From: David Daney <ddaney@caviumnetworks.com>
To: Felix Fietkau <nbd@openwrt.org>
Cc: netdev@vger.kernel.org, Lennert Buytenhek <buytenh@wantstofly.org>
Subject: Re: [PATCH] skbuff: align sk_buff::cb to 64 bit
Date: Fri, 29 Jan 2010 14:42:03 -0800 [thread overview]
Message-ID: <4B63643B.3070400@caviumnetworks.com> (raw)
In-Reply-To: <4B635CA1.8070803@openwrt.org>
Felix Fietkau wrote:
> The alignment requirement for 64-bit load/store instructions on ARM is
> implementation defined. Some CPUs (such as Marvell Feroceon) do not
> generate an exception, if such an instruction is executed with an
> address that is not 64 bit aligned.
> In such a case, the Feroceon corrupts adjacent memory, which showed up
> in my tests as a crash in the rx path of ath9k that only occured with
> CONFIG_XFRM set. This crash happened, because the first field of the
> mac80211 rx status info in the cb is an u64, and changing it corrupted
> the skb->sp field.
>
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> Cc: stable@kernel.org
> ---
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -329,7 +329,7 @@ struct sk_buff {
> * want to keep them across layers you have to do a skb_clone()
> * first. This is owned by whoever has the skb queued ATM.
> */
> - char cb[48];
> + char cb[48] __attribute__((aligned(8)));
>
s/__attribute__((aligned(8)))/__aligned(8)/
Could the same thing be achieved by swapping the order of the dev and
tstamp fields instead of adding the alignment attribute?
What is the sizeof(void *) on this thing?
David Daney
next prev parent reply other threads:[~2010-01-29 22:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-29 22:09 [PATCH] skbuff: align sk_buff::cb to 64 bit Felix Fietkau
2010-01-29 22:42 ` David Daney [this message]
2010-01-29 22:54 ` Edgar E. Iglesias
2010-01-29 23:14 ` Felix Fietkau
2010-01-29 23:09 ` Felix Fietkau
2010-01-30 1:41 ` Lennert Buytenhek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4B63643B.3070400@caviumnetworks.com \
--to=ddaney@caviumnetworks.com \
--cc=buytenh@wantstofly.org \
--cc=nbd@openwrt.org \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).