#!/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="0.9.2"
POST_ENABLE_WAIT=15	# seconds
POST_SIGNAL_WAIT=60	# seconds
MODULE_REF_WAIT=15	# seconds

# How many times to try loading the patch if activeness safety check fails.
MAX_LOAD_ATTEMPTS=5
# How long to wait before retry, in seconds.
RETRY_INTERVAL=2

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 be loaded at boot"
	usage_cmd "uninstall [-k|--kernel-version=<kernel version>] <module>" "uninstall patch module"
	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 (UNSUPPORTED)" "unload all patch modules from the running kernel"
	usage_cmd "unload <module> (UNSUPPORTED)" "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
}

confirm_prompt() {
	local prompt="$1"
	local answer
	while true; do
		read -rp "$prompt [Y/N] " answer
		[[ $answer == 'Y' || $answer == 'y' ]] && return 0
		[[ $answer == 'N' || $answer == 'n' ]] && return 1
	done
}

__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
}

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

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

get_module_name () {
	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 [[ -n "$checksum" ]] && [[ -e "$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" "$tid" && echo -e "$tid $(cat "$proc_task"/comm 2>/dev/null)\nstack:\n$(cat "$proc_task"/stack 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/$module/signal" ]] ; then
		echo "signaling stalled process(es):"
		echo 1 > "/sys/kernel/livepatch/$module/signal"
	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!"
	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
}

module_ref_count() {
	local modname="$1"
	[[ $(cat "/sys/module/$modname/refcnt" 2>/dev/null) != "0" ]]
}

wait_for_zero_module_ref_count() {
	local modname="$1"
	local i=0

	# We can't rely on a zero refcount with kpatch.ko as it
	# implements KPATCH_FORCE_UNSAFE with an additional reference on
	# kpatch-patch modules to avoid potential crashes.
	kpatch_core_loaded && return 0

	module_ref_count "$modname" || return 0

	echo "waiting (up to $MODULE_REF_WAIT seconds) for module refcount..."
	for (( i=0; i<MODULE_REF_WAIT; i++ )); do
		module_ref_count "$modname" || return 0
		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
	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
					show_stalled_processes
					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
			echo "module named $modname already loaded and enabled"
		fi
	else
		echo "loading patch module: $module"
		local i=0
		while true; do
			out="$(LC_ALL=C 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 -eq $MAX_LOAD_ATTEMPTS ]]; then
				die "failed to load module $module"
				break
			else
				warn "retrying..."
				sleep $RETRY_INTERVAL
			fi
		done
	fi

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

	return 0
}

disable_patch () {
	local modname="$1"

	local enabled="$SYSFS/$modname/enabled"
	if ! [[ -e "$enabled" ]]; then
	    warn "patch module $modname is not loaded"
	    return 1
	fi

	if [[ "$(cat "$enabled")" -eq 1 ]]; then
		echo "disabling patch module: $modname"
		local i=0
		while true; do
			out="$(export LC_ALL=C; sh -c "echo 0 > $enabled" 2>&1)"
			[[ -z "$out" ]] && break
			echo "$out" 1>&2
			if [[ ! "$out" =~ "Device or resource busy" ]]; then
				return 1
			fi

			# "Device or resource busy" means the activeness safety check
			# failed.  Retry in a few seconds.
			i=$((i+1))
			if [[ $i -eq $MAX_LOAD_ATTEMPTS ]]; then
				return 1
			else
				warn "retrying..."
				sleep $RETRY_INTERVAL
			fi
		done
	fi
}

disable_patch_strict () {
	local modname="$1"

	disable_patch "$modname" || die "failed to disable module $modname"

	if ! wait_for_patch_transition "$modname" ; then
		die "transition stalled for $modname"
	fi
}

remove_module () {
	local modname="$1"

	if ! wait_for_zero_module_ref_count "$modname"; then
		die "failed to unload module $modname (refcnt)"
	fi

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

unload_module () {
	PATCH="${1//-/_}"
	PATCH="${PATCH%.ko}"
	disable_patch_strict "$PATCH"
	remove_module "$PATCH"
}

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

# RHEL-specific support options
case "$1" in
"force")
	# For scripting purposes, support "kpatch force unload".
	# Shift out the "force" to avoid the user-prompt check below.
	shift
	;;
"unload")
	confirm_prompt "WARNING: Red Hat doesn't support unloading of kpatches, continue anyway?" || exit 1
	;;
esac

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 "$2" in
	"--all")
		# Versions of linux < 5.1 livepatching require patches to be
		# disabled in the inverse order in which they were enabled.
		while true; do
			nr_disabled=0
			for module in "$SYSFS"/*; do
				modname="$(basename "$module")"

				[[ -e "$module" ]] || continue
				disable_patch "$modname" || continue
				if ! wait_for_patch_transition "$modname" ; then
				    warn "transition stalled for $modname"
				    continue
				fi
				remove_module "$modname"
				nr_disabled=$((nr_disabled + 1))
			done
			if [ $nr_disabled -eq 0 ]; then
				break
			fi
		done

		nr_remaining=0
		for module in "$SYSFS"/*; do
			modname="$(basename "$module")"

			[[ -e "$module" ]] || continue
			nr_remaining=$((nr_remaining + 1))
			warn "failed to unload module $modname"
		done

		if [ $nr_remaining -gt 0 ]; then
			exit 1
		fi
		;;
	*)
		unload_module "$(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"
	command -v systemctl > /dev/null 2>&1 && 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 $PATCH"
	rmdir --ignore-fail-on-non-empty "$INSTALLDIR/$KVER" || die "failed to remove directory $INSTALLDIR/$KVER"
	rmdir --ignore-fail-on-non-empty "$INSTALLDIR" || die "failed to remove directory $INSTALLDIR"

	;;

"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"/*.ko; 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