[llvm] r303274 - [CrashRecovery] Use SEH __try instead of VEH when available
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Wed May 17 10:02:16 PDT 2017
Author: rnk
Date: Wed May 17 12:02:16 2017
New Revision: 303274
URL: http://llvm.org/viewvc/llvm-project?rev=303274&view=rev
Log:
[CrashRecovery] Use SEH __try instead of VEH when available
Summary:
It avoids problems when other libraries raise exceptions. In particular,
OutputDebugString raises an exception that the debugger is supposed to
catch and suppress. VEH kicks in first right now, and that is entirely
incorrect.
Unfortunately, GCC does not support SEH, so I've kept the old buggy VEH
codepath around. We could fix it with SetUnhandledExceptionFilter, but
that is not per-thread, so a well-behaved library shouldn't set it.
Reviewers: zturner
Subscribers: llvm-commits, mgorny
Differential Revision: https://reviews.llvm.org/D33261
Added:
llvm/trunk/unittests/Support/CrashRecoveryTest.cpp
Modified:
llvm/trunk/lib/Support/CrashRecoveryContext.cpp
llvm/trunk/unittests/Support/CMakeLists.txt
Modified: llvm/trunk/lib/Support/CrashRecoveryContext.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/CrashRecoveryContext.cpp?rev=303274&r1=303273&r2=303274&view=diff
==============================================================================
--- llvm/trunk/lib/Support/CrashRecoveryContext.cpp (original)
+++ llvm/trunk/lib/Support/CrashRecoveryContext.cpp Wed May 17 12:02:16 2017
@@ -78,6 +78,9 @@ static bool gCrashRecoveryEnabled = fals
static ManagedStatic<sys::ThreadLocal<const CrashRecoveryContext>>
tlIsRecoveringFromCrash;
+static void installExceptionOrSignalHandlers();
+static void uninstallExceptionOrSignalHandlers();
+
CrashRecoveryContextCleanup::~CrashRecoveryContextCleanup() {}
CrashRecoveryContext::~CrashRecoveryContext() {
@@ -113,6 +116,23 @@ CrashRecoveryContext *CrashRecoveryConte
return CRCI->CRC;
}
+void CrashRecoveryContext::Enable() {
+ sys::ScopedLock L(*gCrashRecoveryContextMutex);
+ // FIXME: Shouldn't this be a refcount or something?
+ if (gCrashRecoveryEnabled)
+ return;
+ gCrashRecoveryEnabled = true;
+ installExceptionOrSignalHandlers();
+}
+
+void CrashRecoveryContext::Disable() {
+ sys::ScopedLock L(*gCrashRecoveryContextMutex);
+ if (!gCrashRecoveryEnabled)
+ return;
+ gCrashRecoveryEnabled = false;
+ uninstallExceptionOrSignalHandlers();
+}
+
void CrashRecoveryContext::registerCleanup(CrashRecoveryContextCleanup *cleanup)
{
if (!cleanup)
@@ -140,27 +160,51 @@ CrashRecoveryContext::unregisterCleanup(
delete cleanup;
}
-#ifdef LLVM_ON_WIN32
+#if defined(_MSC_VER)
+// If _MSC_VER is defined, we must have SEH. Use it if it's available. It's way
+// better than VEH. Vectored exception handling catches all exceptions happening
+// on the thread with installed exception handlers, so it can interfere with
+// internal exception handling of other libraries on that thread. SEH works
+// exactly as you would expect normal exception handling to work: it only
+// catches exceptions if they would bubble out from the stack frame with __try /
+// __except.
-#include "Windows/WindowsSupport.h"
+static void installExceptionOrSignalHandlers() {}
+static void uninstallExceptionOrSignalHandlers() {}
-// 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.
+bool CrashRecoveryContext::RunSafely(function_ref<void()> Fn) {
+ bool Result = true;
+ __try {
+ Fn();
+ } __except (1) { // Catch any exception.
+ Result = false;
+ }
+ return Result;
+}
+
+#else // !_MSC_VER
+
+#if defined(LLVM_ON_WIN32)
+// This is a non-MSVC compiler, probably mingw gcc or clang without
+// -fms-extensions. Use vectored exception handling (VEH).
+//
+// 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. Unfortunately, this causes problems in practice with other code
+// running on threads with LLVM crash recovery contexts, so we would like to
+// eventually move away from VEH.
//
-// Vectored exception handling is built on top of SEH, and so it
-// works on a per-thread basis.
+// Vectored works on a per-thread basis, which is an advantage over
+// SetUnhandledExceptionFilter. SetUnhandledExceptionFilter also doesn't have
+// any native support for chaining exception handlers, but VEH allows more than
+// one.
//
// 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).
+
+#include "Windows/WindowsSupport.h"
static LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ExceptionInfo)
{
@@ -203,14 +247,7 @@ static LONG CALLBACK ExceptionHandler(PE
// 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;
-
+static void installExceptionOrSignalHandlers() {
// 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
@@ -219,14 +256,7 @@ void CrashRecoveryContext::Enable() {
sCurrentExceptionHandle.set(handle);
}
-void CrashRecoveryContext::Disable() {
- sys::ScopedLock L(*gCrashRecoveryContextMutex);
-
- if (!gCrashRecoveryEnabled)
- return;
-
- gCrashRecoveryEnabled = false;
-
+static void uninstallExceptionOrSignalHandlers() {
PVOID currentHandle = const_cast<PVOID>(sCurrentExceptionHandle.get());
if (currentHandle) {
// Now we can remove the vectored exception handler from the chain
@@ -237,7 +267,7 @@ void CrashRecoveryContext::Disable() {
}
}
-#else
+#else // !LLVM_ON_WIN32
// Generic POSIX implementation.
//
@@ -289,14 +319,7 @@ static void CrashRecoverySignalHandler(i
const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
}
-void CrashRecoveryContext::Enable() {
- sys::ScopedLock L(*gCrashRecoveryContextMutex);
-
- if (gCrashRecoveryEnabled)
- return;
-
- gCrashRecoveryEnabled = true;
-
+static void installExceptionOrSignalHandlers() {
// Setup the signal handler.
struct sigaction Handler;
Handler.sa_handler = CrashRecoverySignalHandler;
@@ -308,20 +331,13 @@ void CrashRecoveryContext::Enable() {
}
}
-void CrashRecoveryContext::Disable() {
- sys::ScopedLock L(*gCrashRecoveryContextMutex);
-
- if (!gCrashRecoveryEnabled)
- return;
-
- gCrashRecoveryEnabled = false;
-
+static void uninstallExceptionOrSignalHandlers() {
// Restore the previous signal handlers.
for (unsigned i = 0; i != NumSignals; ++i)
sigaction(Signals[i], &PrevActions[i], nullptr);
}
-#endif
+#endif // !LLVM_ON_WIN32
bool CrashRecoveryContext::RunSafely(function_ref<void()> Fn) {
// If crash recovery is disabled, do nothing.
@@ -339,6 +355,8 @@ bool CrashRecoveryContext::RunSafely(fun
return true;
}
+#endif // !_MSC_VER
+
void CrashRecoveryContext::HandleCrash() {
CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
assert(CRCI && "Crash recovery context never initialized!");
Modified: llvm/trunk/unittests/Support/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/CMakeLists.txt?rev=303274&r1=303273&r2=303274&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/CMakeLists.txt (original)
+++ llvm/trunk/unittests/Support/CMakeLists.txt Wed May 17 12:02:16 2017
@@ -11,6 +11,7 @@ add_llvm_unittest(SupportTests
BlockFrequencyTest.cpp
BranchProbabilityTest.cpp
CachePruningTest.cpp
+ CrashRecoveryTest.cpp
Casting.cpp
Chrono.cpp
CommandLineTest.cpp
Added: llvm/trunk/unittests/Support/CrashRecoveryTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/CrashRecoveryTest.cpp?rev=303274&view=auto
==============================================================================
--- llvm/trunk/unittests/Support/CrashRecoveryTest.cpp (added)
+++ llvm/trunk/unittests/Support/CrashRecoveryTest.cpp Wed May 17 12:02:16 2017
@@ -0,0 +1,83 @@
+//===- llvm/unittest/Support/CrashRecoveryTest.cpp ------------------------===//
+//
+// 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/Support/Compiler.h"
+#include "gtest/gtest.h"
+
+#ifdef LLVM_ON_WIN32
+#define WIN32_LEAN_AND_MEAN
+#define NOGDI
+#include <windows.h>
+#endif
+
+using namespace llvm;
+using namespace llvm::sys;
+
+static int GlobalInt = 0;
+static void nullDeref() { *(volatile int *)nullptr = 0; }
+static void incrementGlobal() { ++GlobalInt; }
+static void llvmTrap() { LLVM_BUILTIN_TRAP; }
+
+TEST(CrashRecoveryTest, Basic) {
+ llvm::CrashRecoveryContext::Enable();
+ GlobalInt = 0;
+ EXPECT_TRUE(CrashRecoveryContext().RunSafely(incrementGlobal));
+ EXPECT_EQ(1, GlobalInt);
+ EXPECT_FALSE(CrashRecoveryContext().RunSafely(nullDeref));
+ EXPECT_FALSE(CrashRecoveryContext().RunSafely(llvmTrap));
+}
+
+struct IncrementGlobalCleanup : CrashRecoveryContextCleanup {
+ IncrementGlobalCleanup(CrashRecoveryContext *CRC)
+ : CrashRecoveryContextCleanup(CRC) {}
+ virtual void recoverResources() { ++GlobalInt; }
+};
+
+static void noop() {}
+
+TEST(CrashRecoveryTest, Cleanup) {
+ llvm::CrashRecoveryContext::Enable();
+ GlobalInt = 0;
+ {
+ CrashRecoveryContext CRC;
+ CRC.registerCleanup(new IncrementGlobalCleanup(&CRC));
+ EXPECT_TRUE(CRC.RunSafely(noop));
+ } // run cleanups
+ EXPECT_EQ(1, GlobalInt);
+
+ GlobalInt = 0;
+ {
+ CrashRecoveryContext CRC;
+ CRC.registerCleanup(new IncrementGlobalCleanup(&CRC));
+ EXPECT_FALSE(CRC.RunSafely(nullDeref));
+ } // run cleanups
+ EXPECT_EQ(1, GlobalInt);
+}
+
+#ifdef LLVM_ON_WIN32
+static void raiseIt() {
+ RaiseException(123, EXCEPTION_NONCONTINUABLE, 0, NULL);
+}
+
+TEST(CrashRecoveryTest, RaiseException) {
+ llvm::CrashRecoveryContext::Enable();
+ EXPECT_FALSE(CrashRecoveryContext().RunSafely(raiseIt));
+}
+
+static void outputString() {
+ OutputDebugStringA("output for debugger\n");
+}
+
+TEST(CrashRecoveryTest, CallOutputDebugString) {
+ llvm::CrashRecoveryContext::Enable();
+ EXPECT_TRUE(CrashRecoveryContext().RunSafely(outputString));
+}
+
+#endif
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