/// <summary> /// This method starts from an API call instruction and goes backward to locate the instruction that /// pushes the "this" object into stack. We insert out instrumentation patch at that point so that /// the interception method can access the "this" object. After the interception method ends, we /// push the "this" object to stack again so that the original API call can continue. /// </summary> /// <param name="callInstruction">Instruction that calls the API.</param> /// <returns>The instruction that pushes the "this" object into stack.</returns> private Instruction LocateLoadThisInstruction(Instruction callInstruction) { Tuple <int, int> poppedPushed = MSILHelper.GetStackTransition(callInstruction); int toPop = poppedPushed.Item1; Instruction current = callInstruction.Previous; while (toPop > 1) { poppedPushed = MSILHelper.GetStackTransition(current); toPop += poppedPushed.Item1; toPop -= poppedPushed.Item2; current = current.Previous; } return(current); }
public static Instruction LocateLoadThisInstruction(ILProcessor ilProcessor, Instruction callInstruction) { Dictionary <Instruction, int> stackSize = new Dictionary <Instruction, int>(); Tuple <int, int> poppedPushed = MSILHelper.GetStackTransition(callInstruction); int toPop = poppedPushed.Item1; stackSize[callInstruction] = toPop; if (callInstruction.Previous == null) { ilProcessor.InsertBefore(callInstruction, ilProcessor.Create(OpCodes.Nop)); } Instruction current = callInstruction.Previous; // fail if there current is a branch instruction if (current.OpCode.FlowControl != FlowControl.Next) { return(null); } while (toPop > 1) { if (IsStackEmptyingInstruction(current)) { Instruction branchSrc; Instruction branchDst; GetNextBranchDestinationInstruction(current, callInstruction, out branchSrc, out branchDst); if (branchDst != null) { current = branchSrc; toPop = stackSize[branchDst]; } } poppedPushed = MSILHelper.GetStackTransition(current); toPop += poppedPushed.Item1; toPop -= poppedPushed.Item2; stackSize[current] = toPop; if (current.Previous == null) { ilProcessor.InsertBefore(current, ilProcessor.Create(OpCodes.Nop)); } current = current.Previous; // fail if there current is a branch instruction if (current.OpCode.FlowControl != FlowControl.Next) { return(null); } } if (current.OpCode == OpCodes.Constrained) { current = current.Previous; // fail if there current is a branch instruction if (current.OpCode.FlowControl != FlowControl.Next) { return(null); } } return(current); }