Add ldftn and DelegateShim

src/Platforms/Echo.Platforms.AsmResolver/Emulation/CilThread.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using AsmResolver.DotNet;
 using AsmResolver.DotNet.Signatures;
@@ -236,6 +237,14 @@ private void Step(CilExecutionContext context)
             if (CallStack.Peek().IsRoot)
                 throw new CilEmulatorException("No method is currently being executed.");
 
+            if (CallStack.Peek().IsTrampoline)
+            {
+                var trampolineFrame = CallStack.Pop();
+                if (trampolineFrame.Method.Signature!.ReturnsValue)
+                    CallStack.Peek().EvaluationStack.Push(trampolineFrame.EvaluationStack.Pop());
+                return;
+            }
+
             var currentFrame = CallStack.Peek();
             if (currentFrame.Body is not { } body)
                 throw new CilEmulatorException("Emulator only supports managed method bodies.");

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Dispatch/ObjectModel/CallHandlerBase.cs

@@ -241,6 +241,9 @@
 
                     return CilDispatchResult.Success();
 
+                case InvocationResultType.FullyHandled:
+                    return CilDispatchResult.Success();
+
                 case InvocationResultType.Exception:
                     // There was an exception during the invocation. Throw it.
                     return CilDispatchResult.Exception(result.ExceptionObject);
@@ -254,7 +257,7 @@
             }
         }
 
         protected static MethodDefinition? FindMethodImplementationInType(TypeDefinition? type, MethodDefinition? baseMethod)
         {
             if (type is null || baseMethod is null || !baseMethod.IsVirtual)
                 return baseMethod;

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Dispatch/ObjectModel/LdftnHandler.cs

@@ -0,0 +1,26 @@
+using System;
+using AsmResolver.DotNet;
+using AsmResolver.PE.DotNet.Cil;
+
+namespace Echo.Platforms.AsmResolver.Emulation.Dispatch.ObjectModel;
+
+/// <summary>
+/// Implements a CIL instruction handler for <c>ldftn</c> instruction.
+/// </summary>
+[DispatcherTableEntry(CilCode.Ldftn)]
+public class LdftnHandler : FallThroughOpCodeHandler
+{
+    /// <inheritdoc/>
+    protected override CilDispatchResult DispatchInternal(CilExecutionContext context, CilInstruction instruction)
+    {
+        var stack = context.CurrentFrame.EvaluationStack;
+        var factory = context.Machine.ValueFactory;
+        var methods = context.Machine.ValueFactory.ClrMockMemory.MethodEntryPoints;
+        var type = context.Machine.ContextModule.CorLibTypeFactory.IntPtr;
+
+        var functionPointer = methods.GetAddress((IMethodDescriptor)instruction.Operand!);
+        stack.Push(factory.CreateNativeInteger(functionPointer), type);
+
+        return CilDispatchResult.Success();
+    }
+}

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Invocation/DefaultInvokers.cs

@@ -53,6 +53,11 @@ public static class DefaultInvokers
         /// </summary>
         public static UnsafeInvoker UnsafeShim => UnsafeInvoker.Instance;
 
+        /// <summary>
+        /// Gets the default shim for the <see cref="System.Delegate"/> class.
+        /// </summary>
+        public static DelegateInvoker DelegateShim => DelegateInvoker.Instance;
+
         /// <summary>
         /// Gets the default shim for the <see cref="System.Runtime.CompilerServices.RuntimeHelpers"/> class.
         /// </summary>
@@ -96,7 +101,8 @@ public static IMethodInvoker CreateDefaultShims() => StringShim
             .WithFallback(UnsafeShim)
             .WithFallback(RuntimeHelpersShim)
             .WithFallback(IntrinsicsShim)
-            .WithFallback(MemoryMarshalShim);
+            .WithFallback(MemoryMarshalShim)
+            .WithFallback(DelegateShim);
 
         /// <summary>
         /// Chains the first method invoker with the provided method invoker in such a way that if the result of the

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Invocation/DelegateInvoker.cs

@@ -0,0 +1,113 @@
+using System;
+using System.Collections.Generic;
+using AsmResolver.DotNet;
+using AsmResolver.DotNet.Signatures;
+using AsmResolver.PE.DotNet.Cil;
+using Echo.Memory;
+using Echo.Platforms.AsmResolver.Emulation.Dispatch;
+
+namespace Echo.Platforms.AsmResolver.Emulation.Invocation;
+/// <summary>
+/// Wrapper for Delegates
+/// </summary>
+public class DelegateInvoker : IMethodInvoker
+{
+    /// <summary>
+    /// Instance
+    /// </summary>
+    public static DelegateInvoker Instance { get; } = new();
+
+    /// <inheritdoc />
+    public InvocationResult Invoke(CilExecutionContext context, IMethodDescriptor method, IList<BitVector> arguments)
+    {
+        if (method is not { Name: { } name, DeclaringType: { } declaringType, Signature: { } signature })
+            return InvocationResult.Inconclusive();
+
+        if (declaringType.Resolve() is { IsDelegate: false })
+            return InvocationResult.Inconclusive();
+
+        if (method.Name == ".ctor")
+        {
+            return ConstructDelegate(context, arguments);
+        }
+        else if (method.Name == "Invoke")
+        {
+            return InvokeDelegate(context, method, arguments);
+        }
+        else
+        {
+            return InvocationResult.Inconclusive();
+        }
+    }
+
+    private InvocationResult ConstructDelegate(CilExecutionContext context, IList<BitVector> arguments)
+    {
+        var vm = context.Machine;
+        var valueFactory = vm.ValueFactory;
+
+        var self = arguments[0].AsObjectHandle(vm);
+        var obj = arguments[1];
+        var methodPtr = arguments[2];
+
+        self.WriteField(valueFactory.DelegateTargetField, obj);
+        self.WriteField(valueFactory.DelegateMethodPtrField, methodPtr);
+
+        return InvocationResult.StepOver(null);
+    }
+
+    private InvocationResult InvokeDelegate(CilExecutionContext context, IMethodDescriptor invokeMethod, IList<BitVector> arguments)
+    {
+        var vm = context.Machine;
+        var valueFactory = vm.ValueFactory;
+
+        var self = arguments[0].AsObjectHandle(vm);
+
+        var methodPtrFieldValue = self.ReadField(valueFactory.DelegateMethodPtrField);
+
+        if (!methodPtrFieldValue.IsFullyKnown)
+            throw new CilEmulatorException($"Field {self.GetObjectType().FullName}::_methodPtr contains an unknown value. Perhaps delegate was initialised with an error, or memory was corrupted.");
+
+        var methodPtr = methodPtrFieldValue.AsSpan().ReadNativeInteger(vm.Is32Bit);
+
+        if (!valueFactory.ClrMockMemory.MethodEntryPoints.TryGetObject(methodPtr, out var method))
+            throw new CilEmulatorException($"Cant resolve method from {self.GetObjectType().FullName}::_methodPtr. Possible causes: IMethodDescriptor was not mapped by the emulator, or memory was corrupted.");
+
+        var newArguments = new BitVector[method!.Signature!.GetTotalParameterCount()];
+
+        int argumentIndex = 0;
+
+        // read and push this for HasThis methods
+        if (method!.Signature!.HasThis)
+            newArguments[argumentIndex++] = self.ReadField(valueFactory.DelegateTargetField);
+
+        // skip 1 for delegate "this"
+        for (var i = 1; i < arguments.Count; i++)
+            newArguments[argumentIndex++] = arguments[i];
+
+        var result = context.Machine.Invoker.Invoke(context, method, newArguments);
+
+        if (!result.IsSuccess)
+        {
+            // return error
+            return result;
+        }
+        else if (result.ResultType == InvocationResultType.StepOver)
+        {
+            // return value
+            return result;
+        }
+        else if (result.ResultType == InvocationResultType.StepIn)
+        {
+            // create and push the trampoline frame
+            var trampolineFrame = context.Thread.CallStack.Push(invokeMethod);
+            trampolineFrame.IsTrampoline = true;
+
+            // create and push the method for which the delegate was created
+            var frame = context.Thread.CallStack.Push(method);
+            for (int i = 0; i < newArguments.Length; i++)
+                frame.WriteArgument(i, newArguments[i]);
+        }
+
+        return InvocationResult.FullyHandled();
+    }
+}

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Invocation/InvocationResult.cs

@@ -70,7 +70,12 @@ private InvocationResult(InvocationResultType resultType, BitVector? value, Obje
         /// The result that was produced by the method, or <c>null</c> if the method does not return a value.
         /// </param>
         public static InvocationResult StepOver(BitVector? value) => new(InvocationResultType.StepOver, value, default);
-
+
+        /// <summary>
+        /// Constructs a new conclusive invocation result, where the invocation was fully emulated by the invoker.
+        /// </summary>
+        public static InvocationResult FullyHandled() => new(InvocationResultType.FullyHandled, null, default);
+
         /// <summary>
         /// Constructs a new failed invocation result with the provided pointer to an exception object describing the
         /// error that occurred.

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Invocation/InvocationResultType.cs

@@ -10,7 +10,7 @@ public enum InvocationResultType
         /// Indicates the invocation was not handled yet.
         /// </summary>
         Inconclusive,
-        
+
         /// <summary>
         /// Indicates the invocation is handled as a step-in action.
         /// </summary>
@@ -20,7 +20,12 @@ public enum InvocationResultType
         /// Indicates the invocation is handled fully by the invoker.
         /// </summary>
         StepOver,
-
+
+        /// <summary>
+        /// Indicates the invocation is fully emulated by the invoker.
+        /// </summary>
+        FullyHandled,
+
         /// <summary>
         /// Indicates the invocation resulted in an error.
         /// </summary>

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Runtime/ClrMockMemory.cs

@@ -18,15 +18,17 @@ public class ClrMockMemory : IMemorySpace
         /// </summary>
         public ClrMockMemory()
         {
-            _backingBuffer = new VirtualMemory(0x0300_0000);
+            _backingBuffer = new VirtualMemory(0x0400_0000);
 
             MethodTables = new GenericMockMemory<ITypeDescriptor>(0x0100_0000, 0x100, SignatureComparer.Default);
             Methods = new GenericMockMemory<IMethodDescriptor>(0x0100_0000, 0x20, SignatureComparer.Default);
+            MethodEntryPoints = new GenericMockMemory<IMethodDescriptor>(0x0100_0000, 0x10, SignatureComparer.Default);
             Fields = new GenericMockMemory<IFieldDescriptor>(0x0100_0000, 0x20, SignatureComparer.Default);
 
             _backingBuffer.Map(0x0000_0000, MethodTables);
             _backingBuffer.Map(0x0100_0000, Methods);
-            _backingBuffer.Map(0x0200_0000, Fields);
+            _backingBuffer.Map(0x0200_0000, MethodEntryPoints);
+            _backingBuffer.Map(0x0300_0000, Fields);
         }
 
         /// <inheritdoc />
@@ -48,6 +50,14 @@ public GenericMockMemory<IMethodDescriptor> Methods
             get;
         }
 
+        /// <summary>
+        /// Gets the memory assigned for method entry points
+        /// </summary>
+        public GenericMockMemory<IMethodDescriptor> MethodEntryPoints
+        {
+            get;
+        }
+
         /// <summary>
         /// Gets the memory assigned for field descriptor structures.
         /// </summary>

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Stack/CallFrame.cs

@@ -117,6 +117,11 @@ void AllocateFrameField(TypeSignature type)
         /// </summary>
         public bool IsRoot { get; }
 
+        /// <summary>
+        /// Gets a value indicating that the frame is a trampoline, and that it immediately returns the value of the next method on the stack
+        /// </summary>
+        public bool IsTrampoline { get; set; }
+
         /// <summary>
         /// Gets the method which this frame was associated with.
         /// </summary>

src/Platforms/Echo.Platforms.AsmResolver/Emulation/ValueFactory.cs

@@ -46,6 +46,22 @@ public ValueFactory(ModuleDefinition contextModule, bool is32Bit)
             // Force System.String to be aligned at 4 bytes (required for low level string APIs).
             GetTypeDefOrRefContentsLayout(contextModule.CorLibTypeFactory.String.Type, default, 4);
 
+            DelegateType = new TypeReference(
+                contextModule,
+                contextModule.CorLibTypeFactory.CorLibScope,
+                nameof(System),
+                nameof(Delegate)).Resolve()!;
+
+            DelegateTargetField = new MemberReference(
+                (IMemberRefParent)DelegateType,
+                "_target",
+                new FieldSignature(contextModule.CorLibTypeFactory.Object));
+
+            DelegateMethodPtrField = new MemberReference(
+                (IMemberRefParent)DelegateType,
+                "_methodPtr",
+                new FieldSignature(contextModule.CorLibTypeFactory.IntPtr));
+
             DecimalType = new TypeReference(
                 contextModule, 
                 contextModule.CorLibTypeFactory.CorLibScope, 
@@ -147,6 +163,30 @@ public ITypeDescriptor DecimalType
             get;
         }
 
+        /// <summary>
+        /// Gets a reference to the <see cref="Delegate"/> type. 
+        /// </summary>
+        public ITypeDescriptor DelegateType
+        {
+            get;
+        }
+
+        /// <summary>
+        /// Get a reference to the <see cref="Delegate"/> _target field.
+        /// </summary>
+        public IFieldDescriptor DelegateTargetField
+        {
+            get;
+        }
+
+        /// <summary>
+        /// Get a reference to the <see cref="Delegate"/> _methodPtr field.
+        /// </summary>
+        public IFieldDescriptor DelegateMethodPtrField
+        {
+            get;
+        }
+
         /// <summary>
         /// Gets a reference to the <see cref="InvalidProgramException"/> type. 
         /// </summary>

test/Platforms/Echo.Platforms.AsmResolver.Tests/Emulation/CilVirtualMachineTest.cs

@@ -603,7 +603,7 @@
 
             // Verify.
             Assert.NotNull(result);
             Assert.Equal(1337, result.AsSpan().I32);
         }
 
         [Fact]
@@ -662,5 +662,53 @@
             _mainThread.Step();
             Assert.Equal(instructions[3].Offset, frame.ProgramCounter);
         }
+
+        [Fact]
+        public void CallDelegate()
+        {
+            var method = _fixture.MockModule
+                    .LookupMember<TypeDefinition>(typeof(TestClass).MetadataToken)
+                    .Methods.First(m => m.Name == nameof(TestClass.TestDelegateCall));
+
+            _vm.Invoker = DefaultInvokers.DelegateShim.WithFallback(DefaultInvokers.StepIn);
+            _mainThread.CallStack.Push(method);
+
+            var instructions = method.CilMethodBody!.Instructions;
+
+            var callDelegateOffset = instructions.First(instruction => instruction.OpCode.Code == CilCode.Callvirt).Offset;
+
+            _mainThread.StepWhile(CancellationToken.None, context => context.CurrentFrame.ProgramCounter != callDelegateOffset);
+            _mainThread.Step(); // call delegate::invoke
+            // callstack:
+            // (0) root -> (1) TestClass::TestDelegateCall -> (2) ReturnAnyIntDelegate::Invoke -> (3) TestClass::ReturnAnyInt
+            Assert.Equal(4, _mainThread.CallStack.Count);
+
+            _mainThread.StepOut();
+            // callstack:
+            // (0) root -> (1) TestClass::TestDelegateCall -> (2) ReturnAnyIntDelegate::Invoke
+            // evaluation stack:
+            // (0) i32: 5
+            Assert.Equal(3, _mainThread.CallStack.Count);
+            Assert.Single(_mainThread.CallStack.Peek().EvaluationStack);
+            Assert.Equal(5, _mainThread.CallStack.Peek().EvaluationStack.Peek().Contents.AsSpan().I32);
+
+            _mainThread.StepOut();
+            // callstack:
+            // (0) root -> (1) TestClass::TestDelegateCall
+            // evaluation stack:
+            // (0) i32: 5
+            Assert.Equal(2, _mainThread.CallStack.Count);
+            Assert.Single(_mainThread.CallStack.Peek().EvaluationStack);
+            Assert.Equal(5, _mainThread.CallStack.Peek().EvaluationStack.Peek().Contents.AsSpan().I32);
+
+            _mainThread.StepOut();
+            // callstack:
+            // (0) root
+            // evaluation stack:
+            // (0) i32: 5
+            Assert.Single(_mainThread.CallStack);
+            Assert.Single(_mainThread.CallStack.Peek().EvaluationStack);
+            Assert.Equal(5, _mainThread.CallStack.Peek().EvaluationStack.Peek().Contents.AsSpan().I32);
+        }
     }
 }