| 摘要 |
<p>STORAGE FETCH PROTECT OVERRIDE CONTROLS This invention relates to the fetch protection of a critical area in the main storage (MS) of a data processing system. The critical area is smaller than, and contained within, the size of a main storage block protectable by a single storage protect key having a fetch protection field. This invention extends protect key operations for system/370 extended architectures that use 4KB pages. This invention recognizes that system integrity is enhanced by providing different types of fetch protection within the PSA page which cannot be done with the associated 4KB key. To enable different fetch protections within a special 4KB block, this invention provides fetch protect override controls to partly override the normal operation of the 4KB storage key for a page located at a predetermined real address in MS. While 4KB fetch protection is set on for the special page's 4KB block, the fetch protect override controls disable fetch protection for a portion of the special page's real addresses (e.g. addresses 0-2047). Override enablement is controlled by a fetch protect override control bit in a control register (e.g. bit 6 of control register 0).</p> |
