private void PatchMethod(InjectInfo inject, MethodDefinition targetMethod, ILProcessor il, List <Instruction> patchBody)
{
// Time to actually apply the patch at its injection points
var atList = FindInjectionPoint(inject, targetMethod);
// If the amount of injection points does not match expectations, abort - target code has likely changed
if (atList.Count != inject.ExpectedInjections)
{
throw new MixinInjectionException("Expected an injection count of " + inject.ExpectedInjections + " but got " + atList.Count + " candidates in " + targetMethod.FullName + " at " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName, targetMethod);
}
// Update all jumps to injection point(s) to now jump to our hook instead (so they won't just skip past us)
foreach (var at in atList)
{
var newLabelTarget = patchBody[0];
foreach (var inst in targetMethod.Body.Instructions)
{
if (inst.OpCode.OperandType == OperandType.InlineBrTarget || inst.OpCode.OperandType == OperandType.ShortInlineBrTarget)
{
if (inst.Operand == at)
{
inst.Operand = newLabelTarget;
}
}
}
il.InsertBefore(at, patchBody);
}
}
private void ApplyInjectSimple(InjectInfo inject, MethodDefinition targetMethod)
{
List <VariableDefinition> capturedLocals, storedLocals;
var callbackMethod = CreateCallbackMethod(inject, targetMethod, null, out capturedLocals, out storedLocals);
// Time to build patch
var il = targetMethod.Body.GetILProcessor();
// ReSharper disable once UseObjectOrCollectionInitializer
var insnList = new List <Instruction>();
// 2. Load this, all parameters and the captured locals onto the stack and call the callback Method
insnList.Add(il.CreateLdarg(0));
for (int i = 0; i < targetMethod.Parameters.Count; i++)
{
insnList.Add(il.CreateLdarg(i + 1));
}
insnList.AddRange(capturedLocals.Select(local => il.CreateLdloc(local, local.Index)));
insnList.AddRange(storedLocals.Select(local => local.Index > byte.MaxValue
? il.Create(OpCodes.Ldloca, local)
: il.Create(OpCodes.Ldloca_S, local)));
insnList.Add(il.Create(OpCodes.Call, callbackMethod));
PatchMethod(inject, targetMethod, il, insnList);
}
/// <summary>
/// Returns a list of injection points based on the InjectInfo passed to the function.
/// * For HEAD, the injection point will always be the first instruction, and there will only be one at all times.
/// * For RETURN, there will be one injection point per ret opcode. The injection point will be moved right before something is loaded onto the stack.
/// * Anything else is interpreted as IL-Code and will result in one injection point per matching instruction. The injection point will be moved right before something is loaded onto the stack.
/// </summary>
/// <returns>A list of instructions each serving as an injection point.</returns>
private List <Instruction> FindInjectionPoint(InjectInfo inject, MethodDefinition targetMethod)
{
var list = new List <Instruction>();
switch (inject.At)
{
case "HEAD":
list.Add(targetMethod.Body.Instructions[0]);
break;
case "RETURN":
foreach (var inst in targetMethod.Body.Instructions)
{
if (inst.OpCode == OpCodes.Ret)
{
var found = inst;
while (found.Previous != null && found.Previous.IsLdInstruction(_targetModule))
{
found = found.Previous;
}
list.Add(found);
}
}
break;
default:
foreach (var inst in targetMethod.Body.Instructions)
{
string instString = inst.ToString();
if (inject.At == instString)
{
var found = inst;
while (found.Previous != null && found.Previous.IsLdInstruction(_targetModule))
{
found = found.Previous;
}
list.Add(found);
break;
}
}
break;
}
return(list);
}
private MethodDefinition CreateCallbackMethod(InjectInfo inject, MethodDefinition targetMethod, IMetadataTokenProvider callbackInfoType, out List <VariableDefinition> capturedLocals, out List <VariableDefinition> storedLocals)
{
if (!CompareMethodParams(targetMethod, inject.NewMethod, callbackInfoType))
{
throw new MixinException("Target Method has mismatching parameters " + targetMethod.ReturnType.FullName + " At " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName);
}
var callbackMethod = new MethodDefinition(_mixin.MixinContainer.Name + "_" + inject.NewMethod.Name, MethodAttributes.HideBySig, _targetModule.TypeSystem.Void);
TransferMethod(callbackMethod, inject.NewMethod);
GrabLocalParameters(targetMethod, callbackMethod, out capturedLocals, out storedLocals);
_targetType.Methods.Add(callbackMethod);
return(callbackMethod);
}
private void ApplyInject(InjectInfo inject)
{
var targetMethod = _targetType.Methods.SingleOrDefault(t => t.FullName == inject.Method);
if (targetMethod == null)
{
throw new MixinException("Target Method '" + inject.Method + "' not found in target module for [Inject] At " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName);
}
if (inject.Cancellable)
{
ApplyInjectCancellable(inject, targetMethod);
}
else
{
ApplyInjectSimple(inject, targetMethod);
}
}
private void ApplyInjectCancellable(InjectInfo inject, MethodDefinition targetMethod)
{
// Ensure the patch method has parameters - Cancellable means the last parameter MUST be CallbackInfo or CallbackInfoReturnable
if (inject.NewMethod.Parameters.Count == 0)
{
throw new MixinException("Expected last parameter of " + inject.NewMethod.FullName + " to be CallbackInfo or CallbackInfoReturnable in " + _mixin.MixinContainer.FullName);
}
// Retrieve the CallbackInfo Type from the last parameter of the patch Method
var callbackInfoType = inject.NewMethod.Parameters.Last().ParameterType;
var callbackInfoTypeDef = callbackInfoType.Resolve();
// Ensure the last parameter is indeed CallbackInfo or CallbackInfoReturnable
if (callbackInfoType.FullName != typeof(CallbackInfo).FullName && (callbackInfoTypeDef.BaseType == null || callbackInfoTypeDef.BaseType.FullName != typeof(CallbackInfo).FullName))
{
// TODO string comp not needed, patch knows these attributes
throw new MixinException("Expected last parameter of " + inject.NewMethod.FullName + " to be CallbackInfo or CallbackInfoReturnable in " + _mixin.MixinContainer.FullName);
}
// If CallbackInfo is a generic instance (so CallbackInfoReturnable), ensure the return Type matches
if (callbackInfoType.IsGenericInstance)
{
if (targetMethod.ReturnType.FullName != ((GenericInstanceType)callbackInfoType).GenericArguments[0].FullName)
{
throw new MixinException("Target Method has mismatching return Type " + targetMethod.ReturnType.FullName + " at " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName);
}
}
else if (targetMethod.ReturnType != _targetModule.TypeSystem.Void)
{
// It's not CallbackInfoReturnable even though the Method has a return value, this is not allowed
throw new MixinException("Target Method has return Type " + targetMethod.ReturnType.FullName + " but CallbackInfo was specified, expected CallbackInfoReturnable at " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName);
}
List <VariableDefinition> capturedLocals, storedLocals;
var callbackMethod = CreateCallbackMethod(inject, targetMethod, callbackInfoType, out capturedLocals, out storedLocals);
// Append a local variable for the CallbackInfo to the target method (this is where we store the CallbackInfo object that is passed to the injected hook)
var callbackInfo = new VariableDefinition(_targetModule.ImportReference(callbackInfoType));
int callbackInfoIndex = targetMethod.Body.Variables.Count;
targetMethod.Body.Variables.Add(callbackInfo);
// Grab the CallbackInfo constructor (gets a generic constructor for CallbackInfoReturnable)
MethodReference callbackInfoConstructor = callbackInfoTypeDef.Methods.Single(m => m.IsConstructor);
if (callbackInfoType.IsGenericInstance)
{
callbackInfoConstructor = callbackInfoConstructor.MakeHostInstanceGeneric(targetMethod.ReturnType);
}
callbackInfoConstructor = _targetModule.ImportReference(callbackInfoConstructor);
// Time to build patch
var il = targetMethod.Body.GetILProcessor();
// ReSharper disable once UseObjectOrCollectionInitializer
var insnList = new List <Instruction>();
// 1. Create CallbackInfo object and store it as a local
insnList.Add(il.Create(OpCodes.Newobj, callbackInfoConstructor));
insnList.Add(il.CreateStloc(callbackInfo, callbackInfoIndex));
// 2. Load this, all parameters, the CallbackInfo, and the captured locals onto the stack and call the callback Method
insnList.Add(il.CreateLdarg(0));
for (int i = 0; i < targetMethod.Parameters.Count; i++)
{
insnList.Add(il.CreateLdarg(i + 1));
}
insnList.Add(il.CreateLdloc(callbackInfo, callbackInfoIndex));
insnList.AddRange(capturedLocals.Select(local => il.CreateLdloc(local, local.Index)));
insnList.AddRange(storedLocals.Select(local => local.Index > byte.MaxValue
? il.Create(OpCodes.Ldloca, local)
: il.Create(OpCodes.Ldloca_S, local)));
insnList.Add(il.Create(OpCodes.Call, callbackMethod));
// 3. If CallbackInfo was cancelled, return here, possibly with return value. Otherwise, skip until after the return to continue normally.
insnList.Add(il.CreateLdloc(callbackInfo, callbackInfoIndex));
insnList.Add(callbackInfoType.IsGenericInstance
? il.Create(OpCodes.Callvirt, _targetModule.ImportReference(callbackInfoTypeDef.BaseType.Resolve().Methods.Single(m => m.Name == "get_IsCancelled")))
: il.Create(OpCodes.Callvirt, _targetModule.ImportReference(callbackInfoTypeDef.Methods.Single(m => m.Name == "get_IsCancelled"))));
if (inject.CancelTarget == "ret")
{
// 3.1. In case of a 'ret' cancel target, we want to exit the function - if cancelled, jump to the NOP after the RET, otherwise just run into the RET and grab the return value if necessary.
var nopAfterReturn = il.Create(OpCodes.Nop);
insnList.Add(il.Create(OpCodes.Brfalse, nopAfterReturn));
if (targetMethod.ReturnType != _targetModule.TypeSystem.Void)
{
insnList.Add(il.CreateLdloc(callbackInfo, callbackInfoIndex));
insnList.Add(il.Create(OpCodes.Callvirt, _targetModule.ImportReference(callbackInfoTypeDef.Methods.Single(m => m.Name == "get_ReturnValue").MakeHostInstanceGeneric(targetMethod.ReturnType))));
}
insnList.Add(il.Create(OpCodes.Ret));
insnList.Add(nopAfterReturn);
}
else
{
// 3.2. This means the hook wants us to jump somewhere else within the function (as in, any other instruction traced back to empty stack)
Instruction found = null;
foreach (var inst in targetMethod.Body.Instructions)
{
string instString = inst.ToString();
if (inject.CancelTarget == instString)
{
found = inst;
while (found.Previous != null && found.Previous.IsLdInstruction(_targetModule))
{
found = found.Previous;
}
}
}
if (found == null)
{
throw new MixinException("Could not find cancel target '" + inject.CancelTarget + "' in " + targetMethod.FullName + " at " + inject.NewMethod.FullName + " in " + _mixin.MixinContainer.FullName);
}
insnList.Add(il.Create(OpCodes.Brtrue, found));
}
PatchMethod(inject, targetMethod, il, insnList);
}