linux-kernel - Re: [PATCH bpf-next 1/2] bpf: Add a bpf_kallsyms

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Message-ID: <CABRcYmKBgQYHezKVaLCVwUvksFaVuU7RHW8VVjM6auOC_GOr+w@mail.gmail.com>
Date:   Tue, 22 Dec 2020 21:17:41 +0100
From:   Florent Revest <revest@...omium.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Yonghong Song <yhs@...com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        KP Singh <kpsingh@...omium.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Florent Revest <revest@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/2] bpf: Add a bpf_kallsyms_lookup helper

On Tue, Dec 22, 2020 at 3:18 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> FYI, there is a reason why kallsyms_lookup is not exported any more.
> I don't think adding that back through a backdoor is a good idea.

Did you maybe mean kallsyms_lookup_name (the one that looks an address
up based on a symbol name) ? It used to be exported but isn't anymore
indeed.
However, this is not what we're trying to do. As far as I can tell,
kallsyms_lookup (the one that looks a symbol name up based on an
address) has never been exported but its close cousins sprint_symbol
and sprint_symbol_no_offset (which only call kallsyms_lookup and
pretty print the result) are still exported, they are also used by
vsprintf. Is this an issue ?