Question

因此，我想创建一个程序，允许用户输入4x5矩阵。我声明了“指向特定行的指针”和“指向这些指针的指针”，以便能够使用一个指针访问每个字符串。我创建了字符串是因为我想检查这些字符串中的符号（用户只能输入数字和+或-作为第一个符号）。因此，当我检查第一个符号（该符号应为+或-）并且用户未输入+或-时，我遇到问题，我看到分段错误（核心已转储）。我使用Ubuntu。（英语不是我的母语，如果我犯了一个错误，那就不用担心））。

; Task: write a program that allows to enter 2-D array 4x5. Show only 2 first columns.
;   # # # # #  
;   # # # # #
;   # # # # #
;   # # # # # 


section .bss ; The section intended for uninitilizated data
    string_00 resb 7
    string_01 resb 7
    string_02 resb 7
    string_03 resb 7
    string_04 resb 7

    string_10 resb 7
    string_11 resb 7
    string_12 resb 7
    string_13 resb 7
    string_14 resb 7

    string_20 resb 7
    string_21 resb 7
    string_22 resb 7
    string_23 resb 7
    string_24 resb 7

    string_30 resb 7
    string_31 resb 7
    string_32 resb 7
    string_33 resb 7
    string_34 resb 7

section .data ; The section designed for using initilizated data
    GreenColor db 0x1b, '[32m' ; The string that can change text color to green
    lenGreenColor equ $ - GreenColor ; The lenth of this string

    RedColor db 0x1b, '[31m' ; The string that can change text color to red (used if user will enter incorrect data)
    lenRedColor equ $ - RedColor ; The lenth of this string

    Task db 'This program allows you to enter matrix 4x5 and show only 2 first colums.', 0xa ; Just a string that shows my task
    lenTask equ $ - Task ; The lenth of this string

    Warning db 'Enter 16-bit numbers (from -32767 to +32768) and enter the sign of number, please.', 0xa ; Warning, I chose 16-bit number because the bigger
    lenWarning equ $ - Warning ; The lenth of this string                                                ; numbers will be processed in the same way, but long
                                                                                                         ; numbers are not necessary    

    ErrorSign db 'You should use the sign of the number ( + or - )!', 0xa ; An error message to user if he did not use the number sign
    lenErrorSing equ $ - ErrorSign ; THe lenth of this message

    pointer_0 dd string_00, string_01, string_02, string_03, string_04
    pointer_1 dd string_10, string_11, string_12, string_13, string_14
    pointer_2 dd string_20, string_21, string_22, string_23, string_24
    pointer_3 dd string_30, string_31, string_32, string_33, string_34

    pointer dd pointer_0, pointer_1, pointer_2, pointer_3

    external_counter db 0
    internal_counter db 0

section .text
    global _start
_start:
    mov edx, lenGreenColor
    mov ecx, GreenColor
    call _print

    mov edx, lenTask
    mov ecx, Task
    call _print

    mov edx, lenWarning
    mov ecx, Warning
    call _print

    call _check



    mov ebx, 0
    mov eax, 1
    int 0x80

_print:
    mov ebx, 1
    mov eax, 4
    int 0x80
    ret

_enter:
    mov edx, 7
    mov ebx, 0
    mov eax, 3
    int 0x80
    ret

_check:
    external_loop:
        mov eax, [pointer]
        mov ebx, [external_counter]
        mov esi, [eax + ebx * 4]

            internal_loop:
                mov ebx, [internal_counter]

                add ebx, ebx
                add ebx, ebx
                add ebx, ebx

                add esi, ebx
                mov ecx, esi
                call _enter

                cmp [esi], byte 43
                je norm_sign
                cmp [esi], byte 45
                je norm_sign


                xor esi, esi
                xor eax, eax
                xor ebx, ebx
                xor ecx, ecx
                xor edx, edx


                jmp _check
                    norm_sign:
                        ret

Answer 1

您有mov ebx, [external_counter]，还有external_counter db 0。由于ebx是32位寄存器，因此将从external_counter中读取4个字节。问题是external_counter只有1个字节长。这意味着您将把3个垃圾字节拖入ebx中，这将使您在执行mov esi, [eax + ebx * 4]时超出范围。改为使用external_counter dd 0。（而且您似乎也用internal_counter犯了同样的错误。）

NASM分段故障（核心已转储）

1 个答案: