[Linux/x86] Use ebp from current context during unwinding (#26789)

pCurrentContextPointers in REGDISPLAY can contain NULLs so we need to use
ebp value from pCurrentContext. This patch contains following changes:

- GetRegdisplayFP returns ebp from pCurrentContext
- GetRegdisplayFP is used instead of *GetEbpLocation()
- Set##reg##Location also updates register value in pCurrentContext

4 files changed, 21 insertions, 15 deletions

diff --git a/src/debug/ee/i386/x86walker.cpp b/src/debug/ee/i386/x86walker.cpp
index 8b62797484..078bc7ca75 100644
--- a/src/debug/ee/i386/x86walker.cpp
+++ b/src/debug/ee/i386/x86walker.cpp
@@ -307,7 +307,7 @@ DWORD NativeWalker::GetRegisterValue(int registerNumber)
         return m_registers->SP;
         break;
     case 5:
-        return *m_registers->GetEbpLocation();
+        return GetRegdisplayFP(m_registers);
         break;
     case 6:
         return *m_registers->GetEsiLocation();
diff --git a/src/inc/regdisp.h b/src/inc/regdisp.h
index 7875edf653..4a7e57e63d 100644
--- a/src/inc/regdisp.h
+++ b/src/inc/regdisp.h
@@ -95,7 +95,11 @@ struct REGDISPLAY : public REGDISPLAY_BASE {
 
 #define REG_METHODS(reg) \
     inline PDWORD Get##reg##Location(void) { return pCurrentContextPointers->reg; } \
-    inline void   Set##reg##Location(PDWORD p##reg) { pCurrentContextPointers->reg = p##reg; }
+    inline void   Set##reg##Location(PDWORD p##reg) \
+    { \
+        pCurrentContextPointers->reg = p##reg; \
+        pCurrentContext->reg = *p##reg; \
+    }
 
 #endif // WIN64EXCEPTIONS
 
@@ -115,8 +119,11 @@ struct REGDISPLAY : public REGDISPLAY_BASE {
 
 inline TADDR GetRegdisplayFP(REGDISPLAY *display) {
     LIMITED_METHOD_DAC_CONTRACT;
-
+#ifdef WIN64EXCEPTIONS
+    return (TADDR)display->pCurrentContext->Ebp;
+#else
     return (TADDR)*display->GetEbpLocation();
+#endif
 }
 
 inline LPVOID GetRegdisplayFPAddress(REGDISPLAY *display) {
diff --git a/src/vm/eetwain.cpp b/src/vm/eetwain.cpp
index c0eb7aa8d0..c3e49cfe8a 100644
--- a/src/vm/eetwain.cpp
+++ b/src/vm/eetwain.cpp
@@ -3203,7 +3203,7 @@ void EECodeManager::QuickUnwindStackFrame(PREGDISPLAY pRD, StackwalkCacheEntry *
     if (pCacheEntry->fUseEbpAsFrameReg)
     {
         _ASSERTE(pCacheEntry->fUseEbp);
-        TADDR curEBP = (TADDR)*pRD->GetEbpLocation();
+        TADDR curEBP = GetRegdisplayFP(pRD);
 
         // EBP frame, update ESP through EBP, since ESPOffset may vary
         pRD->SetEbpLocation(PTR_DWORD(curEBP));
@@ -3479,7 +3479,7 @@ void UnwindEbpDoubleAlignFrameEpilog(
             unsigned calleeSavedRegsSize = info->savedRegsCountExclFP * sizeof(void*); 
 
             if (!InstructionAlreadyExecuted(offset, info->epilogOffs))
-                ESP = *pContext->GetEbpLocation() - calleeSavedRegsSize;
+                ESP = GetRegdisplayFP(pContext) - calleeSavedRegsSize;
             
             offset = SKIP_LEA_ESP_EBP(-int(calleeSavedRegsSize), epilogBase, offset);
         }
@@ -3508,7 +3508,7 @@ void UnwindEbpDoubleAlignFrameEpilog(
     if (needMovEspEbp)
     {
         if (!InstructionAlreadyExecuted(offset, info->epilogOffs))
-            ESP = *pContext->GetEbpLocation();
+            ESP = GetRegdisplayFP(pContext);
             
         offset = SKIP_MOV_REG_REG(epilogBase, offset);
     }
@@ -3802,7 +3802,7 @@ void UnwindEbpDoubleAlignFrameProlog(
        can be determined using EBP. Since we are still in the prolog,
        we need to know our exact location to determine the callee-saved registers */
        
-    const unsigned curEBP = *pContext->GetEbpLocation();
+    const unsigned curEBP = GetRegdisplayFP(pContext);
     
     if (flags & UpdateAllRegs)
     {        
@@ -3873,8 +3873,8 @@ bool UnwindEbpDoubleAlignFrame(
 
     _ASSERTE(info->ebpFrame || info->doubleAlign);
 
-    const unsigned curESP =  pContext->SP;
-    const unsigned curEBP = *pContext->GetEbpLocation();
+    const unsigned curESP = pContext->SP;
+    const unsigned curEBP = GetRegdisplayFP(pContext);
 
     /* First check if we are in a filter (which is obviously after the prolog) */
 
@@ -4015,7 +4015,6 @@ bool UnwindEbpDoubleAlignFrame(
     /* The caller's saved EBP is pointed to by our EBP */
 
     pContext->SetEbpLocation(PTR_DWORD((TADDR)curEBP));
-
     return true;
 }
 
@@ -4310,8 +4309,8 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY     pContext,
     GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
     unsigned  curOffs = pCodeInfo->GetRelOffset();
 
-    unsigned  EBP     = *pContext->GetEbpLocation();
-    unsigned  ESP     =  pContext->SP;
+    unsigned  EBP     = GetRegdisplayFP(pContext);
+    unsigned  ESP     = pContext->SP;
 
     unsigned  ptrOffs;
 
@@ -5243,7 +5242,7 @@ OBJECTREF* EECodeManager::GetAddrOfSecurityObjectFromCachedInfo(PREGDISPLAY pRD,
     // We pretend that filters are ESP-based methods in UnwindEbpDoubleAlignFrame().
     // Hence we cannot enforce this assert.
     // _ASSERTE(stackwalkCacheUnwindInfo->fUseEbpAsFrameReg);
-    return (OBJECTREF *) (size_t) (*pRD->GetEbpLocation() - (securityObjectOffset * sizeof(void*)));
+    return (OBJECTREF *) (size_t) (GetRegdisplayFP(pRD) - (securityObjectOffset * sizeof(void*)));
 }
 #endif // _TARGET_X86_
 
@@ -5280,7 +5279,7 @@ OBJECTREF* EECodeManager::GetAddrOfSecurityObject(CrawlFrame *pCF)
         if(stateBuf->hdrInfoBody.prologOffs == hdrInfo::NOT_IN_PROLOG &&
                 stateBuf->hdrInfoBody.epilogOffs == hdrInfo::NOT_IN_EPILOG)
         {
-            return (OBJECTREF *)(size_t)(*pRD->GetEbpLocation() - GetSecurityObjectOffset(&stateBuf->hdrInfoBody));
+            return (OBJECTREF *)(size_t)(GetRegdisplayFP(pRD) - GetSecurityObjectOffset(&stateBuf->hdrInfoBody));
         }
     }
 #else // !USE_GC_INFO_DECODER
diff --git a/src/vm/proftoeeinterfaceimpl.cpp b/src/vm/proftoeeinterfaceimpl.cpp
index cff17213a7..03362f9299 100644
--- a/src/vm/proftoeeinterfaceimpl.cpp
+++ b/src/vm/proftoeeinterfaceimpl.cpp
@@ -7747,7 +7747,7 @@ Loop:
                 CodeManState codeManState;
                 codeManState.dwIsSet = 0;
                 REGDISPLAY rd;
-                ZeroMemory(&rd, sizeof(rd));
+                FillRegDisplay(&rd, &ctxCur);
 
                 rd.SetEbpLocation(&ctxCur.Ebp);
                 rd.SP = ctxCur.Esp;