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Vol. 2A 3-497
INSTRUCTION SET REFERENCE, A-M
IRET/IRETD—Interrupt Return
IF CPL = 0
THEN
EFLAGS(IOPL) ← tempEFLAGS;
IF OperandSize
= 32
THEN EFLAGS(VM, VIF, VIP) ← tempEFLAGS; FI;
IF OperandSize = 64
THEN EFLAGS(VIF, VIP) ← tempEFLAGS; FI;
FI;
CPL ← RPL of the return code segment selector;
FOR each of segment register (ES, FS, GS, and DS)
DO
IF segment register points to data or non-conforming code segment
and CPL > segment descriptor DPL (* Stored in hidden part of segment register *)
THEN (* Segment register invalid *)
SegmentSelector ← 0; (* NULL segment selector *)
FI;
OD;
END;
IA-32e-MODE-RETURN: (* IA32_EFER.LMA = 1, PE
= 1 *)
IF ( (return code segment selector is NULL) or (return RIP is non-canonical) or
(SS selector is NULL going back to compatibility mode) or
(SS selector is NULL going back to CPL3 64-bit mode) or
(RPL <> CPL going back to non-CPL3 64-bit mode for a NULL SS selector) )
THEN GP(0); FI;
IF return code segment selector addresses descriptor beyond descriptor table limit
THEN GP(selector); FI;
Read segment descriptor pointed to by the return code segment selector;
IF return code segment descriptor is not a code segment
THEN #GP(selector); FI;
IF return code segment selector RPL < CPL
THEN #GP(selector); FI;
IF return code segment descriptor is conforming
and return code segment DPL > return code segment selector RPL
THEN #GP(selector); FI;
IF return code segment descriptor is not present
THEN #NP(selector); FI;
IF return code segment selector RPL > CPL
THEN GOTO RETURN-OUTER-PRIVILEGE-LEVEL;
ELSE GOTO RETURN-TO-SAME-PRIVILEGE-LEVEL; FI;
END;