This is a simple example of modules.

Compile:
  Save this file name it helloworld.c
  # echo "obj-m := helloworld.o" > Makefile
  # make -Wall -C /lib/modules/`uname -r`/build M=`pwd` modules
Load the module:
  #insmod helloworld.ko


從/var/log/kern.log  insmod and rmmod printk 印出來字串