Sorry for the delay on this.  Discussed in [1].  It's a helper for
proving to the verifier that your access in the array is valid.  Happy
to change names or whatever.  =)

Also added a libbpf helper function for mmapping an mmappable map.

We've been using both in our ghost-BPF schedulers[2].

[1] https://lore.kernel.org/bpf/b4cb3423-b18d-8fad-7355-d8aa66ccfe4c@google.com/T/
[2] https://github.com/google/ghost-userspace/blob/main/third_party/bpf/common.bpf.h#L218

v1: https://lore.kernel.org/bpf/20240103153307.553838-1-brho@google.com/
- use libbpf's internal bpf_map_mmap_sz()
- remove debugging cruft

Barret Rhoden (2):
  libbpf: add helpers for mmapping maps
  selftests/bpf: add inline assembly helpers to access array elements

 tools/bpf/bpftool/gen.c                       |  16 +-
 tools/lib/bpf/libbpf.c                        |  18 ++
 tools/lib/bpf/libbpf.h                        |   6 +
 tools/lib/bpf/libbpf.map                      |   4 +
 .../bpf/prog_tests/test_array_elem.c          | 112 ++++++++++
 .../selftests/bpf/progs/array_elem_test.c     | 195 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/bpf_misc.h  |  43 ++++
 7 files changed, 381 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_array_elem.c
 create mode 100644 tools/testing/selftests/bpf/progs/array_elem_test.c

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2.43.0.472.g3155946c3a-goog