module: check module wasn't already initialized

The virtual-device fuzzer must initialize QOM, prior to running
vl:qemu_init, so that it can use the qos_graph to identify the arguments
required to initialize a guest for libqos-assisted fuzzing. This change
prevents errors when vl:qemu_init tries to (re)initialize the previously
initialized QOM module.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200220041118.23264-4-alxndr@bu.edu
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

util/module.c

@@ -30,6 +30,7 @@ typedef struct ModuleEntry
 typedef QTAILQ_HEAD(, ModuleEntry) ModuleTypeList;
 
 static ModuleTypeList init_type_list[MODULE_INIT_MAX];
+static bool modules_init_done[MODULE_INIT_MAX];
 
 static ModuleTypeList dso_init_list;
 
@@ -91,11 +92,17 @@ void module_call_init(module_init_type type)
     ModuleTypeList *l;
     ModuleEntry *e;
 
+    if (modules_init_done[type]) {
+        return;
+    }
+
     l = find_type(type);
 
     QTAILQ_FOREACH(e, l, node) {
         e->init();
     }
+
+    modules_init_done[type] = true;
 }
 
 #ifdef CONFIG_MODULES