Synchronous communication between execution environments in a data processing system employing an object-oriented memory protection mechanism

Claim 1

In a data processing system including a memory space and a processor register space in a processor of said data processing system, said processor register space including means for storing object descriptors having base and length information stored therein for use in locating objects in said memory space, means in said processor for communicating with said memory space; and, means in said processor for executing an operation by means of an operator specified in an instruction; the improvement comprising in combination: first means in said processor for communicating between a current (calling) execution environment stored in said memory space and a target (called) execution environment stored in said memory space, second means in said processor, connected to said first means, for storing first objects defining said current (calling) execution environment, said current execution environment being accessible by means of a first domain object, third means in said processor, connected to said first means, for storing in said memory second objects defining said target (called) execution environment, said target execution environment being accessible by means of a second domain object; fourth means in said processor for creating a first environment table object, said first environment table object being accessible by means of said first domain object; said environment table object including a control stack for containing subsystem linkage information, said control stack being an array of control stack entries, which entries represent a state of said current (calling) execution environment to be restored on a return from said target (called) execution environment which is a target of a subsystem call; fifth means in said processor for storing in said second domain object a Region 0 access descriptor (AD) that reference a Region 0 object which defines region 0 of said target (called) execution environment which is a target of a subsystem call; sixth means in said processor for storing in said second domain object a Region 1 AD that references a Region 1 object which defines region 1 of said target (called) execution environment which is the target of a subsystem call; seventh means in said processor for storing in said second domain object a subsystem ID that points to an entry in a subsystem table in said first environment table object, a subsystem entry in said subsystem table specifying a Region 2 object that defines region 2 of said target (called) execution environment and a frame pointer of a topmost stack frame in said target (called) execution environment, a supervisor Stack Pointer that is a linear address (in words) for a supervisor stack used when invoking a supervisor call in a user mode (instead of the stack pointer in the current frame) to locate a new frame; eighth means in said processor for storing, in said second domain object, Procedure Entries that specify a type and an address of said target (called) environment, each of said procedure entries including a Procedure Entry Type field that indicates a type of procedure to be invoked including, but not limited to, a supervisor procedure and a subsystem procedure, and an Offset into said target (called) execution environment, which offset specifies a first instruction of said target (called) execution environment; and, ninth means in said processor, connected to said fourth means and to said seventh means, for utilizing said subsystem ID in said second domain object to find, in said subsystem table in said first environment table object, a subsystem entry containing a new region 2 access descriptor, and a top most frame pointer and a topmost stack pointer of a new stack.