Kernel module和Makefile範例

1. 準備hello.c和Makefile

$ vi hello.c

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

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Allen");
MODULE_DESCRIPTION("A Simple Hello World module");

static int __init hello_init(void)
{
    printk(KERN_INFO "Enter module. Hello world!\n");
    return 0;
}

static void __exit hello_exit(void)
{
    printk(KERN_INFO "Exit module.\n");
}

module_init(hello_init);
module_exit(hello_exit);

$ vi Makefile

obj-m += hello.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

2. 編譯Hello world的kernel module

$ make
make -C /lib/modules/3.11.0-15-generic/build M=/home/allen/Work/module modules
make[1]: Entering directory `/usr/src/linux-headers-3.11.0-15-generic'
  CC [M]  /home/allen/Work/module/hello.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/allen/Work/module/hello.mod.o
  LD [M]  /home/allen/Work/module/hello.ko
make[1]: Leaving directory `/usr/src/linux-headers-3.11.0-15-generic'


$ ls
hello.c   hello.mod.c  hello.o   modules.order
hello.ko  hello.mod.o  Makefile  Module.symvers

3. 掛載Hello world的kernel module

$ sudo insmod hello.ko

$ dmesg | tail -1
[18253.619885] Enter module. Hello world!

4. 卸載Hello world的kernel module

$ sudo rmmod hello

$ dmesg | tail -1
[18291.787154] Exit module.

5. 列出已掛載kernel module

$ lsmod | grep hello
hello                  12425  0

6. 顯示module的資訊

$ modinfo hello.ko
filename:       hello.ko
description:    A Simple Hello World module
author:         Allen
license:        GPL
srcversion:     4022E1AB22D5C59AACC7122
depends:
vermagic:       3.11.0-15-generic SMP mod_unload modversions

7. 參考來源
How to Write Your Own Linux Kernel Module with a Simple Example