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Date: Tue, 6 Oct 2015 10:50:36 -0700 From: Alexei Starovoitov <ast@...mgrid.com> To: Daniel Borkmann <daniel@...earbox.net>, Ingo Molnar <mingo@...nel.org> Cc: "David S. Miller" <davem@...emloft.net>, Andy Lutomirski <luto@...capital.net>, Hannes Frederic Sowa <hannes@...essinduktion.org>, Eric Dumazet <edumazet@...gle.com>, Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net-next 1/2] bpf: enable non-root eBPF programs On 10/6/15 1:39 AM, Daniel Borkmann wrote: >>> [...] Also classic BPF would then need to test for it, since a socket >>> filter >>> doesn't really know whether native eBPF is loaded there or a >>> classic-to-eBPF >>> transformed one, and classic never makes use of this. Anyway, it >>> could be done >>> by adding a bit flag cb_access:1 to the bpf_prog, set it during eBPF >>> verification phase, and test it inside sk_filter() if I see it >>> correctly. >> >> That could also be done in an unlikely() branch, to keep the cost to >> the non-eBPF >> case near zero. > > Yes, agreed. For the time being, the majority of users are coming from the > classic BPF side anyway and the unlikely() could still be changed later on > if it should not be the case anymore. The flag and bpf_func would share the > same cacheline as well. was also thinking that we can do it only in paths that actually have multiple protocol layers, since today bpf is mainly used with tcpdump(raw_socket) and new af_packet fanout both have cb cleared on RX, because it just came out of alloc_skb and no layers were called, and on TX we can clear 20 bytes in dev_queue_xmit_nit(). af_unix/netlink also have clean skb. Need to analyze tun and sctp... but it feels overly fragile to save a branch in sk_filter, so planning to go with if(unlikely(prog->cb_access)) memset in sk_filter(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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