userspace-ntos

A from-scratch reimplementation of the Windows NT kernel personality in user space, running on the rust-micro seL4 microkernel. Everything is Rust.

NT's executive is a set of cooperating subsystems (Object Manager, Memory Manager, Process/Thread manager, I/O manager, …) layered over a small kernel. This project rebuilds that personality as isolated user-space components on a capability microkernel — the microkernel provides threads, address spaces, IPC, and capabilities; the NT semantics live entirely in user space. The first component is the NT Object Manager (the \ObjectDirectory namespace, typed objects, handles, symbolic links).

Repository layout

rust-micro/            the seL4-style microkernel (git submodule, pinned)
Cargo.toml             workspace for the host-testable NT crates (cargo test on the host)
crates/
  nt-status/           NTSTATUS-style status codes                       no_std
  nt-types/            ids, access masks, UnicodeString, NtPath parser   no_std + alloc
  nt-object-abi/       fixed-layout SURT wire ABI (opcodes + structs)    no_std
  nt-object-manager/   the Object Manager core (store/handles/namespace/symlinks/access)
  nt-object-server/    transport-agnostic service dispatcher (decode/validate/dispatch)
  nt-object-client/    ergonomic client stub over a pluggable transport backend
  ntos-root/           the root task the kernel boots (standalone, custom target)
components/
  object-manager/      the Object Manager as a seL4 component (runs the stack on the kernel)
  object-service/      client + server as TWO isolated components over SURT rings
  io-manager/          the I/O Manager (over an embedded OM) as isolated components over SURT
  driver-host/         the I/O Manager dispatching IRPs to an isolated driver peer over SURT
  driver-host-exec/    runs a REAL WDM .sys driver's DriverEntry on seL4 (x64 exec)
  driver-host-svc/     runs the real WDM driver in an ISOLATED seL4 child component
scripts/
  run.sh               build the hello root task + kernel and boot QEMU
  run-object-manager.sh  build + boot the Object Manager component in QEMU
  run-object-service.sh  build + boot the isolated client/server (over SURT) in QEMU
  run-io-manager.sh      build + boot the isolated I/O Manager client/server in QEMU
  run-driver-host.sh     build + boot the I/O Manager + isolated driver peer in QEMU
  run-driver-host-exec.sh  build + boot the real-driver executor (runs SurtTest.sys on seL4)
  run-driver-host-svc.sh   build + boot the real driver in an isolated child component
docs/compat-notes/     behavioural compatibility notes vs Windows NT
references/            NT/ReactOS/driver reference trees (gitignored, local only)

The host-testable NT core (nt-status, nt-types, nt-object-abi, nt-object-manager) is a normal cargo workspace — cargo test on your laptop, no seL4 or QEMU. The kernel-bound bins (ntos-root, components/*) are standalone crates built for the microkernel's bare-metal target and excluded from the workspace. Implementation follows the milestones in references/nt-object-manager-spec.md §22.

The kernel is a pinned git submodule, not vendored source: userspace-ntos depends on an exact kernel SHA (its syscall/invocation ABI is tightly coupled), and the NTOS components consume the kernel's ABI through one shared crate, rust-micro/crates/sel4-rt, rather than re-hand-rolling it.

Building & running

Requires the Rust nightly toolchain with rust-src (for -Z build-std), and the QEMU + image tooling the kernel's scripts use (see the submodule's README).

git clone --recursive https://github.com/stakach/userspace-ntos.git
cd userspace-ntos
./scripts/run.sh

Already cloned without --recursive? Fetch the kernel:

git submodule update --init --recursive

Expected boot output:

[ntos] userspace-ntos root task alive on rust-micro
[ntos]   node 0/4, first empty slot 34, ipc_buffer @ 0x...
[ntos]   5 untyped(s), 9 image frame cap(s)
[ntos] boot smoke-test OK

scripts/run.sh builds the ntos-root ELF (a minimal boot smoke-test), stages it as the kernel's rootserver, and drives the kernel's build+image+QEMU pipeline in extern-rootserver mode (bring your own root task).

Running the hosted ReactOS desktop (quick start)

The headline demo boots the rust-micro microkernel hosting real, unmodified GPL ReactOS binaries — smss.exe → csrss.exe → winlogon.exe → win32k.sys — all the way to a painted Windows desktop. One command from a fresh clone:

git clone --recursive https://github.com/stakach/userspace-ntos.git
cd userspace-ntos
./run.sh                # headless serial gate (default)
./run.sh --desktop      # boot with a QEMU window so you SEE the painted desktop

./run.sh (at the repo root — distinct from scripts/run.sh above) is a self-contained launcher that:

1. Preflight-checks every prerequisite (QEMU, mkfs.vfat/dosfstools, mmd/mcopy/mtools, bsdtar/libarchive, python3, the Rust nightly toolchain + rust-src, and OVMF/edk2 UEFI firmware). If anything is missing it prints a per-platform brew install … / apt install … remediation table and stops — no cryptic mid-build failure.
2. Checks out the rust-micro submodule if you forgot --recursive.
3. Fetches the ReactOS binaries on first run (a ~30 MiB GPL ReactOS x64 livecd, reactos-livecd-0.4.17-dev-478-g4117217, from iso.reactos.org; cached under rust-micro/.tmp/reactos/, extracted with bsdtar). Override the URL with REACTOS_7Z_URL=…. ReactOS is GPL, so its binaries are freely redistributable — the executive loads them via SEC_IMAGE and runs their real ntdll loader.
4. Builds the ntos-executive (the NT executive that hosts the ReactOS processes) + the kernel, and packs the FAT32/UEFI disk image.
5. Boots QEMU.

What you should see

Headless (default) — the serial log streams to your terminal and ends with the executive's success sentinel; run.sh then prints a clear verdict:

  PASS exec_win32k_desktop_painted
[ntos-exec] desktop-bg match 768/768 px, px0=0x003a6ea5 (expected 0x003a6ea5)
[ntos-exec summary: 140/94 executive->isolated-service checks passed]
[microtest done]
SUCCESS — the ReactOS stack booted and the win32k desktop painted (0x003a6ea5).

--desktop — a QEMU window opens showing the real painted desktop: win32k authentically fills the BOOTBOOT GOP framebuffer with the ReactOS desktop background colour 0x003a6ea5 (RGB 58,110,165) via winlogon's natural SwitchDesktop flow. This is a genuine graphics path (the real ReactOS win32k.sys + framebuf.dll display driver + ftfd.dll/Arial font stack), not a stub or a mock. The window persists after the run so you can see it — close it to quit.

Expected run time: ~1 minute once the toolchain is warm (the QEMU boot + gate is ~50 s); the very first run adds the one-time ReactOS download + a full cargo build.

Gotchas:

• The kernel is a git submodule (rust-micro); the build target is userspace-ntos/rust-micro, not any standalone checkout. A clone without --recursive needs git submodule update --init --recursive (the launcher does this for you).
• Some ReactOS binaries are only staged onto the disk image if they were fetched first — a fresh clone that skips the fetch step boots the kernel without the hosted processes. Always let ./run.sh run the fetch (it is idempotent and cached).

Updating the kernel

cd rust-micro && git checkout <new-sha> && cd ..
git add rust-micro && git commit -m "bump kernel to <new-sha>"

Pin to SHAs at milestones; point the submodule at a kernel branch during active co-development of kernel + NTOS.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option. This is an independent, clean-room reimplementation of NT concepts; it contains no Microsoft code and is not affiliated with or endorsed by Microsoft. "Windows" and "Windows NT" are trademarks of Microsoft Corporation.