1. Add comments about reserve space on space according to x64 calling convention

[mirror_edk2.git] / MdePkg / Library / BaseLib / X64 / SwitchStack.asm

;------------------------------------------------------------------------------\r
;\r
; Copyright (c) 2006 - 2008, Intel Corporation\r
; All rights reserved. This program and the accompanying materials\r
; are licensed and made available under the terms and conditions of the BSD License\r
; which accompanies this distribution.  The full text of the license may be found at\r
; http://opensource.org/licenses/bsd-license.php\r
;\r
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
;\r
; Module Name:\r
;\r
;   SwitchStack.Asm\r
;\r
; Abstract:\r
;\r
;------------------------------------------------------------------------------\r
\r
    .code\r
\r
;------------------------------------------------------------------------------\r
; Routine Description:\r
;\r
;   Routine for switching stacks with 2 parameters\r
;\r
; Arguments:\r
;\r
;   (rcx) EntryPoint    - Entry point with new stack.\r
;   (rdx) Context1      - Parameter1 for entry point.\r
;   (r8)  Context2      - Parameter2 for entry point.\r
;   (r9)  NewStack      - Pointer to new stack.\r
;\r
; Returns:\r
;\r
;   None\r
;\r
;------------------------------------------------------------------------------\r
InternalSwitchStack PROC\r
    mov     rax, rcx\r
    mov     rcx, rdx\r
    mov     rdx, r8\r
    ;\r
    ; Reserve space for register parameters (rcx, rdx, r8 & r9) on the stack,\r
    ; in case the callee wishes to spill them.\r
    ;\r
    lea     rsp, [r9 - 20h]\r
    call    rax\r
InternalSwitchStack ENDP\r
\r
    END\r