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https://github.com/willothy/goose

Good ol' OS experiment. Probably bad. I have no idea what I'm doing, but the goal is to have some idea when I'm done.
https://github.com/willothy/goose

hobby-os kernel operating-system rust

Last synced: 23 days ago
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Good ol' OS experiment. Probably bad. I have no idea what I'm doing, but the goal is to have some idea when I'm done.

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# Goose (Good ol' OS experiment)



Hobby OS project. Probably very bad. I have no idea what I'm doing.



Inspired by [OSDev](https://wiki.osdev.org/Main_Page), [blog_os](https://os.phil-opp.com/),

and [StreamOS](https://github.com/sphaerophoria/stream-os).



## Goals



- 64-bit, x86_64

- Bootable by grub or similar (BIOS, UEFI is a non-goal for now)

  - Multiboot2

- Run on multiple CPU cores (SMP)

- Support for simple graphics such as text and shapes

- Preemptive, multicore scheduler (main goal, I want to learn about this)

- Userland processes

- Basic network stack (maybe a web server if I am lucky)

- TUI environment with builtin multiplexer

  - Vim bindings EVERYWHERE. Maybe I won't even support mouse at all.

  - If I am able to get GUI, then build the GUI around the terminal.

    Like tmux but you can have splits be GUI windows OR builtin terminals.



## About



I've followed the blog_os series before as well as the OSDev barebones tutorial, but I

am attempting to learn by doing with this project. I will be sometimes indirectly

following tutorials or courses I find, but for the most part

my goal here is to really figure out how OS dev works and how to do it myself.



I am writing it in Rust because I like Rust, but also because most of the available resources use

C so I will not have the temptation to copy-paste. Also, there will be crates available for some

tasks which is a nice improvement from c-land. I am already making use of the

[multiboot2](https://github.com/rust-osdev/multiboot2) and [spin](https://github.com/mvdnes/spin-rs) crates for

parsing multiboot info and sync primitives, respectively.



While I will use crates for some things, I will be implementing as much as possible

of the kernel myself. I really just didn't want to deal with multiboot or writing an elf parser.



## Architecture



Multiboot2 compatible.



Everything can be compiled with a standard nightly Rust toolchain (target = x86_64-unknown-none); no special gcc cross-compiler is needed.



`nasm` and a linker are required as well, to build the assembly files and construct the final executable.



The current build setup uses `grub-mkrescue` to construct a bootable image, but this could be adapted to other

bootloaders / systems as long as multiboot2 is supported.



Bootstrap (/boot.asm, /boot64.asm):



- This is where grub puts us initially

- setup stack and do protected mode (32-bit) init stuff

- setup basic paging so we can enter long mode

- setup basic gdt so CPU lets us into long mode

- setup long mode (64-bit)

- jump to kernel entry point in long mode



TODO: move some of this bootstrap code to 32-bit Rust. I tried to do this before

with *some* success, but found linking back and forth difficult so I went with full asm for now.



Kernel: (/kernel):



- Parse multiboot info (using multiboot2 crate)

- Setup VGA writer

- Setup long mode GDT (WIP)

- Setup IDT and interrupt handlers (WIP)

- Setup and enable PICs and PIT



Working (sorta) but not enabled:



- Jump to userland (WIP)

  - Currently cannot get interrupts to re-enable when entering user mode due to general protection fault



TODO:



- Setup long mode 4-level paging

- Memory allocator so I can use the `alloc` crate and the heap

- Test harness

- Serial driver

- USB driver

- Basic filesystem (FAT32?)

- Scheduler + processes

  - SMP boot / AP trampoline code

- etc...



Runner (/runner):



- Builds and runs the kernel

- I should look at how the bootloader / bootimage crates do things

- Need to make framework for running tests / communicating via serial.