Ringing in a new asynchronous I/O API

We're in "passing massive structures and/or arrays of structures" land, and trying to *not* produce a horror show like perf_event_open() is fairly high on my priority list! (Though, really, arguing against myself: the reason perf_event_open() is horrifying is that it does a lot, and honestly the same would be true of any attempt to wrap it in a uring, or in anything else. It's not really a win to move from 'this ioctl/syscall has security holes because the interface has too many edges to test exhaustively' to 'this uringed interface has security holes because the interface has too many edges to test exhaustively', alas. :( )