ZenOS  

Warning

There might be dragons and bugs.

Overview

ZenOS is a 64-bit SMP preemptive operating system built from scratch in C and x86_64 assembly, bootstrapped with the Limine bootloader.

The project focuses on clean design, correctness, and real hardware interaction.

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Key Features

Kernel

• 64-bit x86_64 monolithic kernel
• Symmetric Multiprocessing (SMP)
• Preemptive round-robin SMP scheduler
• ELF64 userspace execution
• Dynamic loader
• Unix-style process model
• High-resolution timing via HPET
• ACPI-based hardware discovery and power management

Syscalls

75+ POSIX-compatible / custom syscalls covering major app and C library needs.

Hardware & Drivers

• Framebuffer output
• PS/2 keyboard and mouse
• PC speaker
• Serial port for debugging and logging
• Local APIC and IOAPIC interrupt handling
• ATA disk driver (DMA/PIO, 28-bit LBA)
• PCI bus
• Intel e1000 Ethernet driver
• RTC, HPET

Networking

• TCP/IP stack
• DNS resolution
• zen — a package manager that fetches and installs packages over HTTP
• wget — downloads files over HTTP/1.0

Filesystem

• VFS layer with support for multiple mountpoints
• FAT32 via a port of FatFs by CHAN
• Native host-side disk image tooling (fat_man)

Userspace & Libc

• mlibc C library.
• ELF64 userspace programs.
• Dynamic ELF loader : ld.so.

Applications

• Shell & Core Utils — shell, echo, yes, sleep, cat, ls, touch, rm, stat, wc, mkdir, rmdir, pwd, mv, cp, rename
• Process Utils — ps, kill
• System Info — uname, time
• Math — calc, primes, fibonacci, counter
• Text & UI — Harp (Custom compositor and server for Zen), terminal (PTY terminal emulator), edit (non-harp text editor), clock, beep, mouse, FIGlet, Kilo, DOOM.
• Compilers — TinyCC, SmallerC
• Scripting — Lua 5.5.0
• Networking — wget, zen package manager
• Misc — hello, init

The ZenOS.vhd in the repository usually already has these compiled and ready. A separate Storage.vhd is present for storage.

I/O & Display

• Flanterm for early kernel output
• Scalable font rendering via SSFN
• Structured kernel logging with log levels and serial output

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Building

Run make help first to see available build commands.

• Build everything: make all from the repo root
• Missing dependencies will be reported with clear errors
• make funcs generates funcs.txt listing all defined functions in the codebase

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Contributions

All good contributions are welcome. Check ISSUES.md for open problems, or add a feature, fix a bug, or improve the codebase.

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Design Goals

• Clean, minimal, readable codebase
• Solid foundation for experimenting with:
  • Kernel subsystems
  • Filesystems
  • Scheduling and SMP
  • Userspace ABI design
  • Unix-compatible process model (fork/exec/signals/pipes/PTY)
  • Networking (TCP/IP, DNS, HTTP)
  • Native C compilation on the OS itself
  • Lightweight everyday utilities
  • Dual-boot support

ZenOS is a learning-oriented project. Understanding the machine comes first for me.

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Toolchain / Prerequisites

clang
ld.lld
nasm
basename
ninja
meson
xorriso
qemu-system-x86_64
gdb
socat

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Third Party

• Check CREDITS.md for the list of third party apps and libraries.

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Showcase (may be outdated)

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ZenOS