netdev - Re: [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct

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Message-ID: <CAEf4Bzbk1ivXa=Q_Fvb+jjrWAJaXJccBWhFTAsH4pVsz0V-eLQ@mail.gmail.com>
Date:   Tue, 4 Aug 2020 23:18:20 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Wenbo Zhang <ethercflow@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Brendan Gregg <bgregg@...flix.com>,
        Florent Revest <revest@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct_access function

On Sat, Aug 1, 2020 at 10:04 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Adding btf_struct_walk function that walks through the
> struct type + given offset and returns following values:
>
>   enum bpf_struct_walk_result {
>        /* < 0 error */
>        WALK_SCALAR = 0,
>        WALK_PTR,
>        WALK_STRUCT,
>   };
>
> WALK_SCALAR - when SCALAR_VALUE is found
> WALK_PTR    - when pointer value is found, its ID is stored
>               in 'next_btf_id' output param
> WALK_STRUCT - when nested struct object is found, its ID is stored
>               in 'next_btf_id' output param
>
> It will be used in following patches to get all nested
> struct objects for given type and offset.
>
> The btf_struct_access now calls btf_struct_walk function,
> as long as it gets nested structs as return value.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---

This turned out to be rather much more succinct and clean than I
imagined when I was originally proposing the struct iteration idea.
Great job at abstracting this!

Acked-by: Andrii Nakryiko <andriin@...com>

>  kernel/bpf/btf.c | 75 +++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 65 insertions(+), 10 deletions(-)
>

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