Hi all,
I tried to write my own system call
and call it from the user land using _syscall0 macro
The following code works but
I m not sure whether the following code that i have written is the legal and
safer way of doing it.
I saw somewhere in the kernel source code
that the size of the sys_call_table is 256.
In unistd.h for i386 there are only 221 calls
so i decided to insert my own call at 222.
some one please tell me whether it is safe or not to do that.
If not is there a decent way of writing my own system call.
I m using RedHat 7.1 and the kernel version is 2.4.2-2 on an i686
/*The code goes here*/
#include <linux/kernel.h>
#include <linux/module.h>
extern int printk(const char *fmt, ...);
extern void *sys_call_table[];
extern int nr_running;
/*extern int nr_threads;*/
/*extern int last_pid;*/
asmlinkage int our_syscall()
{
printk("---------------------\n");
printk("nr_running : %d\n",nr_running);
printk("---------------------\n");
return 0;
}
int init_module()
{
sys_call_table[222] = our_syscall;
return 0;
}
void cleanup_module()
{
sys_call_table[222] = 0;
}
thanks and regards,
mohan.
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