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 provides a solution for this problem.
1/5 blocks ioctl(PERF_EVENT_IOC_SET_BPF) attaching BPF program that calls
get_perf_callchain() to perf events with PEBS entries.
2/5 exposes callchain fetched by perf subsystem to BPF program.
3/5 introduces bpf_get_callchain_stackid(), which is alternative to
bpf_get_stackid() for perf_event with PEBS.
4/5 adds selftests for 1/5.
5/5 adds selftests for 2/5 and 3/5.
[1] https://lore.kernel.org/lkml/ED7B9430-6489-4260-B3C5-9CFA2E3AA87A@xxxxxx/
Song Liu (5):
bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
bpf: add callchain to bpf_perf_event_data
bpf: introduce bpf_get_callchain_stackid
selftests/bpf: add get_stackid_cannot_attach
selftests/bpf: add callchain_stackid
include/linux/bpf.h | 1 +
include/linux/filter.h | 3 +-
include/linux/perf_event.h | 5 --
include/linux/trace_events.h | 5 ++
include/uapi/linux/bpf.h | 43 +++++++++++++
include/uapi/linux/bpf_perf_event.h | 7 +++
kernel/bpf/btf.c | 5 ++
kernel/bpf/stackmap.c | 63 ++++++++++++++-----
kernel/bpf/verifier.c | 7 ++-
kernel/events/core.c | 10 +++
kernel/trace/bpf_trace.c | 29 +++++++++
scripts/bpf_helpers_doc.py | 2 +
tools/include/uapi/linux/bpf.h | 43 +++++++++++++
tools/include/uapi/linux/bpf_perf_event.h | 8 +++
.../bpf/prog_tests/callchain_stackid.c | 61 ++++++++++++++++++
.../prog_tests/get_stackid_cannot_attach.c | 57 +++++++++++++++++
.../selftests/bpf/progs/callchain_stackid.c | 37 +++++++++++
17 files changed, 364 insertions(+), 22 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/callchain_stackid.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c
create mode 100644 tools/testing/selftests/bpf/progs/callchain_stackid.c
--
2.24.1
