NASM Linux程序集打印整数

Question

我试图在linux上的nasm程序集中打印单个数字整数.我目前编写的内容很好,但没有任何内容写入屏幕.任何人都可以向我解释我在这里做错了什么吗？

section .text
    global _start

_start:
    mov ecx, 1          ; stores 1 in rcx
    add edx, ecx        ; stores ecx in edx
    add edx, 30h        ; gets the ascii value in edx
    mov ecx, edx        ; ascii value is now in ecx
    jmp write           ; jumps to write


write:
    mov eax, ecx        ; moves ecx to eax for writing
    mov eax, 4          ; sys call for write
    mov ebx, 1          ; stdout

    int 80h             ; call kernel
    mov eax,1           ; system exit
    mov ebx,0           ; exit 0
    int 80h             ; call the kernel again 

Answer 1

这是添加,而不是存储:

add edx, ecx        ; stores ecx in edx

这将ecx复制到eax,然后用4覆盖它:

mov eax, ecx        ; moves ecx to eax for writing
mov eax, 4          ; sys call for write

编辑:

对于'写'系统调用:

eax = 4
ebx = file descriptor (1 = screen)
ecx = address of string
edx = length of string

Answer 2

在查看了其他两个答案之后，这就是我最终想到的。

sys_exit        equ     1
sys_write       equ     4
stdout          equ     1

section .bss
    outputBuffer    resb    4       

section .text
    global _start

_start:
    mov  ecx, 1                 ; Number 1
    add  ecx, 0x30              ; Add 30 hex for ascii
    mov  [outputBuffer], ecx    ; Save number in buffer
    mov  ecx, outputBuffer      ; Store address of outputBuffer in ecx

    mov  eax, sys_write         ; sys_write
    mov  ebx, stdout            ; to STDOUT
    mov  edx, 1                 ; length = one byte
    int  0x80                   ; Call the kernel

    mov eax, sys_exit           ; system exit
    mov ebx, 0                  ; exit 0
    int 0x80                    ; call the kernel again