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Fix GC hole with collectible assemblies and tailcalls #51315

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Merged
jkotas merged 1 commit into from
Apr 16, 2021
Merged

Fix GC hole with collectible assemblies and tailcalls #51315

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10 changes: 6 additions & 4 deletions ...eclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -318,7 +318,7 @@ public static IntPtr AllocateTypeAssociatedMemory(Type type, int size)
[StackTraceHidden]
private static unsafe void DispatchTailCalls(
IntPtr callersRetAddrSlot,
delegate*<IntPtr, IntPtr, IntPtr*, void> callTarget,
delegate*<IntPtr, IntPtr, PortableTailCallFrame*, void> callTarget,
IntPtr retVal)
{
IntPtr callersRetAddr;
Expand All @@ -332,15 +332,17 @@ private static unsafe void DispatchTailCalls(

PortableTailCallFrame newFrame;
newFrame.Prev = prevFrame;
// GC uses NextCall to keep LoaderAllocator alive after we link it below,
// so we must null it out before that.
newFrame.NextCall = null;

try
{
tls->Frame = &newFrame;

do
{
newFrame.NextCall = null;
callTarget(tls->ArgBuffer, retVal, &newFrame.TailCallAwareReturnAddress);
callTarget(tls->ArgBuffer, retVal, &newFrame);
callTarget = newFrame.NextCall;
} while (callTarget != null);
}
Expand Down Expand Up @@ -503,7 +505,7 @@ internal unsafe struct PortableTailCallFrame
{
public PortableTailCallFrame* Prev;
public IntPtr TailCallAwareReturnAddress;
public delegate*<IntPtr, IntPtr, IntPtr*, void> NextCall;
public delegate*<IntPtr, IntPtr, PortableTailCallFrame*, void> NextCall;
}

[StructLayout(LayoutKind.Sequential)]
Expand Down
17 changes: 16 additions & 1 deletion src/coreclr/vm/gcenv.ee.cpp
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Expand Up @@ -157,7 +157,22 @@ static void ScanStackRoots(Thread * pThread, promote_func* fn, ScanContext* sc)

static void ScanTailCallArgBufferRoots(Thread* pThread, promote_func* fn, ScanContext* sc)
{
TailCallArgBuffer* argBuffer = pThread->GetTailCallTls()->GetArgBuffer();
TailCallTls* tls = pThread->GetTailCallTls();
// Keep loader associated with CallTailCallTarget alive.
if (sc->promotion)
{
#ifndef DACCESS_COMPILE
const PortableTailCallFrame* frame = tls->GetFrame();
if (frame->NextCall != NULL)
{
MethodDesc* pMD = Entry2MethodDesc((PCODE)frame->NextCall, NULL);
if (pMD != NULL)
GcReportLoaderAllocator(fn, sc, pMD->GetLoaderAllocator());
}
#endif
}

TailCallArgBuffer* argBuffer = tls->GetArgBuffer();
if (argBuffer == NULL || argBuffer->GCDesc == NULL)
return;

Expand Down
18 changes: 12 additions & 6 deletions src/coreclr/vm/tailcallhelp.cpp
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Expand Up @@ -465,10 +465,10 @@ MethodDesc* TailCallHelp::CreateCallTargetStub(const TailCallInfo& info)

ILCodeStream* pCode = sl.NewCodeStream(ILStubLinker::kDispatch);

// void CallTarget(void* argBuffer, void* retVal, void** pTailCallAwareRetAddress)
// void CallTarget(void* argBuffer, void* retVal, PortableTailCallFrame* pFrame)
const int ARG_ARG_BUFFER = 0;
const int ARG_RET_VAL = 1;
const int ARG_PTR_TAILCALL_AWARE_RET_ADDR = 2;
const int ARG_PTR_FRAME = 2;

auto emitOffs = [&](UINT offs)
{
Expand All @@ -477,10 +477,16 @@ MethodDesc* TailCallHelp::CreateCallTargetStub(const TailCallInfo& info)
pCode->EmitADD();
};

// *pTailCallAwareRetAddr = NextCallReturnAddress();
pCode->EmitLDARG(ARG_PTR_TAILCALL_AWARE_RET_ADDR);
// pFrame->NextCall = 0;
pCode->EmitLDARG(ARG_PTR_FRAME);
pCode->EmitLDC(0);
pCode->EmitCONV_U();
pCode->EmitSTFLD(FIELD__PORTABLE_TAIL_CALL_FRAME__NEXT_CALL);

// pFrame->TailCallAwareReturnAddress = NextCallReturnAddress();
pCode->EmitLDARG(ARG_PTR_FRAME);
pCode->EmitCALL(METHOD__STUBHELPERS__NEXT_CALL_RETURN_ADDRESS, 0, 1);
pCode->EmitSTIND_I();
pCode->EmitSTFLD(FIELD__PORTABLE_TAIL_CALL_FRAME__TAILCALL_AWARE_RETURN_ADDRESS);

for (COUNT_T i = 0; i < info.ArgBufLayout.Values.GetCount(); i++)
{
Expand Down Expand Up @@ -613,7 +619,7 @@ void TailCallHelp::CreateCallTargetStubSig(const TailCallInfo& info, SigBuilder*
// Return value
sig->AppendElementType(ELEMENT_TYPE_I);

// Pointer to tail call aware return address
// Pointer to tail call frame
sig->AppendElementType(ELEMENT_TYPE_I);

#ifdef _DEBUG
Expand Down