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[v4,bpf-next,0/4] bpf: fix stackmap on perf_events with PEBS

Message ID 20200722184210.4078256-1-songliubraving@fb.com
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Series bpf: fix stackmap on perf_events with PEBS | expand

Message

Song Liu July 22, 2020, 6:42 p.m. UTC 
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 v3 => v4:
1. Fix error check logic in bpf_get_stackid_pe and bpf_get_stack_pe.
   (Alexei)
2. Do not allow attaching BPF programs with bpf_get_stack|stackid to
   perf_event with precise_ip > 0, but not proper callchain. (Alexei)
3. Add selftest get_stackid_cannot_attach.

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 (4):
  bpf: separate bpf_get_[stack|stackid] for perf events BPF
  bpf: fail PERF_EVENT_IOC_SET_BPF when bpf_get_[stack|stackid] cannot
    work
  selftests/bpf: add callchain_stackid
  selftests/bpf: add get_stackid_cannot_attach

 include/linux/bpf.h                           |   2 +
 include/linux/filter.h                        |   3 +-
 kernel/bpf/stackmap.c                         | 184 ++++++++++++++++--
 kernel/bpf/verifier.c                         |   3 +
 kernel/events/core.c                          |  18 ++
 kernel/trace/bpf_trace.c                      |   4 +-
 .../prog_tests/get_stackid_cannot_attach.c    |  91 +++++++++
 .../bpf/prog_tests/perf_event_stackmap.c      | 116 +++++++++++
 .../selftests/bpf/progs/perf_event_stackmap.c |  59 ++++++
 9 files changed, 459 insertions(+), 21 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c
 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