#!/bin/bash
#
# Incremental Kernel Patch Builder
# Robin Johnson
# robbat2@orbis-terrarum.net
#
# Build an incremental diff between two kernel patches
# run as "./interpatch 2.4.13 ac7 ac8" to build patch-2.4.13-ac7-ac8.bz2
# this would require the follow files in the current directory:
# linux-2.4.13.tar.bz2
# patch-2.4.13-ac7.bz2
# patch-2.4.13-ac8.bz2
#
# REQUIRES tmpfs and lots of RAM for speed reasons
#
#

TAR_CMD="tar x"
COMPRESS_CMD="bzip2 -9c"
UNCOMPRESS_CMD="bzip2 -dc"
PATCH_CMD="patch -s -p1"
DIFF_CMD="diff -HurdN" #the Hurd kernel ? 
MOUNTCMD="mount -t tmpfs /dev/ram8"
MOUNTOPT=" -o size=512M" 

# -----------------------------------------
# NO USER CONFIGURATION BEYOND THIS!
# -----------------------------------------

KERNELVERSION=$1
PATCHLEVEL1=$2
PATCHLEVEL2=$3

SRC="linux-${KERNELVERSION}.tar.bz2"
OLDVERSION="${KERNELVERSION}-${PATCHLEVEL1}"
NEWVERSION="${KERNELVERSION}-${PATCHLEVEL2}"
OLDDIR="linux-${OLDVERSION}"
NEWDIR="linux-${NEWVERSION}"
PATCH1="patch-${OLDVERSION}.bz2"
PATCH2="patch-${NEWVERSION}.bz2"
TARGET="patch-${KERNELVERSION}-${PATCHLEVEL1}-${PATCHLEVEL2}"

SRCDIR=`pwd`
TMPDIR=`mktemp -q -d kernpatch.XXXXXX`


echo "Setting up space..."
${MOUNTCMD} ${TMPDIR} ${MOUNTOPT}

cd ${TMPDIR}

echo "Extracting..." 
${UNCOMPRESS_CMD} ${SRCDIR}/${SRC} | ${TAR_CMD}

echo "Copying..." 
mv linux $OLDDIR
cp -r $OLDDIR $NEWDIR

echo "Patching #1..."
${UNCOMPRESS_CMD} ${SRCDIR}/${PATCH1} | ${PATCH_CMD} -d $OLDDIR
echo "Patching #2..."
${UNCOMPRESS_CMD} ${SRCDIR}/${PATCH2} | ${PATCH_CMD} -d $NEWDIR
echo "Building diff..."
${DIFF_CMD} $OLDDIR $NEWDIR > ${TARGET}

echo "Compressing diff..."
${COMPRESS_CMD} ${TARGET} > ${SRCDIR}/${TARGET}.bz2

cd ${SRCDIR}

echo "Cleaning up..."
rm -rf ${TMPDIR}/*
umount ${TMPDIR}
rm -rf ${TMPDIR}