Dive in the Sky

$cd /usr/src

$sudo wget -O raspberrypi-linux-3.1.9.tar.gz https://github.com/raspberrypi/linux/tarball/

rpi-patches

$sudo tar xzf raspberrypi-linux-3.1.9.tar.gz

$sudo ln -s /usr/src/raspberrypi-linux-eab45cb /lib/modules/`uname -r`/build

$cd /usr/src/raspberrypi-linux-8fa2e19

$sudo sh -c 'zcat /proc/config.gz > .config'

$sudo sed -i 's/EXTRAVERSION =.*/EXTRAVERSION = +/' Makefile

$wget http://www.grendelman.net/files/raspi/Module.symvers

$sudo cp ~/Module.symvers .

$sudo make oldconfig

$sudo make modules_prepare

hello.c

// Defining __KERNEL__ and MODULE allows us to access kernel-level code not usually available to userspace programs.

#undef __KERNEL__

#define __KERNEL__

#undef MODULE

#define MODULE

// Linux Kernel/LKM headers: module.h is needed by all modules and kernel.h is needed for KERN_INFO.

#include <linux/module.h> // included for all kernel modules

#include <linux/kernel.h> // included for KERN_INFO

#include <linux/init.h> // included for __init and __exit macros

static int __init hello_init(void)

{

printk(KERN_INFO "Hello world!\n");

return 0; // Non-zero return means that the module couldn't be loaded.

}

static void __exit hello_cleanup(void)

{

printk(KERN_INFO "Cleaning up module.\n");

}

module_init(hello_init);

module_exit(hello_cleanup);

Makefile

obj-m := hello.o

KDIR := /lib/modules/$(shell uname -r)/build

PWD := $(shell pwd)

all:

$(MAKE) -C $(KDIR) M=$(PWD) modules

$sudo insmod hello.ko

$sudo rmmod hello

$dmesg

.

.

.

[ 2042.460603] Hello world!

[ 2092.632882] Cleaning up module.