os

Hobby i386 kernel / operating system.

• Active and planned work
• Design concepts and implementation references

This project started by following the tutorials under https://github.com/cfenollosa/os-tutorial but has diverged quite a bit since. Some components are still mostly the same (eg. src/boot/).

Goals

The OS will be finished when all of the following are implemented.

1. Able to get and draw basic http web page
2. Compiler for at least Assembly or C
3. Playable Minecraft Clone

The following lists show the planned development stages and planned tasks to achieve these goals.

Near Near Term

• Read extended kernel form floppy
• Switch to protected mode
• some stdio.h
• printf
• some string.h
• keyboard driver
• ata driver
• terminal with command parsing
• circular buffer + tests (builtin, needs separating)

Near Term

• Kernel stats (stats command returns # disk io, keys, mounts, etc.)
• Detect stack overflows
• fs
  • Finish implementing fs functions
  • Implement file io
• basic malloc (linked list)
• malloc
  • Actually manage memory
  • Need to find end of kernel to not overflow at runtime (for malloc start)
  • Detect max memory for malloc
  • Do that fancy memory map
• Paging
  • Setup page dir and table
  • Enter paging
• Load user space application
• Ring 3
  • Kernel Service Calls
• Date and Time
• Optional don't disable interrupts during interrupt (nested interrupts)
• Better key event buffer (with mods) (maybe in addition to char buffer)
• Change stdlib names with k prefix for namespace during testing
• Optimize disk read to check if area already in buffer

Long Term

These tasks will be broken down further after completion of Near Term, when there is a better foundation and design to work with.

• Switch to 2d graphics mode
• Virtual memory pages / memory paging
• Memory permissions (eg. stack can't exec, code can't write)
• User level applications (might need 3rd level kernel from filesystem)
• Testing
• FAT or EXT2 filesystem driver
• Audio Driver
• 64 bit support printf (needs libgcc)
• Text editor

Long Long Term

These tasks will be broken down further after completion of Long Term, when there is enough support for their development.

• Graphics card driver (pseudo opengl)
• Threading / multi-process
• (Maybe) Multiboot or GRUB?

Setup

You will need to install the gcc i386 elf cross compiler. This project expects this to be under ~/.local/opt/cross but this can be changed by editing the root CMakeLists.txt. For instructions of how to build the i386 elf compiler from source, follow the instructions on the OS-Dev Wiki GCC_Cross-Compiler

git clone git@github.com:automas-dev/os.git
cd os
make setup

Building

The os image can be found at build/os-image.bin, with an elf for the kernel at build/src/kernel/kernel.elf for debug symbols. Apps are combined in a tar file at build/apps.tar which is mounted by the kernel at runtime.

make build

Running

QEMU is used for cpu emulation and kernel execution. I'm using QEMU emulator version 10.1.0 (Debian 1:10.1.0+ds-5ubuntu2.4) but other versions should work. Logs will be written to stdout and kernel.log Qemu logs are written to qemu_logs.txt

make run

Once running, use the help command to see what you can do.

Kernel log level can be adjusted in src/kernel/src/loader.c in the function __start

Testing

make test
make test_cov
make test_cov DARK_MODE=ON

Formatting / Linting

make lint
make format