llvm/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
  16 #include "DebugOptions.h"
  17
  18 #include "llvm/ADT/STLExtras.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/Config/llvm-config.h"
  21 #include "llvm/Support/CommandLine.h"
  22 #include "llvm/Support/ErrorOr.h"
  23 #include "llvm/Support/FileSystem.h"
  24 #include "llvm/Support/FileUtilities.h"
  25 #include "llvm/Support/Format.h"
  26 #include "llvm/Support/FormatAdapters.h"
  27 #include "llvm/Support/FormatVariadic.h"
  28 #include "llvm/Support/ManagedStatic.h"
  29 #include "llvm/Support/MemoryBuffer.h"
  30 #include "llvm/Support/Mutex.h"
  31 #include "llvm/Support/Program.h"
  32 #include "llvm/Support/StringSaver.h"
  33 #include "llvm/Support/raw_ostream.h"
  34 #include <vector>
  35
  36 //===----------------------------------------------------------------------===//
  37 //=== WARNING: Implementation here must contain only TRULY operating system
  38 //===          independent code.
  39 //===----------------------------------------------------------------------===//
  40
  41 using namespace llvm;
  42
  43 // Use explicit storage to avoid accessing cl::opt in a signal handler.
  44 static bool DisableSymbolicationFlag = false;
  45 static ManagedStatic<std::string> CrashDiagnosticsDirectory;
  46 namespace {
  47 struct CreateDisableSymbolication {
  48   static void *call() {
  49     return new cl::opt<bool, true>(
  50         "disable-symbolication",
  51         cl::desc("Disable symbolizing crash backtraces."),
  52         cl::location(DisableSymbolicationFlag), cl::Hidden);
  53   }
  54 };
  55 struct CreateCrashDiagnosticsDir {
  56   static void *call() {
  57     return new cl::opt<std::string, true>(
  58         "crash-diagnostics-dir", cl::value_desc("directory"),
  59         cl::desc("Directory for crash diagnostic files."),
  60         cl::location(*CrashDiagnosticsDirectory), cl::Hidden);
  61   }
  62 };
  63 } // namespace
  64 void llvm::initSignalsOptions() {
  65   static ManagedStatic<cl::opt<bool, true>, CreateDisableSymbolication>
  66       DisableSymbolication;
  67   static ManagedStatic<cl::opt<std::string, true>, CreateCrashDiagnosticsDir>
  68       CrashDiagnosticsDir;
  69   *DisableSymbolication;
  70   *CrashDiagnosticsDir;
  71 }
  72
  73 constexpr char DisableSymbolizationEnv[] = "LLVM_DISABLE_SYMBOLIZATION";
  74 constexpr char LLVMSymbolizerPathEnv[] = "LLVM_SYMBOLIZER_PATH";
  75
  76 // Callbacks to run in signal handler must be lock-free because a signal handler
  77 // could be running as we add new callbacks. We don't add unbounded numbers of
  78 // callbacks, an array is therefore sufficient.
  79 struct CallbackAndCookie {
  80   sys::SignalHandlerCallback Callback;
  81   void *Cookie;
  82   enum class Status { Empty, Initializing, Initialized, Executing };
  83   std::atomic<Status> Flag;
  84 };
  85 static constexpr size_t MaxSignalHandlerCallbacks = 8;
  86 static CallbackAndCookie CallBacksToRun[MaxSignalHandlerCallbacks];
  87
  88 // Signal-safe.
  89 void sys::RunSignalHandlers() {
  90   for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
  91     auto &RunMe = CallBacksToRun[I];
  92     auto Expected = CallbackAndCookie::Status::Initialized;
  93     auto Desired = CallbackAndCookie::Status::Executing;
  94     if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
  95       continue;
  96     (*RunMe.Callback)(RunMe.Cookie);
  97     RunMe.Callback = nullptr;
  98     RunMe.Cookie = nullptr;
  99     RunMe.Flag.store(CallbackAndCookie::Status::Empty);
 100   }
 101 }
 102
 103 // Signal-safe.
 104 static void insertSignalHandler(sys::SignalHandlerCallback FnPtr,
 105                                 void *Cookie) {
 106   for (size_t I = 0; I < MaxSignalHandlerCallbacks; ++I) {
 107     auto &SetMe = CallBacksToRun[I];
 108     auto Expected = CallbackAndCookie::Status::Empty;
 109     auto Desired = CallbackAndCookie::Status::Initializing;
 110     if (!SetMe.Flag.compare_exchange_strong(Expected, Desired))
 111       continue;
 112     SetMe.Callback = FnPtr;
 113     SetMe.Cookie = Cookie;
 114     SetMe.Flag.store(CallbackAndCookie::Status::Initialized);
 115     return;
 116   }
 117   report_fatal_error("too many signal callbacks already registered");
 118 }
 119
 120 static bool findModulesAndOffsets(void **StackTrace, int Depth,
 121                                   const char **Modules, intptr_t *Offsets,
 122                                   const char *MainExecutableName,
 123                                   StringSaver &StrPool);
 124
 125 /// Format a pointer value as hexadecimal. Zero pad it out so its always the
 126 /// same width.
 127 static FormattedNumber format_ptr(void *PC) {
 128   // Each byte is two hex digits plus 2 for the 0x prefix.
 129   unsigned PtrWidth = 2 + 2 * sizeof(void *);
 130   return format_hex((uint64_t)PC, PtrWidth);
 131 }
 132
 133 /// Helper that launches llvm-symbolizer and symbolizes a backtrace.
 134 LLVM_ATTRIBUTE_USED
 135 static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace,
 136                                       int Depth, llvm::raw_ostream &OS) {
 137   if (DisableSymbolicationFlag || getenv(DisableSymbolizationEnv))
 138     return false;
 139
 140   // Don't recursively invoke the llvm-symbolizer binary.
 141   if (Argv0.find("llvm-symbolizer") != std::string::npos)
 142     return false;
 143
 144   // FIXME: Subtract necessary number from StackTrace entries to turn return addresses
 145   // into actual instruction addresses.
 146   // Use llvm-symbolizer tool to symbolize the stack traces. First look for it
 147   // alongside our binary, then in $PATH.
 148   ErrorOr<std::string> LLVMSymbolizerPathOrErr = std::error_code();
 149   if (const char *Path = getenv(LLVMSymbolizerPathEnv)) {
 150     LLVMSymbolizerPathOrErr = sys::findProgramByName(Path);
 151   } else if (!Argv0.empty()) {
 152     StringRef Parent = llvm::sys::path::parent_path(Argv0);
 153     if (!Parent.empty())
 154       LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer", Parent);
 155   }
 156   if (!LLVMSymbolizerPathOrErr)
 157     LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer");
 158   if (!LLVMSymbolizerPathOrErr)
 159     return false;
 160   const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
 161
 162   // If we don't know argv0 or the address of main() at this point, try
 163   // to guess it anyway (it's possible on some platforms).
 164   std::string MainExecutableName =
 165       sys::fs::exists(Argv0) ? (std::string)std::string(Argv0)
 166                              : sys::fs::getMainExecutable(nullptr, nullptr);
 167   BumpPtrAllocator Allocator;
 168   StringSaver StrPool(Allocator);
 169   std::vector<const char *> Modules(Depth, nullptr);
 170   std::vector<intptr_t> Offsets(Depth, 0);
 171   if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
 172                              MainExecutableName.c_str(), StrPool))
 173     return false;
 174   int InputFD;
 175   SmallString<32> InputFile, OutputFile;
 176   sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
 177   sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
 178   FileRemover InputRemover(InputFile.c_str());
 179   FileRemover OutputRemover(OutputFile.c_str());
 180
 181   {
 182     raw_fd_ostream Input(InputFD, true);
 183     for (int i = 0; i < Depth; i++) {
 184       if (Modules[i])
 185         Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
 186     }
 187   }
 188
 189   Optional<StringRef> Redirects[] = {InputFile.str(), OutputFile.str(),
 190                                      StringRef("")};
 191   StringRef Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
 192 #ifdef _WIN32
 193                       // Pass --relative-address on Windows so that we don't
 194                       // have to add ImageBase from PE file.
 195                       // FIXME: Make this the default for llvm-symbolizer.
 196                       "--relative-address",
 197 #endif
 198                       "--demangle"};
 199   int RunResult =
 200       sys::ExecuteAndWait(LLVMSymbolizerPath, Args, None, Redirects);
 201   if (RunResult != 0)
 202     return false;
 203
 204   // This report format is based on the sanitizer stack trace printer.  See
 205   // sanitizer_stacktrace_printer.cc in compiler-rt.
 206   auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
 207   if (!OutputBuf)
 208     return false;
 209   StringRef Output = OutputBuf.get()->getBuffer();
 210   SmallVector<StringRef, 32> Lines;
 211   Output.split(Lines, "\n");
 212   auto CurLine = Lines.begin();
 213   int frame_no = 0;
 214   for (int i = 0; i < Depth; i++) {
 215     auto PrintLineHeader = [&]() {
 216       OS << right_justify(formatv("#{0}", frame_no++).str(),
 217                           std::log10(Depth) + 2)
 218          << ' ' << format_ptr(StackTrace[i]) << ' ';
 219     };
 220     if (!Modules[i]) {
 221       PrintLineHeader();
 222       OS << '\n';
 223       continue;
 224     }
 225     // Read pairs of lines (function name and file/line info) until we
 226     // encounter empty line.
 227     for (;;) {
 228       if (CurLine == Lines.end())
 229         return false;
 230       StringRef FunctionName = *CurLine++;
 231       if (FunctionName.empty())
 232         break;
 233       PrintLineHeader();
 234       if (!FunctionName.startswith("??"))
 235         OS << FunctionName << ' ';
 236       if (CurLine == Lines.end())
 237         return false;
 238       StringRef FileLineInfo = *CurLine++;
 239       if (!FileLineInfo.startswith("??"))
 240         OS << FileLineInfo;
 241       else
 242         OS << "(" << Modules[i] << '+' << format_hex(Offsets[i], 0) << ")";
 243       OS << "\n";
 244     }
 245   }
 246   return true;
 247 }
 248
 249 // Include the platform-specific parts of this class.
 250 #ifdef LLVM_ON_UNIX
 251 #include "Unix/Signals.inc"
 252 #endif
 253 #ifdef _WIN32
 254 #include "Windows/Signals.inc"
 255 #endif