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Fix for stress failure when adjusting effective IP while stackwalking may put it on a wrong instruction. #100376

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merged 3 commits into from
Mar 30, 2024
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Fix for stress failure when adjusting effective IP while stackwalking may put it on a wrong instruction. #100376

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b4acf8b
fix
VSadov Mar 27, 2024
6b91f33
same change for x86 and NativeAOT, get rid of ICodeManagerFlags::Abor…
VSadov Mar 28, 2024
d330b3b
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VSadov Mar 29, 2024
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2 changes: 1 addition & 1 deletion src/coreclr/inc/eetwain.h
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Expand Up @@ -89,7 +89,7 @@ enum ICodeManagerFlags
ExecutionAborted = 0x0002, // execution of this function has been aborted
// (i.e. it will not continue execution at the
// current location)
AbortingCall = 0x0004, // The current call will never return
// unused = 0x0004, // was AbortingCall
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UpdateAllRegs = 0x0008, // update full register set
CodeAltered = 0x0010, // code of that function might be altered
// (e.g. by debugger), need to call EE
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2 changes: 1 addition & 1 deletion src/coreclr/inc/gcinfodecoder.h
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Expand Up @@ -179,7 +179,7 @@ enum ICodeManagerFlags
ExecutionAborted = 0x0002, // execution of this function has been aborted
// (i.e. it will not continue execution at the
// current location)
AbortingCall = 0x0004, // The current call will never return
// unused = 0x0004, // was AbortingCall
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ParentOfFuncletStackFrame
= 0x0040, // A funclet for this frame was previously reported

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18 changes: 17 additions & 1 deletion src/coreclr/jit/codegenlinear.cpp
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Expand Up @@ -712,7 +712,9 @@ void CodeGen::genCodeForBBlist()

if ((call != nullptr) && (call->gtOper == GT_CALL))
{
if ((call->AsCall()->gtCallMoreFlags & GTF_CALL_M_DOES_NOT_RETURN) != 0)
if ((call->AsCall()->gtCallMoreFlags & GTF_CALL_M_DOES_NOT_RETURN) != 0 ||
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Can we extend GenTreeCall::IsNoReturn() to cover the helper case too? Either by setting the no return flag when the helper is set, or by putting this check there?

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@VSadov VSadov Mar 28, 2024 •
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I have tried, naively, to put

    if (s_helperCallProperties.AlwaysThrow((CorInfoHelpFunc)helper))
    {
        result->gtCallMoreFlags |= GTF_CALL_M_DOES_NOT_RETURN;
    }

in gtNewHelperCallNode

, but that resulted in

  Assertion failed 'call->gtCallType == CT_USER_FUNC' in 'System.ModuleHandle:ResolveFieldHandle(int,System.RuntimeTypeHandle[],System.Run
  timeTypeHandle[]):System.RuntimeFieldHandle:this' during 'Merge throw blocks' (IL size 283; hash 0x040825d3; FullOpts)

        if (!call->IsNoReturn())
        {
            continue;
        }

        // Sanity check -- only user funcs should be marked do not return
        assert(call->gtCallType == CT_USER_FUNC);

I could not easily tell if the assert is just an observation, that could be relaxed or indeed guarding some assumptions made in the code, so I did not continue on that path.

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Commenting out that assert leads to others:

  Assert failure(PID 35472 [0x00008a90], Thread: 41468 [0xa1fc]): Assertion failed 'updateCount < optNoReturnCallCount' in 'System.Tests.S
  tringComparerTests:Create_CreatesValidComparer():this' during 'Merge throw blocks' (IL size 543; hash 0xc45bc068; FullOpts)

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I think I'd prefer entering an issue on this.

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Makes sense, looks like there are some assumptions in the throw helper merging to sort out.

((call->AsCall()->gtCallType == CT_HELPER) &&
Compiler::s_helperCallProperties.AlwaysThrow(call->AsCall()->GetHelperNum())))
{
instGen(INS_BREAKPOINT); // This should never get executed
}
Expand Down Expand Up @@ -756,6 +758,20 @@ void CodeGen::genCodeForBBlist()

case BBJ_ALWAYS:
{
GenTree* call = block->lastNode();
if ((call != nullptr) && (call->gtOper == GT_CALL))
{
if ((call->AsCall()->gtCallMoreFlags & GTF_CALL_M_DOES_NOT_RETURN) != 0 ||
((call->AsCall()->gtCallType == CT_HELPER) &&
Compiler::s_helperCallProperties.AlwaysThrow(call->AsCall()->GetHelperNum())))
{
// NOTE: We should probably never see a BBJ_ALWAYS block ending with a throw in a first place.
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I take it you did see such cases? Can you open an issues for us to follow-up and switch them over to BBJ_THROWs?

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Note this might largely clean itself up by adding the logic to IsNoReturn, though there is one place in morph where we still check the flag rather than the property.

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@VSadov VSadov Mar 28, 2024 •
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I take it you did see such cases?

Yes, I wanted this to be an assert, so it would not happen by accident in the future. To my surprise, the assert was triggered by existing code.

// If that is fixed, this condition can be just an assert.
// For the reasons why we insert a BP, see the similar code in "case BBJ_THROW:" above.
instGen(INS_BREAKPOINT); // This should never get executed
}
}

// If this block jumps to the next one, we might be able to skip emitting the jump
if (block->CanRemoveJumpToNext(compiler))
{
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13 changes: 5 additions & 8 deletions src/coreclr/nativeaot/Runtime/unix/UnixNativeCodeManager.cpp
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Expand Up @@ -212,14 +212,11 @@ void UnixNativeCodeManager::EnumGcRefs(MethodInfo * pMethodInfo,
ASSERT(((uintptr_t)codeOffset & 1) == 0);
#endif

if (!isActiveStackFrame)
bool executionAborted = ((UnixNativeMethodInfo*)pMethodInfo)->executionAborted;

if (!isActiveStackFrame && !executionAborted)
{
// If we are not in the active method, we are currently pointing
// to the return address. That may not be reachable after a call (if call does not return)
// or reachable via a jump and thus have a different live set.
// Therefore we simply adjust the offset to inside of call instruction.
// NOTE: The GcInfoDecoder depends on this; if you change it, you must
// revisit the GcInfoEncoder/Decoder
// the reasons for this adjustment are explained in EECodeManager::EnumGcRefs
codeOffset--;
}

Expand All @@ -230,7 +227,7 @@ void UnixNativeCodeManager::EnumGcRefs(MethodInfo * pMethodInfo,
);

ICodeManagerFlags flags = (ICodeManagerFlags)0;
if (((UnixNativeMethodInfo*)pMethodInfo)->executionAborted)
if (executionAborted)
flags = ICodeManagerFlags::ExecutionAborted;

if (IsFilter(pMethodInfo))
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13 changes: 5 additions & 8 deletions src/coreclr/nativeaot/Runtime/windows/CoffNativeCodeManager.cpp
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Expand Up @@ -435,8 +435,10 @@ void CoffNativeCodeManager::EnumGcRefs(MethodInfo * pMethodInfo,
PTR_uint8_t gcInfo;
uint32_t codeOffset = GetCodeOffset(pMethodInfo, safePointAddress, &gcInfo);

bool executionAborted = ((CoffNativeMethodInfo *)pMethodInfo)->executionAborted;

ICodeManagerFlags flags = (ICodeManagerFlags)0;
if (((CoffNativeMethodInfo *)pMethodInfo)->executionAborted)
if (executionAborted)
flags = ICodeManagerFlags::ExecutionAborted;

if (IsFilter(pMethodInfo))
Expand All @@ -446,14 +448,9 @@ void CoffNativeCodeManager::EnumGcRefs(MethodInfo * pMethodInfo,
flags = (ICodeManagerFlags)(flags | ICodeManagerFlags::ActiveStackFrame);

#ifdef USE_GC_INFO_DECODER
if (!isActiveStackFrame)
if (!isActiveStackFrame && !executionAborted)
{
// If we are not in the active method, we are currently pointing
// to the return address. That may not be reachable after a call (if call does not return)
// or reachable via a jump and thus have a different live set.
// Therefore we simply adjust the offset to inside of call instruction.
// NOTE: The GcInfoDecoder depends on this; if you change it, you must
// revisit the GcInfoEncoder/Decoder
// the reasons for this adjustment are explained in EECodeManager::EnumGcRefs
codeOffset--;
}

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20 changes: 9 additions & 11 deletions src/coreclr/vm/eetwain.cpp
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Expand Up @@ -1466,17 +1466,15 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY pRD,
}
else
{
/* However if ExecutionAborted, then this must be one of the
* ExceptionFrames. Handle accordingly
*/
_ASSERTE(!(flags & AbortingCall) || !(flags & ActiveStackFrame));

if (flags & AbortingCall)
{
curOffs--;
LOG((LF_GCINFO, LL_INFO1000, "Adjusted GC reporting offset due to flags ExecutionAborted && AbortingCall. Now reporting GC refs for %s at offset %04x.\n",
methodName, curOffs));
}
// Since we are aborting execution, we are either in a frame that actually faulted or in a throwing call.
// * We do not need to adjust in a leaf
// * A throwing call will have unreachable <brk> after it, thus GC info is the same as before the call.
//
// Either way we do not need to adjust.

// NOTE: only fully interruptible methods may need to report anything here as without
// exception handling all current local variables are already unreachable.
// EnumerateLiveSlots will shortcircuit the partially interruptible case just a bit later.
}

// Check if we have been given an override value for relOffset
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8 changes: 1 addition & 7 deletions src/coreclr/vm/gc_unwind_x86.inl
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Expand Up @@ -3686,13 +3686,7 @@ bool EnumGcRefsX86(PREGDISPLAY pContext,
}
else
{
/* However if ExecutionAborted, then this must be one of the
* ExceptionFrames. Handle accordingly
*/
_ASSERTE(!(flags & AbortingCall) || !(flags & ActiveStackFrame));

newCurOffs = (flags & AbortingCall) ? curOffs-1 // inside "call"
: curOffs; // at faulting instr, or start of "try"
newCurOffs = curOffs;
}

ptrOffs = 0;
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1 change: 0 additions & 1 deletion src/coreclr/vm/stackwalk.h
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Expand Up @@ -284,7 +284,6 @@ class CrawlFrame
if (!HasFaulted() && !IsIPadjusted())
{
_ASSERTE(!(flags & ActiveStackFrame));
flags |= AbortingCall;
}
}

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