perf daemon: Avoid msan warnings on send_cmd

As a full union is always sent, ensure all bytes of the union are
initialized with memset to avoid msan warnings of use of uninitialized
memory.

An example warning from the daemon test:

Uninitialized bytes in __interceptor_write at offset 71 inside [0x7ffd98da6280, 72)
==11602==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x5597edccdbe4 in ion tools/lib/perf/lib.c:18:6
    #1 0x5597edccdbe4 in writen tools/lib/perf/lib.c:47:9
    #2 0x5597ed221d30 in send_cmd tools/perf/builtin-daemon.c:1376:22
    #3 0x5597ed21b48c in cmd_daemon tools/perf/builtin-daemon.c
    #4 0x5597ed1d6b67 in run_builtin tools/perf/perf.c:313:11
    #5 0x5597ed1d6036 in handle_internal_command tools/perf/perf.c:365:8
    #6 0x5597ed1d6036 in run_argv tools/perf/perf.c:409:2
    #7 0x5597ed1d6036 in main tools/perf/perf.c:539:3

SUMMARY: MemorySanitizer: use-of-uninitialized-value tools/lib/perf/lib.c:18:6 in ion
Exiting

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@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>
Link: http://lore.kernel.org/lkml/20210617055554.1917997-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/builtin-daemon.c

@@ -1403,8 +1403,10 @@ static int send_cmd(struct daemon *daemon, union cmd *cmd)
 
 static int send_cmd_list(struct daemon *daemon)
 {
-	union cmd cmd = { .cmd = CMD_LIST, };
+	union cmd cmd;
 
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.list.cmd = CMD_LIST;
 	cmd.list.verbose = verbose;
 	cmd.list.csv_sep = daemon->csv_sep ? *daemon->csv_sep : 0;
 
@@ -1432,6 +1434,7 @@ static int __cmd_signal(struct daemon *daemon, struct option parent_options[],
 		return -1;
 	}
 
+	memset(&cmd, 0, sizeof(cmd));
 	cmd.signal.cmd = CMD_SIGNAL,
 	cmd.signal.sig = SIGUSR2;
 	strncpy(cmd.signal.name, name, sizeof(cmd.signal.name) - 1);
@@ -1446,7 +1449,7 @@ static int __cmd_stop(struct daemon *daemon, struct option parent_options[],
 		OPT_PARENT(parent_options),
 		OPT_END()
 	};
-	union cmd cmd = { .cmd = CMD_STOP, };
+	union cmd cmd;
 
 	argc = parse_options(argc, argv, start_options, daemon_usage, 0);
 	if (argc)
@@ -1457,6 +1460,8 @@ static int __cmd_stop(struct daemon *daemon, struct option parent_options[],
 		return -1;
 	}
 
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.cmd = CMD_STOP;
 	return send_cmd(daemon, &cmd);
 }
 
@@ -1470,7 +1475,7 @@ static int __cmd_ping(struct daemon *daemon, struct option parent_options[],
 		OPT_PARENT(parent_options),
 		OPT_END()
 	};
-	union cmd cmd = { .cmd = CMD_PING, };
+	union cmd cmd;
 
 	argc = parse_options(argc, argv, ping_options, daemon_usage, 0);
 	if (argc)
@@ -1481,6 +1486,8 @@ static int __cmd_ping(struct daemon *daemon, struct option parent_options[],
 		return -1;
 	}
 
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.cmd = CMD_PING;
 	scnprintf(cmd.ping.name, sizeof(cmd.ping.name), "%s", name);
 	return send_cmd(daemon, &cmd);
 }