netdev - Re: [PATCH bpf-next] tools/resolve_btfids: Warn when having multiple IDs for single type

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Message-ID: <CAADnVQJSry=o-GOPT0XL0=qGrikz=TuP=Wx7fHyiQVjLqMcOxA@mail.gmail.com>
Date:   Tue, 5 Jan 2021 11:37:09 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Qais Yousef <qais.yousef@....com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH bpf-next] tools/resolve_btfids: Warn when having multiple
 IDs for single type

On Tue, Jan 5, 2021 at 7:39 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> The kernel image can contain multiple types (structs/unions)
> with the same name. This causes distinct type hierarchies in
> BTF data and makes resolve_btfids fail with error like:
>
>   BTFIDS  vmlinux
> FAILED unresolved symbol udp6_sock
>
> as reported by Qais Yousef [1].
>
> This change adds warning when multiple types of the same name
> are detected:
>
>   BTFIDS  vmlinux
> WARN: multiple IDs found for 'file' (526, 113351)
> WARN: multiple IDs found for 'sk_buff' (2744, 113958)
>
> We keep the lower ID for the given type instance and let the
> build continue.

I think it would make sense to mention this decision in the warning.
'WARN: multiple IDs' is ambiguous and confusing when action is not specified.