在 AT&T IA-32 Linux 汇编器 (gas) 上分割字符串

发布于 2024-07-11 03:21:42 字数 356 浏览 10 评论 0原文

.section .data

astring: .asciz "11010101"
format: .asciz "%d\n"

.section .text
.globl _start

_start:

xorl %ecx, %ecx

movb astring(%ecx,1), %al
movzbl %al, %eax

pushl %eax
pushl $format
call printf
addl $8, %esp


movl $1, %eax
movl $0, %ebx
int $0x80

假设我想破坏 .asciz 字符串 1101011 并得到它的第一个。我该怎么办？上面的代码不起作用，它打印 49 之类的。

原文

.section .data

astring: .asciz "11010101"
format: .asciz "%d\n"

.section .text
.globl _start

_start:

xorl %ecx, %ecx

movb astring(%ecx,1), %al
movzbl %al, %eax

pushl %eax
pushl $format
call printf
addl $8, %esp


movl $1, %eax
movl $0, %ebx
int $0x80

Suppose I wanna break the .asciz string 1101011 and get it's first one. How do I go about it? The code above ain't working, it prints 49 or something.

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傾旎 2024-07-18 03:21:42

将 printf 从 % 更改为转换说明符d 到 %c 以打印字符而不是其 ascii 值。

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此岸叶落 2024-07-18 03:21:42

4年后。
我正在学习使用 GNU 汇编器进行 asm 编程。
我这样做是为了练习：

.section .rodata
.LC0:
.string "This is the number: %d \n"
.data
.type str, @object
str:
.long .LC0

.section .text
.globl main
.type main, @function
.extern printf
main:
push %ebp
movl %esp, %ebp
andl $-16, %esp
subl $12, %esp
movl $2600, 4(%esp)
movl str, %edx
# Simple printf
movl %edx, %eax
movl %eax, (%esp)
call printf

# putchar
# for loop
movl $0, -4(%ebp)
jmp .check_for
.for_loop:
movl -4(%ebp), %eax
movl str, %edx
leal (%edx, %eax), %eax
movzbl (%eax), %eax
movsbl %al, %eax
movl %eax, (%esp)
call putchar
addl $1, -4(%ebp)
.check_for:
cmp $0x00, (%esp)
jnz .for_loop
leave
ret

4 years later.
I'm learning to programming in asm with GNU Assembler.
I did it as a practice:

.section .rodata
.LC0:
.string "This is the number: %d \n"
.data
.type str, @object
str:
.long .LC0

.section .text
.globl main
.type main, @function
.extern printf
main:
push %ebp
movl %esp, %ebp
andl $-16, %esp
subl $12, %esp
movl $2600, 4(%esp)
movl str, %edx
# Simple printf
movl %edx, %eax
movl %eax, (%esp)
call printf

# putchar
# for loop
movl $0, -4(%ebp)
jmp .check_for
.for_loop:
movl -4(%ebp), %eax
movl str, %edx
leal (%edx, %eax), %eax
movzbl (%eax), %eax
movsbl %al, %eax
movl %eax, (%esp)
call putchar
addl $1, -4(%ebp)
.check_for:
cmp $0x00, (%esp)
jnz .for_loop
leave
ret

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