The RADII Bootloader

RADII is an EFI bootloader written in C, and built with CMake.

The vision for RADII involves an easily customizable bootloader, including a boot information structure based on a configuration file. This would allow for the ability to adapt the layout of the information passed to the kernel based on that specific kernel's needs.

The hope of creating this bootloader is to gain understanding of the full framework of an OS, from hardware to userland.

By no means does this bootloader aim to cover the UEFI specification in full, but it does implement enough for necessary and useful functionality.

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Table of Contents

• Operating Systems that Use RADII
• Building RADII
  • Dependencies
  • Bootloader
• Booting RADII
  • Boot Media Generation
  • Virtual Machines
    • QEMU
    • VirtualBox
    • VMWare Workstation Player

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Operating Systems that Use this Bootloader

• COMING SOON - LensorOS

Building RADII

• Dependencies
• Bootloader

NOTE: Every block of shell commands assumes a starting working directory of this repository, RADII.

Dependencies

Tools required for the build:

• CMake
  • Windows: CMake download page
  • Debian: sudo apt install cmake
• a MinGW x86_64 cross-compiler
  • Windows: TDM-GCC
  • Debian: sudo apt install binutils-mingw-w64-x86-64 gcc-mingw-w64-x86-64

NOTE: Both CMake and the cross compiler must be in the PATH environment variable.

With the pre-requisite tools installed and added to the PATH environment variable, we are ready to begin.

Bootloader

CMake is a build-system generator that takes into account the host machine, and supports lots of different build systems (GNU make, Ninja, etc).

In a terminal, enter the following command to generate a GNU Make build system that uses our cross compiler in the bld subdirectory:

cmake -G "Unix Makefiles" -S . -B bld

To invoke the generated build system (and actually build the bootloader), use the following command:

cmake --build bld

At this point, bin/main.efi will have been generated. This is the executable EFI application that UEFI hardware is able to run.

Booting RADII

• Boot Media Generation
• Virtual Machines

Boot Media Generation

CMake targets that generate boot media are listed below. Nested underneath each are it's dependencies, or programs it requires to work. If the dependencies are not found on the system at the time of CMake configuration, the targets will not be included in the generated build system.

• image_dir -- Directory structure of a UEFI-compatible boot image.
• image_raw -- FAT32 UEFI-compatible boot image.
  • dd -- Native command on Unix
    • On Windows, use one of the following options:
      • MinGW installer to get MSYS coreutils ext package
      • Cygwin
      • Windows Subsystem for Linux
  • GNU mtools -- MS/DOS filesystem manipulation
    • Home Page
    • Debian distros: sudo apt install mtools
    • Pre-built binaries for Windows

Virtual Machines

• QEMU

  Get QEMU

  Invoke a CMake target to run QEMU, launching the RADII bootloader upon startup:

cmake --build bld -t run_qemu

• VirtualBox

  Get VirtualBox

1. Click the New button to create a new virtual machine.
2. In the pop-up window, give the new virtual machine a name and a file path you are comfortable with.
3. Select Type of Other and Version of Other/Unknown (64-bit).
4. Leave the memory size how it is; 64MB is plenty at this time.
5. Select the Do not add a virtual hard disk option.
6. Click the Create button to create the new virtual machine.
7. Select the new VM in the list on the left, then click the Settings button.
8. Navigate to System within the list on the left.
   1. Change Chipset to ICH9.
   2. Enable Extended Feature Enable EFI (special OSes only).
9. Navigate to Storage within the list on the left.
   1. Right click the default controller (IDE), and select Remove Controller.
   2. Right click the area labeled Storage Devices, and select AHCI (SATA).
   3. Right click the new AHCI storage controller, and select either Optical Drive or Hard Disk depending on whether you'd like to boot from the .iso or .bin, respectively.
   4. Click Add in the new Virtual Media Selector window that pops up.
   5. Browse to the bin subdirectory and, depending on whether Optical Drive or Hard Disk was selected, choose either the .iso or the .bin disk image file.
10. Navigate to Network within the list on the left.
    1. Disable all network adapters.

• VMWare Workstation Player

  Get VMWare Workstation Player

1. Select Home in the list on the left side. Click Create a New Virtual Machine on the right.
2. Select the I will install the operating system later. option.
3. Select a guest OS of Other, and a Version of Other 64-bit.
4. Give the virtual machine a name and path you are comfortable with. Keep note of the path.
5. It will ask about a disk, but the disk it's asking about won't be used. Click next.
6. The next screen should be an overview of the virtual machine hardware. Click Customize Hardware....
   1. Select New CD/DVD on the left, then click Advanced... on the right.
   2. Select SATA, then click OK.
   3. On the right, select Use ISO image file, and then click Browse....
   4. Select the .iso image file located in the bin subdirectory.
   5. Select the hard drive that we skipped configuring in the list on the left.
   6. Remove the hard drive using the Remove button near the bottom center.
   7. Remove any and all network adapters and sound cards in the same manner.
   8. Click Close in the bottom right to close the hardware configuration window.
7. Click Finish.
8. Navigate to the path specified in step #5, where the virtual machine is located.
   1. Open the file ending with .vmx in a text editor.
   2. Add the following line of text: firmware="efi".
   3. Save the file, then close it.

You will have to select UEFI Shell once VMware Workstation boots into LensorOS (even if it says something like "Unsupported").

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