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Date: Wed, 23 Feb 2011 13:29:46 -0800
Message-ID: <AANLkTi=dE5_VjJ+5H6cWf9nAtdkLiqhSXo6Gvd_uGQ25@mail.gmail.com>
Subject: Re: [PATCH v2 2/5] firmware: Basic dmi-sysfs support
From: Tony Luck <tony.luck@intel.com>
To: Mike Waychison <mikew@google.com>
Cc: Greg KH <greg@kroah.com>, Olof Johansson <olofj@chromium.org>,
        Andi Kleen <andi@firstfloor.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Robert Lippert <rlippert@google.com>, Jon Mayer <jonmayer@google.com>,
        Duncan Laurie <dlaurie@google.com>, Aaron Durbin <adurbin@google.com>,
        linux-kernel@vger.kernel.org, Tim Hockin <thockin@google.com>,
        David Hendrix <dhendrix@chromium.org>, linux-api@vger.kernel.org
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On Wed, Feb 23, 2011 at 12:28 PM, Mike Waychison <mikew@google.com> wrote:
> Ya, I don't think there is anything that guarantees that dmi_header is
> aligned. ? The access is probably the struct copy I did here:
>
> ? ? ? ?/* Set the key */
> ? ? ? ?entry->dh = *dh;

Yup - looking back at the assembly I see that one of the 2-byte
accesses is offset 2
(picking up ->handle), but the second is offset 0 (picking up ->type
and ->length). The
compiler assumed the structure was 2-byte aligned because of ->handle.

> What if we changed that guy to use memcpy? ?We'd probably need to
> memcpy the dmi_system_event_log as well. ?Patch attached (applies on
> top of the entire patchset).

With the patch, all the unaligned accesses go away.

Tested-by: Tony Luck <tony.luck@intel.com>

-Tony
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