This set allows a BPF program to make a call to a static subprog within a bpf_spin_lock critical section. This problem has been hit in sched-ext and ghOSt [0] as well, and is mostly an annoyance which is worked around by inling the static subprog into the critical section. In case of sched-ext, there are a lot of other helper/kfunc calls that need to be allow listed for the support to be complete, but a separate follow up will deal with that. Unlike static subprogs, global subprogs cannot be allowed yet as the verifier will not explore their body when encountering a call instruction for them. Therefore, we would need an alternative approach (some sort of function summarization to ensure a lock is never taken from a global subprog and all its callees). [0]: https://lore.kernel.org/bpf/bd173bf2-dea6-3e0e-4176-4a9256a9a056@xxxxxxxxxx Changelog: ---------- v1 -> v2 v1: https://lore.kernel.org/bpf/20240204120206.796412-1-memxor@xxxxxxxxx * Indicate global function call in verifier error string (Yonghong, David) * Add Acks from Yonghong, David Kumar Kartikeya Dwivedi (2): bpf: Allow calling static subprogs while holding a bpf_spin_lock selftests/bpf: Add test for static subprog call in lock cs kernel/bpf/verifier.c | 11 +++- .../selftests/bpf/prog_tests/spin_lock.c | 2 + .../selftests/bpf/progs/test_spin_lock.c | 65 +++++++++++++++++++ .../selftests/bpf/progs/test_spin_lock_fail.c | 44 +++++++++++++ .../selftests/bpf/progs/verifier_spin_lock.c | 2 +- 5 files changed, 120 insertions(+), 4 deletions(-) base-commit: 2a79690eae953daaac232f93e6c5ac47ac539f2d -- 2.40.1
