make: Entering directory `/usr/src/linux-headers-4.4.0-142-generic'
  CC [M]  /home/user/kernrk/kernrk.o
/home/user/kernrk/kernrk.c: In function ‘entry_handler’:
/home/user/kernrk/kernrk.c:22:21: warning: unused variable ‘data’ [-Wunused-variable]
     struct my_data *data = (struct my_data *)ri->data;
                     ^
/home/user/kernrk/kernrk.c: In function ‘ret_handler’:
/home/user/kernrk/kernrk.c:69:5: error: implicit declaration of function ‘regs_set_return_value’ [-Werror=implicit-function-declaration]
     regs_set_return_value(regs, new_nread); // update return value to new_nread