[cdac] Implement ISOSDacInterface::GetUsefulGlobals (#105106)

Add the Exception, Object, Array of Object, and String method tables to the data descriptor and use them to implement ISOSDacInterface::GetUsefulGlobals in the cDAC.

Contracts are unaffected - this is just exposing those globals via the DAC API.

Author: elinor-fung

src/coreclr/debug/daccess/dacimpl.h

@@ -1242,6 +1242,7 @@ class ClrDataAccess
     HRESULT GetMethodTableNameImpl(CLRDATA_ADDRESS mt, unsigned int count, _Inout_updates_z_(count) WCHAR *mtName, unsigned int *pNeeded);
     HRESULT GetObjectExceptionDataImpl(CLRDATA_ADDRESS objAddr, struct DacpExceptionObjectData *data);
     HRESULT GetObjectStringDataImpl(CLRDATA_ADDRESS obj, unsigned int count, _Inout_updates_z_(count) WCHAR *stringData, unsigned int *pNeeded);
+    HRESULT GetUsefulGlobalsImpl(struct DacpUsefulGlobalsData *globalsData);
 
     BOOL IsExceptionFromManagedCode(EXCEPTION_RECORD * pExceptionRecord);
 #ifndef TARGET_UNIX
@@ -2005,7 +2006,7 @@ class DacMethodTableSlotEnumerator : public DefaultCOMImpl<ISOSMethodEnum, IID_I
     DacMethodTableSlotEnumerator() : mIteratorIndex(0)
     {
     }
-    
+
     virtual ~DacMethodTableSlotEnumerator() {}
 
     HRESULT Init(PTR_MethodTable mTable);

src/coreclr/debug/daccess/request.cpp

@@ -3460,13 +3460,47 @@ ClrDataAccess::GetHeapAnalyzeStaticData(struct DacpGcHeapAnalyzeData *analyzeDat
 }
 
 HRESULT
-ClrDataAccess::GetUsefulGlobals(struct DacpUsefulGlobalsData *globalsData)
+ClrDataAccess::GetUsefulGlobals(struct DacpUsefulGlobalsData* globalsData)
 {
     if (globalsData == NULL)
         return E_INVALIDARG;
 
     SOSDacEnter();
 
+    if (m_cdacSos != NULL)
+    {
+        hr = m_cdacSos->GetUsefulGlobals(globalsData);
+        if (FAILED(hr))
+        {
+            hr = GetUsefulGlobals(globalsData);
+        }
+#ifdef _DEBUG
+        else
+        {
+            // Assert that the data is the same as what we get from the DAC.
+            DacpUsefulGlobalsData globalsDataLocal;
+            HRESULT hrLocal = GetUsefulGlobalsImpl(&globalsDataLocal);
+            _ASSERTE(hr == hrLocal);
+            _ASSERTE(globalsData->ArrayMethodTable == globalsDataLocal.ArrayMethodTable);
+            _ASSERTE(globalsData->StringMethodTable == globalsDataLocal.StringMethodTable);
+            _ASSERTE(globalsData->ObjectMethodTable == globalsDataLocal.ObjectMethodTable);
+            _ASSERTE(globalsData->ExceptionMethodTable == globalsDataLocal.ExceptionMethodTable);
+            _ASSERTE(globalsData->FreeMethodTable == globalsDataLocal.FreeMethodTable);
+        }
+#endif
+    }
+    else
+    {
+        hr = GetUsefulGlobals(globalsData);;
+    }
+
+    SOSDacLeave();
+    return hr;
+}
+
+HRESULT
+ClrDataAccess::GetUsefulGlobalsImpl(struct DacpUsefulGlobalsData *globalsData)
+{
     TypeHandle objArray = g_pPredefinedArrayTypes[ELEMENT_TYPE_OBJECT];
     if (objArray != NULL)
         globalsData->ArrayMethodTable = HOST_CDADDR(objArray.AsMethodTable());
@@ -3478,8 +3512,7 @@ ClrDataAccess::GetUsefulGlobals(struct DacpUsefulGlobalsData *globalsData)
     globalsData->ExceptionMethodTable = HOST_CDADDR(g_pExceptionClass);
     globalsData->FreeMethodTable = HOST_CDADDR(g_pFreeObjectMethodTable);
 
-    SOSDacLeave();
-    return hr;
+    return S_OK;
 }
 
 HRESULT

src/coreclr/debug/runtimeinfo/datadescriptor.h

@@ -282,7 +282,10 @@ CDAC_GLOBAL(ObjectToMethodTableUnmask, uint8, 1 | 1 << 1 | 1 << 2)
 CDAC_GLOBAL(ObjectToMethodTableUnmask, uint8, 1 | 1 << 1)
 #endif //TARGET_64BIT
 CDAC_GLOBAL(SOSBreakingChangeVersion, uint8, SOS_BREAKING_CHANGE_VERSION)
+CDAC_GLOBAL_POINTER(ExceptionMethodTable, &::g_pExceptionClass)
 CDAC_GLOBAL_POINTER(FreeObjectMethodTable, &::g_pFreeObjectMethodTable)
+CDAC_GLOBAL_POINTER(ObjectMethodTable, &::g_pObjectClass)
+CDAC_GLOBAL_POINTER(ObjectArrayMethodTable, &::g_pPredefinedArrayTypes[ELEMENT_TYPE_OBJECT])
 CDAC_GLOBAL_POINTER(StringMethodTable, &::g_pStringClass)
 CDAC_GLOBAL_POINTER(MiniMetaDataBuffAddress, &::g_MiniMetaDataBuffAddress)
 CDAC_GLOBAL_POINTER(MiniMetaDataBuffMaxSize, &::g_MiniMetaDataBuffMaxSize)

src/native/managed/cdacreader/src/Constants.cs

@@ -17,7 +17,10 @@ internal static class Globals
         internal const string ObjectToMethodTableUnmask = nameof(ObjectToMethodTableUnmask);
         internal const string SOSBreakingChangeVersion = nameof(SOSBreakingChangeVersion);
 
+        internal const string ExceptionMethodTable = nameof(ExceptionMethodTable);
         internal const string FreeObjectMethodTable = nameof(FreeObjectMethodTable);
+        internal const string ObjectMethodTable = nameof(ObjectMethodTable);
+        internal const string ObjectArrayMethodTable = nameof(ObjectArrayMethodTable);
         internal const string StringMethodTable = nameof(StringMethodTable);
 
         internal const string MiniMetaDataBuffAddress = nameof(MiniMetaDataBuffAddress);

src/native/managed/cdacreader/src/Legacy/ISOSDacInterface.cs

@@ -91,6 +91,15 @@ internal struct DacpMethodTableData
     public int bIsDynamic;
     public int bContainsGCPointers;
 }
+
+internal struct DacpUsefulGlobalsData
+{
+    public ulong ArrayMethodTable;
+    public ulong StringMethodTable;
+    public ulong ObjectMethodTable;
+    public ulong ExceptionMethodTable;
+    public ulong FreeMethodTable;
+}
 #pragma warning restore CS0649 // Field is never assigned to, and will always have its default value
 
 [GeneratedComInterface]
@@ -280,7 +289,7 @@ internal unsafe partial interface ISOSDacInterface
 
     // Other
     [PreserveSig]
-    int GetUsefulGlobals(/*struct DacpUsefulGlobalsData */ void* data);
+    int GetUsefulGlobals(DacpUsefulGlobalsData* data);
     [PreserveSig]
     int GetClrWatsonBuckets(ulong thread, void* pGenericModeBlock);
     [PreserveSig]

src/native/managed/cdacreader/src/Legacy/SOSDacImpl.cs

@@ -403,7 +403,30 @@ public unsafe int GetThreadStoreData(DacpThreadStoreData* data)
     }
 
     public unsafe int GetTLSIndex(uint* pIndex) => HResults.E_NOTIMPL;
-    public unsafe int GetUsefulGlobals(void* data) => HResults.E_NOTIMPL;
+
+    public unsafe int GetUsefulGlobals(DacpUsefulGlobalsData* data)
+    {
+        try
+        {
+            data->ArrayMethodTable = _target.ReadPointer(
+                _target.ReadGlobalPointer(Constants.Globals.ObjectArrayMethodTable));
+            data->StringMethodTable = _target.ReadPointer(
+                _target.ReadGlobalPointer(Constants.Globals.StringMethodTable));
+            data->ObjectMethodTable = _target.ReadPointer(
+                _target.ReadGlobalPointer(Constants.Globals.ObjectMethodTable));
+            data->ExceptionMethodTable = _target.ReadPointer(
+                _target.ReadGlobalPointer(Constants.Globals.ExceptionMethodTable));
+            data->FreeMethodTable = _target.ReadPointer(
+                _target.ReadGlobalPointer(Constants.Globals.FreeObjectMethodTable));
+        }
+        catch (System.Exception ex)
+        {
+            return ex.HResult;
+        }
+
+        return HResults.S_OK;
+    }
+
     public unsafe int GetWorkRequestData(ulong addrWorkRequest, void* data) => HResults.E_NOTIMPL;
     public unsafe int IsRCWDCOMProxy(ulong rcwAddress, int* inDCOMProxy) => HResults.E_NOTIMPL;
     public unsafe int TraverseEHInfo(ulong ip, void* pCallback, void* token) => HResults.E_NOTIMPL;