Load and store operations are checked against both the page table permissions and the protection key permissions associated with the protection domain of the virtual address, and only allowed if both permissions allow the access.
12.
Since 1989, it has concentrated on computer security, firstly with CopyControl ( a software-based copy protection system ), then Dinkey Dongle ( small hardware copy protection keys that connect to parallel or USB ports ).
13.
The software fault handler can, if desired, check the missing key against a larger list of keys maintained by software; thus, the protection key registers inside the processor may be treated as a software-managed cache of a larger list of keys associated with a process.
