iAPX 286 Operating System Writers Guide 1983

interSIGNALS AND INTERRUPTSlOTGOTTSSINTERRUPT10TASK GATEnTSSDESCRIPTORnFigure 6-1. Interrupt Vectoring for Tasks121960·304lOTEXECUTABLESEGMENTINTERRUPT10-TRAP GATE ORINTERRUPT GATEUI--LOT OR GOTOFFSETENTRY POINT~SEGMENTDESCRIPTORBASEFigure 6-2. Interrupt Vectoring for Procedures121960·302Note that if an interrupt occurs while a privilege-level D (PL-D) procedure is executing, an attempt totransfer to a less privileged level violates protection rules. (The same protection rules apply as for aCALL to a less privileged segment.) In general it is impossible to predict when an interrupt occurs;therefore, it is equally impossible to avoid a protection violation when a less privileged procedure hasan interrupt gate or trap gate in the IDT.6-3 121960·001