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Date:   Thu, 25 Jan 2018 12:32:28 -0600
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     David Woodhouse <dwmw2@infradead.org>
Cc:     Borislav Petkov <bp@alien8.de>, tim.c.chen@linux.intel.com,
        pjt@google.com, jikos@kernel.org, gregkh@linux-foundation.org,
        dave.hansen@intel.com, mingo@kernel.org, riel@redhat.com,
        luto@amacapital.net, torvalds@linux-foundation.org,
        ak@linux.intel.com, keescook@google.com, peterz@infradead.org,
        tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org,
        linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/pti] x86/retpoline: Fill return stack buffer on vmexit
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On Thu, Jan 25, 2018 at 06:04:23PM +0000, David Woodhouse wrote:
> On Thu, 2018-01-25 at 18:53 +0100, Borislav Petkov wrote:
> > 
> > So forget the KABI angle and think: simpler, cleaner, more readable
> > macros.
> > 
> > Oh, and David, if while doing so I manage to add the alignment, then
> > *that* is even better.
> > 
> > Win-win-effing-win situation!
> 
> Yep, I'll buy that. But first we need Josh to work out what he's having
> for lunch.

This is what I've been eating every day:

  https://www.urbandictionary.com/define.php?term=Shit%20Sandwich

:-)

> Although just another marker to tell objtool "ignore this whole
> function" might be sufficient to allow us to have an out-of-line RSB-
> stuffing function.

If the function is only in arch/x86/lib/retpoline.S, we can just tell
objtool to ignore the entire file for now, as the file has no useful
information anyway (until I get around to adding ORC hints to it).  Just
add

  OBJECT_FILES_NON_STANDARD_retpoline.o :=y
  
to the Makefile.

-- 
Josh