如何在ARM64中实现系统调用? [英] How to implement system call in ARM64?

问题描述

我正在使用 arm64 汇编代码，我想使用 svc 指令实现系统调用.我在网上找不到任何可用的 arm64 系统调用实现.另外，我找不到 arm64 的系统调用列表.还解释了实现.

I am working with arm64 assembly coding and I want to implement system calls using svc instruction . I can't find any working arm64 system call implementation online.Also, I can't find the system call list for arm64. Also explain the implementation .

推荐答案

可以将x0中的六个参数传递给x5，返回值保存在x0.

You can pass six arguments in x0 to x5, return value is saved in x0.

为了给出汇编代码片段，这是来自 Android Bionic 的 libc 实现.write 的三个参数已经在 x0-x2 中.系统调用号在 x8 中传递.

To give an assembler snippet, this is write syscall from Android Bionic's libc implementation. write's three arguments would already be in x0-x2. Syscall number is passed in x8.

/* Generated by gensyscalls.py. Do not edit. */

#include <private/bionic_asm.h>

    .hidden __set_errno

ENTRY(write)
    mov     x8, __NR_write
    svc     #0

    cmn     x0, #(MAX_ERRNO + 1)
    cneg    x0, x0, hi
    b.hi    __set_errno

    ret
END(write)

提供 AArch64 ABI 看看.

新一代架构都使用来自的数字包括/uapi/asm-generic/unistd.h.

Newer generation of architectures all use numbers from include/uapi/asm-generic/unistd.h.

你也可以查看arch/arm64/包括/asm/syscall.h 用于参数和返回值处理.

You can also check arch/arm64/include/asm/syscall.h for argument and return value handling.

如果您手头有 as 和 ld，您可以创建一个简单的可执行文件，只需使用退出值退出即可.

If you have as and ld in hand, you can create a simple executable just quitting with an exit value.

这里 42 是我们的返回值，93 是 exit 系统调用.

Here 42 is our return value and 93 is exit system call.

$cat answer.s
 .global _start
 _start:
 mov x0, #42
 mov x8, #93
 svc #0
$as answer.s -o answer.o
$ld answer.o -o answer
$./answer
$echo $?
42

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