NeptuneOS

Features

• Implements the Windows NT Executive as a userspace process on the seL4 microkernel.

• Exposes the NT Native API (Nt*) via stub functions in a custom NTDLL.DLL.

• Runs device drivers in separate userspace processes to enhance system isolation and security.

• Provides a complete storage driver stack including classpnp.sys, disk.sys, and storport.sys.

• Supports high-performance storage interfaces through AHCI and NVMe miniport drivers.

• Features a FAT12/16/32 file system driver with integrated read-ahead and write-back caching.

• Includes an Object Manager for managing system resources with support for symbolic links and parsing.

• Implements a Cache Manager that ensures consistent file access across different process boundaries.

• Supports Structured Exception Handling (SEH) for robust kernel-mode and user-mode error recovery.

• Provides a Configuration Manager that implements a volatile registry for hardware configuration.

• Includes a DMA subsystem supporting ISA slave DMA, PCI bus mastering, and software scatter/gather.

• Supports UEFI booting with high-definition GOP linear framebuffer rendering for the text console.

• Implements Local Procedure Call (LPC) port objects as thin wrappers over seL4 endpoint primitives.

• Features a PNP root enumerator and ACPI/PCI bus drivers for automated device discovery.

• Includes a POSIX subsystem shim allowing for the execution of basic Unix-like utilities.

• Supports i686, x86_64, and AArch64 architectures with specific optimizations like fsgsbase and global pages.

Neptune OS utilizes a microkernel architecture where the seL4 microkernel serves as the foundational layer, handling low-level hardware abstraction, thread scheduling, and Inter-Process Communication (IPC). The core of the operating system is the “NT Executive,” which runs as the seL4 root task in userspace. This component implements the high-level semantics of Windows NT, including the Object Manager, Process Manager, and IO Manager. By moving these traditionally kernel-space services into userspace, Neptune OS leverages seL4’s capability-based security model to isolate system components.

Communication between the NT Executive and other system components, such as device drivers and environment subsystems, is performed using I/O Request Packets (IRPs) serialized over seL4 IPC. Device drivers in Neptune OS are standalone processes, a departure from the monolithic Windows model, which prevents a single driver failure from compromising the entire system. The architecture is designed to be binary compatible with native Windows executables by providing a faithful implementation of the NT Native API via NTDLL.

Core Components

• Object Manager (Ob): Manages the system namespace, handle tables, and object lifetimes.
• IO Manager (Io): Orchestrates IRP-based communication between clients and drivers.
• Cache Manager (Cc): Provides a centralized caching mechanism for file systems and block devices.
• Process Manager (Ps): Handles process and thread creation, mapping NT concepts to seL4 primitives.
• Configuration Manager (Cm): Manages the system registry and hardware configuration database.

Use Cases

This RTOS is ideal for:

• Secure Systems Research: Leveraging the formal verification of seL4 while providing a familiar Windows-like environment for application development.
• Legacy Driver Isolation: Running ported Windows or ReactOS drivers in isolated userspace environments to prevent system-wide crashes.
• Embedded Windows Personalities: Deploying lightweight, NT-compatible environments on hardware where a full Windows installation is not feasible.
• Microkernel Performance Benchmarking: Evaluating the overhead of NT-style IRP processing and system calls in a client-server microkernel model.

Getting Started

To begin developing for Neptune OS, you must have a Linux-based build environment with the LLVM toolchain (Clang/LLD) and Python dependencies installed. The project uses a unified build script, build.sh, which orchestrates the compilation of the seL4 kernel, the NT Executive, and various PE-format drivers and utilities. Developers should clone the repository with submodules to include the seL4 source. Detailed architectural documentation and a driver porting guide are available in the docs/ directory, specifically within the Developer-Guide.md file. For testing, the project provides run.sh to launch the OS in QEMU with support for direct kernel loading, ISO, or UEFI boot modes.