SYSEXIT
Usage: SYSEXIT Modifies flags: None
Fast return to privilege level 3 user code.
Fast Return From System Call
SYSEXIT ; 0F 35 [P6,PRIV]
SYSEXIT executes a fast return to privilege level 3 user code. This instruction is a companion instruction to the SYSENTER instruction, and can only be executed by privilege level 0 code. Various registers need to be set up before calling this instruction:
SYSENTER_CS_MSR contains the 32-bit segment selector for the privilege level 0 code segment in which the processor is currently executing. (This value is used to compute the segment selectors for the privilege level 3 code and stack segments.)
EDX contains the 32-bit offset into the privilege level 3 code segment to the first instruction to be executed in the user code.
ECX contains the 32-bit stack pointer for the privilege level 3 stack.
SYSEXIT performs the following sequence of operations:
Adds 16 to the value in SYSENTER_CS_MSR and loads the sum into the CS selector register.
Loads the instruction pointer from the EDX register into the EIP register.
Adds 24 to the value in SYSENTER_CS_MSR and loads the sum into the SS selector register.
Loads the stack pointer from the ECX register into the ESP register.
Switches to privilege level 3.
Begins executing the user code at the EIP address.
For more information on the use of the SYSENTER and SYSEXIT instructions, see the Intel Architecture Software Developer's Manual, Volume 2.
EXAMPLE:
sysexit