Specialcase active frames in EnumGcRefs

Author: VSadov

src/coreclr/nativeaot/Runtime/ICodeManager.h

@@ -152,7 +152,8 @@ class ICodeManager
     virtual void EnumGcRefs(MethodInfo *    pMethodInfo,
                             PTR_VOID        safePointAddress,
                             REGDISPLAY *    pRegisterSet,
-                            GCEnumContext * hCallback) = 0;
+                            GCEnumContext * hCallback,
+                            bool            isActiveStackFrame) = 0;
 
     virtual bool UnwindStackFrame(MethodInfo *    pMethodInfo,
                                   REGDISPLAY *    pRegisterSet,                     // in/out

src/coreclr/nativeaot/Runtime/StackFrameIterator.cpp

@@ -96,7 +96,7 @@ StackFrameIterator::StackFrameIterator(Thread * pThreadToWalk, PInvokeTransition
 #ifdef FEATURE_SUSPEND_REDIRECTION
     if (pInitialTransitionFrame == REDIRECTED_THREAD_MARKER)
     {
-        InternalInit(pThreadToWalk, pThreadToWalk->GetRedirectionContext(), GcStackWalkFlags);
+        InternalInit(pThreadToWalk, pThreadToWalk->GetRedirectionContext(), GcStackWalkFlags | ActiveStackFrame);
     }
     else
 #endif
@@ -1407,7 +1407,7 @@ void StackFrameIterator::NextInternal()
 {
 UnwindOutOfCurrentManagedFrame:
     ASSERT(m_dwFlags & MethodStateCalculated);
-    m_dwFlags &= ~(ExCollide|MethodStateCalculated|UnwoundReversePInvoke);
+    m_dwFlags &= ~(ExCollide|MethodStateCalculated|UnwoundReversePInvoke|ActiveStackFrame);
     ASSERT(IsValid());
 
     m_pHijackedReturnValue = NULL;
@@ -1757,6 +1757,12 @@ MethodInfo * StackFrameIterator::GetMethodInfo()
     return &m_methodInfo;
 }
 
+bool StackFrameIterator::IsActiveStackFrame()
+{
+    ASSERT(IsValid());
+    return (m_dwFlags & ActiveStackFrame) != 0;
+}
+
 #ifdef DACCESS_COMPILE
 #define FAILFAST_OR_DAC_RETURN_FALSE(x) if(!(x)) return false;
 #else

src/coreclr/nativeaot/Runtime/StackFrameIterator.h

@@ -43,6 +43,7 @@ class StackFrameIterator
     REGDISPLAY *     GetRegisterSet();
     PTR_ICodeManager GetCodeManager();
     MethodInfo *     GetMethodInfo();
+    bool             IsActiveStackFrame();
     bool             GetHijackedReturnValueLocation(PTR_RtuObjectRef * pLocation, GCRefKind * pKind);
     void             SetControlPC(PTR_VOID controlPC);
 
@@ -138,6 +139,9 @@ class StackFrameIterator
         // This is a state returned by Next() which indicates that we just unwound a reverse pinvoke method
         UnwoundReversePInvoke = 0x20,
 
+        // The thread was interrupted in the current frame at the current IP by a signal, SuspendThread or similar.
+        ActiveStackFrame = 0x40,
+
         GcStackWalkFlags = (CollapseFunclets | RemapHardwareFaultsToSafePoint),
         EHStackWalkFlags = ApplyReturnAddressAdjustment,
         StackTraceStackWalkFlags = GcStackWalkFlags

src/coreclr/nativeaot/Runtime/gcrhenv.cpp

@@ -515,7 +515,8 @@ void RedhawkGCInterface::EnumGcRefs(ICodeManager * pCodeManager,
                                     PTR_VOID safePointAddress,
                                     REGDISPLAY * pRegisterSet,
                                     void * pfnEnumCallback,
-                                    void * pvCallbackData)
+                                    void * pvCallbackData,
+                                    bool   isActiveStackFrame)
 {
     EnumGcRefContext ctx;
     ctx.pCallback = EnumGcRefsCallback;
@@ -526,7 +527,8 @@ void RedhawkGCInterface::EnumGcRefs(ICodeManager * pCodeManager,
     pCodeManager->EnumGcRefs(pMethodInfo,
                              safePointAddress,
                              pRegisterSet,
-                             &ctx);
+                             &ctx,
+                             isActiveStackFrame);
 }
 
 // static

src/coreclr/nativeaot/Runtime/gcrhinterface.h

@@ -120,7 +120,8 @@ class RedhawkGCInterface
                            PTR_VOID safePointAddress,
                            REGDISPLAY * pRegisterSet,
                            void * pfnEnumCallback,
-                           void * pvCallbackData);
+                           void * pvCallbackData,
+                           bool   isActiveStackFrame);
 
     static void EnumGcRefsInRegionConservatively(PTR_RtuObjectRef pLowerBound,
                                                  PTR_RtuObjectRef pUpperBound,

src/coreclr/nativeaot/Runtime/thread.cpp

@@ -533,7 +533,8 @@ void Thread::GcScanRootsWorker(void * pfnEnumCallback, void * pvCallbackData, St
                                                frameIterator.GetEffectiveSafePointAddress(),
                                                frameIterator.GetRegisterSet(),
                                                pfnEnumCallback,
-                                               pvCallbackData);
+                                               pvCallbackData,
+                                               frameIterator.IsActiveStackFrame());
             }
 
             // Each enumerated frame (including the first one) may have an associated stack range we need to

src/coreclr/nativeaot/Runtime/unix/UnixNativeCodeManager.cpp

@@ -136,7 +136,8 @@ bool UnixNativeCodeManager::IsSafePoint(PTR_VOID pvAddress)
 void UnixNativeCodeManager::EnumGcRefs(MethodInfo *    pMethodInfo,
                                        PTR_VOID        safePointAddress,
                                        REGDISPLAY *    pRegisterSet,
-                                       GCEnumContext * hCallback)
+                                       GCEnumContext * hCallback,
+                                       bool            isActiveStackFrame)
 {
     UnixNativeMethodInfo * pNativeMethodInfo = (UnixNativeMethodInfo *)pMethodInfo;
 
@@ -155,7 +156,7 @@ void UnixNativeCodeManager::EnumGcRefs(MethodInfo *    pMethodInfo,
     GcInfoDecoder decoder(
         GCInfoToken(p),
         GcInfoDecoderFlags(DECODE_GC_LIFETIMES | DECODE_SECURITY_OBJECT | DECODE_VARARG),
-        codeOffset - 1 // TODO: Is this adjustment correct?
+        codeOffset - 1 // TODO: isActiveStackFrame
     );
 
     ICodeManagerFlags flags = (ICodeManagerFlags)0;

src/coreclr/nativeaot/Runtime/unix/UnixNativeCodeManager.h

@@ -39,7 +39,8 @@ class UnixNativeCodeManager : public ICodeManager
     void EnumGcRefs(MethodInfo *    pMethodInfo,
                     PTR_VOID        safePointAddress,
                     REGDISPLAY *    pRegisterSet,
-                    GCEnumContext * hCallback);
+                    GCEnumContext * hCallback,
+                    bool            isActiveStackFrame);
 
     bool UnwindStackFrame(MethodInfo *    pMethodInfo,
                           REGDISPLAY *    pRegisterSet,                 // in/out

src/coreclr/nativeaot/Runtime/windows/CoffNativeCodeManager.cpp

@@ -379,11 +379,23 @@ bool CoffNativeCodeManager::IsSafePoint(PTR_VOID pvAddress)
 void CoffNativeCodeManager::EnumGcRefs(MethodInfo *    pMethodInfo,
                                        PTR_VOID        safePointAddress,
                                        REGDISPLAY *    pRegisterSet,
-                                       GCEnumContext * hCallback)
+                                       GCEnumContext * hCallback,
+                                       bool            isActiveStackFrame)
 {
     PTR_UInt8 gcInfo;
     uint32_t codeOffset = GetCodeOffset(pMethodInfo, safePointAddress, &gcInfo);
 
+    if (!isActiveStackFrame)
+    {
+        // 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
+        codeOffset--;
+    }
+
     GcInfoDecoder decoder(
         GCInfoToken(gcInfo),
         GcInfoDecoderFlags(DECODE_GC_LIFETIMES | DECODE_SECURITY_OBJECT | DECODE_VARARG),
@@ -393,12 +405,16 @@ void CoffNativeCodeManager::EnumGcRefs(MethodInfo *    pMethodInfo,
     ICodeManagerFlags flags = (ICodeManagerFlags)0;
     if (((CoffNativeMethodInfo *)pMethodInfo)->executionAborted)
         flags = ICodeManagerFlags::ExecutionAborted;
+
     if (IsFilter(pMethodInfo))
         flags = (ICodeManagerFlags)(flags | ICodeManagerFlags::NoReportUntracked);
 
+    if (isActiveStackFrame)
+        flags = (ICodeManagerFlags)(flags | ICodeManagerFlags::ActiveStackFrame);
+
     if (!decoder.EnumerateLiveSlots(
         pRegisterSet,
-        false /* reportScratchSlots */,
+        isActiveStackFrame /* reportScratchSlots */,
         flags,
         hCallback->pCallback,
         hCallback

src/coreclr/nativeaot/Runtime/windows/CoffNativeCodeManager.h

@@ -77,7 +77,8 @@ class CoffNativeCodeManager : public ICodeManager
     void EnumGcRefs(MethodInfo *    pMethodInfo,
                     PTR_VOID        safePointAddress,
                     REGDISPLAY *    pRegisterSet,
-                    GCEnumContext * hCallback);
+                    GCEnumContext * hCallback,
+                    bool            isActiveStackFrame);
 
     bool UnwindStackFrame(MethodInfo *    pMethodInfo,
                           REGDISPLAY *    pRegisterSet,                 // in/out