Mach Kernel Abstractions and XNU Internals
Man is born free, and everywhere he is in chains. - Jean-Jacques Rousseau; The Social Contract
Search for the truth is the noblest occupation of man; its publication is a duty. - Anne Louise Germaine de Staël; De l'Allemagne
Preamble: XNU and the Mach Kernel
An operating system is a set of system software that acts as a bridge between the application software and the underlying hardware. Among the various software packaged with an operating system is the kernel — a program responsible for communicating with the hardware and managing the system in its entirety. The purpose of this post is to explore the XNU kernel source and understand the core abstractions of the Mach kernel that underpin the macOS kernel architecture. We'll walk through Mach's taxonomy — tasks, threads, IPC ports, processor sets — and examine the XNU-specific implementation details, including pointer authentication and key Mach routines like task_info and mach_task_self.