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