CSharpMicrokernel

CSharpMicrokernel is an experimental microkernel operating system written primarily in C# (NativeAOT), supported by a minimal assembly + C bootstrap layer ("BootShim"). It is designed to run on bare-metal x86_64 hardware with no runtime dependencies, showcasing how modern managed languages can drive systems-level development.

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Vision

The project explores the fusion of managed language ergonomics with low-level OS engineering. By leveraging .NET NativeAOT, we achieve: - Zero runtime dependencies on the target --- no libc, no CoreCLR, no operating system. - Bare-metal execution: runs directly on hardware or emulators. - Microkernel architecture: only essential primitives in kernel space (scheduling, IPC, memory management), while services (console, FS, drivers) live in isolated modules.

This is not just a proof of concept --- it is a platform to experiment with modern language design in OS construction.

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Architecture Overview

┌───────────────┐
│   BootShim    │   Assembly + C
│  (boot.s)     │   CPU bring-up, GDT/IDT, paging, stack
└───────┬───────┘
        │
┌───────▼────────┐
│    Kernel C    │   kmain.c, VGA, IDT, Keyboard, PIT
└───────┬────────┘
        │
┌───────▼────────┐
│  ManagedCore   │   C# (NativeAOT)
│  Entry.cs      │   Scheduler, IPC, Shell, FS
└────────────────┘

• BootShim: Responsible for entering 64-bit long mode, building page tables, and handing off to C.
• C Layer: Initializes interrupts (IDT/PIC), timers, and hardware drivers. Bridges unmanaged world to managed world.
• ManagedCore (C#): Provides the microkernel's heart --- scheduler, interprocess communication (IPC), shell, and higher-level services.

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Current Features

• ✅ Multiboot2-compliant boot via GRUB\
• ✅ 64-bit long mode bring-up (assembly)\
• ✅ VGA text console output (C + C#)\
• ✅ IDT setup + PIC remap\
• ✅ PS/2 keyboard driver (IRQ1) feeding into C# shell\
• ✅ Interactive shell in C# with commands (help, cls, echo)

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Roadmap

• PIT timer + uptime counter\
• Cooperative → preemptive scheduler\
• Virtual memory manager with per-process address spaces\
• IPC (send/recv/reply) channels\
• Virtual File System (VFS) with RAMFS backend\
• Disk drivers + FAT32 filesystem\
• Networking (e1000 NIC driver + TCP/IP stack)\
• User-mode processes and isolation

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Build Instructions

Prerequisites

• Windows 10/11 with Visual Studio 2022

  • Workloads: Desktop Development with C++, .NET desktop development

• WSL2 (Ubuntu 22.04) (recommended) with:

  sudo apt update
  sudo apt install build-essential clang lld nasm make grub-pc-bin xorriso qemu-system-x86 dotnet-sdk-8.0

Build

# In WSL or Linux
make all

Run

make run

This will launch QEMU and boot the kernel ISO.

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📂 Repository Structure

CSharpMicrokernel/
├─ BootShim/          # Assembly + C bootstrap
│  ├─ boot/           # Assembly files (boot.s, gdt64.s, longmode.s)
│  ├─ kernel/         # C files (kmain.c, vga.c, idt.c, keyboard.c)
│  ├─ fs/             # Future: filesystem support
│  ├─ drivers/        # Future: hardware drivers
│  ├─ grub/           # grub.cfg
│  ├─ linker.ld       # Linker script
│  └─ Makefile
│
├─ ManagedCore/       # C# NativeAOT kernel logic
│  ├─ Kernel.csproj
│  ├─ Entry.cs
│  ├─ Vga.cs
│  ├─ Keyboard.cs
│  ├─ Shell.cs
│  └─ rd.xml
│
├─ build/             # Generated build outputs
└─ README.md

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