After reading about the amazing 5-seconds bootup I decided to once again compile a kernel myself. Compiling a kernel is almost trivial these days, but customizing the configuration can still be quite confusing. For example, the names of the modules in lsmod aren’t the ones you select as config options. To map them, I found some scripts in the LQWiki, but they weren’t that easily to use, and also programming in bash is just painful.

So i wrote a python variant, that takes an input config(for example your distributions config) and changes the reply to “y” for all config options if the respective module is loaded(ie. if ext3 is loaded, CONFIG_EXT3_FS=y will be set).

In almost all cases you still want to tweak the resulting config file with make menuconfig. Also keep in mind that some things don’t work that easily if compiled in, for example if firmware has to be loaded from a file, the disk should be accessible.

#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
Script to modify kernel config based on lsmod output
Copyright (C) 2008  Andreas Goelzer
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
Based on a previous config and the output of lsmod, this script determines
which modules could be compiled in and generates a new config.
See http://andreas.goelzer.de/kernel-config-based-on-lsmod-output for updates
"""

import re;
from optparse import OptionParser;
from os import popen;
from sys import stderr, stdout, stdin;

parser = OptionParser(version="%prog 0.31");
parser.add_option("-i", "--infile", dest="cfgfile",
                  help="input config file", default=".config", metavar="FILE");
parser.add_option("-o", "--outfile", dest="outfile",
                  help="output config file", default="-", metavar="FILE");
parser.add_option("-l", "--logfile", dest="logfile",
                  help="file to log errors to", default="-", metavar="FILE");
parser.add_option("-s", "--sourcedir", dest="sourcedir",
                  help="kernel source tree", default=".", metavar="DIR");
#parser.add_option("-v", "--verbose",
                  #action="store_true", dest="verbose", default=False,
                  #help="print debug messages");

(options, args) = parser.parse_args();
if(options.outfile == '-'): of = stdout;
else: of = open(options.outfile, 'w');
if(options.logfile != '-'): stderr = open(options.logfile, 'w');


loadedmods=popen('lsmod | tail -n+2').readlines();
getmodname=re.compile(r"^(?P<modname>\w*)");

#prob. need to replace kernel with sth. like (kernel|ubuntu) for an ubuntu kernel source
parsepath=re.compile(r"/kernel(?P<path>/.*/)(?P<file>.*).ko")

wantin=[];
for module in loadedmods:
	modname = re.search(getmodname,module).group('modname');
	moduleprops=re.search(parsepath,popen('modinfo -n ' + modname).read());
	if(moduleprops):
		#search the makefile for the module name
		try:
			f=open(options.sourcedir + moduleprops.group('path') + 'Makefile' , 'r');
		except IOError:
			stderr.write('Could not find Makefile for ' + modname + '\n');
			continue
		cont=f.read();
		f.close();
		m=re.search(r"obj-\$\((?P<cfgname>[A-Z0-9_]*)\)\W*\+=\W*"+moduleprops.group('file')+r"\.o",cont);
		if(m):wantin.append(m.group('cfgname'));
		else:stderr.write('Could not determine config name for ' + modname + '\n');
	else:
		stderr.write('Could not parse modinfo for ' + modname + '\n');



if(options.cfgfile != '-'): 
	f=open(options.cfgfile, 'r');
	lines=f.readlines();
	f.close();
else:
	lines=stdin.readlines();

confparse = re.compile(r"\W*(?P<iscomment>#?)\W*(?P<cfgname>CONFIG_[A-Z0-9_]*)\W*=?\W*(?P<answer>[nmy]?)");

for line in lines:
	matches = re.search(confparse,line);
	if(matches and matches.group('cfgname') in wantin): 
		of.write(matches.group('cfgname')+'=y\n');
	else: 
		#if(matches and matches.group('answer') == 'm'):of.write(matches.group('cfgname')+'=n\n');
		of.write(line);

customconfig.py

To use the script, call it for example like ./customconfig.py -i /boot/config-2.6.24-21-generic -o .config if it is located in a linux kernel directory. Then modify the resulting config to suit your needs with make menuconfig, and then you can proceed to compile your kernel.