[bpf-next,0/6] libbpf: add support for kernel module BTF CO-RE relocations

Message

Andrii Nakryiko Nov. 19, 2020, 11:22 p.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_sidecar"), that is a predictable playground for all the
BPF selftests, that rely on module BTFs.

Andrii Nakryiko (6):
  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_sidecar kernel module for testing
  selftests/bpf: add CO-RE relocs selftest relying on kernel module BTF

 kernel/trace/bpf_trace.c                      |   6 +-
 tools/lib/bpf/btf.c                           |  61 +--
 tools/lib/bpf/libbpf.c                        | 352 ++++++++++++++----
 tools/lib/bpf/libbpf_internal.h               |   1 +
 tools/testing/selftests/bpf/.gitignore        |   1 +
 tools/testing/selftests/bpf/Makefile          |  12 +-
 .../selftests/bpf/bpf_sidecar/.gitignore      |   6 +
 .../selftests/bpf/bpf_sidecar/Makefile        |  20 +
 .../bpf/bpf_sidecar/bpf_sidecar-events.h      |  36 ++
 .../selftests/bpf/bpf_sidecar/bpf_sidecar.c   |  51 +++
 .../selftests/bpf/bpf_sidecar/bpf_sidecar.h   |  14 +
 .../selftests/bpf/prog_tests/core_reloc.c     |  72 +++-
 .../selftests/bpf/progs/core_reloc_types.h    |  17 +
 .../bpf/progs/test_core_reloc_module.c        |  66 ++++
 tools/testing/selftests/bpf/test_progs.c      |  52 +++
 15 files changed, 647 insertions(+), 120 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_sidecar/.gitignore
 create mode 100644 tools/testing/selftests/bpf/bpf_sidecar/Makefile
 create mode 100644 tools/testing/selftests/bpf/bpf_sidecar/bpf_sidecar-events.h
 create mode 100644 tools/testing/selftests/bpf/bpf_sidecar/bpf_sidecar.c
 create mode 100644 tools/testing/selftests/bpf/bpf_sidecar/bpf_sidecar.h
 create mode 100644 tools/testing/selftests/bpf/progs/test_core_reloc_module.c