Georgios

Georgios (Greek version of the name George, said like GORE-GEE-OS) is an operating system I’m making for fun which currently targets i386/IA-32. The purpose of this project is to serve as a learning experience.

Work in progress graphics mode:

https://user-images.githubusercontent.com/5941194/180702578-91270793-c91c-4f24-b7e1-f86bc2b48c53.mp4

Features

Working on at least some minimal level

• Kernel console that supports UTF-8 (specifically the subset needed for Code page 437 subset) and some basic ANSI escape codes
• Support for multiple mounted filesystems:
  • Ext2 accessed using an ATA Driver (read only)
  • In-memory filesystem mounted at boot (read/write)
• Basic preemptive multitasking between processes that can be loaded from ELF files
• ACPI shutdown using ACPICA

Started on, but not really working yet

• A graphics mode using VESA BIOS Extensions (VBE)
  • This will use libx86emu to invoke the BIOS code required to switch to VBE graphics modes. This doesn’t really work yet though.
  • This can be bypassed with make multiboot_vbe=true, which has GRUB set a fixed VBE graphics mode. This is how the demo above was ran. This is not the default for a number of reasons:
    • The major reason is the graphics are slow. This can be seen in the demo, especially when the Apollo earthrise picture takes a moment to get drawn on the screen.
    • It’s a fixed graphics mode when the kernel starts and so nothing gets printed to the screen until the graphical console is ready. So an error before this wouldn’t get printed, which is a problem when running on real hardware.
    • The graphical console is mostly done but missing things like the cursor and text rendering is a bit off.
• USB 2.0 stack
• Porting real applications written in Zig and C
  • The applications currently written in Zig are “real” as in they are compiled and ran separately from the kernel, are running in x86 ring3, and can’t take the whole system down (for the most part). The issue is they are compiled using the freestanding target. To be able to use a Zig or C hello world program without any modification, the standard libraries would have to be ported and toolchains would have to be modified to target Georgios properly.
• Freeing the OS from the need of a boot CD
• PS/2 Mouse support
  • Can be tried out by building with make mouse=true and running test-mouse. This isn’t enabled by default becuase currently the keyboard and mouse cross talk when being used at the same time.

Building

Building Georgios requires a Unix-like environment with:

• Zig 0.9.1
• Python 3
• Bridle
  • Is a submodule, but it needs to be installed using pip install --user scripts/codegen/bridle.
• GRUB2
  • Requires i686 Support (grub-pc-bin package on Ubuntu)
• xorriso (xorriso package on Ubuntu)

Georgios can be built as a bootable ISO (called georgios.iso) by running make. If installed, QEMU and Bochs can be run by running make qemu or make bochs respectively. On Ubuntu, Bochs requires apt-get install bochs bochsbios bochs-sdl bochs-x vgabios.

For the moment it assumes the existence of an IDE disk with certain files on it.

Resources Used

• OSDev Wiki
  • Very popular, fairly large set of resources in one place, but rough or just plain unhelpful in many places.
• The little book about OS development
  • Polished, but limited intro into x86 OS development. Provided me with the initial start.
• Intel x86 Software Development Manuals
• xv6
• The Design and Implementation of the 4.4 BSD Operating System
• FYSOS: Media Storage Devices
• UNIX Internals: The New Frontiers