linux-kernel - Re: [REGRESSION] "efi: efistub: Convert into static library" and preparation patches

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Message-ID: <54078C74.2060804@zytor.com>
Date:	Wed, 03 Sep 2014 14:47:32 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matt Fleming <matt@...sole-pimps.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Ulf Winkelvos <ulf@...kelvos.de>,
	Matt Fleming <matt.fleming@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [REGRESSION] "efi: efistub: Convert into static library" and
 preparation patches

> 
> Any reason we can't reuse the existing GOT fixup code in the early x86
> boot code? We're not executing it before the EFI boot stub atm, which is
> the reason Maarten is hitting these difficulties.
> 
> Maarten, does the following help?
> 
> If not, Ard please go ahead with option #2 above. Overkill yes, but I've
> done the single __attribute__() hacks in other projects and someone
> (usually me) always eventually forgets to tag some instance.
> 

I think we really have two options: either fix up the GOT (which may be
a null operation, if the GOT is empty) or we add a compile-time check
that the GOT is empty, lest we will keep having these problems.

Since the GOT fixup loop is only a few instructions, it doesn't seem to
be all that problematic to just do it -- but make sure we don't end up
running it twice on any code path!

	-hpa

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