From: "John W. Linville" <linville@xxxxxxxxxxxxx>
Date: Fri, 5 Jun 2009 08:25:03 -0400
> On Thu, Jun 04, 2009 at 11:18:33PM +0200, Michael Buesch wrote:
>> From: Matthieu CASTET <castet.matthieu@xxxxxxx>
>>
>> Fix possible unaligned u32 access in b43_generate_plcp_hdr().
>> Unaligned data is read/write with a u32 pointer instead of using the
>> packed structure. Some versions of gcc ignore the "packed" attribute, if the
>> structure element is accessed through a local pointer.
>>
>> Signed-off-by: Matthieu CASTET <castet.matthieu@xxxxxxx>
>> Signed-off-by: Michael Buesch <mb@xxxxxxxxx>
>
> That seems pretty brain-dead...can you cite a source for this
> information? The patch seems like a no-op...
The "packed" attribute simply doesn't propagate. It isn't
a GCC bug. Look at this:
struct foo {
u32 x;
} attribute((packed));
u32 bar(struct foo *p)
{
u32 *p = &p->x;
return *p;
}
That will (correctly) do a 32-bit aligned load, only doing
the "return p->x;" will proply respect the packed attribute.
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