For x86 processors, the modes are Sim_CPU_Mode_User for CPL 3, and Sim_CPU_Mode_Supervisor for CPL 0-2.
For other processors, the modes are Sim_CPU_Mode_User or Sim_CPU_Mode_Supervisor. Some processors also has the Sim_CPU_Mode_Hypervisor mode.
void (*)(lang_void *callback_data, conf_object_t *trigger_obj, int64 old_mode, int64 new_mode);