lzungri / laritos

Highly-configurable and modular arm32 operating system created from scratch

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laritOS

laritOS is a highly-configurable, modular, test-driven developed operating system prototype created entirely from scratch, from bootloader to kernel, kernel to drivers, toolchain (including a minimal libc) to userspace applications.

The primary aim of laritOS is to provide a set of free resources (codebase, documentation, tutorials) for learning about operating system internals. Therefore, its focus is put mainly on simplicity, maintainability, modularity, debuggability and testability. Aspects such as performance, security, compatibility with existing OSes are not the priority for now.

The operating system is composed of the following 3 components, each of them with its corresponding repository:

Component	Description
laritos	Kernel + drivers + board-specific resources + tests + misc tools
laritos-toolchain	Minimal libc + userspace apps building tools
laritos-apps	Userland applications such as shell, ps unix-like tool for listing processes, testing apps, etc

Wiki

For the complete OS documentation, please refer to the wiki page

Features

Kernel features

• Multitasking with kernel preemption
• Userspace/kernelspace and system call support
• Testing infrastructure for Test Driven Development (TDD) with more than 250 tests already implemented
• Interrupt management infrastructure
• ARM 32bits support (armv7a)
• Spinlock support
• Semaphores, reentrant mutex and atomic32/64 support
• Priority-based scheduler (round robin by default)
• Support for multiple architectures by separating the kernel generic code from the architecture-specific code. So far, only the armv7a (arm 32 bits) arch has been implemented
• Monolitic but modular kernel (not a microkernel 😢)
• Configurable kernel parameters via the Kbuild infrastructure, this is the same builder used by Linux ported to laritOS
• Configurable target hardware specs via board/<boardname/*.bi (board information) files. This could be seen as a very simplified version of the Linux device tree
• Hierarchical Virtual File System (VFS) supporting ext2 and pseudofs (aka in-memory filesystems, e.g. /proc, stats fs)
• Kernel heap and stack protector
• Dynamic system configuration via properties (/property pseudo filesystem)
• Monouser
• Userspace shell
• ELF support for userspace applications
• Health monitor service configurable via system properties

Future features

• SMP support
• UI
• Multiuser support
• Virtual memory
• Memory protection
• and many more...

Toolchain features

• Easy to use build tools
• Minimal libc support for functions such as sleep, chdir, listdir, open, close, read, write, spawn_process, waitpid, time, printf, yield, exit, and more
• ARM 32bits support (armv7a)
• Debug utilities

See laritos-toolchain repo for more info

Userspace features

• Minimal shell supporting commands such as cat, xxd, run, run in the background, cd, mkdir, ls, getprop, and others
• ps program for listing active processes

See laritos-app repo for more info

Building, installing and running

See wiki page

Status

laritOS is currently in alpha version, hence some features may not work as expected and stability is not guaranteed. Use at your own risk 💥

License

The code is licensed under the MIT license.