UEFI Playground

Low-level firmware development in C

A hands-on exploration of UEFI internals, boot processes, memory management and system initialization.

Built with:

C
GNU-EFI
QEMU
OVMF
Linux

Modern operating systems hide many low-level details behind layers of abstraction.

This project explores what happens before an operating system starts: how firmware initializes hardware, provides services, manages memory and transfers control to the next boot stage.

Getting Started

New to UEFI development or this project?

Start here: Getting Started

Architecture

Linux Host
    |
    v
QEMU + OVMF Firmware
    |
    +--> UEFI Applications
    |       |
    |       +--> Memory Map Viewer
    |       +--> Filesystem Explorer
    |       +--> Graphics Demo
    |
    +--> Boot Loader
            |
            +--> Linux Loader (planned)

Learning Topics

UEFI Applications and Boot Services
Memory management via GetMemoryMap()
Filesystem access through EFI protocols
Graphics Output Protocol (GOP)
Boot process transition (firmware -> OS)
QEMU + OVMF emulation environment

Applications

The project currently contains several standalone UEFI applications exploring different parts of the firmware environment.

Memory Map Viewer

Explores how UEFI represents system memory before the operating system starts.

Features:

Retrieves the firmware memory map via GetMemoryMap()
Displays EFI memory descriptors
Groups contiguous memory regions
Calculates memory sizes

Memory Map Viewer output

Filesystem Explorer

Demonstrates access to EFI filesystem protocols.

Features:

Locates EFI Simple File System Protocol
Opens filesystem volumes
Enumerates directories
Reads file metadata

Filesystem Explorer output

Graphics Output Protocol Demo

Explores direct framebuffer access using the UEFI Graphics Output Protocol.

Features:

Retrieves framebuffer information
Draws pixels directly into framebuffer memory
Implements basic drawing primitives

Graphics Output Protocol Demo

Hello World UEFI Application

The first application of the project.

It demonstrates:

Creating a .efi executable
Receiving the UEFI System Table
Writing output through firmware services

Hello World running in UEFI Shell

Core Concepts

Technical Findings

During development several implementation details turned out to be less obvious than expected.

Topics include: