Koerix

What is Koerix?

Koerix is a Unix-like hobby OS written in C++. I am mainly targeting the x86_64 (on PC) and the armv6a and AArch64 (on raspi/raspi4) architectures. This repo is the patched-together result of ~4 years of on/off work on my OS projects (turns out OS development is real hard, so I started over again a few times). It's not the most stable, yet, (especially on real hardware) but I'm getting there.

Version 1.0 will be shipped as soon as bash and busybox are up and running :)

In the image, you can see the userspace program textcon in action. the terminal to the left shows the serial output. textcon will print everything on the screen it reads from it's stdin (in this case, the serial console).

Licensing

While the kernel (directories arch/, platform/, kernel/) and userspace environment programs (env/) is licensed under the terms of the GNU Lesser General Public License, the directory libc/ contains large parts of the Musl libc, which is provided under the terms of the MIT license. Additionally, all files should have a SPDX comment at the top stating the exact license and copyright holder. If they don't: please tell me or open a pull request.

Roadmap

Now that the OS actually runs quite nicely on real hardware, it's time to implement some new features:

• Fixing any stability issues (race conditions)
• Add APIC and SMP support (supported by limine bootloader): I want to add it as soon as possible in order to be able to detect synchronization issues early.
• Writing a driver for SATA drives and implementing ext2 filesystem support: pretty much a must-have for any serious OS. After that, I can start thinking about porting some actually useful software, like bash.
• raspi1 port (BCM2835/armv6), since I have some old 32bit pis that are too slow for anything else and I think that's a nice re-use application.

Recently, I completely dropped support for 32bit x86 (i386 architecture), since I think supporting it would be too much added complexity that I don't want (cannot map the whole physical RAM in the upper half, jumping to higher half requires some extra magic), given that I don't even own corresponding hardware anymore. However, I will eventually support executing 32bit code in userspace (compatibility mode).

Current Kernel Features

• x86_64 kernel (64bit) written in C++, C as well as some GNU Assembler
• preemptive multitasking (single core), Mutexes and Spinlocks
• full paged Virtual Memory support
• POSIX fork() with multi-level copy-on-write
• read(), write(), open(), close() via Virtual file system (WIP)
• system calls via software interrupt 0x80
• limine bootloader
• POSIX pipes (create by calling pipe pipe(), use by fork()ing)
• Processes and Threads (but no exec() so far)
• OS support for FPU/SSE

Drivers

• PC Serial port driver (for getting a shell and some debug output)
• Rudimentary support for PS/2 keyboard

Userspace features

• Standard C-library (by copying and modifying sources from musl libc as needed)
• Access to full resolution framebuffer, font rendering and draw functions via libc in userspace.
• Create userspace threads with functions from koerix/threads.h

Available Software

• textcon: A userspace program that prints everything it reads from stdin to the framebuffer providing a text console. It also opens the keyboard device and prints everything it reads from there to stdout.

Runtime configuration

The kernel can be configured at boot time (via the kernel command line) to do a few things. For example:

• console=/dev/uart0 will open a serial console on uart0 (first serial port)
• init=/bin/init will load the specified binary from disk and run it after booting
• init=@some_mod will load the specified module passed via the bootloader and run it after booting

Building

Building the kernel and userspace binaries:

$ git clone --recursive https://github.com/ulmer-a/koerix
$ mkdir -p koerix/build && cd koerix/build
$ cmake ..
$ make -j

Assembling a diskimage:

$ make disk    # this will build the limine bootloader
               # from source and generate a disk image
$ make qemu    # this will start your diskimage in QEMU