From: Yonghong Song <yhs@fb.com>
To: Alan Maguire <alan.maguire@oracle.com>
Cc: David Ahern <dsahern@gmail.com>, Andrii Nakryiko <andriin@fb.com>,
<bpf@vger.kernel.org>, Martin KaFai Lau <kafai@fb.com>,
<netdev@vger.kernel.org>, Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: Re: [RFC PATCH bpf-next v2 00/17] bpf: implement bpf based dumping of kernel data structures
Date: Sat, 18 Apr 2020 22:34:36 -0700 [thread overview]
Message-ID: <ae1cc2d9-bb25-a39c-5fc4-1e1a5b612e43@fb.com> (raw)
In-Reply-To: <alpine.LRH.2.21.2004171518090.16765@localhost>
On 4/17/20 8:02 AM, Alan Maguire wrote:
> On Wed, 15 Apr 2020, Yonghong Song wrote:
>
>>
>>
>> On 4/15/20 7:23 PM, David Ahern wrote:
>>> On 4/15/20 1:27 PM, Yonghong Song wrote:
>>>>
>>>> As there are some discussions regarding to the kernel interface/steps to
>>>> create file/anonymous dumpers, I think it will be beneficial for
>>>> discussion with this work in progress.
>>>>
>>>> Motivation:
>>>> The current way to dump kernel data structures mostly:
>>>> 1. /proc system
>>>> 2. various specific tools like "ss" which requires kernel support.
>>>> 3. drgn
>>>> The dropback for the first two is that whenever you want to dump more,
>>>> you
>>>> need change the kernel. For example, Martin wants to dump socket local
>>>
>>> If kernel support is needed for bpfdump of kernel data structures, you
>>> are not really solving the kernel support problem. i.e., to dump
>>> ipv4_route's you need to modify the relevant proc show function.
>>
>> Yes, as mentioned two paragraphs below. kernel change is required.
>> The tradeoff is that this is a one-time investment. Once kernel change
>> is in place, printing new fields (in most cases except new fields
>> which need additional locks etc.) no need for kernel change any more.
>>
>
> One thing I struggled with initially when reading the cover
> letter was understanding how BPF dumper programs get run.
> Patch 7 deals with that I think and the answer seems to be to
> create additional seq file infrastructure to the exisiting
> one which executes the BPF dumper programs where appropriate.
> Have I got this right? I guess more lightweight methods
Yes. The reason is that some data structures like bpf_map, task, or
task/file do not have existing seq_ops infrastructure so I created
new ones to iterate them.
> such as instrumenting functions associated with an existing /proc
> dumper are a bit too messy?
We did use existing seq_ops from /proc/net/ipv6_route and
/proc/net/netlink as an example. In the future, we will do
/proc/net/tcp[6] and
/proc/net/udp[6] which will reuse existing seq_ops with slight
modifications.
next prev parent reply other threads:[~2020-04-19 5:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 19:27 [RFC PATCH bpf-next v2 00/17] bpf: implement bpf based dumping of kernel data structures Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 01/17] net: refactor net assignment for seq_net_private structure Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 02/17] bpf: create /sys/kernel/bpfdump mount file system Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 03/17] bpf: provide a way for targets to register themselves Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 04/17] bpf: allow loading of a dumper program Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 05/17] bpf: create file or anonymous dumpers Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 06/17] bpf: add PTR_TO_BTF_ID_OR_NULL support Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 07/17] bpf: add netlink and ipv6_route targets Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 08/17] bpf: add bpf_map target Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 09/17] bpf: add task and task/file targets Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 10/17] bpf: add bpf_seq_printf and bpf_seq_write helpers Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 11/17] bpf: support variable length array in tracing programs Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 12/17] bpf: implement query for target_proto and file dumper prog_id Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 13/17] tools/libbpf: libbpf support for bpfdump Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 14/17] tools/bpftool: add bpf dumper support Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 15/17] tools/bpf: selftests: add dumper programs for ipv6_route and netlink Yonghong Song
2020-04-15 19:27 ` [RFC PATCH bpf-next v2 16/17] tools/bpf: selftests: add dumper progs for bpf_map/task/task_file Yonghong Song
2020-04-15 19:28 ` [RFC PATCH bpf-next v2 17/17] tools/bpf: selftests: add a selftest for anonymous dumper Yonghong Song
2020-04-16 2:23 ` [RFC PATCH bpf-next v2 00/17] bpf: implement bpf based dumping of kernel data structures David Ahern
2020-04-16 6:41 ` Yonghong Song
2020-04-17 15:02 ` Alan Maguire
2020-04-19 5:34 ` Yonghong Song [this message]
2020-04-17 10:54 ` Alan Maguire
2020-04-19 5:30 ` Yonghong Song
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ae1cc2d9-bb25-a39c-5fc4-1e1a5b612e43@fb.com \
--to=yhs@fb.com \
--cc=alan.maguire@oracle.com \
--cc=andriin@fb.com \
--cc=ast@fb.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=dsahern@gmail.com \
--cc=kafai@fb.com \
--cc=kernel-team@fb.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox