Memory matching key capability

A non-transitory computer-readable data storage medium storing program code executable by a hardware device to:

• receive an execution protection key (EPK) of a matching key capability (MaKC) of a memory block associated with a memory level of a hierarchy of memory levels at which the memory block actually exists;
• retrieve a block protection key (BPK) of the MaKC of the memory block;
• compare the EPK against the BPK to determine whether the EPK matches the BPK;
• and
• in response to the EPK matching the BPK, permit access to the memory block in accordance with permissions of the MaKC of the memory block,
• wherein:
• each memory level has a plurality of memory addresses, the memory addresses of each memory level except for a lowest memory level mapping to the memory addresses of an immediately lower memory level,
• the hardware device resides at a given memory level within the hierarchy of memory levels, wherein the MaKC of the memory block is a master MaKC, and wherein the program code is executable by the hardware device to further:
• create a secondary MaKC of a memory region overlapping the memory block;
• and
• accord the secondary MaKC with permissions no greater than the permissions of the memory block MaKC of the memory block,
• wherein any hardware device at any memory level of the hierarchy of memory levels in which the memory block is addressed has access to the secondary MaKC, including revocation and modification of the secondary MaKC, upon creation of the secondary MaKC of the memory region.