From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "Måns Rullgård" <mans@mansr.com>,
"Jon Masters" <jonathan@jonmasters.org>,
netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: alignment faults in 3.6
Date: Thu, 11 Oct 2012 09:53:02 +0100 [thread overview]
Message-ID: <20121011085302.GM4625@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <AE90C24D6B3A694183C094C60CF0A2F6026B7038@saturn3.aculab.com>
On Thu, Oct 11, 2012 at 09:21:35AM +0100, David Laight wrote:
> It might be enough to use __attribute__((aligned(2))) on some structure
> members (actually does 'ldm' need 8 byte alignment?? - in which case
> aligned(4) is enough).
No, ldm just needs 4 byte alignment, the same as normal word loads/stores
not to fault. The only instructions which needs 8 byte alignment not to
fault are the double-word load/stores.
> One on my bugbears is hardware that will once receive ethernet frames
> onto a 4n boundary - it needs to be 4n+2. two bytes of 'junk' will do.
Indeed, but remember that is just a mere optimisation for IPv4. What
may be true of IPv4 is not necessarily true of other protocols, though
IPv4 is currently the dominant protocol today. IPv6 follows the same
alignment rules as IPv4, so it's unlikely to change.
next prev parent reply other threads:[~2012-10-11 8:53 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
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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 [this message]
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
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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