Specifications

Intel
®
64 and IA-32 Architectures Software Developer’s Manual Documentation Changes 196
Documentation Changes
SS.BASE ← 0; (* Flat segment *)
SS.LIMIT ← FFFFFH; (* 4-GByte limit *)
SS.ARbyte.G ← 1; (* 4-KByte granularity *)
SS.ARbyte.S ←;
SS.ARbyte.TYPE ← 0011B; (* Read/Write, Accessed *)
SS.ARbyte.D ← 1; (* 32-bit stack segment*)
SS.ARbyte.DPL ← 0;
SS.SEL.RPL ← 0;
SS.ARbyte.P ← 1;
ESP ← SYSENTER_ESP_MSR;
EIP ← SYSENTER_EIP_MSR;
...
SYSEXIT—Fast Return from Fast System Call
Instruction Operand Encoding
...
SYSRET—Return From Fast System Call
Instruction Operand Encoding
...
Opcode Instruction Op/
En
64-Bit
Mode
Compat/
Leg Mode
Description
0F 35 SYSEXIT A Valid Valid Fast return to privilege level
3 user code.
REX.W + 0F 35 SYSEXIT A Valid Valid Fast return to 64-bit mode
privilege level 3 user code.
Op/En Operand 1 Operand 2 Operand 3 Operand 4
ANA NA NA NA
Opcode Instruction Op/
En
64-Bit
Mode
Compat/
Leg Mode
Description
0F 07 SYSRET A Valid Invalid Return from fast system call
Op/En Operand 1 Operand 2 Operand 3 Operand 4
ANA NA NA NA