SYSCALL
Usage: SYSCALL Modifies flags: None
Fast call to privilege level 0 system procedures.
Call Operating System
SYSCALL ; 0F 05 [P6,AMD]
SYSCALL provides a fast method of transferring control to a fixed entry point in an operating system.
The EIP register is copied into the ECX register.
Bits [31-0] of the 64-bit SYSCALL/SYSRET Target Address Register(STAR) are copied into the EIP register.
Bits [47-32] of the STAR register specify the selector that is copied into the CS register.
Bits [47-32]+1000b of the STAR register specify the selector that is copied into the SS register.
The CS and SS registers should not be modified by the operating system between the execution of the SYSCALL instruction and its corresponding SYSRET instruction.
For more information, see the SYSCALL and SYSRET Instruction Specification (AMD document number 21086.pdf).
EXAMPLE:
syscall