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