[PATCH v6 2/3] trace-cmd: Load libtraceevent plugins from build folder, if exists.

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

When a development version of trace-cmd is built and run on the machine,
by default it loads only installed plugins, from system directories.
Thus, the development plugins will not be loaded. To simplify the development
process, a new logic is added:
  At plugins load time, check the location of trace-cmd application and look
  for "plugins" directory around it. If found, load plugins from it. Those
  plugins will be loaded last, so in case of duplication the "development"
  plugins win.
A two new APIs are introduced to libtraceevent, in order to accomplish this
logic:
 tep_load_plugins_dir() - loads tep plugins from a specific directory.
 tep_plugins_append() - Append two plugin lists.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/trace-cmd/trace-cmd.h |  2 ++
 lib/trace-cmd/trace-input.c   |  7 +-----
 lib/trace-cmd/trace-util.c    | 42 +++++++++++++++++++++++++++++++++++
 tracecmd/trace-check-events.c |  7 +-----
 tracecmd/trace-list.c         | 14 ++----------
 5 files changed, 48 insertions(+), 24 deletions(-)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index 4090eba..d1aaef8 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -24,6 +24,8 @@ void tracecmd_parse_ftrace_printk(struct tep_handle *pevent, char *file, unsigne
 extern int tracecmd_disable_sys_plugins;
 extern int tracecmd_disable_plugins;
 
+struct tep_plugin_list *trace_load_plugins(struct tep_handle *tep);
+
 char **tracecmd_event_systems(const char *tracing_dir);
 char **tracecmd_system_events(const char *tracing_dir, const char *system);
 struct tep_handle *tracecmd_local_events(const char *tracing_dir);
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 6102eb3..28da455 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2886,15 +2886,10 @@ struct tracecmd_input *tracecmd_alloc_fd(int fd)
 	if (!handle->pevent)
 		goto failed_read;
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(handle->pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(handle->pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	/* register default ftrace functions first */
 	tracecmd_ftrace_overrides(handle, &handle->finfo);
 
-	handle->plugin_list = tep_load_plugins(handle->pevent);
+	handle->plugin_list = trace_load_plugins(handle->pevent);
 
 	tep_set_file_bigendian(handle->pevent, buf[0]);
 	tep_set_local_bigendian(handle->pevent, tracecmd_host_bigendian());
diff --git a/lib/trace-cmd/trace-util.c b/lib/trace-cmd/trace-util.c
index 8aa3b6c..690a135 100644
--- a/lib/trace-cmd/trace-util.c
+++ b/lib/trace-cmd/trace-util.c
@@ -860,6 +860,48 @@ void trace_util_free_plugin_files(char **files)
 	free(files);
 }
 
+static char *get_source_plugins_dir(void)
+{
+	char *p, path[PATH_MAX+1];
+	int ret;
+
+	ret = readlink("/proc/self/exe", path, PATH_MAX);
+	if (ret > PATH_MAX || ret < 0)
+		return NULL;
+
+	dirname(path);
+	p = strrchr(path, '/');
+	if (!p)
+		return NULL;
+	/* Check if we are in the the source tree */
+	if (strcmp(p, "/tracecmd") != 0)
+		return NULL;
+
+	strcpy(p, "/lib/traceevent/plugins");
+	return strdup(path);
+}
+
+struct tep_plugin_list*
+trace_load_plugins(struct tep_handle *tep)
+{
+	struct tep_plugin_list *list;
+	char *path;
+
+	if (tracecmd_disable_plugins)
+		tep_set_flag(tep, TEP_DISABLE_PLUGINS);
+	if (tracecmd_disable_sys_plugins)
+		tep_set_flag(tep, TEP_DISABLE_SYS_PLUGINS);
+
+	path = get_source_plugins_dir();
+	if (path)
+		tep_add_plugin_path(tep, path, TEP_PLUGIN_LAST);
+	free(path);
+
+	list = tep_load_plugins(tep);
+
+	return list;
+}
+
 char *tracecmd_get_tracing_file(const char *name)
 {
 	static const char *tracing;
diff --git a/tracecmd/trace-check-events.c b/tracecmd/trace-check-events.c
index b09fcd0..ffaae27 100644
--- a/tracecmd/trace-check-events.c
+++ b/tracecmd/trace-check-events.c
@@ -43,12 +43,7 @@ void trace_check_events(int argc, char **argv)
 	if (!pevent)
 		exit(EINVAL);
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
-	list = tep_load_plugins(pevent);
+	list = trace_load_plugins(pevent);
 	ret = tracecmd_fill_local_events(tracing, pevent, &parsing_failures);
 	if (ret || parsing_failures)
 		ret = EINVAL;
diff --git a/tracecmd/trace-list.c b/tracecmd/trace-list.c
index 65099a5..6b59117 100644
--- a/tracecmd/trace-list.c
+++ b/tracecmd/trace-list.c
@@ -317,14 +317,9 @@ static void show_plugin_options(void)
 	if (!pevent)
 		die("Can not allocate pevent\n");
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	trace_seq_init(&s);
 
-	list = tep_load_plugins(pevent);
+	list = trace_load_plugins(pevent);
 	tep_plugin_print_options(&s);
 	trace_seq_do_printf(&s);
 	tep_unload_plugins(list, pevent);
@@ -348,14 +343,9 @@ static void show_plugins(void)
 	if (!pevent)
 		die("Can not allocate pevent\n");
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	trace_seq_init(&s);
 
-	list = tep_load_plugins(pevent);
+	list = trace_load_plugins(pevent);
 	tep_print_plugins(&s, "  ", "\n", list);
 
 	trace_seq_do_printf(&s);
-- 
2.21.0