I had some success in porting Wine to amd64.OpenBSD. Was able to run a few games. But that required in memory patching of %gs commands (LLM's suggestion and 1st implementation, then I re-did it from scratch - I'm not that smart with amd64 assembly code) and no one in upstream WINE will want to take it. Mostly because of a heavy support burden - it's about 800 lines of code just for OpenBSD.

If OpenBSD adds ability to set %gs - those 800 lines disappear.

But as a fresh tourist (half year watcher, few days writer) I understand the security goals and was just was interested about the idea behind %gs.

> I thought WINE had an additional requirement that page 0 of a process be mappable.

In OpenBSD userland %gs always maps to 0, so any time WINE tries to get TEB it faults - that was the way how I was able to patch it to point at %fs base + teb_tls_offset at first fault. This way performance does not suffer after the first run.