perf parse: Report initial event parsing error

Record the first event parsing error and report. Implementing feedback
from Jiri Olsa:

  https://lkml.org/lkml/2019/10/28/680

An example error is:

  $ tools/perf/perf stat -e c/c/
  WARNING: multiple event parsing errors
  event syntax error: 'c/c/'
                         \___ unknown term

  valid terms: event,filter_rem,filter_opc0,edge,filter_isoc,filter_tid,filter_loc,filter_nc,inv,umask,filter_opc1,tid_en,thresh,filter_all_op,filter_not_nm,filter_state,filter_nm,config,config1,config2,name,period,percore

Initial error:

  event syntax error: 'c/c/'
                      \___ Cannot find PMU `c'. Missing kernel support?
  Run 'perf list' for a list of valid events

   Usage: perf stat [<options>] [<command>]

      -e, --event <event>   event selector. use 'perf list' to list available events

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Allison Randal <allison@lohutok.net>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20191116074652.9960-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-events.c

@@ -189,12 +189,29 @@ void parse_events__handle_error(struct parse_events_error *err, int idx,
 		free(help);
 		return;
 	}
-	WARN_ONCE(err->str, "WARNING: multiple event parsing errors\n");
-	err->idx = idx;
-	free(err->str);
-	err->str = str;
-	free(err->help);
-	err->help = help;
+	switch (err->num_errors) {
+	case 0:
+		err->idx = idx;
+		err->str = str;
+		err->help = help;
+		break;
+	case 1:
+		err->first_idx = err->idx;
+		err->idx = idx;
+		err->first_str = err->str;
+		err->str = str;
+		err->first_help = err->help;
+		err->help = help;
+		break;
+	default:
+		WARN_ONCE(1, "WARNING: multiple event parsing errors\n");
+		free(err->str);
+		err->str = str;
+		free(err->help);
+		err->help = help;
+		break;
+	}
+	err->num_errors++;
 }
 
 struct tracepoint_path *tracepoint_id_to_path(u64 config)
@@ -1349,7 +1366,7 @@ int parse_events_add_pmu(struct parse_events_state *parse_state,
 		if (asprintf(&err_str,
 				"Cannot find PMU `%s'. Missing kernel support?",
 				name) >= 0)
-			parse_events__handle_error(err, -1, err_str, NULL);
+			parse_events__handle_error(err, 0, err_str, NULL);
 		return -EINVAL;
 	}
 
@@ -2007,15 +2024,14 @@ static int get_term_width(void)
 	return ws.ws_col > MAX_WIDTH ? MAX_WIDTH : ws.ws_col;
 }
 
-void parse_events_print_error(struct parse_events_error *err,
-			      const char *event)
+static void __parse_events_print_error(int err_idx, const char *err_str,
+				const char *err_help, const char *event)
 {
 	const char *str = "invalid or unsupported event: ";
 	char _buf[MAX_WIDTH];
 	char *buf = (char *) event;
 	int idx = 0;
-
-	if (err->str) {
+	if (err_str) {
 		/* -2 for extra '' in the final fprintf */
 		int width       = get_term_width() - 2;
 		int len_event   = strlen(event);
@@ -2038,8 +2054,8 @@ void parse_events_print_error(struct parse_events_error *err,
 		buf = _buf;
 
 		/* We're cutting from the beginning. */
-		if (err->idx > max_err_idx)
-			cut = err->idx - max_err_idx;
+		if (err_idx > max_err_idx)
+			cut = err_idx - max_err_idx;
 
 		strncpy(buf, event + cut, max_len);
 
@@ -2052,16 +2068,33 @@ void parse_events_print_error(struct parse_events_error *err,
 			buf[max_len] = 0;
 		}
 
-		idx = len_str + err->idx - cut;
+		idx = len_str + err_idx - cut;
 	}
 
 	fprintf(stderr, "%s'%s'\n", str, buf);
 	if (idx) {
-		fprintf(stderr, "%*s\\___ %s\n", idx + 1, "", err->str);
-		if (err->help)
-			fprintf(stderr, "\n%s\n", err->help);
-		zfree(&err->str);
-		zfree(&err->help);
+		fprintf(stderr, "%*s\\___ %s\n", idx + 1, "", err_str);
+		if (err_help)
+			fprintf(stderr, "\n%s\n", err_help);
+	}
+}
+
+void parse_events_print_error(struct parse_events_error *err,
+			      const char *event)
+{
+	if (!err->num_errors)
+		return;
+
+	__parse_events_print_error(err->idx, err->str, err->help, event);
+	zfree(&err->str);
+	zfree(&err->help);
+
+	if (err->num_errors > 1) {
+		fputs("\nInitial error:\n", stderr);
+		__parse_events_print_error(err->first_idx, err->first_str,
+					err->first_help, event);
+		zfree(&err->first_str);
+		zfree(&err->first_help);
 	}
 }
 
@@ -2071,8 +2104,11 @@ int parse_events_option(const struct option *opt, const char *str,
 			int unset __maybe_unused)
 {
 	struct evlist *evlist = *(struct evlist **)opt->value;
-	struct parse_events_error err = { .idx = 0, };
-	int ret = parse_events(evlist, str, &err);
+	struct parse_events_error err;
+	int ret;
+
+	bzero(&err, sizeof(err));
+	ret = parse_events(evlist, str, &err);
 
 	if (ret) {
 		parse_events_print_error(&err, str);