如何将两个dword移到一个qword中? [英] How can I move two dword into one qword?

问题描述

我在此处找到了类似的答案，但仅适用于32位.如何在64位处理器的NASM中做到这一点?

I found similiar anwser here, but it works only for 32bit. How can I do it in NASM in 64bit processor?

推荐答案

您可以使用两个双字连续变量(一个接一个)，分别给它们分配值，然后将两个值都作为一个值四字.我在此在线编译器中测试了下一个代码:

You can use two double-word consecutive variables (one after another), assign them values separatedly, then get both values as one quad-word. I tested next code in this online compiler :

section .data
    dw1  : dd 0   ;◄■■ FIRST DOUBLE-WORD.
    dw2  : dd 0   ;◄■■ SECOND DOUBLE-WORD.

section .text
    global _start
_start:

    mov dword [dw2], 12345678h   ;◄■■ ONE DOUBLE-WORD.
    mov dword [dw1], 90ABCDEFh   ;◄■■ ANOTHER DOUBLE-WORD.
    mov rax, [dw1]               ;◄■■ GET ONE QUAD-WORD (1234567890ABCDEFh).

请注意第二双字(dw2)如何获得更高的值以及第一双字()获取降低值.另请注意，如何从第一个变量中提取四字，但由于rax的大小而到达第二个变量.

Notice how the second double-word (dw2) gets the higher value, and the first double-word (dw1) gets the lower value. Also notice how the quad-word is extracted from the first variable but it reaches the second variable because of the size of rax.

先前的代码不显示任何内容来了解​​RAX中发生的事情，所以这是我的原始代码:它将RAX中的值移动到字符串中，然后显示字符串(垃圾字符):

Previous code doesn't display anything to know what is going on in RAX, so this is my original code: it moves the value from RAX into a string, then displays the string (garbage chars) :

section .data
    str1 : db  '12345678',10
    len  : equ $-str1
    dw1  : dd 0
    dw2  : dd 0

section .text
    global _start
_start:
    mov eax, 4
    mov ebx, 1
    mov ecx, str1
    mov edx, len
    int 80h             ;◄■■ DISPLAY STRING = "12345678".

    mov rax, 01234567890ABCDEFh ;◄■■ MOVE ONE QUAD-WORD DIRECTLY.
    mov [str1], rax    
    mov eax, 4
    mov ebx, 1
    mov ecx, str1
    mov edx, len
    int 80h             ;◄■■ DISPLAY STRING = "�ͫ�xV4"

    mov dword [dw2], 12345678h ;◄■■ MOVE ONE DOUBLE-WORD.
    mov dword [dw1], 90ABCDEFh ;◄■■ MOVE ANOTHER DOUBLE-WORD.
    mov rax, [dw1]
    mov [str1], rax    
    mov eax, 4
    mov ebx, 1
    mov ecx, str1
    mov edx, len
    int 80h            ;◄■■ DISPLAY STRING = "�ͫ�xV4" AGAIN!!!

    mov eax,1
    mov ebx,0
    int 80h

上一个是"int 80h"版本，下一个是"syscall版本"(感谢@MichaelPetch告诉我必须使用的寄存器)，也在同一在线编译器:

EDIT : previous is the "int 80h" version, next is the "syscall version" (thanks @MichaelPetch for telling me what registers I had to use), also tested in the same online compiler :

section .data
    str1 : db  '12345678',10
    len  : equ $-str1
    dw1  : dd 0
    dw2  : dd 0

section .text
    global _start
_start:
    mov rax, 1
    mov rdi, 1
    mov rsi, str1
    mov rdx, len
    syscall             ;◄■■ DISPLAY STRING = "12345678".

    mov rax, 01234567890ABCDEFh ;◄■■ MOVE ONE QUAD-WORD DIRECTLY.
    mov [str1], rax    
    mov rax, 1
    mov rdi, 1
    mov rsi, str1
    mov rdx, len
    syscall             ;◄■■ DISPLAY STRING = "�ͫ�xV4"

    mov dword [dw2], 12345678h ;◄■■ MOVE ONE DOUBLE-WORD.
    mov dword [dw1], 90ABCDEFh ;◄■■ MOVE ANOTHER DOUBLE-WORD.
    mov rax, [dw1]
    mov [str1], rax    
    mov rax, 1
    mov rdi, 1
    mov rsi, str1
    mov rdx, len
    syscall            ;◄■■ DISPLAY STRING = "�ͫ�xV4" AGAIN!!!

    mov rax,60
    mov rdi,0
    syscall

这篇关于如何将两个dword移到一个qword中?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！