Storing secure mode page table data in secure and non-secure regions of memory

摘要

Apparatus for data processing 2 is provided with processing circuitry 8 which operates in one or more secure modes 40 and one or more non-secure modes 42. When operating in a non-secure mode, one or more regions of the memory are inaccessible. A memory management unit 24 is responsive to page table data to manage accesses to the memory which includes a secure memory 22 and a non-secure memory 6. Secure page table data 36, 38 is used when operating in one of the secure modes. A page table entry within the hierarchy of page tables of the secure page table data includes a table security field 68, 72 indicating whether or not a further page table pointed to by that page table entry is stored within the secure memory 22 or the non-secure memory 6. If any of the page tables associated with a memory access are stored within the non-secure memory 6, then the memory access is marked with a table attribute bit NST indicating that the memory access should be treated as non-secure.