[v2,bpf-next,0/7] libbpf: add support for kernel module BTF CO-RE relocations

Message

Andrii Nakryiko Dec. 1, 2020, 12:31 a.m. UTC

Implement libbpf support for performing CO-RE relocations against types in
kernel module BTFs, in addition to existing vmlinux BTF support.

This is a first step towards fully supporting kernel module BTFs. Subsequent
patch sets will expand kernel and libbpf sides to allow using other
BTF-powered capabilities (fentry/fexit, struct_ops, ksym externs, etc). For
CO-RE relocations support, though, no extra kernel changes are necessary.

This patch set also sets up a convenient and fully-controlled custom kernel
module (called "bpf_testmod"), that is a predictable playground for all the
BPF selftests, that rely on module BTFs.

v1->v2:
  - module_put() inside preempt_disable() region (Alexei);
  - bpf_sidecar -> bpf_testmod rename (Alexei);
  - test_progs more relaxed handling of bpf_testmod;
  - test_progs marks skipped sub-tests properly as SKIP now.

Andrii Nakryiko (7):
  bpf: fix bpf_put_raw_tracepoint()'s use of __module_address()
  libbpf: add internal helper to load BTF data by FD
  libbpf: refactor CO-RE relocs to not assume a single BTF object
  libbpf: add kernel module BTF support for CO-RE relocations
  selftests/bpf: add bpf_testmod kernel module for testing
  selftests/bpf: add support for marking sub-tests as skipped
  selftests/bpf: add CO-RE relocs selftest relying on kernel module BTF

 kernel/trace/bpf_trace.c                      |   8 +-
 tools/lib/bpf/btf.c                           |  61 ++--
 tools/lib/bpf/libbpf.c                        | 345 ++++++++++++++----
 tools/lib/bpf/libbpf_internal.h               |   1 +
 tools/testing/selftests/bpf/.gitignore        |   1 +
 tools/testing/selftests/bpf/Makefile          |  12 +-
 .../selftests/bpf/bpf_testmod/.gitignore      |   6 +
 .../selftests/bpf/bpf_testmod/Makefile        |  20 +
 .../bpf/bpf_testmod/bpf_testmod-events.h      |  36 ++
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  51 +++
 .../selftests/bpf/bpf_testmod/bpf_testmod.h   |  14 +
 .../selftests/bpf/prog_tests/core_reloc.c     |  79 +++-
 .../selftests/bpf/progs/core_reloc_types.h    |  17 +
 .../bpf/progs/test_core_reloc_module.c        |  66 ++++
 tools/testing/selftests/bpf/test_progs.c      |  65 +++-
 tools/testing/selftests/bpf/test_progs.h      |   1 +
 16 files changed, 661 insertions(+), 122 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_testmod/.gitignore
 create mode 100644 tools/testing/selftests/bpf/bpf_testmod/Makefile
 create mode 100644 tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
 create mode 100644 tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
 create mode 100644 tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
 create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_module.c