mount_root-mod

#!/bin/sh

ubi_num=

find_mtd_part() {
	local PART=$(awk -F: "/$1/{print \$1}" /proc/mtd)

	if [ ! -z "$PART" ]; then
		PART="${PART##mtd}"
		if [ ! -z "$PART" ]; then
			echo /dev/mtdblock$PART
		fi
	fi
}

#Since Linux 3.18-rc6, overlayfs has been renamed overlay
legacy_overlayfs() {
	local ovl
	ovl=$(cat /proc/filesystems | grep "\overlay\b" | awk '{print $2}')
	[ "$ovl" != "overlay" ]
}

find_mount_jffs2() {
	local options
	local mtdpartname
	local mtdpart
	local dir="$1"

	options=$(grep "^mount=" /etc/jffs2_options 2>/dev/null | sed "s/^mount=//" )
	if [ ! -z $options ]; then
		options="-o $options"
	fi

	mkdir -p "$dir"

	for mtdpartname in $(cat /proc/banktable/notbooted); do
		mtdpart="$(find_mtd_part $mtdpartname)"
		if [ -n "$mtdpart" ]; then
			mount -t jffs2 $options "$mtdpart" "$dir"
			if [ $? -ne 0 ]; then
				echo "failed to mount $mtdpartname on $mtdpart as jffs2"
				echo "retrying... by erasing and remounting"
				mtd erase $mtdpartname
				mount -t jffs2 $options "$mtdpart" "$dir"
				if [ $? -ne 0 ]; then
					echo "failed to mount $mtdpartname on $mtdpart as jffs2"
				else
					mtd -qq unlock $mtdpartname
					if [ $? -ne 0 ]; then
						echo "failed to unlock $mtdpartname, partition not writeable"
						umount "$dir"
					else
						if ! legacy_overlayfs; then
							mkdir -p "$dir/work"
						fi
						return 0
					fi
				fi
			else
				mtd -qq unlock $mtdpartname
				if [ $? -ne 0 ]; then
					echo "failed to unlock $mtdpartname, partition not writeable"
					umount "$dir"
				else
					if ! legacy_overlayfs; then
						mkdir -p "$dir/work"
					fi
					return 0
				fi
			fi
		fi
	done

	echo "failed to find suitable partition to mount"
	return 1
}

find_available_ubi_num() {
	local lastubidevice=
	for x in $(ubinfo | grep "Present UBI devices" | cut -d':' -f2 | tr "," "\n")
	do
		lastubidevice=$x
	done

	if [ -z "$lastubidevice" ]
	then
		lastubidevice=ubi0
	fi

	last_num=$(echo $lastubidevice | sed 's/ubi//')
	avail_dev_num=`expr $last_num + 1`
	echo $avail_dev_num
}

find_overlay_partition() {
        local result=$1
        overlay_partition="$(cat /proc/banktable/notbooted)"
        for partition in $overlay_partition ; do
                if ( cat /proc/mtd | grep -i $partition ) ; then
			eval $result="'$partition'"
			break
                fi
        done
}

get_ubi_num_from_vol() {
	volname=$1
	dev_count=$(ubinfo | grep "Count" |  tr -dc '0-9')
	for i in `seq 0 $(expr $dev_count - 1)`
	do
		ubi_count=$(ubinfo -d $i| grep "Volumes count" |  tr -dc '0-9')
		for j in `seq 0 $(expr $ubi_count - 1)`
		do
			ubivol=$(ubinfo -d $i -n $j |grep $volname)
			if [ ! -z "$ubivol" ] ; then
				ubi_num=$i
				break;
			fi
		done
	done


}

find_mount_ubifs() {
	local dir=$1

	find_overlay_partition partition

	get_ubi_num_from_vol $partition


	if [ ! -z  "$ubi_num" ] ; then
		echo "ubi_num=$ubi_num"

	elif ( cat /proc/mtd | grep -i "$partition" ) ; then
		mtd_block_number=$(cat /proc/mtd | grep -i "$partition" | sed 's/^mtd//' | awk -F ':' '{print $1}')

		echo "Detected block device: $dir for $partition" > /dev/kmsg
		ubi_num="$(find_available_ubi_num)"
		ubiattach -m "$mtd_block_number" -d $ubi_num /dev/ubi_ctrl

	else
		echo "No $partition partition found"
		return 1
	fi

	mkdir -p "$dir"

	mount -o sync -t ubifs ubi$ubi_num:overlay $dir
	if [ $? -ne 0 ]; then
		echo "failed to mount ubi$ubi_num:overlay on ubifs"
		return 1
	fi

	mkdir -p $dir/work
	return 0
}

pivot() { # <new_root> <old_root>
	local new=$1
	local old=$2
	mount -o move /proc $new/proc && \
	pivot_root $new $new$old && {
		mount -o move $old/dev /dev
		mount -o move $old/tmp /tmp
		mount -o move $old/sys /sys 2>&-
		mount -o move $old/overlay /overlay 2>&-
	}
}

fopivot() { # <rw_root> <ro_root>
	local rw_root=$1
	local ro_root=$2
	ovl=$(cat /proc/filesystems | grep "\overlay\b" | awk '{print $2}')
	if [ "$ovl" = "overlay" ]	#Since Linux 3.18-rc6, overlayfs has been renamed overlay
	then
		echo "mounting overlay fs"
		mount -t overlay -o lowerdir=/,upperdir=/overlay/1,workdir=/overlay/0 overlay /mnt && rw_root=/mnt
	else
		echo "mounting overlayfs fs"
		mount -t overlayfs -olowerdir=/,upperdir=$rw_root "overlayfs:$rw_root" /mnt && rw_root=/mnt
	fi
	pivot $rw_root $ro_root
}

check_banktable() {
	if [ -f /lib/modules/$(uname -r)/bankmgr.ko ]; then
		insmod bankmgr 2>/dev/null
	fi
}

run_mount_checks() {
	local mount_point="$1"
	local checkdir=/lib/mount_modroot_checks
	if [ ! -d "$checkdir" ]; then
		return
	fi
	local loop_detect="${mount_point}/mount_check_reboot"
	if [ -f "$loop_detect" ]; then
		#reboot because of mount check failures
		#do not check again, to prevent reboot loops
		rm $loop_detect
		return
	fi
	local reboot_needed="no"
	for check in $(ls -lA $checkdir); do
		if [ -x $checkdir/$check ]; then
			$checkdir/$check "$mount_point" || reboot_needed="yes"
		fi
	done
	if [ "$reboot_needed" = "yes" ]; then
		touch $loop_detect
		/sbin/reboot -f
	fi
}

mount_root_mod() {
	local upperdir
	local mount_point="/tmp/modoverlay"

	check_banktable
	if [ -f /proc/banktable/booted ]; then
		upperdir=/modoverlay
	else
		# modroot on notbooted bank not possible
		return
	fi

	find_mount_jffs2 ${mount_point}
	if [ $? -ne 0 ]; then
		find_mount_ubifs ${mount_point}
		if [ $? -ne 0 ]; then
			# something went wrong
			return
		fi
	fi

	run_mount_checks ${mount_point}

	mkdir -p $upperdir

	echo "switching to modoverlay"
	mount -o move /tmp/modoverlay /modoverlay 2>&-

	for f in /lib/mount_modroot/*; do
		[ -x $f ] && $f $upperdir
	done

	# mkdir -p $oldroot
	fopivot $upperdir /rom

	# make sure /tmp has the correct permissions !
	chmod 01777 /tmp
}

# Actually mount the dir
mount_root_mod

# Create needed dir
mkdir /saferoot
mkdir /modoverlay

# Move oldroot to saferoot
mount -o move /rom /saferoot

# Move old mount to new position
mount -o move /saferoot/modoverlay /modoverlay

# Restore original rom
mount -o move /saferoot/rom /rom

# Restore saferoot overlay
mount -o move /saferoot/overlay /overlay