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 && __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 // We 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 // We rely on a std::string implementation for which repeated calls to 128 // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these 129 // strings to try to ensure this is safe. 130 const char *path = FilesToRemove[i].c_str(); 131 132 // Get the status so we can determine if it's a file or directory. If we 133 // can't stat the file, ignore it. 134 struct stat buf; 135 if (stat(path, &buf) != 0) 136 continue; 137 138 // If this is not a regular file, ignore it. We want to prevent removal of 139 // special files like /dev/null, even if the compiler is being run with the 140 // super-user permissions. 141 if (!S_ISREG(buf.st_mode)) 142 continue; 143 144 // Otherwise, remove the file. We ignore any errors here as there is nothing 145 // else we can do. 146 unlink(path); 147 } 148} 149 150// SignalHandler - The signal handler that runs. 151static RETSIGTYPE SignalHandler(int Sig) { 152 // Restore the signal behavior to default, so that the program actually 153 // crashes when we return and the signal reissues. This also ensures that if 154 // we crash in our signal handler that the program will terminate immediately 155 // instead of recursing in the signal handler. 156 UnregisterHandlers(); 157 158 // Unmask all potentially blocked kill signals. 159 sigset_t SigMask; 160 sigfillset(&SigMask); 161 sigprocmask(SIG_UNBLOCK, &SigMask, 0); 162 163 SignalsMutex.acquire(); 164 RemoveFilesToRemove(); 165 166 if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) { 167 if (InterruptFunction) { 168 void (*IF)() = InterruptFunction; 169 SignalsMutex.release(); 170 InterruptFunction = 0; 171 IF(); // run the interrupt function. 172 return; 173 } 174 175 SignalsMutex.release(); 176 raise(Sig); // Execute the default handler. 177 return; 178 } 179 180 SignalsMutex.release(); 181 182 // Otherwise if it is a fault (like SEGV) run any handler. 183 for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i) 184 CallBacksToRun[i].first(CallBacksToRun[i].second); 185} 186 187void llvm::sys::RunInterruptHandlers() { 188 SignalsMutex.acquire(); 189 RemoveFilesToRemove(); 190 SignalsMutex.release(); 191} 192 193void llvm::sys::SetInterruptFunction(void (*IF)()) { 194 SignalsMutex.acquire(); 195 InterruptFunction = IF; 196 SignalsMutex.release(); 197 RegisterHandlers(); 198} 199 200// RemoveFileOnSignal - The public API 201bool llvm::sys::RemoveFileOnSignal(const sys::Path &Filename, 202 std::string* ErrMsg) { 203 SignalsMutex.acquire(); 204 std::string *OldPtr = FilesToRemove.empty() ? 0 : &FilesToRemove[0]; 205 FilesToRemove.push_back(Filename.str()); 206 207 // We want to call 'c_str()' on every std::string in this vector so that if 208 // the underlying implementation requires a re-allocation, it happens here 209 // rather than inside of the signal handler. If we see the vector grow, we 210 // have to call it on every entry. If it remains in place, we only need to 211 // call it on the latest one. 212 if (OldPtr == &FilesToRemove[0]) 213 FilesToRemove.back().c_str(); 214 else 215 for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) 216 FilesToRemove[i].c_str(); 217 218 SignalsMutex.release(); 219 220 RegisterHandlers(); 221 return false; 222} 223 224// DontRemoveFileOnSignal - The public API 225void llvm::sys::DontRemoveFileOnSignal(const sys::Path &Filename) { 226 SignalsMutex.acquire(); 227 std::vector<std::string>::reverse_iterator RI = 228 std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename.str()); 229 std::vector<std::string>::iterator I = FilesToRemove.end(); 230 if (RI != FilesToRemove.rend()) 231 I = FilesToRemove.erase(RI.base()-1); 232 233 // We need to call c_str() on every element which would have been moved by 234 // the erase. These elements, in a C++98 implementation where c_str() 235 // requires a reallocation on the first call may have had the call to c_str() 236 // made on insertion become invalid by being copied down an element. 237 for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I) 238 I->c_str(); 239 240 SignalsMutex.release(); 241} 242 243/// AddSignalHandler - Add a function to be called when a signal is delivered 244/// to the process. The handler can have a cookie passed to it to identify 245/// what instance of the handler it is. 246void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) { 247 CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie)); 248 RegisterHandlers(); 249} 250 251 252// PrintStackTrace - In the case of a program crash or fault, print out a stack 253// trace so that the user has an indication of why and where we died. 254// 255// On glibc systems we have the 'backtrace' function, which works nicely, but 256// doesn't demangle symbols. 257static void PrintStackTrace(void *) { 258#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES) 259 static void* StackTrace[256]; 260 // Use backtrace() to output a backtrace on Linux systems with glibc. 261 int depth = backtrace(StackTrace, 262 static_cast<int>(array_lengthof(StackTrace))); 263#if HAVE_DLFCN_H && __GNUG__ 264 int width = 0; 265 for (int i = 0; i < depth; ++i) { 266 Dl_info dlinfo; 267 dladdr(StackTrace[i], &dlinfo); 268 const char* name = strrchr(dlinfo.dli_fname, '/'); 269 270 int nwidth; 271 if (name == NULL) nwidth = strlen(dlinfo.dli_fname); 272 else nwidth = strlen(name) - 1; 273 274 if (nwidth > width) width = nwidth; 275 } 276 277 for (int i = 0; i < depth; ++i) { 278 Dl_info dlinfo; 279 dladdr(StackTrace[i], &dlinfo); 280 281 fprintf(stderr, "%-2d", i); 282 283 const char* name = strrchr(dlinfo.dli_fname, '/'); 284 if (name == NULL) fprintf(stderr, " %-*s", width, dlinfo.dli_fname); 285 else fprintf(stderr, " %-*s", width, name+1); 286 287 fprintf(stderr, " %#0*lx", 288 (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]); 289 290 if (dlinfo.dli_sname != NULL) { 291 int res; 292 fputc(' ', stderr); 293 char* d = abi::__cxa_demangle(dlinfo.dli_sname, NULL, NULL, &res); 294 if (d == NULL) fputs(dlinfo.dli_sname, stderr); 295 else fputs(d, stderr); 296 free(d); 297 298 fprintf(stderr, " + %tu",(char*)StackTrace[i]-(char*)dlinfo.dli_saddr); 299 } 300 fputc('\n', stderr); 301 } 302#else 303 backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO); 304#endif 305#endif 306} 307 308/// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or 309/// SIGSEGV) is delivered to the process, print a stack trace and then exit. 310void llvm::sys::PrintStackTraceOnErrorSignal() { 311 AddSignalHandler(PrintStackTrace, 0); 312 313#if defined(__APPLE__) 314 // Environment variable to disable any kind of crash dialog. 315 if (getenv("LLVM_DISABLE_CRASH_REPORT")) { 316 mach_port_t self = mach_task_self(); 317 318 exception_mask_t mask = EXC_MASK_CRASH; 319 320 kern_return_t ret = task_set_exception_ports(self, 321 mask, 322 MACH_PORT_NULL, 323 EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES, 324 THREAD_STATE_NONE); 325 (void)ret; 326 } 327#endif 328} 329 330 331/***/ 332 333// On Darwin, raise sends a signal to the main thread instead of the current 334// thread. This has the unfortunate effect that assert() and abort() will end up 335// bypassing our crash recovery attempts. We work around this for anything in 336// the same linkage unit by just defining our own versions of the assert handler 337// and abort. 338 339#ifdef __APPLE__ 340 341#include <signal.h> 342#include <pthread.h> 343 344int raise(int sig) { 345 return pthread_kill(pthread_self(), sig); 346} 347 348void __assert_rtn(const char *func, 349 const char *file, 350 int line, 351 const char *expr) { 352 if (func) 353 fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n", 354 expr, func, file, line); 355 else 356 fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n", 357 expr, file, line); 358 abort(); 359} 360 361void abort() { 362 raise(SIGABRT); 363 usleep(1000); 364 __builtin_trap(); 365} 366 367#endif 368