tools lib traceevent: Add interface for options to plugins

Add tep_plugin_add_option() and tep_plugin_print_options() to lib
traceevent library that allows plugins to have their own options. For
example, the function plugin by default does not print the parent, as it
uses the parent to do the indenting. The "parent" option is created by
the function plugin that will print the parent of the function like it
does in the trace file.

The tep_plugin_print_options() will print out the list of options that a
Cc: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
plugin has defined.

Link: http://lore.kernel.org/linux-trace-devel/20190802110101.14759-3-tz.stoyanov@gmail.com
Link: http://lore.kernel.org/linux-trace-devel/20200625100516.365338-5-tz.stoyanov@gmail.comSigned-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200702185704.092654084@goodmis.orgSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.h

@@ -406,7 +406,9 @@ char **tep_plugin_list_options(void);
 void tep_plugin_free_options_list(char **list);
 int tep_plugin_add_options(const char *name,
 			   struct tep_plugin_option *options);
+int tep_plugin_add_option(const char *name, const char *val);
 void tep_plugin_remove_options(struct tep_plugin_option *options);
+void tep_plugin_print_options(struct trace_seq *s);
 void tep_print_plugins(struct trace_seq *s,
 			const char *prefix, const char *suffix,
 			const struct tep_plugin_list *list);

tools/lib/traceevent/event-plugin.c

@@ -13,6 +13,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <dirent.h>
+#include <errno.h>
 #include "event-parse.h"
 #include "event-parse-local.h"
 #include "event-utils.h"
@@ -247,6 +248,166 @@ void tep_plugin_remove_options(struct tep_plugin_option *options)
 	}
 }
 
+static void parse_option_name(char **option, char **plugin)
+{
+	char *p;
+
+	*plugin = NULL;
+
+	if ((p = strstr(*option, ":"))) {
+		*plugin = *option;
+		*p = '\0';
+		*option = strdup(p + 1);
+		if (!*option)
+			return;
+	}
+}
+
+static struct tep_plugin_option *
+find_registered_option(const char *plugin, const char *option)
+{
+	struct registered_plugin_options *reg;
+	struct tep_plugin_option *op;
+	const char *op_plugin;
+
+	for (reg = registered_options; reg; reg = reg->next) {
+		for (op = reg->options; op->name; op++) {
+			if (op->plugin_alias)
+				op_plugin = op->plugin_alias;
+			else
+				op_plugin = op->file;
+
+			if (plugin && strcmp(plugin, op_plugin) != 0)
+				continue;
+			if (strcmp(option, op->name) != 0)
+				continue;
+
+			return op;
+		}
+	}
+
+	return NULL;
+}
+
+static int process_option(const char *plugin, const char *option, const char *val)
+{
+	struct tep_plugin_option *op;
+
+	op = find_registered_option(plugin, option);
+	if (!op)
+		return 0;
+
+	return update_option_value(op, val);
+}
+
+/**
+ * tep_plugin_add_option - add an option/val pair to set plugin options
+ * @name: The name of the option (format: <plugin>:<option> or just <option>)
+ * @val: (optiona) the value for the option
+ *
+ * Modify a plugin option. If @val is given than the value of the option
+ * is set (note, some options just take a boolean, so @val must be either
+ * "1" or "0" or "true" or "false").
+ */
+int tep_plugin_add_option(const char *name, const char *val)
+{
+	struct trace_plugin_options *op;
+	char *option_str;
+	char *plugin;
+
+	option_str = strdup(name);
+	if (!option_str)
+		return -ENOMEM;
+
+	parse_option_name(&option_str, &plugin);
+
+	/* If the option exists, update the val */
+	for (op = trace_plugin_options; op; op = op->next) {
+		/* Both must be NULL or not NULL */
+		if ((!plugin || !op->plugin) && plugin != op->plugin)
+			continue;
+		if (plugin && strcmp(plugin, op->plugin) != 0)
+			continue;
+		if (strcmp(op->option, option_str) != 0)
+			continue;
+
+		/* update option */
+		free(op->value);
+		if (val) {
+			op->value = strdup(val);
+			if (!op->value)
+				goto out_free;
+		} else
+			op->value = NULL;
+
+		/* plugin and option_str don't get freed at the end */
+		free(plugin);
+		free(option_str);
+
+		plugin = op->plugin;
+		option_str = op->option;
+		break;
+	}
+
+	/* If not found, create */
+	if (!op) {
+		op = malloc(sizeof(*op));
+		if (!op)
+			return -ENOMEM;
+		memset(op, 0, sizeof(*op));
+		op->next = trace_plugin_options;
+		trace_plugin_options = op;
+
+		op->plugin = plugin;
+		op->option = option_str;
+
+		if (val) {
+			op->value = strdup(val);
+			if (!op->value)
+				goto out_free;
+		}
+	}
+
+	return process_option(plugin, option_str, val);
+ out_free:
+	free(option_str);
+	return -ENOMEM;
+}
+
+static void print_op_data(struct trace_seq *s, const char *name,
+			  const char *op)
+{
+	if (op)
+		trace_seq_printf(s, "%8s:\t%s\n", name, op);
+}
+
+/**
+ * tep_plugin_print_options - print out the registered plugin options
+ * @s: The trace_seq descriptor to write the plugin options into
+ *
+ * Writes a list of options into trace_seq @s.
+ */
+void tep_plugin_print_options(struct trace_seq *s)
+{
+	struct registered_plugin_options *reg;
+	struct tep_plugin_option *op;
+
+	for (reg = registered_options; reg; reg = reg->next) {
+		if (reg != registered_options)
+			trace_seq_printf(s, "============\n");
+		for (op = reg->options; op->name; op++) {
+			if (op != reg->options)
+				trace_seq_printf(s, "------------\n");
+			print_op_data(s, "file", op->file);
+			print_op_data(s, "plugin", op->plugin_alias);
+			print_op_data(s, "option", op->name);
+			print_op_data(s, "desc", op->description);
+			print_op_data(s, "value", op->value);
+			trace_seq_printf(s, "%8s:\t%d\n", "set", op->set);
+		}
+	}
+}
+
 /**
  * tep_print_plugins - print out the list of plugins loaded
  * @s: the trace_seq descripter to write to
@@ -273,6 +434,7 @@ load_plugin(struct tep_handle *tep, const char *path,
 	    const char *file, void *data)
 {
 	struct tep_plugin_list **plugin_list = data;
+	struct tep_plugin_option *options;
 	tep_plugin_load_func func;
 	struct tep_plugin_list *list;
 	const char *alias;
@@ -297,6 +459,16 @@ load_plugin(struct tep_handle *tep, const char *path,
 	if (!alias)
 		alias = file;
 
+	options = dlsym(handle, TEP_PLUGIN_OPTIONS_NAME);
+	if (options) {
+		while (options->name) {
+			ret = update_option(alias, options);
+			if (ret < 0)
+				goto out_free;
+			options++;
+		}
+	}
+
 	func = dlsym(handle, TEP_PLUGIN_LOADER_NAME);
 	if (!func) {
 		warning("could not find func '%s' in plugin '%s'\n%s\n",