#!/bin/bash
# Command to erase user data file system
# Modified for ubifs, secure boot (no U-Boot access)

MNT_USER="/mnt/user"
OVERLAY="$MNT_USER/overlay"
WORKDIR="$MNT_USER/work"
UPPERDIR="$MNT_USER/upper"
LOWERDIR="/"
USER_ORIG="$UPPERDIR/orig"
USER_PARTITION="ubi0:user-data"
# Erase the file system
DO_ERASE_PERSISTENT=$(fw_printenv erase_persistent_f | cut -d '"' -f2 | grep -Eo '[0-9]+$' || true)
# Remove files not hidden
DO_ERASE_ALL_EXCEPT_PERSISTENT=$(fw_printenv default_reset_f | cut -d '"' -f2 | grep -Eo '[0-9]+$' || true)

pid=$$
prefix="<3>overlayrootfs-generator[${pid}]: "
loginfo()  { echo "${prefix}$@" >/dev/kmsg ; }
logpipe() {
   OIFS="${IFS}"
   IFS=$'\n'
   while read ln ; do
        echo -n "${prefix}${ln}" >/dev/kmsg
   done
   IFS="${OIFS}"
}

mnt_user() {
    mkdir -p $MNT_USER
    mount -t ubifs $USER_PARTITION $MNT_USER
}

fs="/run /dev /proc /sys /sys/kernel/security /dev/shm /dev/pts /sys/fs/cgroup /sys/fs/cgroup/unified
 /sys/fs/cgroup/systemd /sys/fs/cgroup/devices /sys/fs/cgroup/freezer /sys/fs/cgroup/pids /sys/fs/cgroup/memory
 /dev/mqueue /sys/kernel/debug /tmp /sys/fs/fuse/connections /sys/kernel/config /var/volatile"

my_switch_root() {
    NEW_ROOT=$1
    loginfo mountinfo
    mount --make-rprivate /
    loginfo "my_switch_root: Mount file systems"
    for f in $fs ; do
        if [[ -d $NEW_ROOT/$f ]] ; then
            loginfo "my_switch_root: mount -o noatime,move --bind $f $NEW_ROOT/$f"
            mount -o noatime,move --bind "$f" "$NEW_ROOT/$f"
        else
            # loginfo "my_switch_root: Skipping $NEW_ROOT/$f"
            :
        fi
    done
    /sbin/pivot_root "$NEW_ROOT" "$NEW_ROOT"/orig
}

do_erase_all_except_persistent() {
    # Delete all files and folders except for the "${MNT_USER}/.persistent" directory.
    loginfo "Clearing user data. Persistent data will be left "
    rm -rf "${MNT_USER:?}/"*
}

# Most efficient way to clear UBIFS file system
do_erase_persistent() {
    loginfo "Erasing user data"
    # Sys must be mounted to use ubifs utilities
    mount -t sysfs sysfs /sys

    ubiattach -m 1 >/dev/null 2>&1 || true
    ubinfo -d 0 -N user-data | logpipe
    [[ $(ubinfo -d 0 -N user-data | grep 'Volume ID') =~ .*[[:space:]]+([0-9]+) ]]
    DEV=/dev/ubi0_"${BASH_REMATCH[1]}"
    umount -l $MNT_USER
    loginfo "Erase user-data partition $DEV"
    # Would be nice if ubiupdatevol took volume names instead of numbers
    ubiupdatevol "${DEV}" -t 2>&1 | logpipe

    mnt_user
}

do_rw_mount() {
    loginfo "Starting RW overlayfs"
    mount -t tmpfs inittemp /mnt

    mnt_user # user_data is now accessible
    if [[ "$DO_ERASE_PERSISTENT" -eq 1 ]] ; then
        do_erase_persistent
        fw_setenv erase_persistent_f 0
        fw_setenv default_reset_f 0
    elif [[ "$DO_ERASE_ALL_EXCEPT_PERSISTENT" -eq 1 ]] ; then
        do_erase_all_except_persistent
        fw_setenv default_reset_f 0
    fi

    mkdir -p $UPPERDIR $WORKDIR $OVERLAY $USER_ORIG ${MNT_USER}/.persistent
    loginfo "Mounting..."
    mount -o noatime,lowerdir=$LOWERDIR,upperdir=$UPPERDIR,workdir=$WORKDIR,rw -t overlay overlay $OVERLAY
    loginfo "/proc/mounts:"
    cat /proc/mounts | grep overlay | logpipe

    mkdir -p ${OVERLAY}/var/persistent

    mount --bind ${MNT_USER}/.persistent ${OVERLAY}/var/persistent
    loginfo "Switch root to $OVERLAY"
    my_switch_root $OVERLAY
    cat /proc/mounts | grep overlay | logpipe
    mount -o remount,rw /
    cat /proc/mounts | grep overlay | logpipe
    cat /proc/mounts | grep tmp | logpipe
    umount -l /tmp >/dev/null 2>&1
    umount -l /var/volatile >/dev/null 2>&1
    cgroupmnts=$(sed -r -e 's/[^[:space:]]*[[:space:]]//'  -e 's/[[:space:]]+.*//g' /proc/mounts | grep '^/orig')
    for mp in ${cgroupmnts} ; do
        if [[ $mp != /orig ]] && [[ $mp != /orig/mnt* ]] && [[ -d $mp ]] ; then
            umount -l "$mp" >/dev/null 2>&1
        fi
    done
}

do_start() {
    do_rw_mount
}

case $1 in
start)
    do_start
;;
*)
    echo "Usage: $0 {start}"
;;
esac