Importance

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Abstract

A subsystem call mechanism for communicating between a first execution environment associated with a first domain object, and a second execution environment associated with a second domain object. An environment table object is associated with a process object. The environment table object includes a control stack which is an array of control stack entries which entries save the state of the first calling execution environment to be restored on a return from the second execution environment. A subsystem entry in the subsystem table specifies the object that defines region 2 of the target execution environment and the frame pointer of the topmost stack frame in the target environment, a supervisor Stack Pointer that is a linear address for the supervisor stack used when involving a supervisor call in the user mode (instead of the stack pointer in the current frame) to locate the new frame. The first domain object further includes Procedure Entries that specify the type and address of the target procedure. Each of the procedure entries includes a Procedure Entry Type field that indicates the type of procedure to be invoked, either a supervisor procedure or a subsystem procedure, and an offset into the target execution environment. The offset specifies the first instruction of the target procedure.

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First Claim