[PATCH bpf-next v3 0/4] bpf: Add __bpf_kfunc tag for kfunc definitions

[David Vernet <void@manifault.com>]

This is v3 of the patchset [0]. v2 can be found at [1].

[0]: https://lore.kernel.org/bpf/Y7kCsjBZ%2FFrsWW%2Fe@maniforge.lan/T/
[1]: https://lore.kernel.org/lkml/20230123171506.71995-1-void@manifault.com/

Changelog:
----------
v2 -> v3:
- Go back to the __bpf_kfunc approach from v1. The BPF_KFUNC macro
  received pushback as it didn't match the more typical EXPORT_SYMBOL*
  APIs used elsewhere in the kernel. It's the longer term plan, but for
  now we're proposing something less controversial to fix kfuncs and BTF
  encoding.
- Add __bpf_kfunc macro to newly added cpumask kfuncs.
- Add __bpf_kfunc macro to newly added XDP metadata kfuncs, which were
  failing to be BTF encoded in the thread in [2].
- Update patch description(s) to reference the discussions in [2].
- Add a selftest that validates that a static kfunc with unused args is
  properly BTF encoded and can be invoked.

[2]: https://lore.kernel.org/all/fe5d42d1-faad-d05e-99ad-1c2c04776950@oracle.com/

v1 -> v2:
- Wrap entire function signature in BPF_KFUNC macro instead of using
  __bpf_kfunc tag (Kumar)
- Update all kfunc definitions to use this macro.
- Update kfuncs.rst documentation to describe and illustrate the macro.
- Also clean up a few small parts of kfuncs.rst, e.g. some grammar, and
  in general making it a bit tighter.

David Vernet (4):
  bpf: Add __bpf_kfunc tag for marking kernel functions as kfuncs
  bpf: Document usage of the new __bpf_kfunc macro
  bpf: Add __bpf_kfunc tag to all kfuncs
  selftests/bpf: Add testcase for static kfunc

 Documentation/bpf/kfuncs.rst                  | 20 +++++-
 Documentation/conf.py                         |  3 +
 include/linux/btf.h                           |  8 +++
 kernel/bpf/cpumask.c                          | 60 +++++++++---------
 kernel/bpf/helpers.c                          | 38 ++++++------
 kernel/cgroup/rstat.c                         |  4 +-
 kernel/kexec_core.c                           |  3 +-
 kernel/trace/bpf_trace.c                      |  8 +--
 net/bpf/test_run.c                            | 61 +++++++++++--------
 net/core/xdp.c                                |  5 +-
 net/ipv4/tcp_bbr.c                            | 16 ++---
 net/ipv4/tcp_cong.c                           | 10 +--
 net/ipv4/tcp_cubic.c                          | 12 ++--
 net/ipv4/tcp_dctcp.c                          | 12 ++--
 net/netfilter/nf_conntrack_bpf.c              | 20 +++---
 net/netfilter/nf_nat_bpf.c                    |  6 +-
 net/xfrm/xfrm_interface_bpf.c                 |  7 +--
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  2 +-
 .../selftests/bpf/prog_tests/kfunc_call.c     |  1 +
 .../selftests/bpf/progs/kfunc_call_test.c     | 11 ++++
 20 files changed, 176 insertions(+), 131 deletions(-)

-- 
2.39.0