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/StringRef.h"
  19 #include "llvm/Config/llvm-config.h"
  20 #include "llvm/Support/CommandLine.h"
  21 #include "llvm/Support/ErrorOr.h"
  22 #include "llvm/Support/FileSystem.h"
  23 #include "llvm/Support/FileUtilities.h"
  24 #include "llvm/Support/Format.h"
  25 #include "llvm/Support/FormatVariadic.h"
  26 #include "llvm/Support/ManagedStatic.h"
  27 #include "llvm/Support/MemoryBuffer.h"
  28 #include "llvm/Support/Path.h"
  29 #include "llvm/Support/Program.h"
  30 #include "llvm/Support/StringSaver.h"
  31 #include "llvm/Support/raw_ostream.h"
  32 #include <array>
  33 #include <cmath>
  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 constexpr char EnableSymbolizerMarkupEnv[] = "LLVM_ENABLE_SYMBOLIZER_MARKUP";
  76
  77 // Callbacks to run in signal handler must be lock-free because a signal handler
  78 // could be running as we add new callbacks. We don't add unbounded numbers of
  79 // callbacks, an array is therefore sufficient.
  80 struct CallbackAndCookie {
  81   sys::SignalHandlerCallback Callback;
  82   void *Cookie;
  83   enum class Status { Empty, Initializing, Initialized, Executing };
  84   std::atomic<Status> Flag;
  85 };
  86
  87 static constexpr size_t MaxSignalHandlerCallbacks = 8;
  88
  89 // A global array of CallbackAndCookie may not compile with
  90 // -Werror=global-constructors in c++20 and above
  91 static std::array<CallbackAndCookie, MaxSignalHandlerCallbacks> &
  92 CallBacksToRun() {
  93   static std::array<CallbackAndCookie, MaxSignalHandlerCallbacks> callbacks;
  94   return callbacks;
  95 }
  96
  97 // Signal-safe.
  98 void sys::RunSignalHandlers() {
  99   for (CallbackAndCookie &RunMe : CallBacksToRun()) {
 100     auto Expected = CallbackAndCookie::Status::Initialized;
 101     auto Desired = CallbackAndCookie::Status::Executing;
 102     if (!RunMe.Flag.compare_exchange_strong(Expected, Desired))
 103       continue;
 104     (*RunMe.Callback)(RunMe.Cookie);
 105     RunMe.Callback = nullptr;
 106     RunMe.Cookie = nullptr;
 107     RunMe.Flag.store(CallbackAndCookie::Status::Empty);
 108   }
 109 }
 110
 111 // Signal-safe.
 112 static void insertSignalHandler(sys::SignalHandlerCallback FnPtr,
 113                                 void *Cookie) {
 114   for (CallbackAndCookie &SetMe : CallBacksToRun()) {
 115     auto Expected = CallbackAndCookie::Status::Empty;
 116     auto Desired = CallbackAndCookie::Status::Initializing;
 117     if (!SetMe.Flag.compare_exchange_strong(Expected, Desired))
 118       continue;
 119     SetMe.Callback = FnPtr;
 120     SetMe.Cookie = Cookie;
 121     SetMe.Flag.store(CallbackAndCookie::Status::Initialized);
 122     return;
 123   }
 124   report_fatal_error("too many signal callbacks already registered");
 125 }
 126
 127 static bool findModulesAndOffsets(void **StackTrace, int Depth,
 128                                   const char **Modules, intptr_t *Offsets,
 129                                   const char *MainExecutableName,
 130                                   StringSaver &StrPool);
 131
 132 /// Format a pointer value as hexadecimal. Zero pad it out so its always the
 133 /// same width.
 134 static FormattedNumber format_ptr(void *PC) {
 135   // Each byte is two hex digits plus 2 for the 0x prefix.
 136   unsigned PtrWidth = 2 + 2 * sizeof(void *);
 137   return format_hex((uint64_t)PC, PtrWidth);
 138 }
 139
 140 /// Helper that launches llvm-symbolizer and symbolizes a backtrace.
 141 LLVM_ATTRIBUTE_USED
 142 static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace,
 143                                       int Depth, llvm::raw_ostream &OS) {
 144   if (DisableSymbolicationFlag || getenv(DisableSymbolizationEnv))
 145     return false;
 146
 147   // Don't recursively invoke the llvm-symbolizer binary.
 148   if (Argv0.contains("llvm-symbolizer"))
 149     return false;
 150
 151   // FIXME: Subtract necessary number from StackTrace entries to turn return addresses
 152   // into actual instruction addresses.
 153   // Use llvm-symbolizer tool to symbolize the stack traces. First look for it
 154   // alongside our binary, then in $PATH.
 155   ErrorOr<std::string> LLVMSymbolizerPathOrErr = std::error_code();
 156   if (const char *Path = getenv(LLVMSymbolizerPathEnv)) {
 157     LLVMSymbolizerPathOrErr = sys::findProgramByName(Path);
 158   } else if (!Argv0.empty()) {
 159     StringRef Parent = llvm::sys::path::parent_path(Argv0);
 160     if (!Parent.empty())
 161       LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer", Parent);
 162   }
 163   if (!LLVMSymbolizerPathOrErr)
 164     LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer");
 165   if (!LLVMSymbolizerPathOrErr)
 166     return false;
 167   const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr;
 168
 169   // If we don't know argv0 or the address of main() at this point, try
 170   // to guess it anyway (it's possible on some platforms).
 171   std::string MainExecutableName =
 172       sys::fs::exists(Argv0) ? (std::string)std::string(Argv0)
 173                              : sys::fs::getMainExecutable(nullptr, nullptr);
 174   BumpPtrAllocator Allocator;
 175   StringSaver StrPool(Allocator);
 176   std::vector<const char *> Modules(Depth, nullptr);
 177   std::vector<intptr_t> Offsets(Depth, 0);
 178   if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(),
 179                              MainExecutableName.c_str(), StrPool))
 180     return false;
 181   int InputFD;
 182   SmallString<32> InputFile, OutputFile;
 183   sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile);
 184   sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile);
 185   FileRemover InputRemover(InputFile.c_str());
 186   FileRemover OutputRemover(OutputFile.c_str());
 187
 188   {
 189     raw_fd_ostream Input(InputFD, true);
 190     for (int i = 0; i < Depth; i++) {
 191       if (Modules[i])
 192         Input << Modules[i] << " " << (void*)Offsets[i] << "\n";
 193     }
 194   }
 195
 196   std::optional<StringRef> Redirects[] = {InputFile.str(), OutputFile.str(),
 197                                           StringRef("")};
 198   StringRef Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining",
 199 #ifdef _WIN32
 200                       // Pass --relative-address on Windows so that we don't
 201                       // have to add ImageBase from PE file.
 202                       // FIXME: Make this the default for llvm-symbolizer.
 203                       "--relative-address",
 204 #endif
 205                       "--demangle"};
 206   int RunResult =
 207       sys::ExecuteAndWait(LLVMSymbolizerPath, Args, std::nullopt, Redirects);
 208   if (RunResult != 0)
 209     return false;
 210
 211   // This report format is based on the sanitizer stack trace printer.  See
 212   // sanitizer_stacktrace_printer.cc in compiler-rt.
 213   auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str());
 214   if (!OutputBuf)
 215     return false;
 216   StringRef Output = OutputBuf.get()->getBuffer();
 217   SmallVector<StringRef, 32> Lines;
 218   Output.split(Lines, "\n");
 219   auto CurLine = Lines.begin();
 220   int frame_no = 0;
 221   for (int i = 0; i < Depth; i++) {
 222     auto PrintLineHeader = [&]() {
 223       OS << right_justify(formatv("#{0}", frame_no++).str(),
 224                           std::log10(Depth) + 2)
 225          << ' ' << format_ptr(StackTrace[i]) << ' ';
 226     };
 227     if (!Modules[i]) {
 228       PrintLineHeader();
 229       OS << '\n';
 230       continue;
 231     }
 232     // Read pairs of lines (function name and file/line info) until we
 233     // encounter empty line.
 234     for (;;) {
 235       if (CurLine == Lines.end())
 236         return false;
 237       StringRef FunctionName = *CurLine++;
 238       if (FunctionName.empty())
 239         break;
 240       PrintLineHeader();
 241       if (!FunctionName.starts_with("??"))
 242         OS << FunctionName << ' ';
 243       if (CurLine == Lines.end())
 244         return false;
 245       StringRef FileLineInfo = *CurLine++;
 246       if (!FileLineInfo.starts_with("??"))
 247         OS << FileLineInfo;
 248       else
 249         OS << "(" << Modules[i] << '+' << format_hex(Offsets[i], 0) << ")";
 250       OS << "\n";
 251     }
 252   }
 253   return true;
 254 }
 255
 256 static bool printMarkupContext(raw_ostream &OS, const char *MainExecutableName);
 257
 258 LLVM_ATTRIBUTE_USED
 259 static bool printMarkupStackTrace(StringRef Argv0, void **StackTrace, int Depth,
 260                                   raw_ostream &OS) {
 261   const char *Env = getenv(EnableSymbolizerMarkupEnv);
 262   if (!Env || !*Env)
 263     return false;
 264
 265   std::string MainExecutableName =
 266       sys::fs::exists(Argv0) ? std::string(Argv0)
 267                              : sys::fs::getMainExecutable(nullptr, nullptr);
 268   if (!printMarkupContext(OS, MainExecutableName.c_str()))
 269     return false;
 270   for (int I = 0; I < Depth; I++)
 271     OS << format("{{{bt:%d:%#016x}}}\n", I, StackTrace[I]);
 272   return true;
 273 }
 274
 275 // Include the platform-specific parts of this class.
 276 #ifdef LLVM_ON_UNIX
 277 #include "Unix/Signals.inc"
 278 #endif
 279 #ifdef _WIN32
 280 #include "Windows/Signals.inc"
 281 #endif