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 (CallbackAndCookie &RunMe : CallBacksToRun) { 91 auto Expected = CallbackAndCookie::Status::Initialized; 92 auto Desired = CallbackAndCookie::Status::Executing; 93 if (!RunMe.Flag.compare_exchange_strong(Expected, Desired)) 94 continue; 95 (*RunMe.Callback)(RunMe.Cookie); 96 RunMe.Callback = nullptr; 97 RunMe.Cookie = nullptr; 98 RunMe.Flag.store(CallbackAndCookie::Status::Empty); 99 } 100 } 101 102 // Signal-safe. 103 static void insertSignalHandler(sys::SignalHandlerCallback FnPtr, 104 void *Cookie) { 105 for (CallbackAndCookie &SetMe : CallBacksToRun) { 106 auto Expected = CallbackAndCookie::Status::Empty; 107 auto Desired = CallbackAndCookie::Status::Initializing; 108 if (!SetMe.Flag.compare_exchange_strong(Expected, Desired)) 109 continue; 110 SetMe.Callback = FnPtr; 111 SetMe.Cookie = Cookie; 112 SetMe.Flag.store(CallbackAndCookie::Status::Initialized); 113 return; 114 } 115 report_fatal_error("too many signal callbacks already registered"); 116 } 117 118 static bool findModulesAndOffsets(void **StackTrace, int Depth, 119 const char **Modules, intptr_t *Offsets, 120 const char *MainExecutableName, 121 StringSaver &StrPool); 122 123 /// Format a pointer value as hexadecimal. Zero pad it out so its always the 124 /// same width. 125 static FormattedNumber format_ptr(void *PC) { 126 // Each byte is two hex digits plus 2 for the 0x prefix. 127 unsigned PtrWidth = 2 + 2 * sizeof(void *); 128 return format_hex((uint64_t)PC, PtrWidth); 129 } 130 131 /// Helper that launches llvm-symbolizer and symbolizes a backtrace. 132 LLVM_ATTRIBUTE_USED 133 static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace, 134 int Depth, llvm::raw_ostream &OS) { 135 if (DisableSymbolicationFlag || getenv(DisableSymbolizationEnv)) 136 return false; 137 138 // Don't recursively invoke the llvm-symbolizer binary. 139 if (Argv0.find("llvm-symbolizer") != std::string::npos) 140 return false; 141 142 // FIXME: Subtract necessary number from StackTrace entries to turn return addresses 143 // into actual instruction addresses. 144 // Use llvm-symbolizer tool to symbolize the stack traces. First look for it 145 // alongside our binary, then in $PATH. 146 ErrorOr<std::string> LLVMSymbolizerPathOrErr = std::error_code(); 147 if (const char *Path = getenv(LLVMSymbolizerPathEnv)) { 148 LLVMSymbolizerPathOrErr = sys::findProgramByName(Path); 149 } else if (!Argv0.empty()) { 150 StringRef Parent = llvm::sys::path::parent_path(Argv0); 151 if (!Parent.empty()) 152 LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer", Parent); 153 } 154 if (!LLVMSymbolizerPathOrErr) 155 LLVMSymbolizerPathOrErr = sys::findProgramByName("llvm-symbolizer"); 156 if (!LLVMSymbolizerPathOrErr) 157 return false; 158 const std::string &LLVMSymbolizerPath = *LLVMSymbolizerPathOrErr; 159 160 // If we don't know argv0 or the address of main() at this point, try 161 // to guess it anyway (it's possible on some platforms). 162 std::string MainExecutableName = 163 sys::fs::exists(Argv0) ? (std::string)std::string(Argv0) 164 : sys::fs::getMainExecutable(nullptr, nullptr); 165 BumpPtrAllocator Allocator; 166 StringSaver StrPool(Allocator); 167 std::vector<const char *> Modules(Depth, nullptr); 168 std::vector<intptr_t> Offsets(Depth, 0); 169 if (!findModulesAndOffsets(StackTrace, Depth, Modules.data(), Offsets.data(), 170 MainExecutableName.c_str(), StrPool)) 171 return false; 172 int InputFD; 173 SmallString<32> InputFile, OutputFile; 174 sys::fs::createTemporaryFile("symbolizer-input", "", InputFD, InputFile); 175 sys::fs::createTemporaryFile("symbolizer-output", "", OutputFile); 176 FileRemover InputRemover(InputFile.c_str()); 177 FileRemover OutputRemover(OutputFile.c_str()); 178 179 { 180 raw_fd_ostream Input(InputFD, true); 181 for (int i = 0; i < Depth; i++) { 182 if (Modules[i]) 183 Input << Modules[i] << " " << (void*)Offsets[i] << "\n"; 184 } 185 } 186 187 Optional<StringRef> Redirects[] = {InputFile.str(), OutputFile.str(), 188 StringRef("")}; 189 StringRef Args[] = {"llvm-symbolizer", "--functions=linkage", "--inlining", 190 #ifdef _WIN32 191 // Pass --relative-address on Windows so that we don't 192 // have to add ImageBase from PE file. 193 // FIXME: Make this the default for llvm-symbolizer. 194 "--relative-address", 195 #endif 196 "--demangle"}; 197 int RunResult = 198 sys::ExecuteAndWait(LLVMSymbolizerPath, Args, None, Redirects); 199 if (RunResult != 0) 200 return false; 201 202 // This report format is based on the sanitizer stack trace printer. See 203 // sanitizer_stacktrace_printer.cc in compiler-rt. 204 auto OutputBuf = MemoryBuffer::getFile(OutputFile.c_str()); 205 if (!OutputBuf) 206 return false; 207 StringRef Output = OutputBuf.get()->getBuffer(); 208 SmallVector<StringRef, 32> Lines; 209 Output.split(Lines, "\n"); 210 auto CurLine = Lines.begin(); 211 int frame_no = 0; 212 for (int i = 0; i < Depth; i++) { 213 auto PrintLineHeader = [&]() { 214 OS << right_justify(formatv("#{0}", frame_no++).str(), 215 std::log10(Depth) + 2) 216 << ' ' << format_ptr(StackTrace[i]) << ' '; 217 }; 218 if (!Modules[i]) { 219 PrintLineHeader(); 220 OS << '\n'; 221 continue; 222 } 223 // Read pairs of lines (function name and file/line info) until we 224 // encounter empty line. 225 for (;;) { 226 if (CurLine == Lines.end()) 227 return false; 228 StringRef FunctionName = *CurLine++; 229 if (FunctionName.empty()) 230 break; 231 PrintLineHeader(); 232 if (!FunctionName.startswith("??")) 233 OS << FunctionName << ' '; 234 if (CurLine == Lines.end()) 235 return false; 236 StringRef FileLineInfo = *CurLine++; 237 if (!FileLineInfo.startswith("??")) 238 OS << FileLineInfo; 239 else 240 OS << "(" << Modules[i] << '+' << format_hex(Offsets[i], 0) << ")"; 241 OS << "\n"; 242 } 243 } 244 return true; 245 } 246 247 // Include the platform-specific parts of this class. 248 #ifdef LLVM_ON_UNIX 249 #include "Unix/Signals.inc" 250 #endif 251 #ifdef _WIN32 252 #include "Windows/Signals.inc" 253 #endif 254