It's useful to know [uk]probe's nmissed and nhit stats. For example with tracing tools, it's important to know when events may have been lost. debugfs currently exposes a control file to get this information, but it is not compatible with probes registered with the perf API. While bpf programs may be able to manually count nhit, there is no way to gather nmissed. In other words, it is currently not possible to retrieve information about FD-based probes. This patch adds a new ioctl that lets users query nmissed (as well as nhit for completeness). We currently only add support for [uk]probes but leave the possibility open for other probes like tracepoint. v3 -> v4: - Make kernel code set size field on ioctl arg - Update selftests to check size field - Remove unnecessary function stubs v2 -> v3: - Introduce bpf_link_type and associated getter to track underlying link types - Add back size field in perf_event_query_probe for forward/backwards compat - Remove NULL checks, fix typos v1 -> v2: - More descriptive cover letter - Make API more generic and support uprobes as well - Use casters/getters for libbpf instead of single getter - Fix typos - Remove size field from ioctl struct - Split out libbpf.h sync to tools dir to separate commit Daniel Xu (4): tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE ioctl libbpf: Add helpers to extract perf fd from bpf_link tracing/probe: Sync perf_event.h to tools tracing/probe: Add self test for PERF_EVENT_IOC_QUERY_PROBE include/linux/trace_events.h | 2 + include/uapi/linux/perf_event.h | 23 ++++ kernel/events/core.c | 20 +++ kernel/trace/trace_kprobe.c | 25 ++++ kernel/trace/trace_uprobe.c | 25 ++++ tools/include/uapi/linux/perf_event.h | 23 ++++ tools/lib/bpf/libbpf.c | 21 ++++ tools/lib/bpf/libbpf.h | 13 ++ tools/lib/bpf/libbpf.map | 3 + .../selftests/bpf/prog_tests/attach_probe.c | 115 ++++++++++++++++++ 10 files changed, 270 insertions(+) -- 2.21.0
