使用变量进行装配

Question

我试图让文本屏幕打印'h',它存储在一个变量中.我正在使用NASM.x86保护模式,一种从头开始的内核.

DisplayMessage:
        ;mov byte[Color], 0xF
        ;mov CFC, EAX;
        ;mov byte[Color], 104
        ;push 104
        ;mov byte[esi], Msg
        ;lodsb
        mov ebx, Msg
        add ebx, 4
        mov [Msg], eax
        mov byte[0xB8000], Msg
        ;mov byte[eax], Color
        ;pop byte[0xB8000]
        ;mov byte[0xB8000], byte Color
        ;mov byte[0xB8000], 0xB500000;
        ;Now return
        ret
EndCode:
Msg: db 104

它显示的字母永远不对.什么是正确的方法来做到这一点？

Answer 1

    mov ebx, Msg ; this loads ebx with the address of Msg, OK
    add ebx, 4 ; this increments the address by 4, OK, but why?
    mov [Msg], eax ; this stores eax into the first 4 bytes of Msg, OK, but why?
    mov byte[0xB8000], Msg ; this writes the least significant byte of the
                           ; address of Msg to the screen, not OK.
                           ; Does not make any sense.

为什么不呢？:

mov al, [Msg]
mov [0xB8000], al

这应该Msg在屏幕的左上角写入('h'具有ASCII码104,正确)的第一个字符,当然,如果您的数据段在其段描述符中具有基址0,并且如果你org是对的.