What I'm curious about is whether there's a good writeup of what you need to do to handle the (presumably) ASLR that OpenBSD has.

I've been having a hell of a time figuring out what's going on when I try to port Myrddin -- the code I generate will often segfault, on a string that GDB seems to think is perfectly valid, and happily prints. Some of the strings have clearly wonky addresses, (eg, within the zero page), others don't look insane.