在Linux的64位程序的命令行 [英] Process command line in Linux 64 bit

问题描述

我在访问来自Linux的64位汇编程序过程中的命令行的问题。要重现此以最小的code，我做它打印的程序名的前5个字符这32位程序：

I have problems accessing the process command line from Linux 64 bit Assembly program. To reproduce this with minimal code, I made this 32-bit program which prints first 5 characters of the program name:

.section .text

.globl _start
_start:
 movl  %esp, %ebp

 movl $4, %eax        # write
 movl $1, %ebx        # stdout
 movl 4(%ebp), %ecx   # program name address (argv[0])
 movl $5, %edx        # hard-coded length
 int  $0x80

 movl $1, %eax
 movl $0, %ebx
 int  $0x80

此程序工作。当我把它翻译为64位和Linux的64运行，它不打印任何东西：

This program is working. When I translate it to 64 bit and run in Linux 64, it doesn't print anything:

.section .text

.globl _start
_start:
 movq  %rsp, %rbp

 movq $4, %rax
 movq $1, %rbx
 movq 8(%rbp), %rcx       # program name address ?
 movq $5, %rdx
 int  $0x80

 movq $1, %rax
 movq $0, %rbx
 int  $0x80

在哪里是我的错？

Where is my mistake?

推荐答案

您加载正确的地址为％RCX 。

INT 0x80的然后调用32位的系统调用接口。截断的地址为32位，这使得它不正确。 （如果你使用调试器，只是之后的第一个 INT 0x80的，你会看到，它在-14 返回％EAX ，这是 -EFAULT ）

int 0x80 then invokes the 32-bit syscall interface. That truncates the address to 32 bits, which makes it incorrect. (If you use a debugger and set a breakpoint just after the first int 0x80, you will see that it returns with -14 in %eax, which is -EFAULT.)

第二个系统调用，退出，工程确定，因为截断到32位没有做任何伤害在这种情况下。

The second syscall, exit, works OK because the truncation to 32 bits doesn't do any harm in that case.

如果你想传递一个64位的地址，系统调用，你将不得不使用64位系统调用接口：

If you want to pass a 64-bit address to a system call, you will have to use the 64-bit syscall interface:

• 使用系统调用，不是 INT 0x80的;
• 在不同的寄存器用于：看这里;
• 系统调用号不同，以及：请参见这里

• use syscall, not int 0x80;
• different registers are used: see here;
• the system call numbers are different as well: see here.

下面是你的code的工作版本：

Here is a working version of your code:

.section .text

.globl _start
_start:
 movq  %rsp, %rbp

 movq $1, %rax
 movq $1, %rdi
 movq 8(%rbp), %rsi       # program name address ?
 movq $5, %rdx
 syscall

 movq $60, %rax
 movq $0, %rdi
 syscall

这篇关于在Linux的64位程序的命令行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！