A method of controlling access to an address translation data structure of a computer system. The computer system includes a processor having a normal execution mode and a secure execution mode. The method includes executing code and generating a linear address. During translation of the linear address into a physical address, the method also includes generating a read-only page fault exception during the normal execution mode in response to detecting a software invoked write access to an address translation data structure having a read/write attribute set to be read-only. The method further includes selectively generating either the read-only page fault exception or a security exception during the secure execution mode in response to detecting the software invoked write access.