linux-kernel - Re: [RFC PATCH bpf-next 0/4] bpf

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Date:   Mon, 11 Jul 2022 12:51:22 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Artem Savkov <asavkov@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>, dvacek@...hat.com
Subject: Re: [RFC PATCH bpf-next 0/4] bpf_panic() helper

On Mon, Jul 11, 2022 at 10:32:16AM +0200, Artem Savkov wrote:
> eBPF is often used for kernel debugging, and one of the widely used and
> powerful debugging techniques is post-mortem debugging with a full memory dump.
> Triggering a panic at exactly the right moment allows the user to get such a
> dump and thus a better view at the system's state. This patchset adds
> bpf_panic() helper to do exactly that.

FWIW I was asked for such helper some time ago from Daniel Vacek, cc-ed

jirka

> 
> I realize that even though there are multiple guards present, a helper like
> this is contrary to BPF being "safe", so this is sent as RFC to have a
> discussion on whether adding destructive capabilities is deemed acceptable.
> 
> Artem Savkov (4):
>   bpf: add a sysctl to enable destructive bpf helpers
>   bpf: add BPF_F_DESTRUCTIVE flag for BPF_PROG_LOAD
>   bpf: add bpf_panic() helper
>   selftests/bpf: bpf_panic selftest
> 
>  include/linux/bpf.h                           |   8 +
>  include/uapi/linux/bpf.h                      |  13 ++
>  kernel/bpf/core.c                             |   1 +
>  kernel/bpf/helpers.c                          |  13 ++
>  kernel/bpf/syscall.c                          |  33 +++-
>  kernel/bpf/verifier.c                         |   7 +
>  kernel/trace/bpf_trace.c                      |   2 +
>  tools/include/uapi/linux/bpf.h                |  13 ++
>  .../selftests/bpf/prog_tests/bpf_panic.c      | 144 ++++++++++++++++++
>  9 files changed, 233 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_panic.c
> 
> -- 
> 2.35.3
>