--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/Support/CrashRecoveryContext.cpp	Thu Dec 12 13:56:28 2013 +0900
@@ -0,0 +1,356 @@
+//===--- CrashRecoveryContext.cpp - Crash Recovery ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/CrashRecoveryContext.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Mutex.h"
+#include "llvm/Support/ThreadLocal.h"
+#include <cstdio>
+#include <setjmp.h>
+using namespace llvm;
+
+namespace {
+
+struct CrashRecoveryContextImpl;
+
+static ManagedStatic<sys::ThreadLocal<const CrashRecoveryContextImpl> > CurrentContext;
+
+struct CrashRecoveryContextImpl {
+  CrashRecoveryContext *CRC;
+  std::string Backtrace;
+  ::jmp_buf JumpBuffer;
+  volatile unsigned Failed : 1;
+  unsigned SwitchedThread : 1;
+
+public:
+  CrashRecoveryContextImpl(CrashRecoveryContext *CRC) : CRC(CRC),
+                                                        Failed(false),
+                                                        SwitchedThread(false) {
+    CurrentContext->set(this);
+  }
+  ~CrashRecoveryContextImpl() {
+    if (!SwitchedThread)
+      CurrentContext->erase();
+  }
+
+  /// \brief Called when the separate crash-recovery thread was finished, to
+  /// indicate that we don't need to clear the thread-local CurrentContext.
+  void setSwitchedThread() { SwitchedThread = true; }
+
+  void HandleCrash() {
+    // Eliminate the current context entry, to avoid re-entering in case the
+    // cleanup code crashes.
+    CurrentContext->erase();
+
+    assert(!Failed && "Crash recovery context already failed!");
+    Failed = true;
+
+    // FIXME: Stash the backtrace.
+
+    // Jump back to the RunSafely we were called under.
+    longjmp(JumpBuffer, 1);
+  }
+};
+
+}
+
+static ManagedStatic<sys::Mutex> gCrashRecoveryContextMutex;
+static bool gCrashRecoveryEnabled = false;
+
+static ManagedStatic<sys::ThreadLocal<const CrashRecoveryContextCleanup> >
+       tlIsRecoveringFromCrash;
+
+CrashRecoveryContextCleanup::~CrashRecoveryContextCleanup() {}
+
+CrashRecoveryContext::~CrashRecoveryContext() {
+  // Reclaim registered resources.
+  CrashRecoveryContextCleanup *i = head;
+  tlIsRecoveringFromCrash->set(head);
+  while (i) {
+    CrashRecoveryContextCleanup *tmp = i;
+    i = tmp->next;
+    tmp->cleanupFired = true;
+    tmp->recoverResources();
+    delete tmp;
+  }
+  tlIsRecoveringFromCrash->erase();
+  
+  CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
+  delete CRCI;
+}
+
+bool CrashRecoveryContext::isRecoveringFromCrash() {
+  return tlIsRecoveringFromCrash->get() != 0;
+}
+
+CrashRecoveryContext *CrashRecoveryContext::GetCurrent() {
+  if (!gCrashRecoveryEnabled)
+    return 0;
+
+  const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
+  if (!CRCI)
+    return 0;
+
+  return CRCI->CRC;
+}
+
+void CrashRecoveryContext::registerCleanup(CrashRecoveryContextCleanup *cleanup)
+{
+  if (!cleanup)
+    return;
+  if (head)
+    head->prev = cleanup;
+  cleanup->next = head;
+  head = cleanup;
+}
+
+void
+CrashRecoveryContext::unregisterCleanup(CrashRecoveryContextCleanup *cleanup) {
+  if (!cleanup)
+    return;
+  if (cleanup == head) {
+    head = cleanup->next;
+    if (head)
+      head->prev = 0;
+  }
+  else {
+    cleanup->prev->next = cleanup->next;
+    if (cleanup->next)
+      cleanup->next->prev = cleanup->prev;
+  }
+  delete cleanup;
+}
+
+#ifdef LLVM_ON_WIN32
+
+#include "Windows/Windows.h"
+
+// On Windows, we can make use of vectored exception handling to
+// catch most crashing situations.  Note that this does mean
+// we will be alerted of exceptions *before* structured exception
+// handling has the opportunity to catch it.  But that isn't likely
+// to cause problems because nowhere in the project is SEH being
+// used.
+//
+// Vectored exception handling is built on top of SEH, and so it
+// works on a per-thread basis.
+//
+// The vectored exception handler functionality was added in Windows
+// XP, so if support for older versions of Windows is required,
+// it will have to be added.
+//
+// If we want to support as far back as Win2k, we could use the
+// SetUnhandledExceptionFilter API, but there's a risk of that
+// being entirely overwritten (it's not a chain).
+
+static LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ExceptionInfo)
+{
+  // Lookup the current thread local recovery object.
+  const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
+
+  if (!CRCI) {
+    // Something has gone horribly wrong, so let's just tell everyone
+    // to keep searching
+    CrashRecoveryContext::Disable();
+    return EXCEPTION_CONTINUE_SEARCH;
+  }
+
+  // TODO: We can capture the stack backtrace here and store it on the
+  // implementation if we so choose.
+
+  // Handle the crash
+  const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
+
+  // Note that we don't actually get here because HandleCrash calls
+  // longjmp, which means the HandleCrash function never returns.
+  llvm_unreachable("Handled the crash, should have longjmp'ed out of here");
+}
+
+// Because the Enable and Disable calls are static, it means that
+// there may not actually be an Impl available, or even a current
+// CrashRecoveryContext at all.  So we make use of a thread-local
+// exception table.  The handles contained in here will either be
+// non-NULL, valid VEH handles, or NULL.
+static sys::ThreadLocal<const void> sCurrentExceptionHandle;
+
+void CrashRecoveryContext::Enable() {
+  sys::ScopedLock L(*gCrashRecoveryContextMutex);
+
+  if (gCrashRecoveryEnabled)
+    return;
+
+  gCrashRecoveryEnabled = true;
+
+  // We can set up vectored exception handling now.  We will install our
+  // handler as the front of the list, though there's no assurances that
+  // it will remain at the front (another call could install itself before
+  // our handler).  This 1) isn't likely, and 2) shouldn't cause problems.
+  PVOID handle = ::AddVectoredExceptionHandler(1, ExceptionHandler);
+  sCurrentExceptionHandle.set(handle);
+}
+
+void CrashRecoveryContext::Disable() {
+  sys::ScopedLock L(*gCrashRecoveryContextMutex);
+
+  if (!gCrashRecoveryEnabled)
+    return;
+
+  gCrashRecoveryEnabled = false;
+
+  PVOID currentHandle = const_cast<PVOID>(sCurrentExceptionHandle.get());
+  if (currentHandle) {
+    // Now we can remove the vectored exception handler from the chain
+    ::RemoveVectoredExceptionHandler(currentHandle);
+
+    // Reset the handle in our thread-local set.
+    sCurrentExceptionHandle.set(NULL);
+  }
+}
+
+#else
+
+// Generic POSIX implementation.
+//
+// This implementation relies on synchronous signals being delivered to the
+// current thread. We use a thread local object to keep track of the active
+// crash recovery context, and install signal handlers to invoke HandleCrash on
+// the active object.
+//
+// This implementation does not to attempt to chain signal handlers in any
+// reliable fashion -- if we get a signal outside of a crash recovery context we
+// simply disable crash recovery and raise the signal again.
+
+#include <signal.h>
+
+static const int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP };
+static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]);
+static struct sigaction PrevActions[NumSignals];
+
+static void CrashRecoverySignalHandler(int Signal) {
+  // Lookup the current thread local recovery object.
+  const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
+
+  if (!CRCI) {
+    // We didn't find a crash recovery context -- this means either we got a
+    // signal on a thread we didn't expect it on, the application got a signal
+    // outside of a crash recovery context, or something else went horribly
+    // wrong.
+    //
+    // Disable crash recovery and raise the signal again. The assumption here is
+    // that the enclosing application will terminate soon, and we won't want to
+    // attempt crash recovery again.
+    //
+    // This call of Disable isn't thread safe, but it doesn't actually matter.
+    CrashRecoveryContext::Disable();
+    raise(Signal);
+
+    // The signal will be thrown once the signal mask is restored.
+    return;
+  }
+
+  // Unblock the signal we received.
+  sigset_t SigMask;
+  sigemptyset(&SigMask);
+  sigaddset(&SigMask, Signal);
+  sigprocmask(SIG_UNBLOCK, &SigMask, 0);
+
+  if (CRCI)
+    const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
+}
+
+void CrashRecoveryContext::Enable() {
+  sys::ScopedLock L(*gCrashRecoveryContextMutex);
+
+  if (gCrashRecoveryEnabled)
+    return;
+
+  gCrashRecoveryEnabled = true;
+
+  // Setup the signal handler.
+  struct sigaction Handler;
+  Handler.sa_handler = CrashRecoverySignalHandler;
+  Handler.sa_flags = 0;
+  sigemptyset(&Handler.sa_mask);
+
+  for (unsigned i = 0; i != NumSignals; ++i) {
+    sigaction(Signals[i], &Handler, &PrevActions[i]);
+  }
+}
+
+void CrashRecoveryContext::Disable() {
+  sys::ScopedLock L(*gCrashRecoveryContextMutex);
+
+  if (!gCrashRecoveryEnabled)
+    return;
+
+  gCrashRecoveryEnabled = false;
+
+  // Restore the previous signal handlers.
+  for (unsigned i = 0; i != NumSignals; ++i)
+    sigaction(Signals[i], &PrevActions[i], 0);
+}
+
+#endif
+
+bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) {
+  // If crash recovery is disabled, do nothing.
+  if (gCrashRecoveryEnabled) {
+    assert(!Impl && "Crash recovery context already initialized!");
+    CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl(this);
+    Impl = CRCI;
+
+    if (setjmp(CRCI->JumpBuffer) != 0) {
+      return false;
+    }
+  }
+
+  Fn(UserData);
+  return true;
+}
+
+void CrashRecoveryContext::HandleCrash() {
+  CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
+  assert(CRCI && "Crash recovery context never initialized!");
+  CRCI->HandleCrash();
+}
+
+const std::string &CrashRecoveryContext::getBacktrace() const {
+  CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl;
+  assert(CRC && "Crash recovery context never initialized!");
+  assert(CRC->Failed && "No crash was detected!");
+  return CRC->Backtrace;
+}
+
+//
+
+namespace {
+struct RunSafelyOnThreadInfo {
+  void (*UserFn)(void*);
+  void *UserData;
+  CrashRecoveryContext *CRC;
+  bool Result;
+};
+}
+
+static void RunSafelyOnThread_Dispatch(void *UserData) {
+  RunSafelyOnThreadInfo *Info =
+    reinterpret_cast<RunSafelyOnThreadInfo*>(UserData);
+  Info->Result = Info->CRC->RunSafely(Info->UserFn, Info->UserData);
+}
+bool CrashRecoveryContext::RunSafelyOnThread(void (*Fn)(void*), void *UserData,
+                                             unsigned RequestedStackSize) {
+  RunSafelyOnThreadInfo Info = { Fn, UserData, this, false };
+  llvm_execute_on_thread(RunSafelyOnThread_Dispatch, &Info, RequestedStackSize);
+  if (CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *)Impl)
+    CRC->setSwitchedThread();
+  return Info.Result;
+}