Qualcomm Snapdragon (MSM) bootloader.img format: C++98/STL 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 C++98/STL generated by Kaitai Struct depends on the C++/STL runtime library. You have to install it before you can parse data.

For C++, the easiest way is to clone the runtime library sources and build them along with your project.

Code

Using Kaitai Struct in C++/STL usually consists of 3 steps.

  1. We need to create an STL input stream (std::istream). One can open local file for that, or use existing std::string or char* buffer.
    #include <fstream>
    
    std::ifstream is("path/to/local/file.img", std::ifstream::binary);
    
    #include <sstream>
    
    std::istringstream is(str);
    
    #include <sstream>
    
    const char buf[] = { ... };
    std::string str(buf, sizeof buf);
    std::istringstream is(str);
    
  2. We need to wrap our input stream into Kaitai stream:
    #include "kaitai/kaitaistream.h"
    
    kaitai::kstream ks(&is);
    
  3. And finally, we can invoke the parsing:
    android_bootldr_qcom_t data(&ks);
    

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.

C++98/STL source code to parse Qualcomm Snapdragon (MSM) bootloader.img format

android_bootldr_qcom.h

#ifndef ANDROID_BOOTLDR_QCOM_H_
#define ANDROID_BOOTLDR_QCOM_H_

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

#include "kaitai/kaitaistruct.h"
#include <stdint.h>
#include <vector>

#if KAITAI_STRUCT_VERSION < 9000L
#error "Incompatible Kaitai Struct C++/STL API: version 0.9 or later is required"
#endif

/**
 * 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.
 * \sa https://android.googlesource.com/device/lge/hammerhead/+/7618a7d/releasetools.py Source
 */

class android_bootldr_qcom_t : public kaitai::kstruct {

public:
    class img_header_t;
    class img_body_t;

    android_bootldr_qcom_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent = 0, android_bootldr_qcom_t* p__root = 0);

private:
    void _read();
    void _clean_up();

public:
    ~android_bootldr_qcom_t();

    class img_header_t : public kaitai::kstruct {

    public:

        img_header_t(kaitai::kstream* p__io, android_bootldr_qcom_t* p__parent = 0, android_bootldr_qcom_t* p__root = 0);

    private:
        void _read();
        void _clean_up();

    public:
        ~img_header_t();

    private:
        std::string m_name;
        uint32_t m_len_body;
        android_bootldr_qcom_t* m__root;
        android_bootldr_qcom_t* m__parent;

    public:
        std::string name() const { return m_name; }
        uint32_t len_body() const { return m_len_body; }
        android_bootldr_qcom_t* _root() const { return m__root; }
        android_bootldr_qcom_t* _parent() const { return m__parent; }
    };

    class img_body_t : public kaitai::kstruct {

    public:

        img_body_t(int32_t p_idx, kaitai::kstream* p__io, android_bootldr_qcom_t* p__parent = 0, android_bootldr_qcom_t* p__root = 0);

    private:
        void _read();
        void _clean_up();

    public:
        ~img_body_t();

    private:
        bool f_img_header;
        img_header_t* m_img_header;

    public:
        img_header_t* img_header();

    private:
        std::string m_body;
        int32_t m_idx;
        android_bootldr_qcom_t* m__root;
        android_bootldr_qcom_t* m__parent;

    public:
        std::string body() const { return m_body; }
        int32_t idx() const { return m_idx; }
        android_bootldr_qcom_t* _root() const { return m__root; }
        android_bootldr_qcom_t* _parent() const { return m__parent; }
    };

private:
    bool f_img_bodies;
    std::vector<img_body_t*>* m_img_bodies;

public:
    std::vector<img_body_t*>* img_bodies();

private:
    std::string m_magic;
    uint32_t m_num_images;
    uint32_t m_ofs_img_bodies;
    uint32_t m_bootloader_size;
    std::vector<img_header_t*>* m_img_headers;
    android_bootldr_qcom_t* m__root;
    kaitai::kstruct* m__parent;

public:
    std::string magic() const { return m_magic; }
    uint32_t num_images() const { return m_num_images; }
    uint32_t ofs_img_bodies() const { return m_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.
     */
    uint32_t bootloader_size() const { return m_bootloader_size; }
    std::vector<img_header_t*>* img_headers() const { return m_img_headers; }
    android_bootldr_qcom_t* _root() const { return m__root; }
    kaitai::kstruct* _parent() const { return m__parent; }
};

#endif  // ANDROID_BOOTLDR_QCOM_H_

android_bootldr_qcom.cpp

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

#include "android_bootldr_qcom.h"
#include "kaitai/exceptions.h"

android_bootldr_qcom_t::android_bootldr_qcom_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent, android_bootldr_qcom_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = this;
    m_img_headers = 0;
    m_img_bodies = 0;
    f_img_bodies = false;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void android_bootldr_qcom_t::_read() {
    m_magic = m__io->read_bytes(8);
    if (!(magic() == std::string("\x42\x4F\x4F\x54\x4C\x44\x52\x21", 8))) {
        throw kaitai::validation_not_equal_error<std::string>(std::string("\x42\x4F\x4F\x54\x4C\x44\x52\x21", 8), magic(), _io(), std::string("/seq/0"));
    }
    m_num_images = m__io->read_u4le();
    m_ofs_img_bodies = m__io->read_u4le();
    m_bootloader_size = m__io->read_u4le();
    int l_img_headers = num_images();
    m_img_headers = new std::vector<img_header_t*>();
    m_img_headers->reserve(l_img_headers);
    for (int i = 0; i < l_img_headers; i++) {
        m_img_headers->push_back(new img_header_t(m__io, this, m__root));
    }
}

android_bootldr_qcom_t::~android_bootldr_qcom_t() {
    _clean_up();
}

void android_bootldr_qcom_t::_clean_up() {
    if (m_img_headers) {
        for (std::vector<img_header_t*>::iterator it = m_img_headers->begin(); it != m_img_headers->end(); ++it) {
            delete *it;
        }
        delete m_img_headers; m_img_headers = 0;
    }
    if (f_img_bodies) {
        if (m_img_bodies) {
            for (std::vector<img_body_t*>::iterator it = m_img_bodies->begin(); it != m_img_bodies->end(); ++it) {
                delete *it;
            }
            delete m_img_bodies; m_img_bodies = 0;
        }
    }
}

android_bootldr_qcom_t::img_header_t::img_header_t(kaitai::kstream* p__io, android_bootldr_qcom_t* p__parent, android_bootldr_qcom_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = p__root;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void android_bootldr_qcom_t::img_header_t::_read() {
    m_name = kaitai::kstream::bytes_to_str(kaitai::kstream::bytes_terminate(m__io->read_bytes(64), 0, false), std::string("ASCII"));
    m_len_body = m__io->read_u4le();
}

android_bootldr_qcom_t::img_header_t::~img_header_t() {
    _clean_up();
}

void android_bootldr_qcom_t::img_header_t::_clean_up() {
}

android_bootldr_qcom_t::img_body_t::img_body_t(int32_t p_idx, kaitai::kstream* p__io, android_bootldr_qcom_t* p__parent, android_bootldr_qcom_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = p__root;
    m_idx = p_idx;
    f_img_header = false;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void android_bootldr_qcom_t::img_body_t::_read() {
    m_body = m__io->read_bytes(img_header()->len_body());
}

android_bootldr_qcom_t::img_body_t::~img_body_t() {
    _clean_up();
}

void android_bootldr_qcom_t::img_body_t::_clean_up() {
}

android_bootldr_qcom_t::img_header_t* android_bootldr_qcom_t::img_body_t::img_header() {
    if (f_img_header)
        return m_img_header;
    m_img_header = _root()->img_headers()->at(idx());
    f_img_header = true;
    return m_img_header;
}

std::vector<android_bootldr_qcom_t::img_body_t*>* android_bootldr_qcom_t::img_bodies() {
    if (f_img_bodies)
        return m_img_bodies;
    std::streampos _pos = m__io->pos();
    m__io->seek(ofs_img_bodies());
    int l_img_bodies = num_images();
    m_img_bodies = new std::vector<img_body_t*>();
    m_img_bodies->reserve(l_img_bodies);
    for (int i = 0; i < l_img_bodies; i++) {
        m_img_bodies->push_back(new img_body_t(i, m__io, this, m__root));
    }
    m__io->seek(_pos);
    f_img_bodies = true;
    return m_img_bodies;
}