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, loads drivers, launches programs, survives application crashes, runs Doom, plays video, talks TCP/IP, and occasionally reminds you that it is still a hobby kernel.

The codebase is small enough to understand, but no longer small enough to pretend it is just a weekend project.

features

• UEFI bootloader
• real SMP
• physical and virtual memory managers
• kernel pool and user heap
• single address-space design with user/supervisor page permissions
• HAL split from the kernel
• preemptive priority scheduler
• processes and threads
• per-process handles with rights checks
• process exit state, reaping, and restartable init services
• events, semaphores, mutexes, queues, named queues, and alertable waits
• IRQL, DPCs, kernel APCs, and user APCs
• native user-mode exception dispatch
• Win32 vectored exception handlers
• minimal runtime-registered SEH substrate
• async file I/O with events, IOSBs, APC callbacks, and cancellation
• VFS with IRPs
• page cache with dirty writeback and invalidation
• AHCI driver, interrupt-driven
• IDE driver, PIO/DMA
• FAT32 filesystem driver with VFAT long names
• USB bus, xHCI, mass storage, and HID
• VMware SVGA display driver
• drive-number paths such as 0:/apps/shell.exe
• PE import resolution and dynamic .sys driver loading
• modular networking through lwIP
• RTL8139 and RTL816x network drivers
• native BSD-ish socket syscalls
• DNS resolver syscall
• length-tracked string-view syscall ABI
• request-struct based syscalls for larger calls
• native NTLSTATUS_* status codes
• INI-based configuration
• partial Win32 personality
• partial (microsoft-level) POSIX personality
• Doom
• video playback
• fully GDPR-compliant
• everything but the kitchen sink

paths

"apps/shell.exe"      -> current working directory
"0:/apps/shell.exe"   -> volume 0, native path; works everywhere
"2:/data/config.ini"  -> volume 2, native path
"C:\apps\doom.exe"    -> volume 0 through win32.dll; C: maps to 0:, D: maps to 1:, etc.
"/apps/video.exe"     -> volume 0 through posix.dll
"/1/apps/video.exe"   -> volume 1 through posix.dll

Volumes 0-7 are available. A volume only works if a filesystem is registered on it.

The Win32 personality translates drive letters to volume numbers. The POSIX personality maps volumes into a tree.

how to build

• open the VS x64 build tools as administrator
• 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

efi/boot/
  bootx64.efi
boot.ini
drivers/
  drivers.ini
  ahci.sys
  ata.sys
  fat32.sys
  lwip.sys
  pci.sys
  ps2.sys
  rtl816x.sys
  rtl8139.sys
  usb.sys
  vmwaresvga.sys
system/
  colonel.exe
  hal.dll
  init.exe
  syscall.dll
  win32.dll
  posix.dll
apps/
  shell_native.exe
  shell_win32.exe
  shell_posix.exe
  async_apc.exe
  async_cancel.exe
  doom.exe
  video.exe
  httpget.exe
  tcpserve.exe
  udp.exe
  resolve.exe
  ping.exe

screenshots

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: todo

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

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: Depends how you frame it. Real apps won't run but specifically prepared ones will.

Q: Are processes isolated?
A: No. But IPC is free. 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: It will be once I get a job.

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 both Win32 and POSIX? A: NT could do it, why can't I?

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.