lib/Support/CrashRecoveryContext.cpp

   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/Support/Mutex.h"
  14 #include "llvm/Support/ThreadLocal.h"
  15 #include <setjmp.h>
  16 #include <cstdio>
  17 using namespace llvm;
  18
  19 namespace {
  20
  21 struct CrashRecoveryContextImpl;
  22
  23 static sys::ThreadLocal<const CrashRecoveryContextImpl> CurrentContext;
  24
  25 struct CrashRecoveryContextImpl {
  26   CrashRecoveryContext *CRC;
  27   std::string Backtrace;
  28   ::jmp_buf JumpBuffer;
  29   volatile unsigned Failed : 1;
  30
  31 public:
  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
  57 static sys::Mutex gCrashRecoveryContexMutex;
  58 static bool gCrashRecoveryEnabled = false;
  59
  60 static sys::ThreadLocal<const CrashRecoveryContextCleanup>
  61        tlIsRecoveringFromCrash;
  62
  63 CrashRecoveryContextCleanup::~CrashRecoveryContextCleanup() {}
  64
  65 CrashRecoveryContext::~CrashRecoveryContext() {
  66   // Reclaim registered resources.
  67   CrashRecoveryContextCleanup *i = head;
  68   tlIsRecoveringFromCrash.set(head);
  69   while (i) {
  70     CrashRecoveryContextCleanup *tmp = i;
  71     i = tmp->next;
  72     tmp->cleanupFired = true;
  73     tmp->recoverResources();
  74     delete tmp;
  75   }
  76   tlIsRecoveringFromCrash.erase();
  77
  78   CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
  79   delete CRCI;
  80 }
  81
  82 bool CrashRecoveryContext::isRecoveringFromCrash() {
  83   return tlIsRecoveringFromCrash.get() != 0;
  84 }
  85
  86 CrashRecoveryContext *CrashRecoveryContext::GetCurrent() {
  87   if (!gCrashRecoveryEnabled)
  88     return 0;
  89
  90   const CrashRecoveryContextImpl *CRCI = CurrentContext.get();
  91   if (!CRCI)
  92     return 0;
  93
  94   return CRCI->CRC;
  95 }
  96
  97 void CrashRecoveryContext::registerCleanup(CrashRecoveryContextCleanup *cleanup)
  98 {
  99   if (!cleanup)
 100     return;
 101   if (head)
 102     head->prev = cleanup;
 103   cleanup->next = head;
 104   head = cleanup;
 105 }
 106
 107 void
 108 CrashRecoveryContext::unregisterCleanup(CrashRecoveryContextCleanup *cleanup) {
 109   if (!cleanup)
 110     return;
 111   if (cleanup == head) {
 112     head = cleanup->next;
 113     if (head)
 114       head->prev = 0;
 115   }
 116   else {
 117     cleanup->prev->next = cleanup->next;
 118     if (cleanup->next)
 119       cleanup->next->prev = cleanup->prev;
 120   }
 121   delete cleanup;
 122 }
 123
 124 #ifdef LLVM_ON_WIN32
 125
 126 // FIXME: No real Win32 implementation currently.
 127
 128 void CrashRecoveryContext::Enable() {
 129   sys::ScopedLock L(gCrashRecoveryContexMutex);
 130
 131   if (gCrashRecoveryEnabled)
 132     return;
 133
 134   gCrashRecoveryEnabled = true;
 135 }
 136
 137 void CrashRecoveryContext::Disable() {
 138   sys::ScopedLock L(gCrashRecoveryContexMutex);
 139
 140   if (!gCrashRecoveryEnabled)
 141     return;
 142
 143   gCrashRecoveryEnabled = false;
 144 }
 145
 146 #else
 147
 148 // Generic POSIX implementation.
 149 //
 150 // This implementation relies on synchronous signals being delivered to the
 151 // current thread. We use a thread local object to keep track of the active
 152 // crash recovery context, and install signal handlers to invoke HandleCrash on
 153 // the active object.
 154 //
 155 // This implementation does not to attempt to chain signal handlers in any
 156 // reliable fashion -- if we get a signal outside of a crash recovery context we
 157 // simply disable crash recovery and raise the signal again.
 158
 159 #include <signal.h>
 160
 161 static int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP };
 162 static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]);
 163 static struct sigaction PrevActions[NumSignals];
 164
 165 static void CrashRecoverySignalHandler(int Signal) {
 166   // Lookup the current thread local recovery object.
 167   const CrashRecoveryContextImpl *CRCI = CurrentContext.get();
 168
 169   if (!CRCI) {
 170     // We didn't find a crash recovery context -- this means either we got a
 171     // signal on a thread we didn't expect it on, the application got a signal
 172     // outside of a crash recovery context, or something else went horribly
 173     // wrong.
 174     //
 175     // Disable crash recovery and raise the signal again. The assumption here is
 176     // that the enclosing application will terminate soon, and we won't want to
 177     // attempt crash recovery again.
 178     //
 179     // This call of Disable isn't thread safe, but it doesn't actually matter.
 180     CrashRecoveryContext::Disable();
 181     raise(Signal);
 182
 183     // The signal will be thrown once the signal mask is restored.
 184     return;
 185   }
 186
 187   // Unblock the signal we received.
 188   sigset_t SigMask;
 189   sigemptyset(&SigMask);
 190   sigaddset(&SigMask, Signal);
 191   sigprocmask(SIG_UNBLOCK, &SigMask, 0);
 192
 193   if (CRCI)
 194     const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
 195 }
 196
 197 void CrashRecoveryContext::Enable() {
 198   sys::ScopedLock L(gCrashRecoveryContexMutex);
 199
 200   if (gCrashRecoveryEnabled)
 201     return;
 202
 203   gCrashRecoveryEnabled = true;
 204
 205   // Setup the signal handler.
 206   struct sigaction Handler;
 207   Handler.sa_handler = CrashRecoverySignalHandler;
 208   Handler.sa_flags = 0;
 209   sigemptyset(&Handler.sa_mask);
 210
 211   for (unsigned i = 0; i != NumSignals; ++i) {
 212     sigaction(Signals[i], &Handler, &PrevActions[i]);
 213   }
 214 }
 215
 216 void CrashRecoveryContext::Disable() {
 217   sys::ScopedLock L(gCrashRecoveryContexMutex);
 218
 219   if (!gCrashRecoveryEnabled)
 220     return;
 221
 222   gCrashRecoveryEnabled = false;
 223
 224   // Restore the previous signal handlers.
 225   for (unsigned i = 0; i != NumSignals; ++i)
 226     sigaction(Signals[i], &PrevActions[i], 0);
 227 }
 228
 229 #endif
 230
 231 bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) {
 232   // If crash recovery is disabled, do nothing.
 233   if (gCrashRecoveryEnabled) {
 234     assert(!Impl && "Crash recovery context already initialized!");
 235     CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl(this);
 236     Impl = CRCI;
 237
 238     if (setjmp(CRCI->JumpBuffer) != 0) {
 239       return false;
 240     }
 241   }
 242
 243   Fn(UserData);
 244   return true;
 245 }
 246
 247 void CrashRecoveryContext::HandleCrash() {
 248   CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
 249   assert(CRCI && "Crash recovery context never initialized!");
 250   CRCI->HandleCrash();
 251 }
 252
 253 const std::string &CrashRecoveryContext::getBacktrace() const {
 254   CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl;
 255   assert(CRC && "Crash recovery context never initialized!");
 256   assert(CRC->Failed && "No crash was detected!");
 257   return CRC->Backtrace;
 258 }
 259
 260 //
 261
 262 namespace {
 263 struct RunSafelyOnThreadInfo {
 264   void (*UserFn)(void*);
 265   void *UserData;
 266   CrashRecoveryContext *CRC;
 267   bool Result;
 268 };
 269 }
 270
 271 static void RunSafelyOnThread_Dispatch(void *UserData) {
 272   RunSafelyOnThreadInfo *Info =
 273     reinterpret_cast<RunSafelyOnThreadInfo*>(UserData);
 274   Info->Result = Info->CRC->RunSafely(Info->UserFn, Info->UserData);
 275 }
 276 bool CrashRecoveryContext::RunSafelyOnThread(void (*Fn)(void*), void *UserData,
 277                                              unsigned RequestedStackSize) {
 278   RunSafelyOnThreadInfo Info = { Fn, UserData, this, false };
 279   llvm_execute_on_thread(RunSafelyOnThread_Dispatch, &Info, RequestedStackSize);
 280   return Info.Result;
 281 }