perf trace: Allow configuring if zeroed syscall args should be printed

The default so far, since we show argument names followed by its values,
was to make the output more compact by suppressing most zeroed args.

Make this configurable so that users can choose what best suit their
needs.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-q0gxws02ygodh94o0hzim5xd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index d754a74..4d97bda 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -127,6 +127,7 @@
 	bool			show_tool_stats;
 	bool			trace_syscalls;
 	bool			kernel_syscallchains;
+	bool			show_zeros;
 	bool			force;
 	bool			vfs_getname;
 	int			trace_pgfaults;
@@ -1598,6 +1599,7 @@
  			 * strarray for it.
  			 */
 			if (val == 0 &&
+			    !trace->show_zeros &&
 			    !(sc->arg_fmt &&
 			      (sc->arg_fmt[arg.idx].show_zero ||
 			       sc->arg_fmt[arg.idx].scnprintf == SCA_STRARRAY ||
@@ -3526,14 +3528,16 @@
 
 static int trace__config(const char *var, const char *value, void *arg)
 {
+	struct trace *trace = arg;
 	int err = 0;
 
 	if (!strcmp(var, "trace.add_events")) {
-		struct trace *trace = arg;
 		struct option o = OPT_CALLBACK('e', "event", &trace->evlist, "event",
 					       "event selector. use 'perf list' to list available events",
 					       parse_events_option);
 		err = parse_events_option(&o, value, 0);
+	} else if (!strcmp(var, "trace.show_zeros")) {
+		trace->show_zeros = perf_config_bool(var, value);
 	}
 
 	return err;