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3-474 Vol. 2A INT n/INTO/INT 3—Call to Interrupt Procedure
INSTRUCTION SET REFERENCE, A-M
CS ← IDT(Descriptor (vector_number ∗ 4), selector));
EIP ← IDT(Descriptor (vector_number ∗ 4), offset)); (* 16 bit offset AND 0000FFFFH *)
END;
PROTECTED-MODE:
IF ((vector_number ∗ 8) + 7) is not within IDT limits
or selected IDT descriptor is not an interrupt-, trap-, or task-gate type
THEN #GP((vector_number ∗ 8) + 2 + EXT); FI;
(* EXT is bit 0 in error code *)
IF software interrupt (* Generated by INT n, INT 3, or INTO *)
THEN
IF gate descriptor DPL < CPL
THEN #GP((vector_number ∗ 8) + 2 ); FI;
(* PE
= 1, DPL<CPL, software interrupt *)
FI;
IF gate not present
THEN #NP((vector_number ∗ 8) + 2 + EXT); FI;
IF task gate (* Specified in the selected interrupt table descriptor *)
THEN GOTO TASK-GATE;
ELSE GOTO TRAP-OR-INTERRUPT-GATE; (* PE = 1, trap/interrupt gate *)
FI;
END;
IA-32e-MODE:
IF ((vector_number ∗ 16) + 15) is not in IDT limits
or selected IDT descriptor is not an interrupt-, or trap-gate type
THEN #GP((vector_number ∗ 16) + 2 + EXT); FI;
(* EXT is bit 0 in error code *)
IF software interrupt (* Generated by INT n, INT 3, but not INTO *)
THEN
IF gate descriptor DPL < CPL
THEN #GP((vector_number ∗ 16) + 2 ); FI;
(* PE
= 1, DPL < CPL, software interrupt *)
ELSE (* Generated by INTO *)
THEN #UD;
FI;
IF gate not present
THEN #NP((vector_number ∗ 16) + 2 + EXT); FI;
IF ((vector_number * 16)[IST]
≠ 0)
NewRSP ← TSS[ISTx]; FI;
GOTO TRAP-OR-INTERRUPT-GATE; (* Trap/interrupt gate *)
END;
TASK-GATE: (* PE
= 1, task gate *)
Read segment selector in task gate (IDT descriptor);
IF local/global bit is set to local