[PATCH 06/22] perf tools: Collect perf_evsel in BPF object files

[Wang Nan]

This patch collects 'struct perf_evsel' for every probing points in BPF
object file(s) and fill 'struct evlist'. The previous introduced dummy
event now removed. After this patch, following command:

 # perf record --event filter.o ls

Can trace on each probing points defined in filter.o.

The core of this patch is bpf__foreach_tev(), which calls a callback
function for each 'struct probe_trace_event' events for a bpf program
with their file descriptors. Callback function add_bpf_event()
creates evsels by calling parse_events_add_tracepoint().

Since bpf-loader.c will not be built if libbpf is turned off, an empty
bpf__foreach_tev() is defined in bpf-loader.h to avoid compiling
error.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Brendan Gregg <brendan.d.gregg@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kaixu Xia <xiakaixu@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/ebpf-6yw9eg0ej3l4jnqhinngkw86@xxxxxxxxxxxxxx
---
 tools/perf/util/bpf-loader.c   | 40 ++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h   | 14 ++++++++++++
 tools/perf/util/parse-events.c | 49 ++++++++++++++++++++++++++++++++++++------
 3 files changed, 96 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 7279558..aa784a4 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -255,6 +255,46 @@ int bpf__load(struct bpf_object *obj)
 	return 0;
 }
 
+int bpf__foreach_tev(struct bpf_object *obj,
+		     bpf_prog_iter_callback_t func,
+		     void *arg)
+{
+	struct bpf_program *prog;
+	int err;
+
+	bpf_object__for_each_program(prog, obj) {
+		struct probe_trace_event *tev;
+		struct perf_probe_event *pev;
+		struct bpf_prog_priv *priv;
+		int i, fd;
+
+		err = bpf_program__get_private(prog,
+				(void **)&priv);
+		if (err || !priv) {
+			pr_debug("bpf: failed to get private field\n");
+			return -EINVAL;
+		}
+
+		pev = &priv->pev;
+		for (i = 0; i < pev->ntevs; i++) {
+			tev = &pev->tevs[i];
+
+			fd = bpf_program__fd(prog);
+			if (fd < 0) {
+				pr_debug("bpf: failed to get file descriptor\n");
+				return fd;
+			}
+
+			err = (*func)(tev, fd, arg);
+			if (err) {
+				pr_debug("bpf: call back failed, stop iterate\n");
+				return err;
+			}
+		}
+	}
+	return 0;
+}
+
 #define bpf__strerror_head(err, buf, size) \
 	char sbuf[STRERR_BUFSIZE], *emsg;\
 	if (!size)\
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index b091ceb..a8f25ee 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -8,11 +8,15 @@
 #include <linux/compiler.h>
 #include <linux/err.h>
 #include <string.h>
+#include "probe-event.h"
 #include "debug.h"
 
 struct bpf_object;
 #define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
 
+typedef int (*bpf_prog_iter_callback_t)(struct probe_trace_event *tev,
+					int fd, void *arg);
+
 #ifdef HAVE_LIBBPF_SUPPORT
 struct bpf_object *bpf__prepare_load(const char *filename);
 
@@ -26,6 +30,8 @@ int bpf__strerror_probe(struct bpf_object *obj, int err,
 int bpf__load(struct bpf_object *obj);
 int bpf__strerror_load(struct bpf_object *obj, int err,
 		       char *buf, size_t size);
+int bpf__foreach_tev(struct bpf_object *obj,
+		     bpf_prog_iter_callback_t func, void *arg);
 #else
 static inline struct bpf_object *
 bpf__prepare_load(const char *filename __maybe_unused)
@@ -41,6 +47,14 @@ static inline int bpf__unprobe(struct bpf_object *obj __maybe_unused) { return 0
 static inline int bpf__load(struct bpf_object *obj __maybe_unused) { return 0; }
 
 static inline int
+bpf__foreach_tev(struct bpf_object *obj __maybe_unused,
+		 bpf_prog_iter_callback_t func __maybe_unused,
+		 void *arg __maybe_unused)
+{
+	return 0;
+}
+
+static inline int
 __bpf_strerror(char *buf, size_t size)
 {
 	if (!size)
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index cfeaa7b..3c4842c 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -530,12 +530,46 @@ static int add_tracepoint_multi_sys(struct list_head *list, int *idx,
 	return ret;
 }
 
+struct __add_bpf_event_param {
+	struct parse_events_evlist *data;
+	struct list_head *list;
+};
+
+static int add_bpf_event(struct probe_trace_event *tev, int fd,
+			 void *_param)
+{
+	struct __add_bpf_event_param *param = _param;
+	struct parse_events_evlist *evlist = param->data;
+	struct list_head *list = param->list;
+	int err;
+
+	pr_debug("add bpf event %s:%s and attach bpf program %d\n",
+			tev->group, tev->event, fd);
+
+	err = parse_events_add_tracepoint(list, &evlist->idx, tev->group,
+					  tev->event, evlist->error, NULL);
+	if (err) {
+		struct perf_evsel *evsel, *tmp;
+
+		pr_debug("Failed to add BPF event %s:%s\n",
+			 tev->group, tev->event);
+		list_for_each_entry_safe(evsel, tmp, list, node) {
+			list_del(&evsel->node);
+			perf_evsel__delete(evsel);
+		}
+		return err;
+	}
+	pr_debug("adding %s:%s\n", tev->group, tev->event);
+	return 0;
+}
+
 int parse_events_load_bpf_obj(struct parse_events_evlist *data,
 			      struct list_head *list,
 			      struct bpf_object *obj)
 {
 	int err;
 	char errbuf[BUFSIZ];
+	struct __add_bpf_event_param param = {data, list};
 	static bool registered_unprobe_atexit = false;
 
 	if (IS_ERR(obj) || !obj) {
@@ -562,13 +596,14 @@ int parse_events_load_bpf_obj(struct parse_events_evlist *data,
 		goto errout;
 	}
 
-	/*
-	 * Temporary add a dummy event here so we can check whether
-	 * basic bpf loader works. Following patches will replace
-	 * dummy event by useful evsels.
-	 */
-	return parse_events_add_numeric(data, list, PERF_TYPE_SOFTWARE,
-					PERF_COUNT_SW_DUMMY, NULL);
+	err = bpf__foreach_tev(obj, add_bpf_event, &param);
+	if (err) {
+		snprintf(errbuf, sizeof(errbuf),
+			 "Attach events in BPF object failed");
+		goto errout;
+	}
+
+	return 0;
 errout:
 	data->error->help = strdup("(add -v to see detail)");
 	data->error->str = strdup(errbuf);
-- 
1.8.3.4

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