LXR Guide

LXR, shortened for Linux Cross-Reference, is a perl web application that lets you read linux kernel source code of different versions with the benefit of having static values and functions 'linked' to each other which makes it a good reference when dealing with kernel source.

Step by Step Guide

Prerequisites

Install required packages. Unfortunately, there are a few packages that are not available through yum (through default repos), and must be built through CPAN. screen is not a dependency, but it is nice to run the indexer through it as it can take from hours to days depending on your hardware.

yum --nogpgcheck install \
    perl-CGI-Ajax \
    perl-CGI-Simple \
    perl-CPAN \
    perl-DBD-Pg \
    perl-DBI \
    perl-Devel-Size \
    perl-ExtUtils-CBuilder \
    perl-ExtUtils-MakeMaker \
    perl-ExtUtils-Embed \
    perl-PerlIO-gzip \
    perl-HTML-Entities* \
    perl-Term-ProgressBar \
    perl-Template* \
    xapian* \
    postgresql postgresql-server \
    httpd \
    mod_perl \
    mod_perl-devel \
    ctags-etags \
    make gcc gcc-c++ \
    git \
    screen

lxr expects it as ctag as ctags-exuberant.

 ln -s /usr/bin/ctags /usr/bin/ctags-exuberant

Install the missing dependencies through CPAN:

 perl -MCPAN -e "install Search::Xapian Apache2::Reload"

Setting up PostgreSQL

With PostgreSQL installed, set it up with a lxrng database. You may want to set up permissions as well, but I will be using the root account.

/etc/init.d/postgresql initdb
/etc/init.d/postgresql start

sudo -u postgres psql
  ALTER USER postgres WITH ENCRYPTED PASSWORD 'lxrng';
  CREATE DATABASE lxrng;
  \q

# Use passwords
sed -i "s/ident$/md5/g" /var/lib/pgsql/data/pg_hba.conf

# Apply changes by restarting
/etc/init.d/postgresql restart

# Make sure postgres starts on startup
chkconfig postgresql on --level 345

LXRng Setup

We will be putting LXRng into /export

mkdir /export
cd /export
# Source is from git. If unavailable, there is a copy at http://pages.cpsc.ucalgary.ca/~leo/support/packages/src/lxrng*.tar.gz
git clone git://lxr.linux.no/git/lxrng.git

Edit LXRng's configuration at lxrng.conf. Make sure the database settings and URL is correct.

cd lxrng
cp lxrng.conf-dist lxrng.conf
sed -i "s/\/var\/lib/\/export/g" /export/lxrng/lxrng.conf
sed -i "s/db_user => \"\"/db_user => \"postgres\"/g" /export/lxrng/lxrng.conf
sed -i "s/db_pass => \"\"/db_pass => \"lxrng\"/g" /export/lxrng/lxrng.conf
sed -i "s/localhost/lxr.lab.cpsc.ucalgary.ca/g" /export/lxrng/lxrng.conf
sed -i "s/'ver_default'\s*=>\s*'[a-z0-9.]*'/'ver_default' => 'v2.6.32'/g" /export/lxrng/lxrng.conf

Set up a few directories such as repos which will contain all the source code to be referenced.

mkdir repos
mkdir -p text-db/linux-2.6
mkdir cache
chmod 777 cache
touch lxr-ctags-quirks

Fetch the Kernel Source

Get the source code either via git or from an existing tarball.

cd repos

# wget http://pages.cpsc.ucalgary.ca/~leo/support/linux-2.6-source.tar.gz -O - | tar -xzf -
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git

# or for the newest post-2.6 kernels:
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

Start the indexing process:

cd /export/lxrng
./lxr-db-admin linux --init
screen -d -m ./lxr-genxref linux

Setting up Apache

cd /export/lxrng
cp apache2-site.conf-dist-mod_perl /etc/httpd/conf.d/lxrng.conf
sed -i "s/@@LXRROOT@@/\/export\/lxrng/g" /etc/httpd/conf.d/lxrng.conf
sed -i "s/@@LXRURL@@/lxr/g" /etc/httpd/conf.d/lxrng.conf
sed -i "s/^[\(^#\)]*/# /" /etc/httpd/conf.d/welcome.conf
/etc/init.d/httpd start
chkconfig httpd on --level 345

Run 'screen -r' to view the progress of the cross reference generation progress

Updating Kernel Source

cd repos
git pull git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git master