creating own syscall on 2.6.37.3 and getting error on compilaton...

[rgonzale@darkterminal.net (rgonzale at darkterminal.net)]

I'm trying to implement my own system call on Linux kernel 2.6.37.3 using this guide.

http://enzam.wordpress.com/2011/03/2...nel-ubuntu-os/

Here's the code that I have for kernel/mysystemcalls.c
It just takes an int for an argument and then spits out the PIDs for the process that is running on that CPU.
Code:

#include<linux/linkage.h>
#include<linux/cpumask.h>
asmlinkage long sys_current_pid(int i)  {
	struct rq *rq;
	int num_cpu;
	num_cpu = num_online_cpus();
	if(i <= 0 || i > num_cpu)
		return -1;

	rq = cpu_rq(i);
	if(rq->curr != NULL)
		return rq->curr->pid;
	else
		return -1;
}

But on kernel compilation I get this.
Code:

kernel/mysystemcalls.c: In function 'sys_current_pid':
kernel/mysystemcalls.c:12: error: implicit declaration of function 'cpu_rq'
kernel/mysystemcalls.c:12: warning: assignment makes pointer from integer without a cast
kernel/mysystemcalls.c:13: error: dereferencing pointer to incomplete type
kernel/mysystemcalls.c:14: error: dereferencing pointer to incomplete type
make[1]: *** [kernel/mysystemcalls.o] Error 1
make[1]: *** Waiting for unfinished jobs....

The definition for cpu_rq() is in kernel/sched.c.
Here's the pertinent piece of Makefile in kernel/Makefile
Code:

#
# Makefile for the linux kernel.
#

obj-y     = sched.o fork.o exec_domain.o panic.o printk.o \
				cpu.o exit.o itimer.o time.o softirq.o resource.o \
				sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \
				signal.o sys.o kmod.o workqueue.o pid.o \
				rcupdate.o extable.o params.o posix-timers.o \
				kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
				hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
				notifier.o ksysfs.o pm_qos_params.o sched_clock.o cred.o \
				async.o range.o jump_label.o
				obj-y += mysystemcalls.o

				I would think that since sched.o(the first c file that gets compiled) has the definition for the cpu_rq() then mysystemcalls.c should be able to see that function. What am I missing?

-Tristan