A simple tourial for Linux 2.6.24 kernel module
Author: Charles Yang <chio.yang@gmail.com>
Linux Dist: Ubuntu 8.04 Hardy
1. Preparation
1.1 Download source code with apporiate version
Usually, the linux release distribution have no full kernel source code tree. So you should get a copy of kernel source from www.kernel.org. For convience, you had better download the same version as you running linux kernel.
You can type uname -r in you X-term, for example:
2.6.24-16-generic
1.2 Learn the document for Linux Kernel Module (LKM)
Once you plan to do modules development, you should refer to: $SRCDIR/Document/kbuild/modules.txt
In my ubuntu 8.04, I can find it in /usr/src/linux-headers-2.6.24-16/Documentation/kbuild
Now let read the document for module development..
1). How to build external module
From modules.txt, we know the simplest make command:
the <path-to-kernel> means the kernel source path.
For the running kernel use:
The -C option: change to the directory before execute the make command.
Actually, that will result in search the Makefile in /lib/modules/2.6.24-16-generic/build in my OS.
Notice: Most of files in /lib/modules/2.6.24-16-generic/build actually link to /usr/src/linux-headers-2.6.24-16/
The M=`pwd`: define a MACRO required by Makefile in /lib/modules/2.6.24-16-generic/build, which can tell the directory of current exernal module code.
Therefore you needn't write your own Makefile for build your modules, that's completed by kbuild - a good machism for kernel modules.
2. make target
make -C $KDIR M=`pwd` all
make -C $KDIR M=`pwd` modules
make -C $KDIR M=`pwd` modules_install
make -C $KDIR M=`pwd` clean
make -C $KDIR M=`pwd` help
the first 3 commands are absolutely same. For more details, you can refer to modules.txt
