[RFC PATCH v7 32/37] perf record: Probe at kprobe points

Wang Nan
2015-06-12T05:38:46Z

In this patch, kprobe points are created using add_perf_probe_events.
Since all events are already grouped together in an array, calling
add_perf_probe_events() once creates all of them.

probe_conf.max_probes is set to MAX_PROBES to support glob matching.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
tools/perf/builtin-record.c | 18 ++++++++++++++++-
tools/perf/util/bpf-loader.c | 48 ++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/bpf-loader.h | 4 ++++
3 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d3731cc..29f7b40 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -29,6 +29,7 @@
#include "util/data.h"
#include "util/auxtrace.h"
#include "util/parse-branch-options.h"
+#include "util/bpf-loader.h"

#include <unistd.h>
#include <sched.h>
@@ -1106,7 +1107,21 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
if (err)
return err;

- err = -ENOMEM;
+ /*
+ * bpf__probe must be called before symbol__init() because we
+ * need init_symbol_maps. If called after symbol__init,
+ * symbol_conf.sort_by_name won't take effect.
+ *
+ * bpf__unprobe() is safe even if bpf__probe() failed, and it
+ * also calls symbol__init. Therefore, goto out_symbol_exit
+ * is safe when probe failed.
+ */
+ err = bpf__probe();
+ if (err) {
+ pr_err("Probing at events in BPF object failed.\n");
+ pr_err("Try perf probe -d '*' to remove existing probe events.\n");
+ goto out_symbol_exit;
+ }

symbol__init(NULL);

@@ -1167,6 +1182,7 @@ out_symbol_exit:
perf_evlist__delete(rec->evlist);
symbol__exit();
auxtrace_record__free(rec->itr);
+ bpf__unprobe();
return err;
}

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index a202702..cb11561 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -191,3 +191,51 @@ void bpf__clear(void)
bpf_object__for_each(obj, tmp)
bpf_object__close(obj);
}
+
+static bool is_probing = false;
+
+int bpf__unprobe(void)
+{
+ struct strfilter *delfilter;
+ int ret;
+
+ if (!is_probing)
+ return 0;
+
+ delfilter = strfilter__new(PERF_BPF_PROBE_GROUP ":*", NULL);
+ if (!delfilter) {
+ pr_err("Failed to create delfilter when unprobing\n");
+ return -ENOMEM;
+ }
+
+ ret = del_perf_probe_events(delfilter);
+ strfilter__delete(delfilter);
+ if (ret < 0 && is_probing)
+ pr_err("Error: failed to delete events: %s\n",
+ strerror(-ret));
+ else
+ is_probing = false;
+ return ret < 0 ? ret : 0;
+}
+
+int bpf__probe(void)
+{
+ int err;
+
+ if (nr_probe_events <= 0)
+ return 0;
+
+ probe_conf.max_probes = MAX_PROBES;
+ /* Let add_perf_probe_events keeps probe_trace_event */
+ err = add_perf_probe_events(probe_event_array,
+ nr_probe_events,
+ false);
+
+ /* add_perf_probe_events return negative when fail */
+ if (err < 0)
+ pr_err("bpf probe: failed to probe events\n");
+ else
+ is_probing = true;
+
+ return err < 0 ? err : 0;
+}
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index 5a3c954..374aec0 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -12,6 +12,8 @@

#ifdef HAVE_LIBBPF_SUPPORT
int bpf__prepare_load(const char *filename, bool source);
+int bpf__probe(void);
+int bpf__unprobe(void);

void bpf__clear(void);
#else
@@ -22,6 +24,8 @@ static inline int bpf__prepare_load(const char *filename __maybe_unused,
return -1;
}

+static inline int bpf__probe(void) { return 0; }
+static inline int bpf__unprobe(void) { return 0; }
static inline void bpf__clear(void) { }
#endif
#endif
--
1.8.3.4