进入并离开装配体? [英] ENTER and LEAVE in Assembly?

问题描述

我正在阅读汇编语言的艺术(Randall Hyde，链接到Amazon )，我在那本书中尝试了一个控制台应用程序.它是一个使用Win32 API函数为其自身创建了新控制台的程序.该程序包含一个名为LENSTR的过程，该过程将字符串的长度存储在EBP寄存器中.该函数的代码如下:

I was reading The Art of Assembly Language (Randall Hyde, link to Amazon) and I tried out a console application in that book. It was a program that created a new console for itself using Win32 API functions. The program contains a procedure called LENSTR, which stores the length of string in the EBP register. The code for this function is as follows:

LENSTR PROC
ENTER 0, 0
PUSH  EAX
;----------------------
CLD
MOV   EDI, DWORD PTR [EBP+08H]
MOV   EBX, EDI
MOV   ECX, 100 ; Limit the string length
XOR   AL, AL
REPNE SCASB ; Find the 0 character
SUB   EDI, EBX ; String length including 0
MOV   EBX, EDI

DEC   EBX
;----------------------
POP   EAX
LEAVE
RET   4
LENSTR ENDP

您能在这里解释enter和leave命令的用法吗?

Could you explain the usage of the enter and leave commands here?

推荐答案

这是该函数的堆栈框架(激活记录)的设置.内部通常看起来像这样:

This is the setup for the stack frame (activation record) for the function. Internally it normally looks something like this:

push( ebp );         // Save a copy of the old EBP value

mov( esp, ebp );     // Get ptr to base of activation record into EBP

sub( NumVars, esp ); // Allocate storage for local variables.

然后，当要再次销毁堆栈框架时，您必须执行以下操作:

Then when the stack frame is to be destroyed again, you have to do something along the following lines:

   mov( ebp, esp );    // Deallocate locals and clean up stack.

   pop( ebp );         // Restore pointer to caller's activation record.

   ret();              // Return to the caller.

此处是使用HLA对其的更好解释.尽管您正在阅读的书中对它的解释很充分，但我也有这本书，而且我已经阅读了解释它的部分.

Here is a better explanation of it using HLA. Though it is well explained in the book you're reading, as I have that book too, and I've read the section explaining it.

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