1. An apparatus providing for a secure execution environment, comprising: a microprocessor, configured to execute non-secure application programs and a secure application program, wherein said non-secure application programs are accessed from a system memory via a system bus, said microprocessor comprising: secure execution mode logic, configured to detect execution of a secure execution mode return event, and configured to terminate a secure execution mode within said microprocessor, wherein said secure execution mode exclusively supports execution of said secure application program; and a secure non-volatile memory, coupled to said microprocessor via a private bus, configured to store said secure application program prior to termination of said secure execution mode, wherein transactions over said private bus between said microprocessor and said secure non-volatile memory are isolated from said system bus and corresponding system bus resources within said microprocessor.