1//===- Signals.cpp - Generic Unix Signals Implementation -----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines some helpful functions for dealing with the possibility of 11// Unix signals occurring while your program is running. 12// 13//===----------------------------------------------------------------------===// 14 15#include "Unix.h" 16#include "llvm/ADT/STLExtras.h" 17#include "llvm/Support/Mutex.h" 18#include <string> 19#include <vector> 20#include <algorithm> 21#if HAVE_EXECINFO_H 22# include <execinfo.h> // For backtrace(). 23#endif 24#if HAVE_SIGNAL_H 25#include <signal.h> 26#endif 27#if HAVE_SYS_STAT_H 28#include <sys/stat.h> 29#endif 30#if HAVE_DLFCN_H && HAVE_CXXABI_H && __GNUG__ 31#include <dlfcn.h> 32#include <cxxabi.h> 33#endif 34#if HAVE_MACH_MACH_H 35#include <mach/mach.h> 36#endif 37 38using namespace llvm; 39 40static RETSIGTYPE SignalHandler(int Sig); // defined below. 41 42static SmartMutex<true> SignalsMutex; 43 44/// InterruptFunction - The function to call if ctrl-c is pressed. 45static void (*InterruptFunction)() = 0; 46 47static std::vector<std::string> FilesToRemove; 48static std::vector<std::pair<void(*)(void*), void*> > CallBacksToRun; 49 50// IntSigs - Signals that may interrupt the program at any time. 51static const int IntSigs[] = { 52 SIGHUP, SIGINT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2 53}; 54static const int *const IntSigsEnd = 55 IntSigs + sizeof(IntSigs) / sizeof(IntSigs[0]); 56 57// KillSigs - Signals that are synchronous with the program that will cause it 58// to die. 59static const int KillSigs[] = { 60 SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV 61#ifdef SIGSYS 62 , SIGSYS 63#endif 64#ifdef SIGXCPU 65 , SIGXCPU 66#endif 67#ifdef SIGXFSZ 68 , SIGXFSZ 69#endif 70#ifdef SIGEMT 71 , SIGEMT 72#endif 73}; 74static const int *const KillSigsEnd = 75 KillSigs + sizeof(KillSigs) / sizeof(KillSigs[0]); 76 77static unsigned NumRegisteredSignals = 0; 78static struct { 79 struct sigaction SA; 80 int SigNo; 81} RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])]; 82 83 84static void RegisterHandler(int Signal) { 85 assert(NumRegisteredSignals < 86 sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) && 87 "Out of space for signal handlers!"); 88 89 struct sigaction NewHandler; 90 91 NewHandler.sa_handler = SignalHandler; 92 NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND; 93 sigemptyset(&NewHandler.sa_mask); 94 95 // Install the new handler, save the old one in RegisteredSignalInfo. 96 sigaction(Signal, &NewHandler, 97 &RegisteredSignalInfo[NumRegisteredSignals].SA); 98 RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal; 99 ++NumRegisteredSignals; 100} 101 102static void RegisterHandlers() { 103 // If the handlers are already registered, we're done. 104 if (NumRegisteredSignals != 0) return; 105 106 std::for_each(IntSigs, IntSigsEnd, RegisterHandler); 107 std::for_each(KillSigs, KillSigsEnd, RegisterHandler); 108} 109 110static void UnregisterHandlers() { 111 // Restore all of the signal handlers to how they were before we showed up. 112 for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i) 113 sigaction(RegisteredSignalInfo[i].SigNo, 114 &RegisteredSignalInfo[i].SA, 0); 115 NumRegisteredSignals = 0; 116} 117 118 119/// RemoveFilesToRemove - Process the FilesToRemove list. This function 120/// should be called with the SignalsMutex lock held. 121/// NB: This must be an async signal safe function. It cannot allocate or free 122/// memory, even in debug builds. 123static void RemoveFilesToRemove() { 124 // Note: avoid iterators in case of debug iterators that allocate or release 125 // memory. 126 for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) { 127 // Note that we don't want to use any external code here, and we don't care 128 // about errors. We're going to try as hard as we can as often as we need 129 // to to make these files go away. If these aren't files, too bad. 130 // 131 // We do however rely on a std::string implementation for which repeated 132 // calls to 'c_str()' don't allocate memory. We pre-call 'c_str()' on all 133 // of these strings to try to ensure this is safe. 134 unlink(FilesToRemove[i].c_str()); 135 } 136} 137 138// SignalHandler - The signal handler that runs. 139static RETSIGTYPE SignalHandler(int Sig) { 140 // Restore the signal behavior to default, so that the program actually 141 // crashes when we return and the signal reissues. This also ensures that if 142 // we crash in our signal handler that the program will terminate immediately 143 // instead of recursing in the signal handler. 144 UnregisterHandlers(); 145 146 // Unmask all potentially blocked kill signals. 147 sigset_t SigMask; 148 sigfillset(&SigMask); 149 sigprocmask(SIG_UNBLOCK, &SigMask, 0); 150 151 SignalsMutex.acquire(); 152 RemoveFilesToRemove(); 153 154 if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) { 155 if (InterruptFunction) { 156 void (*IF)() = InterruptFunction; 157 SignalsMutex.release(); 158 InterruptFunction = 0; 159 IF(); // run the interrupt function. 160 return; 161 } 162 163 SignalsMutex.release(); 164 raise(Sig); // Execute the default handler. 165 return; 166 } 167 168 SignalsMutex.release(); 169 170 // Otherwise if it is a fault (like SEGV) run any handler. 171 for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i) 172 CallBacksToRun[i].first(CallBacksToRun[i].second); 173} 174 175void llvm::sys::RunInterruptHandlers() { 176 SignalsMutex.acquire(); 177 RemoveFilesToRemove(); 178 SignalsMutex.release(); 179} 180 181void llvm::sys::SetInterruptFunction(void (*IF)()) { 182 SignalsMutex.acquire(); 183 InterruptFunction = IF; 184 SignalsMutex.release(); 185 RegisterHandlers(); 186} 187 188// RemoveFileOnSignal - The public API 189bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename, 190 std::string* ErrMsg) { 191 SignalsMutex.acquire(); 192 std::string *OldPtr = FilesToRemove.empty() ? 0 : &FilesToRemove[0]; 193 FilesToRemove.push_back(Filename.str()); 194 195 // We want to call 'c_str()' on every std::string in this vector so that if 196 // the underlying implementation requires a re-allocation, it happens here 197 // rather than inside of the signal handler. If we see the vector grow, we 198 // have to call it on every entry. If it remains in place, we only need to 199 // call it on the latest one. 200 if (OldPtr == &FilesToRemove[0]) 201 FilesToRemove.back().c_str(); 202 else 203 for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) 204 FilesToRemove[i].c_str(); 205 206 SignalsMutex.release(); 207 208 RegisterHandlers(); 209 return false; 210} 211 212// DontRemoveFileOnSignal - The public API 213void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) { 214 SignalsMutex.acquire(); 215 std::vector<std::string>::reverse_iterator RI = 216 std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename.str()); 217 std::vector<std::string>::iterator I = FilesToRemove.end(); 218 if (RI != FilesToRemove.rend()) 219 I = FilesToRemove.erase(RI.base()-1); 220 221 // We need to call c_str() on every element which would have been moved by 222 // the erase. These elements, in a C++98 implementation where c_str() 223 // requires a reallocation on the first call may have had the call to c_str() 224 // made on insertion become invalid by being copied down an element. 225 for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I) 226 I->c_str(); 227 228 SignalsMutex.release(); 229} 230 231/// AddSignalHandler - Add a function to be called when a signal is delivered 232/// to the process. The handler can have a cookie passed to it to identify 233/// what instance of the handler it is. 234void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) { 235 CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie)); 236 RegisterHandlers(); 237} 238 239 240// PrintStackTrace - In the case of a program crash or fault, print out a stack 241// trace so that the user has an indication of why and where we died. 242// 243// On glibc systems we have the 'backtrace' function, which works nicely, but 244// doesn't demangle symbols. 245static void PrintStackTrace(void *) { 246#ifdef HAVE_BACKTRACE 247 static void* StackTrace[256]; 248 // Use backtrace() to output a backtrace on Linux systems with glibc. 249 int depth = backtrace(StackTrace, 250 static_cast<int>(array_lengthof(StackTrace))); 251#if HAVE_DLFCN_H && HAVE_CXXABI_H && __GNUG__ 252 int width = 0; 253 for (int i = 0; i < depth; ++i) { 254 Dl_info dlinfo; 255 dladdr(StackTrace[i], &dlinfo); 256 const char* name = strrchr(dlinfo.dli_fname, '/'); 257 258 int nwidth; 259 if (name == NULL) nwidth = strlen(dlinfo.dli_fname); 260 else nwidth = strlen(name) - 1; 261 262 if (nwidth > width) width = nwidth; 263 } 264 265 for (int i = 0; i < depth; ++i) { 266 Dl_info dlinfo; 267 dladdr(StackTrace[i], &dlinfo); 268 269 fprintf(stderr, "%-2d", i); 270 271 const char* name = strrchr(dlinfo.dli_fname, '/'); 272 if (name == NULL) fprintf(stderr, " %-*s", width, dlinfo.dli_fname); 273 else fprintf(stderr, " %-*s", width, name+1); 274 275 fprintf(stderr, " %#0*lx", 276 (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]); 277 278 if (dlinfo.dli_sname != NULL) { 279 int res; 280 fputc(' ', stderr); 281 char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res); 282 if (d == NULL) fputs(dlinfo.dli_sname, stderr); 283 else fputs(d, stderr); 284 free(d); 285 286 fprintf(stderr, " + %tu",(char*)StackTrace[i]-(char*)dlinfo.dli_saddr); 287 } 288 fputc('\n', stderr); 289 } 290#else 291 backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO); 292#endif 293#endif 294} 295 296/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or 297/// SIGSEGV) is delivered to the process, print a stack trace and then exit. 298void llvm::sys::PrintStackTraceOnErrorSignal() { 299 AddSignalHandler(PrintStackTrace, 0); 300 301#if defined(__APPLE__) && !defined(ANDROID) 302 // Environment variable to disable any kind of crash dialog. 303 if (getenv("LLVM_DISABLE_CRASH_REPORT")) { 304 mach_port_t self = mach_task_self(); 305 306 exception_mask_t mask = EXC_MASK_CRASH; 307 308 kern_return_t ret = task_set_exception_ports(self, 309 mask, 310 MACH_PORT_NULL, 311 EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES, 312 THREAD_STATE_NONE); 313 (void)ret; 314 } 315#endif 316} 317 318 319/***/ 320 321// On Darwin, raise sends a signal to the main thread instead of the current 322// thread. This has the unfortunate effect that assert() and abort() will end up 323// bypassing our crash recovery attempts. We work around this for anything in 324// the same linkage unit by just defining our own versions of the assert handler 325// and abort. 326 327#if defined(__APPLE__) && !defined(ANDROID) 328 329#include <signal.h> 330#include <pthread.h> 331 332int raise(int sig) { 333 return pthread_kill(pthread_self(), sig); 334} 335 336void __assert_rtn(const char *func, 337 const char *file, 338 int line, 339 const char *expr) { 340 if (func) 341 fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n", 342 expr, func, file, line); 343 else 344 fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n", 345 expr, file, line); 346 abort(); 347} 348 349void abort() { 350 raise(SIGABRT); 351 usleep(1000); 352 __builtin_trap(); 353} 354 355#endif 356