Intel 253666-024US - Manual (Page 542)

3-496 Vol. 2A IRET/IRETD—Interrupt Return
INSTRUCTION SET REFERENCE, A-M
EFLAGS(IOPL) ← tempEFLAGS;
IF OperandSize = 32 or OperandSize = 64
THEN EFLAGS(VIF, VIP) ← tempEFLAGS; FI;
FI;
END;
RETURN-TO-OUTER-PRIVILEGE-LEVEL:
IF OperandSize = 32
THEN
IF top 8 bytes on stack are not within limits
THEN #SS(0); FI;
ELSE (* OperandSize = 16 *)
IF top 4 bytes on stack are not within limits
THEN #SS(0); FI;
FI;
Read return segment selector;
IF stack segment selector is NULL
THEN #GP(0); FI;
IF return stack segment selector index is not within its descriptor table limits
THEN #GP(SSselector); FI;
Read segment descriptor pointed to by return segment selector;
IF stack segment selector RPL
≠ RPL of the return code segment selector
or the stack segment descriptor does not indicate a a writable data segment;
or the stack segment DPL
≠ RPL of the return code segment selector
THEN #GP(SS selector); FI;
IF stack segment is not present
THEN #SS(SS selector); FI;
IF new mode ≠ 64-Bit Mode
THEN
IF tempEIP is not within code segment limits
THEN #GP(0); FI;
EIP ← tempEIP;
ELSE (* new mode = 64-bit mode *)
IF tempRIP is non-canonical
THEN #GP(0); FI;
RIP ← tempRIP;
FI;
CS ← tempCS;
EFLAGS (CF, PF, AF, ZF, SF, TF, DF, OF, NT) ← tempEFLAGS;
IF OperandSize = 32
THEN EFLAGS(RF, AC, ID) ← tempEFLAGS; FI;
IF CPL ≤ IOPL
THEN EFLAGS(IF) ← tempEFLAGS; FI;