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