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* [PATCHv2 bpf-next 00/15] Improve BPF syscall command documentation
@ 2021-03-02 17:19 Joe Stringer
  2021-03-02 17:19 ` [PATCHv2 bpf-next 01/15] bpf: Import syscall arg documentation Joe Stringer
                   ` (16 more replies)
  0 siblings, 17 replies; 33+ messages in thread
From: Joe Stringer @ 2021-03-02 17:19 UTC (permalink / raw)
  To: bpf
  Cc: linux-man, linux-doc, mtk.manpages, ast, brianvv, daniel, daniel,
	john.fastabend, ppenkov, quentin, sean, yhs

The state of bpf(2) manual pages today is not exactly ideal. For the
most part, it was written several years ago and has not kept up with the
pace of development in the kernel tree. For instance, out of a total of
~35 commands to the BPF syscall available today, when I pull the
kernel-man-pages tree today I find just 6 documented commands: The very
basics of map interaction and program load.

In contrast, looking at bpf-helpers(7), I am able today to run one
command[0] to fetch API documentation of the very latest eBPF helpers
that have been added to the kernel. This documentation is up to date
because kernel maintainers enforce documenting the APIs as part of
the feature submission process. As far as I can tell, we rely on manual
synchronization from the kernel tree to the kernel-man-pages tree to
distribute these more widely, so all locations may not be completely up
to date. That said, the documentation does in fact exist in the first
place which is a major initial hurdle to overcome.

Given the relative success of the process around bpf-helpers(7) to
encourage developers to document their user-facing changes, in this
patch series I explore applying this technique to bpf(2) as well.
Unfortunately, even with bpf(2) being so out-of-date, there is still a
lot of content to convert over. In particular, the following aspects of
the bpf syscall could also be individually be generated from separate
documentation in the header:
* BPF syscall commands
* BPF map types
* BPF program types
* BPF program subtypes (aka expected_attach_type)
* BPF attachment points

Rather than tackle everything at once, I have focused in this series on
the syscall commands, "enum bpf_cmd". This series is structured to first
import what useful descriptions there are from the kernel-man-pages
tree, then piece-by-piece document a few of the syscalls in more detail
in cases where I could find useful documentation from the git tree or
from a casual read of the code. Not all documentation is comprehensive
at this point, but a basis is provided with examples that can be further
enhanced with subsequent follow-up patches. Note, the series in its
current state only includes documentation around the syscall commands
themselves, so in the short term it doesn't allow us to automate bpf(2)
generation; Only one section of the man page could be replaced. Though
if there is appetite for this approach, this should be trivial to
improve on, even if just by importing the remaining static text from the
kernel-man-pages tree.

Following that, the series enhances the python scripting around parsing
the descriptions from the header files and generating dedicated
ReStructured Text and troff output. Finally, to expose the new text and
reduce the likelihood of having it get out of date or break the docs
parser, it is added to the selftests and exposed through the kernel
documentation web pages.

The eventual goal of this effort would be to extend the kernel UAPI
headers such that each of the categories I had listed above (commands,
maps, progs, hooks) have dedicated documentation in the kernel tree, and
that developers must update the comments in the headers to document the
APIs prior to patch acceptance, and that we could auto-generate the
latest version of the bpf(2) manual pages based on a few static
description sections combined with the dynamically-generated output from
the header.

This patch series can also be found at the following location on GitHub:
https://github.com/joestringer/linux/tree/submit/bpf-command-docs_v2

Thanks also to Quentin Monnet for initial review.

[0]: make -C tools/testing/selftests/bpf docs

---

v2:
* Remove build infrastructure in favor of kernel-doc directives
* Shift userspace-api docs under Documentation/userspace-api/ebpf
* Fix scripts/bpf_doc.py syscall --header (throw unsupported error)
* Improve .gitignore handling of newly autogenerated files

---

Joe Stringer (15):
  bpf: Import syscall arg documentation
  bpf: Add minimal bpf() command documentation
  bpf: Document BPF_F_LOCK in syscall commands
  bpf: Document BPF_PROG_PIN syscall command
  bpf: Document BPF_PROG_ATTACH syscall command
  bpf: Document BPF_PROG_TEST_RUN syscall command
  bpf: Document BPF_PROG_QUERY syscall command
  bpf: Document BPF_MAP_*_BATCH syscall commands
  scripts/bpf: Abstract eBPF API target parameter
  scripts/bpf: Add syscall commands printer
  tools/bpf: Remove bpf-helpers from bpftool docs
  selftests/bpf: Templatize man page generation
  selftests/bpf: Test syscall command parsing
  docs/bpf: Add bpf() syscall command reference
  tools: Sync uapi bpf.h header with latest changes

 Documentation/bpf/index.rst                   |   9 +-
 Documentation/userspace-api/ebpf/index.rst    |  17 +
 Documentation/userspace-api/ebpf/syscall.rst  |  24 +
 Documentation/userspace-api/index.rst         |   1 +
 MAINTAINERS                                   |   2 +
 include/uapi/linux/bpf.h                      | 714 +++++++++++++++++-
 scripts/{bpf_helpers_doc.py => bpf_doc.py}    | 191 ++++-
 tools/bpf/Makefile.helpers                    |  60 --
 tools/bpf/bpftool/.gitignore                  |   1 -
 tools/bpf/bpftool/Documentation/Makefile      |  11 +-
 tools/include/uapi/linux/bpf.h                | 714 +++++++++++++++++-
 tools/lib/bpf/Makefile                        |   2 +-
 tools/perf/MANIFEST                           |   2 +-
 tools/testing/selftests/bpf/.gitignore        |   2 +
 tools/testing/selftests/bpf/Makefile          |  20 +-
 tools/testing/selftests/bpf/Makefile.docs     |  82 ++
 .../selftests/bpf/test_bpftool_build.sh       |  21 -
 tools/testing/selftests/bpf/test_doc_build.sh |  13 +
 18 files changed, 1746 insertions(+), 140 deletions(-)
 create mode 100644 Documentation/userspace-api/ebpf/index.rst
 create mode 100644 Documentation/userspace-api/ebpf/syscall.rst
 rename scripts/{bpf_helpers_doc.py => bpf_doc.py} (82%)
 delete mode 100644 tools/bpf/Makefile.helpers
 create mode 100644 tools/testing/selftests/bpf/Makefile.docs
 create mode 100755 tools/testing/selftests/bpf/test_doc_build.sh

-- 
2.27.0


^ permalink raw reply	[flat|nested] 33+ messages in thread

end of thread, other threads:[~2021-04-10 18:12 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-03-02 17:19 [PATCHv2 bpf-next 00/15] Improve BPF syscall command documentation Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 01/15] bpf: Import syscall arg documentation Joe Stringer
2021-03-03 19:38   ` Yonghong Song
2021-03-03 20:20     ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 02/15] bpf: Add minimal bpf() command documentation Joe Stringer
2021-03-03 19:44   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 03/15] bpf: Document BPF_F_LOCK in syscall commands Joe Stringer
2021-03-03 20:16   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 04/15] bpf: Document BPF_PROG_PIN syscall command Joe Stringer
2021-03-03 20:21   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 05/15] bpf: Document BPF_PROG_ATTACH " Joe Stringer
2021-03-03 20:23   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 06/15] bpf: Document BPF_PROG_TEST_RUN " Joe Stringer
2021-03-03 20:29   ` Yonghong Song
2021-03-03 23:53     ` Joe Stringer
2021-04-10 18:12       ` Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 07/15] bpf: Document BPF_PROG_QUERY " Joe Stringer
2021-03-03 20:31   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 08/15] bpf: Document BPF_MAP_*_BATCH syscall commands Joe Stringer
2021-03-03 17:38   ` Brian Vazquez
2021-03-03 20:44   ` Yonghong Song
2021-03-02 17:19 ` [PATCHv2 bpf-next 09/15] scripts/bpf: Abstract eBPF API target parameter Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 10/15] scripts/bpf: Add syscall commands printer Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 11/15] tools/bpf: Remove bpf-helpers from bpftool docs Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 12/15] selftests/bpf: Templatize man page generation Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 13/15] selftests/bpf: Test syscall command parsing Joe Stringer
2021-03-03 22:23   ` Yonghong Song
2021-03-03 23:50     ` Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 14/15] docs/bpf: Add bpf() syscall command reference Joe Stringer
2021-03-02 17:19 ` [PATCHv2 bpf-next 15/15] tools: Sync uapi bpf.h header with latest changes Joe Stringer
2021-03-03 17:25 ` [PATCHv2 bpf-next 00/15] Improve BPF syscall command documentation Jonathan Corbet
2021-03-03 18:50   ` Joe Stringer
2021-03-05  2:51 ` Alexei Starovoitov

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