Linux kernel develop -- Hello World

hello.c:

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("xudonglee");

static int hello_init(void)
{
  printk(KERN_ALERT "Hello, world!\n");
  return ;
}

static void hello_exit(void)
{
  printk(KERN_ALERT "Goodbye, My Dear World!\n");
}

module_init(hello_init);
module_exit(hello_exit);

Makefile:

obj-m = hello.o
KVERSION = $(shell uname -r)
all:
    make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
    make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

The files:

order in terminal:

make

insmod hello.ko

tail /var/log/messages(read the log of output)

rmmod hello.ko

tail /var/log/messages(read the log of output)