Write a simple Linux kernel module __linux

1. First, write the C program HELLOWORLD.C:

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
static int hello_init (void)
{
PRINTK ("<1>hello world!\n");
return 0;
}

static void Hello_exit (void)
{
PRINTK ("<1>goodbye!\n");
}

Module_init (Hello_init);
Module_exit (Hello_exit);
Module_license ("GPL");

2. Preparation of Makefile:

obj-m:=helloworld.o

All
Make-c/lib/modules/$ (Shell uname-r)/build m=$ (PWD) modules
Clean
Make-c/lib/modules/$ (Shell uname-r)/build m=$ (PWD) Clean

3. Run command make, producing the following file:
HELLOWORLD.O module.symvers Helloworld.ko helloworld.mod.c HELLOWORLD.MOD.O

4. Load into the kernel: Insmod Helloworld.ko

5. View Kernel module: lsmod | grep helloworld
Module Size Used by
HelloWorld 5504 0

6. Removal module: Rmmod Helloworld.ko