#!/bin/sh

BOOTDIR=/boot
CONF=/etc/initramfs-tools/update-initramfs.conf
mode=""
version=""
update_initramfs=yes
backup_initramfs=no

set -e

[ -r ${CONF} ] && . ${CONF}

if [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ] && [ $# = 1 ] && [ "$1" = -u ]; then
	if dpkg-trigger --no-await update-initramfs; then
		echo "update-initramfs: deferring update (trigger activated)"
		exit 0
	fi
fi

usage()
{
	cat << EOF

Usage: update-initramfs {-c|-d|-u} [-k version] [-v] [-b directory]

Options:
 -k version	Specify kernel version or 'all'
 -c		Create a new initramfs
 -u		Update an existing initramfs
 -d		Remove an existing initramfs
 -b directory	Set alternate boot directory
 -v		Be verbose

See update-initramfs(8) for further details.

EOF
}

usage_error()
{
	if [ -n "${1:-}" ]; then
		printf "%s\\n\\n" "${*}" >&2
	fi
	usage >&2
	exit 2
}

mild_panic()
{
	if [ -n "${1:-}" ]; then
		printf "%s\\n" "${*}" >&2
	fi
	exit 0
}

panic()
{
	if [ -n "${1:-}" ]; then
		printf "%s\\n" "${*}" >&2
	fi
	exit 1
}

verbose()
{
	if [ "${verbose}" = 1 ]; then
		printf "%s\\n" "${*}"
	fi
}

set_initramfs()
{
	initramfs="${BOOTDIR}/initrd.img-${version}"
}


# backup initramfs while running
backup_initramfs()
{
	[ ! -r "${initramfs}" ] && return 0
	initramfs_bak="${initramfs}.dpkg-bak"
	[ -r "${initramfs_bak}" ] && rm -f "${initramfs_bak}"
	ln -f "${initramfs}" "${initramfs_bak}" \
		|| cp -a "${initramfs}" "${initramfs_bak}"
	verbose "Keeping ${initramfs_bak}"
}

# keep booted initramfs
backup_booted_initramfs()
{
	initramfs_bak="${initramfs}.dpkg-bak"

	# first time run thus no backup
	[ ! -r "${initramfs_bak}" ] && return 0

	# chroot with no /proc
	[ ! -r /proc/uptime ] && rm -f "${initramfs_bak}" && return 0

	# no kept backup wanted
	[ "${backup_initramfs}" = "no" ] && rm -f "${initramfs_bak}" && return 0

	# no backup yet
	if [ ! -r "${initramfs}.bak" ]; then
		mv -f ${initramfs_bak} "${initramfs}.bak"
		verbose "Backup ${initramfs}.bak"
		return 0
	fi

	# keep booted initramfs
	boot_initramfs=
	uptime_days=$(awk '{printf "%d", $1 / 3600 / 24}' /proc/uptime)
	if [ -n "$uptime_days" ]; then
		boot_initramfs=$(find "${initramfs}.bak" -mtime "+${uptime_days}")
	fi
	if [ -n "${boot_initramfs}" ]; then
		mv -f "${initramfs_bak}" "${initramfs}.bak"
		verbose "Backup ${initramfs}.bak"
		return 0
	fi
	verbose "Removing current backup ${initramfs_bak}"
	rm -f ${initramfs_bak}
}

# nuke generated copy
remove_initramfs_bak()
{
	[ -z "${initramfs_bak:-}" ] && return 0
	rm -f "${initramfs_bak}"
	verbose "Removing ${initramfs_bak}"
}


generate_initramfs()
{
	echo "update-initramfs: Generating ${initramfs}"
	OPTS="-o"
	if [ "${verbose}" = 1 ]; then
		OPTS="-v ${OPTS}"
	fi
	# shellcheck disable=SC2086
	if mkinitramfs ${OPTS} "${initramfs}.new" "${version}"; then
		mv -f "${initramfs}.new" "${initramfs}"
		# Guard against an unclean shutdown
		sync -f "${initramfs}"
	else
		mkinitramfs_return="$?"
		remove_initramfs_bak
		rm -f "${initramfs}.new"
		echo "update-initramfs: failed for ${initramfs} with $mkinitramfs_return." >&2
		exit $mkinitramfs_return
	fi
}

# Invoke bootloader
run_bootloader()
{
	# invoke policy conformant bootloader hooks
	if [ -d /etc/initramfs/post-update.d/ ]; then
		run-parts --arg="${version}" --arg="${initramfs}" \
			/etc/initramfs/post-update.d/
		return 0
	fi
}

# ro /boot is not modified
ro_boot_check()
{
	# check irrelevant inside of a chroot
	if [ ! -r /proc/mounts ] || ischroot; then
		return 0
	fi

	# shellcheck disable=SC1004
	boot_opts=$(awk '/boot/{if ((match($4, /^ro/) || match($4, /,ro/)) \
		&& $2 == "/boot") print "ro"}' /proc/mounts)
	if [ -n "${boot_opts}" ]; then
		echo "W: /boot is ro mounted." >&2
		echo "W: update-initramfs: Not updating ${initramfs}" >&2
		exit 0
	fi
}

get_sorted_versions()
{
	version_list="$(
		linux-version list |
		while read -r version; do
		      test -e "${BOOTDIR}/initrd.img-$version" && echo "$version"
		done |
		linux-version sort --reverse
		)"
	verbose "Available versions: ${version_list}"
}

set_current_version()
{
	if [ -f "/boot/initrd.img-$(uname -r)" ]; then
		version=$(uname -r)
	fi
}

set_linked_version()
{
	linktarget=
	if [ -e /initrd.img ] && [ -L /initrd.img ]; then
		linktarget="$(basename "$(readlink /initrd.img)")"
	fi

	if [ -e /boot/initrd.img ] && [ -L /boot/initrd.img ]; then
		linktarget="$(basename "$(readlink /boot/initrd.img)")"
	fi

	if [ -z "${linktarget}" ]; then
		return
	fi

	version="${linktarget##initrd.img-}"
}

set_highest_version()
{
	get_sorted_versions
	if [ -z "${version_list}" ]; then
		version=
		return
	fi
	# shellcheck disable=SC2086
	set -- ${version_list}
	version=${1}
}

create()
{
	if [ -z "${version}" ]; then
		usage_error "Create mode requires a version argument"
	fi

	set_initramfs

	generate_initramfs

	run_bootloader
}

update()
{
	if [ "${update_initramfs}" = "no" ]; then
		echo "update-initramfs: Not updating initramfs."
		exit 0
	fi

	if [ -z "${version}" ]; then
		set_highest_version
	fi

	if [ -z "${version}" ]; then
		set_linked_version
	fi

	if [ -z "${version}" ]; then
		set_current_version
	fi

	if [ -z "${version}" ]; then
		verbose "Nothing to do, exiting."
		exit 0
	fi

	set_initramfs

	ro_boot_check

	backup_initramfs

	generate_initramfs

	run_bootloader

	backup_booted_initramfs
}

delete()
{
	if [ -z "${version}" ]; then
		usage_error "Delete mode requires a version argument"
	fi

	set_initramfs

	echo "update-initramfs: Deleting ${initramfs}"

	rm -f "${initramfs}" "${initramfs}.bak"
}

# Defaults
verbose=0

##

OPTIONS=$(getopt -o "k:cudvtb:h?" --long help -n "$0" -- "$@") || usage_error

eval set -- "$OPTIONS"

while true; do
	case "$1" in
	-k)
		version="$2"
		shift 2
		;;
	-c)
		mode="c"
		shift
		;;
	-d)
		mode="d"
		shift
		;;
	-u)
		mode="u"
		shift
		;;
	-v)
		verbose="1"
		shift
		;;
	-t)
		# accepted for compatibility, but ignored
		shift
		;;
	-b)
		BOOTDIR="$2"
		if [ ! -d "${BOOTDIR}" ]; then
			echo "E: ${BOOTDIR} is not a directory." >&2
			exit 1
		fi
		shift 2
		;;
	-h|-\?|--help)
		usage
		exit 0
		;;
	--)
		shift
		break
		;;
	esac
done

if [ $# -ne 0 ]; then
	printf "Extra argument '%s'\\n\\n" "$1" >&2
	usage_error
fi

# Validate arguments
if [ -z "${mode}" ]; then
	usage_error "You must specify at least one of -c, -u, or -d."
fi

if [ "${version}" = "all" ] \
	|| { [ "${update_initramfs}" = "all" ] && [ -z "${version}" ]; }; then
	case "${mode}" in
	c)
		version_list="$(linux-version list)"
		;;
	d | u)
		get_sorted_versions
		;;
	esac
	if [ -z "${version_list}" ]; then
		verbose "Nothing to do, exiting."
		exit 0
	fi

	OPTS="-b ${BOOTDIR}"
	if [ "${verbose}" = "1" ]; then
		OPTS="${OPTS} -v"
	fi
	for u_version in ${version_list}; do
		verbose "Execute: ${0} -${mode} -k \"${u_version}\" ${OPTS}"
		# shellcheck disable=SC2086
		"${0}" -${mode} -k "${u_version}" ${OPTS}
	done
	exit 0
fi


case "${mode}" in
	c)
		create
		;;
	d)
		delete
		;;
	u)
		update
		;;
esac