为什么我不能使用int 0x80从指向堆栈存储器的指针进行sys_write? [英] Why can't I sys_write from a pointer to stack memory, using int 0x80?

问题描述

; NASM
push 30 ; '0'

mov rax, 4 ; write
mov rbx, 1 ; stdout
mov rcx, rsp ; ptr to character on stack
mov rdx, 1 ; length of string = 1
int 80h

上面的代码不会将任何内容输出到stdout.当我为section .data中的字符提供ptr时，它会起作用.我在做什么错了?

The code above does not print anything to stdout. It works when i give it a ptr to a character in section .data. What am i doing wrong?

推荐答案

amd64使用与int 0x80不同的方法进行系统调用，尽管该方法可能仍适用于已安装的32位库等.而在会这样做:

amd64 uses a different method for system calls than int 0x80, although that might still work with 32-bit libraries installed, etc. Whereas on x86 one would do:

mov eax, SYSCALL_NUMBER
mov ebx, param1
mov ecx, param2
mov edx, param3
int 0x80

在amd64上的

可以这样做:

on amd64 one would instead do this:

mov rax, SYSCALL_NUMBER_64 ; different from the x86 equivalent, usually
mov rdi, param1
mov rsi, param2
mov rdx, param3
syscall

对于您想做的事情，请考虑以下示例:

For what you want to do, consider the following example:

        bits 64
        global _start

section .text

_start:
        push            0x0a424242
        mov             rdx, 04h
        lea             rsi, [rsp]
        call            write
        call            exit
exit:
        mov             rax, 60     ; exit()
        xor             rdi, rdi    ; errno
        syscall

write:
        mov             rax, 1      ; write()
        mov             rdi, 1      ; stdout
        syscall
        ret

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