1#!/bin/sh
2
3# Get the value of the root env variable found in /proc/cmdline
4get_root() {
5    local root="$(cat /proc/cmdline)"
6    root="${root##* root=PARTLABEL=}"
7    root="${root%% *}"
8    [ "${root}" != "" ] && echo "${root}"
9}
10
11fslist="proc sys dev run"
12rodir=/mnt/rofs
13cd /
14mkdir -p $fslist
15mount dev dev -tdevtmpfs
16mount sys sys -tsysfs
17mount proc proc -tproc
18mount tmpfs run -t tmpfs -o mode=755,nodev
19
20# Wait up to 5s for the mmc device to appear. Continue even if the count is
21# exceeded. A failure will be caught later like in the mount command.
22mmcdev="/dev/mmcblk0"
23count=0
24while [ $count -lt 5 ]; do
25    if [ -e "${mmcdev}" ]; then
26        break
27    fi
28    sleep 1
29    count=$((count + 1))
30done
31
32# Move the secondary GPT to the end of the device if needed. Look for the GPT
33# header signature "EFI PART" located 512 bytes from the end of the device.
34if ! tail -c 512 "${mmcdev}" | hexdump -C -n 8 | grep -q "EFI PART"; then
35    sgdisk -e "${mmcdev}"
36    partprobe
37fi
38
39# There eMMC GPT labels for the rootfs are rofs-a and rofs-b, and the label for
40# the read-write partition is rwfs. Run udev to make the partition labels show
41# up. Mounting by label allows for partition numbers to change if needed.
42udevd --daemon
43udevadm trigger --type=devices --action=add
44udevadm settle --timeout=10
45
46mkdir -p $rodir
47if ! mount /dev/disk/by-partlabel/"$(get_root)" $rodir -t ext4 -o ro; then
48    /bin/sh
49fi
50
51rwfsdev="/dev/disk/by-partlabel/rwfs"
52fsck.ext4 -p "${rwfsdev}"
53if ! mount "${rwfsdev}" $rodir/var -t ext4 -o rw; then
54    /bin/sh
55fi
56
57rm -rf $rodir/var/persist/etc-work/
58mkdir -p $rodir/var/persist/etc $rodir/var/persist/etc-work $rodir/var/persist/home/root
59mount overlay $rodir/etc -t overlay -o lowerdir=$rodir/etc,upperdir=$rodir/var/persist/etc,workdir=$rodir/var/persist/etc-work
60
61for f in $fslist; do
62    mount --move $f $rodir/$f
63done
64
65exec switch_root $rodir /sbin/init
66