[PATCH bpf-next 0/3] Add new-style bpf_object__open APIs

[Andrii Nakryiko <andriin@fb.com>]

Add bpf_object__open_file() and bpf_object__open_mem() APIs that use a new
approach to providing future-proof non-ABI-breaking API changes. It relies on
APIs accepting optional self-describing "opts" struct, containing its own
size, filled out and provided by potentially outdated (as well as
newer-than-libbpf) user application. A set of internal helper macros
(OPTS_VALID, OPTS_HAS, and OPTS_GET) streamline and simplify a graceful
handling forward and backward compatibility for user applications dynamically
linked against different versions of libbpf shared library.

Users of libbpf are provided with convenience macro LIBBPF_OPTS that takes
care of populating correct structure size and zero-initializes options struct,
which helps avoid obscure issues of unitialized padding. Uninitialized padding
in a struct might turn into garbage-populated new fields understood by future
versions of libbpf.

Patch #3 switches two of test_progs' tests to use new APIs as a validation
that they work as expected.

v1->v2:
- use better approach for tracking last field in opts struct;
- convert few tests to new APIs for validation;
- fix bug with using offsetof(last_field) instead of offsetofend(last_field).

Andrii Nakryiko (3):
  libbpf: stop enforcing kern_version, populate it for users
  libbpf: add bpf_object__open_{file,mem} w/ extensible opts
  selftests/bpf: switch tests to new bpf_object__open_{file,mem}() APIs

 tools/lib/bpf/libbpf.c                        | 128 +++++++++---------
 tools/lib/bpf/libbpf.h                        |  38 +++++-
 tools/lib/bpf/libbpf.map                      |   3 +
 tools/lib/bpf/libbpf_internal.h               |  32 +++++
 tools/testing/selftests/bpf/Makefile          |   2 +-
 .../selftests/bpf/prog_tests/attach_probe.c   |  42 +++++-
 .../bpf/prog_tests/reference_tracking.c       |   7 +-
 .../selftests/bpf/progs/test_attach_probe.c   |   1 -
 .../bpf/progs/test_get_stack_rawtp.c          |   1 -
 .../selftests/bpf/progs/test_perf_buffer.c    |   1 -
 .../selftests/bpf/progs/test_stacktrace_map.c |   1 -
 11 files changed, 176 insertions(+), 80 deletions(-)

-- 
2.17.1