This series introduces four new BPF-native inline helpers -- bpf_in_nmi(),
bpf_in_hardirq(), bpf_in_serving_softirq(), and bpf_in_task() -- to allow
BPF programs to query the current execution context.

Following the feedback on v1, these are implemented in bpf_experimental.h
as inline helpers wrapping get_preempt_count(). This approach allows the
logic to be JIT-inlined for better performance compared to a kfunc call,
while providing the granular context detection (e.g., hardirq vs. softirq)
required by subsystems like sched_ext.

The series includes a new selftest suite, exe_ctx, which uses bpf_testmod
to verify context detection across Task, HardIRQ, and SoftIRQ boundaries
via irq_work and tasklets. NMI context testing is omitted as NMIs cannot
be triggered deterministically within software-only BPF CI environments.

ChangeLog v1 -> v2:
- Dropped the core kernel kfunc implementations, and implemented context
  detection as inline BPF helpers in bpf_experimental.h.
- Renamed the selftest suite from ctx_kfunc to exe_ctx to reflect the
  change from kfuncs to helpers.
- Updated BPF programs to use the new inline helpers.
- Swapped clean-up order between tasklet and irqwork in bpf_testmod to 
  avoid re-scheduling the already-killed tasklet (reported by bot+bpf-ci).

Changwoo Min (2):
  selftests/bpf: Introduce execution context detection helpers
  selftests/bpf: Add tests for execution context helpers

 .../testing/selftests/bpf/bpf_experimental.h  | 38 ++++++++++++
 .../selftests/bpf/prog_tests/exe_ctx.c        | 59 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_ctx.c  | 48 +++++++++++++++
 .../selftests/bpf/test_kmods/bpf_testmod.c    | 32 ++++++++++
 .../bpf/test_kmods/bpf_testmod_kfunc.h        |  4 ++
 5 files changed, 181 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/exe_ctx.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_ctx.c

-- 
2.52.0