[RFC PATCH 2/5] perf trace: Improve error message when receive non-tracepoint events

[Wang Nan]

Before this patch, strange error message is provided if passed a
non-tracepoint event to 'perf trace':

 # perf trace -a  --ev cycles sleep 1
 Failed to set filter "common_pid != 27500" on event cycles with 22 (Invalid argument)

This is because 'perf trace' accepts all valid event during cmdline
parsing, but since it need setting filter to events, actually user
can pass tracepoints with '--ev' only.

This patch validate evlist, report error earlier:

 # ./perf trace -a  --ev cycles sleep 1
 Only support tracepoint events!

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/builtin-trace.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 6c52f3c..2deb3f0 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2525,6 +2525,17 @@ out_enomem:
 	goto out;
 }
 
+static int validate_evlist(struct perf_evlist *evlist)
+{
+	struct perf_evsel *evsel;
+
+	evlist__for_each(evlist, evsel) {
+		if (evsel->attr.type != PERF_TYPE_TRACEPOINT)
+			return -EINVAL;
+	}
+	return 0;
+}
+
 static int trace__run(struct trace *trace, int argc, const char **argv)
 {
 	struct perf_evlist *evlist = trace->evlist;
@@ -3113,6 +3124,11 @@ 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);
 
+	if (validate_evlist(trace.evlist)) {
+		pr_err("Only support tracepoint events!\n");
+		return -EINVAL;
+	}
+
 	if (trace.trace_pgfaults) {
 		trace.opts.sample_address = true;
 		trace.opts.sample_time = true;
-- 
1.8.3.4