无法在x86 ubuntu linux上添加自定义系统调用 [英] Unable to add a custom system call on x86 ubuntu linux
问题描述
我对此并不陌生，只是了解内核，因此我试图向内核4.20.4添加自定义调用.这是我所做的步骤.
I am new to this and just learning about the kernel, and I am trying to add a custom call to kernel 4.20.4. This is the steps that I did.
- 首先，我创建包含代码的文件(
kernel/printmsg.c).
#include <linux/kernel.h>
#include <linux/syscalls.h>
SYSCALL_DEFINE1(printmsg, int, i)
{
printk(KERN_DEBUG, "TESTING %d", i);
return 1;
}
- 接下来，我将此文件添加到
kernel/Makefile
obj-y = fork.o exec_domain.o panic.o \
// A few more lines
obj-y += printmsg.o // I added this line
- 最后，通过添加以下行，将系统调用添加到
arch/x86/entry/syscalls/syscall_64.tbl上的syscall表中(我正在64位Ubuntu上构建它):
- Finally, I add the system call to the syscall table on
arch/x86/entry/syscalls/syscall_64.tbl(I'm building this on a 64-bit Ubuntu) by appending this line:
548 64 printmsg sys_printmsg
现在，我继续运行make.但是，它有此错误:
Now, I proceed to run make. However, it has this error:
arch/x86/entry/syscall_64.o:(.rodata+0x1120): undefined reference to `sys_printmsg'
Makefile:1034: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1
为此我已经挠了很长时间，但我似乎不知道出了什么问题.
I've been scratching my head for a long time for this but I can't seem to realised what went wrong.
希望任何设法找到问题的人都能帮助穷人.预先感谢！
Hope that anyone that managed to find a problem can help out a poor soul. Thanks in advance!
推荐答案
好吧，经过数小时的反复试验，我终于找到了问题所在.从Linux内核v4.17开始，x86_64系统调用可能以"__x64_sys"开头.
Okay, after hours of trial and error, I have finally found the problem. From linux kernel v4.17 onwards, x86_64 system calls may begin with "__x64_sys".
因此，我没有使用548 64 printmsg sys_printmsg，而是将其更改为548 64 printmsg __x64_sys_printmsg.然后一切正常.
So, instead of using 548 64 printmsg sys_printmsg, I changed it to 548 64 printmsg __x64_sys_printmsg. Then everything works.
希望这对可能遇到此问题的所有人有所帮助.
Hoped this helped everyone that might have this problem.
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