[mike_hearn]

Oracle Labs has tech that does that:

https://youtu.be/T05FI93MBI8?si=EieFgujaGiW2gbO8&t=958

The trick is to do a cascading disassembly of all untrusted code you'll execute to prove it can't change the MPK register.

[twoodfin]

Wow. Neat trick and exactly the kind of thing I was looking for.

Thanks!

EDIT: Looks like this is the relevant paper from the Graal team: https://www.graalvm.org/resources/articles/binsweep.pdf