HOW TO REBUILD A LINUX KERNEL MODULES FROM SRPM

                       (c) 2006 Hiro Sugawara

It often happens that I need to create a new driver kernel module for
my Linux servers running versions of Fedora Core. The kernel source
package installed during the binary distribution installation under
/usr/src/kernels does not help any more than referencing include files
becasue there are no *.c file to compile. Neither does the tarball
from kernel.org because it is just a generic plain kernel and does not
have the spec file (or whatever necessary) for the particular builds
running on my servers.

Here's how to make it possible to build a new kernel module using
build-specific source tree from an SRPM. The following uses the
latest Fedora Core 5 as of writing to show examples.

This document was originally derived from
http://www.bonsai.com/ken/ace_tao_rpm/srpm_howto.txt.

Create personal RPM work area
=============================
The default RPM configuration assumes host-wide operations performed
by root. To avoid building things as root...

	$ mkdir -p ~/rpm/{BUILD,RPMS,SOURCES,SPECS,SRPMS,tmp}

	$ cat > ~/.rpmmacros
	%_topdir        %(echo ${HOME}/rpm)
	%_tmppath       %{_topdir}/tmp

	%packager       Firstname Lastname <your.address@here>

	# Have built RPMs land in RPMS/ instead of RPMS/<arch>/
	%_rpmfilename  %%{NAME}-%%{VERSION}-%%{RELEASE}.%%{ARCH}.rpm
	^D


Install SRPM
============
To download the SRPM from one of mirros and project in ~/rpm/SOURCES...

	$ rpm -U ftp://mirror.linux.duke.edu/pub/fedora/linux/core/updates/5/SRPMS/kernel-2.6.17-1.2187_FC5.src.rpm

The ~/rpm/SOURCE directory will get populated with a bunch of files--do
not worry about them. The SRPM spec file will take care of them...

Rename the spec file if necessary. This may be useful when one has
to deal with multiple kernel builds.

	$ cd ~/rpm/SPEC
	$ mv kernel-2.6.spec kernel-2.6.17-1.2187_FC5.spec
 

Set up build tree
=================
To create a compilable build tree under ~/rpm/BUILD...

	$ rpmbuild -bp --target i686 ~/rpm/SPECS/kernel-2.6.17-1.2187_FC5.spec

Rename the directory if necessary for the same reason as the spec file.

	$ cd ~/rpm/BUILD
	$ mv kernel-2.6.17 kernel-2.6.17-1.2187_FC5


Pick up the right config file
=============================

	$ cd ~/rpm/BUILD/kernel-2.6.17-1.2187_FC5/linux-2.6.17.i686
	$ cp configs/kernel-2.6.17-i686.config .config


Build target modules
====================

	$ cat Makefile
	ifneq ($(KERNELRELEASE),)
	# kbuilt portion
	obj-m	:= mymod.o
	mymod-y	:= mymod-1.o mymod-2.o
	else
	# normal portion
	KDIR	:= $(HOME)/rpm/BUILD/kernel-2.6.17-1.2187_FC5/linux-2.6.17.i686

	all: myprog mymod.ko
	
	myprog: myprog-1.o myprog-2.o
	
	mymod.ko:
		$(MAKE) -C $(KDIR)  M=`pwd`

	clean:
		$(MAKE) -C $(KDIR)  M=`pwd` clean
	endif