From 3980ee9ad8575915cda3790447af700bb865b493 Mon Sep 17 00:00:00 2001 From: Athira Rajeev Date: Tue, 31 Jan 2023 19:17:48 +0530 Subject: perf probe: Fix usage when libtraceevent is missing While parsing the tracepoint events in parse_events_add_tracepoint() function, code checks for HAVE_LIBTRACEEVENT support. This is needed since libtraceevent is necessary for tracepoint. But while adding probe points, check for LIBTRACEEVENT is not done in case of perf probe. Hence, in environment with missing libtraceevent-devel, it is observed that adding a probe point shows below message though it can't be used via perf record. Example: Adding probe point: ./perf probe 'vfs_getname=getname_flags:72 pathname=result->name:string' Added new event: probe:vfs_getname (on getname_flags:72 with pathname=result->name:string) You can now use it in all perf tools, such as: perf record -e probe:vfs_getname -aR sleep 1 But trying perf record: ./perf record -e probe:vfs_getname -aR sleep 1 event syntax error: 'probe:vfs_getname' \___ unsupported tracepoint libtraceevent is necessary for tracepoint support Run 'perf list' for a list of valid events The builtin tool like perf record needs libtraceevent to parse tracefs. But still the probe can be used by enabling via tracefs. Patch fixes the probe usage message to the user based on presence of libtraceevent. With the fix, # ./perf probe 'pmu:myprobe=schedule' Added new event: pmu:myprobe (on schedule) perf is not linked with libtraceevent, to use the new probe you can use tracefs: cd /sys/kernel/tracing/ echo 1 > events/pmu/myprobe/enable echo 1 > tracing_on cat trace_pipe Before removing the probe, echo 0 > events/pmu/myprobe/enable Signed-off-by: Athira Rajeev Cc: Andi Kleen Cc: Disha Goel Cc: Ian Rogers Cc: James Clark Cc: Jiri Olsa Cc: Kajol Jain Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Nageswara R Sastry Cc: Namhyung Kim Cc: linuxppc-dev@lists.ozlabs.org Link: https://lore.kernel.org/r/20230131134748.54567-1-atrajeev@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-probe.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'tools/perf/builtin-probe.c') diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c index ed73d0b89ca2..e72f6cea76f7 100644 --- a/tools/perf/builtin-probe.c +++ b/tools/perf/builtin-probe.c @@ -383,9 +383,18 @@ static int perf_add_probe_events(struct perf_probe_event *pevs, int npevs) /* Note that it is possible to skip all events because of blacklist */ if (event) { +#ifndef HAVE_LIBTRACEEVENT + pr_info("\nperf is not linked with libtraceevent, to use the new probe you can use tracefs:\n\n"); + pr_info("\tcd /sys/kernel/tracing/\n"); + pr_info("\techo 1 > events/%s/%s/enable\n", group, event); + pr_info("\techo 1 > tracing_on\n"); + pr_info("\tcat trace_pipe\n"); + pr_info("\tBefore removing the probe, echo 0 > events/%s/%s/enable\n", group, event); +#else /* Show how to use the event. */ pr_info("\nYou can now use it in all perf tools, such as:\n\n"); pr_info("\tperf record -e %s:%s -aR sleep 1\n\n", group, event); +#endif } out_cleanup: -- cgit v1.2.3