Re: [PATCH 2/3] objtool: Ignore retpoline alternatives

[David Woodhouse]

On Thu, 2018-01-11 at 18:05 +0100, Peter Zijlstra wrote:
> On Thu, Jan 11, 2018 at 06:01:23PM +0100, Jiri Kosina wrote:
> > On Thu, 11 Jan 2018, Josh Poimboeuf wrote:
> >Â
> > > I think I heard that retpolines won't be ported to anything older thanÂ
> > > GCC 4.9, so maybe it's safe to use '%='. I don't remember when it wasÂ
> > > introduced into GCC though.
> >Â
> > I'm afraid we'll have to backport retpolines in some form to 4.3.x atÂ
> > least. I'd be surprised if we'd be the only ones on this planet :)
> 
> So upstream code is going to require 4.5 at least, and 4.4 has %=.
> Backport effort will just have to cope or backport more GCC bits, that
> is, if you're backporting retpoline to 4.3 also backport asm-goto.

Again, the RSB thing is for more than just retpoline; it's needed for
IBRS support too and that *doesn't* necessarily require a newer
compiler at all.

But really, if %= is supported at least as far back as 4.4 (and maybe
further?) then I'm not going to care about it unless someone really
screams.

I think we're fairly much done, unless Andi you really want to make the
RSB stuffing code out-of-line?

Thomas, do you want to leave Josh's patches on top with a revert, as
they are at the moment in my tree, or rebase and fold them in as we go?

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