Initramfs /init script for Linux hibernation/swsusp resume from encrypted swap partition

init

#!/bin/sh
# Discussion at https://community.frame.work/t/fw16-debian-bookworm-hibernate-not-reliable/52980/11?u=whitslack

mount --no-mtab -t devtmpfs dev /dev
mount --no-mtab -t proc proc /proc
mount --no-mtab -t sysfs sysfs /sys

loadkeys dvorak
echo 51 >/sys/class/backlight/amdgpu_bl0/brightness

read -r cmdline </proc/cmdline
for arg in ${cmdline} ; do
	case "${arg}" in
		root=*)
			root="${arg#*=}"
			;;
		rootflags=*)
			rootflags="${arg#*=}"
			;;
		rootfstype=*)
			rootfstype="${arg#*=}"
			;;
		ro)
			rw=ro
			;;
		rw)
			rw=rw
			;;
		data=*)
			data="${arg#*=}"
			;;
		swap=*)
			swap="${arg#*=}"
			;;
		init=*)
			init="${arg#*=}"
			;;
		single)
			set S
			;;
	esac
done

root="$(findfs "${root-PARTLABEL=Root}")"
data="$(findfs "${data-PARTLABEL=Data}")"
swap="$(findfs "${swap-PARTLABEL=Swap}")"

cryptsetup() {(
	read -r printk </proc/sys/kernel/printk
	echo 1 >/proc/sys/kernel/printk
	command cryptsetup "${@}" ; ret=$?
	printf '%s' "${printk}" >/proc/sys/kernel/printk
	return "${ret}"
)}

if [ -n "${data}" -a -n "${swap}" ] ; then
	until cryptsetup luksOpen --disable-locks --test-passphrase --link-vk-to-keyring @us::dmcrypt "${data}" ; do : ; done
	keyctl pipe %user:dmcrypt | cryptsetup open --type plain --cipher aes-xts-plain64 --key-size 512 --key-file - --sector-size 4096 --allow-discards "${swap}" swap
	stat --format='%Hr:%Lr' /dev/mapper/swap >/sys/power/resume
fi

mount --no-mtab ${rootfstype+-t "${rootfstype}"} -o "${rw:-ro}${rootflags:+,${rootflags}}" "${root:?}" /root
umount --no-mtab /sys /proc /dev
exec switch_root /root "${init:-/sbin/init}" "${@}"