#!/bin/bash
#
# kpatch build script
#
# Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
# Copyright (C) 2013,2014 Josh Poimboeuf <jpoimboe@redhat.com>
#
# 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 2
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA,
# 02110-1301, USA.

# This script takes a patch based on the version of the kernel
# currently running and creates a kernel module that will
# replace modified functions in the kernel such that the
# patched code takes effect.

# This script currently only works on Fedora and will need to be adapted to
# work on other distros.

# This script:
# - Downloads the kernel src rpm for the currently running kernel
# - Unpacks and prepares the src rpm for building
# - Builds the base kernel (vmlinux)
# - Builds the patched kernel and monitors changed objects
# - Builds the patched objects with gcc flags -f[function|data]-sections
# - Runs kpatch tools to create and link the patch kernel module

BASE="$PWD"
LOGFILE="/tmp/kpatch-build-$(date +%s).log"
SCRIPTDIR="$(readlink -f $(dirname $(type -p $0)))"
ARCHVERSION="$(uname -r)"
DISTROVERSION="${ARCHVERSION%*.*}"
LOCALVERSION="-${ARCHVERSION##*-}"
CPUS="$(grep -c ^processor /proc/cpuinfo)"
CACHEDIR="$HOME/.kpatch"
SRCDIR="$CACHEDIR/$ARCHVERSION/src"
OBJDIR="$CACHEDIR/$ARCHVERSION/obj"
OBJDIR2="$CACHEDIR/$ARCHVERSION/obj2"
TEMPDIR=
STRIPCMD="strip -d --keep-file-symbols"
APPLIEDPATCHFILE="applied-patch"
DEBUG=0

die() {
	if [[ -z $1 ]]; then
		echo "ERROR: kpatch build failed. Check $LOGFILE for more details." >&2
	else
		echo "ERROR: $1" >&2
	fi
	exit 1
}

cleanup() {
	[[ "$DEBUG" -eq 0 ]] && rm -rf "$TEMPDIR"
	if [[ -e "$SRCDIR/$APPLIEDPATCHFILE" ]]; then
		patch -p1 -R -d "$SRCDIR" < "$SRCDIR/$APPLIEDPATCHFILE" &> /dev/null
		rm -f "$SRCDIR/$APPLIEDPATCHFILE"
	fi
}

find_dirs() {
	if [[ -e "$SCRIPTDIR/create-diff-object" ]]; then
		# git repo
		TOOLSDIR="$SCRIPTDIR"
		DATADIR="$(readlink -f $SCRIPTDIR/../kmod)"
		SYMVERSFILE="$DATADIR/core/Module.symvers"
		return
	elif [[ -e "$SCRIPTDIR/../libexec/kpatch/create-diff-object" ]]; then
		# installation path
		TOOLSDIR="$(readlink -f $SCRIPTDIR/../libexec/kpatch)"
		DATADIR="$(readlink -f $SCRIPTDIR/../share/kpatch)"
		SYMVERSFILE="$(readlink -f $SCRIPTDIR/../lib/modules/$(uname -r)/kpatch/Module.symvers)"
		return
	fi

	return 1
}

usage() {
	echo "usage: $0 [options] <patch file>" >&2
	echo "		-h, --help	Show this help message" >&2
	echo "		-s, --sourcedir	Specify kernel source directory" >&2
	echo "		-c, --config	Specify kernel config file" >&2
	echo "		-d, --debug	Keep scratch files in /tmp" >&2
}

options=$(getopt -o hs:c:d -l "help,sourcedir:,config:,debug" -- "$@") || die "getopt failed"

eval set -- "$options"

while [[ $# -gt 0 ]]; do
	case "$1" in
	-h|--help)
		usage
		exit 0
		;;
	-s|--sourcedir)
		USERSRCDIR=$(readlink -f "$2")
		shift
		[[ ! -d "$USERSRCDIR" ]] && die "source dir $USERSRCDIR not found"
		;;
	-c|--config)
		CONFIGFILE=$(readlink -f "$2")
		shift
		[[ ! -f "$CONFIGFILE" ]] && die "config file $CONFIGFILE not found"
		;;
	-d|--debug)
		echo "DEBUG mode enabled"
		DEBUG=1
		;;
	--)
		if [[ -z "$2" ]]; then
			usage
			exit 1
		fi
		PATCHFILE=$(readlink -f "$2")
		[[ ! -f "$PATCHFILE" ]] && die "patch file $PATCHFILE not found"
		break
		;;
	esac
	shift
done

PATCHNAME="$(basename $PATCHFILE)"
if [[ "$PATCHNAME" =~ \.patch ]] || [[ "$PATCHNAME" =~ \.diff ]]; then
	PATCHNAME="${PATCHNAME%.*}"
fi

TEMPDIR="$(mktemp -d)" || die "mktemp failed"

trap cleanup EXIT INT TERM

find_dirs || die "can't find supporting tools"

[[ -e "$SYMVERSFILE" ]] || die "can't find core module Module.symvers"

if [[ -d "$SRCDIR" ]] || [[ -n "$USERSRCDIR" ]]; then
	if [[ -n "$USERSRCDIR" ]]; then
		SRCDIR="$CACHEDIR/src"
		OBJDIR="$CACHEDIR/obj"
		OBJDIR2="$CACHEDIR/obj2"

		rm -rf "$CACHEDIR"
		mkdir -p "$CACHEDIR"
		mkdir -p "$OBJDIR" "$OBJDIR2"

		if [[ -n "$CONFIGFILE" ]]; then
			cp "$CONFIGFILE" "$OBJDIR/.config" || die "config file is missing"
		else
			cp "$USERSRCDIR/.config" "$OBJDIR" || die "source dir is missing a .config file"
		fi

		echo "Copying source to $SRCDIR"
		cp -a "$USERSRCDIR" "$SRCDIR" || die "copy failed"
	else
		echo "Using cache at $SRCDIR"
	fi
else
	rpm -q --quiet rpmdevtools || die "rpmdevtools not installed"
	rpm -q --quiet yum-utils || die "yum-utils not installed"

	echo "Downloading kernel source for $ARCHVERSION"
	yumdownloader --source --destdir "$TEMPDIR" "kernel-$ARCHVERSION" >> "$LOGFILE" 2>&1 || die

	echo "Unpacking kernel source"
	rpmdev-setuptree >> "$LOGFILE" 2>&1 || die
	rpm -ivh "$TEMPDIR/kernel-$DISTROVERSION.src.rpm" >> "$LOGFILE" 2>&1 || die
	rpmbuild -bp "--target=$(uname -m)" "$HOME/rpmbuild/SPECS/kernel.spec" >> "$LOGFILE" 2>&1 ||
		die "rpmbuild -bp failed.  you may need to run 'yum-builddep kernel' first."
	rm -rf "$CACHEDIR"
	mkdir -p "$OBJDIR"
	mv "$HOME"/rpmbuild/BUILD/kernel-*/linux-"$ARCHVERSION" "$SRCDIR" >> "$LOGFILE" 2>&1 || die

	cp "$SRCDIR/.config" "$OBJDIR" || die
	echo "$LOCALVERSION" > "$SRCDIR/localversion" || die
fi

echo "Testing patch file"
cd "$SRCDIR" || die
cp "$PATCHFILE" "$APPLIEDPATCHFILE" || die
patch -p1 < "$APPLIEDPATCHFILE" || die "source patch file failed to apply"
patch -p1 -R < "$APPLIEDPATCHFILE" &> /dev/null || die "reverse patch apply failed"

echo "Building original kernel"
make mrproper >> "$LOGFILE" 2>&1 || die
make "-j$CPUS" vmlinux "O=$OBJDIR" >> "$LOGFILE" 2>&1 || die
cp -LR "$DATADIR/patch" "$TEMPDIR" || die
cp "$OBJDIR/vmlinux" "$TEMPDIR" || die

echo "Building patched kernel"
patch -p1 < "$APPLIEDPATCHFILE" >> "$LOGFILE" 2>&1 || die
make "-j$CPUS" vmlinux "O=$OBJDIR" 2>&1 | tee -a "$TEMPDIR/patched_build.log" >> "$LOGFILE"
[[ "${PIPESTATUS[0]}" -eq 0 ]] || die

echo "Detecting changed objects"
grep CC "$TEMPDIR/patched_build.log" | grep -v -e init/version.o -e scripts/mod/devicetable-offsets.s -e scripts/mod/file2alias.o | awk '{print $2}' > "$TEMPDIR/changed_objs"
[[ ! -s "$TEMPDIR/changed_objs" ]] && die "no changed objects were detected"

echo "Rebuilding changed objects"
rm -rf "$OBJDIR2"
mkdir -p "$OBJDIR2"
cp "$OBJDIR/.config" "$OBJDIR2" || die
mkdir "$TEMPDIR/patched"
for i in $(cat $TEMPDIR/changed_objs); do
	KCFLAGS="-ffunction-sections -fdata-sections" make "$i" "O=$OBJDIR2" >> "$LOGFILE" 2>&1 || die
	$STRIPCMD "$OBJDIR2/$i" >> "$LOGFILE" 2>&1 || die
	mkdir -p "$TEMPDIR/patched/$(dirname $i)"
	cp -f "$OBJDIR2/$i" "$TEMPDIR/patched/$i" || die
	
done
patch -R -p1 < "$APPLIEDPATCHFILE" >> "$LOGFILE" 2>&1
rm -f "$APPLIEDPATCHFILE"
mkdir "$TEMPDIR/orig"
for i in $(cat $TEMPDIR/changed_objs); do
	rm -f "$i"
	KCFLAGS="-ffunction-sections -fdata-sections" make "$i" "O=$OBJDIR2" >> "$LOGFILE" 2>&1 || die
	$STRIPCMD -d "$OBJDIR2/$i" >> "$LOGFILE" 2>&1 || die
	mkdir -p "$TEMPDIR/orig/$(dirname $i)"
	cp -f "$OBJDIR2/$i" "$TEMPDIR/orig/$i" || die
done

echo "Extracting new and modified ELF sections"
cd "$TEMPDIR/orig"
FILES="$(find * -type f)"
cd "$TEMPDIR"
mkdir output
for i in $FILES; do
	mkdir -p "output/$(dirname $i)"
	"$TOOLSDIR"/create-diff-object "orig/$i" "patched/$i" "output/$i" 2>&1 |tee -a "$LOGFILE"
	[[ "${PIPESTATUS[0]}" -eq 0 ]] || die
done

echo "Building patch module: kpatch-$PATCHNAME.ko"
cp "$OBJDIR/.config" "$SRCDIR"
cd "$SRCDIR"
make prepare >> "$LOGFILE" 2>&1 || die
cd "$TEMPDIR/output"
ld -r -o ../patch/output.o $FILES >> "$LOGFILE" 2>&1 || die
cd "$TEMPDIR/patch"
"$TOOLSDIR"/add-patches-section output.o ../vmlinux >> "$LOGFILE" 2>&1 || die
KPATCH_BUILD="$SRCDIR" KPATCH_NAME="$PATCHNAME" KBUILD_EXTRA_SYMBOLS="$SYMVERSFILE" make "O=$OBJDIR" >> "$LOGFILE" 2>&1 || die
$STRIPCMD "kpatch-$PATCHNAME.ko" >> "$LOGFILE" 2>&1 || die
"$TOOLSDIR"/link-vmlinux-syms "kpatch-$PATCHNAME.ko" ../vmlinux >> "$LOGFILE" 2>&1 || die

cp -f "$TEMPDIR/patch/kpatch-$PATCHNAME.ko" "$BASE" || die

rm -f "$LOGFILE"

echo "SUCCESS"