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