[bpf-next,RFC,v1,0/8] Support kernel module function calls from eBPF

Message

Kumar Kartikeya Dwivedi Aug. 30, 2021, 5:34 p.m. UTC

This set enables kernel module function calls, and also modifies verifier logic
to permit invalid kernel function calls as long as they are pruned as part of
dead code elimination. This is done to provide better runtime portability for
BPF objects, which can conditionally disable parts of code that are pruned later
by the verifier (e.g. const volatile vars, kconfig options). libbpf
modifications are made along with kernel changes to support module function
calls.

It also converts TCP congestion control objects to use the module kfunc support
instead of relying on IS_BUILTIN ifdef.

Kumar Kartikeya Dwivedi (8):
  bpf: Introduce BPF support for kernel module function calls
  bpf: Be conservative during verification for invalid kfunc calls
  libbpf: Support kernel module function calls
  libbpf: Resolve invalid kfunc calls with imm = 0, off = 0
  tools: Allow specifying base BTF file in resolve_btfids
  bpf: btf: Introduce helpers for dynamic BTF set registration
  bpf: enable TCP congestion control kfunc from modules
  bpf, selftests: Add basic test for module kfunc call

 include/linux/bpf.h                           |   1 +
 include/linux/bpfptr.h                        |   1 +
 include/linux/btf.h                           |  18 +++
 include/linux/filter.h                        |   9 ++
 include/uapi/linux/bpf.h                      |   3 +-
 kernel/bpf/btf.c                              |  37 +++++++
 kernel/bpf/core.c                             |  14 +++
 kernel/bpf/syscall.c                          |  55 +++++++++-
 kernel/bpf/verifier.c                         | 103 ++++++++++++++----
 kernel/trace/bpf_trace.c                      |   1 +
 net/ipv4/bpf_tcp_ca.c                         |  34 +-----
 net/ipv4/tcp_bbr.c                            |  28 ++++-
 net/ipv4/tcp_cubic.c                          |  26 ++++-
 net/ipv4/tcp_dctcp.c                          |  26 ++++-
 scripts/Makefile.modfinal                     |   1 +
 tools/bpf/resolve_btfids/main.c               |  19 +++-
 tools/include/uapi/linux/bpf.h                |   3 +-
 tools/lib/bpf/bpf.c                           |   3 +
 tools/lib/bpf/libbpf.c                        |  91 ++++++++++++++--
 tools/lib/bpf/libbpf_internal.h               |   2 +
 tools/testing/selftests/bpf/Makefile          |   3 +-
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  23 +++-
 .../selftests/bpf/prog_tests/ksyms_module.c   |  10 +-
 .../selftests/bpf/progs/test_ksyms_module.c   |   9 ++
 24 files changed, 446 insertions(+), 74 deletions(-)