linux-kernel - Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.64.1011081312570.29956@wotan.suse.de>
Date:	Mon, 8 Nov 2010 13:20:01 +0100 (CET)
From:	Michael Matz <matz@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Richard Guenther <richard.guenther@...il.com>,
	Andreas Schwab <schwab@...ux-m68k.org>, Jim <jim876@...all.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gcc@....gnu.org
Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

Hi,

On Mon, 8 Nov 2010, Andi Kleen wrote:

> Richard Guenther <richard.guenther@...il.com> writes:
> 
> > On Mon, Nov 8, 2010 at 12:03 AM, Andi Kleen <andi@...stfloor.org> wrote:
> >> Andreas Schwab <schwab@...ux-m68k.org> writes:
> >>>
> >>> The asm fails to mention that it modifies *regs.
> >>
> >> It has a memory clobber, that should be enough, no?
> >
> > No.  A memory clobber does not cover automatic storage.
> 
> That's a separate problem.
> 
> > Btw, I can't see a testcase anywhere so I just assume Andreas got
> > it right as usual.
> 
> An asm with live inputs and outputs should never be optimized
> way. If 4.5.1 started doing that it's seriously broken.

You know the drill: testcase -> gcc.gnu.org/bugzilla/

(In particular up to now it's only speculation in some forum that the asm 
really is optimized away, which I agree would be a bug, or if it isn't 
merely that regs->eax isn't reloaded after the asm(), which would be 
caused by the problem Andreas mentioned)


Ciao,
Michael.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/