hi,
adding helpers for trampolines and 2 other fixes to have kernel
support for loading trampoline programs in bcc/bpftrace.

Original rfc post [1].

Speedup output of perf bench while running klockstat.py
on kprobes vs trampolines:

    Without:
            $ perf bench sched messaging -l 50000
            ...
                 Total time: 18.571 [sec]

    With current kprobe tracing:
            $ perf bench sched messaging -l 50000
            ...
                 Total time: 183.395 [sec]

    With kfunc tracing:
            $ perf bench sched messaging -l 50000
            ...
                 Total time: 39.773 [sec]

v3 changes:
  - added ack from John Fastabend for patch 1
  - move out is_bpf_image_address from is_bpf_text_address call [David]

v2 changes:
  - make the unwind work for dispatcher as well
  - added test for allowed trampolines count
  - used raw tp pt_regs nest-arrays for trampoline helpers

thanks,
jirka


[1] https://lore.kernel.org/netdev/20191229143740.29143-1-jolsa@kernel.org/ (local)
---
Jiri Olsa (6):
      bpf: Allow ctx access for pointers to scalar
      bpf: Add bpf_perf_event_output_kfunc
      bpf: Add bpf_get_stackid_kfunc
      bpf: Add bpf_get_stack_kfunc
      bpf: Allow to resolve bpf trampoline and dispatcher in unwind
      selftest/bpf: Add test for allowed trampolines count

 include/linux/bpf.h                                       |  12 +++++++++++-
 kernel/bpf/btf.c                                          |  13 ++++++++++++-
 kernel/bpf/dispatcher.c                                   |   4 ++--
 kernel/bpf/trampoline.c                                   |  82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 kernel/extable.c                                          |   7 +++++--
 kernel/trace/bpf_trace.c                                  |  96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/prog_tests/trampoline_count.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_trampoline_count.c |  21 +++++++++++++++++++++
 8 files changed, 334 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/trampoline_count.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_trampoline_count.c