system calls

[kernelppc]

Dear all,

I need to add a new system call to the linux kernel.

These are the linux information:
Linux ubuntu-desktop 2.6.32.3 #5 SMP Mon Jan 11 16:56:27 CET 2010 i686 GNU/Linux

I am working on kernel 2.6.32.

These are all the changes I did:

1- adding " .long sys_mycall" to the end of "arch/x86/kernel/syscall_table_32.S"

2- adding

#define __NR_mycall 242 
__SYSCALL(__NR_mycall, sys_mycall) 
#undef __NR_syscalls 
#define __NR_syscalls 243

to the "include/asm-generic/unistd.h"

3- adding
asmlinkage long sys_mycall(char * fname, void * params);
to the end of "/include/linux/syscalls.h"

4-modifying the linux Makefile
core-y += kernel/ mm/ fs/ ipc/ security/ crypto/ block/ mycall/

5- adding mycall folder to kernel source and mycall.c and the corresponding Makefile in it:

#include <linux/kernel.h> 
#include <linux/syscalls.h> 
SYSCALL_DEFINE2(mycall, char __user *, fname,void __user *,params) 
{ 
printk("I am here !!"; 
return 10; 
}

Now after building and installing the new kernel, I want to test the system call with this code:

#include<stdio.h> 
#include <errno.h> 
#include<linux/unistd.h> 
#include <sys/syscall.h> 

#define __NR_mycall 242 

long mycall(char * fname, void * params ) 
{ 
return syscall(__NR_mycall, fname, params); 
} 

int main(void) 
{ 
int tmp=10;	
int er=0;	
char * chp= (char *) &tmp; 
void * vp= (void *) &tmp; 
printf("%d\n", er=mycall(chp,vp)); 
if( er < 0 ) { 
printf( "Error: %d, %s\n", errno, strerror( errno ) ); 
} 
}

Unfortunately, the code prints this:
-1
Error: 3, No such process

And I have no idea what the problem is!

Is there any body who can help me?

Thank you and best regards,
Mojtaba