x86程序集寄存器地址

Question

我试图自己做，但我无法正确管理它。以下是我的考试问题，我想要正确地做并理解它是如何运作的。如果你能帮助我，我将不胜感激。

确定目标（寄存器或存储器地址）以及以下程序片段的每条指令所存储的值：

mov eax, 0x8000
mov ebx, 0x40000
lea esp, [ebx]
shl eax, 16
sar ebx, 23
lea ecx, [ebx+0xff]
push    ecx
sar eax, 31
push    eax
mov eax, [esp+4]
sub eax, [esp]

Answer 1

注释您的代码：

mov eax, 0x8000      ; Move the 32-bit value 0x8000 into register eax
mov ebx, 0x40000     ; Move the 32-bit value 0x40000 into register ebx
lea esp, [ebx]       ; Load the value of register ebx into register esp
shl eax, 16          ; Take the value of register eax, shift left 16 bits, and store back into eax
sar ebx, 23          ; Take the value of register ebx, shift right 23 bits (copying sign bit), and store back into ebx
lea ecx, [ebx+0xff]  ; Load the value of (register ebx) + 0xFF into register ecx
push    ecx          ; Push the value of register ecx onto the stack (the memory near the address of the value of register esp)
sar eax, 31          ; Take the value of register ebx, shift right 31 bits (copying sign bit), and store back into ebx
push    eax          ; Push the value of register eax onto the stack
mov eax, [esp+4]     ; Move the vaule of register the memory at address (esp + 4) and store into eax
sub eax, [esp]       ; Subtract the value of the memory at address esp from eax and store into eax

Answer 2

这是intel汇编语法，因此每一行始终是

instruction destination source

eax，esp等都是注册名称。

数字被解释为数字常量。

[ expression ]

可用于计算地址，然后从该地址加载值。

我很乐观你可以通过阅读obvious wikipedia page来解决这个问题（并学到更多），甚至可以链接到a whole wikibook on x86 assembler。