linux-kernel - Re: Urgent: x86-32 and GNU ld 2.22.52.0.1

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Message-ID: <20120519102041.GA22271@gmail.com>
Date:	Sat, 19 May 2012 12:20:41 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Josh Boyer <jwboyer@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "H.J. Lu" <hjl.tools@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>
Subject: Re: Urgent: x86-32 and GNU ld 2.22.52.0.1


* Josh Boyer <jwboyer@...il.com> wrote:

> On Fri, May 18, 2012 at 12:20 PM, H. Peter Anvin <hpa@...or.com> wrote:
> > On 05/18/2012 09:14 AM, H.J. Lu wrote:
> >> On Fri, May 18, 2012 at 8:56 AM, H. Peter Anvin <hpa@...or.com> wrote:
> >>> I need an urgent opinion.  It seems we have an epic mess on our hands.
> >>>
> >>> GNU ld 2.22.52.0.1 silently changed the semantics of section-relative
> >>> symbols that are part of otherwise empty sections, and silently changes
> >>> them to absolute.  We rely on section-relative symbols staying
> >>> section-relative, and actually have several sections in the linker
> >>> script solely for this purpose.
> >>
> >> That is I talked to you a couple days ago:
> >>
> >> http://sourceware.org/bugzilla/show_bug.cgi?id=14052
> >>
> >
> > I know, which was a very good thing... otherwise we'd probably not have
> > tracked this down anywhere near as quickly.  Thank you.
> >
> > The problem is that this version of binutils made it into Fedora 17, and
> > so we now have a large number of users with a known bad binutils in the
> > field...
> 
> We've not seen many kernel bugs that would seem to be blamed 
> on this as of yet.  It does seem like a problem waiting to hit 
> us once F17 goes GA though.  My limited 32-bit F17 machine 
> collection definitely shows the __init_{begin,end} symbols 
> being absolute, but they boot fine.  Likely because the kernel 
> isn't relocated on them.

Relocation is rare, it typically happens with crashdump kernels.

Thanks,

	Ingo
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