Method and system for preventing unauthorized processor mode switches

摘要

A system comprising a processor adapted to activate multiple security levels for the system and a monitoring device coupled to the processor and employing security rules pertaining to the multiple security levels. The monitoring device restricts usage of the system if the processor activates the security levels in a sequence contrary to the security rules.

主权项

1. A system, comprising:
a processor apparatus adapted to activate one of more than two operating modes for the system, each mode having an assigned security level wherein the security levels are partitioned into secure and non-secure modes with an intermediate mode between the secure and non-secure modes and wherein the system switches between the secure and non-secure modes by adjusting a single bit stored in the processor apparatus, said bit adjusted only in the intermediate mode; and a monitoring device coupled to the processor apparatus and employing security rules pertaining to the more than two operating modes, wherein the monitoring device restricts usage of the system if the processor apparatus switches to a secure operating mode from a non-secure operating mode or to a non-secure operating mode from a secure operating mode without first switching to the intermediate mode.