Deep Dive into Apple's XNU Kernel Exclave Architecture
This article delves into the secure enclave architecture within Apple's XNU kernel. Exclaves manage resources via a two-level kernel table structure, encompassing domains (e.g., com.apple.kernel) each containing multiple resources (services, buffers). Conclaves, a special resource type, enable shared access among services, controlled by a Conclave Manager. A new _exclaves_ctl_trap() system call manages various Exclave operations, including launching conclaves, looking up services, and executing downcalls (secure world code execution). Upcalls allow secure world code to invoke specific XNU kernel functions. The article details the three-stage Exclave boot process and how the SPTM memory typing system controls Exclave memory access.