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:67:5: 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
     ^
/home/user/kernrk/kernrk.c:72:1: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
 static struct kretprobe my_kretprobe = {
 ^
/home/user/kernrk/kernrk.c:80:19: error: invalid storage class for function ‘my_init’
 static int __init my_init(void) {
                   ^
/home/user/kernrk/kernrk.c:90:20: error: invalid storage class for function ‘my_exit’
 static void __exit my_exit(void) {
                    ^
In file included from /home/user/kernrk/kernrk.c:1:0:
include/linux/module.h:128:42: error: invalid storage class for function ‘__inittest’
  static inline initcall_t __maybe_unused __inittest(void)  \
                                          ^
/home/user/kernrk/kernrk.c:95:1: note: in expansion of macro ‘module_init’
 module_init(my_init);
 ^
/home/user/kernrk/kernrk.c:95:1: warning: ‘alias’ attribute ignored [-Wattributes]
In file included from /home/user/kernrk/kernrk.c:1:0:
include/linux/module.h:134:42: error: invalid storage class for function ‘__exittest’
  static inline exitcall_t __maybe_unused __exittest(void)  \
                                          ^
/home/user/kernrk/kernrk.c:96:1: note: in expansion of macro ‘module_exit’
 module_exit(my_exit);
 ^
include/linux/module.h:134:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
  static inline exitcall_t __maybe_unused __exittest(void)  \
  ^
/home/user/kernrk/kernrk.c:96:1: note: in expansion of macro ‘module_exit’
 module_exit(my_exit);
 ^
/home/user/kernrk/kernrk.c:96:1: warning: ‘alias’ attribute ignored [-Wattributes]
/home/user/kernrk/kernrk.c:96:1: error: expected declaration or statement at end of input
/home/user/kernrk/kernrk.c: At top level:
/home/user/kernrk/kernrk.c:34:12: warning: ‘ret_handler’ defined but not used [-Wunused-function]
 static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs) {
            ^
cc1: some warnings being treated as errors
make[1]: *** [/home/user/kernrk/kernrk.o] Error 1
make: *** [_module_/home/user/kernrk] Error 2