bpf, tracing: introduce bpf raw tracepoints

This patch set is a different way to address the pressing need to access
task_struct pointers in sched tracepoints from bpf programs.

The first approach simply added these pointers to sched tracepoints:
https://lkml.org/lkml/2017/12/14/753
which Peter nacked.
Few options were discussed and eventually the discussion converged on
doing bpf specific tracepoint_probe_register() probe functions.
Details here:
https://lkml.org/lkml/2017/12/20/929

Patch 1 is kernel wide cleanup of pass-struct-by-value into
pass-struct-by-reference into tracepoints.

Patch 2 minor prep work to expose number of arguments passed
into tracepoints.

Patch 3 introduces BPF_RAW_TRACEPOINT api.
the auto-cleanup and multiple concurrent users are must have
features of tracing api. For bpf raw tracepoints it looks like:
  // load bpf prog with BPF_PROG_TYPE_RAW_TRACEPOINT type
  prog_fd = bpf_prog_load(...);

  // receive anon_inode fd for given bpf_raw_tracepoint
  raw_tp_fd = bpf_raw_tracepoint_open("xdp_exception");

  // attach bpf program to given tracepoint
  bpf_prog_attach(prog_fd, raw_tp_fd, BPF_RAW_TRACEPOINT);

Ctrl-C of tracing daemon or cmdline tool will automatically
detach bpf program, unload it and unregister tracepoint probe.
More details in patch 3.

Patch 4, 5 - user space lib and tests

samples/bpf/test_overhead performance on 1 cpu:

tracepoint    base  kprobe+bpf tracepoint+bpf raw_tracepoint+bpf
task_rename   1.1M   769K        947K            1.0M
urandom_read  789K   697K        750K            755K

Alexei Starovoitov (5):
  treewide: remove struct-pass-by-value from tracepoints arguments
  tracepoint: compute num_args at build time
  bpf: introduce BPF_RAW_TRACEPOINT
  libbpf: add bpf_raw_tracepoint_open helper
  samples/bpf: raw tracepoint test

 arch/x86/xen/mmu_pv.c                    |  16 +--
 drivers/gpu/drm/i915/i915_trace.h        |  13 +-
 drivers/infiniband/hw/hfi1/file_ops.c    |   2 +-
 drivers/infiniband/hw/hfi1/trace_ctxts.h |  12 +-
 drivers/s390/cio/ioasm.c                 |  18 +--
 drivers/s390/cio/trace.h                 |  50 ++++----
 fs/dax.c                                 |   2 +-
 include/linux/bpf_types.h                |   1 +
 include/linux/trace_events.h             |  57 +++++++++
 include/linux/tracepoint-defs.h          |   1 +
 include/linux/tracepoint.h               |  32 +++--
 include/trace/bpf_probe.h                |  87 +++++++++++++
 include/trace/define_trace.h             |  15 ++-
 include/trace/events/f2fs.h              |   2 +-
 include/trace/events/fs_dax.h            |   6 +-
 include/trace/events/rcu.h               |   4 +-
 include/trace/events/xen.h               |  32 ++---
 include/uapi/linux/bpf.h                 |  11 ++
 kernel/bpf/syscall.c                     | 108 ++++++++++++++++
 kernel/rcu/tree.c                        |  10 +-
 kernel/trace/bpf_trace.c                 | 211 +++++++++++++++++++++++++++++++
 kernel/tracepoint.c                      |  27 ++--
 net/wireless/trace.h                     |   2 +-
 samples/bpf/Makefile                     |   1 +
 samples/bpf/bpf_load.c                   |  13 ++
 samples/bpf/test_overhead_raw_tp_kern.c  |  17 +++
 samples/bpf/test_overhead_user.c         |  12 ++
 sound/firewire/amdtp-stream-trace.h      |   2 +-
 tools/include/uapi/linux/bpf.h           |  11 ++
 tools/lib/bpf/bpf.c                      |  10 ++
 tools/lib/bpf/bpf.h                      |   1 +
 31 files changed, 677 insertions(+), 109 deletions(-)
 create mode 100644 include/trace/bpf_probe.h
 create mode 100644 samples/bpf/test_overhead_raw_tp_kern.c

-- 
2.9.5