Noptrace module example

int (*real_ptrace) (int, int, int, int);
int new_ptrace  (int, int, int, int);
extern void *sys_call_table[];

/* The replacement function */
int new_ptrace(int request, int pid, int addr, int data) {
      return -1;
}

int init_module() {

      /* Save a pointer to the old ptrace function */
      real_ptrace   = sys_call_table[ __NR_ptrace ];

      /* point to our new ptrace function in sys_call_table */
      sys_call_table[ __NR_ptrace ]   =  (void *)new_ptrace;

      printk(KERN_INFO "noptrace module installed\n");
      return 0;
}