unidos - *NIX for DOS-era systems

Unidos is a UNIXlike kernel and user environment targeting period-correct 80386 hardware.

More specific documentation about what the project entails can be found in the docs directory.

Prerequisites (Arch)

I am building on an Arch-based distro, but if you have access to a Linux machine with the following tools, you should be able to compile and run it.

• nasm
• cmake
• ninja
• qemu-system-i386 (optional but recommended)
• bochs (optional)
• dosfstools (mkfs.fat)
• mtools (mcopy)

I also recommend PCem for period-correct emulation (I use the AMIBIOS 386DX ROM for testing).

Build image

• Configure: cmake --preset debug
• Build: cmake --build --preset debug

Output image:

• build/debug/out/floppy.img

Run

• QEMU: cmake --build --preset run-qemu
• Bochs: cmake --build build/debug --target run-bochs

Current state

• stage1 is the boot sector at LBA 0.
• stage2 is written raw to reserved sectors starting at LBA 1.
• FAT12 is formatted with extra reserved sectors so the stage2 reserved area is not part of normal file allocation.
• kernel is copied into the FAT12 filesystem as KERNEL.BIN.
• Parameters passed to the kernel are stored in the filesystem root in kparams.dat and are loaded into ESI at kernel entry.
• Kernel contains basic VGA text driver for debugging on live hardware, and is currently getting descriptors set up to commence on real kernel work.