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.erase(); 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 int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP }; 91 static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]); 92 static struct sigaction PrevActions[NumSignals]; 93 94 static void CrashRecoverySignalHandler(int Signal) { 95 // Lookup the current thread local recovery object. 96 const CrashRecoveryContextImpl *CRCI = CurrentContext.get(); 97 98 if (!CRCI) { 99 // We didn't find a crash recovery context -- this means either we got a 100 // signal on a thread we didn't expect it on, the application got a signal 101 // outside of a crash recovery context, or something else went horribly 102 // wrong. 103 // 104 // Disable crash recovery and raise the signal again. The assumption here is 105 // that the enclosing application will terminate soon, and we won't want to 106 // attempt crash recovery again. 107 // 108 // This call of Disable isn't thread safe, but it doesn't actually matter. 109 CrashRecoveryContext::Disable(); 110 raise(Signal); 111 } 112 113 // Unblock the signal we received. 114 sigset_t SigMask; 115 sigemptyset(&SigMask); 116 sigaddset(&SigMask, Signal); 117 sigprocmask(SIG_UNBLOCK, &SigMask, 0); 118 119 if (CRCI) 120 const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash(); 121 } 122 123 void CrashRecoveryContext::Enable() { 124 if (gCrashRecoveryEnabled) 125 return; 126 127 gCrashRecoveryEnabled = true; 128 129 // Setup the signal handler. 130 struct sigaction Handler; 131 Handler.sa_handler = CrashRecoverySignalHandler; 132 Handler.sa_flags = 0; 133 sigemptyset(&Handler.sa_mask); 134 135 for (unsigned i = 0; i != NumSignals; ++i) { 136 sigaction(Signals[i], &Handler, &PrevActions[i]); 137 } 138 } 139 140 void CrashRecoveryContext::Disable() { 141 if (!gCrashRecoveryEnabled) 142 return; 143 144 gCrashRecoveryEnabled = false; 145 146 // Restore the previous signal handlers. 147 for (unsigned i = 0; i != NumSignals; ++i) 148 sigaction(Signals[i], &PrevActions[i], 0); 149 } 150 151 #endif 152 153 bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) { 154 // If crash recovery is disabled, do nothing. 155 if (gCrashRecoveryEnabled) { 156 assert(!Impl && "Crash recovery context already initialized!"); 157 CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl; 158 Impl = CRCI; 159 160 if (setjmp(CRCI->JumpBuffer) != 0) { 161 return false; 162 } 163 } 164 165 Fn(UserData); 166 return true; 167 } 168 169 void CrashRecoveryContext::HandleCrash() { 170 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl; 171 assert(CRCI && "Crash recovery context never initialized!"); 172 CRCI->HandleCrash(); 173 } 174 175 const std::string &CrashRecoveryContext::getBacktrace() const { 176 CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl; 177 assert(CRC && "Crash recovery context never initialized!"); 178 assert(CRC->Failed && "No crash was detected!"); 179 return CRC->Backtrace; 180 } 181