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#!/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="0.9.7"
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' "$1" "$(fmt -w 80 <(echo "      $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. This is only useful on systems that have the sysfs livepatch signal interface. On other systems, the signaling should be done automatically by the OS and this subcommand is a no-op."
	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() {
	[[ -d "/sys/kernel/kpatch" ]]
}

core_loaded () {
	[[ -d "/sys/kernel/kpatch" ]] || [[ -d "/sys/kernel/livepatch" ]]
}

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"
        else
            warn "Livepatch process signaling is performed automatically on your system."
            warn "Skipping manual process signaling."
	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) -gt "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 $modname already loaded and enabled"
		fi
	else
		# Cleanup possibly loaded, but disabled patch.
		remove_module "$modname" "quiet"

		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 "$enabled" ]]; then
		if [[ -d "/sys/module/$modname" ]] ; then
			# Module is loaded, but already disabled
			return 0
		fi
		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

	if [[ "$#" -lt 2 || "$2" != "quiet" ]] ; then
		echo "unloading patch module: $modname"
	fi
	# ignore any error here because rmmod can fail if the module used
	# KPATCH_FORCE_UNSAFE.
	rmmod "$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"

	;;

"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