[mce] Add valgrind mode to ease memory leak debugging

Using valgrind to find memory issues from mce can be tricky.

Add --valgrind-mode command line option for running mce in valgrind friendly
manner when needed.

Do not unmap plugins so that valgrind can locate symbol information for them
at exit time.

Flush cached dbus message objects before exiting.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

mce-dbus.c

@@ -4197,5 +4197,11 @@ void mce_dbus_exit(void)
 			dbus_connection = NULL;
 	}
 
+	/* When debugging, tell libdbus to release all dynamic resouces */
+	if( mce_in_valgrind_mode() ) {
+		mce_log(LL_WARN, "dbus shutdown");
+		dbus_shutdown();
+	}
+
 	return;
 }

mce-modules.c

@@ -214,6 +214,24 @@ void mce_modules_exit(void)
 
 	if (modules != NULL) {
 		for (i = 0; (module = g_slist_nth_data(modules, i)) != NULL; i++) {
+			if( mce_in_valgrind_mode() ) {
+				/* Do not actually unmap the plugins so that
+				 * valgrind can still locate the symbols at
+				 * exit time. */
+				gpointer addr = 0;
+				g_module_symbol(module, "g_module_unload", &addr);
+				if( addr ) {
+					mce_log(LL_WARN, "simulating module %s unload",
+						g_module_name(module));
+					void (*unload)(GModule *) = addr;
+					unload(module);
+				}
+				else {
+					mce_log(LL_WARN, "skipping module %s unload",
+						g_module_name(module));
+				}
+				continue;
+			}
 			g_module_close(module);
 		}
 

mce.c

@@ -657,6 +657,7 @@ static struct
 	bool systembus;
 	bool show_module_info;
 	bool systemd_notify;
+	bool valgrind_mode;
 	int  auto_exit;
 } mce_args =
 {
@@ -666,9 +667,15 @@ static struct
 	.systembus        = true,
 	.show_module_info = false,
 	.systemd_notify   = false,
+	.valgrind_mode    = false,
 	.auto_exit        = -1,
 };
 
+bool mce_in_valgrind_mode(void)
+{
+	return mce_args.valgrind_mode;
+}
+
 static bool mce_do_help(const char *arg);
 static bool mce_do_version(const char *arg);
 
@@ -698,6 +705,12 @@ static bool mce_do_auto_exit(const char *arg)
 	mce_args.auto_exit = arg ? strtol(arg, 0, 0) : 5;
 	return true;
 }
+static bool mce_do_valgrind_mode(const char *arg)
+{
+	(void)arg;
+	mce_args.valgrind_mode = true;
+	return true;
+}
 static bool mce_do_log_function(const char *arg)
 {
 	mce_log_add_pattern(arg);
@@ -859,6 +872,12 @@ static const mce_opt_t options[] =
 			"\n"
 			"This is usefult for mce startup debugging only.\n"
 	},
+	{
+		.name        = "valgrind-mode",
+		.without_arg = mce_do_valgrind_mode,
+		.usage       =
+			"Enable run-under valgrind mode\n"
+	},
 	// sentinel
 	{
 		.name = 0

mce.h

@@ -418,6 +418,7 @@ submode_t mce_get_submode_int32(void);
 gboolean mce_add_submode_int32(const submode_t submode);
 gboolean mce_rem_submode_int32(const submode_t submode);
 
+bool mce_in_valgrind_mode(void);
 void mce_abort(void) __attribute__((noreturn));
 void mce_quit_mainloop(void);
 void mce_signal_handlers_remove(void);