#!/bin/sh -u
# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# A script to install from removable media to hard disk.

# If we're not running as root, restart as root.
if [ ${UID:-$(id -u)} -ne 0 ]; then
  exec sudo "$0" "$@"
fi

# Load functions and constants for chromeos-install.
. /usr/share/misc/chromeos-common.sh || exit 1
. /usr/share/misc/shflags || exit 1

# Helpful constants.
HARDWARE_DIAGNOSTICS_PATH=/tmp/hardware_diagnostics.log
TMPMNT=/tmp/install-mount-point
STATEFUL_PART=1
# This is defined later once we have mounted the ROOT.
STATEFUL_FORMAT=

# Partition numbers that have assumptions about them. This list should be kept
# to a minimal. Check copy_partition for most special casing.
KERNEL_A_PART=2
ROOTFS_A_PART=3
KERNEL_B_PART=4
ROOTFS_B_PART=5

# TODO(installer): Clean up all these flags. There are way too many flags in
# this script.

DEFINE_string dst "" "Destination device"
DEFINE_boolean skip_src_removable ${FLAGS_FALSE} \
  "Skip check to ensure source is removable"
DEFINE_boolean skip_dst_removable ${FLAGS_FALSE} \
  "Skip check to ensure destination is not removable"
DEFINE_boolean skip_rootfs ${FLAGS_FALSE} \
  "Skip installing the rootfs; Only set up partition table"
DEFINE_boolean yes ${FLAGS_FALSE} \
  "Answer yes to everything"
DEFINE_boolean preserve_stateful ${FLAGS_FALSE} \
  "Don't create a new filesystem for the stateful partition. Be careful \
using this option as this may make the stateful partition not mountable."
DEFINE_string arch "" \
  "Architecture for this image, must be one of 'ARM', 'MIPS', or 'INTEL'.  \
If unset, auto-detect."
DEFINE_string payload_image "" "Path to a Chromium OS image to install onto \
the device's hard drive"
DEFINE_string gpt_layout "" "Path to a script for pre-defined GPT partition \
layout"
DEFINE_string pmbr_code "" "Path to PMBR code to be installed"
DEFINE_string target_bios "" "Bios type to boot with (see postinst --bios)"
DEFINE_boolean mtd_layout ${FLAGS_FALSE} "This system uses MTD for \
partitioning rather than GPT"
DEFINE_boolean debug ${FLAGS_FALSE} "Show debug output"
DEFINE_boolean large_test_partitions ${FLAGS_FALSE} \
  "Make partitions 9 and 10 large (for filesystem testing)"
DEFINE_boolean skip_postinstall ${FLAGS_FALSE} \
  "Skip postinstall for situations where you're building for a \
non-native arch. Note that this will probably break verity."
DEFINE_string lab_preserve_logs "" "Path to a file containing logs to be \
preserved"


# Parse command line
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"

die() {
  echo "$*" >&2
  exit 1
}

# Determine our architecture
get_architecture() {
  if [ -n "${FLAGS_arch}" ]; then
    case ${FLAGS_arch} in
    INTEL|ARM|MIPS)
      echo "${FLAGS_arch}"
      return 0
      ;;
    *)
      die "Error: Unknown architecture '${FLAGS_arch}'."
    esac
  fi

  case $(uname -m) in
  i?86|x86_64)
    echo "INTEL"
    ;;
  arm*|aarch64)
    echo "ARM"
    ;;
  mips*)
    echo "MIPS"
    ;;
  *)
    die "Error: Failed to auto detect architecture."
  esac
  return 0
}

fast_dd() {
  # Usage: fast_dd <block size> <count> <seek> <skip> other dd args
  local user_block_size="$1"
  shift
  local user_count="$1"
  shift
  local user_seek="$1"
  shift
  local user_skip="$1"
  shift
  local ideal_block_size=$((2 * 1024 * 1024))  # 2 MiB
  if [ $(($ideal_block_size % $user_block_size)) -eq 0 ]; then
    local factor=$(($ideal_block_size / $user_block_size))
    if [ $(($user_count % $factor)) -eq 0 -a \
         $(($user_seek % $factor)) -eq 0 -a \
         $(($user_skip % $factor)) -eq 0 ]; then
      local count_arg=""
      if [ "$user_count" -ne 0 ]; then
        count_arg="count=$(($user_count / $factor))"
      fi
      dd $* bs="$ideal_block_size" seek=$(($user_seek / $factor)) \
          skip=$(($user_skip / $factor)) $count_arg
      return
    fi
  fi
  # Give up and do the user's slow dd
  echo
  echo WARNING: DOING A SLOW dd OPERATION. PLEASE FIX
  echo
  local count_arg=""
  if [ "$user_count" -ne 0 ]; then
    count_arg="count=$user_count"
  fi
  dd $* bs="$user_block_size" seek="$user_seek" skip="$user_skip" \
    $count_arg
}

# Get the specified env var for the specified partition.
#  $1 the field name such as "PARTITION_SIZE", "FS_FORMAT"
#  $2 the partition such as "1", or "ROOT_A"
_get_field() {
  local field part
  field="$1"
  part="$2"
  eval echo \""\${${field}_${part}}"\"
}

get_format() {
  _get_field FORMAT "$@"
}

get_fs_format() {
  _get_field FS_FORMAT "$@"
}

get_partition_size() {
  _get_field PARTITION_SIZE "$@"
}

get_reserved_ebs() {
  _get_field RESERVED_EBS "$@"
}

# Calculate the maximum number of bad blocks per 1024 blocks for UBI.
#  $1 partition number
calculate_max_beb_per_1024() {
  local part_no mtd_size eb_size nr_blocks
  part_no="$1"
  # The max beb per 1024 is on the total device size, not the partition size.
  mtd_size=$(cat /sys/class/mtd/mtd0/size)
  eb_size=$(cat /sys/class/mtd/mtd0/erasesize)
  nr_blocks=$((mtd_size / eb_size))
  reserved_ebs=$(get_reserved_ebs "${part_no}")
  echo $((reserved_ebs * 1024 / nr_blocks))
}

# Format and make UBI volume if it's not already there.
#  $1 partition number such as "1", "2"
#  $2 volume name
init_ubi_volume() {
  local part_no volume_name phy_ubi log_ubi
  part_no="$1"
  volume_name="$2"
  phy_ubi="/dev/ubi${part_no}"
  log_ubi="${phy_ubi}_0"
  if [ ! -e "${phy_ubi}" ]; then
    ubiformat -y -e 0 "/dev/mtd${part_no}"
    ubiattach -d "${part_no}" -m "${part_no}" \
              --max-beb-per1024 $(calculate_max_beb_per_1024 "${part_no}")
  fi
  if [ ! -e "${log_ubi}" ]; then
    local volume_size
    volume_size=$(get_partition_size "${part_no}")
    ubimkvol -s "${volume_size}" -N "${volume_name}" "${phy_ubi}"
  fi
}

# Update a specific partition in the destination device.
write_partition() {
  local user_part="$1"
  local user_count="$2"
  local user_seek="$3"
  local user_skip="$4"
  local src="$5"
  local dst="$6"
  local format fs_format

  if [ ${user_count} -eq 0 ]; then
    echo "Skipping partition as it does not exist"
    return 0
  fi

  format=$(get_format ${user_part})
  case ${format} in
  nand)
    flash_erase "/dev/mtd${user_part}" 0 0
    nandwrite --input-skip $((user_skip * 512)) \
      --input-size $((user_count * 512)) \
      "/dev/mtd${user_part}" "${src}"
    ;;

  ubi)
    local phy_ubi="/dev/ubi${user_part}"
    local log_ubi="${phy_ubi}_0"
    local sysfs_name="/sys/class/mtd/mtd${user_part}/name"

    init_ubi_volume "${user_part}" "$(cat "${sysfs_name}")"

    fs_format=$(get_fs_format ${user_part})
    case ${fs_format} in
    ubifs)
      local src_mnt="${TMPMNT}/src" dst_mnt="${TMPMNT}/dst"
      mkdir -p "${src_mnt}" "${dst_mnt}"

      mkfs.ubifs -y -x none -R 0 "${log_ubi}"
      mount "${log_ubi}" "${dst_mnt}"

      # Have to copy the files over by hand as the source partition is a
      # different filesystem type (like ext4).
      loop_offset_setup "${src}" "${user_seek}"
      TMPMNT="${src_mnt}" mount_on_loop_dev
      cp -a "${src_mnt}"/* "${dst_mnt}"/
      TMPMNT="${src_mnt}" umount_from_loop_dev
      loop_offset_cleanup

      umount "${log_ubi}"
      ;;
    *)
      ubiupdatevol --skip $((user_skip * 512)) --size $((user_count * 512)) \
        ${log_ubi} "${src}"
      ;;
    esac
    ;;

  *)
    fast_dd 512 "${user_count}" "${user_seek}" "${user_skip}" \
      if="${src}" of="${dst}" conv=notrunc
    ;;
  esac
}

# Find root partition of the block device that we are installing from
get_root_device() {
  rootdev -s
}

# Check for optional payload image
check_payload_image() {
  if [ "${FLAGS_skip_rootfs}" -eq "${FLAGS_TRUE}" -a \
       -s "${FLAGS_gpt_layout}" ]; then
    # Usually this is used for partition setup.
    SRC=""
    ROOT=""
  elif [ -z "${FLAGS_payload_image}" ]; then
    # Find root partition of the root block device
    SRC=$(get_block_dev_from_partition_dev $(get_root_device))
    ROOT=""

    if [ "${FLAGS_skip_src_removable}" -eq "${FLAGS_FALSE}" ]; then
      if [ "$(cat /sys/block/${SRC#/dev/}/removable)" != "1" ]; then
        # Work around ARM kernel bug http://crosbug.com/14871
        # Removable flag is implemented inconsistantly for ARM sdcard reader.
        if [ "${SRC}" != "/dev/mmcblk1" ]; then
          die "Error: Source does not look like a removable device: ${SRC}"
        fi
      fi
    fi
  else
    if [ ! -e "${FLAGS_payload_image}" ]; then
      die "Error: No payload image found at ${FLAGS_payload_image}"
    fi

    # Needed to copy PMBR code off image
    SRC="${FLAGS_payload_image}"
    ROOT="$(mktemp -d)"
  fi
}

# Clean any mounts that might be present to avoid
# aliasing access to block devices.
prepare_disk() {
  if [ -e /etc/init/cros-disks.conf ]; then
    initctl stop cros-disks || true
  fi
  # Often times, nothing is mounted, so swallow the warnings.
  umount -f /media/*/* 2>&1 | \
    grep -v -i \
      -e 'No such file or directory' \
      -e 'not found' || true
}

# Like mount but keeps track of the current mounts so that they can be cleaned
# up automatically.
tracked_mount() {
  local last_arg
  eval last_arg=\$$#
  MOUNTS="${last_arg}${MOUNTS:+ }${MOUNTS:-}"
  mount "$@"
}

# Unmount with tracking.
tracked_umount() {
  # dash doesnt support ${//} expansions
  local new_mounts
  for mount in $MOUNTS; do
    if [ "$mount" != "$1" ]; then
      new_mounts="${new_mounts:-}${new_mounts+ }$mount"
    fi
  done
  MOUNTS=${new_mounts:-}

  umount "$1"
}

# Create a loop device on the given file at a specified (sector) offset.
# Remember the loop device using the global variable LOOP_DEV.
# Invoke as: command
# Args: FILE OFFSET
loop_offset_setup() {
  local filename=$1
  local offset=$2

  LOOP_DEV=$(losetup -f --show -o $(($offset * 512)) ${filename})
  if [ -z "$LOOP_DEV" ]; then
    die "No free loop device. Free up a loop device or reboot. Exiting."
  fi

  LOOPS="${LOOP_DEV}${LOOPS:+ }${LOOPS:-}"
}

# Delete the current loop device.
loop_offset_cleanup() {
  # dash doesnt support ${//} expansions
  local new_loops
  for loop in $LOOPS; do
    if [ "$loop" != "$LOOP_DEV" ]; then
      new_loops="${new_loops:-}${new_loops+ }$loop"
    fi
  done
  LOOPS=${new_loops:-}

  # losetup -a doesn't always show every active device, so we'll always try to
  # delete what we think is the active one without checking first. Report
  # success no matter what.
  losetup -d ${LOOP_DEV} || /bin/true
}

# Mount the existing loop device at the mountpoint in $TMPMNT.
# Args: optional 'readwrite'. If present, mount read-write, otherwise read-only.
mount_on_loop_dev() {
  local rw_flag=${1-readonly}
  local mount_flags=""
  if [ "${rw_flag}" != "readwrite" ]; then
    mount_flags="-o ro"
  fi
  tracked_mount ${mount_flags} ${LOOP_DEV} ${TMPMNT}
}

# Unmount loop-mounted device.
umount_from_loop_dev() {
  mount | grep -q " on ${TMPMNT} " && tracked_umount ${TMPMNT}
}

# Check if all arguments are non-empty values
check_non_empty_values() {
  local value
  for value in "$@"; do
    if [ -z "$value" ]; then
      return ${FLAGS_FALSE}
    fi
  done
  return ${FLAGS_TRUE}
}

# Undo all mounts and loops and runs hw diagnostics on failure.
cleanup_on_failure() {
  set +e

  if [ -b "${DST}" ]; then
    # Generate the diagnostics log that can be used by a caller.
    echo "Running a hw diagnostics test -- this might take a couple minutes."
    badblocks -sv "${DST}" 2>&1 | tee "${HARDWARE_DIAGNOSTICS_PATH}"

    # Run a few extra diagnostics and then them to stdout. These will be stored
    # as part of the recovery.log for recovery images.
    if which smartctl >/dev/null 2>&1; then
      smartctl -l error "${DST}"
      smartctl -l selftest "${DST}"
      smartctl -a "${DST}"
    fi
  fi

  cleanup
}

# Undo all mounts and loops.
cleanup() {
  set +e

  local mount_point
  for mount_point in ${MOUNTS:-}; do
    umount "$mount_point" || /bin/true
  done
  MOUNTS=""

  local loop_dev
  for loop_dev in ${LOOPS:-}; do
    losetup -d "$loop_dev" || /bin/true
  done
  LOOPS=""

  if [ ! -z "$ROOT" ]; then
    rmdir "$ROOT"
  fi
}

check_removable() {
  if [ ${FLAGS_skip_dst_removable} -eq ${FLAGS_TRUE} ]; then
    return
  fi

  local removable

  if ! removable=$(cat /sys/block/${DST#/dev/}/removable); then
    die "Error: Invalid destination device (must be whole device): ${DST}"
  fi

  if [ "${removable}" != "0" ]; then
    die "Error: Attempt to install to a removeable device: ${DST}"
  fi
}

# Wipes and expands the stateful partition.
wipe_stateful() {
  echo "Clearing the stateful partition..."
  local stateful_fs_format=$(get_fs_format ${STATEFUL_PART})

  case ${STATEFUL_FORMAT} in
  ubi)
    local phy_ubi="/dev/ubi${STATEFUL_PART}"
    local log_ubi="${phy_ubi}_0"
    local sysfs_name="/sys/class/mtd/mtd${STATEFUL_PART}/name"

    init_ubi_volume "${STATEFUL_PART}" "$(cat "${sysfs_name}")"
    ;;
  *)
    loop_offset_setup ${DST} ${START_STATEFUL}
    ;;
  esac

  # We always make any ext* stateful partitions ext4.
  case ${stateful_fs_format} in
  ext[234])
    mkfs.ext4 -F -b 4096 -L "H-STATE" ${LOOP_DEV} \
      $((NUM_STATEFUL_SECTORS / 8))
    ;;
  ubifs)
    mkfs.ubifs -y -x none -R 0 /dev/ubi${STATEFUL_PART}_0
    ;;
  esac

  case ${STATEFUL_FORMAT} in
  ubi) ;;
  *)
    # Need to synchronize before releasing loop device, otherwise calling
    # loop_offset_cleanup may return "device busy" error.
    sync
    loop_offset_cleanup
    ;;
  esac
}

# Install the stateful partition content
# Method handles copying data over to the stateful partition. This is done
# differently than other partitions due to the EXPAND option i.e. src partition
# and dst partitions are of different sizes. In addition, there are some special
# tweaks we do for stateful here for various workflows.
install_stateful() {
  # In general, the system isn't allowed to depend on anything
  # being in the stateful partition at startup.  We make some
  # exceptions for dev images (only), as enumerated below:
  #
  # var_overlay
  #   These are included to support gmerge, and must be kept in
  #   sync with those listed in /etc/init/var-overlay.conf:
  #      db/pkg
  #      lib/portage
  #
  # dev_image
  #   This provides tools specifically chosen to be mounted at
  #   /usr/local as development only tools.
  #
  # Every exception added makes the dev image different from
  # the release image, which could mask bugs.  Make sure every
  # item you add here is well justified.
  echo "Installing the stateful partition..."
  case ${STATEFUL_FORMAT} in
  ubi)
    # We modify the global used here as it affects how we unmount later.
    LOOP_DEV="/dev/ubi${STATEFUL_PART}_0"
    ;;
  *)
    loop_offset_setup ${DST} ${START_STATEFUL}
    ;;
  esac
  mount_on_loop_dev readwrite

  # Move log files listed in FLAGS_lab_preserve_logs from stateful_partition to
  # a dedicated location. This flag is used to enable Autotest to collect log
  # files before reimage deleting all prior logs.
  if crossystem 'cros_debug?1' && [ -n "${FLAGS_lab_preserve_logs}" ]; then
    local gatherme="${TMPMNT}/.gatherme"
    touch "${gatherme}"
    local prior_log_dir="${TMPMNT}/unencrypted/prior_logs"
    mkdir -p "${prior_log_dir}"
    local log_path
    for log_path in $(sed -e '/^#/ d' -e '/^$/ d' "${FLAGS_lab_preserve_logs}"); do
      case "${log_path}" in
        /dev/* | /sys/*)
          ;;
        /*)
          echo "${log_path}" >> "${gatherme}"
          continue
          ;;
        *)
          log_path="${TMPMNT}/${log_path}"
          ;;
      esac
      if [ -d "${log_path}" ]; then
        cp -au -r --parents "${log_path}" "${prior_log_dir}" || true
      elif [ -f "${log_path}" ]; then
        cp -au "${log_path}" "${prior_log_dir}" || true
      fi
    done
  fi

  # Whitelist files to copy onto the stateful partition.
  #
  # When adding to the whitelist, consider the need for related changes in
  # src/platform/init/chromeos_startup, and in src/platform/dev/stateful_update.
  #
  local dirlist="unencrypted/import_extensions"
  if crossystem 'cros_debug?1'; then
    dirlist="
      ${dirlist}
      var_overlay/db/pkg
      var_overlay/lib/portage
      dev_image
    "
  fi

  if crossystem 'devsw_boot?1' ; then
    # This is a base build, and the dev switch was on when we booted;
    # we assume it will be on for the next boot.  We touch
    # ".developer_mode" to avoid a pointless delay after reboot while
    # chromeos_startup wipes an empty stateful partition.
    #
    # See chromeos_startup for the companion code that checks for this
    # file.
    #
    touch ${TMPMNT}/.developer_mode
  fi

  local dir
  for dir in ${dirlist}; do
    if [ ! -d "${ROOT}/mnt/stateful_partition/${dir}" ]; then
      continue
    fi
    local parent=$(dirname "${dir}")
    mkdir -p "${TMPMNT}/${parent}"
    cp -au "${ROOT}/mnt/stateful_partition/${dir}" "${TMPMNT}/${dir}"
  done

  umount_from_loop_dev
  case ${STATEFUL_FORMAT} in
  ubi) ;;
  *)
    loop_offset_cleanup
    ;;
  esac
}

# Copy partition from src to dst (figures out partition offsets). Note, this
# has some special casing for rootfs, kernel, and stateful partitions. In
# addition, it only copies partitions that are equally sized over one another.
# $1 - Partition number we are copying to.
# $2 - src image
# $3 - dst image.
copy_partition() {
  local part_num=$1
  local src=$2
  local dst=$3
  local part_size=$(partsize ${src} ${part_num})
  local src_offset=$(partoffset ${src} ${part_num})
  local dst_offset=$(partoffset ${dst} ${part_num})

  echo "Installing partition ${part_num} to ${dst}"

  case ${part_num} in
  ${STATEFUL_PART})
    install_stateful
    ;;
  ${ROOTFS_A_PART}|${ROOTFS_B_PART})
    # Always copy from ROOT_A for rootfs partitions.
    part_size=$(partsize ${src} ${ROOTFS_A_PART})
    src_offset=$(partoffset ${src} ${ROOTFS_A_PART})
    write_partition ${part_num} ${part_size} ${dst_offset} \
      ${src_offset} ${src} ${dst}
    ;;
  ${KERNEL_A_PART}|${KERNEL_B_PART})
    # Use kernel B from the source into both kernel A and B in the destination.
    part_size=$(partsize ${src} ${KERNEL_B_PART})
    src_offset=$(partoffset ${src} ${KERNEL_B_PART})
    write_partition ${part_num} ${part_size} ${dst_offset} \
      ${src_offset} ${src} ${dst}
    ;;
  *)
    local dst_part_size=$(partsize ${dst} ${part_num})
    if [ ${part_size} -ne ${dst_part_size} -o ${part_size} -le 4096 ]; then
      # We only copy partitions that are equally sized and greater than the
      # min fs block size. This matches the build_image logic.
      return
    fi
    write_partition ${part_num} ${part_size} ${dst_offset} \
      ${src_offset} ${src} ${dst}
    ;;
  esac
}

# Remove partitions 1 to 12 from MTD device. Recreate partitions 1 to 12 with
# information from the current GPT table.
# $1 is the device node, such as "/dev/mtd0"
recreate_nand_partitions() {
  local dst=$1
  local part_no
  for part_no in $(ls /dev | grep 'mtd[0-9]*$' | grep -v mtd0 | cut -c 4-); do
    # Ignore any error in case no UBI volume is attached.
    ubidetach -m "${part_no}" 2>&1 > /dev/null || true
    nand_partition del "${dst}" "${part_no}"
  done

  local gpt_file mtd_size mtd_gpt_file part_size part_offset
  gpt_file=$(mktemp)
  flashrom -r "-iRW_GPT:${gpt_file}"
  mtd_size=$(cat "/sys/class/mtd/$(basename "${dst}")/size")
  mtd_gpt_file="-D ${mtd_size} ${gpt_file}"
  for part_no in $(seq 12); do
    part_size=$(partsize "${mtd_gpt_file}" "${part_no}")
    : $(( part_size *= 512 ))
    part_offset=$(partoffset "${mtd_gpt_file}" "${part_no}")
    : $(( part_offset *= 512 ))
    nand_partition add "${dst}" "${part_no}" \
      "${part_offset}" "${part_size}"
  done
  rm -f "${gpt_file}"
}

# Find our destination device.
# If the user hasn't selected a destination,
# we expect that the disk layout declares it for us.
check_dst() {
  if [ -z "${DST}" ]; then
    die "Error: can not determine destination device. Specify --dst yourself."
  fi

  if [ "${DST}" = "/dev/mtd0" ]; then
    FLAGS_mtd_layout=${FLAGS_TRUE}
  fi

  # Check out the dst device.
  if [ ${FLAGS_mtd_layout} -eq ${FLAGS_TRUE} ]; then
    FLAGS_skip_dst_removable=${FLAGS_TRUE}
  elif [ ! -b "${DST}" ]; then
    die "Error: Unable to find destination block device: ${DST}"
  fi

  if [ "${DST}" = "${SRC}" ]; then
    die "Error: src and dst are the same: ${SRC} = ${DST}"
  fi
}

# Gets the right PMBR (protective master boot record) code (either from
# FLAGS_pmbr_code, source or destination media) by printing the file path
# containing PMBR code in standard out.
get_pmbr_code() {
  local pmbr_code="/tmp/gptmbr.bin"

  if [ -n "${FLAGS_pmbr_code}" ]; then
    echo "${FLAGS_pmbr_code}"
  elif [ ${FLAGS_mtd_layout} -eq ${FLAGS_TRUE} ]; then
    # We don't use PMBR if this is on MTD.
    dd bs=512 count=1 if=/dev/zero of="${pmbr_code}" >/dev/null 2>&1
    echo "${pmbr_code}"
  elif [ "${ARCH}" = "ARM" ]; then
    # Store the existing PMBR from the destination in the temp pmbr file so we
    # can restore it when we're installing the GPT. This ensures that we
    # preserve settings set by crossystem (such as dev_boot_usb).
    dd bs=512 count=1 if="${DST}" of="${pmbr_code}" >/dev/null 2>&1
    echo "${pmbr_code}"
  else
    # Steal the PMBR code from the source MBR to put on the dest MBR, for
    # booting on legacy-BIOS devices.
    dd bs=512 count=1 if="${SRC}" of="${pmbr_code}" >/dev/null 2>&1
    echo "${pmbr_code}"
  fi
}

# Reload the system partitions after the partition table was modified (so the
# device nodes like /dev/sda1 can be accessed).
reload_partitions() {
  if [ ${FLAGS_mtd_layout} -eq ${FLAGS_FALSE} ]; then
    # Reload the partition table on block devices only.
    # On MTD, the ChromeOS kernel loads the partition table at boot time.
    #
    # In some cases, we may be racing with udev for access to the
    # device leading to EBUSY when we reread the partition table.  We
    # avoid the conflict by using `udevadm settle`, so that udev goes
    # first.  cf. crbug.com/343681.
    udevadm settle
    /sbin/blockdev --rereadpt "${DST}"
  else
    # On NAND, we need to recreate the partition table.
    recreate_nand_partitions "${DST}"
  fi
}

# Post partition copying work and special casing
do_post_install() {
  local args=""
  if [ -n "${FLAGS_target_bios}" ]; then
    args="${args} --bios ${FLAGS_target_bios}"
  fi
  if [ "${FLAGS_debug}" -eq "${FLAGS_TRUE}" ]; then
    args="${args} --debug"
  fi
  local dst_rootfs_dev=""

  # Now run the postinstall script on one new rootfs. Note that even though
  # we're passing the new destination partition number as an arg, the postinst
  # script had better not try to access it, for the reasons we just gave.
  # We can't run this if the target arch isn't the same as the host arch
  if [ "${FLAGS_skip_postinstall}" -eq "${FLAGS_FALSE}" ]; then
    if [ ${FLAGS_mtd_layout} -eq ${FLAGS_TRUE} ]; then
      if ! [ -b "/dev/ubiblock${ROOTFS_A_PART}_0" ]; then
        ubiblock -c "/dev/ubi${ROOTFS_A_PART}_0"
      fi
      LOOP_DEV="/dev/ubiblock${ROOTFS_A_PART}_0"
      # We need to pass the __writable__ device to postinst, hence ubiX_0.
      dst_rootfs_dev="/dev/ubi${ROOTFS_A_PART}_0"
    else
      loop_offset_setup ${DST} ${START_ROOTFS_A}
      dst_rootfs_dev=$(make_partition_dev ${DST} ${ROOTFS_A_PART})
    fi

    mount_on_loop_dev
    IS_INSTALL="1" ${TMPMNT}/postinst "${dst_rootfs_dev}" ${args}
    umount_from_loop_dev
    if [ ${FLAGS_mtd_layout} -eq ${FLAGS_FALSE} ]; then
      loop_offset_cleanup
    fi
  fi
}

main() {
  # Be aggressive.
  set -eu
  if [ "${FLAGS_debug}" = "${FLAGS_TRUE}" ]; then
    set -x
  fi

  ARCH="$(get_architecture)" || exit $?

  check_payload_image
  mkdir -p "${TMPMNT}"

  # We untrap on success and run cleanup ourselves. Othewise, on any failure, run
  # our custom trap method to gather any diagnostic data before cleaning up.
  trap cleanup_on_failure EXIT

  # Clean media browser mounts if they've popped up.
  prepare_disk
  locate_gpt

  # Special handling for payload_image. This is passed in for recovery images
  # and usb installs. This is done first so we can read the gpt partition
  # file below.
  if [ -n "${FLAGS_payload_image}" ]; then
    SRC="${FLAGS_payload_image}"
    # Mount files that are required to be referenced (when not already mounted).
    loop_offset_setup "${SRC}" $(partoffset "${SRC}" ${ROOTFS_A_PART})
    tracked_mount -o ro "${LOOP_DEV}" "${ROOT}"
    loop_offset_setup "${SRC}" $(partoffset "${SRC}" ${STATEFUL_PART})
    tracked_mount -o ro "${LOOP_DEV}" "${ROOT}"/mnt/stateful_partition
  fi

  # Load the GPT helper functions and the image settings.
  . "${ROOT}/usr/sbin/write_gpt.sh"
  load_base_vars

  # Now that we have loaded the partition table we can actually read the format
  # and partition information.
  STATEFUL_FORMAT=$(get_format ${STATEFUL_PART})

  DST=${FLAGS_dst:-$(get_fixed_dst_drive)}
  check_dst
  check_removable

  # Ask for confirmation to be sure.
  echo "This will install from '${SRC}' to '${DST}'."
  echo "This will erase all data at this destination: ${DST}"
  local sure
  if [ ${FLAGS_yes} -eq ${FLAGS_FALSE} ]; then
    read -p "Are you sure (y/N)? " sure
    if [ "${sure}" != "y" ]; then
      # Don't run diagnostics if the user explictly bailed out.
      trap - EXIT
      cleanup
      die "Ok, better safe than sorry; you answered '${sure}'."
    fi
  fi

  # Write the GPT using the board specific script. The parameters are ignored
  # on MTD devices.
  write_base_table "${DST}" "$(get_pmbr_code)"
  legacy_offset_size_export "${DST}"
  reload_partitions

  if [ ${FLAGS_skip_rootfs} -eq ${FLAGS_TRUE} ]; then
    echo Done installing partitons.
    exit 0
  fi

  if [ ${FLAGS_preserve_stateful} -eq ${FLAGS_FALSE} -a \
       ! -n "${FLAGS_lab_preserve_logs}" ]; then
    wipe_stateful
  fi

  # Install the content. Do so in reverse order to have stateful get installed
  # last. The order shouldn't matter but legacy behavior has us go in reverse
  # order.
  local current_part
  for current_part in $(seq 12 -1 1); do
    copy_partition ${current_part} ${SRC} ${DST}
  done

  do_post_install

  # Force data to disk before we declare done.
  sync
  cleanup
  trap - EXIT

  echo "------------------------------------------------------------"
  echo ""
  echo "Installation to '${DST}' complete."
  echo "Please shutdown, remove the USB device, cross your fingers, and reboot."
}

main "$@"