flatcar-scripts/lib/cros_image_common.sh

#!/bin/bash

# Copyright (c) 2009 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.

# This script contains common utility function to deal with disk images,
# especially for being redistributed into platforms without complete Chromium OS
# developing environment.

# Checks if given command is available in current system
image_has_command() {
  type "$1" >/dev/null 2>&1
}

# Prints error message and exit as 1 (error)
image_die() {
  echo "ERROR: $@" >&2
  exit 1
}

# Finds the best gzip compressor and invoke it
image_gzip_compress() {
  if image_has_command pigz; then
    # echo " ** Using parallel gzip **" >&2
    # Tested with -b 32, 64, 128(default), 256, 1024, 16384, and -b 32 (max
    # window size of Deflate) seems to be the best in output size.
    pigz -b 32 "$@"
  else
    gzip "$@"
  fi
}

# Finds the best bzip2 compressor and invoke it
image_bzip2_compress() {
  if image_has_command pbzip2; then
    pbzip2 "$@"
  else
    bzip2 "$@"
  fi
}

# Finds if current system has tools for part_* commands
image_has_part_tools() {
  image_has_command cgpt || image_has_command parted
}

# Finds the best partition tool and print partition offset
image_part_offset() {
  local file="$1"
  local partno="$2"
  local unpack_file="$(dirname "$file")/unpack_partitions.sh"

  # TODO parted is available on most Linux so we may deprecate other code path
  if image_has_command cgpt; then
    cgpt show -b -i "$partno" "$file"
  elif image_has_command parted; then
    # First trial-run to make sure image is valid (because awk always return 0)
    parted -m "$file" unit s print | grep -qs "^$partno:" || exit 1
    parted -m "$file" unit s print | awk -F ':' "/^$partno:/ { print int(\$2) }"
  elif [ -f "$unpack_file" ]; then
    awk "/ $partno  *Label:/ { print \$2 }" "$unpack_file"
  else
    exit 1
  fi
}

# Finds the best partition tool and print partition size
image_part_size() {
  local file="$1"
  local partno="$2"
  local unpack_file="$(dirname "$file")/unpack_partitions.sh"

  # TODO parted is available on most Linux so we may deprecate other code path
  if image_has_command cgpt; then
    cgpt show -s -i "$partno" "$file"
  elif image_has_command parted; then
    # First trial-run to make sure image is valid (because awk always return 0)
    parted -m "$file" unit s print | grep -qs "^$partno:" || exit 1
    parted -m "$file" unit s print | awk -F ':' "/^$partno:/ { print int(\$4) }"
  elif [ -s "$unpack_file" ]; then
    awk "/ $partno  *Label:/ { print \$3 }" "$unpack_file"
  else
    exit 1
  fi
}

# Dumps a file by given offset and size (in sectors)
image_dump_partial_file() {
  local file="$1"
  local offset="$2"
  local sectors="$3"
  local bs=512

  # Try to use larger buffer if offset/size can be re-aligned.
  # 2M / 512 = 4096
  local buffer_ratio=4096
  if [ $((offset % buffer_ratio)) -eq 0 -a \
       $((sectors % buffer_ratio)) -eq 0 ]; then
    offset=$((offset / buffer_ratio))
    sectors=$((sectors / buffer_ratio))
    bs=$((bs * buffer_ratio))
  fi

  if image_has_command pv; then
    dd if="$file" bs=$bs skip="$offset" count="$sectors" \
      oflag=sync status=noxfer 2>/dev/null |
      pv -ptreb -B $bs -s $((sectors * bs))
  else
    dd if="$file" bs=$bs skip="$offset" count="$sectors" \
      oflag=sync status=noxfer 2>/dev/null
  fi
}

# Dumps a specific partition from given image file
image_dump_partition() {
  local file="$1"
  local part_num="$2"
  local offset="$(image_part_offset "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"
  local size="$(image_part_size "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"

  image_dump_partial_file "$file" "$offset" "$size"
}

# Maps a specific partition from given image file to a loop device
image_map_partition() {
  local file="$1"
  local part_num="$2"
  local offset="$(image_part_offset "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"
  local size="$(image_part_size "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"

  sudo losetup --offset $((offset * 512)) --sizelimit=$((size * 512)) \
    -f --show "$file"
}

# Unmaps a loop device created by image_map_partition
image_unmap_partition() {
  local map_point="$1"

  sudo losetup -d "$map_point"
}

# Mounts a specific partition inside a given image file
image_mount_partition() {
  local file="$1"
  local part_num="$2"
  local mount_point="$3"
  local mount_opt="$4"
  local offset="$(image_part_offset "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"
  local size="$(image_part_size "$file" "$part_num")" ||
    image_die "failed to find partition #$part_num from: $file"

  if [ -z "$mount_opt" ]; then
    # by default, mount as read-only.
    mount_opt=",ro"
  fi

  sudo mount \
    -o "loop,offset=$((offset * 512)),sizelimit=$((size * 512)),$mount_opt" \
    "$file" \
    "$mount_point"
}

# Unmounts a partition mount point by mount_partition
image_umount_partition() {
  local mount_point="$1"

  sudo umount -d "$mount_point"
}

# Copy a partition from one image to another.
image_partition_copy() {
  local src="$1"
  local srcpart="$2"
  local dst="$3"
  local dstpart="$4"

  local srcoffset=$(image_part_offset "${src}" "${srcpart}")
  local dstoffset=$(image_part_offset "${dst}" "${dstpart}")
  local length=$(image_part_size "${src}" "${srcpart}")
  local dstlength=$(image_part_size "${dst}" "${dstpart}")

  if [ "${length}" -gt  "${dstlength}" ]; then
    exit 1
  fi

  # Try to use larger buffer if offset/size can be re-aligned.
  # 2M / 512 = 4096
  local buffer_ratio=4096
  local bs=512
  if [ $((dstoffset % buffer_ratio)) -eq 0 -a \
       $((length % buffer_ratio)) -eq 0 ]; then
    dstoffset=$((dstoffset / buffer_ratio))
    bs=$((bs * buffer_ratio))
  fi

  image_dump_partition "${src}" "${srcpart}" |
      dd of="${dst}" bs="${bs}" seek="${dstoffset}" conv=notrunc oflag=dsync
}

# Temporary object management
_IMAGE_TEMP_OBJECTS=""

# Add a temporary object (by mktemp) into list for image_clean_temp to clean
image_add_temp() {
  _IMAGE_TEMP_OBJECTS="$_IMAGE_TEMP_OBJECTS $*"
}

# Cleans objects tracked by image_add_temp.
image_clean_temp() {
  local temp_list="$_IMAGE_TEMP_OBJECTS"
  local object
  _IMAGE_TEMP_OBJECTS=""

  for object in $temp_list; do
    if [ -d "$object" ]; then
      sudo umount -d "$object" >/dev/null 2>&1 || true
      sudo rmdir "$object" >/dev/null 2>&1 || true
    else
      rm -f "$object" >/dev/null 2>&1 || true
    fi
  done
}

# Determines the boot type of a ChromeOS kernel partition.
# Prints "recovery", "ssd", "usb", "factory_install", "invalid", or "unknown".
image_cros_kernel_boot_type() {
  local keyblock="$1"
  local magic flag skip kernel_config

  # TODO(hungte) use vbutil_keyblock if available

  # Reference: firmware/include/vboot_struct.h
  local KEY_BLOCK_FLAG_DEVELOPER_0=1  # Developer switch off
  local KEY_BLOCK_FLAG_DEVELOPER_1=2  # Developer switch on
  local KEY_BLOCK_FLAG_RECOVERY_0=4  # Not recovery mode
  local KEY_BLOCK_FLAG_RECOVERY_1=8  # Recovery mode
  local KEY_BLOCK_MAGIC="CHROMEOS"
  local KEY_BLOCK_MAGIC_SIZE=8
  local KEY_BLOCK_FLAG_OFFSET=72  # magic:8 major:4 minor:4 size:8 2*(sig:8*3)

  magic="$(dd if="$keyblock" bs=$KEY_BLOCK_MAGIC_SIZE count=1 2>/dev/null)"
  if [ "$magic" != "$KEY_BLOCK_MAGIC" ]; then
    echo "invalid"
    return
  fi
  skip="$KEY_BLOCK_FLAG_OFFSET"
  flag="$(dd if="$keyblock" bs=1 count=1 skip="$skip" 2>/dev/null |
          od -t u1 -A n)"
  if [ "$((flag & KEY_BLOCK_FLAG_RECOVERY_0))" != 0 ]; then
    echo "ssd"
  elif [ "$((flag & KEY_BLOCK_FLAG_RECOVERY_1))" != 0 ]; then
    if [ "$((flag & KEY_BLOCK_FLAG_DEVELOPER_0))" = 0 ]; then
      echo "factory_install"
    else
      # Recovery or USB. Check "cros_recovery" in kernel config.
      if image_has_command dump_kernel_config; then
        kernel_config="$(dump_kernel_config "$keyblock")"
      else
        # strings is less secure than dump_kernel_config, so let's try more
        # keywords
        kernel_config="$(strings "$keyblock" |
                         grep -w "root=" | grep -w "cros_recovery")"
      fi
      if (echo "$kernel_config" | grep -qw "cros_recovery") &&
         (echo "$kernel_config" | grep -qw "kern_b_hash"); then
        echo "recovery"
      else
        echo "usb"
      fi
    fi
  else
    echo "unknown"
  fi
}