A DATA PROCESSING APPARATUS AND METHOD FOR PROTECTING SECURE DATA AND PROGRAM CODE FROM NON-SECURE ACCESS WHEN SWITCHING BETWEEN SECURE AND LESS SECURE DOMAINS

摘要

A data processing apparatus includes processing circuitry and a data store including a plurality of regions including a secure region and a less secure region. The secure region is configured to store sensitive data accessible by the circuitry when operating in a secure domain and not accessible by the circuitry when operating in a less secure domain. The data store includes a plurality of stacks with a secure stack in the secure region. Stack access circuitry is configured to store predetermined processing state to the secure stack. The processing circuitry further comprises fault checking circuitry configured to identify a first fault condition if the data stored in the predetermined relative location is the first value. This provides protection against attacks from the less secure domain, for example performing a function call return from an exception, or an exception return from a function call.