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[mirror_edk2.git] / MdeModulePkg / Universal / EbcDxe / X64 / EbcLowLevel.asm

;/** @file\r
;  \r
;    This code provides low level routines that support the Virtual Machine.\r
;    for option ROMs.\r
;  \r
;  Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>\r
;  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
;**/\r
\r
  page    ,132\r
  title   VM ASSEMBLY LANGUAGE ROUTINES\r
\r
;---------------------------------------------------------------------------\r
; Equate files needed.\r
;---------------------------------------------------------------------------\r
\r
text SEGMENT\r
\r
;---------------------------------------------------------------------------\r
;;GenericPostSegment      SEGMENT USE16\r
;---------------------------------------------------------------------------\r
\r
;****************************************************************************\r
; EbcLLCALLEX\r
;\r
; This function is called to execute an EBC CALLEX instruction.\r
; This instruction requires that we thunk out to external native\r
; code. For x64, we switch stacks, copy the arguments to the stack\r
; and jump to the specified function.\r
; On return, we restore the stack pointer to its original location.\r
;\r
; Destroys no working registers.\r
;****************************************************************************\r
; VOID EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)\r
\r
CopyMem  PROTO  Destination:PTR DWORD, Source:PTR DWORD, Count:DWORD\r
\r
\r
EbcLLCALLEXNative        PROC    PUBLIC\r
      push   rbp\r
      push   rbx\r
      mov    rbp, rsp\r
      ; Function prolog\r
\r
      ; Copy FuncAddr to a preserved register.\r
      mov    rbx, rcx\r
\r
      ; Set stack pointer to new value\r
      sub    r8,  rdx\r
      sub    rsp, r8\r
      mov    rcx, rsp\r
      sub    rsp, 20h\r
      call   CopyMem\r
      add    rsp, 20h\r
\r
      ; Considering the worst case, load 4 potiential arguments\r
      ; into registers.\r
      mov    rcx, qword ptr [rsp]\r
      mov    rdx, qword ptr [rsp+8h]\r
      mov    r8,  qword ptr [rsp+10h]\r
      mov    r9,  qword ptr [rsp+18h]\r
\r
      ; Now call the external routine\r
      call  rbx\r
\r
      ; Function epilog\r
      mov      rsp, rbp\r
      pop      rbx\r
      pop      rbp\r
      ret\r
EbcLLCALLEXNative    ENDP\r
\r
\r
; UINTN EbcLLGetEbcEntryPoint(VOID);\r
; Routine Description:\r
;   The VM thunk code stuffs an EBC entry point into a processor\r
;   register. Since we can't use inline assembly to get it from\r
;   the interpreter C code, stuff it into the return value\r
;   register and return.\r
;\r
; Arguments:\r
;     None.\r
;\r
; Returns:\r
;     The contents of the register in which the entry point is passed.\r
;\r
EbcLLGetEbcEntryPoint        PROC    PUBLIC\r
    mov  rax, r10\r
    ret\r
EbcLLGetEbcEntryPoint    ENDP\r
\r
;/*++\r
;\r
;Routine Description:\r
;\r
;  Return the caller's value of the stack pointer.\r
;\r
;Arguments:\r
;\r
;  None.\r
;\r
;Returns:\r
;\r
;  The current value of the stack pointer for the caller. We\r
;  adjust it by 4 here because when they called us, the return address\r
;  is put on the stack, thereby lowering it by 4 bytes.\r
;\r
;--*/\r
\r
; UINTN EbcLLGetStackPointer()\r
EbcLLGetStackPointer        PROC    PUBLIC\r
    mov    rax, rsp      ; get current stack pointer\r
    ; Stack adjusted by this much when we were called,\r
    ; For this function, it's 4.\r
    add   rax, 4\r
    ret\r
EbcLLGetStackPointer    ENDP\r
\r
; UINT64 EbcLLGetReturnValue(VOID);\r
; Routine Description:\r
;   When EBC calls native, on return the VM has to stuff the return\r
;   value into a VM register. It's assumed here that the value is still\r
;    in the register, so simply return and the caller should get the\r
;   return result properly.\r
;\r
; Arguments:\r
;     None.\r
;\r
; Returns:\r
;     The unmodified value returned by the native code.\r
;\r
EbcLLGetReturnValue   PROC    PUBLIC\r
    ret\r
EbcLLGetReturnValue    ENDP\r
\r
text  ENDS\r
END\r
\r