bpf, tracing: introduce bpf raw tracepoints

v6->v7:
- adopted Steven's bpf_raw_tp_map section approach to find tracepoint and corresponding bpf probe function instead of kallsyms approach. dropped kernel_tracepoint_find_by_name() patch

v5->v6:
- avoid changing semantics of for_each_kernel_tracepoint() function, instead introduce kernel_tracepoint_find_by_name() helper

v4->v5:
- adopted Daniel's fancy REPEAT macro in bpf_trace.c in patch 7

v3->v4:
- adopted Linus's CAST_TO_U64 macro to cast any integer, pointer, or small struct to u64. That nicely reduced the size of patch 1

v2->v3:
- with Linus's suggestion introduced generic COUNT_ARGS and CONCATENATE macros (or rather moved them from apparmor)
that cleaned up patches 6 and 7
- added patch 4 to refactor trace_iwlwifi_dev_ucode_error() from 17 args to 4 Now any tracepoint with >12 args will have build error

v1->v2:
- simplified api by combing bpf_raw_tp_open(name) + bpf_attach(prog_fd) into bpf_raw_tp_open(name, prog_fd) as suggested by Daniel.
That simplifies bpf_detach as well which is now simple close() of fd.
- fixed memory leak in error path which was spotted by Daniel.
- fixed bpf_get_stackid(), bpf_perf_event_output() called from raw tracepoints
- added more tests
- fixed allyesconfig build caught by buildbot

v1:
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.

Patches 2 and 3 are minor cleanups to address allyesconfig build

Patch 4 refactor trace_iwlwifi_dev_ucode_error from 17 to 4 args

Patch 5 introduces COUNT_ARGS macro

Patch 6 minor prep work to expose number of arguments passed into tracepoints.

Patch 7 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 // and attach bpf program to it
raw_tp_fd = bpf_raw_tracepoint_open("xdp_exception", prog_fd);

Ctrl-C of tracing daemon or cmdline tool will automatically detach bpf program, unload it and unregister tracepoint probe. More details in patch 7.

Patch 8 - trivial support in libbpf
Patches 9, 10 - user space 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 (10):
treewide: remove large struct-pass-by-value from tracepoint arguments net/mediatek: disambiguate mt76 vs mt7601u trace events net/mac802154: disambiguate mac80215 vs mac802154 trace events net/wireless/iwlwifi: fix iwlwifi_dev_ucode_error tracepoint
macro: introduce COUNT_ARGS() macro
tracepoint: compute num_args at build time
bpf: introduce BPF_RAW_TRACEPOINT
libbpf: add bpf_raw_tracepoint_open helper
samples/bpf: raw tracepoint test
selftests/bpf: test for bpf_get_stackid() from raw tracepoints

 drivers/infiniband/hw/hfi1/file_ops.c              |   2 +-
 drivers/infiniband/hw/hfi1/trace_ctxts.h           |  12 +-
 drivers/net/wireless/intel/iwlwifi/dvm/main.c      |   7 +-
 .../wireless/intel/iwlwifi/iwl-devtrace-iwlwifi.h  |  39 ++---
 drivers/net/wireless/intel/iwlwifi/iwl-devtrace.c  |   1 +
 drivers/net/wireless/intel/iwlwifi/mvm/utils.c     |   7 +-
 drivers/net/wireless/mediatek/mt7601u/trace.h      |   6 +-
 include/asm-generic/vmlinux.lds.h                  |  10 ++
 include/linux/bpf_types.h                          |   1 +
 include/linux/kernel.h                             |   7 +
 include/linux/trace_events.h                       |  42 +++++
 include/linux/tracepoint-defs.h                    |   6 +
 include/linux/tracepoint.h                         |  12 +-
 include/trace/bpf_probe.h                          |  91 ++++++++++
 include/trace/define_trace.h                       |  15 +-
 include/trace/events/f2fs.h                        |   2 +-
 include/uapi/linux/bpf.h                           |  11 ++
 kernel/bpf/syscall.c                               |  78 +++++++++
 kernel/trace/bpf_trace.c                           | 183 +++++++++++++++++++++
 net/mac802154/trace.h                              |   8 +-
 net/wireless/trace.h                               |   2 +-
 samples/bpf/Makefile                               |   1 +
 samples/bpf/bpf_load.c                             |  14 ++
 samples/bpf/test_overhead_raw_tp_kern.c            |  17 ++
 samples/bpf/test_overhead_user.c                   |  12 ++
 security/apparmor/include/path.h                   |   7 +-
 sound/firewire/amdtp-stream-trace.h                |   2 +-
 tools/include/uapi/linux/bpf.h                     |  11 ++
 tools/lib/bpf/bpf.c                                |  11 ++
 tools/lib/bpf/bpf.h                                |   1 +
 tools/testing/selftests/bpf/test_progs.c           |  91 +++++++---
 31 files changed, 619 insertions(+), 90 deletions(-)
 create mode 100644 include/trace/bpf_probe.h
 create mode 100644 samples/bpf/test_overhead_raw_tp_kern.c

2.9.5