netdev - Re: [PATCH v2 net-next] net: filter: export pkt_type

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Date:	Fri, 05 Sep 2014 00:45:59 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Laight <David.Laight@...lab.com>,
	Denis Kirjanov <kirjanov@...il.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Denis Kirjanov <kda@...ux-powerpc.org>, netdev@...r.kernel.org,
	Markos Chandras <markos.chandras@...tec.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH v2 net-next] net: filter: export pkt_type_offset() helper

Hi,

On Thu, Sep 4, 2014, at 22:51, Alexei Starovoitov wrote:
> On Thu, Sep 4, 2014 at 7:41 AM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
> > On Do, 2014-09-04 at 07:35 -0700, Eric Dumazet wrote:
> >> On Thu, 2014-09-04 at 16:33 +0200, Hannes Frederic Sowa wrote:
> >>
> >> > Which btw. also uses int, which might change alignment of structures.
> >>
> >> You missed the point .
> >>
> >> kmemcheck wants to make sure the whole word is set, or else you could
> >> get false positives.
> >>
> >> kmemcheck needs are quite different.
> >
> > Now that you said it, I understand. :)
> >
> > You were right with the int vs. u8 thing all along. gcc aligns the
> > datatype on the next struct field and not on the whole field, as I
> > expected. So excuse my error above.
> >
> > I think the latest proposals looks good?
> 
> to me: yes
> and I think your latest half-patch with:
> +       __u8                    __pkt_type_offset[0];
> also looks good.
> 
> Are you going to take it over from Denis here?

I don't know. Denis, do you want to incorperate my changes or should I
take over here?

> while at it would you fix sparc jit as well that has comment:
> #if 0
>                                 /* GCC won't let us take the address of
>                                  * a bit field even though we very much
>                                  * know what we are doing here.
>                                  */
>                         case BPF_ANC | SKF_AD_PKTTYPE:
>                                 __emit_skb_load8(pkt_type, r_A);
>                                 emit_alu_K(SRL, 5);
>                                 break;
> #endif
> should be able to replace 'pkt_type' above with __pkt_type_offset...

I'll have a look then but cannot test sparc easily.

Bye,
Hannes
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