From: Arnd Bergmann <arnd@arndb•de>
To: linux-arm-kernel@lists•infradead.org
Cc: "Eric Dumazet" <eric.dumazet@gmail•com>,
"Russell King - ARM Linux" <linux@arm•linux.org.uk>,
"Jon Masters" <jonathan@jonmasters•org>,
netdev@vger•kernel.org, "Måns Rullgård" <mans@mansr•com>,
"David Laight" <David.Laight@aculab•com>,
"Rob Herring" <robherring2@gmail•com>
Subject: Re: alignment faults in 3.6
Date: Thu, 11 Oct 2012 12:28:25 +0000 [thread overview]
Message-ID: <201210111228.25995.arnd@arndb.de> (raw)
In-Reply-To: <1349952574.21172.8604.camel@edumazet-glaptop>
On Thursday 11 October 2012, Eric Dumazet wrote:
> On Thu, 2012-10-11 at 11:32 +0100, Russell King - ARM Linux wrote:
> > On Thu, Oct 11, 2012 at 12:22:06PM +0200, Eric Dumazet wrote:
> > > I took a look, and I dont see why/how gcc could use a ldm instruction
> > >
> > > Doing so assumed the alignment of the structure was 8 bytes, but its
> > > not.
> > >
> > > Networking stack mandates that IP headers are aligned on 4 bytes
> > > boundaries, not 8 bytes.
> >
> > Err, no. ldm is "load multiple" not "load double". It loads multiple
> > 32-bit registers, and its requirement for non-faulting behaviour is for
> > the pointer to be 4 byte aligned. However, "load double" requires 8
> > byte alignment.
>
> So if you have an alignment fault, thats because IP header is not
> aligned on 4 bytes ?
>
> If so a driver is buggy and must be fixed.
>
> Please send us full stack trace
Rob Herring as the original reporter has dropped off the Cc list, adding
him back.
I assume that the calxeda xgmac driver is the culprit then. It uses
netdev_alloc_skb() rather than netdev_alloc_skb_ip_align() in
xgmac_rx_refill but it is not clear whether it does so intentionally
or by accident.
Arnd
next prev parent reply other threads:[~2012-10-11 12:28 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <506E1762.3010601@gmail.com>
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[not found] ` <20121005071216.GD4625@n2100.arm.linux.org.uk>
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[not found] ` <507619FA.6080001@jonmasters.org>
2012-10-11 2:27 ` alignment faults in 3.6 Måns Rullgård
2012-10-11 2:34 ` Jon Masters
2012-10-11 8:21 ` David Laight
2012-10-11 8:53 ` Russell King - ARM Linux
2012-10-11 9:45 ` Måns Rullgård
2012-10-11 10:00 ` Eric Dumazet
2012-10-11 10:20 ` Måns Rullgård
2012-10-11 10:22 ` Eric Dumazet
2012-10-11 10:32 ` Russell King - ARM Linux
2012-10-11 10:49 ` Eric Dumazet
2012-10-11 10:56 ` Maxime Bizon
2012-10-11 11:28 ` Eric Dumazet
2012-10-11 11:47 ` Maxime Bizon
2012-10-11 11:54 ` Eric Dumazet
2012-10-11 12:00 ` Eric Dumazet
2012-10-11 12:51 ` Maxime Bizon
2012-10-11 12:59 ` Eric Dumazet
2012-10-11 12:28 ` Arnd Bergmann [this message]
2012-10-11 12:40 ` Eric Dumazet
2012-10-11 13:20 ` Rob Herring
2012-10-11 13:32 ` Måns Rullgård
2012-10-11 13:35 ` Arnd Bergmann
2012-10-11 13:47 ` Eric Dumazet
2012-10-11 15:23 ` Rob Herring
2012-10-11 15:39 ` David Laight
2012-10-11 16:18 ` Måns Rullgård
2012-10-12 8:11 ` Arnd Bergmann
2012-10-12 9:03 ` Russell King - ARM Linux
2012-10-12 10:04 ` Eric Dumazet
2012-10-12 12:24 ` Russell King - ARM Linux
2012-10-12 11:00 ` Måns Rullgård
2012-10-12 11:07 ` Russell King - ARM Linux
2012-10-12 11:18 ` Måns Rullgård
2012-10-12 11:44 ` Russell King - ARM Linux
2012-10-12 12:08 ` Eric Dumazet
2012-10-12 14:22 ` Benjamin LaHaise
2012-10-12 14:36 ` David Laight
2012-10-12 14:48 ` Eric Dumazet
2012-10-12 15:00 ` Benjamin LaHaise
2012-10-12 15:04 ` Ben Hutchings
2012-10-12 15:47 ` David Laight
2012-10-12 16:13 ` Ben Hutchings
2012-10-12 12:16 ` Måns Rullgård
2012-10-12 11:19 ` Russell King - ARM Linux
2012-10-11 16:15 ` Eric Dumazet
2012-10-11 16:59 ` Catalin Marinas
2012-10-11 10:16 ` David Laight
2012-10-11 10:46 ` Måns Rullgård
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