[bpf-next,v4,00/10] bpf: add bpf_get_stack helper

Currently, stackmap and bpf_get_stackid helper are provided
for bpf program to get the stack trace. This approach has
a limitation though. If two stack traces have the same hash,
only one will get stored in the stackmap table regardless of
whether BPF_F_REUSE_STACKID is specified or not,
so some stack traces may be missing from user perspective.

This patch implements a new helper, bpf_get_stack, will
send stack traces directly to bpf program. The bpf program
is able to see all stack traces, and then can do in-kernel
processing or send stack traces to user space through
shared map or bpf_perf_event_output.

Patches #1 and #2 implemented the core kernel support.
Patch #3 removes two never-hit branches in verifier.
Patches #4 and #5 are two verifier improves to make
bpf programming easier. Patch #6 synced the new helper
to tools headers. Patch #7 moved perf_event polling code
and ksym lookup code from samples/bpf to
tools/testing/selftests/bpf. Patch #8 added a verifier
test in tools/bpf for new verifier change.
Patches #9 and #10 added tests for raw tracepoint prog
and tracepoint prog respectively.

Changelogs:
  v3 -> v4:
    . fixed a bug when meta ptr is set to NULL in check_func_arg.
    . introduced tnum_arshift and added detailed comments for
      the underlying implementation
    . avoided using VLA in tools/bpf test_progs.
  v2 -> v3:
    . used meta to track helper memory size argument
    . implemented range checking for ARSH in verifier
    . moved perf event polling and ksym related functions
      from samples/bpf to tools/bpf
    . added test to compare build id's between bpf_get_stackid
      and bpf_get_stack
  v1 -> v2:
    . fixed compilation error when CONFIG_PERF_EVENTS is not enabled

Yonghong Song (10):
  bpf: change prototype for stack_map_get_build_id_offset
  bpf: add bpf_get_stack helper
  bpf/verifier: refine retval R0 state for bpf_get_stack helper
  bpf: remove never-hit branches in verifier adjust_scalar_min_max_vals
  bpf/verifier: improve register value range tracking with ARSH
  tools/bpf: add bpf_get_stack helper to tools headers
  samples/bpf: move common-purpose trace functions to selftests
  tools/bpf: add a verifier test case for bpf_get_stack helper and ARSH
  tools/bpf: add a test for bpf_get_stack with raw tracepoint prog
  tools/bpf: add a test for bpf_get_stack with tracepoint prog

 include/linux/bpf.h                                |   1 +
 include/linux/filter.h                             |   3 +-
 include/linux/tnum.h                               |   4 +-
 include/uapi/linux/bpf.h                           |  19 ++-
 kernel/bpf/core.c                                  |   5 +
 kernel/bpf/stackmap.c                              |  80 ++++++++-
 kernel/bpf/syscall.c                               |  10 ++
 kernel/bpf/tnum.c                                  |  10 ++
 kernel/bpf/verifier.c                              |  75 ++++++++-
 kernel/trace/bpf_trace.c                           |  50 +++++-
 samples/bpf/Makefile                               |  11 +-
 samples/bpf/bpf_load.c                             |  63 -------
 samples/bpf/bpf_load.h                             |   7 -
 samples/bpf/offwaketime_user.c                     |   1 +
 samples/bpf/sampleip_user.c                        |   1 +
 samples/bpf/spintest_user.c                        |   1 +
 samples/bpf/trace_event_user.c                     |   1 +
 samples/bpf/trace_output_user.c                    | 125 ++------------
 tools/include/uapi/linux/bpf.h                     |  19 ++-
 tools/testing/selftests/bpf/Makefile               |   3 +-
 tools/testing/selftests/bpf/bpf_helpers.h          |   3 +-
 tools/testing/selftests/bpf/test_get_stack_rawtp.c | 102 +++++++++++
 tools/testing/selftests/bpf/test_progs.c           | 185 +++++++++++++++++++-
 .../selftests/bpf/test_stacktrace_build_id.c       |  20 ++-
 tools/testing/selftests/bpf/test_stacktrace_map.c  |  20 ++-
 tools/testing/selftests/bpf/test_verifier.c        |  45 +++++
 tools/testing/selftests/bpf/trace_helpers.c        | 186 +++++++++++++++++++++
 tools/testing/selftests/bpf/trace_helpers.h        |  24 +++
 28 files changed, 856 insertions(+), 218 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/test_get_stack_rawtp.c
 create mode 100644 tools/testing/selftests/bpf/trace_helpers.c
 create mode 100644 tools/testing/selftests/bpf/trace_helpers.h