KaworuOS

A WIP Unix-like AArch64 operating system.

Building

If you use nix, nix develop sets up everything you will need in order to build and run the kernel under Qemu.

Building requires the following packages:

clang
lld

xorriso # to create iso image

qemu # to run
gnumake # ofcourse
python313Packages.kconfiglib

# llvm # not required, but contains useful tools like objdump, objcopy
# gdb # for debugging
# bear # if you want to generate compile_commands.json

Then generate a config using:

# Use the default config
make defconfig
# Or configure the kernel yourself and save it
make menuconfig

Then build the kernel

make

Running

I have yet to test this on actual hardware, I have only tested this on Qemu under the virt platform.

Since AArch64 only supports UEFI and not bios, you will need to provide UEFI firmware for Qemu. You can just download the full-release from the releases page as it contains both a built ISO Image and firmware you need to emulate under Qemu.

You can also download the firmware from the releases page of: https://github.com/osdev0/edk2-ovmf-stable-bins/releases/

Then set UEFI_FIRMWARE env pointing directly to the firmware.

This is done automatically if you're using nix.

run under Qemu:

make run

To-Do

- [x] Startup
    - [x] Exception vectors
    - [x] Setup system registers
    - [x] Setup boot cpu stack
    - [x] Enable interrupts

- [x] Spinlock

- [x] Uart driver
    - [x] init pl011
    - [x] `uart_putchar`/`uart_getchar`

- [x] Framebuffer
    - [x] Set up Flanterm

- [x] Console
    - [x] Generic console

- [x] Printf implementation
    - [x] `printf`, `vprintf`
    - [x] `panic`

- [x] Logging
    - [x] `DEBUG`, `INFO`, `WARN`, `ERROR`, `FATAL` conditional logging macros

- [ ] Exception handling
    - [x] Pretty exception dump
    - [ ] Decode ESR_EL1, FAR_EL1, ELR_EL1

- [x] Physical page allocator
    - [x] `kmem_alloc`/`kmem_free`

- [x] MMU
    - [x] page table setup
    - [x] map kernel
    - [x] map MMIO

- [x] Ranged bitmap allocator

- [ ] Virtual Memory
    - [x] kernel virtual memory manager
    - [x] `vm_alloc`/`vm_free` and `vm_map`/`vm_unmap`
    - [ ] Guard pages for kernel stacks

- [x] Kernel heap
    - [x] `kalloc`/`kfree`

- [x] Device driver manager

- [x] Interrupts
    - [x] GIC distributor init and cpu interface init
    - [x] IRQ framework

- [x] Timer
    - [x] Arm generic timer init
    - [x] Periodic timer interrupt

- [x] Semi hosting
    - [x] Semi hosting subsystem
    - [x] Attach as a console device

- [ ] Scheduler
    - [ ] Concept of task, task states
    - [ ] Run queue
    - [ ] Context switch

- [ ] Kernel Threads
    - [ ] `kthread_create`/`kthread_exit`
    - [ ] Idle thread
    - [ ] Scheduler (maybe round robin?)

- [ ] Userspace
    - [ ] EL0 entry support
    - [ ] User stack
    - [ ] User address space

- [ ] Syscalls
    - [ ] SVC handler
    - [ ] Syscall table
    - [ ] Basic ones like: read, write, exit, yield

- [ ] FS
    - [ ] Decide on a simple filesystem to implement.

Thirdparty

Limine - Modern, secure, portable, multi protocol bootloader and boot manager.
Flanterm - Fast and reasonably complete (frame buffer) terminal emulator.
libfdt - The device tree library

Resources

https://wiki.osdev.org
https://krinkinmu.github.io # thank you @krinkinmu
https://kernel-internals.org
https://df.lth.se/~getz/ARM/A64/
https://github.com/Elite-zx/Tiny-OS # thank you @Elite-zx
https://github.com/mit-pdos/xv6-riscv
https://github.com/arryndoestech/adt_os # thank you @arryndoestech
https://xv6-guide.github.io/xv6-riscv-book
https://github.com/gmarino2048/64bit-os-tutorial # thank you @gmarino2048
https://lowenware.com/blog/aarch64-mmu-programming/
https://developer.arm.com/documentation/ddi0487/latest
https://developer.arm.com/documentation/ddi0601/latest
https://cs140e.sergio.bz/docs/ARMv8-Reference-Manual.pdf