An operating system implemented entirely from scratch (no existing kernel), spanning kernel development, driver architecture, filesystems, userland applications, and UI frameworks.

Technical Scope

Multi-architecture kernel: x86/x86-64, ARMv7, Arm64, RISC-V support with unified codebase
Custom bootloaders for each architecture with ELF validation and secure boot integration
Full userspace stack: C/C++ standard libraries, Objective-C runtime, UI framework, window server
Production OS features: Ext2 filesystem, virtual filesystem layer, process management, POSIX signals, TTY subsystem

Core Technical Implementation

Kernel Architecture

Preemptive Multitasking & Scheduling

Priority-based round-robin scheduler with 12 priority levels
Per-CPU runqueues for SMP support (multi-core)
Conditional kernel preemption (PREEMPT_KERNEL flag for real-time responsiveness)
Interrupt depth counter preventing race conditions during context switches
Idle threads for zero-allocation interrupt handling

Memory Management

Virtual memory manager with per-process address spaces
Demand paging and swap support
Kernel/userspace memory isolation with access validation
Shared buffers for zero-copy IPC

System Call Interface

60+ system calls following POSIX conventions (fork, exec, read, write, mmap, etc.)
Architecture-specific syscall dispatch (software interrupts on x86, svc on ARM)
Kernel-mode syscalls (ksys1-ksys4) for internal operations

Boot Process & Security

Custom Bootloader Chain

Stage 1 (x86): Real-mode to protected-mode transition, memory map collection
Stage 2/Prekernel: ELF loader, device tree initialization, MMU setup
Kernel validation: SHA256 + RSA signature verification before execution
Passes boot arguments (boot_args_t) with memory layout, framebuffer, device tree

Filesystem & Device Management

Ext2 filesystem with full read/write support
Virtual filesystem (VFS) layer abstracting file operations
/dev (device nodes) and /proc (process/system introspection) filesystems
Device tree parsing for ARM/RISC-V hardware discovery
Device driver framework with pluggable driver registration

Userland & UI

Window Server (compositing manager)

Client-server architecture using IPC
Desktop and mobile window management modes
Hardware-accelerated rendering via LibG
Menu bar, dock, popup system

Libraries

LibC/LibCxx: POSIX-compliant C library and C++ STL
LibObjC: Objective-C runtime (message dispatch, ARC)
LibFoundation: Event loop, shared buffers, collections (Cocoa-inspired)
LibG: 2D graphics (pixel buffers, fonts, PNG/BMP loaders)
LibUI: High-level UI widgets (buttons, text fields, windows)

Key Engineering Decisions

1. Multi-Architecture Support
Abstracted platform-specific code (kernel/platform/{x86,arm32,arm64,riscv}) with common interfaces for MMU, interrupts, context switching. Enables same kernel codebase across all targets.

2. Build System
GN (Generate Ninja) meta-build system for fast incremental builds. Compiles for multiple architectures from single source tree.

3. Bootloader Security
Validates kernel ELF binary cryptographically before loading—prevents tampered kernel execution (verified boot).

4. Preemptive vs Cooperative
Kernel preemption is compile-time optional (-DPREEMPT_KERNEL). Enables low-latency scheduling when enabled, or simpler non-preemptive model for easier debugging.

5. Window Server Architecture
Separates compositing from applications—crash in user app doesn't take down entire UI. Similar to X11/Wayland model.

Features

Kernel

x86/x86-64, ARMv7 and Arm64 kernel with pre-emptive multi-threading
Ext2 filesystem
/dev and /proc filesystems
Local sockets
POSIX signals
TTY
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Libraries

Runtime & support: LibC, LibCxx, LibObjC
Rich functionality: LibFoundation
UI functionality & rendering: LibG, LibUI
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Userland

Composing windows manager for desktop and mobile
Simple UI apps
Terminal

Boot

Custom bootloaders
Kernel validation during the boot proccess
Custom device tree
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How to build and run xOS?

See the build instructions

Languages

C 65.8%

C++ 25.4%

Python 4.7%

Assembly 2.5%

Shell 0.9%

Other 0.7%