[PATCH v3 bpf-next 0/2] bpf: fix stackmap on perf_events with PEBS

[Song Liu <songliubraving@fb.com>]

Calling get_perf_callchain() on perf_events from PEBS entries may cause
unwinder errors. To fix this issue, perf subsystem fetches callchain early,
and marks perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
Similar issue exists when BPF program calls get_perf_callchain() via
helper functions. For more information about this issue, please refer to
discussions in [1].

This set fixes this issue with helper proto bpf_get_stackid_pe and
bpf_get_stack_pe.

[1] https://lore.kernel.org/lkml/ED7B9430-6489-4260-B3C5-9CFA2E3AA87A@fb.com/

Changes v2 => v3:
1. Fix handling of stackmap skip field. (Andrii)
2. Simplify the code in a few places. (Andrii)

Changes v1 => v2:
1. Simplify the design and avoid introducing new helper function. (Andrii)

Song Liu (2):
  bpf: separate bpf_get_[stack|stackid] for perf events BPF
  selftests/bpf: add callchain_stackid

 include/linux/bpf.h                           |   2 +
 kernel/bpf/stackmap.c                         | 202 ++++++++++++++++--
 kernel/trace/bpf_trace.c                      |   4 +-
 .../bpf/prog_tests/perf_event_stackmap.c      | 116 ++++++++++
 .../selftests/bpf/progs/perf_event_stackmap.c |  59 +++++
 5 files changed, 363 insertions(+), 20 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_event_stackmap.c
 create mode 100644 tools/testing/selftests/bpf/progs/perf_event_stackmap.c

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2.24.1