eos-image-boot-setup

#!/bin/sh
# Copyright (C) 2016 Endless Mobile, Inc.
# Licensed under the GPLv2
#
# Support booting from an image file hosted on a filesystem.
# We identify which disk blocks correspond to the image file, and create
# a dm-linear block device mapping them.

type getarg >/dev/null 2>&1 || . /lib/dracut-lib.sh

host_device=$(cat /var/tmp/endless-image-host)
image_path=$(getarg endless.image.path)

blockdev --setro ${host_device}

if getargbool 0 endless.live_boot; then
  dm_roflag=--readonly
  kpartx_roflag=-r
fi

fstype=$(lsblk --noheadings -o FSTYPE "${host_device}")
if [ $? != 0 ]; then
  echo "image-boot: failed to detect filesystem type"
  exit 1
fi

# Identify the EOS image extents on the host device, and create a dm-linear
# block device that maps exactly to that.

case "${fstype}" in
exfat)
  extents=$(dumpexfat -f "${image_path}" "${host_device}")
  ;;
ntfs)
  extents=$(ntfsextents "${host_device}" "${image_path}")
  ;;
*)
  echo "image-boot: unsupported filesystem ${fstype}"
  exit 1
esac

if [ $? != 0 ]; then
  echo "image-boot: failed to lookup image on device"
  exit 1
fi

offset=0
echo "$extents" | while read extent_offset extent_size; do
  [ -z "${extent_offset}" -o -z "${extent_size}" ] && continue
  # Convert bytes to sectors, rounding up
  if [ $(( extent_size % 512 )) != 0 ]; then
    echo "image-boot: extent size $extent_size not sector-aligned" >&2
    exit 1
  fi
  extent_size=$(( extent_size / 512 ))
  extent_offset=$(( extent_offset / 512 ))
  echo "${offset} ${extent_size} linear ${host_device} $extent_offset"
  offset=$((offset + extent_size))
done > /tmp/dmtable

if [ $? != 0 ]; then
  exit 1
fi

dmsetup create endless-image $dm_roflag < /tmp/dmtable
if [ $? != 0 ]; then
  echo "image-boot: failed to set up linear mapping"
  exit 1
fi

if ! kpartx $kpartx_roflag -a -v /dev/mapper/endless-image; then
  echo "image-boot: failed to probe partitions"
  exit 1
fi

exit 0