perf util: Add more debug message on failure path

It's helpful for debugging on tracing features.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeremy Eder <jeder@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>,
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/n/tip-rjysr9ljiesymgk4qblteaty@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/header.c

@@ -2803,8 +2803,10 @@ static int perf_evsel__prepare_tracepoint_event(struct perf_evsel *evsel,
 	}
 
 	event = pevent_find_event(pevent, evsel->attr.config);
-	if (event == NULL)
+	if (event == NULL) {
+		pr_debug("cannot find event format for %d\n", (int)evsel->attr.config);
 		return -1;
+	}
 
 	if (!evsel->name) {
 		snprintf(bf, sizeof(bf), "%s:%s", event->system, event->name);

tools/perf/util/trace-event-read.c

@@ -260,39 +260,53 @@ static int read_header_files(struct pevent *pevent)
 
 static int read_ftrace_file(struct pevent *pevent, unsigned long long size)
 {
+	int ret;
 	char *buf;
 
 	buf = malloc(size);
-	if (buf == NULL)
+	if (buf == NULL) {
+		pr_debug("memory allocation failure\n");
 		return -1;
+	}
 
-	if (do_read(buf, size) < 0) {
-		free(buf);
-		return -1;
+	ret = do_read(buf, size);
+	if (ret < 0) {
+		pr_debug("error reading ftrace file.\n");
+		goto out;
 	}
 
-	parse_ftrace_file(pevent, buf, size);
+	ret = parse_ftrace_file(pevent, buf, size);
+	if (ret < 0)
+		pr_debug("error parsing ftrace file.\n");
+out:
 	free(buf);
-	return 0;
+	return ret;
 }
 
 static int read_event_file(struct pevent *pevent, char *sys,
 			    unsigned long long size)
 {
+	int ret;
 	char *buf;
 
 	buf = malloc(size);
-	if (buf == NULL)
+	if (buf == NULL) {
+		pr_debug("memory allocation failure\n");
 		return -1;
+	}
 
-	if (do_read(buf, size) < 0) {
+	ret = do_read(buf, size);
+	if (ret < 0) {
 		free(buf);
-		return -1;
+		goto out;
 	}
 
-	parse_event_file(pevent, buf, size, sys);
+	ret = parse_event_file(pevent, buf, size, sys);
+	if (ret < 0)
+		pr_debug("error parsing event file.\n");
+out:
 	free(buf);
-	return 0;
+	return ret;
 }
 
 static int read_ftrace_files(struct pevent *pevent)
@@ -345,25 +359,30 @@ static int read_saved_cmdline(struct pevent *pevent)
 {
 	unsigned long long size;
 	char *buf;
+	int ret;
 
 	/* it can have 0 size */
 	size = read8(pevent);
 	if (!size)
 		return 0;
 
 	buf = malloc(size + 1);
-	if (buf == NULL)
+	if (buf == NULL) {
+		pr_debug("memory allocation failure\n");
 		return -1;
+	}
 
-	if (do_read(buf, size) < 0) {
-		free(buf);
-		return -1;
+	ret = do_read(buf, size);
+	if (ret < 0) {
+		pr_debug("error reading saved cmdlines\n");
+		goto out;
 	}
 
 	parse_saved_cmdline(pevent, buf, size);
-
+	ret = 0;
+out:
 	free(buf);
-	return 0;
+	return ret;
 }
 
 ssize_t trace_report(int fd, struct trace_event *tevent, bool __repipe)