[cDAC] Add GetApproxTypeHandle DacDbi API

docs/design/datacontracts/RuntimeTypeSystem.md

@@ -59,8 +59,8 @@ partial interface IRuntimeTypeSystem : IContract
     // True if the MethodTable is the System.Object MethodTable (g_pObjectClass)
     public virtual bool IsObject(TypeHandle typeHandle);
     public virtual bool IsString(TypeHandle typeHandle);
-    // True if the type is a GC-collectable object reference.
-    public virtual bool IsObjRef(TypeHandle typeHandle);
+    // True if the CorElementType represents a GC-collectable object reference.
+    public virtual bool IsCorElementTypeObjRef(CorElementType elementType);
     // True if the MethodTable represents a type that contains managed references
     public virtual bool ContainsGCPointers(TypeHandle typeHandle);
     // True if the type requires 8-byte alignment on platforms that don't 8-byte align by default (FEATURE_64BIT_ALIGNMENT)
@@ -603,7 +603,14 @@ Contracts used:
 
     public bool IsString(TypeHandle TypeHandle) => !typeHandle.IsMethodTable() ? false : _methodTables[TypeHandle.Address].Flags.IsString;
 
-    public bool IsObjRef(TypeHandle typeHandle) => // Returns true if GetSignatureCorElementType returns Class, Array, or SzArray.
+    public bool IsCorElementTypeObjRef(CorElementType elementType) =>
+        elementType is CorElementType.Class
+                    or CorElementType.Object
+                    or CorElementType.String
+                    or CorElementType.Array
+                    or CorElementType.SzArray
+                    or CorElementType.Var
+                    or CorElementType.MVar;
 
     public bool ContainsGCPointers(TypeHandle TypeHandle) => !typeHandle.IsMethodTable() ? false : _methodTables[TypeHandle.Address].Flags.ContainsGCPointers;
 

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.cs

@@ -130,7 +130,8 @@ public interface IRuntimeTypeSystem : IContract
     // True if the MethodTable is the System.Object MethodTable (g_pObjectClass)
     bool IsObject(TypeHandle typeHandle) => throw new NotImplementedException();
     bool IsString(TypeHandle typeHandle) => throw new NotImplementedException();
-    bool IsObjRef(TypeHandle typeHandle) => throw new NotImplementedException();
+    // True if the CorElementType represents a GC-collectable object reference.
+    bool IsCorElementTypeObjRef(CorElementType elementType) => throw new NotImplementedException();
     // True if the MethodTable represents a type that contains managed references
     bool ContainsGCPointers(TypeHandle typeHandle) => throw new NotImplementedException();
     // True if the type requires 8-byte alignment on platforms that don't 8-byte align by default (FEATURE_64BIT_ALIGNMENT)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs

@@ -560,12 +560,14 @@ private Data.EEClass GetClassData(TypeHandle typeHandle)
     public bool IsObject(TypeHandle typeHandle) => ObjectMethodTablePointer != TargetPointer.Null && ObjectMethodTablePointer == typeHandle.Address;
 
     public bool IsString(TypeHandle typeHandle) => !typeHandle.IsMethodTable() ? false : _methodTables[typeHandle.Address].Flags.IsString;
-    public bool IsObjRef(TypeHandle typeHandle)
-    {
-        CorElementType elementType = GetSignatureCorElementType(typeHandle);
-        // Keep this aligned with CorTypeInfo::IsObjRef semantics for signature element types.
-        return elementType is CorElementType.Class or CorElementType.Array or CorElementType.SzArray;
-    }
+    public bool IsCorElementTypeObjRef(CorElementType elementType)
+        => elementType is CorElementType.Class
+            or CorElementType.Object
+            or CorElementType.String
+            or CorElementType.Array
+            or CorElementType.SzArray
+            or CorElementType.Var
+            or CorElementType.MVar;
     public bool ContainsGCPointers(TypeHandle typeHandle) => !typeHandle.IsMethodTable() ? false : _methodTables[typeHandle.Address].Flags.ContainsGCPointers;
     public bool RequiresAlign8(TypeHandle typeHandle) => !typeHandle.IsMethodTable() ? false : _methodTables[typeHandle.Address].Flags.RequiresAlign8;
     public bool IsContinuationWithoutMetadata(TypeHandle typeHandle) => typeHandle.IsMethodTable()

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs

@@ -1907,8 +1907,45 @@ public int GetTypeHandle(ulong vmModule, uint metadataToken, ulong* pRetVal)
         return hr;
     }
 
-    public int GetApproxTypeHandle(nint pTypeData, ulong* pRetVal)
-        => LegacyFallbackHelper.CanFallback() && _legacy is not null ? _legacy.GetApproxTypeHandle(pTypeData, pRetVal) : HResults.E_NOTIMPL;
+    public int GetApproxTypeHandle(TypeInfoList* pTypeData, ulong* pRetVal)
+    {
+        if (pTypeData == null || pRetVal == null)
+            return HResults.E_POINTER;
+        *pRetVal = 0;
+        int hr = HResults.S_OK;
+        try
+        {
+            IRuntimeTypeSystem rts = _target.Contracts.RuntimeTypeSystem;
+
+            TargetPointer canonMtPtr = _target.ReadPointer(_target.ReadGlobalPointer(Constants.Globals.CanonMethodTable));
+            TypeHandle canonTh = rts.GetTypeHandle(canonMtPtr);
+
+            if (pTypeData->m_nEntries <= 0 || pTypeData->m_pList == null)
+                throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_CLASS_NOT_LOADED)!;
+
+            TypeDataWalk walk = new TypeDataWalk(_target, rts, canonTh, pTypeData->m_pList, (uint)pTypeData->m_nEntries);
+            TypeHandle th = walk.ReadLoadedTypeHandle();
+            if (th.IsNull)
+                throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_CLASS_NOT_LOADED)!;
+            *pRetVal = th.Address.Value;
+        }
+        catch (System.Exception ex)
+        {
+            hr = ex.HResult;
+        }
+#if DEBUG
+        if (_legacy is not null)
+        {
+            ulong vmLocal;
+            int hrLocal = _legacy.GetApproxTypeHandle(pTypeData, &vmLocal);
+            Debug.ValidateHResult(hr, hrLocal);
+            if (hr == HResults.S_OK)
+                Debug.Assert(*pRetVal == vmLocal, $"cDAC: {*pRetVal:x}, DAC: {vmLocal:x}");
+        }
+#endif
+        return hr;
+    }
+
 
     public int GetExactTypeHandle(DebuggerIPCE_ExpandedTypeData* pTypeData, ArgInfoList* pArgInfo, ulong* pVmTypeHandle)
     {
@@ -2000,29 +2037,7 @@ private TypeHandle GetClassOrValueTypeHandle(IRuntimeTypeSystem rts, DebuggerIPC
 
         ulong vmAssembly = ReadLittleEndian(pData->vmAssembly);
         uint metadataToken = ReadLittleEndian(pData->metadataToken);
-        return LookupTypeDefOrRefInAssembly(rts, vmAssembly, metadataToken);
-    }
-
-    private TypeHandle LookupTypeDefOrRefInAssembly(IRuntimeTypeSystem rts, ulong vmAssembly, uint metadataToken)
-    {
-        Contracts.ILoader loader = _target.Contracts.Loader;
-        Contracts.ModuleHandle moduleHandle = loader.GetModuleHandleFromAssemblyPtr(new TargetPointer(vmAssembly));
-        Contracts.ModuleLookupTables lookupTables = loader.GetLookupTables(moduleHandle);
-        TargetPointer mt;
-        switch ((EcmaMetadataUtils.TokenType)(metadataToken & EcmaMetadataUtils.TokenTypeMask))
-        {
-            case EcmaMetadataUtils.TokenType.mdtTypeDef:
-                mt = loader.GetModuleLookupMapElement(lookupTables.TypeDefToMethodTable, metadataToken, out _);
-                break;
-            case EcmaMetadataUtils.TokenType.mdtTypeRef:
-                mt = loader.GetModuleLookupMapElement(lookupTables.TypeRefToMethodTable, metadataToken, out _);
-                break;
-            default:
-                throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_CLASS_NOT_LOADED)!;
-        }
-        if (mt == TargetPointer.Null)
-            throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_CLASS_NOT_LOADED)!;
-        return rts.GetTypeHandle(mt);
+        return DbiHelpers.LookupTypeDefOrRefInAssembly(_target, rts, vmAssembly, metadataToken);
     }
 
     private TypeHandle GetExactArrayTypeHandle(IRuntimeTypeSystem rts, DebuggerIPCE_ExpandedTypeData* pTopLevel, ArgInfoList* pArgInfo)
@@ -2048,7 +2063,7 @@ private TypeHandle GetExactClassTypeHandle(IRuntimeTypeSystem rts, DebuggerIPCE_
     {
         ulong vmAssembly = ReadLittleEndian(pTopLevel->ClassTypeData_vmAssembly);
         uint metadataToken = ReadLittleEndian(pTopLevel->ClassTypeData_metadataToken);
-        TypeHandle typeConstructor = LookupTypeDefOrRefInAssembly(rts, vmAssembly, metadataToken);
+        TypeHandle typeConstructor = DbiHelpers.LookupTypeDefOrRefInAssembly(_target, rts, vmAssembly, metadataToken);
 
         int argCount = pArgInfo->m_nEntries;
         if (argCount == 0)
@@ -3228,7 +3243,7 @@ public int GetObjectFields(ulong id, uint celt, COR_FIELD* layout, uint* pceltFe
                 // count actually written. Preserve this behavior for compatibility w/ICorDebug.
                 *pceltFetched = celt;
 
-                bool isReferenceType = rts.IsObjRef(typeHandle);
+                bool isReferenceType = rts.IsCorElementTypeObjRef(rts.GetInternalCorElementType(typeHandle));
                 uint firstFieldOffset = isReferenceType ? _target.GetTypeInfo(DataType.Object).Size!.Value : 0;
 
                 TargetPointer[] fieldDescList = rts.GetFieldDescList(typeHandle).Take((int)cFields).ToArray();
@@ -3358,8 +3373,11 @@ public int GetTypeLayout(ulong id, COR_TYPE_LAYOUT* pLayout)
                 numInstanceFields -= rts.GetNumInstanceFields(parentHandle);
             }
             pLayout->numFields = numInstanceFields;
-            pLayout->boxOffset = rts.IsObjRef(typeHandle) ? 0u : (uint)_target.PointerSize;
-            pLayout->type = (int)(rts.IsString(typeHandle) ? CorElementType.String : rts.GetInternalCorElementType(typeHandle));
+            CorElementType componentType = rts.IsString(typeHandle)
+                ? CorElementType.String
+                : rts.GetInternalCorElementType(typeHandle);
+            pLayout->type = (int)componentType;
+            pLayout->boxOffset = rts.IsCorElementTypeObjRef(componentType) ? 0u : (uint)_target.PointerSize;
         }
         catch (System.Exception ex)
         {
@@ -4208,7 +4226,7 @@ private static void WriteLittleEndian<T>(ref T dest, T value) where T : unmanage
         }
     }
 
-    private static T ReadLittleEndian<T>(T value) where T : unmanaged, IBinaryInteger<T>
+    internal static T ReadLittleEndian<T>(T value) where T : unmanaged, IBinaryInteger<T>
     {
         if (BitConverter.IsLittleEndian)
             return value;

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DbiHelpers.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.InteropServices;
+using Microsoft.Diagnostics.DataContractReader.Contracts;
+
+namespace Microsoft.Diagnostics.DataContractReader.Legacy;
+internal static class DbiHelpers
+{
+    public static TypeHandle LookupTypeDefOrRefInAssembly(Target target, IRuntimeTypeSystem rts, ulong vmAssembly, uint metadataToken)
+    {
+        TypeHandle th = TryLookupTypeDefOrRefInAssembly(target, rts, vmAssembly, metadataToken);
+        if (th.IsNull)
+            throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_CLASS_NOT_LOADED)!;
+        return th;
+    }
+
+    public static TypeHandle TryLookupTypeDefOrRefInAssembly(Target target, IRuntimeTypeSystem rts, ulong vmAssembly, uint metadataToken)
+    {
+        ILoader loader = target.Contracts.Loader;
+        ModuleHandle moduleHandle = loader.GetModuleHandleFromAssemblyPtr(new TargetPointer(vmAssembly));
+        ModuleLookupTables lookupTables = loader.GetLookupTables(moduleHandle);
+        TargetPointer mt;
+        switch ((EcmaMetadataUtils.TokenType)(metadataToken & EcmaMetadataUtils.TokenTypeMask))
+        {
+            case EcmaMetadataUtils.TokenType.mdtTypeDef:
+                mt = loader.GetModuleLookupMapElement(lookupTables.TypeDefToMethodTable, metadataToken, out _);
+                break;
+            case EcmaMetadataUtils.TokenType.mdtTypeRef:
+                mt = loader.GetModuleLookupMapElement(lookupTables.TypeRefToMethodTable, metadataToken, out _);
+                break;
+            default:
+                return default;
+        }
+        if (mt == TargetPointer.Null)
+            return default;
+        return rts.GetTypeHandle(mt);
+    }
+}

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/IDacDbiInterface.cs

@@ -287,6 +287,20 @@ public unsafe struct ArgInfoList
     public int m_nEntries;
 }
 
+[StructLayout(LayoutKind.Sequential, Size = 48)]
+public struct DebuggerIPCE_TypeArgData
+{
+    public DebuggerIPCE_ExpandedTypeData data;
+    public uint numTypeArgs; // Portable<UINT>
+}
+
+[StructLayout(LayoutKind.Sequential)]
+public unsafe struct TypeInfoList
+{
+    public DebuggerIPCE_TypeArgData* m_pList;
+    public int m_nEntries;
+}
+
 public enum DynamicMethodType
 {
     kNone = 0,
@@ -551,7 +565,7 @@ public unsafe partial interface IDacDbiInterface
     int GetTypeHandle(ulong vmModule, uint metadataToken, ulong* pRetVal);
 
     [PreserveSig]
-    int GetApproxTypeHandle(nint pTypeData, ulong* pRetVal);
+    int GetApproxTypeHandle(TypeInfoList* pTypeData, ulong* pRetVal);
 
     [PreserveSig]
     int GetExactTypeHandle(DebuggerIPCE_ExpandedTypeData* pTypeData, ArgInfoList* pArgInfo, ulong* pVmTypeHandle);