[bpf-next,0/5] Add fd_array_cnt attribute for BPF_PROG_LOAD

Message

Anton Protopopov Nov. 15, 2024, 12:46 a.m. UTC

Add a new attribute to the bpf(BPF_PROG_LOAD) system call. If this
new attribute is non-zero, then the fd_array is considered to be a
continuous array of the fd_array_cnt length and to contain only
proper map file descriptors, or btf file descriptors, or zeroes.

This change allows maps, which aren't referenced directly by a BPF
program, to be bound to the program _and_ also to be present during
the program verification (so BPF_PROG_BIND_MAP is not enough for this
use case).

The primary reason for this change is that it is a prerequisite for
adding "instruction set" maps, which are both non-referenced by the
program and must be present during the program verification.

The first three commits add the new functionality, the fourth adds
corresponding self-tests, and the last one is a small additional fix.

Anton Protopopov (5):
  bpf: add a __btf_get_by_fd helper
  bpf: move map/prog compatibility checks
  bpf: add fd_array_cnt attribute for prog_load
  selftests/bpf: Add tests for fd_array_cnt
  bpf: fix potential error return

 include/linux/btf.h                           |  13 +
 include/uapi/linux/bpf.h                      |  10 +
 kernel/bpf/btf.c                              |  13 +-
 kernel/bpf/core.c                             |   9 +-
 kernel/bpf/syscall.c                          |   2 +-
 kernel/bpf/verifier.c                         | 204 ++++++----
 tools/include/uapi/linux/bpf.h                |  10 +
 .../selftests/bpf/prog_tests/fd_array.c       | 374 ++++++++++++++++++
 8 files changed, 557 insertions(+), 78 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/fd_array.c