Comparing hash values computed at function entry and exit for increased security

In response to encountering a function entry instruction while running an application, a processor computes an entry hash value using a hash of three hash input parameters, wherein one of the input parameters is a secret key stored in the special purpose register. In response to encountering a function exit instruction, the processor computes an exit hash value using the same three input parameters and the same hash used when computing the entry hash value. The processor determines if the entry hash value is the same as the exit hash value. In response to the entry hash value being the same as the exit hash value the processor exits the function and in response to the entry hash value not being the same as the exit hash value the processor executes a trap interrupt.