#!/bin/bash
#
# kpatch hot patch module management script
#
# Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
# Copyright (C) 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 is the kpatch user script that manages installing, loading, and
# displaying information about kernel patch modules installed on the system.

INSTALLDIR=/var/lib/kpatch
SCRIPTDIR="$(readlink -f $(dirname $(type -p $0)))"
VERSION="0.4.0"
POST_ENABLE_WAIT=5	# seconds
POST_SIGNAL_WAIT=60	# seconds

usage_cmd() {
	printf '   %-20s\n      %s\n' "$1" "$2" >&2
}

usage () {
	# ATTENTION ATTENTION ATTENTION ATTENTION ATTENTION ATTENTION
	# When changing this, please also update the man page.  Thanks!
	echo "usage: kpatch <command> [<args>]" >&2
	echo >&2
	echo "Valid commands:" >&2
	usage_cmd "install [-k|--kernel-version=<kernel version>] <module>" "install patch module to the initrd to be loaded at boot"
	usage_cmd "uninstall [-k|--kernel-version=<kernel version>] <module>" "uninstall patch module from the initrd"
	echo >&2
	usage_cmd "load --all" "load all installed patch modules into the running kernel"
	usage_cmd "load <module>" "load patch module into the running kernel"
	usage_cmd "unload --all" "unload all patch modules from the running kernel"
	usage_cmd "unload <module>" "unload patch module from the running kernel"
	echo >&2
	usage_cmd "info <module>" "show information about a patch module"
	echo >&2
	usage_cmd "list" "list installed patch modules"
	echo >&2
	usage_cmd "signal" "signal/poke any process stalling the current patch transition"
	echo >&2
	usage_cmd "version" "display the kpatch version"
	exit 1
}

warn() {
	echo "kpatch: $@" >&2
}

die() {
	warn "$@"
	exit 1
}

__find_module () {
	MODULE="$1"
	[[ -f "$MODULE" ]] && return

	MODULE=$INSTALLDIR/$(uname -r)/"$1"
	[[ -f "$MODULE" ]] && return

	return 1
}

mod_name () {
	MODNAME="$(basename $1)"
	MODNAME="${MODNAME%.ko}"
	MODNAME="${MODNAME//-/_}"
}

find_module () {
	arg="$1"
	if [[ "$arg" =~ \.ko ]]; then
		__find_module "$arg" || return 1
		mod_name "$MODULE"
		return
	else
		for i in $INSTALLDIR/$(uname -r)/*; do
			mod_name "$i"
			if [[ $MODNAME == $arg ]]; then
				MODULE="$i"
				return
			fi
		done
	fi

	return 1
}

find_core_module() {
	COREMOD="$SCRIPTDIR"/../kmod/core/kpatch.ko
	[[ -f "$COREMOD" ]] && return

	COREMOD="/usr/local/lib/kpatch/$(uname -r)/kpatch.ko"
	[[ -f "$COREMOD" ]] && return

	COREMOD="/usr/lib/kpatch/$(uname -r)/kpatch.ko"
	[[ -f "$COREMOD" ]] && return

	COREMOD="/usr/local/lib/modules/$(uname -r)/extra/kpatch/kpatch.ko"
	[[ -f "$COREMOD" ]] && return

	COREMOD="/usr/lib/modules/$(uname -r)/extra/kpatch/kpatch.ko"
	[[ -f "$COREMOD" ]] && return

	return 1
}

core_loaded () {
	grep -q -e "T klp_register_patch" -e "T kpatch_register" /proc/kallsyms
}

get_module_name () {
	echo $(readelf -p .gnu.linkonce.this_module $1 | grep '\[.*\]' | awk '{print $3}')
}

init_sysfs_var() {
	# If the kernel is configured with CONFIG_LIVEPATCH, use that.
	# Otherwise, use the kpatch core module (kpatch.ko).
	if [[ -e /sys/kernel/livepatch ]] ; then
		# livepatch ABI
		SYSFS="/sys/kernel/livepatch"

	elif [[ -e /sys/kernel/kpatch/patches ]] ; then
		# kpatch pre-0.4 ABI
		SYSFS="/sys/kernel/kpatch/patches"

	else
		# kpatch 0.4 ABI
		SYSFS="/sys/kernel/kpatch"
	fi
}

verify_module_checksum () {
	modname=$(get_module_name $1)
	[[ -z $modname ]] && return 1

	checksum="$(readelf -p .kpatch.checksum "$1" 2>&1 | grep '\[.*\]' | awk '{print $3}')"

	# Fail checksum match only if both exist and diverge
	if [[ ! -z $checksum ]] && [[ -e "$SYSFS/${modname}/checksum" ]] ; then
		sysfs_checksum=$(cat $SYSFS/${modname}/checksum)
		[[ $checksum == $sysfs_checksum ]] || return 1
	fi

	return 0
}

in_transition() {
	local moddir="$SYSFS/$1"
	[[ $(cat "$moddir/transition" 2>/dev/null) == "1" ]] && return 0
	return 1
}

is_stalled() {
	local module="$1"
	local pid="$2"
	local patch_enabled
	local patch_state

	patch_enabled="$(cat "$SYSFS/$module/enabled" 2>/dev/null)"
	patch_state="$(cat "/proc/$pid/patch_state" 2>/dev/null)"

	# No patch transition in progress
	[[ "$patch_state" == "-1" ]] && return 1

	[[ -z "$patch_enabled" ]] || [[ -z "$patch_state" ]] && return 1

	# Stalls can be determined if the process state does not match
	# the transition target (ie, "enabled" and "patched", "disabled"
	# and "unpatched").  The state value enumerations match, so we
	# can just compare them directly:
	[[ "$patch_enabled" != "$patch_state" ]] && return 0
	return 1
}

get_transition_patch() {
	local module
	local modname
	for module in "$SYSFS"/*; do
		modname=$(basename "$module")
		if in_transition "$modname" ; then
			echo "$modname"
			return
		fi
	done
}

show_stalled_processes() {
	local module
	local proc_task
	local tid

	module=$(get_transition_patch)
	[[ -z "$module" ]] && return

	echo ""
	echo "Stalled processes:"
	for proc_task in /proc/[0-9]*/task/[0-9]*; do
		tid=${proc_task#*/task/}
		is_stalled "$module" "$tid" && echo "$tid $(cat "$proc_task"/comm 2>/dev/null)"
	done
}

signal_stalled_processes() {
	local module
	local proc_task
	local tid

	module=$(get_transition_patch)
	[[ -z "$module" ]] && return

	if [[ -e "/sys/kernel/livepatch/$module/signal" ]] ; then
		echo 1 > "/sys/kernel/livepatch/$module/signal"
	else
		for proc_task in /proc/[0-9]*/task/[0-9]*; do
			tid=${proc_task#*/task/}
			if is_stalled "$module" "$tid" ; then
				if [[ "$tid" -eq "$$" ]] ; then
					echo "skipping pid $tid $(cat "$proc_task"/comm 2>/dev/null)"
				else
					echo "signaling pid $tid $(cat "$proc_task"/comm 2>/dev/null)"
					kill -SIGSTOP "$tid"
					sleep .1
					kill -SIGCONT "$tid"
				fi
			fi
		done
	fi
}

wait_for_patch_transition() {
	local module="$1"
	local i

	in_transition "$module" || return 0

	echo "waiting (up to $POST_ENABLE_WAIT seconds) for patch transition to complete..."
	for (( i=0; i<POST_ENABLE_WAIT; i++ )); do
		if ! in_transition "$module" ; then
			echo "transition complete ($i seconds)"
			return 0
		fi
		sleep 1s
	done

	echo "patch transition has stalled, signaling stalled process(es):"
	signal_stalled_processes

	echo "waiting (up to $POST_SIGNAL_WAIT seconds) for patch transition to complete..."
	for (( i=0; i<POST_SIGNAL_WAIT; i++ )); do
		if ! in_transition "$module" ; then
			echo "transition complete ($i seconds)"
			return 0
		fi
		sleep 1s
	done

	return 1
}

load_module () {
	local module="$1"

	if ! core_loaded; then
		if modprobe -q kpatch; then
			echo "loaded core module"
		else
			find_core_module || die "can't find core module"
			echo "loading core module: $COREMOD"
			insmod "$COREMOD" || die "failed to load core module"
		fi

		# Now that the core module has been loaded, set $SYSFS to the
		# correct value based on the loaded core module's ABI.
		init_sysfs_var
	fi

	local modname=$(get_module_name $module)
	local moddir="$SYSFS/$modname"
	if [[ -d $moddir ]] ; then
		if [[ $(cat "${moddir}/enabled") -eq 0 ]]; then
			if verify_module_checksum $module; then # same checksum
				echo "module already loaded, re-enabling"
				echo 1 > ${moddir}/enabled || die "failed to re-enable module $modname"
				if ! wait_for_patch_transition "$modname" ; then
					echo "module $modname did not complete its transition, disabling..."
					echo 0 > "${moddir}/enabled" || die "failed to disable module $modname"
					wait_for_patch_transition "$modname"
					die "error: failed to re-enable module $modname (transition stalled), patch disabled"
				fi

				return
			else
				die "error: cannot re-enable patch module $modname, cannot verify checksum match"
			fi
		else
			die "error: module named $modname already loaded and enabled"
		fi
	fi

	echo "loading patch module: $module"
	local i=0
	while true; do
		out=$(insmod "$module" 2>&1)
		[[ -z $out ]] && break
		echo $out 1>&2
		[[ ! $out =~ "Device or resource busy" ]] &&
			die "failed to load module $module"

		# "Device or resource busy" means the activeness safety check
		# failed.  Retry in a few seconds.
		i=$((i+1))
		if [[ $i = 5 ]]; then
			die "failed to load module $module"
			break
		else
			warn "retrying..."
			sleep 2
		fi
	done

	if ! wait_for_patch_transition "$modname" ; then
		echo "module $modname did not complete its transition, unloading..."
		unload_module "$modname"
		die "error: failed to load module $modname (transition stalled)"
	fi

	return 0
}

unload_module () {
	PATCH="${1//-/_}"
	PATCH="${PATCH%.ko}"
	ENABLED="$SYSFS/$PATCH/enabled"
	[[ -e "$ENABLED" ]] || die "patch module $1 is not loaded"
	if [[ $(cat "$ENABLED") -eq 1 ]]; then
		echo "disabling patch module: $PATCH"
		echo 0 > $ENABLED || die "can't disable $PATCH"
	fi

	if ! wait_for_patch_transition "$PATCH" ; then
		die "error: failed to unload module $PATCH (transition stalled)"
	fi


	echo "unloading patch module: $PATCH"
	# ignore any error here because rmmod can fail if the module used
	# KPATCH_FORCE_UNSAFE.
	rmmod $PATCH 2> /dev/null || return 0
}

get_module_version() {
	MODVER=$(modinfo -F vermagic "$1") || return 1
	MODVER=${MODVER/ */}
}

unset MODULE

# Initialize the $SYSFS var.  This only works if the core module has been
# loaded.  Otherwise, the value of $SYSFS doesn't matter at this point anyway,
# and we'll have to call this function again after loading it.
init_sysfs_var

[[ "$#" -lt 1 ]] && usage
case "$1" in
"load")
	[[ "$#" -ne 2 ]] && usage
	case "$2" in
	"--all")
		for i in "$INSTALLDIR"/$(uname -r)/*.ko; do
			[[ -e "$i" ]] || continue
			load_module "$i" || die "failed to load module $i"
		done
		;;
	*)
		PATCH="$2"
		find_module "$PATCH" || die "can't find $PATCH"
		load_module "$MODULE" || die "failed to load module $PATCH"
		;;
	esac
	;;

"unload")
	[[ "$#" -ne 2 ]] && usage
	case "$2" in
	"--all")
		for module in $SYSFS/*; do
			[[ -e $module ]] || continue
			unload_module $(basename $module) || die "failed to unload module $module"
		done
		;;
	*)
		unload_module "$(basename $2)" || die "failed to unload module $2"
		;;
	esac
	;;

"install")
	KVER=$(uname -r)
	shift
	options=$(getopt -o k: -l "kernel-version:" -- "$@") || die "getopt failed"
	eval set -- "$options"
	while [[ $# -gt 0 ]]; do
		case "$1" in
		-k|--kernel-version)
			KVER=$2
			shift
			;;
		--)
			[[ -z "$2" ]] && die "no module file specified"
			PATCH="$2"
			;;
		esac
		shift
	done

	[[ ! -e "$PATCH" ]] && die "$PATCH doesn't exist"
	[[ ${PATCH: -3} == ".ko" ]] || die "$PATCH isn't a .ko file"

	get_module_version "$PATCH" || die "modinfo failed"
	[[ $KVER != $MODVER ]] && die "invalid module version $MODVER for kernel $KVER"

	[[ -e $INSTALLDIR/$KVER/$(basename "$PATCH") ]] && die "$PATCH is already installed"

	echo "installing $PATCH ($KVER)"
	mkdir -p $INSTALLDIR/$KVER || die "failed to create install directory"
	cp -f "$PATCH" $INSTALLDIR/$KVER || die "failed to install module $PATCH"
	systemctl enable kpatch.service
	;;

"uninstall")
	KVER=$(uname -r)
	shift
	options=$(getopt -o k: -l "kernel-version:" -- "$@") || die "getopt failed"
	eval set -- "$options"
	while [[ $# -gt 0 ]]; do
		case "$1" in
		-k|--kernel-version)
			KVER=$2
			shift
			;;
		--)
			[[ -z "$2" ]] && die "no module file specified"
			PATCH="$2"
			[[ "$PATCH" != $(basename "$PATCH") ]] && die "please supply patch module name without path"
			;;
		esac
		shift
	done

	MODULE=$INSTALLDIR/$KVER/"$PATCH"
	if [[ ! -f "$MODULE" ]]; then
		mod_name "$PATCH"
		PATCHNAME=$MODNAME
		for i in $INSTALLDIR/$KVER/*; do
			mod_name "$i"
			if [[ $MODNAME == $PATCHNAME ]]; then
				MODULE="$i"
				break
			fi
		done
	fi

	[[ ! -e $MODULE ]] && die "$PATCH is not installed for kernel $KVER"
	

	echo "uninstalling $PATCH ($KVER)"
	rm -f $MODULE || die "failed to uninstall module $PATCH"
	;;

"list")
	[[ "$#" -ne 1 ]] && usage
	echo "Loaded patch modules:"
	for module in $SYSFS/*; do
		if [[ -e "$module" ]]; then
			modname=$(basename "$module")
			if [[ "$(cat "$module/enabled" 2>/dev/null)" -eq 1 ]]; then
				in_transition "$modname" && state="enabling..." \
							 || state="enabled"
			else
				in_transition "$modname" && state="disabling..." \
							 || state="disabled"
			fi
			echo "$modname [$state]"
		fi
	done
	show_stalled_processes
	echo ""
	echo "Installed patch modules:"
	for kdir in $INSTALLDIR/*; do
		[[ -e "$kdir" ]] || continue
		for module in $kdir/*; do
			[[ -e "$module" ]] || continue
			mod_name "$module"
			echo "$MODNAME ($(basename $kdir))"
		done
	done
	;;

"info")
	[[ "$#" -ne 2 ]] && usage
	PATCH="$2"
	find_module "$PATCH" || die "can't find $PATCH"
	echo "Patch information for $PATCH:"
	modinfo "$MODULE" || die "failed to get info for module $PATCH"
	;;

"signal")
	[[ "$#" -ne 1 ]] && usage
	signal_stalled_processes
	;;

"help"|"-h"|"--help")
	usage
	;;

"version"|"-v"|"--version")
	echo "$VERSION"
	;;

*)
	echo "subcommand $1 not recognized"
	usage
	;;
esac