[PATCH bpf-next 00/10] BPF static linking

[Andrii Nakryiko <andrii@kernel.org>]

This patch set adds new libbpf APIs and their bpftool integration that allows
to perform static linking of BPF object files. Currently no extern resolution
across object files is performed. This is going to be the focus of the follow
up patches. But, given amount of code and logic necessary to perform just
basic functionality of linking together mostly independent BPF object files,
it was decided to land basic BPF linker code and logic first and extend it
afterwards.

The motivation for BPF static linking is to provide the functionality that is
naturally assumed for user-space development process: ability to structure
application's code without artificial restrictions of having all the code and
data (variables and maps) inside a single source code file.

This enables better engineering practices of splitting code into
well-encapsulated parts. It provides ability to hide internal state from other
parts of the code base through static variables and maps. It is also a first
steps towards having generic reusable BPF libraries.

Please see individual patches (mostly #5 and #6) for more details. Patch #9
passes all test_progs' individual BPF .o files through BPF static linker,
which is supposed to be a no-op operation, so is essentially validating that
BPF static linker doesn't produce corrupted ELF object files. Patch #10 adds
Makefile infra to be able to specify multi-file BPF object files and adds the
first multi-file test to validate correctness.

Andrii Nakryiko (10):
  libbpf: expose btf_type_by_id() internally
  libbpf: add internal helper to get raw BTF strings section
  libbpf: generalize BTF and BTF.ext type ID and strings iteration
  libbpf: add generic BTF type shallow copy API
  libbpf: add BPF static linker APIs
  libbpf: add BPF static linker BTF and BTF.ext support
  bpftool: add `gen bpfo` command to perform BPF static linking
  selftests/bpf: re-generate vmlinux.h and BPF skeletons if bpftool
    changed
  selftests/bpf: pass all BPF .o's through BPF static linker
  selftests/bpf: add multi-file statically linked BPF object file test

 tools/bpf/bpftool/gen.c                       |   46 +-
 tools/lib/bpf/Build                           |    2 +-
 tools/lib/bpf/btf.c                           |  454 ++--
 tools/lib/bpf/btf.h                           |    2 +
 tools/lib/bpf/libbpf.c                        |   11 +-
 tools/lib/bpf/libbpf.h                        |   13 +
 tools/lib/bpf/libbpf.map                      |    5 +
 tools/lib/bpf/libbpf_internal.h               |   33 +
 tools/lib/bpf/linker.c                        | 1945 +++++++++++++++++
 tools/testing/selftests/bpf/.gitignore        |    1 +
 tools/testing/selftests/bpf/Makefile          |   21 +-
 .../selftests/bpf/prog_tests/static_linked.c  |   40 +
 .../selftests/bpf/progs/test_static_linked1.c |   30 +
 .../selftests/bpf/progs/test_static_linked2.c |   31 +
 14 files changed, 2444 insertions(+), 190 deletions(-)
 create mode 100644 tools/lib/bpf/linker.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/static_linked.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_static_linked1.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_static_linked2.c

-- 
2.24.1