netdev - Re: [RFC 0/3] bpf: Add d

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Message-ID: <20200407011052.khtujfdamjtwvpdp@ast-mbp.dhcp.thefacebook.com>
Date:   Mon, 6 Apr 2020 18:10:52 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Wenbo Zhang <ethercflow@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Andrii Nakryiko <andriin@...com>, bgregg@...flix.com
Subject: Re: [RFC 0/3] bpf: Add d_path helper

On Mon, Apr 06, 2020 at 11:09:18AM +0200, Jiri Olsa wrote:
> 
> is there any way we could have d_path functionality (even
> reduced and not working for all cases) that could be used
> or called like that?

I agree with Al. This helper cannot be enabled for all of bpf tracing.
We have to white list its usage for specific callsites only.
May be all of lsm hooks are safe. I don't know yet. This has to be
analyzed carefully. Every hook. One by one.
in_task() isn't really a solution.

At the same time I agree that such helper is badly needed.
Folks have been requesting it for long time.