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