Apparatus and method for managing a microprocessor providing for a secure execution mode

A microprocessor apparatus, for executing secure code within a secure execution environment, the microprocessor apparatus comprising:

• a secure non-volatile memory, configured to store a secure application program;
• and
• a microprocessor, coupled to said secure non-volatile memory via a private bus, configured to execute non-secure application programs and said secure application program, said microprocessor comprising:
• secure execution mode logic, configured to monitor conditions corresponding to said microprocessor that are associated with potential security exposure and tampering, and configured to cause said microprocessor to transition to a degraded operating mode from said secure execution mode following detection of a first one or more of said conditions, wherein said degraded operating mode exclusively provides for execution of BIOS instructions, said BIOS instructions comprising instructions to allow for user input and display of messages.

A method for executing secure code within a secure execution environment, the method comprising:

• providing a secure non-volatile memory for storage of the secure code, wherein the secure code is accessed within the secure non-volatile memory via private transactions accomplished over a private bus that is coupled between the secure non-volatile memory and a microprocessor, and wherein the private bus is isolated from all system bus resources within the microprocessor and external to the microprocessor, and wherein the private bus is observable and accessible exclusively by secure execution logic within the microprocessor;
• monitoring conditions corresponding to the microprocessor that are associated with potential security exposure and tampering;
• and
• first transitioning the microprocessor to a degraded operating mode from the secure execution mode following detection of a first one or more of the conditions, wherein the degraded operating mode exclusively provides for execution of BIOS instructions, the BIOS instructions comprising instructions to allow for user input and display of messages.