Now custom instructions are directly on the regular instruction space... (+ there's the can of worms of target-specific MSRs being writable from user-space, Ap

Now custom instructions are directly on the regular instruction space... (+ there's the can of worms of target-specific MSRs being writable from user-space, Apple does this as part of APRR to flip the JIT region from RW- to R-X and vice-versa without going through a trip to the kernel. That also has the advantage that the state is modifiable per-thread)