Linux kernel module

hello.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>

MODULE_AUTHOR("sloger");
MODULE_LICENSE("GPLv3");
MODULE_DESCRIPTION("Hello Kernel");

static int __init printk_init(void)
{
    printk(KERN_ALERT "Hello Kernel!\n");

    return 0;
}

static void __exit printk_exit(void)
{
    printk(KERN_ALERT "Good Bye!\n");
}


module_init(printk_init);
module_exit(printk_exit);

Makefile

ifneq ($(KERNELRELEASE),)
	obj-m := hello.o
else
	KERNELDIR ?= /lib/modules/$(shell uname -r)/build

PWD := $(shell pwd)

all:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

clean:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) clean
endif