From: davem@davemloft.net (David Miller)
To: linux-arm-kernel@lists.infradead.org
Subject: ARM unaligned MMIO access with attribute((packed))
Date: Wed, 02 Feb 2011 13:59:54 -0800 (PST) [thread overview]
Message-ID: <20110202.135954.189712480.davem@davemloft.net> (raw)
In-Reply-To: <20110202214522.GG31043@n2100.arm.linux.org.uk>
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Wed, 2 Feb 2011 21:45:22 +0000
> On Wed, Feb 02, 2011 at 01:38:31PM -0800, David Miller wrote:
>> From: Russell King - ARM Linux <linux@arm.linux.org.uk>
>> Date: Wed, 2 Feb 2011 16:37:02 +0000
>>
>> > 1. there's no way to tell GCC that the inline assembly is a load
>> > instruction and therefore it needs to schedule the following
>> > instructions appropriately.
>>
>> Just add a dummy '"m" (pointer)' asm input argument to the inline asm
>> statement. Just make sure "typeof(pointer)" has a size matching the
>> size of the load your are performing.
>
> That involves this problematical cast from a packed struct pointer to
> an unsigned long pointer, which according to the C standard and GCC
> folk is undefined.
It's alignment may be undefined, but it's size definitely is well
defined and that's what matters here.
> Practice over the last 15 years on ARM has also shown that this is not
> necessary.
Sorry oh big super man, little ole' me is only a kernel newbie.
next prev parent reply other threads:[~2011-02-02 21:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-02 16:00 ARM unaligned MMIO access with attribute((packed)) Arnd Bergmann
2011-02-02 16:37 ` Russell King - ARM Linux
2011-02-02 17:39 ` Arnd Bergmann
2011-02-02 19:14 ` Ian Lance Taylor
2011-02-02 21:38 ` David Miller
2011-02-02 21:45 ` Russell King - ARM Linux
2011-02-02 21:59 ` David Miller [this message]
[not found] ` <yw1xei7qm3vy.fsf@unicorn.mansr.com>
2011-02-02 23:23 ` David Miller
2011-02-03 9:26 ` Arnd Bergmann
2011-02-03 15:03 ` Arnd Bergmann
2011-02-02 16:51 ` Richard Guenther
2011-02-02 17:09 ` Russell King - ARM Linux
2011-02-02 17:39 ` Joseph S. Myers
2011-04-26 15:00 ` Rabin Vincent
2011-04-26 18:51 ` Alan Stern
2011-04-27 14:06 ` Rabin Vincent
2011-04-27 16:25 ` Alan Stern
2011-04-27 16:37 ` Arnd Bergmann
2011-04-28 13:35 ` Alan Stern
2011-04-28 14:16 ` Arnd Bergmann
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