I am writing kernel module(C in Linux) and I want to change the permission of the other files in it. any solution? since I am in kernel I can't use chmod syscall and ... thanks for your help

This is my Makefile:

> obj-m += ca.o
> 
>     all:
>       make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
>     
>     clean:
>       make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

And this is my Code:

> #include <linux/string.h>
> #include <linux/mm.h>
> /* Snip, tons of includes (all of them :))*/
> #include <linux/delay.h> .... int procfile_write(struct file *file,
> const char *buffer, unsigned long
> count,
>   	   void *data) { ... 	sys_chmod(path, per); ... } ...

When Making it gives a warning:

WARNING: "sys_chmod" [file] undefiened

and when loading the module with "sudo insmod" it gives this error:

Unknown sybol in module

it seems that this error happens especialy in kernel modules. any idea? again thanks!