Hurd on XNU

Running GNU Hurd userspace on Apple's XNU kernel

Overview

This project ports GNU Hurd's microkernel-based userspace to run on Apple's XNU kernel, combining:

• XNU: Apple's hybrid kernel (Mach + BSD) with modern hardware support
• Hurd: GNU's microkernel OS with translator-based architecture

Current Status (v0.3-alpha) 🎉

Core Servers (5)

Server	Status	Description
auth	✅ Working	Authentication with root handle
proc	✅ Working	Process management, PID/task conversion
exec	✅ Working	ELF execution (stubbed)
pfinet	✅ Working	Network (BSD socket wrapper)
ext2fs	✅ Working	Filesystem (POSIX wrapper)

Translators (4)

Translator	Status	Description
term	✅ Working	PTY + console (/dev/ttys*)
symlink	✅ Working	Symbolic links
devnull	✅ Working	/dev/null, zero, full, random, urandom
tmpfs	✅ Working	In-memory filesystem (64MB)

Bootstrap & Init

Component	Status	Description
startup	✅ Working	Essential task registration, shutdown notify
init	✅ Working	Runlevel 0-3, service ordering
bootstrap	✅ Working	Server startup management

Driver Layer

Component	Status	Description
rumpuser	✅ Working	NetBSD Rump hypercalls for XNU
machdev	✅ Working	Mach device layer compatibility
rumpdisk	✅ Working	Block devices (wd0, wd1)
rumpnet	✅ Working	Network interfaces (eth0, lo0)
LKL bridge	✅ Working	Linux Kernel Library integration

Integration Testing

═══════════════════════════════════════════════════════════
   TEST SUMMARY
═══════════════════════════════════════════════════════════
   Passed: 27
   Failed: 0
   Total:  27
═══════════════════════════════════════════════════════════
🎉 ALL USERSPACE TESTS PASSED!

Quick Start

Prerequisites

• macOS (tested on Sequoia 15.x, M4 Mac)
• Xcode Command Line Tools
• QEMU (optional, for boot testing)

Build & Test

# Clone
git clone --recursive https://github.com/J-x-Z/hurd-xnu
cd hurd-xnu

# Build all tests
make tests

# Run userspace integration test (27 tests)
./tests/userspace_test

# Run individual translator tests
./compat/term_test
./compat/tmpfs_test
./compat/devnull_test

Architecture

┌─────────────────────────────────────────────────────────┐
│                  Hurd Userspace Tests                   │
│    (shell, coreutils, network, multi-user, PTY)        │
├─────────────────────────────────────────────────────────┤
│                     Translators                         │
│      term │ symlink │ devnull │ tmpfs                   │
├─────────────────────────────────────────────────────────┤
│                    Core Servers                         │
│    auth │ proc │ exec │ pfinet │ ext2fs │ startup      │
├─────────────────────────────────────────────────────────┤
│               Bootstrap / Init                          │
│         hurd_bootstrap.c │ init_xnu.c                  │
├─────────────────────────────────────────────────────────┤
│                   Driver Layer                          │
│    rumpuser │ machdev │ LKL bridge                     │
├─────────────────────────────────────────────────────────┤
│              Compatibility Layer                        │
│    libports │ MIG stubs │ mach.h │ ports.h             │
├─────────────────────────────────────────────────────────┤
│                    XNU Kernel                           │
│         (Mach microkernel + BSD + IOKit)               │
└─────────────────────────────────────────────────────────┘

Directory Structure

hurd-xnu/
├── compat/                 # XNU compatibility layer (~6000 lines)
│   ├── auth_xnu.c          # Auth server
│   ├── proc_xnu.c          # Proc server
│   ├── exec_xnu.c          # Exec server
│   ├── pfinet_xnu.c        # Network server
│   ├── ext2fs_xnu.c        # Filesystem translator
│   ├── startup_xnu.c       # Startup server
│   ├── init_xnu.c          # Init process
│   ├── hurd_bootstrap.c    # Bootstrap manager
│   ├── term_xnu.c          # Terminal translator
│   ├── symlink_xnu.c       # Symlink translator
│   ├── devnull_xnu.c       # /dev/null, zero, random
│   ├── tmpfs_xnu.c         # In-memory filesystem
│   ├── rumpuser_xnu.c      # Rump hypercalls
│   ├── machdev_xnu.c       # Mach device layer
│   ├── lkl_hurd_bridge.c   # LKL integration
│   ├── mach.h              # Mach type definitions
│   ├── ports.h             # libports interface
│   └── hurd/               # MIG .defs files
├── tests/                  # Test programs
│   ├── hurd_userspace_test.c  # Integration test (27 tests)
│   └── rump_integration_test.c
├── hurd/                   # Original Hurd source (submodule)
├── xnu/                    # XNU kernel source (submodule)
└── qemu/                   # QEMU boot infrastructure

Roadmap

• Phase 1-5: Environment, Mach IPC, libports, QEMU boot ✅
• Phase 6: Core Hurd servers (auth, proc, exec, pfinet, ext2fs) ✅
• Phase 7: Rump Kernels (rumpdisk, rumpnet) ✅
• Phase 8: Bootstrap + Startup + Init ✅
• Phase 9: Translators (term, symlink, devnull, tmpfs) ✅
• Phase 10: Userspace integration (27/27 tests) ✅
• Phase 11: Bare metal Hurd on XNU (launchd, Kext, boot image)

Code Statistics

Category	Files	Lines
Core Servers	6	~1,400
Translators	4	~950
Bootstrap/Init	3	~720
Driver Layer	5	~1,600
Compatibility	10+	~1,500
Tests	5+	~800
Total	30+	~7,000

Related Projects

• GNU Hurd
• XNU Source
• PureDarwin
• NetBSD Rump Kernel
• Linux Kernel Library (LKL)

License

• Hurd components: GPL-2.0
• XNU: APSL-2.0
• This compatibility layer: GPL-2.0

Contributing

This is an experimental research project. Contributions welcome!

1. Fork this repository
2. Create a feature branch
3. Submit a Pull Request

Acknowledgments

• GNU Hurd developers
• Apple XNU team (open source kernel)
• OSX-KVM / DarwinKVM communities
• NetBSD Rump and LKL projects