[PATCH] perf tools: Sync setting of real bpf events with placeholder

[Wang Nan]

In this patch, when adding real events described in BPF objects, sync
filter and tracking settings with previous dummy placeholder. After
this patch, command like:

 # perf record --test-filter.o --exclude-perf ls

work as we expect.

After all settings are synced, we remove those placeholder from evlist
so they won't appear in the final perf.data.

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>
---
 tools/perf/util/bpf-loader.c |  8 ++++-
 tools/perf/util/bpf-loader.h |  1 +
 tools/perf/util/evlist.c     | 75 +++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 79 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 2880dbf..3400538 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -325,6 +325,12 @@ int bpf__foreach_tev(bpf_prog_iter_callback_t func, void *arg)
 	int err;
 
 	bpf_object__for_each_safe(obj, tmp) {
+		const char *obj_name;
+
+		obj_name = bpf_object__get_name(obj);
+		if (!obj_name)
+			obj_name = "[unknown].o";
+
 		bpf_object__for_each_program(prog, obj) {
 			struct probe_trace_event *tev;
 			struct perf_probe_event *pev;
@@ -348,7 +354,7 @@ int bpf__foreach_tev(bpf_prog_iter_callback_t func, void *arg)
 					return fd;
 				}
 
-				err = (*func)(tev, fd, arg);
+				err = (*func)(tev, obj_name, fd, arg);
 				if (err) {
 					pr_debug("bpf: call back failed, stop iterate\n");
 					return err;
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index 34656f8..5bac423 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -13,6 +13,7 @@
 #define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
 
 typedef int (*bpf_prog_iter_callback_t)(struct probe_trace_event *tev,
+					const char *obj_name,
 					int fd, void *arg);
 
 #ifdef HAVE_LIBBPF_SUPPORT
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 29212dc..7e36563 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -197,7 +197,54 @@ error:
 	return -ENOMEM;
 }
 
-static int add_bpf_event(struct probe_trace_event *tev, int fd,
+static void sync_with_bpf_placeholder(struct perf_evlist *evlist,
+				      const char *obj_name,
+				      struct list_head *list)
+{
+	struct perf_evsel *dummy_evsel, *pos;
+
+	const char *filter;
+	bool tracking_set = false;
+	bool found = false;
+
+	evlist__for_each(evlist, dummy_evsel) {
+		if (!perf_evsel__is_bpf_placeholder(dummy_evsel))
+			continue;
+
+		if (strcmp(dummy_evsel->name, obj_name) == 0) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found) {
+		pr_debug("Failed to find dummy event of '%s'\n",
+			 obj_name);
+		return;
+	}
+
+	filter = dummy_evsel->filter;
+
+	list_for_each_entry(pos, list, node) {
+		if (filter && perf_evsel__set_filter(pos, filter)) {
+			pr_debug("Failed to set filter '%s' to evsel %s\n",
+				 filter, pos->name);
+		}
+
+		/* Sync tracking */
+		if (dummy_evsel->tracking && !tracking_set)
+			pos->tracking = tracking_set = true;
+
+		/*
+		 * If someday we allow to add config terms or modifiers
+		 * to placeholder, we should sync them with real events
+		 * here. Currently only tracking needs to be considered.
+		 */
+	}
+}
+
+static int add_bpf_event(struct probe_trace_event *tev,
+			 const char *obj_name, int fd,
 			 void *arg)
 {
 	struct perf_evlist *evlist = arg;
@@ -205,8 +252,8 @@ static int add_bpf_event(struct probe_trace_event *tev, int fd,
 	struct list_head list;
 	int err, idx, entries;
 
-	pr_debug("add bpf event %s:%s and attach bpf program %d\n",
-			tev->group, tev->event, fd);
+	pr_debug("add bpf event %s:%s and attach bpf program %d (from %s)\n",
+			tev->group, tev->event, fd, obj_name);
 	INIT_LIST_HEAD(&list);
 	idx = evlist->nr_entries;
 
@@ -228,13 +275,33 @@ static int add_bpf_event(struct probe_trace_event *tev, int fd,
 	list_for_each_entry(pos, &list, node)
 		pos->bpf_fd = fd;
 	entries = idx - evlist->nr_entries;
+
+	sync_with_bpf_placeholder(evlist, obj_name, &list);
+	/*
+	 * Currectly we don't need to link those new events at the
+	 * same place where dummy node reside because order of
+	 * events in cmdline won't be used after
+	 * 'perf_evlist__add_bpf'.
+	 */
 	perf_evlist__splice_list_tail(evlist, &list, entries);
 	return 0;
 }
 
 int perf_evlist__add_bpf(struct perf_evlist *evlist)
 {
-	return bpf__foreach_tev(add_bpf_event, evlist);
+	struct perf_evsel *pos, *n;
+	int err;
+
+	err = bpf__foreach_tev(add_bpf_event, evlist);
+
+	evlist__for_each_safe(evlist, n, pos) {
+		if (perf_evsel__is_bpf_placeholder(pos)) {
+			list_del_init(&pos->node);
+			perf_evsel__delete(pos);
+			evlist->nr_entries--;
+		}
+	}
+	return err;
 }
 
 static int perf_evlist__add_attrs(struct perf_evlist *evlist,
-- 
1.8.3.4

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