[PATCH v2 bpf-next 0/3] Add O_PATH-based BPF_OBJ_PIN and BPF_OBJ_GET support

[Andrii Nakryiko <andrii@kernel.org>]

Add ability to specify pinning location within BPF FS using O_PATH-based FDs,
similar to openat() family of APIs. Patch #1 adds necessary kernel-side
changes. Patch #2 exposes this through libbpf APIs. Patch #3 uses new mount
APIs (fsopen, fsconfig, fsmount) to demonstrated how now it's possible to work
with detach-mounted BPF FS using new BPF_OBJ_PIN and BPF_OBJ_GET
functionality.

This feature is inspired as a result of recent conversations during
LSF/MM/BPF 2023 conference about shortcomings of being able to perform BPF
objects pinning only using lookup-based paths.

v1->v2:
  - add BPF_F_PATH_FD flag that should go along with path FD (Christian).

Andrii Nakryiko (3):
  bpf: support O_PATH FDs in BPF_OBJ_PIN and BPF_OBJ_GET commands
  libbpf: add opts-based bpf_obj_pin() API and add support for path_fd
  selftests/bpf: add path_fd-based BPF_OBJ_PIN and BPF_OBJ_GET tests

 include/linux/bpf.h                           |   4 +-
 include/uapi/linux/bpf.h                      |  10 ++
 kernel/bpf/inode.c                            |  16 +--
 kernel/bpf/syscall.c                          |  25 +++-
 tools/include/uapi/linux/bpf.h                |  10 ++
 tools/lib/bpf/bpf.c                           |  17 ++-
 tools/lib/bpf/bpf.h                           |  18 ++-
 tools/lib/bpf/libbpf.map                      |   1 +
 .../bpf/prog_tests/bpf_obj_pinning.c          | 112 ++++++++++++++++++
 9 files changed, 193 insertions(+), 20 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c

-- 
2.34.1