适用于Linux的Windows子系统上的Ubuntu上使用INT 0x80的程序集编译的可执行文件不会产生输出 [英] Assembly compiled executable using INT 0x80 on Ubuntu on Windows Subsystem for Linux doesn't produce output

问题描述

我一直在看汇编教程，我正在尝试运行一个hello world程序.我正在Windows的Ubuntu上使用Bash.

I've been looking at a tutorial for assembly, and I'm trying to get a hello world program to run. I am using Bash on Ubuntu on Windows.

这里是程序集:

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

_start:             ;tells 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  ;string to be printed
    len equ $ - msg     ;length of the string

我正在使用以下命令创建可执行文件:

I am using these commands to create the executable:

nasm -f elf64 hello.asm -o hello.o
ld -o hello hello.o -m elf_x86_64

然后我使用以下命令运行它:

And I run it using:

./hello

然后该程序似乎没有分段错误或错误运行，但没有任何输出.

The program then seems to run without a segmentation fault or error, but it produces no output.

我不知道为什么代码不会产生输出，但是我想知道Windows上在Ubuntu上使用Bash是否与此有关?为什么它不产生输出，我该如何解决?

I can't figure out why the code won't produce an output, but I wonder if using Bash on Ubuntu on Windows has anything to do with it? Why doesn't it produce output and how can I fix it?

推荐答案

问题出在Windows的Ubuntu(Linux的Windows子系统)上.它仅支持64位的 syscall 接口和 不 32位x86 int 0x80 系统调用机制.

The issue is with Ubuntu for Windows (Windows Subsystem for Linux). It only supports the 64-bit syscall interface and not the 32-bit x86 int 0x80 system call mechanism.

除了无法在64位二进制文​​件中使用 int 0x80 (32位兼容性)之外，Windows上的Ubuntu(WSL)

Besides not being able to use int 0x80 (32-bit compatibility) in 64-bit binaries, Ubuntu on Windows (WSL) doesn't support running 32-bit executables either.

您需要从使用 int 0x80 转换为 syscall .不难 syscall 使用一组不同的寄存器，并且系统调用号与其32位对应号不同. Ryan Chapman的博客在 syscall 界面上具有信息，系统调用，以及它们的参数. Sys_write 和 Sys_exit 的定义方式如下:

You need to convert from using int 0x80 to syscall. It's not difficult. A different set of registers are used for a syscall and the system call numbers are different from their 32-bit counterparts. Ryan Chapman's blog has information on the syscall interface, the system calls, and their parameters. Sys_write and Sys_exit are defined this way:

%rax  System call  %rdi               %rsi              %rdx          %r10 %r8 %r9
----------------------------------------------------------------------------------
0     sys_read     unsigned int fd    char *buf         size_t count          
1     sys_write    unsigned int fd    const char *buf   size_t count
60    sys_exit     int error_code     

使用 syscall 还可复制 RCX 和 R11 寄存器.它们被认为是易变的.不要依赖 syscall 之后的相同值.

Using syscall also clobbers RCX and the R11 registers. They are considered volatile. Don't rely on them being the same value after the syscall.

您的代码可以修改为:

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

_start:             ;tells linker entry point
    mov edx,len     ;message length
    mov rsi,msg     ;message to write
    mov edi,1       ;file descriptor (stdout)
    mov eax,edi     ;system call number (sys_write)
    syscall         ;call kernel

    xor edi, edi    ;Return value = 0
    mov eax,60      ;system call number (sys_exit)
    syscall         ;call kernel

section .data
    msg db 'Hello, world!', 0xa  ;string to be printed
    len equ $ - msg     ;length of the string

注意:如果指令的目标寄存器是32位(如 EAX ， EBX ， EDI ， ESI 等)，处理器零将结果扩展到高32位的64位寄存器. mov edi，1 与 mov rdi，1 具有相同的效果.

Note: in 64-bit code if the destination register of an instruction is 32-bit (like EAX, EBX, EDI, ESI etc) the processor zero extends the result into the upper 32-bits of the 64-bit register. mov edi,1 has the same effect as mov rdi,1.

这个答案不是编写64位代码的入门，仅关于使用 syscall 接口.如果您对编写调用 C 库并符合64位System V ABI的代码的细微差别感兴趣，可以使用一些合理的教程来入门，例如

This answer isn't a primer on writing 64-bit code, only about using the syscall interface. If you are interested in the nuances of writing code that calls the C library, and conforms to the 64-bit System V ABI there are reasonable tutorials to get you started like Ray Toal's NASM tutorial. He discusses stack alignment, the red zone, register usage, and a basic overview of the 64-bit System V calling convention.

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