On 11/22/23 10:31 PM, Andrii Nakryiko wrote:
See patch #2 for justification. In few words, current eager verification of global func prevents BPF CO-RE approaches to be applied to global functions. Patch #1 is just a nicety to emit global subprog names in verifier logs. Patch #3 adds selftests validating new lazy semantics. Andrii Nakryiko (3): bpf: emit global subprog name in verifier logs bpf: validate global subprogs lazily selftests/bpf: add lazy global subprog validation tests include/linux/bpf.h | 2 + kernel/bpf/verifier.c | 88 ++++++++++++++---- .../selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/test_global_func12.c | 4 +- .../bpf/progs/verifier_global_subprogs.c | 92 +++++++++++++++++++ .../bpf/progs/verifier_subprog_precision.c | 4 +- 6 files changed, 168 insertions(+), 24 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
Series looks good to me, ACK. It needs a rebase however after the fast forward of the bpf-next tree from today. > With BPF CO-RE approach, the natural way would be to still compile BPF > object file once and guard calls to this global subprog with some CO-RE > check or using .rodata variables. That's what people do to guard usage > of new helpers or kfuncs, and any other new BPF-side feature that might > be missing on old kernels. I was wondering for selftests, could we also add something similar to the above to guard calls via co-re? Just to have this use-case covered in CI. Also perhaps one global_bad function which is dead-code would be nice to have. Thanks, Daniel
