The llvm Cross-DSO CFI implementation depends on mremap, a syscall we currently lack. NetBSD provides an implementation, which we may be able to pull in.
Historically, HardenedBSD maintained syscall compatibility with FreeBSD. We should investigate ways to implement (or emulate) mremap such that we can use it in llvm's Cross-DSO CFI implementation. It would be preferred if we could keep syscall compat with FreeBSD.