TIL: you can enable alignment checks on x86 with the AC flag. Bonus: "This allows explicit supervisor-mode data accesses to user-mode pages even if the SMAP bit is set in the CR4 register." https://xem.github.io/minix86/manual/intel-x86-and-64-manual-vol3/o_fe12b1e2a880e0ce-231.html … and https://www.felixcloutier.com/x86/stac
Isn't it related to the issue found by @m00nbsd in OpenBSD around 2017 ? Basically the AC flag was not reset properly after a syscall or interrupt, neutering SMAP entirely.
https://flak.tedunangst.com/post/openbsd-changes-of-note-628 …
I would be tempted to say "old" 