       RSP ← IA32_SYSENTER_ESP;
         RIP ← IA32_SYSENTER_EIP;
ELSE
         ESP ← IA32_SYSENTER_ESP[31:0];
         EIP ← IA32_SYSENTER_EIP[31:0];
FI;
CS.Selector ← IA32_SYSENTER_CS[15:0] AND FFFCH;
                                                    (* Operating system provides CS; RPL forced to 0 *)
(* Set rest of CS to a fixed value *)
CS.Base ← 0;
                                                    (* Flat segment *)
CS.Limit ← FFFFFH;
                                                  