Object lifetime control in an object-oriented memory protection mechanism

A data processing system including a memory space (10) and a processor register space (11) in a processor of said data processing system for storing object descriptors having base and length information stored therein for use in locating objects in said memory space,

• communicating means in said processor for communicating with said memory space (10);
• executing means in said processor for executing an operation by means of an operator specified in an instruction (14);
• a plurality of addressable objects, including a bipaged object (38), said plurality of addressable objects being stored in an address space of said memory space,
• said plurality of addressable objects including instruction objects comprised of instructions including said instruction (14) defining an operation;
• an address (20) referenced in said instruction (14), said address (20) being specified as an offset (22) and an access descriptor (AD) (24);
• said plurality of objects including an object table (42), a page table directory (60), and a page table (44);
• each of said objects being comprised of words, each of said words being either an access descriptor or a data word;
• each of said access descriptors including
• 1. an object index for selecting an object in said address space,
• 2. a rights field, said rights field specifying permissible operations on an object selected by said access descriptor;
• said data processing system comprising:
• each of said access descriptors including access descriptor (AD) lifetime bit means for indicating a lifetime of an object specified by said access descriptor;
• first means for storing said object table object (42) at an address accessible by said processor upon processor initialization,
• second means for storing in said object table object table entry (OTE) object descriptors for use by said processor in forming physical addresses to said page table directory object (60),
• third means for storing in each of said object descriptors a first encoded field (50) specifying a base address of an object referenced by said object descriptor and a second encoded field (52) which includes page rights;
• said object storage descriptor includes an OTE lifetime bit means for indicating a lifetime of said object selected by said access descriptor;
• fourth means for storing in said page table (44) page table entries for use by said processor in forming physical addresses to said paged object (38),
• fifth means for storing in each page table entry a page rights field (81);
• sixth means for storing in said offset (22) a page index (PI) used to index into a selected page table to locate said page table entry, and a page offset (PO) used in conjunction with a base address (79) stored in said page table entry to locate a datum entry in said paged object (38);
• and,
• means (150) for comparing said AD lifetime bit of said access descriptor with said OTE lifetime bit of said object table entry and for asserting a fault upon the condition that an access permitted by said AD lifetime bit of said access descriptor is inconsistent with said OTE lifetime bit of said object table entry.