[PATCH v18 10/18] trace-cmd: Store the session tracing ID in the trace.dat file

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

The ID of the current tracing session is stored in the trace.dat file.
A new file option is introduced:
	TRACECMD_OPTION_TRACEID
The data is stored in the file as NULL terminated string:
	"\nTraceID: %llu\n"
A new libtracecmd API is introduced, to get the ID when the trace.dat file is read:
	unsigned long long tracecmd_get_traceid(struct tracecmd_input *handle);

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/trace-cmd/trace-cmd.h |  2 ++
 lib/trace-cmd/trace-input.c   | 25 +++++++++++++++++++++++++
 tracecmd/trace-record.c       | 15 +++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index ad69313..6cc2913 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -86,6 +86,7 @@ enum {
 	TRACECMD_OPTION_CPUCOUNT,
 	TRACECMD_OPTION_VERSION,
 	TRACECMD_OPTION_PROCMAPS,
+	TRACECMD_OPTION_TRACEID,
 };
 
 enum {
@@ -128,6 +129,7 @@ int tracecmd_copy_headers(struct tracecmd_input *handle, int fd);
 void tracecmd_set_flag(struct tracecmd_input *handle, int flag);
 void tracecmd_clear_flag(struct tracecmd_input *handle, int flag);
 unsigned long tracecmd_get_flags(struct tracecmd_input *handle);
+unsigned long long tracecmd_get_traceid(struct tracecmd_input *handle);
 
 void tracecmd_parse_trace_clock(struct tracecmd_input *handle, char *file, int size);
 
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 91362f3..40d9825 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -79,6 +79,7 @@ struct tracecmd_input {
 	struct tep_plugin_list	*plugin_list;
 	struct tracecmd_input	*parent;
 	unsigned long		flags;
+	unsigned long long	trace_id;
 	int			fd;
 	int			long_size;
 	int			page_size;
@@ -2169,6 +2170,15 @@ static void procmap_free(struct pid_addr_maps *maps)
 	free(maps);
 }
 
+static int trace_traceid_load(struct tracecmd_input *handle, char *buf)
+{
+
+	if (sscanf(buf, "%*s %llu", &handle->trace_id) == 1)
+		return 0;
+
+	return -1;
+}
+
 #define STR_PROCMAP_LINE_MAX	(PATH_MAX+22)
 static int trace_pid_map_load(struct tracecmd_input *handle, char *buf)
 {
@@ -2406,6 +2416,10 @@ static int handle_options(struct tracecmd_input *handle)
 			if (buf[size-1] == '\0')
 				trace_pid_map_load(handle, buf);
 			break;
+		case TRACECMD_OPTION_TRACEID:
+			if (buf[size-1] == '\0')
+				trace_traceid_load(handle, buf);
+			break;
 		default:
 			warning("unknown option %d", option);
 			break;
@@ -3507,3 +3521,14 @@ void tracecmd_set_show_data_func(struct tracecmd_input *handle,
 {
 	handle->show_data_func = func;
 }
+
+/**
+ * tracecmd_get_traceid - get the trace id of the session
+ * @handle: input handle for the trace.dat file
+ *
+ * Returns the trace id, written in the trace file
+ */
+unsigned long long tracecmd_get_traceid(struct tracecmd_input *handle)
+{
+	return handle->trace_id;
+}
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 7089f7b..b65aeb2 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -3714,6 +3714,19 @@ add_pid_maps(struct tracecmd_output *handle, struct buffer_instance *instance)
 	trace_seq_destroy(&s);
 }
 
+static void
+add_trace_id(struct tracecmd_output *handle, struct buffer_instance *instance)
+{
+	char *str = NULL;
+	int len;
+
+	len = asprintf(&str, "\nTraceID: %llu\n", instance->trace_id);
+	if (len < 1)
+		return;
+	tracecmd_add_option(handle, TRACECMD_OPTION_TRACEID, len + 1, str);
+	free(str);
+}
+
 static void
 add_buffer_stat(struct tracecmd_output *handle, struct buffer_instance *instance)
 {
@@ -3817,6 +3830,8 @@ static void add_options(struct tracecmd_output *handle, struct common_record_con
 	add_option_hooks(handle);
 	add_uname(handle);
 	add_version(handle);
+	if (!no_top_instance())
+		add_trace_id(handle, &top_instance);
 }
 
 static void write_guest_file(struct buffer_instance *instance)
-- 
2.23.0