[zion] Move to default permissions being supplied by KernelObjects

zion/object/address_space.h

@@ -4,6 +4,7 @@
 #include <glacier/memory/ref_ptr.h>
 #include <stdint.h>
 
+#include "include/ztypes.h"
 #include "memory/user_stack_manager.h"
 #include "object/memory_object.h"
 
@@ -36,6 +37,8 @@ class AddressSpace : public KernelObject {
  public:
   uint64_t TypeTag() override { return KernelObject::ADDRESS_SPACE; }
 
+  static uint64_t DefaultPermissions() { return kZionPerm_Write; }
+
   enum MemoryType {
     UNSPECIFIED,
     UNMAPPED,