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