netdev - Re: [PATCH v13 bpf-next 00/10] Add skb + xdp dynptrs

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Message-ID: <20230308001621.432d9a1a@kernel.org>
Date:   Wed, 8 Mar 2023 00:16:21 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Joanne Koong <joannelkoong@...il.com>
Cc:     bpf@...r.kernel.org, martin.lau@...nel.org, andrii@...nel.org,
        ast@...nel.org, memxor@...il.com, daniel@...earbox.net,
        netdev@...r.kernel.org, toke@...nel.org
Subject: Re: [PATCH v13 bpf-next 00/10] Add skb + xdp dynptrs

On Wed,  1 Mar 2023 07:49:43 -0800 Joanne Koong wrote:
> This patchset is the 2nd in the dynptr series. The 1st can be found here [0].
> 
> This patchset adds skb and xdp type dynptrs, which have two main benefits for
> packet parsing:
>     * allowing operations on sizes that are not statically known at
>       compile-time (eg variable-sized accesses).
>     * more ergonomic and less brittle iteration through data (eg does not need
>       manual if checking for being within bounds of data_end)
> 
> When comparing the differences in runtime for packet parsing without dynptrs
> vs. with dynptrs, there is no noticeable difference. Patch 9 contains more
> details as well as examples of how to use skb and xdp dynptrs.

Oddly I see an error trying to build net-next with clang 15.0.7,
but I'm 90% sure that it built yesterday, has anyone seen:

../kernel/bpf/verifier.c:10298:24: error: array index 16 is past the end of the array (which contains 16 elements) [-Werror,-Warray-bounds]
                                   meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
                                                   ^                  ~~~~~~~~~~~~~~~~~~~~~~~~
../kernel/bpf/verifier.c:9150:1: note: array 'special_kfunc_list' declared here
BTF_ID_LIST(special_kfunc_list)
^
../include/linux/btf_ids.h:207:27: note: expanded from macro 'BTF_ID_LIST'
#define BTF_ID_LIST(name) static u32 __maybe_unused name[16];
                          ^
1 error generated.