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EFI Kernel Extractor

This project provides a C utility to extract and decompress a Linux kernel image from an EFI application file, specifically designed to handle ARM64 kernels that are embedded within EFI zboot images. The utility verifies the image, decompresses it if necessary, and saves the decompressed kernel to an output file.

Features

  • EFI zboot Image Handling: Detects and processes Linux EFI zboot images.
  • Decompression: Supports gzip compression format for the kernel image.
  • ARM64 Verification: Ensures that the extracted image is a valid ARM64 kernel before saving.

Getting Started

Prerequisites

  • Compiler: A C compiler like gcc.
  • Build System: Meson and Ninja.
  • Libraries: This utility relies on the following libraries:
    • glib-2.0
    • zlib

Installing Dependencies on Fedora

You can install the necessary dependencies on Fedora using:

sudo dnf install gcc meson ninja-build glib2-devel zlib-devel

Installing Dependencies on Ubuntu

You can install the necessary dependencies on Ubuntu using:

sudo apt-get install build-essential meson ninja-build libglib2.0-dev zlib1g-dev

Installing Dependencies on Alpine

You can install the necessary dependencies on Alpine using:

sudo apk add meson gcc glib-dev musl-dev

Building the Utility

To build the program, follow these steps:

  1. Clone the repository and navigate to the project directory:

    git clone https://github.com/eballetbo/unzboot
cd unzboot

  2. Configure the build directory using Meson:

    meson setup build

  3. Build the project using Ninja:

    meson compile -C build

The compiled binary will be available in the build directory.

Usage

Once compiled, the program can be run from the command line with the following syntax:

./build/unzboot <input_file> <output_file>
  • input_file: The path to the EFI application containing the compressed kernel image.
  • output_file: The path to the output file where the decompressed kernel will be saved.

Example

./build/unzboot efi_image.efi vmlinuz

This will extract the kernel image from efi_image.efi and save it as vmlinuz if it is a valid ARM64 compressed image.

Error Handling

The utility includes error checks for:

  • Incorrect or unsupported EFI zboot images.
  • Issues during decompression.
  • Verification failures for the ARM64 kernel image.

If an error occurs, a descriptive message will be printed to stderr, and the program will exit with a non-zero status.

License

This project is licensed under the MIT License. See the LICENSE file for more details.

Acknowledgments

  • Unpacking functionality is derived from qemu, originally authored by Fabrice Bellard.
  • Gunzip functionality is derived from u-boot by Wolfgang Denk and Semihalf.
  • EFI zboot image format based on the Linux upstream specification.

Contributing

Contributions are welcome! Please open an issue or submit a pull request on GitHub if you have suggestions or improvements.

Contact

For any questions or issues, feel free to open an issue on this repository or contact the maintainer.