sync comments, fix function header, rename variable name to follow coding style.

[mirror_edk2.git] / MdeModulePkg / Universal / EbcDxe / Ia32 / 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. <BR>\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
;**/\r
\r
  page    ,132\r
  title   VM ASSEMBLY LANGUAGE ROUTINES\r
\r
;---------------------------------------------------------------------------\r
; Equate files needed.\r
;---------------------------------------------------------------------------\r
\r
.XLIST\r
\r
.LIST\r
\r
;---------------------------------------------------------------------------\r
; Assembler options\r
;---------------------------------------------------------------------------\r
\r
.686p\r
.model  flat\r
.code\r
;---------------------------------------------------------------------------\r
;;GenericPostSegment      SEGMENT USE16\r
;---------------------------------------------------------------------------\r
CopyMem  PROTO  C Destination:PTR DWORD, Source:PTR DWORD, Count:DWORD\r
\r
;****************************************************************************\r
; EbcLLCALLEXNative\r
;\r
; This function is called to execute an EBC CALLEX instruction\r
; to native code.\r
; This instruction requires that we thunk out to external native\r
; code. For IA32, we simply switch stacks and jump to the\r
; specified function. On return, we restore the stack pointer\r
; to its original location.\r
;\r
; Destroys no working registers.\r
;****************************************************************************\r
; VOID EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)\r
_EbcLLCALLEXNative        PROC    NEAR    PUBLIC\r
      push   ebp\r
      push   ebx\r
      mov    ebp, esp              ; standard function prolog\r
\r
      ; Get function address in a register\r
      ; mov ecx, FuncAddr => mov ecx, dword ptr [FuncAddr]\r
      mov    ecx, dword ptr [esp]+0Ch\r
\r
      ; Set stack pointer to new value\r
      ; mov eax, NewStackPointer => mov eax, dword ptr [NewSp]\r
      mov    eax, dword ptr [esp] + 14h\r
      mov    edx, dword ptr [esp] + 10h\r
      sub    eax, edx\r
      sub    esp, eax\r
      mov    ebx, esp\r
      push   ecx\r
      push   eax\r
      push   edx\r
      push   ebx\r
      call   CopyMem\r
      pop    eax\r
      pop    eax\r
      pop    eax\r
      pop    ecx\r
\r
      ; Now call the external routine\r
      call  ecx\r
\r
      ; ebp is preserved by the callee. In this function it\r
      ; equals the original esp, so set them equal\r
      mov    esp, ebp\r
\r
      ; Standard function epilog\r
      mov      esp, ebp\r
      pop      ebx\r
      pop      ebp\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    NEAR    PUBLIC\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    NEAR    PUBLIC\r
    mov    eax, esp      ; get current stack pointer\r
    add   eax, 4        ; stack adjusted by this much when we were called\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    NEAR    PUBLIC\r
    ret\r
_EbcLLGetReturnValue    ENDP\r
\r
END\r