linux-kernel - Re: [PATCH v3 net-next 00/12] bpf: rewrite value tracking in verifier

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Message-ID: <5922c77e-0476-c4a8-3bf2-e502ee3acb8f@solarflare.com>
Date:   Thu, 6 Jul 2017 15:07:20 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Alexei Starovoitov <ast@...com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        iovisor-dev <iovisor-dev@...ts.iovisor.org>
Subject: Re: [PATCH v3 net-next 00/12] bpf: rewrite value tracking in verifier

On 04/07/17 20:22, Edward Cree wrote:
> I don't know why test_l4lb has to process _fewer_ insns with my patches;
>  if anything I'm worrying that I may be incorrectly pruning branches.
> (I've spotted a possible bug in that I'm not looking at 'id' which,
>  although it doesn't have to match, if two regs in the old state had the
>  same id as each other, then those regs in the new state have to have
>  the same id as each other too.)
I've now fixed that bug, and also changing it to not fill in 'id' on pointers
 other than PTR_TO_PACKET when doing arithmetic (because it's only used for
 'range' sharing and only PTR_TO_PACKET have that.  Of course
 PTR_TO_MAP_VALUE_OR_NULL still use id, but they don't get it from arithmetic).
Changes will be in next version of patch series, but for now:
Program         net-next  short  full   new
test_pkt_access       78     79    79    79
test_xdp             386    411   407   389
test_l4lb           6438   4154  4154  4062
test_tcp_estats      435    436   435   435
test_bpf_obj_id        8      8     8     8
test_pkt_md_access    41     42    42    42
As you can see, the #insns has gone down even further.

-Ed