Signature parsing and GetFieldDescData cDAC API (#119417)

* signature parsing and GetFieldDescData cDAC API

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Max Charlamb <44248479+max-charlamb@users.noreply.github.com>

Author: 3 people

docs/design/datacontracts/RuntimeTypeSystem.md

@@ -86,11 +86,14 @@ partial interface IRuntimeTypeSystem : IContract
     public virtual CorElementType GetSignatureCorElementType(TypeHandle typeHandle);
 
     // return true if the TypeHandle represents an array, and set the rank to either 0 (if the type is not an array), or the rank number if it is.
-    public virtual bool IsArray(TypeHandle typeHandle, out uint rank);
-    public virtual TypeHandle GetTypeParam(TypeHandle typeHandle);
-    public virtual bool IsGenericVariable(TypeHandle typeHandle, out TargetPointer module, out uint token);
-    public virtual bool IsFunctionPointer(TypeHandle typeHandle, out ReadOnlySpan<TypeHandle> retAndArgTypes, out byte callConv);
-    public virtual TargetPointer GetLoaderModule(TypeHandle typeHandle);
+    bool IsArray(TypeHandle typeHandle, out uint rank);
+    TypeHandle GetTypeParam(TypeHandle typeHandle);
+    TypeHandle GetConstructedType(TypeHandle typeHandle, CorElementType corElementType, int rank, ImmutableArray<TypeHandle> typeArguments);
+    TypeHandle GetPrimitiveType(CorElementType typeCode);
+    bool IsGenericVariable(TypeHandle typeHandle, out TargetPointer module, out uint token);
+    bool IsFunctionPointer(TypeHandle typeHandle, out ReadOnlySpan<TypeHandle> retAndArgTypes, out byte callConv);
+    bool IsPointer(TypeHandle typeHandle);
+    TargetPointer GetLoaderModule(TypeHandle typeHandle);
 
     #endregion TypeHandle inspection APIs
 }
@@ -189,6 +192,16 @@ partial interface IRuntimeTypeSystem : IContract
 }
 ```
 
+### FieldDesc
+```csharp
+TargetPointer GetMTOfEnclosingClass(TargetPointer fieldDescPointer);
+uint GetFieldDescMemberDef(TargetPointer fieldDescPointer);
+bool IsFieldDescThreadStatic(TargetPointer fieldDescPointer);
+bool IsFieldDescStatic(TargetPointer fieldDescPointer);
+uint GetFieldDescType(TargetPointer fieldDescPointer);
+uint GetFieldDescOffset(TargetPointer fieldDescPointer, FieldDefinition fieldDef);
+```
+
 ## Version 1
 
 ### TypeHandle
@@ -403,6 +416,11 @@ Contracts used:
 | --- |
 | `Thread` |
 
+### Contract Constants:
+| Name | Type | Purpose | Value |
+| --- | --- | --- | --- |
+| `TYPE_MASK_OFFSET` | int | The number of bits the type is shifted left in the field desc flags2 | `27` |
+
 
 ```csharp
     private readonly Dictionary<TargetPointer, MethodTable_1> _methodTables;
@@ -717,6 +735,89 @@ Contracts used:
         throw new ArgumentException(nameof(typeHandle));
     }
 
+    // helper functions
+
+    private bool GenericInstantiationMatch(TypeHandle genericType, TypeHandle potentialMatch, ImmutableArray<TypeHandle> typeArguments)
+    {
+        ReadOnlySpan<TypeHandle> instantiation = GetInstantiation(potentialMatch);
+        if (instantiation.Length != typeArguments.Length)
+            return false;
+
+        if (GetTypeDefToken(genericType) != GetTypeDefToken(potentialMatch))
+            return false;
+
+        if (GetModule(genericType) != GetModule(potentialMatch))
+            return false;
+
+        for (int i = 0; i < instantiation.Length; i++)
+        {
+            if (!(instantiation[i].Address == typeArguments[i].Address))
+                return false;
+        }
+        return true;
+    }
+
+    private bool ArrayPtrMatch(TypeHandle elementType, CorElementType corElementType, int rank, TypeHandle potentialMatch)
+    {
+        IsArray(potentialMatch, out uint typeHandleRank);
+        return GetSignatureCorElementType(potentialMatch) == corElementType &&
+                GetTypeParam(potentialMatch).Address == elementType.Address &&
+                (corElementType == CorElementType.SzArray || corElementType == CorElementType.Byref ||
+                corElementType == CorElementType.Ptr || (rank == typeHandleRank));
+
+    }
+
+    private bool IsLoaded(TypeHandle typeHandle)
+    {
+        if (typeHandle.Address == TargetPointer.Null)
+            return false;
+        if (typeHandle.IsTypeDesc())
+        {
+            uint typeAndFlags = _target.Read<uint>(typeHandle.TypeDescAddress() + /* TypeDesc::TypeAndFlags offset */);
+            return (typeAndFlags & (uint)TypeDescFlags.IsNotFullyLoaded) == 0;
+        }
+
+        MethodTable methodTable = _methodTables[typeHandle.Address];
+        uint flags = _target.Read<uint>(methodTable.AuxiliaryData + /* AuxiliaryData::Flags offset */);
+        return (flags & (uint)MethodTableAuxiliaryFlags.IsNotFullyLoaded) == 0;
+    }
+
+    TypeHandle GetConstructedType(TypeHandle typeHandle, CorElementType corElementType, int rank, ImmutableArray<TypeHandle> typeArguments)
+    {
+        if (typeHandle.Address == TargetPointer.Null)
+            return new TypeHandle(TargetPointer.Null);
+        ILoader loaderContract = _target.Contracts.Loader;
+        TargetPointer loaderModule = GetLoaderModule(typeHandle);
+        ModuleHandle moduleHandle = loaderContract.GetModuleHandleFromModulePtr(loaderModule);
+        TypeHandle potentialMatch = new TypeHandle(TargetPointer.Null);
+        foreach (TargetPointer ptr in loaderContract.GetAvailableTypeParams(moduleHandle))
+        {
+            potentialMatch = GetTypeHandle(ptr);
+            if (corElementType == CorElementType.GenericInst)
+            {
+                if (GenericInstantiationMatch(typeHandle, potentialMatch, typeArguments) && IsLoaded(potentialMatch))
+                {
+                    _ = _typeHandles.TryAdd(new TypeKey(typeHandle, corElementType, rank, typeArguments), potentialMatch);
+                    return potentialMatch;
+                }
+            }
+            else if (ArrayPtrMatch(typeHandle, corElementType, rank, potentialMatch) && IsLoaded(potentialMatch))
+            {
+                _ = _typeHandles.TryAdd(new TypeKey(typeHandle, corElementType, rank, typeArguments), potentialMatch);
+                return potentialMatch;
+            }
+        }
+        return new TypeHandle(TargetPointer.Null);
+    }
+
+    public TypeHandle GetPrimitiveType(CorElementType typeCode)
+    {
+        TargetPointer coreLib = _target.ReadGlobalPointer("CoreLib");
+        TargetPointer classes = _target.ReadPointer(coreLib + /* CoreLibBinder::Classes offset */);
+        TargetPointer typeHandlePtr = _target.ReadPointer(classes + (ulong)typeCode * (ulong)_target.PointerSize);
+        return GetTypeHandle(typeHandlePtr);
+    }
+
     public bool IsGenericVariable(TypeHandle typeHandle, out TargetPointer module, out uint token)
     {
         module = TargetPointer.Null;
@@ -748,7 +849,7 @@ Contracts used:
             return false;
 
         int TypeAndFlags = // Read TypeAndFlags field from TypeDesc contract using address typeHandle.TypeDescAddress()
-        CorElementType elemType = (CorElementType)(typeDesc.TypeAndFlags & 0xFF);
+        CorElementType elemType = (CorElementType)(TypeAndFlags & 0xFF);
 
         if (elemType != CorElementType.FnPtr)
             return false;
@@ -765,6 +866,16 @@ Contracts used:
         return true;
     }
 
+    public bool IsPointer(TypeHandle typeHandle)
+    {
+        if (!typeHandle.IsTypeDesc())
+            return false;
+
+        int TypeAndFlags = // Read TypeAndFlags field from TypeDesc contract using address typeHandle.TypeDescAddress()
+        CorElementType elemType = (CorElementType)(TypeAndFlags & 0xFF);
+        return elemType == CorElementType.Ptr;
+    }
+
     public TargetPointer GetLoaderModule(TypeHandle typeHandle)
     {
         if (typeHandle.IsTypeDesc())
@@ -915,6 +1026,12 @@ And the following enumeration definitions
     {
         Initialized = 0x0001,
         IsInitError = 0x0100,
+        IsNotFullyLoaded = 0x0040,
+    }
+
+    internal enum TypeDescFlags : uint
+    {
+        IsNotFullyLoaded = 0x00001000,
     }
 
 ```
@@ -1532,3 +1649,66 @@ Getting a MethodDesc for a certain slot in a MethodTable
         return GetMethodDescForEntrypoint(pCode);
     }
 ```
+
+### FieldDesc
+
+The version 1 FieldDesc APIs depend on the following data descriptors:
+| Data Descriptor Name | Field | Meaning |
+| --- | --- | --- |
+| `FieldDesc` | `MTOfEnclosingClass` | Pointer to method table of enclosing class |
+| `FieldDesc` | `DWord1` | The FD's flags and token |
+| `FieldDesc` | `DWord2` | The FD's kind and offset |
+
+```csharp
+internal enum FieldDescFlags1 : uint
+{
+    TokenMask = 0xffffff,
+    IsStatic = 0x1000000,
+    IsThreadStatic = 0x2000000,
+}
+
+internal enum FieldDescFlags2 : uint
+{
+    TypeMask = 0xf8000000,
+    OffsetMask = 0x07ffffff,
+}
+
+TargetPointer GetMTOfEnclosingClass(TargetPointer fieldDescPointer)
+{
+    return target.ReadPointer(fieldDescPointer + /* FieldDesc::MTOfEnclosingClass offset */);
+}
+
+uint GetFieldDescMemberDef(TargetPointer fieldDescPointer)
+{
+    uint DWord1 = target.Read<uint>(fieldDescPointer + /* FieldDesc::DWord1 offset */);
+    return EcmaMetadataUtils.CreateFieldDef(DWord1 & (uint)FieldDescFlags1.TokenMask);
+}
+
+bool IsFieldDescThreadStatic(TargetPointer fieldDescPointer)
+{
+    uint DWord1 = target.Read<uint>(fieldDescPointer + /* FieldDesc::DWord1 offset */);
+    return (DWord1 & (uint)FieldDescFlags1.IsThreadStatic) != 0;
+}
+
+bool IsFieldDescStatic(TargetPointer fieldDescPointer)
+{
+    uint DWord1 = target.Read<uint>(fieldDescPointer + /* FieldDesc::DWord1 offset */);
+    return (DWord1 & (uint)FieldDescFlags1.IsStatic) != 0;
+}
+
+uint GetFieldDescType(TargetPointer fieldDescPointer)
+{
+    uint DWord2 = target.Read<uint>(fieldDescPointer + /* FieldDesc::DWord2 offset */);
+    return (DWord2 & (uint)FieldDescFlags2.TypeMask) >> 27;
+}
+
+uint GetFieldDescOffset(TargetPointer fieldDescPointer)
+{
+    uint DWord2 = target.Read<uint>(fieldDescPointer + /* FieldDesc::DWord2 offset */);
+    if (DWord2 == _target.ReadGlobal<uint>("FieldOffsetBigRVA"))
+    {
+        return (uint)fieldDef.GetRelativeVirtualAddress();
+    }
+    return DWord2 & (uint)FieldDescFlags2.OffsetMask;
+}
+```

docs/design/datacontracts/SignatureDecoder.md

@@ -0,0 +1,70 @@
+# Contract SignatureDecoder
+
+This contract encapsulates signature decoding in the cDAC.
+
+## APIs of contract
+
+```csharp
+TypeHandle DecodeFieldSignature(BlobHandle blobHandle, ModuleHandle moduleHandle, TypeHandle ctx);
+```
+
+## Version 1
+
+In version 1 of the SignatureDecoder contract we take advantage of the System.Reflection.Metadata signature decoding. We implement a SignatureTypeProvider that inherits from System.Reflection.Metadata ISignatureTypeProvider.
+
+Data descriptors used:
+| Data Descriptor Name | Field | Meaning |
+| --- | --- | --- |
+
+
+Global variables used:
+| Global Name | Type | Purpose |
+| --- | --- | --- |
+
+
+Contracts used:
+| Contract Name |
+| --- |
+| RuntimeTypeSystem |
+| Loader |
+| EcmaMetadata |
+
+### SignatureTypeProvider
+The cDAC implements the ISignatureTypeProvider<TType,TGenericContext> with TType=TypeHandle. TGenericContext can either be a MethodDescHandle or TypeHandle; MethodDescHandle context is used to look up generic method parameters, and TypeHandle context is used to look up generic type parameters.
+
+A cDAC SignatureTypeProvider is instantiated over a Module which is used to lookup types.
+
+The following ISignatureTypeProvider APIs are trivially implemented using RuntimeTypeSystem.GetPrimitiveType and RuntimeTypeSystem.GetConstructedType:
+
+* GetArrayType - GetConstructedType
+* GetByReferenceType - GetConstructedType
+* GetFunctionPointerType - Implemented as primitive IntPtr type
+* GetGenericInstantiation - GetConstructedType
+* GetModifiedType - Returns unmodified type
+* GetPinnedType - Returns unpinned type
+* GetPointerType - GetConstructedType
+* GetPrimitiveType - GetConstructedType
+* GetSZArrayType - GetConstructedType
+
+GetGenericMethodParameter is only supported when TGenericContext=MethodDescHandle and looks up the method parameters from the context using RuntimeTypeSystem.GetGenericMethodInstantiation.
+
+GetGenericTypeParameter is only supported when TGenericContext=TypeHandle and looks up the type parameters from the context using RuntimeTypeSystem.GetInstantiation.
+
+GetTypeFromDefinition uses the SignatureTypeProvider's ModuleHandle to lookup the given Token in the Module's TypeDefToMethodTableMap. If a value is not found return null.
+
+GetTypeFromReference uses the SignatureTypeProvider's ModuleHandle to lookup the given Token in the Module's TypeRefToMethodTableMap. If a value is not found return null.The implementation when the type exists in a different module is incomplete.
+
+GetTypeFromSpecification is not currently implemented.
+
+
+### APIs
+```csharp
+TypeHandle ISignatureDecoder.DecodeFieldSignature(BlobHandle blobHandle, ModuleHandle moduleHandle, TypeHandle ctx)
+{
+    SignatureTypeProvider<TypeHandle> provider = new(_target, moduleHandle);
+    MetadataReader mdReader = _target.Contracts.EcmaMetadata.GetMetadata(moduleHandle)!;
+    BlobReader blobReader = mdReader.GetBlobReader(blobHandle);
+    SignatureDecoder<TypeHandle, TypeHandle> decoder = new(provider, mdReader, ctx);
+    return decoder.DecodeFieldSignature(ref blobReader);
+}
+```

src/coreclr/vm/binder.h

@@ -28,7 +28,7 @@ struct HardCodedMetaSig
 #define DEFINE_METASIG_T(body)          extern body
 #define METASIG_BODY(varname, types)    HardCodedMetaSig gsig_ ## varname;
 #include "metasig.h"
-
+#include "cdacdata.h"
 //
 // Use the Binder objects to avoid doing unnecessary name lookup
 // (esp. in the prejit case)
@@ -294,6 +294,7 @@ class CoreLibBinder
     USHORT m_cFields;
 
     static CrstStatic s_SigConvertCrst;
+    friend struct ::cdac_data<CoreLibBinder>;
 
 #ifdef _DEBUG
 
@@ -313,6 +314,12 @@ class CoreLibBinder
 #endif
 };
 
+template<>
+struct cdac_data<CoreLibBinder>
+{
+    static constexpr size_t Classes = offsetof(CoreLibBinder, m_pClasses);
+};
+
 //
 // Global bound modules:
 //

src/coreclr/vm/datadescriptor/datadescriptor.inc

@@ -333,6 +333,13 @@ CDAC_TYPE_INDETERMINATE(TypeDesc)
 CDAC_TYPE_FIELD(TypeDesc, /*uint32*/, TypeAndFlags, cdac_data<TypeDesc>::TypeAndFlags)
 CDAC_TYPE_END(TypeDesc)
 
+CDAC_TYPE_BEGIN(FieldDesc)
+CDAC_TYPE_SIZE(sizeof(FieldDesc))
+CDAC_TYPE_FIELD(FieldDesc, /*uint32*/, DWord1, cdac_data<FieldDesc>::DWord1)
+CDAC_TYPE_FIELD(FieldDesc, /*uint32*/, DWord2, cdac_data<FieldDesc>::DWord2)
+CDAC_TYPE_FIELD(FieldDesc, /*pointer*/, MTOfEnclosingClass, cdac_data<FieldDesc>::MTOfEnclosingClass)
+CDAC_TYPE_END(FieldDesc)
+
 CDAC_TYPE_BEGIN(ParamTypeDesc)
 CDAC_TYPE_INDETERMINATE(ParamTypeDesc)
 CDAC_TYPE_FIELD(ParamTypeDesc, /*pointer*/, TypeArg, cdac_data<ParamTypeDesc>::TypeArg)
@@ -912,6 +919,11 @@ CDAC_TYPE_FIELD(InstMethodHashTable, /*pointer*/, VolatileEntryValue, cdac_data<
 CDAC_TYPE_FIELD(InstMethodHashTable, /*pointer*/, VolatileEntryNextEntry, cdac_data<InstMethodHashTable>::VolatileEntryNextEntry)
 CDAC_TYPE_END(InstMethodHashTable)
 
+CDAC_TYPE_BEGIN(CoreLibBinder)
+CDAC_TYPE_INDETERMINATE(CoreLibBinder)
+CDAC_TYPE_FIELD(CoreLibBinder, /*pointer*/, Classes, cdac_data<CoreLibBinder>::Classes)
+CDAC_TYPE_END(CoreLibBinder)
+
 // this is an SHash type
 CDAC_TYPE_BEGIN(DynamicILBlobTable)
 CDAC_TYPE_SIZE(cdac_data<DynamicILBlobTable>::EntrySize)
@@ -999,6 +1011,7 @@ CDAC_GLOBAL(StaticsPointerMask, uintptr_t, DynamicStaticsInfo::STATICSPOINTERMAS
 CDAC_GLOBAL(PtrArrayOffsetToDataArray, uintptr_t, offsetof(PtrArray, m_Array))
 CDAC_GLOBAL(NumberOfTlsOffsetsNotUsedInNoncollectibleArray, uint8, NUMBER_OF_TLSOFFSETS_NOT_USED_IN_NONCOLLECTIBLE_ARRAY)
 CDAC_GLOBAL(MaxClrNotificationArgs, uint32, MAX_CLR_NOTIFICATION_ARGS)
+CDAC_GLOBAL(FieldOffsetBigRVA, uint32, FIELD_OFFSET_BIG_RVA)
 CDAC_GLOBAL_POINTER(ClrNotificationArguments, &::g_clrNotificationArguments)
 CDAC_GLOBAL_POINTER(ArrayBoundsZero, cdac_data<ArrayBase>::ArrayBoundsZero)
 CDAC_GLOBAL_POINTER(ExceptionMethodTable, &::g_pExceptionClass)
@@ -1012,6 +1025,7 @@ CDAC_GLOBAL_POINTER(MiniMetaDataBuffMaxSize, &::g_MiniMetaDataBuffMaxSize)
 CDAC_GLOBAL_POINTER(DacNotificationFlags, &::g_dacNotificationFlags)
 CDAC_GLOBAL_POINTER(OffsetOfCurrentThreadInfo, &::g_offsetOfCurrentThreadInfo)
 CDAC_GLOBAL_POINTER(ThinlockThreadIdDispenser, &::g_pThinLockThreadIdDispenser)
+CDAC_GLOBAL_POINTER(CoreLib, &::g_CoreLib)
 #ifdef TARGET_WINDOWS
 CDAC_GLOBAL_POINTER(TlsIndexBase, &::_tls_index)
 #endif // TARGET_WINDOWS
@@ -1053,6 +1067,7 @@ CDAC_GLOBAL_CONTRACT(ReJIT, 1)
 CDAC_GLOBAL_CONTRACT(RuntimeInfo, 1)
 CDAC_GLOBAL_CONTRACT(RuntimeTypeSystem, 1)
 CDAC_GLOBAL_CONTRACT(SHash, 1)
+CDAC_GLOBAL_CONTRACT(SignatureDecoder, 1)
 CDAC_GLOBAL_CONTRACT(StackWalk, 1)
 CDAC_GLOBAL_CONTRACT(StressLog, 2)
 CDAC_GLOBAL_CONTRACT(Thread, 1)