#!/bin/bash

shopt -s nullglob


export LC_CTYPE=en_US.UTF-8
NAME=${DEVNAME#/dev/}
DESC="`echo "${ID_MODEL} (${ID_FS_LABEL})" | iconv -f utf8 -t ascii//TRANSLIT`"
SIZE=$[ $(cat /sys/$DEVPATH/size) * 512 ]
MODE=w
QDB_KEY="/qubes-block-devices/$NAME"

xs_remove() {
    if [ "$QUBES_EXPOSED" == "1" ]; then
        qubesdb-rm "$QDB_KEY/"
        qubesdb-write /qubes-block-devices ''
    fi
    echo QUBES_EXPOSED=0
}

is_used() {
    local sys_devpath=$1
    # mounted; or enabled swap
    if lsblk -dnr -o MOUNTPOINT "$DEVNAME" | grep -q .; then
        return 0
    fi
    # part of other device-mapper
    if [ -n "`ls -A $sys_devpath/holders 2> /dev/null`" ]; then
        return 0
    fi
    # open device-mapper device
    if [ -f "$sys_devpath/dm/name" ] && \
            /sbin/dmsetup info "$(cat $sys_devpath/dm/name)" |\
                grep -q "^Open count:.*[1-9]"; then
        return 0
    fi
    return 1
}

# communicate with xenstored through socket in dom0
# trying to access xenstore before xenstored is started, hang forever (in
# non-killable state), so better fail ('-s' in VM if /proc/xen isn't mounted
# yet) than hang dom0 boot
if [ ! -r /proc/xen/capabilities ] || grep -q control_d /proc/xen/capabilities; then
    XENSTORE_LS="xenstore-ls -s"
else
    XENSTORE_LS="xenstore-ls"
fi
is_attached() {
    dev_hex=$(stat -c %t:%T /dev/$(basename $1))
    $XENSTORE_LS backend/vbd | grep -q "physical-device = \"$dev_hex\""
}

# update info about parent devices, if any:
if [ -f /sys$DEVPATH/partition ]; then
    parent=$(dirname $(readlink -f /sys$DEVPATH))
    udevadm trigger \
        --property-match=DEVPATH=/$(realpath --relative-to=/sys $parent)
    # if parent device is already attached, skip its partitions
    if is_attached $parent; then
        xs_remove
        exit 0
    fi
fi

# and underlying devices of device-mapper (if any)
for dev in /sys$DEVPATH/slaves/*; do
    udevadm trigger \
        --property-match=DEVPATH=/$(realpath --relative-to=/sys $dev)
done

# then take care of this device:

# device itself is already used
if is_used /sys$DEVPATH; then
    xs_remove
    exit 0
fi

# or one of its partitions is used
# or already attached (prevent attaching both device and its partition(s) at
# the same time)
for part in /sys$DEVPATH/$NAME*; do
    if [ -d $part ]; then
        if is_used $part; then
            xs_remove
            exit 0
        fi
        if is_attached $part; then
            xs_remove
            exit 0
        fi
    fi
done

# or "empty" loop device
if [ "$MAJOR" -eq 7 -a ! -d /sys/$DEVPATH/loop ]; then
    xs_remove
    exit 0
fi

# ... and temporary devices used during VM startup
if [[ "$NAME" = 'loop'* ]] && \
       [[ "`cat /sys/block/${NAME%p*}/loop/backing_file`" = \
            '/var/lib/qubes/'*'/volatile.img' ]]; then
    xs_remove
    exit 0
fi

# Check if device is read-only
if [ "`cat /sys/$DEVPATH/ro`" -eq 1 ]; then
    MODE=r
fi

# Special case for CD
if [ "$ID_TYPE" = "cd" ]; then
    if [ "$ID_CDROM_MEDIA" != "1" ]; then
        # Hide empty cdrom drive
        xs_remove
        exit 0
    fi
    MODE=r
fi

# Special description for loop devices
if [ -d /sys/$DEVPATH/loop ]; then
    DESC=$(cat /sys/$DEVPATH/loop/backing_file)
fi
# and for device-mapper
if [ -n "$DM_NAME" ]; then
    DESC="$DM_NAME"
fi

# The last one is meant to trigger watches
qubesdb-write \
    "$QDB_KEY/desc" "$DESC" \
    "$QDB_KEY/size" "$SIZE" \
    "$QDB_KEY/mode" "$MODE" \
    /qubes-block-devices ''
echo QUBES_EXPOSED=1

# Make sure that block backend is loaded
/sbin/modprobe xen-blkback 2> /dev/null || /sbin/modprobe blkbk