Re: PROPOSAL: Extend inline asm syntax with size spec

From: Segher Boessenkool
Date: Wed Oct 10 2018 - 15:55:05 EST

On Wed, Oct 10, 2018 at 10:19:06AM +0200, Borislav Petkov wrote:
> On Wed, Oct 10, 2018 at 03:03:25AM -0500, Segher Boessenkool wrote:
> > The code immediately after this makes it size 1, even for things like
> > asm(""), I suppose this works better for the inliner. But that's a detail
> > (and it might change); the description says "consider this asm as minimum
> > length and cost for inlining decisions", which works for either 0 or 1.
> Thanks for implementing this, much appreciated. If you need people to
> test stuff, lemme know.

It would be great to hear from kernel people if it works adequately for
what you guys want it for :-)

> > You can think of it as meaning "we want this asm inlined always", and then
> > whether that actually happens depends on if the function around it is
> > inlined or not.
> My only concern is how we would catch the other extremity where the
> inline asm grows too big and we end up inlining it everywhere and thus
> getting fat. The 0day bot already builds tinyconfigs but we should be
> looking at vmlinux size growth too.

But this isn't really different from other always_inline concerns afaics?
So you should be able to catch it the same way, too.