16 位汇编字符串比较不起作用；可能的错误？

Question

我有另一个不包含 getUserInput 功能的程序。它只是比较两个字符串，所以我知道 getCheckKey 工作正常。为什么这根本行不通？当用户输入匹配字符串 correct 时，它不会跳转到 cupcake。您可以尝试：

nasm -f bin -o cmp-input.bin cmp-input.asm

qemu-system-x86_64 cmp-input.bin

ORG 0x7C00
BITS 16


jmp getUserInput                 ; Call function 'getUserInput'

incorrect:
        mov si, invalidKey       ; Set text to SI register
        call printText           ; Call print text function

getUserInput:
        mov si, msg              ; Set greeting text to SI register
        call printText           ; Call print text function
        mov di, inputString      ; set up the string to be read in into di

getKeyLoop:
        mov ah, 0x00             ; Set function 'Reading' for interrupt 16h
        int 0x16                 ; Use 16h interrupt to read next char from keyboard

        mov ah, 0x0e             ; Set char types and colors
        cmp al, 0xD              ; when enter button is pressed...
        je getCheckKey           ; compare the string entered

        int 0x10                 ; otherwise use 10h interrupt to display character
        mov [di], al             ; Move AL to memory of DI address
        inc di                   ; DI += 1; increments the address of DI to store the next character
        jmp getKeyLoop           ; Loop | jump to function 'getKeyLoop'

getCheckKey:                       
        mov di, inputString      ; move input string into di
        mov si, password         ; copy password to si for comparison
        CheckKeyLoop:
                mov al, [di]     ; move 1st character or inputString into al
                mov cl, [si]     ; move 1st character of key into cl
                cmp cl, al       ; compare 1st character of both strings
                jne incorrect    ; if they don't match, jump back to getUserInput but print incorrect message first

                cmp al, 0        ; otherwise compare to null terminator
                je correct       ; password match

                inc di           ; otherwise check next char
                inc si           ; check next char
                jmp CheckKeyLoop ; resume the loop

correct:
        mov si, correctkey

printText:                       ; Function 'printText'
        mov ah, 0x0e             ; Set the text print mode
        mov bh, 0x00             ; Set screen and text parameters
        mov bl, 0x07             ; Set screen and text parameters
printChar:
        mov al, [si]             ; Move character from si (dereferenced) to al

        cmp al, 0                ; If AL = 0...
        je endPrinting           ; Call function 'endPrinting'
                                 ; Else...
        int 0x10                 ; Use 10h interrupt
        add si, 1                ; Move +1 to SI register (inc si)
        jmp printChar            ; Loop back up to 'printChar' function.

endPrinting:                     ; Function 'endPrinting'
        ret                      ; Return



password db "cupcake", 0
msg db " Enter the password: ", 0
invalidKey db " <= Incorrect. Try again..", 13, 10, 0
inputString db " ", 0
correctkey db " Congratulations!", 13, 10, 0
times 510 - ($-$$) db 0 
dw 0xAA55