nt-lite/readme.md

# NT-Lite -- an x86-64 kernel

“Not only is UNIX dead, it’s starting to smell really bad.” - Rob Pike

“UNIX has three operations: read, write, and lie through ioctl.”

## what is it?

NT-Lite is a 64-bit operating system kernel written from scratch.

It boots into a shell, launches programs, runs Doom, talks TCP/IP, and occasionally reminds you that it is still a hobby kernel.

## features

- UEFI bootloader
- real SMP
- VAD-based virtual memory, file-backed and anonymous mmap, CoW, reclaim
- single address-space design with user/supervisor page permissions
- preemptive priority scheduler
- capability-style handles with rights checks, derivation, and revocation
- rich synchronization primitives
- IRQL, DPCs, kernel APCs, and user APCs
- user exception handling with structured and vectored handlers
- async file I/O with events, IOSBs, APC callbacks, and cancellation
- capability-relative VFS with IRPs
- refcounted mounted volumes with partition arrival/removal
- page cache with dirty writeback and invalidation
- USB bus, xHCI, mass storage, hubs, hotplug, and HID
- audio
- VMware SVGA display driver
- dynamic driver loading
- native BSD-ish socket syscalls
- DNS resolver syscall
- four-register syscall ABI with sized request structs for larger calls
- partial Win32 personality
- partial (microsoft-level) POSIX personality
- Doom
- video playback
- fully GDPR-compliant
- everything but the kitchen sink

## paths

You thought it would be easy, would you?

```text
"apps/shell_native.exe"             -> current working directory, resolved in userspace
"/SystemRoot/apps/shell_native.exe" -> system volume through the resource namespace
"/Device/HarddiskVolume1/boot.ini"  -> system volume through the resource namespace
"C:\apps\doom.exe"                  -> /SystemRoot/apps/doom.exe through win32.dll
"\apps\doom.exe"                    -> /SystemRoot/apps/doom.exe through win32.dll
"/apps/video.exe"                   -> /SystemRoot/apps/video.exe through posix.dll
```

Kernel filesystem syscalls are capability-relative; userspace owns the current working directory and resolves named resources through `rssrv`.

`/SystemRoot` is the configured boot volume. Other mounted volumes are discovered through the volume manager and opened by capability.

## networking

The socket syscalls are BSD-shaped, not BSD-compatible. Same nouns (AF_INET, SOCK_STREAM, IPPROTO_TCP), none of the baggage:  
one fixed-size tagged address struct instead of the sockaddr_in/sockaddr_storage casting dance,  
no htons/ntohl conversions, and DNS resolution is a syscall rather than a userspace library call.  
That's right microkernel purists, cry some more. Ergonomics.  
Async is first-class here too, same machinery as the filesystem. Except the DNS resolver. Ergonomics, am I right?

## how to build

- get mtools
- open the VS x64 build tools
- change into this directory
- run `build.bat`
- use one of:
  - `run.bat` — IDE
  - `rund.bat` — IDE, debug
  - `runa.bat` — AHCI
  - `runad.bat` — AHCI, debug

## how it looks when built

The ESP is just the boot anchor:

```text
efi/boot/
  bootx64.efi
efi/ntlite/fs/
  ...
boot.ini
```

The configured system volume carries the OS:

```text
system/
  colonel.exe
  hal.dll
  init.exe
  rssrv.exe
  syscall.dll
  win32.dll
  posix.dll
  settings.ini
drivers/
  drivers.ini
  ahci.sys
  ata.sys
  fat.sys
  hda.sys
  lwip.sys
  ntfs.sys
  ext4.sys
  pci.sys
  ps2.sys
  rtl816x.sys
  rtl8139.sys
  cereal.sys
  usb.sys
  vmwaresvga.sys
apps/
  shell_native.exe
  shell_win32.exe
  shell_posix.exe
  doom.exe
  video.exe
  edit.exe
  httpget.exe
  tcpserve.exe
  udp.exe
  resolve.exe
  ping.exe
  memtop.exe
```

## screenshots

![video.exe running bink video 2](image.png)

## faq

Q: Is it secure?
A: Don't connect to the internet with it.

Q: Who is this for?
A: Me.

Q: What's next?
A: Whatever I fixate on next.

Q: Does it run Doom?  
A: `doom.exe`

Q: Can it play Crysis?
A: Into the bucket list.

Q: Does USB work?
A: It did for everything I threw at it.

Q: If I write a program now, will it run in the future?
A: WE DO, in fact, BREAK USERSPACE.

Q: Can you read and write files?  
A: As far as I'm aware.

Q: Does it have async I/O?  
A: The best you'll get.

Q: Does the networking actually work?
A: It didn't crash yet.

Q: Does it really have SMP?
A: Watch out. It bites.

Q: Is the Win32 layer real?  
A: API wise, yes. Binary compatibility wise, close but no.

Q: Are processes isolated?  
A: No. But IPC is free. And you can't steal handles. Is this how a serious modern OS should isolate processes? No.  
Are we a serious OS? No. Is it very convenient? Absolutely.

Q: How often does it crash?  
A: It doesn't if you don't touch it.

Q: Can it recover from a crash?  
A: Works on my machine.

Q: Is this finished?  
A: Does it look finished?

Q: Will it corrupt my data?  
A: It shouldn't.

Q: Why is the path syntax so weird?  
A: It makes sense to me.

Q: Why are the logs so verbose?  
A: Try debugging an interrupt path with vibes.

Q: What should I read first?  
A: This document.

Q: How do I contribute?
A: `maksw@maksw.pl`

Q: Can I use this in production?  
A: Don't.

#### Project dedicated to the honorable, esteemed Professor Leszek Wójcik through whom I came to hate Unix.