perf tools: Enhance parsing events tracepoint error output

Enhancing parsing events tracepoint error output. Adding
more verbose output when the tracepoint is not found or
the tracing event path cannot be access.

  $ sudo perf record -e sched:sched_krava ls
  event syntax error: 'sched:sched_krava'
                       \___ unknown tracepoint

  Error:  File /sys/kernel/debug/tracing//tracing/events/sched/sched_krava not found.
  Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

  Run 'perf list' for a list of valid events
  ...

  $ perf record -e sched:sched_krava ls
  event syntax error: 'sched:sched_krava'
                       \___ can't access trace events

  Error:  No permissions to read /sys/kernel/debug/tracing//tracing/events/sched/sched_krava
  Hint:   Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'

  Run 'perf list' for a list of valid events
  ...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1441615087-13886-6-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-events.c

@@ -387,15 +387,44 @@ int parse_events_add_cache(struct list_head *list, int *idx,
 	return add_event(list, idx, &attr, name, NULL);
 }
 
+static void tracepoint_error(struct parse_events_error *error, int err,
+			     char *sys, char *name)
+{
+	char help[BUFSIZ];
+
+	/*
+	 * We get error directly from syscall errno ( > 0),
+	 * or from encoded pointer's error ( < 0).
+	 */
+	err = abs(err);
+
+	switch (err) {
+	case EACCES:
+		error->str = strdup("can't access trace events");
+		break;
+	case ENOENT:
+		error->str = strdup("unknown tracepoint");
+		break;
+	default:
+		error->str = strdup("failed to add tracepoint");
+		break;
+	}
+
+	tracing_path__strerror_open_tp(err, help, sizeof(help), sys, name);
+	error->help = strdup(help);
+}
+
 static int add_tracepoint(struct list_head *list, int *idx,
 			  char *sys_name, char *evt_name,
 			  struct parse_events_error *error __maybe_unused)
 {
 	struct perf_evsel *evsel;
 
 	evsel = perf_evsel__newtp_idx(sys_name, evt_name, (*idx)++);
-	if (IS_ERR(evsel))
+	if (IS_ERR(evsel)) {
+		tracepoint_error(error, PTR_ERR(evsel), sys_name, evt_name);
 		return PTR_ERR(evsel);
+	}
 
 	list_add_tail(&evsel->node, list);
 	return 0;
@@ -413,7 +442,7 @@ static int add_tracepoint_multi_event(struct list_head *list, int *idx,
 	snprintf(evt_path, MAXPATHLEN, "%s/%s", tracing_events_path, sys_name);
 	evt_dir = opendir(evt_path);
 	if (!evt_dir) {
-		perror("Can't open event dir");
+		tracepoint_error(error, errno, sys_name, evt_name);
 		return -1;
 	}
 
@@ -453,7 +482,7 @@ static int add_tracepoint_multi_sys(struct list_head *list, int *idx,
 
 	events_dir = opendir(tracing_events_path);
 	if (!events_dir) {
-		perror("Can't open event dir");
+		tracepoint_error(error, errno, sys_name, evt_name);
 		return -1;
 	}
 

tools/perf/util/parse-events.y

@@ -371,28 +371,30 @@ event_legacy_tracepoint:
 PE_NAME '-' PE_NAME ':' PE_NAME
 {
 	struct parse_events_evlist *data = _data;
+	struct parse_events_error *error = data->error;
 	struct list_head *list;
 	char sys_name[128];
 	snprintf(&sys_name, 128, "%s-%s", $1, $3);
 
 	ALLOC_LIST(list);
-	ABORT_ON(parse_events_add_tracepoint(list, &data->idx, &sys_name, $5, data->error));
+	if (parse_events_add_tracepoint(list, &data->idx, &sys_name, $5, error)) {
+		if (error)
+			error->idx = @1.first_column;
+		return -1;
+	}
 	$$ = list;
 }
 |
 PE_NAME ':' PE_NAME
 {
 	struct parse_events_evlist *data = _data;
+	struct parse_events_error *error = data->error;
 	struct list_head *list;
 
 	ALLOC_LIST(list);
-	if (parse_events_add_tracepoint(list, &data->idx, $1, $3, data->error)) {
-		struct parse_events_error *error = data->error;
-
-		if (error) {
+	if (parse_events_add_tracepoint(list, &data->idx, $1, $3, error)) {
+		if (error)
 			error->idx = @1.first_column;
-			error->str = strdup("unknown tracepoint");
-		}
 		return -1;
 	}
 	$$ = list;