CrashRecoveryContext.cpp revision ebe7eb884e30c8e9e9f44f499d75ee39cc6c6d6e
1//===--- CrashRecoveryContext.cpp - Crash Recovery ------------------------===// 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#include "llvm/Support/CrashRecoveryContext.h" 11#include "llvm/ADT/SmallString.h" 12#include "llvm/Config/config.h" 13#include "llvm/System/Mutex.h" 14#include "llvm/System/ThreadLocal.h" 15#include <setjmp.h> 16#include <cstdio> 17using namespace llvm; 18 19namespace { 20 21struct CrashRecoveryContextImpl; 22 23static sys::ThreadLocal<const CrashRecoveryContextImpl> CurrentContext; 24 25struct CrashRecoveryContextImpl { 26 CrashRecoveryContext *CRC; 27 std::string Backtrace; 28 ::jmp_buf JumpBuffer; 29 volatile unsigned Failed : 1; 30 31public: 32 CrashRecoveryContextImpl(CrashRecoveryContext *CRC) : CRC(CRC), 33 Failed(false) { 34 CurrentContext.set(this); 35 } 36 ~CrashRecoveryContextImpl() { 37 CurrentContext.erase(); 38 } 39 40 void HandleCrash() { 41 // Eliminate the current context entry, to avoid re-entering in case the 42 // cleanup code crashes. 43 CurrentContext.erase(); 44 45 assert(!Failed && "Crash recovery context already failed!"); 46 Failed = true; 47 48 // FIXME: Stash the backtrace. 49 50 // Jump back to the RunSafely we were called under. 51 longjmp(JumpBuffer, 1); 52 } 53}; 54 55} 56 57static sys::Mutex gCrashRecoveryContexMutex; 58static bool gCrashRecoveryEnabled = false; 59 60CrashRecoveryContext::~CrashRecoveryContext() { 61 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl; 62 delete CRCI; 63} 64 65CrashRecoveryContext *CrashRecoveryContext::GetCurrent() { 66 const CrashRecoveryContextImpl *CRCI = CurrentContext.get(); 67 if (!CRCI) 68 return 0; 69 70 return CRCI->CRC; 71} 72 73#ifdef LLVM_ON_WIN32 74 75// FIXME: No real Win32 implementation currently. 76 77void CrashRecoveryContext::Enable() { 78 sys::ScopedLock L(gCrashRecoveryContexMutex); 79 80 if (gCrashRecoveryEnabled) 81 return; 82 83 gCrashRecoveryEnabled = true; 84} 85 86void CrashRecoveryContext::Disable() { 87 sys::ScopedLock L(gCrashRecoveryContexMutex); 88 89 if (!gCrashRecoveryEnabled) 90 return; 91 92 gCrashRecoveryEnabled = false; 93} 94 95#else 96 97// Generic POSIX implementation. 98// 99// This implementation relies on synchronous signals being delivered to the 100// current thread. We use a thread local object to keep track of the active 101// crash recovery context, and install signal handlers to invoke HandleCrash on 102// the active object. 103// 104// This implementation does not to attempt to chain signal handlers in any 105// reliable fashion -- if we get a signal outside of a crash recovery context we 106// simply disable crash recovery and raise the signal again. 107 108#include <signal.h> 109 110static int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP }; 111static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]); 112static struct sigaction PrevActions[NumSignals]; 113 114static void CrashRecoverySignalHandler(int Signal) { 115 // Lookup the current thread local recovery object. 116 const CrashRecoveryContextImpl *CRCI = CurrentContext.get(); 117 118 if (!CRCI) { 119 // We didn't find a crash recovery context -- this means either we got a 120 // signal on a thread we didn't expect it on, the application got a signal 121 // outside of a crash recovery context, or something else went horribly 122 // wrong. 123 // 124 // Disable crash recovery and raise the signal again. The assumption here is 125 // that the enclosing application will terminate soon, and we won't want to 126 // attempt crash recovery again. 127 // 128 // This call of Disable isn't thread safe, but it doesn't actually matter. 129 CrashRecoveryContext::Disable(); 130 raise(Signal); 131 } 132 133 // Unblock the signal we received. 134 sigset_t SigMask; 135 sigemptyset(&SigMask); 136 sigaddset(&SigMask, Signal); 137 sigprocmask(SIG_UNBLOCK, &SigMask, 0); 138 139 if (CRCI) 140 const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash(); 141} 142 143void CrashRecoveryContext::Enable() { 144 sys::ScopedLock L(gCrashRecoveryContexMutex); 145 146 if (gCrashRecoveryEnabled) 147 return; 148 149 gCrashRecoveryEnabled = true; 150 151 // Setup the signal handler. 152 struct sigaction Handler; 153 Handler.sa_handler = CrashRecoverySignalHandler; 154 Handler.sa_flags = 0; 155 sigemptyset(&Handler.sa_mask); 156 157 for (unsigned i = 0; i != NumSignals; ++i) { 158 sigaction(Signals[i], &Handler, &PrevActions[i]); 159 } 160} 161 162void CrashRecoveryContext::Disable() { 163 sys::ScopedLock L(gCrashRecoveryContexMutex); 164 165 if (!gCrashRecoveryEnabled) 166 return; 167 168 gCrashRecoveryEnabled = false; 169 170 // Restore the previous signal handlers. 171 for (unsigned i = 0; i != NumSignals; ++i) 172 sigaction(Signals[i], &PrevActions[i], 0); 173} 174 175#endif 176 177bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) { 178 // If crash recovery is disabled, do nothing. 179 if (gCrashRecoveryEnabled) { 180 assert(!Impl && "Crash recovery context already initialized!"); 181 CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl(this); 182 Impl = CRCI; 183 184 if (setjmp(CRCI->JumpBuffer) != 0) { 185 return false; 186 } 187 } 188 189 Fn(UserData); 190 return true; 191} 192 193void CrashRecoveryContext::HandleCrash() { 194 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl; 195 assert(CRCI && "Crash recovery context never initialized!"); 196 CRCI->HandleCrash(); 197} 198 199const std::string &CrashRecoveryContext::getBacktrace() const { 200 CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl; 201 assert(CRC && "Crash recovery context never initialized!"); 202 assert(CRC->Failed && "No crash was detected!"); 203 return CRC->Backtrace; 204} 205