[PATCH 03/29] tools lib traceevent: Add plugin support

Jiri Olsa
2013-11-28T11:34:05Z

Backporting plugin support for traceevent lib.

Backported from Steven Rostedt's trace-cmd repo (HEAD 0f2c2fb):
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git

It's now possible to use following interface to load plugins
(shared objects) to enhance pevent object functionality.

The plugin interface/hooks are as follows:
(taken from event-parse.h comments)

- 'pevent_plugin_loader' (required)
The function name to initialized the plugin.

int pevent_plugin_loader(struct pevent *pevent)

- 'pevent_plugin_unloader' (optional)
The function called just before unloading

int pevent_plugin_unloader(void)

- 'pevent_plugin_options' (optional)
Plugin options that can be set before loading

struct plugin_option pevent_plugin_options[] = {
{
.name = "option-name",
.plugin_alias = "overide-file-name", (optional)
.description = "description of option to show users",
},
{
.name = NULL,
},
};

Array must end with .name = NULL;

The plugin_alias (below) can be used to give a shorter
name to access the variable. Useful if a plugin handles
more than one event.

NOTE options support is not backported yet.

- 'pevent_plugin_alias' (optional)
The name to use for finding options (uses filename if not defined)

New traceevent functions are added to search and load
available plugins:

struct plugin_list*
traceevent_load_plugins(struct pevent *pevent)
- loads plusing for 'struct pevent' object and returns
loaded plugins list

void traceevent_unload_plugins(struct plugin_list *plugin_list);
- unload plugin list

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: David Ahern <dsahern@gmail.com>
---
tools/lib/traceevent/Makefile | 6 +-
tools/lib/traceevent/event-parse.h | 5 +
tools/lib/traceevent/event-plugin.c | 202 ++++++++++++++++++++++++++++++++++++
3 files changed, 212 insertions(+), 1 deletion(-)
create mode 100644 tools/lib/traceevent/event-plugin.c

diff --git a/tools/lib/traceevent/Makefile b/tools/lib/traceevent/Makefile
index fc15020..2ccb5bc 100644
--- a/tools/lib/traceevent/Makefile
+++ b/tools/lib/traceevent/Makefile
@@ -180,7 +180,11 @@ $(obj)/%.o: $(src)/%.c
%.o: $(src)/%.c
$(Q)$(call do_compile)

-PEVENT_LIB_OBJS = event-parse.o trace-seq.o parse-filter.o parse-utils.o
+PEVENT_LIB_OBJS = event-parse.o
+PEVENT_LIB_OBJS += event-plugin.o
+PEVENT_LIB_OBJS += trace-seq.o
+PEVENT_LIB_OBJS += parse-filter.o
+PEVENT_LIB_OBJS += parse-utils.o
PEVENT_LIB_OBJS += kbuffer-parse.o

ALL_OBJS = $(PEVENT_LIB_OBJS)
diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index 8d73d25..a288860 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -377,6 +377,11 @@ enum pevent_errno {
};
#undef _PE

+struct plugin_list;
+
+struct plugin_list *traceevent_load_plugins(struct pevent *pevent);
+void traceevent_unload_plugins(struct plugin_list *plugin_list);
+
struct cmdline;
struct cmdline_list;
struct func_map;
diff --git a/tools/lib/traceevent/event-plugin.c b/tools/lib/traceevent/event-plugin.c
new file mode 100644
index 0000000..d272d87
--- /dev/null
+++ b/tools/lib/traceevent/event-plugin.c
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License (not later!)
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <string.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <dirent.h>
+#include "event-parse.h"
+#include "event-utils.h"
+
+#define LOCAL_PLUGIN_DIR ".traceevent/plugins"
+
+struct plugin_list {
+ struct plugin_list *next;
+ char *name;
+ void *handle;
+};
+
+static void
+load_plugin(struct pevent *pevent, const char *path,
+ const char *file, void *data)
+{
+ struct plugin_list **plugin_list = data;
+ pevent_plugin_load_func func;
+ struct plugin_list *list;
+ const char *alias;
+ char *plugin;
+ void *handle;
+
+ plugin = malloc_or_die(strlen(path) + strlen(file) + 2);
+
+ strcpy(plugin, path);
+ strcat(plugin, "/");
+ strcat(plugin, file);
+
+ handle = dlopen(plugin, RTLD_NOW | RTLD_GLOBAL);
+ if (!handle) {
+ warning("could not load plugin '%s'\n%s\n",
+ plugin, dlerror());
+ goto out_free;
+ }
+
+ alias = dlsym(handle, PEVENT_PLUGIN_ALIAS_NAME);
+ if (!alias)
+ alias = file;
+
+ func = dlsym(handle, PEVENT_PLUGIN_LOADER_NAME);
+ if (!func) {
+ warning("could not find func '%s' in plugin '%s'\n%s\n",
+ PEVENT_PLUGIN_LOADER_NAME, plugin, dlerror());
+ goto out_free;
+ }
+
+ list = malloc_or_die(sizeof(*list));
+ list->next = *plugin_list;
+ list->handle = handle;
+ list->name = plugin;
+ *plugin_list = list;
+
+ pr_stat("registering plugin: %s", plugin);
+ func(pevent);
+ return;
+
+ out_free:
+ free(plugin);
+}
+
+static void
+load_plugins_dir(struct pevent *pevent, const char *suffix,
+ const char *path,
+ void (*load_plugin)(struct pevent *pevent,
+ const char *path,
+ const char *name,
+ void *data),
+ void *data)
+{
+ struct dirent *dent;
+ struct stat st;
+ DIR *dir;
+ int ret;
+
+ ret = stat(path, &st);
+ if (ret < 0)
+ return;
+
+ if (!S_ISDIR(st.st_mode))
+ return;
+
+ dir = opendir(path);
+ if (!dir)
+ return;
+
+ while ((dent = readdir(dir))) {
+ const char *name = dent->d_name;
+
+ if (strcmp(name, ".") == 0 ||
+ strcmp(name, "..") == 0)
+ continue;
+
+ /* Only load plugins that end in suffix */
+ if (strcmp(name + (strlen(name) - strlen(suffix)), suffix) != 0)
+ continue;
+
+ load_plugin(pevent, path, name, data);
+ }
+
+ closedir(dir);
+}
+
+static void
+load_plugins(struct pevent *pevent, const char *suffix,
+ void (*load_plugin)(struct pevent *pevent,
+ const char *path,
+ const char *name,
+ void *data),
+ void *data)
+{
+ char *home;
+ char *path;
+ char *envdir;
+
+ /*
+ * If a system plugin directory was defined,
+ * check that first.
+ */
+#ifdef PLUGIN_DIR
+ load_plugins_dir(pevent, suffix, PLUGIN_DIR, load_plugin, data);
+#endif
+
+ /*
+ * Next let the environment-set plugin directory
+ * override the system defaults.
+ */
+ envdir = getenv("TRACEEVENT_PLUGIN_DIR");
+ if (envdir)
+ load_plugins_dir(pevent, suffix, envdir, load_plugin, data);
+
+ /*
+ * Now let the home directory override the environment
+ * or system defaults.
+ */
+ home = getenv("HOME");
+ if (!home)
+ return;
+
+ path = malloc_or_die(strlen(home) + strlen(LOCAL_PLUGIN_DIR) + 2);
+
+ strcpy(path, home);
+ strcat(path, "/");
+ strcat(path, LOCAL_PLUGIN_DIR);
+
+ load_plugins_dir(pevent, suffix, path, load_plugin, data);
+
+ free(path);
+}
+
+struct plugin_list*
+traceevent_load_plugins(struct pevent *pevent)
+{
+ struct plugin_list *list = NULL;
+
+ load_plugins(pevent, ".so", load_plugin, &list);
+ return list;
+}
+
+void
+traceevent_unload_plugins(struct plugin_list *plugin_list)
+{
+ pevent_plugin_unload_func func;
+ struct plugin_list *list;
+
+ while (plugin_list) {
+ list = plugin_list;
+ plugin_list = list->next;
+ func = dlsym(list->handle, PEVENT_PLUGIN_UNLOADER_NAME);
+ if (func)
+ func();
+ dlclose(list->handle);
+ free(list->name);
+ free(list);
+ }
+}
--
1.8.3.1