linux-kernel - Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs

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Message-ID: <CACYkzJ6BT8F+75GW=7hLwjMwFccYBqPb3FXV5dVk0SkeNFpurg@mail.gmail.com>
Date:   Mon, 11 Jan 2021 11:14:42 +0100
From:   KP Singh <kpsingh@...nel.org>
To:     Song Liu <songliubraving@...com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, mingo@...hat.com,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Kernel Team <kernel-team@...com>, Hao Luo <haoluo@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs

On Sat, Jan 9, 2021 at 12:35 AM Song Liu <songliubraving@...com> wrote:
>
> To access per-task data, BPF program typically creates a hash table with
> pid as the key. This is not ideal because:
>  1. The use need to estimate requires size of the hash table, with may be
>     inaccurate;
>  2. Big hash tables are slow;
>  3. To clean up the data properly during task terminations, the user need
>     to write code.
>
> Task local storage overcomes these issues and becomes a better option for
> these per-task data. Task local storage is only available to BPF_LSM. Now
> enable it for tracing programs.

Also mention here that you change the pointer from being a security blob to a
dedicated member in the task struct. I assume this is because you want to
use it without CONFIG_BPF_LSM?

>

Can you also mention the reasons for changing the
raw_spin_lock_bh to raw_spin_lock_irqsave in the commit log?


> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Song Liu <songliubraving@...com>
> ---
>  include/linux/bpf.h            |  7 +++++++
>  include/linux/bpf_lsm.h        | 22 ----------------------
>  include/linux/bpf_types.h      |  2 +-
>  include/linux/sched.h          |  5 +++++
>  kernel/bpf/Makefile            |  3 +--
>  kernel/bpf/bpf_local_storage.c | 28 +++++++++++++++++-----------
>  kernel/bpf/bpf_lsm.c           |  4 ----
>  kernel/bpf/bpf_task_storage.c  | 26 ++++++--------------------
>  kernel/fork.c                  |  5 +++++
>  kernel/trace/bpf_trace.c       |  4 ++++
>  10 files changed, 46 insertions(+), 60 deletions(-)
>

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