Implementation of SOSDacApi GetMethodDescName for cDAC (dotnet#106169)

Add a number of new `MethodDesc` contract definitions

| Contract algorithm on RuntimeTypeSystem |
| --- |
| `IsGenericMethodDefinition`|
|`GetGenericMethodInstantiation`|
|`GetMethodToken`|
|`IsArrayMethod`|
|`IsDynamicMethod`|
|`IsStoredSigMethodDesc`|
|`IsNoMetadataMethod`|
|`IsILStub`|

Update cDAC compat asserts in cDAC to always be enabled by using a tls variable in `mscordaccore`

Implement `GetMethodDescName` on `ISOSDacInterface` in the `cdacreader`

Stub out an implementation of `GetPath` in the `Loader` contract used in a fallback after a fallback. This will need further work, but is included to make sure the code path isn't lost.

Fix the `EcmaMetadataReader` to be able to find blobs in the metadata

Add ability to read target data from a buffer held on the cdac side using the `Target` class. This was needed to handle signature containing a `CorElementType.Internal`.

And finally actually implement the name generation algorithm via a line for line port from the CoreCLR codebase.

Contributes to dotnet#99302

docs/design/datacontracts/RuntimeTypeSystem.md

@@ -92,12 +92,51 @@ struct MethodDescHandle
 }
 ```
 
+```csharp
+public enum ArrayFunctionType
+{
+    Get = 0,
+    Set = 1,
+    Address = 2,
+    Constructor = 3
+}
+```
+
 ```csharp
 partial interface IRuntimeTypeSystem : IContract
 {
     public virtual MethodDescHandle GetMethodDescHandle(TargetPointer methodDescPointer);
 
     public virtual TargetPointer GetMethodTable(MethodDescHandle methodDesc);
+
+    // Return true for an uninstantiated generic method
+    public virtual bool IsGenericMethodDefinition(MethodDescHandle methodDesc);
+
+    public virtual ReadOnlySpan<TypeHandle> GetGenericMethodInstantiation(MethodDescHandle methodDesc);
+
+    // Return mdTokenNil (0x06000000) if the method doesn't have a token, otherwise return the token of the method
+    public virtual uint GetMethodToken(MethodDescHandle methodDesc);
+
+    // Return true if a MethodDesc represents an array method
+    // An array method is also a StoredSigMethodDesc
+    public virtual bool IsArrayMethod(MethodDescHandle methodDesc, out ArrayFunctionType functionType);
+
+    // Return true if a MethodDesc represents a method without metadata method, either an IL Stub dynamically
+    // generated by the runtime, or a MethodDesc that describes a method represented by the System.Reflection.Emit.DynamicMethod class
+    // Or something else similar.
+    // A no metadata method is also a StoredSigMethodDesc
+    public virtual bool IsNoMetadataMethod(MethodDescHandle methodDesc, out ReadOnlySpan<byte> methodName);
+
+    // A StoredSigMethodDesc is a MethodDesc for which the signature isn't found in metadata.
+    public virtual bool IsStoredSigMethodDesc(MethodDescHandle methodDesc, out ReadOnlySpan<byte> signature);
+
+    // Return true for a MethodDesc that describes a method represented by the System.Reflection.Emit.DynamicMethod class
+    // A DynamicMethod is also a StoredSigMethodDesc, and a NoMetadataMethod
+    public virtual bool IsDynamicMethod(MethodDescHandle methodDesc);
+
+    // Return true if a MethodDesc represents an IL Stub dynamically generated by the runtime
+    // A IL Stub method is also a StoredSigMethodDesc, and a NoMetadataMethod
+    public virtual bool IsILStub(MethodDescHandle methodDesc);
 }
 ```
 
@@ -563,7 +602,8 @@ The version 1 `MethodDesc` APIs depend on the `MethodDescAlignment` global and t
 
 | Global name | Meaning |
 | --- | --- |
-| `MethodDescAlignment` | `MethodDescChunk` trailing data is allocated in multiples of this constant.  The size (in bytes) of each `MethodDesc` (or subclass) instance is a multiple of this constant.
+| `MethodDescAlignment` | `MethodDescChunk` trailing data is allocated in multiples of this constant.  The size (in bytes) of each `MethodDesc` (or subclass) instance is a multiple of this constant. |
+| `MethodDescTokenRemainderBitCount` | Number of bits in the token remainder in `MethodDesc` |
 
 
 In the runtime a `MethodDesc` implicitly belongs to a single `MethodDescChunk` and some common data is shared between method descriptors that belong to the same chunk.  A single method table
@@ -572,12 +612,211 @@ will typically have multiple chunks.  There are subkinds of MethodDescs at runti
 We depend on the following data descriptors:
 | Data Descriptor Name | Field | Meaning |
 | --- | --- | --- |
-| `MethodDesc` | `ChunkIndex` | Offset of this `MethodDesc` relative to the end of its containing `MethodDescChunk` - in multiples of `MethodDescAlignment`
-| `MethodDesc` | `Slot` | The method's slot
-| `MethodDesc` | `Flags` | The method's flags
-| `MethodDescChunk` | `MethodTable` | The method table set of methods belongs to
-| `MethodDescChunk` | `Next` | The next chunk of methods
-| `MethodDescChunk` | `Size` | The size of this `MethodDescChunk`  following this `MethodDescChunk` header, minus 1. In multiples of `MethodDescAlignment`
-| `MethodDescChunk` | `Count` | The number of `MethodDesc` entries in this chunk, minus 1.
+| `MethodDesc` | `ChunkIndex` | Offset of this `MethodDesc` relative to the end of its containing `MethodDescChunk` - in multiples of `MethodDescAlignment` |
+| `MethodDesc` | `Slot` | The method's slot |
+| `MethodDesc` | `Flags` | The method's flags |
+| `MethodDesc` | `Flags3AndTokenRemainder` | More flags for the method, and the low bits of the method's token's RID |
+| `MethodDescChunk` | `MethodTable` | The method table set of methods belongs to |
+| `MethodDescChunk` | `Next` | The next chunk of methods |
+| `MethodDescChunk` | `Size` | The size of this `MethodDescChunk`  following this `MethodDescChunk` header, minus 1. In multiples of `MethodDescAlignment` |
+| `MethodDescChunk` | `Count` | The number of `MethodDesc` entries in this chunk, minus 1. |
+| `MethodDescChunk` | `FlagsAndTokenRange` | `MethodDescChunk` flags, and the upper bits of the method token's RID |
+| `InstantiatedMethodDesc` | `PerInstInfo` | The pointer to the method's type arguments |
+| `InstantiatedMethodDesc` | `Flags2` | Flags for the `InstantiatedMethodDesc` |
+| `InstantiatedMethodDesc` | `NumGenericArgs` | How many generic args the method has |
+| `StoredSigMethodDesc` | `Sig` | Pointer to a metadata signature |
+| `StoredSigMethodDesc` | `cSig` | Count of bytes in the metadata signature |
+| `StoredSigMethodDesc` | `ExtendedFlags` | Flags field for the `StoredSigMethodDesc` |
+| `DynamicMethodDesc` | `MethodName` | Pointer to Null-terminated UTF8 string describing the Method desc |
+
+
+And the following enumeration definitions
+
+```csharp
+    internal enum MethodDescClassification
+    {
+        IL = 0, // IL
+        FCall = 1, // FCall (also includes tlbimped ctor, Delegate ctor)
+        PInvoke = 2, // PInvoke method
+        EEImpl = 3, // special method; implementation provided by EE (like Delegate Invoke)
+        Array = 4, // Array ECall
+        Instantiated = 5, // Instantiated generic methods, including descriptors
+                            // for both shared and unshared code (see InstantiatedMethodDesc)
+        ComInterop = 6,
+        Dynamic = 7, // for method desc with no metadata behind
+    }
+
+    [Flags]
+    internal enum MethodDescFlags : ushort
+    {
+        ClassificationMask = 0x7,
+        HasNonVtableSlot = 0x0008,
+    }
+
+    internal enum InstantiatedMethodDescFlags2 : ushort
+    {
+        KindMask = 0x07,
+        GenericMethodDefinition = 0x01,
+        UnsharedMethodInstantiation = 0x02,
+        SharedMethodInstantiation = 0x03,
+        WrapperStubWithInstantiations = 0x04,
+    }
+
+    [Flags]
+    internal enum DynamicMethodDescExtendedFlags : uint
+    {
+        IsLCGMethod = 0x00004000,
+        IsILStub = 0x00008000,
+    }
+```
+
+
+And the various apis are implemented with the following algorithms
+
+```csharp
+    public bool IsGenericMethodDefinition(MethodDescHandle methodDescHandle)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Instantiated)
+            return false;
+
+        ushort Flags2 = // Read Flags2 field from InstantiatedMethodDesc contract using address methodDescHandle.Address
+
+        return ((int)Flags2 & (int)InstantiatedMethodDescFlags2.KindMask) == (int)InstantiatedMethodDescFlags2.GenericMethodDefinition;
+    }
+
+    public ReadOnlySpan<TypeHandle> GetGenericMethodInstantiation(MethodDescHandle methodDescHandle)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Instantiated)
+            return default;
+
+        TargetPointer dictionaryPointer = // Read PerInstInfo field from InstantiatedMethodDesc contract using address methodDescHandle.Address
+        if (dictionaryPointer == 0)
+            return default;
+
+        int NumTypeArgs = // Read NumGenericArgs from methodDescHandle.Address using InstantiatedMethodDesc contract
+        TypeHandle[] instantiation = new TypeHandle[NumTypeArgs];
+        for (int i = 0; i < NumTypeArgs; i++)
+            instantiation[i] = GetTypeHandle(_target.ReadPointer(dictionaryPointer + _target.PointerSize * i));
+
+        return instantiation;
+    }
+
+    public uint GetMethodToken(MethodDescHandle methodDescHandle)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        TargetPointer methodDescChunk = // Using ChunkIndex from methodDesc, compute the wrapping MethodDescChunk
+        
+        ushort Flags3AndTokenRemainder = // Read Flags3AndTokenRemainder field from MethodDesc contract using address methodDescHandle.Address
+
+        ushort FlagsAndTokenRange = // Read FlagsAndTokenRange field from MethodDescChunk contract using address methodDescChunk
 
+        int tokenRemainderBitCount = _target.ReadGlobal<byte>(Constants.Globals.MethodDescTokenRemainderBitCount);
+        int tokenRangeBitCount = 24 - tokenRemainderBitCount;
+        uint allRidBitsSet = 0xFFFFFF;
+        uint tokenRemainderMask = allRidBitsSet >> tokenRangeBitCount;
+        uint tokenRangeMask = allRidBitsSet >> tokenRemainderBitCount;
+
+        uint tokenRemainder = (uint)(_desc.Flags3AndTokenRemainder & tokenRemainderMask);
+        uint tokenRange = ((uint)(_chunk.FlagsAndTokenRange & tokenRangeMask)) << tokenRemainderBitCount;
+
+        return 0x06000000 | tokenRange | tokenRemainder;
+    }
+
+    public bool IsArrayMethod(MethodDescHandle methodDescHandle, out ArrayFunctionType functionType)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Array)
+        {
+            functionType = default;
+            return false;
+        }
+
+        int arrayMethodIndex = methodDesc.Slot - GetNumVtableSlots(GetTypeHandle(methodDesc.MethodTable));
+
+        functionType = arrayMethodIndex switch
+        {
+            0 => ArrayFunctionType.Get,
+            1 => ArrayFunctionType.Set,
+            2 => ArrayFunctionType.Address,
+            > 3 => ArrayFunctionType.Constructor,
+            _ => throw new InvalidOperationException()
+        };
+
+        return true;
+    }
+
+    public bool IsNoMetadataMethod(MethodDescHandle methodDescHandle, out ReadOnlySpan<byte> methodName)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Dynamic)
+        {
+            methodName = default;
+            return false;
+        }
+
+        TargetPointer methodNamePointer = // Read MethodName field from DynamicMethodDesc contract using address methodDescHandle.Address
+
+        methodName = // ReadBuffer from target of a utf8 null terminated string, starting at address methodNamePointer
+        return true;
+    }
+
+    public bool IsStoredSigMethodDesc(MethodDescHandle methodDescHandle, out ReadOnlySpan<byte> signature)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        switch (methodDesc.Classification)
+        {
+            case MethodDescClassification.Dynamic:
+            case MethodDescClassification.EEImpl:
+            case MethodDescClassification.Array:
+                break; // These have stored sigs
+
+            default:
+                signature = default;
+                return false;
+        }
+
+        TargetPointer Sig = // Read Sig field from StoredSigMethodDesc contract using address methodDescHandle.Address
+        uint cSig = // Read cSig field from StoredSigMethodDesc contract using address methodDescHandle.Address
+
+        TargetPointer methodNamePointer = // Read S field from DynamicMethodDesc contract using address methodDescHandle.Address
+        signature = // Read buffer from target memory starting at address Sig, with cSig bytes in it.
+        return true;
+    }
+
+    public bool IsDynamicMethod(MethodDescHandle methodDescHandle)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Dynamic)
+        {
+            return false;
+        }
+
+        uint ExtendedFlags = // Read ExtendedFlags field from StoredSigMethodDesc contract using address methodDescHandle.Address
+
+        return ((DynamicMethodDescExtendedFlags)ExtendedFlags).HasFlag(DynamicMethodDescExtendedFlags.IsLCGMethod);
+    }
+
+    public bool IsILStub(MethodDescHandle methodDescHandle)
+    {
+        MethodDesc methodDesc = _methodDescs[methodDescHandle.Address];
+
+        if (methodDesc.Classification != MethodDescClassification.Dynamic)
+        {
+            return false;
+        }
+
+        uint ExtendedFlags = // Read ExtendedFlags field from StoredSigMethodDesc contract using address methodDescHandle.Address
+
+        return ((DynamicMethodDescExtendedFlags)ExtendedFlags).HasFlag(DynamicMethodDescExtendedFlags.IsILStub);
+    }
+```
 **TODO(cdac)**

src/coreclr/debug/daccess/dacfn.cpp

@@ -1386,6 +1386,15 @@ DacAllocHostOnlyInstance(ULONG32 size, bool throwEx)
     return inst + 1;
 }
 
+thread_local bool t_DacAssertsUnconditionally = false;
+
+bool DacSetEnableDacAssertsUnconditionally(bool enable)
+{
+    bool oldValue = t_DacAssertsUnconditionally;
+    t_DacAssertsUnconditionally = enable;
+    return oldValue;
+}
+
 //
 // Queries whether ASSERTs should be raised when inconsistencies in the target are detected
 //
@@ -1404,6 +1413,10 @@ bool DacTargetConsistencyAssertsEnabled()
         return true;
     }
 
+    // If asserts are unconditionally enabled via the thread local, simply return true.
+    if (t_DacAssertsUnconditionally)
+        return true;
+
     return g_dacImpl->TargetConsistencyAssertsEnabled();
 }
 

src/coreclr/debug/daccess/dacimpl.h

@@ -1245,6 +1245,7 @@ class ClrDataAccess
     HRESULT GetObjectStringDataImpl(CLRDATA_ADDRESS obj, unsigned int count, _Inout_updates_z_(count) WCHAR *stringData, unsigned int *pNeeded);
     HRESULT GetUsefulGlobalsImpl(struct DacpUsefulGlobalsData *globalsData);
     HRESULT GetMethodDescDataImpl(CLRDATA_ADDRESS methodDesc, CLRDATA_ADDRESS ip, struct DacpMethodDescData *data, ULONG cRevertedRejitVersions, DacpReJitData * rgRevertedRejitData, ULONG * pcNeededRevertedRejitData);
+    HRESULT GetMethodDescNameImpl(CLRDATA_ADDRESS methodDesc, unsigned int count, _Inout_updates_z_(count) WCHAR *name, unsigned int *pNeeded);
 
     BOOL IsExceptionFromManagedCode(EXCEPTION_RECORD * pExceptionRecord);
 #ifndef TARGET_UNIX