This series introduces four new kfuncs -- bpf_in_nmi(), bpf_in_hardirq(), bpf_in_serving_softirq(), and bpf_in_task() -- to allow BPF programs to query the current execution context.
While BPF programs can often infer their context from attachment points, subsystems like sched_ext may call the same BPF logic from multiple contexts (e.g., task-to-task wake-ups vs. interrupt-to-task wake-ups). These kfuncs provide a reliable way to branch logic based on the current CPU execution state. The series includes a new selftest suite, ctx_kfunc, which uses bpf_testmod to verify context detection across Task, HardIRQ, and SoftIRQ boundaries via irq_work and tasklets. NMI context testing is omitted from the suite as NMIs cannot be triggered deterministically within the software-only environments typically used for BPF CI. Changwoo Min (2): bpf: Introduce execution context detection kfuncs selftests/bpf: Add tests for execution context kfuncs kernel/bpf/helpers.c | 44 ++++++++++++++ .../selftests/bpf/prog_tests/ctx_kfunc.c | 59 +++++++++++++++++++ tools/testing/selftests/bpf/progs/test_ctx.c | 51 ++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 32 ++++++++++ .../bpf/test_kmods/bpf_testmod_kfunc.h | 4 ++ 5 files changed, 190 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/ctx_kfunc.c create mode 100644 tools/testing/selftests/bpf/progs/test_ctx.c -- 2.52.0
