[x86/Linux] Fix assert in HelperMethodFrame::UpdateRegDisplay (#14235)

In some cases during execution of the SOS command 'clrstack -i'
portability assert in HelperMethodFrame::UpdateRegDisplay occurs.
This patch removes this assert and adds corresponding implementation.

1 files changed, 24 insertions, 1 deletions

diff --git a/src/vm/i386/cgenx86.cpp b/src/vm/i386/cgenx86.cpp
index 9b8960a6eb..3b523c9c28 100644
--- a/src/vm/i386/cgenx86.cpp
+++ b/src/vm/i386/cgenx86.cpp
@@ -378,7 +378,30 @@ void HelperMethodFrame::UpdateRegDisplay(const PREGDISPLAY pRD)
     pRD->IsCallerSPValid      = FALSE;        // Don't add usage of this field.  This is only temporary.
 
 #ifdef DACCESS_COMPILE
-    PORTABILITY_ASSERT("HelperMethodFrame::UpdateRegDisplay");
+    // For DAC, we may get here when the HMF is still uninitialized.
+    // So we may need to unwind here.
+    if (!m_MachState.isValid())
+    {
+        // This allocation throws on OOM.
+        MachState* pUnwoundState = (MachState*)DacAllocHostOnlyInstance(sizeof(*pUnwoundState), true);
+
+        InsureInit(false, pUnwoundState);
+
+        pRD->pCurrentContext->Eip = pRD->ControlPC = pUnwoundState->GetRetAddr();
+        pRD->pCurrentContext->Esp = pRD->SP        = pUnwoundState->esp();
+
+#define CALLEE_SAVED_REGISTER(regname) pRD->pCurrentContext->regname = *((DWORD*) pUnwoundState->p##regname());
+        ENUM_CALLEE_SAVED_REGISTERS();
+#undef CALLEE_SAVED_REGISTER
+
+#define CALLEE_SAVED_REGISTER(regname) pRD->pCurrentContextPointers->regname = (DWORD*) pUnwoundState->p##regname();
+        ENUM_CALLEE_SAVED_REGISTERS();
+#undef CALLEE_SAVED_REGISTER
+
+        ClearRegDisplayArgumentAndScratchRegisters(pRD);
+
+        return;
+    }
 #endif // DACCESS_COMPILE
 
     pRD->pCurrentContext->Eip = pRD->ControlPC = m_MachState.GetRetAddr();