From: Daniel Borkmann <daniel@iogearbox•net>
To: Johannes Berg <johannes@sipsolutions•net>,
Alexei Starovoitov <ast@kernel•org>
Cc: netdev <netdev@vger•kernel.org>
Subject: Re: __sk_buff.data_end
Date: Thu, 20 Apr 2017 02:01:49 +0200 [thread overview]
Message-ID: <58F7FA6D.5030000@iogearbox.net> (raw)
In-Reply-To: <1492640459.22185.7.camel@sipsolutions.net>
On 04/20/2017 12:20 AM, Johannes Berg wrote:
> On Wed, 2017-04-19 at 23:31 +0200, Johannes Berg wrote:
>> Hi Alexei, Daniel,
>>
>> I'm looking at adding the __wifi_sk_buff I talked about, and I notice
>> that it uses CB space to store data_end. Unfortunately, in a lot of
>> cases, we don't have any CB space to spare in wifi.
>
> I guess I can work around this, would this seem reasonable?
>
> struct bpf_skb_data_end {
> struct qdisc_skb_cb qdisc_cb;
> - void *data_end;
> + /*
> + * The alignment here is for mac80211, since that doesn't use
> + * a pointer but a u64 value and needs to save/restore that
> + * across running its BPF programs.
> + */
> + void *data_end __aligned(sizeof(u64));
> };
Yeah, should work as well for the 32 bit archs, on 64 bit we
have this effectively already:
struct bpf_skb_data_end {
struct qdisc_skb_cb qdisc_cb; /* 0 28 */
/* XXX 4 bytes hole, try to pack */
void * data_end; /* 32 8 */
/* size: 40, cachelines: 1, members: 2 */
/* sum members: 36, holes: 1, sum holes: 4 */
/* last cacheline: 40 bytes */
};
Can you elaborate on why this works for mac80211? It uses cb
only up to that point from where you invoke the prog?
next prev parent reply other threads:[~2017-04-20 0:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 21:31 __sk_buff.data_end Johannes Berg
2017-04-19 22:20 ` __sk_buff.data_end Johannes Berg
2017-04-20 0:01 ` Daniel Borkmann [this message]
2017-04-20 0:12 ` __sk_buff.data_end Alexei Starovoitov
2017-04-20 0:38 ` __sk_buff.data_end Daniel Borkmann
2017-04-20 6:07 ` __sk_buff.data_end Johannes Berg
2017-04-20 6:06 ` __sk_buff.data_end Johannes Berg
2017-04-20 6:01 ` __sk_buff.data_end Johannes Berg
2017-04-20 14:10 ` __sk_buff.data_end Daniel Borkmann
2017-04-20 14:17 ` __sk_buff.data_end Johannes Berg
2017-04-20 14:28 ` __sk_buff.data_end Daniel Borkmann
2017-04-20 14:32 ` __sk_buff.data_end Johannes Berg
2017-04-20 14:46 ` __sk_buff.data_end Daniel Borkmann
2017-04-20 14:48 ` __sk_buff.data_end Johannes Berg
2017-04-19 23:51 ` __sk_buff.data_end Daniel Borkmann
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