大会，你好世界问题 [英] Assembly, hello world question

问题描述

我正在Linux上学习asm(noobuntu 10.04) 我得到以下代码: http://asm.sourceforge.net/intro/hello. html

I'm learning asm on Linux (noobuntu 10.04) I got the following code off of: http://asm.sourceforge.net/intro/hello.html

section .text
global _start ;must be declared for linker (ld)

_start: ;tell linker entry point

mov edx,len ;message length
mov ecx,msg ;message to write
mov ebx,1 ;file descriptor (stdout)
mov eax,4 ;system call number (sys_write)
int 0x80 ;call kernel

mov eax,1 ;system call number (sys_exit)
int 0x80 ;call kernel

section .data

msg db 'Hello, world!',0xa ;our dear string
len equ $ - msg ;length of our dear string

这是一个简单的问候世界.在Linux上运行+直接(显然)调用内核. 谁能解释一下这里到底发生了什么?我认为它会读取eax&中的整数ebx处理器寄存器和ecx，edx数据，它定义了调用内核时的系统调用.如果是这样，在调用int 0x80时，整数的不同组合是否定义了不同的系统调用?

It's a simple hello world. Runs on Linux + calls the kernel directly (apparently). Can anyone please explain what is really going on here? I think it reads the integers in the eax & ebx processor registers & ecx, edx data and that defines the system call when the kernel is called. If so, do different combinations of integers define different system calls when int 0x80 is called?

我对手册页不好，但是已经阅读了我能找到的所有相关手册，任何手册页都告诉我哪些组合定义了哪些系统调用吗?

I'm not good with man pages, but have read every related one I can find, does any man page tell me what combinations define what syscalls?

感谢您的帮助.一行一行的解释将是惊人的... -提前致谢 杰里米

ANY help is appreciated. A line by line explanation would be amazing... -Thanks in advance Jeremy

推荐答案

调用int 0x80时，内核会查看eax寄存器的值以确定要调用的函数(这是"syscall"数字").根据该数字，其余寄存器将被解释为表示特定的事物. sys_write调用要求按以下步骤设置寄存器:

When you call int 0x80, the kernel looks at the value of the eax register to determine the function you want to call (this is the "syscall number"). Depending on that number, the rest of the registers are interpreted to mean specific things. The sys_write call expects the registers to be set up as follows:

• eax包含4
• ebx包含文件描述符
• ecx包含要写入的数据的地址
• edx包含字节数

• eax contains 4
• ebx contains the file descriptor
• ecx contains the address of the data to write
• edx contains the number of bytes

有关更多详细信息，请参见 Linux系统调用.

For further extensive information, see Linux System Calls.

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