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Adjust IP after an AV during an STEP with FEATURE_EMULATE_SINGLESTEP enabled #105633

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Merged
merged 4 commits into from
Jul 31, 2024
Merged

Adjust IP after an AV during an STEP with FEATURE_EMULATE_SINGLESTEP enabled #105633

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d6f6d7f
Trying to fix step in a line that will throw an AV
thaystg Jul 29, 2024
233ea19
Fix build
thaystg Jul 29, 2024
91e4b78
Addressing Noah's comments.
Jul 30, 2024
1dfd383
Removing changes not needed anymore.
thaystg Jul 30, 2024
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2 changes: 1 addition & 1 deletion src/coreclr/debug/ee/controller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3232,7 +3232,7 @@ void DebuggerController::UnapplyTraceFlag(Thread *thread)
// so there should be nothing to do. However, we still assert b/c we want to know how
// we'd actually hit this.
// @todo - is there a path if TriggerUnwind() calls DisableAll(). But why would
CONSISTENCY_CHECK_MSGF(false, ("How did we get here?. thread=%p\n", thread));
//CONSISTENCY_CHECK_MSGF(false, ("How did we get here?. thread=%p\n", thread)); it can be caused in a scenario where we are stepping and an AV is thrown
LOG((LF_CORDB,LL_INFO1000, "DC::UnapplyTraceFlag couldn't get context.\n"));
return;
}
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11 changes: 11 additions & 0 deletions src/coreclr/vm/exceptionhandling.cpp
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Expand Up @@ -5426,6 +5426,17 @@ BOOL IsSafeToCallExecutionManager()

BOOL IsSafeToHandleHardwareException(PCONTEXT contextRecord, PEXCEPTION_RECORD exceptionRecord)
{
#ifdef FEATURE_EMULATE_SINGLESTEP
Thread *pThread = GetThreadNULLOk();
if (pThread && pThread->IsSingleStepEnabled() &&
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@noahfalk noahfalk Jul 30, 2024

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Any reason why we only invoke pThread->HandleSingleStep() in some cases and not others? Could we do something like this in IsSafeToHandleHardwareException() and remove the HandleSingleStep call from HandleHardwareException?

#ifdef FEATURE_EMULATE_SINGLESTEP
Thread *pThread = GetThreadNULLOk();
if (pThread != NULL && g_pDebugInterface != NULL)
{
    HandleSingleStep(contextRecord, exceptionRecord, pThread);
}
#endif

It feels easier to understand if we always invoke it from one place rather than conditionally invoke it from two different place.

exceptionRecord->ExceptionCode != STATUS_BREAKPOINT &&
exceptionRecord->ExceptionCode != STATUS_SINGLE_STEP &&
exceptionRecord->ExceptionCode != STATUS_STACK_OVERFLOW)
{
pThread->HandleSingleStep(contextRecord, exceptionRecord->ExceptionCode);
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@noahfalk noahfalk Jul 31, 2024

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The updated version of the change looks like it still calls HandleSingleStep from two different places, once here and once over in HandleHardwareException.

I was suggesting that we converge those into a single call here. Is there a reason we need two different calls? If yes it would be great to add a comment saying why we have both, and if not it would be nice to get rid of the HandleHardwareException portion and do it all here.

}
#endif

PCODE controlPc = GetIP(contextRecord);

if (IsIPInWriteBarrierCodeCopy(controlPc))
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