Exokernel Doom development repo

Repo layout

• src/
  • boot.s — Multiboot header + _start entry (sets up stack, calls kernel_main)
  • kernel.c — freestanding C kernel entrypoint (writes to VGA text buffer)
  • linker.ld — places kernel at 2M, defines sections, entrypoint _start
  • grub.cfg — GRUB menu entry that multiboot-loads /boot/exodoom
• docker/
  • Dockerfile.build — i686-elf cross compiler + GRUB ISO tools
  • Dockerfile.qemu — QEMU runtime image
  • scripts/build.sh — build script run inside the build container
• Makefile — convenience targets to build + run

Dependencies

Required (host machine)

• Docker (or compatible: Podman should work if it supports docker CLI well enough)
• GNU Make

That’s it. No local cross-compiler required.

What Docker images provide

• techiekeith/gcc-cross-i686-elf base image for i686-elf-gcc / i686-elf-as
• GRUB + ISO tooling inside the build container (grub-mkrescue, grub-file, xorriso)
• QEMU inside the run container (qemu-system-i386)

How the build works (high level)

The build container runs docker/scripts/build.sh:

1. Assemble src/boot.s → build/boot.o
2. Compile src/kernel.c (freestanding) → build/kernel.o
3. Link with src/linker.ld → build/exodoom
4. Verify it’s Multiboot-valid using grub-file
5. Stage an ISO tree under build/isodir/boot/...
6. Create build/exodoom.iso using grub-mkrescue

Outputs:

• build/exodoom (kernel ELF)
• build/exodoom.iso (bootable ISO)

Makefile usage

Build everything (kernel + ISO) in Docker

make docker-build

Build, then boot the ISO in QEMU (GRUB menu)

make docker-run

Build, then boot the kernel directly (no GRUB menu) <--- Recommended for development iteration

make docker-run-kernel

Clean build artifacts

make clean

Keyboard shortcuts

• Ctrl + A then X to exit QEMU
• Ctrl + A then C to open QEMU monitor (for debugging)

Notes / gotchas

• Pressing Enter at the GRUB menu doesn't work right now. Boot directly for the time being, unless debugging the GRUB config.
• QEMU is run with -display curses and serial attached to your terminal (-serial mon:stdio).
• The kernel currently writes to VGA text memory at 0xB8000, so you should see output in the QEMU display.
• If you edit src/grub.cfg, it gets copied into the ISO staging directory during build.

License

MIT License (at least for now, may change later...?)