This looks sane to me, although I'm surprised that we didn't already have an annotation for the nonstandard stack frame for asm files. That probably would be cleaner in a separate commit, but I guess it doesn't matter.
Anyway, I'm willing to consider the entry code version if it looks a _lot_ simpler than this (so I'd like to see them side-by-side), but it's not like this looks all that complicated to me either.
Linus