linux-kernel - Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)

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: <48A9BF9C.80108@freescale.com>
Date:	Mon, 18 Aug 2008 13:29:48 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Steven Rostedt <srostedt@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Eran Liberty <liberty@...ricom.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)

Steven Rostedt wrote:
>> Should use a "b" constraint for %2, or you could get r0. 
> 
> I will make an updated patch.
> 
>> Or, use an "m"
>> constraint with %U2%X2 after the lwz/stw. 
> 
> The 'b' seems easier ;-)

The advantage of the latter is that it allows GCC to choose indexed or 
update instructions -- but that's merely an optimization.  Switching to 
"b" is enough to avoid the potential bug.

>> %1 also needs to be an early clobber.
> 
> Not exactly sure what you mean by the above.

%1 is written to before some inputs are consumed, so you need to use 
"=&r" rather than "=r" so that GCC won't use the same register for both.

-Scott
--
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/