Security method making deterministic real time execution of multitask applications of control and command type with error confinement

Abstract

The method is implemented with a management system of the time-triggered architecture type in association with a processor of a central processor unit that possesses a privileged execution mode to which access is protected by an instruction of the 'call to system layer' type. The only system layer call that is authorized from an application task under consideration to the system layer consists in reporting a change of node in the control graph of the task in question. When the system layer has verified that the call is legal relative to the execution paths of the control graph as described in the constant tables of the application, all of the operations to be performed on the node in question by the system layer are predetermined by the constant tables of the application associated with the system layer. Prior to real-time execution, pre-ordering of the lists of tasks of an application under consideration is performed in a micro-kernel, which subsequently ensures, when called by the system layer during real-time execution, that task lists are updated in ordered manner depending on the new time characteristics of the tasks, specifically their earliest start times d(i) and their latest finish times f(i) as calculated by the system layer.