[RFC PATCH v4 26/29] perf record: Probe at kprobe points

[Wang Nan]

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.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/perf/builtin-record.c  | 14 ++++++++++++++
 tools/perf/util/bpf-loader.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  2 ++
 3 files changed, 61 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index c3efdfb..9297800 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -27,6 +27,7 @@
 #include "util/cpumap.h"
 #include "util/thread_map.h"
 #include "util/data.h"
+#include "util/bpf-loader.h"
 
 #include <unistd.h>
 #include <sched.h>
@@ -957,6 +958,18 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 		usage_with_options(record_usage, record_options);
 	}
 
+	/*
+	 * 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.
+	 */
+	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");
+		return err;
+	}
+
 	symbol__init(NULL);
 
 	if (symbol_conf.kptr_restrict)
@@ -1011,5 +1024,6 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 out_symbol_exit:
 	perf_evlist__delete(rec->evlist);
 	symbol__exit();
+	bpf__unprobe();
 	return err;
 }
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 1022729..f5d5f3e 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -179,3 +179,48 @@ void bpf__clear(void)
 	bpf_object__for_each(obj, tmp)
 		bpf_object__close(obj);
 }
+
+static bool is_probing = false;
+
+int bpf__unprobe(void)
+{
+	struct strlist *dellist;
+	int ret;
+
+	if (!is_probing)
+		return 0;
+
+	dellist = strlist__new(true, PERF_BPF_PROBE_GROUP ":*");
+	if (!dellist) {
+		pr_err("Failed to create dellist when unprobing\n");
+		return -ENOMEM;
+	}
+
+	ret = del_perf_probe_events(dellist);
+	strlist__delete(dellist);
+	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;
+
+	err = add_perf_probe_events(probe_event_array,
+				    nr_probe_events,
+				    MAX_PROBES, 0);
+	/* 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 43d7b99..1127880 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -8,6 +8,8 @@
 #define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
 
 int bpf__prepare_load(const char *filename);
+int bpf__probe(void);
+int bpf__unprobe(void);
 
 void bpf__clear(void);
 #endif
-- 
1.8.3.4

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