通过动态方法解析IL中发现的令牌

Question

感谢Hans Passant在这里回答我的问题： How do I get an IL bytearray from a DynamicMethod?

我能够起床并跑步。我现在正在尝试解决在IL发出的元数据令牌，以查看正在调用哪些方法，或者什么不是。我能够解决方法体中的下一个标记是一个调用。我正在使用Mono.Reflection的MethodBodyReader中的一些代码。

static byte[] GetILByteArray(Delegate @delegate){
   // does stuff mentioned in other thread
}
...
Expression<Action> foo = () => Console.WriteLine(0);
var compiled = foo.Compile();
var bytes = GetILByteArray(compiled);
int index =Array.FindIndex(bytes,b=>GetOpCode(b).OperandType == OperandType.InlineMethod);
var token = BitConverter.ToInt32(bytes,index+1);
compiled.Method.Module.ResolveMember(token);

抛出异常，说明该域中的令牌是不可解析的。这里有人有诀窍吗？我应该尝试传递代理通用参数还是完全没用？

我目前正在考虑为表达式树的代表编写反编译器的想法，我真的希望能够使用我自己编译为测试用例的表达式树，因为我总是可以回到原始状态并比较。

Answer 1

答案是您必须使用DynamicMethod.m_resolver来解析动态方法的令牌，而不是使用Module。这是有道理的，因为DynamicMethod.m_resolver.m_code是where you should be getting the IL byte array from。

这很困难，因为DynamicResolver.ResolveToken返回IntPtr并将其转回RuntimeTypeHandle和RuntimeMethodHandle等，需要进行大量反思。这个解决方案不太可能在.NET 4.x运行时中断，但要注意任何主要的版本更改。

没有简洁的方法来表达这一点。

定义并使用此界面而不是Module来解析令牌：

public interface ITokenResolver
{
    MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments);
    Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments);
    FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments);
    MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments);
    byte[] ResolveSignature(int metadataToken);
    string ResolveString(int metadataToken);
}

对于非动态方法：

public sealed class ModuleTokenResolver : ITokenResolver
{
    private readonly Module module;

    public ModuleTokenResolver(Module module)
    {
        this.module = module;
    }

    public MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) =>
        module.ResolveMember(metadataToken, genericTypeArguments, genericMethodArguments);

    public Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) =>
        module.ResolveType(metadataToken, genericTypeArguments, genericMethodArguments);

    public FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) =>
        module.ResolveField(metadataToken, genericTypeArguments, genericMethodArguments);

    public MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) =>
        module.ResolveMethod(metadataToken, genericTypeArguments, genericMethodArguments);

    public byte[] ResolveSignature(int metadataToken) =>
        module.ResolveSignature(metadataToken);

    public string ResolveString(int metadataToken) =>
        module.ResolveString(metadataToken);
}

对于动态方法：

public sealed class DynamicMethodTokenResolver : ITokenResolver
{
    private delegate void TokenResolver(int token, out IntPtr typeHandle, out IntPtr methodHandle, out IntPtr fieldHandle);
    private delegate string StringResolver(int token);
    private delegate byte[] SignatureResolver(int token, int fromMethod);
    private delegate Type GetTypeFromHandleUnsafe(IntPtr handle);

    private readonly TokenResolver tokenResolver;
    private readonly StringResolver stringResolver;
    private readonly SignatureResolver signatureResolver;
    private readonly GetTypeFromHandleUnsafe getTypeFromHandleUnsafe;
    private readonly MethodInfo getMethodBase;
    private readonly ConstructorInfo runtimeMethodHandleInternalCtor;
    private readonly ConstructorInfo runtimeFieldHandleStubCtor;
    private readonly MethodInfo getFieldInfo;

    public DynamicMethodTokenResolver(DynamicMethod dynamicMethod)
    {
        var resolver = typeof(DynamicMethod).GetField("m_resolver", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(dynamicMethod);
        if (resolver == null) throw new ArgumentException("The dynamic method's IL has not been finalized.");

        tokenResolver = (TokenResolver)resolver.GetType().GetMethod("ResolveToken", BindingFlags.Instance | BindingFlags.NonPublic).CreateDelegate(typeof(TokenResolver), resolver);
        stringResolver = (StringResolver)resolver.GetType().GetMethod("GetStringLiteral", BindingFlags.Instance | BindingFlags.NonPublic).CreateDelegate(typeof(StringResolver), resolver);
        signatureResolver = (SignatureResolver)resolver.GetType().GetMethod("ResolveSignature", BindingFlags.Instance | BindingFlags.NonPublic).CreateDelegate(typeof(SignatureResolver), resolver);

        getTypeFromHandleUnsafe = (GetTypeFromHandleUnsafe)typeof(Type).GetMethod("GetTypeFromHandleUnsafe", BindingFlags.Static | BindingFlags.NonPublic, null, new[] { typeof(IntPtr) }, null).CreateDelegate(typeof(GetTypeFromHandleUnsafe), null);
        var runtimeType = typeof(RuntimeTypeHandle).Assembly.GetType("System.RuntimeType");

        var runtimeMethodHandleInternal = typeof(RuntimeTypeHandle).Assembly.GetType("System.RuntimeMethodHandleInternal");
        getMethodBase = runtimeType.GetMethod("GetMethodBase", BindingFlags.Static | BindingFlags.NonPublic, null, new[] { runtimeType, runtimeMethodHandleInternal }, null);
        runtimeMethodHandleInternalCtor = runtimeMethodHandleInternal.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(IntPtr) }, null);

        var runtimeFieldInfoStub = typeof(RuntimeTypeHandle).Assembly.GetType("System.RuntimeFieldInfoStub");
        runtimeFieldHandleStubCtor = runtimeFieldInfoStub.GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, new[] { typeof(IntPtr), typeof(object) }, null);
        getFieldInfo = runtimeType.GetMethod("GetFieldInfo", BindingFlags.Static | BindingFlags.NonPublic, null, new[] { runtimeType, typeof(RuntimeTypeHandle).Assembly.GetType("System.IRuntimeFieldInfo") }, null);
    }

    public Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
    {
        IntPtr typeHandle, methodHandle, fieldHandle;
        tokenResolver.Invoke(metadataToken, out typeHandle, out methodHandle, out fieldHandle);

        return getTypeFromHandleUnsafe.Invoke(typeHandle);
    }

    public MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
    {
        IntPtr typeHandle, methodHandle, fieldHandle;
        tokenResolver.Invoke(metadataToken, out typeHandle, out methodHandle, out fieldHandle);

        return (MethodBase)getMethodBase.Invoke(null, new[]
        {
            typeHandle == IntPtr.Zero ? null : getTypeFromHandleUnsafe.Invoke(typeHandle),
            runtimeMethodHandleInternalCtor.Invoke(new object[] { methodHandle })
        });
    }

    public FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
    {
        IntPtr typeHandle, methodHandle, fieldHandle;
        tokenResolver.Invoke(metadataToken, out typeHandle, out methodHandle, out fieldHandle);

        return (FieldInfo)getFieldInfo.Invoke(null, new[]
        {
            typeHandle == IntPtr.Zero ? null : getTypeFromHandleUnsafe.Invoke(typeHandle),
            runtimeFieldHandleStubCtor.Invoke(new object[] { fieldHandle, null })
        });
    }

    public MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
    {
        IntPtr typeHandle, methodHandle, fieldHandle;
        tokenResolver.Invoke(metadataToken, out typeHandle, out methodHandle, out fieldHandle);

        if (methodHandle != IntPtr.Zero)
        {
            return (MethodBase)getMethodBase.Invoke(null, new[]
            {
                typeHandle == IntPtr.Zero ? null : getTypeFromHandleUnsafe.Invoke(typeHandle),
                runtimeMethodHandleInternalCtor.Invoke(new object[] { methodHandle })
            });
        }

        if (fieldHandle != IntPtr.Zero)
        {
            return (FieldInfo)getFieldInfo.Invoke(null, new[]
            {
                typeHandle == IntPtr.Zero ? null : getTypeFromHandleUnsafe.Invoke(typeHandle),
                runtimeFieldHandleStubCtor.Invoke(new object[] { fieldHandle, null })
            });
        }

        if (typeHandle != IntPtr.Zero)
        {
            return getTypeFromHandleUnsafe.Invoke(typeHandle);
        }

        throw new NotImplementedException("DynamicMethods are not able to reference members by token other than types, methods and fields.");
    }

    public byte[] ResolveSignature(int metadataToken)
    {
        return signatureResolver.Invoke(metadataToken, 0);
    }

    public string ResolveString(int metadataToken)
    {
        return stringResolver.Invoke(metadataToken);
    }
}

这是检测动态方法的方法，以及一些辅助方法：

public static class ReflectionExtensions
{
    public static bool IsLightweightMethod(this MethodBase method)
    {
        return method is DynamicMethod || typeof(DynamicMethod).GetNestedType("RTDynamicMethod", BindingFlags.NonPublic).IsInstanceOfType(method);
    }

    public static ITokenResolver GetTokenResolver(this MethodBase method)
    {
        var dynamicMethod = TryGetDynamicMethod(method as MethodInfo) ?? method as DynamicMethod;
        return dynamicMethod != null
            ? new DynamicMethodTokenResolver(dynamicMethod)
            : (ITokenResolver)new ModuleTokenResolver(method.Module);
    }

    public static byte[] GetILBytes(this MethodBase method)
    {
        var dynamicMethod = TryGetDynamicMethod(method as MethodInfo) ?? method as DynamicMethod;
        return dynamicMethod != null
            ? GetILBytes(dynamicMethod)
            : method.GetMethodBody()?.GetILAsByteArray();
    }

    public static byte[] GetILBytes(DynamicMethod dynamicMethod)
    {
        var resolver = typeof(DynamicMethod).GetField("m_resolver", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(dynamicMethod);
        if (resolver == null) throw new ArgumentException("The dynamic method's IL has not been finalized.");
        return (byte[])resolver.GetType().GetField("m_code", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(resolver);
    }

    public static DynamicMethod TryGetDynamicMethod(MethodInfo rtDynamicMethod)
    {
        var typeRTDynamicMethod = typeof(DynamicMethod).GetNestedType("RTDynamicMethod", BindingFlags.NonPublic);
        return typeRTDynamicMethod.IsInstanceOfType(rtDynamicMethod)
            ? (DynamicMethod)typeRTDynamicMethod.GetField("m_owner", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(rtDynamicMethod)
            : null;
    }
}