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Re: alignment issues on netif_rx

To: Andi Kleen <ak@xxxxxx>
Subject: Re: alignment issues on netif_rx
From: Jes Sorensen <jes@xxxxxxxxxxxxx>
Date: 18 Dec 2000 16:30:52 +0100
Cc: Johannes Erdfelt <johannes@xxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxx>, kai@xxxxxxxxxxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx
In-reply-to: Andi Kleen's message of "Sun, 17 Dec 2000 22:36:12 +0100"
References: <Pine.LNX.4.10.10012151332190.32035-100000@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <200012151606.IAA20579@xxxxxxxxxxxxxxx> <20001216135124.A1045@xxxxxxxxxxxx> <20001217223612.A985@xxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
User-agent: Gnus/5.070096 (Pterodactyl Gnus v0.96) Emacs/20.4
>>>>> "Andi" == Andi Kleen <ak@xxxxxx> writes:

Andi> On Sun, Dec 17, 2000 at 04:21:14PM +0100, Johannes Erdfelt
Andi> wrote:
>>  However, I can't imagine we've made it this long without this
>> being a problem so there must be something I'm missing.

Andi> Nobody apparently tried to use IPX on IA64 yet (due to a
Andi> different ethernet header length it usually has to deal with an
Andi> misaligned header)

Andi> With this there are also plenty of ways to crash an IA64 box
Andi> remotely, e.g. by putting misaligned timestamps into options.

I have been thinking about adding mis-word-aligned read/write macros
to the networking code for this reason. Ie. less generic macros that
will load half words and merge them instead of the very generic
misaligned load macros. This way architectures that do not have a
problem with misaligned word loads but do have mis aligned byte loads
can optimize it away.

I think some of the Alphas have the alignment problems as well.


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