问linux上的x86程序集，movsd分段故障

EN

_start:
    jmp short call

shell:
    pop esi
    movsd ;move 4 byte from esi to edi (/bin)
    mov edx,edi ;edx contains /bin
    xor edi,edi 
    movsw ;move 2 bytes (/s) 
    xor ebx,ebx
    mov ebx,edi ;ebx contains /s
    xor eax,eax
    xor edi,edi
    movsb
    mov eax,edi ;eax contiene h
    mov esi,edx ;esi contains /bin

    xor ecx,ecx
    push ecx
    mov edx,esp ;edx dword NULL

    push ecx ;NULL
    push ecx ;NULL
    add esp,3 ;0
    push eax
    add esp,3 ;h
    push ebx
    add esp,2 ;/s
    push esi ;/bin  
    mov ecx,esp ;/bin/sh0,NULL

    xor edi,edi
    push edi
    add esp,3 ;0
    push eax
    add esp,3
    push ebx
    add esp,2
    push esi
    mov ebx,esp ;/bin/bash0

    xor eax,eax
    mov al,0xb
    int 0x80

call:
    call shell
    path db "/bin/sh"