分段错误（核心已转储）在随后的汇编程序中此错误的原因是什么（将大写转换为小写字符串）？

Question

I want to convert a string to a string with all characters in upper case.What causes segmentation fault(core dumped) ? What are reasons for segmentation fault?

OutPut:Enter a Stringsbash: line 1:     9 Segmentation fault      (core dumped) 

Source:

    %macro accept 2
    mov eax,3
    mov ebx,0
    mov ecx,%1
    mov edx,%2
    int 0x80
    %endmacro

    %macro display 2
    mov eax,4
    mov ebx,1
    mov ecx,%1
    mov edx,%2
    int 0x80
    %endmacro

    section .data
    str1 db "Enter a String";
    len1 equ $-str1
    cnt db 0

    section .bss
    str2 resb 20
    len2 resb 1
    c resb 1


    section .text
    global _start
    _start:
    display str1,len1
    accept str2,2;
    dec al;
    mov [cnt],al
    mov si,[str2]


   up:

    mov ch,[si]
    mov bl,ch

    inc si
    cmp bl,61
    jna up
    cmp bl,73
    ja up
    mov al,20
    sub bl,20
    mov [si],bl;

    mov eax,0
    mov ebx,0;
    int 0x80

Answer 1

Possible reasons are:

1. You don't terminate the loop, you need to use cnt to count characters, then jump out of the loop when cnt is 0.
2. You use si instead of esi, in 32bit mode esi should be used for addressing memory.
3. Instead of mov si,[str2] you should use mov esi,str2 , so that esi stores address of your string, not string bytes.
4. exit syscall has code 1, not 0 (in the end).

Also you probably meant hexadecimal 0x61 (code for letter a), not decimal 61. Same with 73 and 20.