[PATCH v4 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 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 ++
 include/traceevent/event-parse.h |  3 +++
 lib/trace-cmd/trace-input.c      |  7 +----
 lib/trace-cmd/trace-util.c       | 46 ++++++++++++++++++++++++++++++++
 lib/traceevent/event-plugin.c    | 38 ++++++++++++++++++++++++++
 tracecmd/trace-check-events.c    |  7 +----
 tracecmd/trace-list.c            | 14 ++--------
 7 files changed, 93 insertions(+), 24 deletions(-)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index 092bd89..0593463 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -25,6 +25,8 @@ 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_tep_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/include/traceevent/event-parse.h b/include/traceevent/event-parse.h
index 99da5ef..b97a366 100644
--- a/include/traceevent/event-parse.h
+++ b/include/traceevent/event-parse.h
@@ -380,6 +380,9 @@ struct tep_plugin_list;
 #define INVALID_PLUGIN_LIST_OPTION	((char **)((unsigned long)-1))
 
 struct tep_plugin_list *tep_load_plugins(struct tep_handle *tep);
+struct tep_plugin_list *tep_load_plugins_dir(struct tep_handle *tep, char *path);
+void tep_plugins_append(struct tep_plugin_list *list1,
+			struct tep_plugin_list *list2);
 void tep_unload_plugins(struct tep_plugin_list *plugin_list,
 			struct tep_handle *tep);
 void tep_load_plugins_hook(struct tep_handle *tep, const char *suffix,
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 8cceb31..6e1fa2e 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2850,15 +2850,10 @@ 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_tep_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 b08e377..5a84fc3 100644
--- a/lib/trace-cmd/trace-util.c
+++ b/lib/trace-cmd/trace-util.c
@@ -884,6 +884,52 @@ 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_tep_plugins(struct tep_handle *tep)
+{
+	struct tep_plugin_list *list_dev;
+	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);
+
+	list = tep_load_plugins(tep);
+
+	path = get_source_plugins_dir();
+	if (path) {
+		list_dev = tep_load_plugins_dir(tep, path);
+		tep_plugins_append(list_dev, list);
+		list = list_dev;
+		free(path);
+	}
+
+	return list;
+}
+
 char *tracecmd_get_tracing_file(const char *name)
 {
 	static const char *tracing;
diff --git a/lib/traceevent/event-plugin.c b/lib/traceevent/event-plugin.c
index bc10205..b2a30bb 100644
--- a/lib/traceevent/event-plugin.c
+++ b/lib/traceevent/event-plugin.c
@@ -599,6 +599,44 @@ tep_load_plugins(struct tep_handle *tep)
 	return list;
 }
 
+/**
+ * tep_load_plugins_dir - load traceevent plugins from a directory
+ * @tep: Trace event handler.
+ * @path: Path to a directory. All files with extension .so in that
+ *	  directory will be loaded as plugins.
+ *
+ * Returns a list of loaded plugins
+ */
+struct tep_plugin_list*
+tep_load_plugins_dir(struct tep_handle *tep, char *path)
+{
+	struct tep_plugin_list *list = NULL;
+
+	if (tep && tep->flags & TEP_DISABLE_PLUGINS)
+		return NULL;
+
+	load_plugins_dir(tep, ".so", path, load_plugin, &list);
+	return list;
+}
+
+/**
+ * tep_plugins_append - Concatenate two plugin lists.
+ * @list1: The first plugin list.
+ * @list2: The second plugin list.
+ *
+ * The second plugin list (list2) is appended to the first one (list1).
+ */
+void tep_plugins_append(struct tep_plugin_list *list1,
+			struct tep_plugin_list *list2)
+{
+	struct tep_plugin_list *list = list1;
+
+	while (list && list->next)
+		list = list->next;
+	if (list)
+		list->next = list2;
+}
+
 void
 tep_unload_plugins(struct tep_plugin_list *plugin_list, struct tep_handle *tep)
 {
diff --git a/tracecmd/trace-check-events.c b/tracecmd/trace-check-events.c
index b09fcd0..eb840c6 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_tep_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..840eeac 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_tep_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_tep_plugins(pevent);
 	tep_print_plugins(&s, "  ", "\n", list);
 
 	trace_seq_do_printf(&s);
-- 
2.21.0