.NET CIL操作评估堆栈 [英] .NET CIL manipulation of evaluation stack

问题描述

我有此序列的CIL代码，这些代码是通过 Mono.Cecil 注入的。但是，修改后的.NET C＃应用程序将无法运行。

I have this sequence of CIL codes which I injected through the use of Mono.Cecil. However, the modified .NET C# application will not run.

目标：
从堆栈中手动加载和弹出值以在<$ c $中显示c> Console.WriteLine

Objective: Manually load and pop values from stack to display in Console.WriteLine

 for (int i = 0; i < 3; i++)
        {
            int z = some value popped manually from stack;                 
            Console.WriteLine(z);
        }

这是我修改的简单main（）程序：

.method private hidebysig static void Main(string[] args) cil managed
{

    .entrypoint
    .maxstack 5
    .locals init (
        [0] int32 num,
        [1] int32 num2)
    L_0000: ldc.i4.6 //manually push value 6 to stack
    L_0001: ldc.i4.5 //manually push value 5 to stack
    L_0002: ldc.i4.4 //manually push value 4 to stack
    L_0003: ldc.i4.0 //push int i initial value 0 to stack 
    L_0004: stloc.0 //pop and store to int i variable to variable num
    L_0005: br.s L_0013
    L_0007: nop 
    L_0008: stloc.1 //pop the pushed values 6,5 and 4 to variable num2
    L_0009: ldloc.1 //load value of num2 to stack
    L_000a: call void [mscorlib]System.Console::WriteLine(int32) //pop value of num2 and print
    L_000f: ldloc.0 //load previous value in variable num to stack
    L_0010: ldc.i4.1 //load incremental value 1 to stack
    L_0011: add //pop and add the top 2 values, result is pushed to stack
    L_0012: stloc.0 //store the new result to variable num. (int i)
    L_0013: ldloc.0 //push int i variable value to stack
    L_0014: ldc.i4.3 //push value 3 to stack as number of times to loop
    L_0015: blt.s L_0007 //branch less than (pop and cmp the top 2 values in stack)
    L_0017: ret 
}

但是，以上代码无法运行。我尝试将 blt.s 更改为 clt 和 br_true.s 但它也不起作用。有人知道是否有可能实现我的目标？谢谢。

However, the above code cannnot run. I tried changing blt.s to clt and br_true.s but it doesn't work either. Does anyone know if it is possible to attain my objective? Thanks.

编辑：
根据ECMA-335，III.1.7.5，可能存在向后分支约束。不确定是否是这种情况。

According to ECMA-335, III.1.7.5, there might be a backward branch constraint. Not sure if this is the case.

特别是，如果单遍分析到达一条指令，则将其称为位置X，即
立即跟随无条件分支，并且如果X不是较早分支
指令的目标，那么显然不能从现有
信息中得出X处评估堆栈的状态。在这种情况下，CLI要求X处的评估堆栈为空。

In particular, if that single-pass analysis arrives at an instruction, call it location X, that immediately follows an unconditional branch, and where X is not the target of an earlier branch instruction, then the state of the evaluation stack at X, clearly, cannot be derived from existing information. In this case, the CLI demands that the evaluation stack at X be empty.

推荐答案

您IL代码看起来还可以，但是我认为CLR可能无法在方法完成后检查堆栈是否已损坏。将某些内容压入堆栈时，CLR会检查该值是否也从堆栈中弹出。

You IL-Code looks ok, but i think the CLR might not be able to check if the stack is corrupted after the method completes. When something is pushed onto the stack, the CLR checks if the value are also popped from the stack.

因此，如果将3个值压入堆栈，则CLR可能不会能够检查循环是否正在运行3次，因此CLR不知道在方法返回时堆栈上是否还有值。

So if you push 3 values onto the stack the CLR not might be able to check if your loop is running three times, so the CLR doesn't know if there are still values onto the stack when the method is returning.

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