RishiOS

RishiOS is an x86-64 operating system written from scratch in C and x86 Assembly. It includes a custom bootloader and kernel, and is designed to run in an emulated environment. Why? I was awestruck with how computers with silicon transistors are able to fire in such a way that we can run elegant software on them. In order to fully learn to appreciate all Unix-based devices, I decided to build an OS of my own, with a simple command-line retro feel to it.

System Requirements

The OS targets the following hardware configuration:

• x86-64 architecture
• 1G page support (pdpe1gb)
• xAPIC
• SSE2
• PS/2 keyboard
• ATA disk (IDE interface)
• No hard disk required at runtime, runs entirely in RAM

Project Structure

Directory	Description
bootloader/	Stage 1/2 bootloader written in x86 Assembly
kernel/	Kernel source in C and Assembly
user/	User-space programs
scripts/	Build and run scripts
bin/	Compiled binaries
boot.img	Bootable disk image (stable version)
os.img	Full OS disk image (FAT16 in-progress)
bochsrc.bxrc	Bochs emulator configuration for FAT16 version
old.bxrc	Bochs emulator configuration for stable version

Dependencies

Building from source requires:

• nasm
• x86_64-elf-gcc (cross-compiler, do NOT use the system gcc)
• make

Running the OS requires one of:

• QEMU (recommended, works on Linux and macOS)
• Bochs 2.7 (Windows, using bochsrc.bxrc)

Setup

Pre-built Image

If you would prefer a pre-built image, that is provided to you in releases. For contribution, however, it is necessary to build the system from a cross-compiler (x86_64-elf-gcc`, in this case).

Linux

Install dependencies:

sudo apt install nasm gcc-x86-64-linux-gnu qemu-system-x86

Build and run:

bash scripts/compile_run.sh

macOS

Install dependencies via Homebrew:

brew install nasm x86_64-elf-gcc qemu

Build:

bash scripts/compile_run.sh

compile_run.sh may give errors depending on the version that the script targeted. If all else fails, one can use the image file from releases.

Run:

qemu-system-x86_64 \
  -m 1G \
  -smp 1 \
  -cpu pentium3,+lm,+sse2,+apic,+pdpe1gb \
  -drive file=boot.img,format=raw,if=ide,media=disk \
  -machine type=pc-i440fx-9.2

Note: -enable-kvm and -mem-path /dev/hugepages are Linux-only flags and must be omitted on macOS.

Windows

Install Bochs 2.7 and open bochsrc.bxrc from the repo root, or use WSL (Debian) for building combined with Bochs on the Windows side:

scripts\windowsrun.bat

Requires WSL with Debian, NASM, and x86_64-elf-gcc installed inside WSL.

Results

Here is how RishiOS currently looks like from the QEMU emulator:

RishiOS.latest.version.mp4

This is from a MacOS system

Suggestions for me?

I am new to the world of OS development, and would love any suggestions for better code, or just tips in general :)