linux-kernel - Re: kernel unaligned accesses on 2.6.29.

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Date:	Tue, 24 Mar 2009 20:14:18 -0500
From:	Robin Holt <holt@....com>
To:	Chuck Lever <chuck.lever@...cle.com>, tony.luck@...el.com
Cc:	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: kernel unaligned accesses on 2.6.29.

Had a few minutes to look around.

On Tue, Mar 24, 2009 at 12:28:57PM -0500, Robin Holt wrote:
> I just built and booted an ia64 2.6.29 kernel.  While accessing NFS
> filesystems, I occassionally get:
> 
> kernel unaligned access to 0xe00007bc3b8f67b9, ip=0xa00000020a61e370
> kernel unaligned access to 0xe00007bc3b8f67b1, ip=0xa00000020a61e3d1
> 
> grep a00000020a61 /proc/modules
> lockd 146448 1 nfs, Live 0xa00000020a610000
> 
> 
> These come in pairs.  I tracked it down to the lockd.ko kernel module
> and then objdump'd to find we are in:
> 
> 
> nsm_get_handle
> nsm_init_private():
> /data/lwork/attica2/holt/git-linus/v2.6.29/fs/lockd/mon.c:280
>     e370:       0b 00 98 68 98 11       [MMI]       st8 [r52]=r38;;

This one is:
	u64 *p = (u64 *)&nsm->sm_priv.data;
	...
	*p = (unsigned long)nsm;

sm_priv.data is an unsigned char array, so there are no alignment
rules. You either need to use memcpy, or not define it as an unsigned
char.  Tony, any suggestions?

> /data/lwork/attica2/holt/git-linus/v2.6.29/fs/lockd/mon.c:279
>     e376:       00 00 00 02 00 00                   nop.m 0x0
>     e37c:       92 d0 e9 53                         shl r16=r9,5;;
> 
> nsm_display_address():
> /data/lwork/attica2/holt/git-linus/v2.6.29/fs/lockd/mon.c:86
> ...
>     e3d0:       0a 60 28 1c 8d 39       [MMI]       cmp4.eq p12,p13=10,r14;;
>     e3d6:       00 a8 95 30 23 00                   st8 [r37]=r53

Haven't gotten to this one yet.

Robin
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