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EE Suspension on x86 should use RtlRestoreContext when available #65878

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Merged
VSadov merged 9 commits into from
Mar 2, 2022
Merged

EE Suspension on x86 should use RtlRestoreContext when available #65878

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752091c
RestoreContextSimulated
VSadov Feb 25, 2022
7fbba05
probe for RtlRestoreContext
VSadov Feb 25, 2022
50c5ed6
ntdll.dll
VSadov Feb 25, 2022
b176a8e
restore self-trap sequence
VSadov Feb 25, 2022
de51359
PR feedback
VSadov Feb 25, 2022
d4e1f52
Clarify CopyContext in RedirectedHandledJITCaseExceptionFilter
VSadov Feb 25, 2022
4e4245d
simpler indentation.
VSadov Mar 2, 2022
6fcc73e
restore last error on the legacy path.
VSadov Mar 2, 2022
bfee187
Update src/coreclr/vm/threads.h
danmoseley Mar 2, 2022
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8 changes: 8 additions & 0 deletions src/coreclr/vm/threads.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3076,6 +3076,14 @@ class Thread
static void __stdcall RedirectedHandledJITCaseForGCStress();
#endif // defined(HAVE_GCCOVER) && USE_REDIRECT_FOR_GCSTRESS

#ifdef TARGET_X86
// RtlRestoreContext is available on x86, but relatively recently.
// RestoreContextSimulated uses SEH machinery for a similar result on legacy OS-es.
// This function should not be used on new OS-es as the pattern is not
// guaranteed to continue working in the future.
static void RestoreContextSimulated(Thread* pThread, CONTEXT* pCtx, void* pFrame, DWORD dwLastError);
#endif

friend void CPFH_AdjustContextForThreadSuspensionRace(T_CONTEXT *pContext, Thread *pThread);
#endif // FEATURE_HIJACK && !TARGET_UNIX

Expand Down
270 changes: 126 additions & 144 deletions src/coreclr/vm/threadsuspend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1948,6 +1948,9 @@ typedef BOOL(WINAPI* PINITIALIZECONTEXT2)(PVOID Buffer, DWORD ContextFlags, PCON
PINITIALIZECONTEXT2 pfnInitializeContext2 = NULL;

#ifdef TARGET_X86
typedef VOID(__cdecl* PRTLRESTORECONTEXT)(PCONTEXT ContextRecord, struct _EXCEPTION_RECORD* ExceptionRecord);
PRTLRESTORECONTEXT pfnRtlRestoreContext = NULL;

#define CONTEXT_COMPLETE (CONTEXT_FULL | CONTEXT_FLOATING_POINT | \
CONTEXT_DEBUG_REGISTERS | CONTEXT_EXTENDED_REGISTERS | CONTEXT_EXCEPTION_REQUEST)
#else
Expand All @@ -1967,6 +1970,14 @@ CONTEXT* AllocateOSContextHelper(BYTE** contextBuffer)
pfnInitializeContext2 = (PINITIALIZECONTEXT2)GetProcAddress(hm, "InitializeContext2");
}

#ifdef TARGET_X86
if (pfnRtlRestoreContext == NULL)
{
HMODULE hm = GetModuleHandleW(_T("ntdll.dll"));
pfnRtlRestoreContext = (PRTLRESTORECONTEXT)GetProcAddress(hm, "RtlRestoreContext");
}
#endif //TARGET_X86

// Determine if the processor supports AVX so we could
// retrieve extended registers
DWORD64 FeatureMask = GetEnabledXStateFeatures();
Expand Down Expand Up @@ -2515,18 +2526,18 @@ void RedirectedThreadFrame::ExceptionUnwind()
int RedirectedHandledJITCaseExceptionFilter(
PEXCEPTION_POINTERS pExcepPtrs, // Exception data
RedirectedThreadFrame *pFrame, // Frame on stack
BOOL fDone, // Whether redirect completed without exception
CONTEXT *pCtx) // Saved context
CONTEXT *pCtx, // Saved context
DWORD dwLastError) // saved last error
{
// !!! Do not use a non-static contract here.
// !!! Contract may insert an exception handling record.
// !!! This function assumes that GetCurrentSEHRecord() returns the exception record set up in
// !!! Thread::RedirectedHandledJITCase
// !!! Thread::RestoreContextSimulated
//
// !!! Do not use an object with dtor, since it injects a fs:0 entry.
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_GC_TRIGGERS;
STATIC_CONTRACT_MODE_ANY;
STATIC_CONTRACT_MODE_COOPERATIVE;

if (pExcepPtrs->ExceptionRecord->ExceptionCode == STATUS_STACK_OVERFLOW)
{
Expand All @@ -2535,48 +2546,18 @@ int RedirectedHandledJITCaseExceptionFilter(

// Get the thread handle
Thread *pThread = GetThread();

STRESS_LOG2(LF_SYNC, LL_INFO100, "In RedirectedHandledJITCaseExceptionFilter fDone = %d pFrame = %p\n", fDone, pFrame);

// If we get here via COM+ exception, gc-mode is unknown. We need it to
// be cooperative for this function.
GCX_COOP_NO_DTOR();

// If the exception was due to the called client, then we need to figure out if it
// is an exception that can be eaten or if it needs to be handled elsewhere.
if (!fDone)
{
if (pExcepPtrs->ExceptionRecord->ExceptionFlags & EXCEPTION_NONCONTINUABLE)
{
return (EXCEPTION_CONTINUE_SEARCH);
}

// Get the latest thrown object
OBJECTREF throwable = CLRException::GetThrowableFromExceptionRecord(pExcepPtrs->ExceptionRecord);

// If this is an uncatchable exception, then let the exception be handled elsewhere
if (IsUncatchable(&throwable))
{
pThread->EnablePreemptiveGC();
return (EXCEPTION_CONTINUE_SEARCH);
}
}
#ifdef _DEBUG
else
{
_ASSERTE(pExcepPtrs->ExceptionRecord->ExceptionCode == EXCEPTION_HIJACK);
}
#endif
STRESS_LOG1(LF_SYNC, LL_INFO100, "In RedirectedHandledJITCaseExceptionFilter pFrame = %p\n", pFrame);
_ASSERTE(pExcepPtrs->ExceptionRecord->ExceptionCode == EXCEPTION_HIJACK);

// Unlink the frame in preparation for resuming in managed code
pFrame->Pop();

// Copy the saved context record into the EH context;
// NB: cannot use ReplaceExceptionContextRecord here.
// these contexts may contain extended registers and may have different format
// for reasons such as alignment or context compaction
// Copy everything in the saved context record into the EH context.
// Historically the EH context has enough space for every enabled context feature.
// That may not hold for the future features beyond AVX, but this codepath is
// supposed to be used only on OSes that do not have RtlRestoreContext.
CONTEXT* pTarget = pExcepPtrs->ContextRecord;
if (!CopyContext(pTarget, pTarget->ContextFlags, pCtx))
if (!CopyContext(pTarget, pCtx->ContextFlags, pCtx))
{
STRESS_LOG1(LF_SYNC, LL_ERROR, "ERROR: Could not set context record, lastError = 0x%x\n", GetLastError());
EEPOLICY_HANDLE_FATAL_ERROR(COR_E_EXECUTIONENGINE);
Expand Down Expand Up @@ -2610,6 +2591,9 @@ int RedirectedHandledJITCaseExceptionFilter(
// Register the special OS handler as the top handler with the OS
SetCurrentSEHRecord(pCurSEH);

// restore last error
SetLastError(dwLastError);

// Resume execution at point where thread was originally redirected
return (EXCEPTION_CONTINUE_EXECUTION);
}
Expand Down Expand Up @@ -2642,6 +2626,38 @@ extern "C" PCONTEXT __stdcall GetCurrentSavedRedirectContext()
return pContext;
}

#ifdef TARGET_X86

void Thread::RestoreContextSimulated(Thread* pThread, CONTEXT* pCtx, void* pFrame, DWORD dwLastError)
{
pThread->HandleThreadAbort(); // Might throw an exception.

// A counter to avoid a nasty case where an
// up-stack filter throws another exception
// causing our filter to be run again for
// some unrelated exception.
int filter_count = 0;

__try
{
// Save the instruction pointer where we redirected last. This does not race with the check
// against this variable in HandledJitCase because the GC will not attempt to redirect the
// thread until the instruction pointer of this thread is back in managed code.
pThread->m_LastRedirectIP = GetIP(pCtx);
pThread->m_SpinCount = 0;

RaiseException(EXCEPTION_HIJACK, 0, 0, NULL);
}
__except (++filter_count == 1
? RedirectedHandledJITCaseExceptionFilter(GetExceptionInformation(), (RedirectedThreadFrame*)pFrame, pCtx, dwLastError)
: EXCEPTION_CONTINUE_SEARCH)
{
_ASSERTE(!"Reached body of __except in Thread::RedirectedHandledJITCase");
}
}

#endif // TARGET_X86

void __stdcall Thread::RedirectedHandledJITCase(RedirectReason reason)
{
STATIC_CONTRACT_THROWS;
Expand All @@ -2665,140 +2681,106 @@ void __stdcall Thread::RedirectedHandledJITCase(RedirectReason reason)

STRESS_LOG5(LF_SYNC, LL_INFO1000, "In RedirectedHandledJITcase reason 0x%x pFrame = %p pc = %p sp = %p fp = %p", reason, &frame, GetIP(pCtx), GetSP(pCtx), GetFP(pCtx));

#ifdef TARGET_X86
// This will indicate to the exception filter whether or not the exception is caused
// by us or the client.
BOOL fDone = FALSE;
int filter_count = 0; // A counter to avoid a nasty case where an
// up-stack filter throws another exception
// causing our filter to be run again for
// some unrelated exception.

__try
#endif // TARGET_X86
{
// Make sure this thread doesn't reuse the context memory.
pThread->MarkRedirectContextInUse(pCtx);
// Make sure this thread doesn't reuse the context memory.
pThread->MarkRedirectContextInUse(pCtx);

// Link in the frame
frame.Push();
// Link in the frame
frame.Push();

#if defined(HAVE_GCCOVER) && defined(USE_REDIRECT_FOR_GCSTRESS) // GCCOVER
if (reason == RedirectReason_GCStress)
{
_ASSERTE(pThread->PreemptiveGCDisabledOther());
DoGcStress(frame.GetContext(), NULL);
}
else
if (reason == RedirectReason_GCStress)
{
_ASSERTE(pThread->PreemptiveGCDisabledOther());
DoGcStress(frame.GetContext(), NULL);
}
else
#endif // HAVE_GCCOVER && USE_REDIRECT_FOR_GCSTRESS
{
// Enable PGC before calling out to the client to allow runtime suspend to finish
GCX_PREEMP_NO_DTOR();
{
_ASSERTE(reason == RedirectReason_GCSuspension ||
reason == RedirectReason_DebugSuspension ||
reason == RedirectReason_UserSuspension);

// Notify the interface of the pending suspension
switch (reason) {
case RedirectReason_GCSuspension:
break;
case RedirectReason_DebugSuspension:
break;
case RedirectReason_UserSuspension:
// Do nothing;
break;
default:
_ASSERTE(!"Invalid redirect reason");
break;
}
// Actual self-suspension.
// Leave and reenter COOP mode to be trapped on the way back.
GCX_PREEMP_NO_DTOR();
GCX_PREEMP_NO_DTOR_END();
}

// Disable preemptive GC so we can unlink the frame
GCX_PREEMP_NO_DTOR_END();
}
// Once we get here the suspension is over!
// We will restore the state as it was at the point of redirection
// and continue normal execution.

#ifdef TARGET_X86
pThread->HandleThreadAbort(); // Might throw an exception.

// Indicate that the call to the service went without an exception, and that
// we're raising our own exception to resume the thread to where it was
// redirected from
fDone = TRUE;

// Save the instruction pointer where we redirected last. This does not race with the check
// against this variable in HandledJitCase because the GC will not attempt to redirect the
// thread until the instruction pointer of this thread is back in managed code.
pThread->m_LastRedirectIP = GetIP(pCtx);
pThread->m_SpinCount = 0;

RaiseException(EXCEPTION_HIJACK, 0, 0, NULL);
if (!pfnRtlRestoreContext)
{
RestoreContextSimulated(pThread, pCtx, &frame, dwLastError);

#else // TARGET_X86
// we never return to the caller.
__UNREACHABLE();
}
#endif // TARGET_X86

#if defined(HAVE_GCCOVER) && defined(USE_REDIRECT_FOR_GCSTRESS) // GCCOVER
//
// If GCStress interrupts an IL stub or inlined p/invoke while it's running in preemptive mode, it switches the mode to
// cooperative - but we will resume to preemptive below. We should not trigger an abort in that case, as it will fail
// due to the GC mode.
//
if (!pThread->m_fPreemptiveGCDisabledForGCStress)
//
// If GCStress interrupts an IL stub or inlined p/invoke while it's running in preemptive mode, it switches the mode to
// cooperative - but we will resume to preemptive below. We should not trigger an abort in that case, as it will fail
// due to the GC mode.
//
if (!pThread->m_fPreemptiveGCDisabledForGCStress)
#endif
{
{

UINT_PTR uAbortAddr;
UINT_PTR uResumePC = (UINT_PTR)GetIP(pCtx);
CopyOSContext(pThread->m_OSContext, pCtx);
uAbortAddr = (UINT_PTR)COMPlusCheckForAbort();
if (uAbortAddr)
{
LOG((LF_EH, LL_INFO100, "thread abort in progress, resuming thread under control... (handled jit case)\n"));
UINT_PTR uAbortAddr;
UINT_PTR uResumePC = (UINT_PTR)GetIP(pCtx);
CopyOSContext(pThread->m_OSContext, pCtx);
uAbortAddr = (UINT_PTR)COMPlusCheckForAbort();
if (uAbortAddr)
{
LOG((LF_EH, LL_INFO100, "thread abort in progress, resuming thread under control... (handled jit case)\n"));

CONSISTENCY_CHECK(CheckPointer(pCtx));
CONSISTENCY_CHECK(CheckPointer(pCtx));

STRESS_LOG1(LF_EH, LL_INFO10, "resume under control: ip: %p (handled jit case)\n", uResumePC);
STRESS_LOG1(LF_EH, LL_INFO10, "resume under control: ip: %p (handled jit case)\n", uResumePC);

SetIP(pThread->m_OSContext, uResumePC);
SetIP(pThread->m_OSContext, uResumePC);

#if defined(TARGET_ARM)
// Save the original resume PC in Lr
pCtx->Lr = uResumePC;
// Save the original resume PC in Lr
pCtx->Lr = uResumePC;

// Since we have set a new IP, we have to clear conditional execution flags too.
ClearITState(pThread->m_OSContext);
// Since we have set a new IP, we have to clear conditional execution flags too.
ClearITState(pThread->m_OSContext);
#endif // TARGET_ARM

SetIP(pCtx, uAbortAddr);
}
SetIP(pCtx, uAbortAddr);
}
}

// Unlink the frame in preparation for resuming in managed code
frame.Pop();
// Unlink the frame in preparation for resuming in managed code
frame.Pop();

{
// Allow future use of the context
pThread->UnmarkRedirectContextInUse(pCtx);
// Allow future use of the context
pThread->UnmarkRedirectContextInUse(pCtx);

#if defined(HAVE_GCCOVER) && defined(USE_REDIRECT_FOR_GCSTRESS) // GCCOVER
if (pThread->m_fPreemptiveGCDisabledForGCStress)
{
pThread->EnablePreemptiveGC();
pThread->m_fPreemptiveGCDisabledForGCStress = false;
}
if (pThread->m_fPreemptiveGCDisabledForGCStress)
{
pThread->EnablePreemptiveGC();
pThread->m_fPreemptiveGCDisabledForGCStress = false;
}
#endif

LOG((LF_SYNC, LL_INFO1000, "Resuming execution with RtlRestoreContext\n"));

SetLastError(dwLastError); // END_PRESERVE_LAST_ERROR
LOG((LF_SYNC, LL_INFO1000, "Resuming execution with RtlRestoreContext\n"));
SetLastError(dwLastError); // END_PRESERVE_LAST_ERROR

RtlRestoreContext(pCtx, NULL);
}
#endif // TARGET_X86
}
#ifdef TARGET_X86
__except (++filter_count == 1
? RedirectedHandledJITCaseExceptionFilter(GetExceptionInformation(), &frame, fDone, pCtx)
: EXCEPTION_CONTINUE_SEARCH)
{
_ASSERTE(!"Reached body of __except in Thread::RedirectedHandledJITCase");
}
pfnRtlRestoreContext(pCtx, NULL);
#else
RtlRestoreContext(pCtx, NULL);
#endif

#endif // TARGET_X86
// we never return to the caller.
__UNREACHABLE();
}

//****************************************************************************************
Expand Down