I guess my mental estimate of last having looked "about 6 months ago" was off by a little bit. I think this weekend might be dedicated to writing a Rust kernel. Thanks for your hard work!

No problem. Like I said, we're very interested in making this use-case better, so please file any odd things that crop up. Oh, and there's #rust-osdev on mozilla's IRC where friendly people idle.

I suspect that the overwhelming majority of cases that warrant inline assembly would not benefit if it was instead a function call out to something you've linked in. That is, most inline assembly is a small snippet of optimized code that necessarily exists in the function you're optimizing.

Yeah, as always, when we're considering stabilizing or removing something, we talk to who is using the feature and in what way, and these kinds of issues surface.

That is why naked and inline exist for.

Inline from C libraries won't -- as far as I'm aware -- inline into a Rust function. Inline is a compile-time hint, not a link-time behavior. In theory this could be changed in LLVM, but it seems really unlikely to me. The function exposed from C (with the inline asm) can be naked, though, assuming you are hygienic.

Yeah, but that is a consequence of not having a Rust aware linker and relying on one that basically uses C semantics.

Languages that use their own linkers tend to have better opportunities for code optimization during linking.