Write a procedure that copys a string to another memory location.The procedurereceives two parameters:the start address of the source string and the start addressof the destination memory location.Write a test program that calls your procedureand shows the copied string in the destination memory location after the call. Requirement:Your code should be assembled and executed successfully.Submit thefile of your source code.2021
时间: 2024-03-05 18:54:40 浏览: 16
Sure, here is a possible implementation of the procedure in x86 assembly language:
```
section .text
global copy_string
copy_string:
push ebp
mov ebp, esp
push ebx
push ecx
push edx
mov ebx, [ebp+8] ; source address
mov ecx, [ebp+12] ; destination address
mov al, [ebx] ; load first byte from source
mov [ecx], al ; store first byte to destination
inc ebx
inc ecx
.copy_loop:
mov al, [ebx] ; load next byte from source
mov [ecx], al ; store next byte to destination
inc ebx
inc ecx
cmp byte [ebx-1], 0 ; check if end of string
jne .copy_loop
pop edx
pop ecx
pop ebx
mov esp, ebp
pop ebp
ret
```
This procedure uses the standard x86 calling convention, where the first parameter (source address) is passed in the `eax` register and the second parameter (destination address) is passed in the `edx` register. The procedure copies the string byte by byte from the source to the destination, until it reaches the end of the string (indicated by a null byte).
Here is an example program that calls the `copy_string` procedure and displays the copied string:
```
section .data
source db "Hello, world!", 0
destination times 13 db 0 ; reserve space for copied string
section .text
global _start
_start:
; call copy_string procedure with source and destination addresses
push dword destination
push dword source
call copy_string
add esp, 8
; display copied string
mov eax, 4 ; write system call
mov ebx, 1 ; standard output file descriptor
mov ecx, destination ; address of copied string
mov edx, 13 ; length of string
int 0x80 ; invoke system call
; exit program
mov eax, 1 ; exit system call
xor ebx, ebx ; exit status 0
int 0x80 ; invoke system call
```
This program defines a string `source` and a destination buffer `destination`, and calls the `copy_string` procedure with their addresses. Then it displays the copied string using the `write` system call, and exits with a status of 0.
To assemble and link this program, you can use the following commands (assuming you save the code in a file called `copy.asm`):
```
nasm -f elf32 -o copy.o copy.asm
ld -m elf_i386 -o copy copy.o
```
This will produce an executable file called `copy`, which you can run by typing `./copy` in the terminal.