemover InputRemover(InputFile.c_str());
 148   FileRemover OutputRemover(OutputFile.c_str());
 149
 150   {
 151     raw_fd_ostream Input(InputFD, true);
 152     for (int i = 0; i < Depth; i++) {
 153       if (Modules[i])
 154         Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
 155     }
 156   }
 157
 158   Optional<StringRef> Redirects[] = {StringRef(InputFile),
 159                                      StringRef(OutputFile), StringRef("")};
 160   StringRef Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
 161 #ifdef _WIN32
 162                       // Pass --relative-address on Windows so that we don't
 163                       // have to add ImageBase from PE file.
 164                       // FIXME: Make this the default for llvm-symbolizer.
 165                       "--relative-address",
 166 #endif
 167                       "--demangle"};
 168   int RunResult =
 169       sys::ExecuteAndWait(LLVMSymbolizerPath, Args, None, Redirects);
 170   if (RunResult != 0)
 171     return false;
 172
 173   // This report format is based on the sanitizer stack trace printer.  See
 174   // sanitizer_stacktrace_printer.cc in compiler-rt.
 175   auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
 176   if (!OutputBuf)
 177     return false;
 178   StringRef Output = OutputBuf.get()->getBuffer();
 179   SmallVector<StringRef, 32> Lines;
 180   Output.split(Lines, "\n");
 181   auto CurLine = Lines.begin();
 182   int frame_no = 0;
 183   for (int i = 0; i < Depth; i++) {
 184     auto PrintLineHeader = [&]() {
 185       OS << right_justify(formatv("#{0}", frame_no++).str(),
 186                           std::log10(Depth) + 2)
 187          << ' ' << format_ptr(StackTrace[i]) << ' ';
 188     };
 189     if (!Modules[i]) {
 190       PrintLineHeader();
 191       OS << '\n';
 192       continue;
 193     }
 194     // Read pairs of lines (function name and file/line info) until we
 195     // encounter empty line.
 196     for (;;) {
 197       if (CurLine == Lines.end())
 198         return false;
 199       StringRef FunctionName = *CurLine++;
 200       if (FunctionName.empty())
 201         break;
 202       PrintLineHeader();
 203       if (!FunctionName.startswith("??"))
 204         OS << FunctionName << ' ';
 205       if (CurLine == Lines.end())
 206         return false;
 207       StringRef FileLineInfo = *CurLine++;
 208       if (!FileLineInfo.startswith("??"))
 209         OS << FileLineInfo;
 210       else
 211         OS << "(" << Modules[i] << '+' << format_hex(Offsets[i], 0) << ")";
 212       OS << "\n";
 213     }
 214   }
 215   return true;
 216 }
 217
 218 // Include the platform-specific parts of this class.
 219 #ifdef LLVM_ON_UNIX
 220 #include "Unix/Signals.inc"
 221 #endif
 222 #ifdef _WIN32
 223 #include "Windows/Signals.inc"
 224 #endif