我知道这听起来很愚蠢,但我对汇编语言很陌生,所以请耐心等待!jmp在程序集中的'变量'标签(AT&T语法)
我有以下汇编代码,这是我试图做的简化版本。
1 # print.s
2 # C callable: char* print()
3
4 .data
5 output:
6 .asciz "abcd"
7
8 .text
9 .globl _printbin
10
11 _printbin:
12 pushl %ebp # set up stack frame
13 movl %esp, %ebp # save esp in ebp
14
15 movl $output, %eax # put the address of "abcd" in eax
16
17 xor %ebx, %ebx # clear ebx
18 movl $5, %ebx # put 5 in ebx (input for func)
19 movl $0, %edx # put 1 in edx (index)
20 jmp _func # call func
21
22 back1:
23 xor %ebx, %ebx # clear ebx
24 movl $7, %ebx # put 7 in ebx (input for func)
25 movl $2, %edx # put 2 in edx (index)
26 jmp _func # call func
27
28 end:
29 movl %ebp, %esp # restore esp
30 popl %ebp # restore ebp
31 ret
32
33 # take the input, add 1 to it,
34 # then print it to eax at the specified index
35 _func: # num input in %ebx, index is in %edx , print to: %eax
36 addb $0x1, %ebx # print the result to eax
37 movb %ebx, (%eax, %edx)
38 jmp back1 # how to decide wether to jump to back1 or to end?
39
40 .end
41
问题是,我该如何跳转到某种“变量”标签。 (所以有时候我想跳到这个标签上,但有些时候是另一个标签......这种想法)
你为什么在第36,37行使用'addb'和'movb';如果我没有弄错,这应该是'addl'和'movl'; 'b'后缀用于'bytes' – Hawken 2012-04-22 14:33:22