I believe it's being returned by the FS driver, not mmap() necessarily. I think I knew what instruction it was when I was debugging it but don't remember right now. (I could probably dig through my LLM history and get it though.)

And yeah, I knew AI is useless, I try to avoid it, but when I'm way over my head it's better than nothing (it did lead me to the workaround that I mentioned in my previous comment).