Re: [PATCH v3 03/33] staging: rtl8192e: Mark unaligned memcpy()

Dan Carpenter
2015-05-14T23:14:48Z

On Thu, May 14, 2015 at 10:29:39PM +0200, Mateusz Kulikowski wrote:
> On 13.05.2015 10:22, Dan Carpenter wrote:
> > On Tue, May 12, 2015 at 10:00:13PM +0200, Mateusz Kulikowski wrote:
> >> On 11.05.2015 10:26, Dan Carpenter wrote:
> (...)
> >>>
> >>> Which part isn't aligned? I think they both are.
> >>>
> >> struct rtllib_rxb *prxb = prxbIndicateArray[j];
> >>
> >> struct rtllib_rxb {
> >> u8 nr_subframes;
> >> struct sk_buff *subframes[MAX_SUBFRAME_COUNT == 64];
> >> u8 dst[ETH_ALEN]; // here
> >> u8 src[ETH_ALEN]; // here
> >> } __packed;
> >>
> >> Either I forgot alignment / packing rules or this fields are never aligned "by design".
> >
> > You must have forgotten something... Everything after the pointer is
> > going to be aligned sizeof(void *).
>
> That would be true, if structure was not __packed:
>

Oh. Duh... You are correct.

I'm not positive it's "by design" though, this is staging code so maybe
they just added __packed to every struct. In fact, I'm pretty sure
unaligned pointers don't work on some arches so the __packed is probably
a bug.

regards,
dan carpenter