Subroutine execution monitoring method, stores subroutine return address in program stack then compares with address given by subroutine return command to determine if error has occurred

摘要

When a subroutine is called (34) a return address (38) is stored in the program stack (30). When a subroutine return command (40) is executed the address in the return command and the address in the stack are compared to determine if they have a predetermined relationship to each other. If not, an error handling routine is called. Independent claims are also included for the following ; (1) processor; (2) chip card with processor.