[PATCH v3 3/5] 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 drierctories.
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
  pluigins will be loaded last, so in case of duplication the "development"
  plugins win.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 lib/traceevent/event-plugin.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/lib/traceevent/event-plugin.c b/lib/traceevent/event-plugin.c
index bc10205..4fc4ee3 100644
--- a/lib/traceevent/event-plugin.c
+++ b/lib/traceevent/event-plugin.c
@@ -14,6 +14,7 @@
 #include <unistd.h>
 #include <dirent.h>
 #include <errno.h>
+#include <libgen.h>
 #include "event-parse.h"
 #include "event-parse-local.h"
 #include "event-utils.h"
@@ -538,6 +539,27 @@ load_plugins_dir(struct tep_handle *tep, const char *suffix,
 	closedir(dir);
 }
 
+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);
+}
+
 void tep_load_plugins_hook(struct tep_handle *tep, const char *suffix,
 			   void (*load_plugin)(struct tep_handle *tep,
 					       const char *path,
@@ -588,6 +610,12 @@ void tep_load_plugins_hook(struct tep_handle *tep, const char *suffix,
 	load_plugins_dir(tep, suffix, path, load_plugin, data);
 
 	free(path);
+
+	path = get_source_plugins_dir();
+	if (path) {
+		load_plugins_dir(tep, suffix, path, load_plugin, data);
+		free(path);
+	}
 }
 
 struct tep_plugin_list*
-- 
2.21.0