A 64-bit operating system kernel written from scratch. UEFI bootloader, physical and virtual memory managers, preemptive scheduler, HAL, VFS, PE loader, partial Win32 layer. It boots into a shell. ~20k lines of C and assembly.

features

UEFI bootloader
physical memory manager
virtual memory manager with kernel pool
HAL (screen, keyboard, mouse, timer, disk, PCI, APIC)
preemptive scheduler with priority levels
processes and threads
VFS with IRPs
drive-letter paths (0:\apps\shell.exe)
INI-based boot and driver configuration
PE import resolution and dynamic driver loading
Win32 personality (partial)
POSIX personality (partial)

how 2 build

open vs x64 build tools as admin
cd into this directory
mkimage.bat
build.bat
run.bat(ide)/rund.bat(ide, debug)/runa.bat(ahci)/runad.bat(ahci, debug)
enjoy

how it looks when built

I have some strong opinions on OS design.

efi/boot/
  bootx64.efi
boot.ini
hal.dll
colonel.exe
drivers/
  drivers.ini
  ide.sys
  ahci.sys
  fat32.sys
syscall.dll
win32.dll
posix.dll
shell.exe
video.exe

driver model

drivers are PE32+ .sys files with an entry point preferably named DriverEntry accepting a constant pointer to HAL_API.

drivers to be loaded have their path stored in drivers.ini, split into essential for boot (loaded by bootloader) and not required for boot (loaded by kernel).

a disk driver fills in a DISK_DRIVER vtable and calls IoRegisterDisk(index, &driver). a filesystem driver fills in an IO_FILESYSTEM vtable and calls IoRegisterFilesystem(index, &fs, &vol).

currently shipping: AHCI (interrupts), IDE (PIO/DMA) and FAT32.

how it boots

UEFI loads boot.ini, reads drivers.ini
bootloader maps kernel, HAL, and boot drivers into the upper half
direct physical window at 0xFFFF880000000000
jumps to KernelMain
PMM, VMM, GDT, IDT, HAL, IRQs, scheduler
loads runtime drivers from disk
launches shell.exe

paths (because they're different)

"apps\shell.exe"     -> current working directory
"0:\apps\shell.exe"  -> drive 0
"2:\data\config.ini" -> drive 2

Drives 0-7. A drive only works if a filesystem registered on it.
The Win32 personality translates drive letters to drive numbers, the POSIX personality maps drives onto a tree.

screenshots

faq

Q: Why?
A: Why not?

Q: Does it run Doom?
A: Not yet.

Q: Is the Win32 layer real?
A: Real enough to load binaries that expect it. Not real enough to run Notepad.

Q: Is the scheduler preemptive?
A: As much as it will ever be.

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

Q: Is this finished?
A: Not in the slightest.

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