event-plugin.c

/*
 * 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(strlen(path) + strlen(file) + 2);
	if (!plugin) {
		warning("could not allocate plugin memory\n");
		return;
	}

	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(sizeof(*list));
	if (!list) {
		warning("could not allocate plugin memory\n");
		goto out_free;
	}

	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(strlen(home) + strlen(LOCAL_PLUGIN_DIR) + 2);
	if (!path) {
		warning("could not allocate plugin memory\n");
		return;
	}

	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, struct pevent *pevent)
{
	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(pevent);
		dlclose(list->handle);
		free(list->name);
		free(list);
	}
}