#! /usr/bin/perl -w

use Cwd;

##############################
# Start user configurable bit
##############################

# Please use absolute paths too.
# you can't use ~'s in your paths here.

# the directory where you've checked out lvm, keep a seperate copy for uml,
# the uml kernel will have links to these files
$lvm_src="/home/thornber/sistina/LVM2";


# the debian root image, get it from here:
# http://prdownloads.sourceforge.net/user-mode-linux/root_fs_debian2.2_small.bz2
# unzip it once you've downloaded it
$root_fs="/home/thornber/uml/root_fs_debian2.2_small";

# these are 100 Meg files created with dd
# these become our PV's /dev/ubd/[1-4]
# I sometimes use ubd/1 as swap though.
@block_devices = ("/home/thornber/uml/scratch1",
		  "/home/thornber/uml/scratch2",
		  "/home/thornber/uml/scratch3",
		  "/home/thornber/uml/scratch4");

# directory where uml will be built, and the up, lvm-install scripts will
# be placed
$dest_dir="/home/thornber/builds/uml-lvm2";

# It must be 2.4.8, can be .gz or .bz2
$kernel_tarball="/home/thornber/packages/2.4/linux-2.4.9.tar";

###############################
# end of user configurable bit
###############################


$wd = cwd;
$uml_patch = $wd . "/uml.patch.bz2";
$lvm_uml_patch = $wd . "/uml-lvm.patch";
$driver = $lvm_src . "/driver/device-mapper";


# check we've got everything we need
&check_file($root_fs);
&check_dir($lvm_src);
&check_file($kernel_tarball);
&check_dir($dest_dir);
&check_file($uml_patch);
&check_file($lvm_uml_patch);


chdir($dest_dir);
&extract_kernel($dest_dir, $kernel_tarball);
chdir("linux");
&run_command("bzip2 -dc $uml_patch | patch -p1", "patching kernel with uml");
&run_command("patch -p1 < $lvm_uml_patch", "enabling LVM driver");

chdir("$dest_dir/linux");

&run_command("cd include/linux; ln -s $driver/device-mapper.h",
	     "linking device-mapper.h");

&run_command("cd drivers/md; ln -s $driver/dm.h", "linking dm.h");
&run_command("cd drivers/md; ln -s $driver/dm-fs.c", "linking dm-fs.c");
&run_command("cd drivers/md; ln -s $driver/dm-table.c", "linking dm-table.c");
&run_command("cd drivers/md; ln -s $driver/dm-target.c", 
	     "linking dm-target.c");
&run_command("cd drivers/md; ln -s $driver/dm.c", "linking dm.c");

chdir("$dest_dir/linux");
&run_command("make oldconfig ARCH=um", "making oldconfig ARCH=um");
&run_command("make dep ARCH=um", "making dependencies");
&run_command("make linux ARCH=um", "building linux uml");

chdir($dest_dir);
&run_command("ln -s $dest_dir/linux/linux uml", "creating link for linux");

chdir($dest_dir);
&run_command("ln -s $root_fs ./root_fs", "linking root filesystem");

chdir($dest_dir);
&link_devices();
&write_up();
&run_command("mkdir root_fs_mnt");
&write_lvm_install();

print "Dont forget to run $dest_dir/lvm-install as root\n";


sub write_lvm_install {
    open(OUT, "> lvm-install");
    print OUT "#! /bin/sh\n\n";
    print OUT <<"end";
mount root_fs root_fs_mnt -o loop
cd $lvm_src; make install; cd $dest_dir
umount root_fs_mnt
end

    close OUT;
    system "chmod +x lvm-install";
}


sub write_up {
    open(UP, "> up");
    print UP "#! /bin/sh\n\n./uml ";
    $count = 1;
    for $d (@block_devices) {
	print UP "ubd$count=ubd$count ";
	$count++;
    }
    print UP "\n";
    close UP;
    system("chmod +x up");
}

sub link_devices {
    $count = 1;
    foreach $d (@block_devices) {
	&run_command("ln -s $d ubd$count",
		     "linking block device ubd$count");
	$count++;
    }
}

sub extract_kernel {
    my($dest, $tb) = @_;
    my($cmd);
    if($tb =~ m/\.bz2/) {
	$cmd = "tar Ixf $tb";

    } elsif($tb =~ m/\.gz/) {
	$cmd = "tar zxf $tb";

    } else {
	$cmd = "tar xf $tb";
    }

    &run_command($cmd, "extracting kernel");
}

sub run_command {
    my($cmd) = shift;
    my($desc) = shift;
    my($r);
    print STDERR $desc, " ... ";
    $r = system("$cmd > /dev/null");
    if(!$r) {
	print STDERR "done.\n";
	return;
    } else {
	print STDERR "failed.\n";
	exit(1);
    }
}

sub check_file {
    $f = shift;
    if(! -e $f) {
	print STDERR "couldn't find $f\n";
	exit;
    }
}

sub check_dir {
    $f = shift;
    if(! -e $f || ! -d $f) {
	print STDERR "couldn't find a directory called $f\n";
	exit;
    }
}