perf trace: Fix segfault when trying to trace events by cgroup

  # ./perf trace -e sched:sched_switch -G test -a sleep 1
  perf: Segmentation fault
  Obtained 11 stack frames.
  ./perf(sighandler_dump_stack+0x43) [0x55cfdc636db3]
  /lib/x86_64-linux-gnu/libc.so.6(+0x3efcf) [0x7fd23eecafcf]
  ./perf(parse_cgroups+0x36) [0x55cfdc673f36]
  ./perf(+0x3186ed) [0x55cfdc70d6ed]
  ./perf(parse_options_subcommand+0x629) [0x55cfdc70e999]
  ./perf(cmd_trace+0x9c2) [0x55cfdc5ad6d2]
  ./perf(+0x1e8ae0) [0x55cfdc5ddae0]
  ./perf(+0x1e8ded) [0x55cfdc5ddded]
  ./perf(main+0x370) [0x55cfdc556f00]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe6) [0x7fd23eeadb96]
  ./perf(_start+0x29) [0x55cfdc557389]
  Segmentation fault
  #

 It happens because "struct trace" in option->value is passed to the
 parse_cgroups function instead of "struct evlist".

Fixes: 9ea42ba4 ("perf trace: Support setting cgroups as targets")
Signed-off-by: Stanislav Ivanichkin <sivanichkin@yandex-team.ru>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
Link: http://lore.kernel.org/lkml/20201027094357.94881-1-sivanichkin@yandex-team.ruSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -4639,9 +4639,9 @@ static int trace__parse_events_option(const struct option *opt, const char *str,
 	err = 0;
 
 	if (lists[0]) {
-		struct option o = OPT_CALLBACK('e', "event", &trace->evlist, "event",
-					       "event selector. use 'perf list' to list available events",
-					       parse_events_option);
+		struct option o = {
+			.value = &trace->evlist,
+		};
 		err = parse_events_option(&o, lists[0], 0);
 	}
 out:
@@ -4655,9 +4655,12 @@ static int trace__parse_cgroups(const struct option *opt, const char *str, int u
 {
 	struct trace *trace = opt->value;
 
-	if (!list_empty(&trace->evlist->core.entries))
-		return parse_cgroups(opt, str, unset);
-
+	if (!list_empty(&trace->evlist->core.entries)) {
+		struct option o = {
+			.value = &trace->evlist,
+		};
+		return parse_cgroups(&o, str, unset);
+	}
 	trace->cgroup = evlist__findnew_cgroup(trace->evlist, str);
 
 	return 0;