Qualcomm Snapdragon (MSM) bootloader.img format: Ruby parsing library

A bootloader for Android used on various devices powered by Qualcomm Snapdragon chips:

https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors

Although not all of the Snapdragon based Android devices use this particular bootloader format, it is known that devices with the following chips have used it (example devices are given for each chip):

(*) bootloader_size is equal to the size of the whole file (not just img_bodies as usual).

(**) There are some data after the end of img_bodies.

On the other hand, devices with these chips do not use this format:

The bootloader-*.img samples referenced above originally come from factory images packed in ZIP archives that can be found on the page Factory Images for Nexus and Pixel Devices on the Google Developers site. Note that the codenames on that page may be different than the ones that are written in the list above. That's because the Google page indicates ROM codenames in headings (e.g. "occam" for Nexus 4) but the above list uses model codenames (e.g. "mako" for Nexus 4) because that is how the original bootloader-*.img files are identified. For most devices, however, these code names are the same.

File extension

img

KS implementation details

License: CC0-1.0

This page hosts a formal specification of Qualcomm Snapdragon (MSM) bootloader.img format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.

The Ruby runtime library can be installed from RubyGems:

gem install kaitai-struct

Code

Parse a local file and get structure in memory:

data = AndroidBootldrQcom.from_file("path/to/local/file.img")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = AndroidBootldrQcom.new(Kaitai::Struct::Stream.new(bytes))

After that, one can get various attributes from the structure by invoking getter methods like:

data.bootloader_size # => According to all available `releasetools.py` versions from AOSP (links are
in the top-level `/doc`), this should determine only the size of
`img_bodies` - there is [an assertion](
https://android.googlesource.com/device/lge/hammerhead/+/7618a7d/releasetools.py#167)
for it.

However, files for certain Pixel devices (see `/doc`) apparently declare
the entire file size here (i.e. including also fields from `magic` to
`img_headers`). So if you interpreted `bootloader_size` as the size of
`img_bodies` substream in these files, you would exceed the end of file.
Although you could check that it fits in the file before attempting to
create a substream of that size, you wouldn't know if it's meant to
specify the size of just `img_bodies` or the size of the entire bootloader
payload (whereas there may be additional data after the end of payload)
until parsing `img_bodies` (or at least summing sizes from `img_headers`,
but that's stupid).

So this field isn't reliable enough to be used as the size of any
substream. If you want to check if it has a reasonable value, do so in
your application code.

Ruby source code to parse Qualcomm Snapdragon (MSM) bootloader.img format

android_bootldr_qcom.rb

Download 

# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

require 'kaitai/struct/struct'

unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
  raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end


##
# A bootloader for Android used on various devices powered by Qualcomm
# Snapdragon chips:
# 
# <https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors>
# 
# Although not all of the Snapdragon based Android devices use this particular
# bootloader format, it is known that devices with the following chips have used
# it (example devices are given for each chip):
# 
# * APQ8064 ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_S4_Pro))
#   - Nexus 4 "mako": [sample][sample-mako] ([other samples][others-mako]),
#     [releasetools.py](https://android.googlesource.com/device/lge/mako/+/33f0114/releasetools.py#98)
# 
# * MSM8974AA ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_800,_801_and_805_(2013/14)))
#   - Nexus 5 "hammerhead": [sample][sample-hammerhead] ([other samples][others-hammerhead]),
#     [releasetools.py](https://android.googlesource.com/device/lge/hammerhead/+/7618a7d/releasetools.py#116)
# 
# * MSM8992 ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_808_and_810_(2015)))
#   - Nexus 5X "bullhead": [sample][sample-bullhead] ([other samples][others-bullhead]),
#     [releasetools.py](https://android.googlesource.com/device/lge/bullhead/+/2994b6b/releasetools.py#126)
# 
# * APQ8064-1AA ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_600_(2013)))
#   - Nexus 7 \[2013] (Mobile) "deb" <a href="#doc-note-data-after-img-bodies">(\**)</a>: [sample][sample-deb] ([other samples][others-deb]),
#     [releasetools.py](https://android.googlesource.com/device/asus/deb/+/14c1638/releasetools.py#105)
#   - Nexus 7 \[2013] (Wi-Fi) "flo" <a href="#doc-note-data-after-img-bodies">(\**)</a>: [sample][sample-flo] ([other samples][others-flo]),
#     [releasetools.py](https://android.googlesource.com/device/asus/flo/+/9d9fee9/releasetools.py#130)
# 
# * MSM8996 Pro-AB ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_820_and_821_(2016)))
#   - Pixel "sailfish" <a href="#doc-note-bootloader-size">(\*)</a>:
#     [sample][sample-sailfish] ([other samples][others-sailfish])
#   - Pixel XL "marlin" <a href="#doc-note-bootloader-size">(\*)</a>:
#     [sample][sample-marlin] ([other samples][others-marlin])
# 
# * MSM8998 ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_835_(2017)))
#   - Pixel 2 "walleye" <a href="#doc-note-bootloader-size">(\*)</a>: [sample][sample-walleye] ([other samples][others-walleye])
#   - Pixel 2 XL "taimen": [sample][sample-taimen] ([other samples][others-taimen])
# 
# <small id="doc-note-bootloader-size">(\*)
# `bootloader_size` is equal to the size of the whole file (not just `img_bodies` as usual).
# </small>
# 
# <small id="doc-note-data-after-img-bodies">(\**)
# There are some data after the end of `img_bodies`.
# </small>
# 
# ---
# 
# On the other hand, devices with these chips **do not** use this format:
# 
# * <del>APQ8084</del> ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_800,_801_and_805_(2013/14)))
#   - Nexus 6 "shamu": [sample][foreign-sample-shamu] ([other samples][foreign-others-shamu]),
#     [releasetools.py](https://android.googlesource.com/device/moto/shamu/+/df9354d/releasetools.py#12) -
#     uses "Motoboot packed image format" instead
# 
# * <del>MSM8994</del> ([devices](https://en.wikipedia.org/wiki/Devices_using_Qualcomm_Snapdragon_processors#Snapdragon_808_and_810_(2015)))
#   - Nexus 6P "angler": [sample][foreign-sample-angler] ([other samples][foreign-others-angler]),
#     [releasetools.py](https://android.googlesource.com/device/huawei/angler/+/cf92cd8/releasetools.py#29) -
#     uses "Huawei Bootloader packed image format" instead
# 
# [sample-mako]: https://androidfilehost.com/?fid=96039337900113996 "bootloader-mako-makoz30f.img"
# [others-mako]: https://androidfilehost.com/?w=search&s=bootloader-mako&type=files
# 
# [sample-hammerhead]: https://androidfilehost.com/?fid=385035244224410247 "bootloader-hammerhead-hhz20h.img"
# [others-hammerhead]: https://androidfilehost.com/?w=search&s=bootloader-hammerhead&type=files
# 
# [sample-bullhead]: https://androidfilehost.com/?fid=11410963190603870177 "bootloader-bullhead-bhz32c.img"
# [others-bullhead]: https://androidfilehost.com/?w=search&s=bootloader-bullhead&type=files
# 
# [sample-deb]: https://androidfilehost.com/?fid=23501681358552487 "bootloader-deb-flo-04.02.img"
# [others-deb]: https://androidfilehost.com/?w=search&s=bootloader-deb-flo&type=files
# 
# [sample-flo]: https://androidfilehost.com/?fid=23991606952593542 "bootloader-flo-flo-04.05.img"
# [others-flo]: https://androidfilehost.com/?w=search&s=bootloader-flo-flo&type=files
# 
# [sample-sailfish]: https://androidfilehost.com/?fid=6006931924117907154 "bootloader-sailfish-8996-012001-1904111134.img"
# [others-sailfish]: https://androidfilehost.com/?w=search&s=bootloader-sailfish&type=files
# 
# [sample-marlin]: https://androidfilehost.com/?fid=6006931924117907131 "bootloader-marlin-8996-012001-1904111134.img"
# [others-marlin]: https://androidfilehost.com/?w=search&s=bootloader-marlin&type=files
# 
# [sample-walleye]: https://androidfilehost.com/?fid=14943124697586348540 "bootloader-walleye-mw8998-003.0085.00.img"
# [others-walleye]: https://androidfilehost.com/?w=search&s=bootloader-walleye&type=files
# 
# [sample-taimen]: https://androidfilehost.com/?fid=14943124697586348536 "bootloader-taimen-tmz30m.img"
# [others-taimen]: https://androidfilehost.com/?w=search&s=bootloader-taimen&type=files
# 
# [foreign-sample-shamu]: https://androidfilehost.com/?fid=745849072291678307 "bootloader-shamu-moto-apq8084-72.04.img"
# [foreign-others-shamu]: https://androidfilehost.com/?w=search&s=bootloader-shamu&type=files
# 
# [foreign-sample-angler]: https://androidfilehost.com/?fid=11410963190603870158 "bootloader-angler-angler-03.84.img"
# [foreign-others-angler]: https://androidfilehost.com/?w=search&s=bootloader-angler&type=files
# 
# ---
# 
# The `bootloader-*.img` samples referenced above originally come from factory
# images packed in ZIP archives that can be found on the page [Factory Images
# for Nexus and Pixel Devices](https://developers.google.com/android/images) on
# the Google Developers site. Note that the codenames on that page may be
# different than the ones that are written in the list above. That's because the
# Google page indicates **ROM codenames** in headings (e.g. "occam" for Nexus 4)
# but the above list uses **model codenames** (e.g. "mako" for Nexus 4) because
# that is how the original `bootloader-*.img` files are identified. For most
# devices, however, these code names are the same.
# @see https://android.googlesource.com/device/lge/hammerhead/+/7618a7d/releasetools.py Source
class AndroidBootldrQcom < Kaitai::Struct::Struct
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    @magic = @_io.read_bytes(8)
    raise Kaitai::Struct::ValidationNotEqualError.new([66, 79, 79, 84, 76, 68, 82, 33].pack('C*'), magic, _io, "/seq/0") if not magic == [66, 79, 79, 84, 76, 68, 82, 33].pack('C*')
    @num_images = @_io.read_u4le
    @ofs_img_bodies = @_io.read_u4le
    @bootloader_size = @_io.read_u4le
    @img_headers = []
    (num_images).times { |i|
      @img_headers << ImgHeader.new(@_io, self, @_root)
    }
    self
  end
  class ImgHeader < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @name = (Kaitai::Struct::Stream::bytes_terminate(@_io.read_bytes(64), 0, false)).force_encoding("ASCII")
      @len_body = @_io.read_u4le
      self
    end
    attr_reader :name
    attr_reader :len_body
  end
  class ImgBody < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self, idx)
      super(_io, _parent, _root)
      @idx = idx
      _read
    end

    def _read
      @body = @_io.read_bytes(img_header.len_body)
      self
    end
    def img_header
      return @img_header unless @img_header.nil?
      @img_header = _root.img_headers[idx]
      @img_header
    end
    attr_reader :body
    attr_reader :idx
  end
  def img_bodies
    return @img_bodies unless @img_bodies.nil?
    _pos = @_io.pos
    @_io.seek(ofs_img_bodies)
    @img_bodies = []
    (num_images).times { |i|
      @img_bodies << ImgBody.new(@_io, self, @_root, i)
    }
    @_io.seek(_pos)
    @img_bodies
  end
  attr_reader :magic
  attr_reader :num_images
  attr_reader :ofs_img_bodies

  ##
  # According to all available `releasetools.py` versions from AOSP (links are
  # in the top-level `/doc`), this should determine only the size of
  # `img_bodies` - there is [an assertion](
  # https://android.googlesource.com/device/lge/hammerhead/+/7618a7d/releasetools.py#167)
  # for it.
  # 
  # However, files for certain Pixel devices (see `/doc`) apparently declare
  # the entire file size here (i.e. including also fields from `magic` to
  # `img_headers`). So if you interpreted `bootloader_size` as the size of
  # `img_bodies` substream in these files, you would exceed the end of file.
  # Although you could check that it fits in the file before attempting to
  # create a substream of that size, you wouldn't know if it's meant to
  # specify the size of just `img_bodies` or the size of the entire bootloader
  # payload (whereas there may be additional data after the end of payload)
  # until parsing `img_bodies` (or at least summing sizes from `img_headers`,
  # but that's stupid).
  # 
  # So this field isn't reliable enough to be used as the size of any
  # substream. If you want to check if it has a reasonable value, do so in
  # your application code.
  attr_reader :bootloader_size
  attr_reader :img_headers
end