Curated source guide

XNU source explorer

Explore Apple's XNU kernel source code interactively. Study Mach IPC, virtual memory, I/O Kit drivers, BSD internals, and the hybrid kernel architecture behind macOS and iOS.

Guide chapters

1. Chapter 1 — A Kernel of Three Minds
2. Chapter 2 — Mach Primitives
3. Chapter 3 — Virtual Memory as a Mach Contract
4. Chapter 4 — BSD Over Mach
5. Chapter 5 — VFS and the Vnode
6. Chapter 6 — I/O Kit and the Driver Model

Key directories

• osfmk/mach/ — Mach type definitions visible to user space
• osfmk/kern/ — Kernel startup — Mach subsystem initialization sequence
• bsd/kern/ — BSD layer initialization — POSIX personality brought online
• iokit/Kernel/ — I/O Kit startup — C++ runtime and driver matching begins
• osfmk/ — Mach kernel core: tasks, threads, IPC, VM, scheduler, and architecture glue.
• bsd/ — POSIX and Unix layer: processes, syscalls, networking, VFS, credentials, and signals.