constanos — An experimental x86 64 operating system…

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About this project

An x86-64 kernel written from scratch in Rust (no_std, UEFI, SMP) with a Linux-numbered syscall ABI. It runs unmodified BusyBox, Rust std programs (tokio included), DOOM and Quake, has its own desktop compositor, and drives an NVIDIA RTX 3050 all the way up to Vulkan through a port of Mesa's NVK. Runs in QEMU and on a real Ryzen machine. A one-person project, built with Claude Code.

Everything below runs today, in QEMU and on one physical machine (Ryzen 9 5900X) that has no serial port, no PS/2 and no IDE — keyboard, mouse and disk all come in over USB.

Screenshots: the desktop · glass in the GPU compositor · DOOM · Quake

Kernel

UEFI boot, SMP up to 32 CPUs with a preemptive scheduler shared by all of them and cross-CPU TLB shootdown.
Buddy + slab allocators, demand paging, copy-on-write fork, shared memory.
Threads, futex, POSIX signals, job control; pipes, AF_UNIX sockets with SCM_RIGHTS, ptys, epoll.
VFS with procfs, devfs, ramfs and read-write ext2.

Linux compatibility

Linux syscall numbers, with mlibc as the libc (one fix sent upstream: managarm/mlibc#1925).
Unmodified BusyBox 1.36.1 is the userland.
Static x86_64-unknown-linux-musl Rust programs run as they are, tokio's multi-threaded runtime included.

GPU: NVIDIA RTX 3050 (GA106)

Its own display code: VBIOS, EDID, DisplayPort/HDMI link training, scanout.
Boots NVIDIA's GSP-RM firmware, then GPU page tables, GPFIFO channels, the copy engine.
/dev/nvgpu backs a port of Mesa's NVK: Vulkan compute, 3D, swapchain and buffers shared between processes. A Vulkan snake game and the GPU compositor run on it at 60 fps.

Desktop

Its own Wayland-style protocol and two compositors (CPU and Vulkan) drawing the same display list, compared pixel by pixel in the tests.
Live-switchable themes, a terminal emulator, a CPU monitor, TrueType text, PNG; DOOM and Quake in windows, with sound through its own AC97 driver.

Real hardware

Its own xHCI driver (USB keyboard, mouse, mass storage), a Realtek RTL8168 NIC driver with smoltcp (TCP, UDP, ICMP, DHCP), a kernel log written to a partition of the boot stick, and unattended test runs with a watchdog.

Testing

The logic that doesn't need hardware lives in separate crates with host tests; the rest is tested in QEMU (kernel tests, a Linux ABI suite, desktop end-to-end tests). A test counts only once it fails when the code it covers is sabotaged.

What's missing

Dynamic linking, isolation between processes on the GPU, IPv6/TLS.

A personal project to learn how an operating system is built, developed with a lot of help from Claude Code.