Implementation of functions of the Assembly Language Learning Series and assembly language functions

Implementation of functions of the Assembly Language Learning Series and assembly language functions

The following code is used to demonstrate functions that exchange integers a and B. The compiling environment is Ubuntu14.04 (32-bit)

If you want to implement the following C code

#include <stdio.h>void swap(int *xp, int *yp){    int x = *xp;    int y = *yp;        *xp = y;    *yp = x;}int main(){    int a = 534, b = 1057;    swap(&a, &b);    printf("%d\n", a);    printf("%d\n", b);    return 0;}

• The Assembly Code is as follows:

. Section. data :. int 534 B :. int 1057 format :. asciz "% d \ n ". section. text. global _ start_start: pushl % ebp movl % esp, % ebp subl $24, % esp # allocate 24 bytes of memory to the stack to save the local variables movl $ a, % eax movl % eax, 4 (% esp) movl $ B, % eax movl % eax, (% esp) call swap # call the swap function pushl a # print a pushl $ format call printf pushl B # print B pushl $ format call printf movl $0, (% esp) call exit swap: pushl % ebp # Save the pre-call stack frame address movl % esp, % ebp pushl % ebx # Save the register ebx movl 8 (% ebp) according to your habits ), % edx # get xp movl 12 (% ebp), % ecx # get yp movl (% edx), % ebx # get x movl (% ecx ), % eax # get y movl % eax, (% edx) movl % ebx, (% ecx) popl % ebx popl % ebp ret

• Compile

As swap. s-o swap. o

• Link

Ld-lc-I/lib/ld-linux.so.2 swap. o-o swap

• Run

./Swap