trace-cmd report: Add --cpus option

Add the option --cpus to trace-cmd report to list the CPUs with data in
the trace file and then exit.

Link: https://lore.kernel.org/linux-trace-devel/20220314130955.420df3ef@gandalf.local.home

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

3 files changed, 32 insertions, 0 deletions

diff --git a/Documentation/trace-cmd/trace-cmd-report.1.txt b/Documentation/trace-cmd/trace-cmd-report.1.txt
index 18e1c5cd..aad8ab51 100644
--- a/Documentation/trace-cmd/trace-cmd-report.1.txt
+++ b/Documentation/trace-cmd/trace-cmd-report.1.txt
@@ -251,6 +251,9 @@ OPTIONS
     Example:  "--cpu 0,3" - show events from CPUs 0 and 3
               "--cpu 2-4" - show events from CPUs 2, 3 and 4
 
+*--cpus*::
+    List the CPUs that have data in the trace file then exit.
+
 *--stat*::
     If the trace.dat file recorded the final stats (outputed at the end of record)
     the *--stat* option can be used to retrieve them.
diff --git a/tracecmd/trace-read.c b/tracecmd/trace-read.c
index 24177c44..df559d2a 100644
--- a/tracecmd/trace-read.c
+++ b/tracecmd/trace-read.c
@@ -1542,6 +1542,7 @@ enum {
 	OPT_kallsyms	= 253,
 	OPT_events	= 254,
 	OPT_cpu		= 255,
+	OPT_cpus	= 256,
 };
 
 void trace_report (int argc, char **argv)
@@ -1569,6 +1570,7 @@ void trace_report (int argc, char **argv)
 	int show_uname = 0;
 	int show_version = 0;
 	int show_events = 0;
+	int show_cpus = 0;
 	int print_events = 0;
 	int nanosec = 0;
 	int no_date = 0;
@@ -1595,6 +1597,7 @@ void trace_report (int argc, char **argv)
 		int option_index = 0;
 		static struct option long_options[] = {
 			{"cpu", required_argument, NULL, OPT_cpu},
+			{"cpus", no_argument, NULL, OPT_cpus},
 			{"events", no_argument, NULL, OPT_events},
 			{"event", required_argument, NULL, OPT_event},
 			{"filter-test", no_argument, NULL, 'T'},
@@ -1724,6 +1727,9 @@ void trace_report (int argc, char **argv)
 		case OPT_cpu:
 			parse_cpulist(optarg);
 			break;
+		case OPT_cpus:
+			show_cpus = 1;
+			break;
 		case OPT_events:
 			print_events = 1;
 			break;
@@ -1916,10 +1922,32 @@ void trace_report (int argc, char **argv)
 			return;
 		}
 
+		if (show_cpus) {
+			int cpus;
+			int ret;
+			int i;
+
+			if (!tracecmd_is_buffer_instance(handle)) {
+				ret = tracecmd_init_data(handle);
+				if (ret < 0)
+					die("failed to init data");
+			}
+			cpus = tracecmd_cpus(handle);
+			printf("List of CPUs in %s with data:\n", inputs->file);
+			for (i = 0; i < cpus; i++) {
+				if (tracecmd_read_cpu_first(handle, i))
+					printf("  %d\n", i);
+			}
+			continue;
+		}
+
 		set_event_flags(pevent, nohandler_events, TEP_EVENT_FL_NOHANDLE);
 		set_event_flags(pevent, raw_events, TEP_EVENT_FL_PRINTRAW);
 	}
 
+	if (show_cpus)
+		return;
+
 	otype = OUTPUT_NORMAL;
 
 	if (tracecmd_get_flags(handle) & TRACECMD_FL_RAW_TS) {
diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c
index 5e96ca44..ea7d510d 100644
--- a/tracecmd/trace-usage.c
+++ b/tracecmd/trace-usage.c
@@ -227,6 +227,7 @@ static struct usage_help usage_help[] = {
 		"          -O plugin option -O [plugin:]var[=val]\n"
 		"          --cpu <cpu1,cpu2,...> - filter events according to the given cpu list.\n"
 		"                                  A range of CPUs can be specified using 'cpuX-cpuY' notation.\n"
+		"          --cpus - List the CPUs that have content in it then exit.\n"
 		"          --check-events return whether all event formats can be parsed\n"
 		"          --stat - show the buffer stats that were reported at the end of the record.\n"
 		"          --uname - show uname of the record, if it was saved\n"