Assembly NASM子程序和分段错误
我一直在试验NASM和汇编语言,因此,我对子程序如何在这种语言中工作有一个基本的想法。然而,我的问题是,如何在同一过程中捆绑不同的标签。例如,我在S.O.中找到的以下代码:Assembly NASM子程序和分段错误,assembly,x86,segmentation-fault,nasm,subroutine,Assembly,X86,Segmentation Fault,Nasm,Subroutine,我一直在试验NASM和汇编语言,因此,我对子程序如何在这种语言中工作有一个基本的想法。然而,我的问题是,如何在同一过程中捆绑不同的标签。例如,我在S.O.中找到的以下代码: ;----------------------------------------------- ;SECTION .DATA ;Instantiated variables/Constants ;----------------------------------------------- section .data r
;-----------------------------------------------
;SECTION .DATA
;Instantiated variables/Constants
;-----------------------------------------------
section .data
result: db "The smallest number is: " , 0x0a
result_len: equ $-result
nl: db " ", 0x0a
nl_len equ $-nl
matrix: dw 25, 24, 23, 22, 21
dw 20, 19, 18, 17, 16
dw 15, 14, 13, 12, 11
dw 10, 9, 8, 7, 6
dw 5, 4, 3, 2, 1
;-----------------------------------------------
;SECTION .BSS
;Non initialized variables
;-----------------------------------------------
section .bss
;-----------------------------------------------
;SECTION .TEXT
;Code
;-----------------------------------------------
section .text
global _start
_start:
mov edi, 0
mov esi, 0
mov ecx, 12
outerLoop:
cmp edi, 50 ;each element is 2 bytes (2 ascii characters)
ja endloop ;we need 50 because it's 5 elements per row
mov esi, 0 ;and 5 rows
innerLoop:
cmp esi, 5 ;Compare esi(inner loop index) to 5
jae innerEnd ;jump if it reached the end of the row
mov ax, [matrix + edi + esi*2]
cmp ax, cx
jg biggerThan
mov cx, ax
biggerThan:
inc esi
jmp innerLoop
innerEnd:
add edi, 10 ;row has been complete, go to next
jmp outerLoop
endloop:
push ecx
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, result_len
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, esp
add [ecx], DWORD 30h
mov edx, 2
int 0x80
; display new line
mov eax, 4
mov ebx, 1
mov ecx, nl
mov edx, nl_len
int 0x80
exit:
mov eax, 1 ;eax contains 1 so quit
mov ebx, 0
int 0x80
是否可以将innerLoop、outerLoop、biggerThan、innerEnd等捆绑在一个过程中,并像这样调用该过程:
;-----------------------------------------------
;SECTION .DATA
;Instantiated variables/Constants
;-----------------------------------------------
section .data
result: db "The smallest number is: " , 0x0a
result_len: equ $-result
nl: db " ", 0x0a
nl_len equ $-nl
matrix: dw 25, 24, 23, 22, 21
dw 20, 19, 18, 17, 16
dw 15, 14, 13, 12, 11
dw 10, 9, 8, 7, 6
dw 5, 4, 3, 2, 1
;-----------------------------------------------
;SECTION .BSS
;Non initialized variables
;-----------------------------------------------
section .bss
;-----------------------------------------------
;SECTION .TEXT
;Code
;-----------------------------------------------
section .text
global _start
_start:
mov edi, 0
mov esi, 0
mov ecx, 12
call findSmallestNumber
findSmallestNumber:
outerLoop:
cmp edi, 50 ;each element is 2 bytes (2 ascii characters)
ja endloop ;we need 50 because it's 5 elements per row
mov esi, 0 ;and 5 rows
innerLoop:
cmp esi, 5 ;Compare esi(inner loop index) to 5
jae innerEnd ;jump if it reached the end of the row
mov ax, [matrix + edi + esi*2]
cmp ax, cx
jg biggerThan
mov cx, ax
biggerThan:
inc esi
jmp innerLoop
innerEnd:
add edi, 10 ;row has been complete, go to next
jmp outerLoop
endloop:
push ecx
ret
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, result_len
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, esp
add [ecx], DWORD 30h
mov edx, 2
int 0x80
; display new line
mov eax, 4
mov ebx, 1
mov ecx, nl
mov edx, nl_len
int 0x80
exit:
mov eax, 1 ;eax contains 1 so quit
mov ebx, 0
int 0x80
这样做会在Linux中导致一致的分段错误,所以我尝试这样做的方式肯定有问题。
任何帮助都将不胜感激 至少存在两个问题:
push ecx
不应该是子例程的一部分,因为它已经是主程序中的代码。它通过write
系统调用设置打印缓冲区。其位置由mov ecx,esp
行使用。请注意,ret
从堆栈中弹出一个地址,并返回该地址。因此,在这种情况下,它将弹出您的ecx
值,并尝试将其用作导致故障的返回地址调用
指令后继续执行代码。在您的情况下,这意味着它将再次进入findsmalestnumber
子例程(因为它直接在调用之后),但这次堆栈上没有返回地址。因此,即使点1已修复,ret
仍会出现故障。解决方法是将子例程移出直接执行路径。也就是说,在发出exit调用之后,将整个子例程放在代码的末尾