iAPX 286 Operating System Writers Guide 1983

USING HARDWARE PROTECTION FEATURES~ - EXECUTABLE SEGMENT[!:J -GATEINTRASEGMENTINTERSEGMENTVIA GATEINTERSEGMENT121960-8Figure 2-7. Intralevel Control TransfersPrivilege Rules for Gated Intersegment TransfersAn intersegment transfer through a gate involves four privilege level fields:• The current privilege level (CPL) of the currently executing segment• The requested privilege level (RPL) in the selector used in the CALL• The DPL in the gate descriptor• The DPL in the segment descriptor of the target executable segmentA transfer is valid only if the following relationships among privilege level numbers both hold:MAX (CPL, RPL)