KleineOS kernel

KleineOS (lit. Small Operating System) is a simple kernel that runs on the RISC-V ISA. It is written using Rust, leveraging increased memory safety along with superior design patterns to provide a safe and modular base for writing other applications on.

As it stands, kleineOS is just a hobby project. While I do have some long-term visions, I do not yet know how they should be manifest into the codebase.

Goals of the project

I would consider this hobby project "done" when I have:

1. A Gemini (protocol not AI) server
2. A Gemini (protocol not AI) client

I would also like to make this happen, if I can pull it off:

1. A mechanism to reload the kernel without reloading the userspace

Building

The core build system for kleineOS uses just, bash and cargo. You also need QEMU (with RISC-V support) to actually run the kernel.

For developing for kleineOS, I recommend the RISC-V GNU toolchain. It provides utilities with RISC-V support, such as objdump, gdb, as, etc.

Some systems have different binary names for some of the tools we rely on. You can modify the variables set at the bottom of the justfile to your liking. The variables you might need to modify on some systems are:

# tools we use (can differ on other distros)
QEMU := env("QEMU", "qemu-system-riscv64")
DEBUGGER := env("DEBUGGER", "rust-gdb")
OBJDUMP := env("OBJDUMP", "riscv64-linux-gnu-objdump")

Once everything is set, you can run the cargo run command. This should fetch all the dependencies, compile the code and run a QEMU virtual machine to execute the kernel. You should see some logs from OpenSBI before the first line of code in our OS is executed.

$ cargo run
# ... collapsed OpenSBI output ...

^w^ welcome to my operating system
DEBUG: KERNEL STARTING ON HART#0

Architecture support

I do not have any plans of extending architecture support. I am very inexperienced when it comes to osdev, and juggling between multiple CPUs will put too much strain on my peanut noggin. Instead, I will (try to) put // TODO-ARCH-RISCV comments wherever I am hardcoding RISC-V specific behaviour. Once I have enough of these comments, I will abstract all arch specific stuff in an arch module, and make it generic over a trait (if such a thing is possible even).

Contributing

Contributions are welcome! Do keep in mind that this is an educational project for me, so I might end up asking too many questions about your code. Do not submit patches if you cannot explain it! If you want to find things to contribute, run grep -rE "TODO|HACK|FIXME" **/*/*.rs in the root of this project.

TODO list

This is the TODO for what I am working on right now.

• VirtIO block driver spec from the PDF

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All code is licensed under the Apache-2.0 license

Copyright Kunal Dandekar (2025)