[PATCH 03/32] perf tools: Introduce dummy evsel

[Wang Nan]

This patch allows linking dummy evsel onto evlist as a placeholder. It
is for following patch which allows passing BPF object using '--event
object.o'.

Doesn't link other event selectors, if passing a BPF object file to
'--event', nothing is linked onto evlist. Instead, events described in
BPF object file are probed and linked in a delayed manner because we
want do all probing work together. Therefore, evsel for events in BPF
object would be linked at the end of evlist. Which causes a small
problem that, if passing '--filter' setting after object file, the
filter option won't be correctly applied to those events.

This patch links dummy onto evlist, so following --filter can be
collected by the dummy evsel. For this reason dummy evsels are set to
PERF_TYPE_TRACEPOINT.

Due to the possibility of existance of dummy evsel,
perf_evlist__purge_dummy() must be called right after parse_options().
This patch adds it to record, top, trace and stat builtin commands.
Further patch moves it down after real BPF events are processed with.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@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: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/builtin-record.c    |  2 ++
 tools/perf/builtin-stat.c      |  1 +
 tools/perf/builtin-top.c       |  1 +
 tools/perf/builtin-trace.c     |  1 +
 tools/perf/util/evlist.c       | 19 +++++++++++++++++++
 tools/perf/util/evlist.h       |  1 +
 tools/perf/util/evsel.c        | 32 ++++++++++++++++++++++++++++++++
 tools/perf/util/evsel.h        |  6 ++++++
 tools/perf/util/parse-events.c | 25 +++++++++++++++++++++----
 9 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a660022..81829de 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1112,6 +1112,8 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 
 	argc = parse_options(argc, argv, record_options, record_usage,
 			    PARSE_OPT_STOP_AT_NON_OPTION);
+	perf_evlist__purge_dummy(rec->evlist);
+
 	if (!argc && target__none(&rec->opts.target))
 		usage_with_options(record_usage, record_options);
 
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 7aa039b..99b62f1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -1208,6 +1208,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 
 	argc = parse_options(argc, argv, options, stat_usage,
 		PARSE_OPT_STOP_AT_NON_OPTION);
+	perf_evlist__purge_dummy(evsel_list);
 
 	interval = stat_config.interval;
 
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 8c465c8..246203b 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1198,6 +1198,7 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
 	perf_config(perf_top_config, &top);
 
 	argc = parse_options(argc, argv, options, top_usage, 0);
+	perf_evlist__purge_dummy(top.evlist);
 	if (argc)
 		usage_with_options(top_usage, options);
 
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 2f1162d..ef5fde6 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3080,6 +3080,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
 
 	argc = parse_options_subcommand(argc, argv, trace_options, trace_subcommands,
 				 trace_usage, PARSE_OPT_STOP_AT_NON_OPTION);
+	perf_evlist__purge_dummy(trace.evlist);
 
 	if (trace.trace_pgfaults) {
 		trace.opts.sample_address = true;
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index e9a5d43..30fc327 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1694,3 +1694,22 @@ void perf_evlist__set_tracking_event(struct perf_evlist *evlist,
 
 	tracking_evsel->tracking = true;
 }
+
+void perf_evlist__purge_dummy(struct perf_evlist *evlist)
+{
+	struct perf_evsel *pos, *n;
+
+	/*
+	 * Remove all dummy events.
+	 * During linking, we don't touch anything except link
+	 * it into evlist. As a result, we don't
+	 * need to adjust evlist->nr_entries during removal.
+	 */
+
+	evlist__for_each_safe(evlist, n, pos) {
+		if (perf_evsel__is_dummy(pos)) {
+			list_del_init(&pos->node);
+			perf_evsel__delete(pos);
+		}
+	}
+}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 436e358..df4820e 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -180,6 +180,7 @@ bool perf_evlist__valid_read_format(struct perf_evlist *evlist);
 void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
 				   struct list_head *list,
 				   int nr_entries);
+void perf_evlist__purge_dummy(struct perf_evlist *evlist);
 
 static inline struct perf_evsel *perf_evlist__first(struct perf_evlist *evlist)
 {
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index b096ef7..35947f5 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -212,6 +212,7 @@ void perf_evsel__init(struct perf_evsel *evsel,
 	evsel->sample_size = __perf_evsel__sample_size(attr->sample_type);
 	perf_evsel__calc_id_pos(evsel);
 	evsel->cmdline_group_boundary = false;
+	evsel->is_dummy = false;
 }
 
 struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx)
@@ -224,6 +225,37 @@ struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx)
 	return evsel;
 }
 
+struct perf_evsel *perf_evsel__new_dummy(const char *name)
+{
+	struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
+
+	if (!evsel)
+		return NULL;
+
+	/*
+	 * Don't need call perf_evsel__init() for dummy evsel.
+	 * Keep it simple.
+	 */
+	evsel->name = strdup(name);
+	if (!evsel->name)
+		goto out_free;
+
+	INIT_LIST_HEAD(&evsel->node);
+	INIT_LIST_HEAD(&evsel->config_terms);
+
+	evsel->cmdline_group_boundary = false;
+	/*
+	 * Set dummy evsel as TRACEPOINT event so it can collect filter
+	 * options.
+	 */
+	evsel->attr.type = PERF_TYPE_TRACEPOINT;
+	evsel->is_dummy = true;
+	return evsel;
+out_free:
+	free(evsel);
+	return NULL;
+}
+
 struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int idx)
 {
 	struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 93ac6b1..443995b 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -114,6 +114,7 @@ struct perf_evsel {
 	struct perf_evsel	*leader;
 	char			*group_name;
 	bool			cmdline_group_boundary;
+	bool			is_dummy;
 	struct list_head	config_terms;
 };
 
@@ -149,6 +150,11 @@ int perf_evsel__object_config(size_t object_size,
 			      void (*fini)(struct perf_evsel *evsel));
 
 struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx);
+struct perf_evsel *perf_evsel__new_dummy(const char *name);
+static inline bool perf_evsel__is_dummy(struct perf_evsel *evsel)
+{
+	return evsel->is_dummy;
+}
 
 static inline struct perf_evsel *perf_evsel__new(struct perf_event_attr *attr)
 {
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 14cd7e3..71d91fb 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1141,7 +1141,7 @@ int parse_events(struct perf_evlist *evlist, const char *str,
 	perf_pmu__parse_cleanup();
 	if (!ret) {
 		int entries = data.idx - evlist->nr_entries;
-		struct perf_evsel *last;
+		struct perf_evsel *last = NULL;
 
 		if (!list_empty(&data.list)) {
 			last = list_entry(data.list.prev,
@@ -1149,8 +1149,25 @@ int parse_events(struct perf_evlist *evlist, const char *str,
 			last->cmdline_group_boundary = true;
 		}
 
-		perf_evlist__splice_list_tail(evlist, &data.list, entries);
-		evlist->nr_groups += data.nr_groups;
+		if (last && perf_evsel__is_dummy(last)) {
+			if (!list_is_singular(&data.list)) {
+				parse_events_evlist_error(&data, 0,
+					"Dummy evsel error: not on a singular list");
+				return -1;
+			}
+			/*
+			 * We are introducing a dummy event. Don't touch
+			 * anything, just link it.
+			 *
+			 * Don't use perf_evlist__splice_list_tail() since
+			 * it alerts evlist->nr_entries, which affect header
+			 * of resulting perf.data.
+			 */
+			list_splice_tail(&data.list, &evlist->entries);
+		} else {
+			perf_evlist__splice_list_tail(evlist, &data.list, entries);
+			evlist->nr_groups += data.nr_groups;
+		}
 
 		return 0;
 	}
@@ -1256,7 +1273,7 @@ foreach_evsel_in_last_glob(struct perf_evlist *evlist,
 	struct perf_evsel *last = NULL;
 	int err;
 
-	if (evlist->nr_entries > 0)
+	if (!list_empty(&evlist->entries))
 		last = perf_evlist__last(evlist);
 
 	do {
-- 
1.8.3.4

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