EdkModulePkg/Universal/Ebc/Dxe/Ia32/EbcLowLevel.asm

   1   page    ,132
   2   title   VM ASSEMBLY LANGUAGE ROUTINES
   3 ;****************************************************************************
   4 ;*
   5 ;*  Copyright (c) 2006, Intel Corporation
   6 ;*  All rights reserved. This program and the accompanying materials
   7 ;*  are licensed and made available under the terms and conditions of the BSD License
   8 ;*  which accompanies this distribution.  The full text of the license may be found at
   9 ;*  http://opensource.org/licenses/bsd-license.php
  10 ;*
  11 ;*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12 ;*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13 ;*
  14 ;****************************************************************************
  15 ;****************************************************************************
  16 ;                                   REV 1.0
  17 ;****************************************************************************
  18 ;
  19 ; Rev  Date      Description
  20 ; ---  --------  ------------------------------------------------------------
  21 ; 1.0  03/14/01  Initial creation of file.
  22 ;
  23 ;****************************************************************************
  24
  25 ;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
  26 ; This code provides low level routines that support the Virtual Machine
  27 ; for option ROMs.
  28 ;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
  29
  30 ;---------------------------------------------------------------------------
  31 ; Equate files needed.
  32 ;---------------------------------------------------------------------------
  33
  34 .XLIST
  35
  36 .LIST
  37
  38 ;---------------------------------------------------------------------------
  39 ; Assembler options
  40 ;---------------------------------------------------------------------------
  41
  42 .686p
  43 .model  flat
  44 .code
  45 ;---------------------------------------------------------------------------
  46 ;;GenericPostSegment      SEGMENT USE16
  47 ;---------------------------------------------------------------------------
  48
  49 ;****************************************************************************
  50 ; EbcLLCALLEXNative
  51 ;
  52 ; This function is called to execute an EBC CALLEX instruction
  53 ; to native code.
  54 ; This instruction requires that we thunk out to external native
  55 ; code. For IA32, we simply switch stacks and jump to the
  56 ; specified function. On return, we restore the stack pointer
  57 ; to its original location.
  58 ;
  59 ; Destroys no working registers.
  60 ;****************************************************************************
  61 ; VOID EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)
  62 _EbcLLCALLEXNative        PROC    NEAR    PUBLIC
  63       push   ebp
  64       mov    ebp, esp              ; standard function prolog
  65
  66       ; Get function address in a register
  67       ; mov ecx, FuncAddr => mov ecx, dword ptr [FuncAddr]
  68       mov    ecx, dword ptr [esp]+8
  69
  70       ; Set stack pointer to new value
  71       ; mov eax, NewStackPointer => mov eax, dword ptr [NewSp]
  72       mov    eax, dword ptr [esp] + 0Ch
  73       mov    esp, eax
  74
  75       ; Now call the external routine
  76       call  ecx
  77
  78       ; ebp is preserved by the callee. In this function it
  79       ; equals the original esp, so set them equal
  80       mov    esp, ebp
  81
  82       ; Standard function epilog
  83       mov      esp, ebp
  84       pop      ebp
  85       ret
  86 _EbcLLCALLEXNative    ENDP
  87
  88
  89 ; UINTN EbcLLGetEbcEntryPoint(VOID);
  90 ; Routine Description:
  91 ;   The VM thunk code stuffs an EBC entry point into a processor
  92 ;   register. Since we can't use inline assembly to get it from
  93 ;   the interpreter C code, stuff it into the return value
  94 ;   register and return.
  95 ;
  96 ; Arguments:
  97 ;     None.
  98 ;
  99 ; Returns:
 100 ;     The contents of the register in which the entry point is passed.
 101 ;
 102 _EbcLLGetEbcEntryPoint        PROC    NEAR    PUBLIC
 103     ret
 104 _EbcLLGetEbcEntryPoint    ENDP
 105
 106 ;/*++
 107 ;
 108 ;Routine Description:
 109 ;
 110 ;  Return the caller's value of the stack pointer.
 111 ;
 112 ;Arguments:
 113 ;
 114 ;  None.
 115 ;
 116 ;Returns:
 117 ;
 118 ;  The current value of the stack pointer for the caller. We
 119 ;  adjust it by 4 here because when they called us, the return address
 120 ;  is put on the stack, thereby lowering it by 4 bytes.
 121 ;
 122 ;--*/
 123
 124 ; UINTN EbcLLGetStackPointer()
 125 _EbcLLGetStackPointer        PROC    NEAR    PUBLIC
 126     mov    eax, esp      ; get current stack pointer
 127     add   eax, 4        ; stack adjusted by this much when we were called
 128     ret
 129 _EbcLLGetStackPointer    ENDP
 130
 131 ; UINT64 EbcLLGetReturnValue(VOID);
 132 ; Routine Description:
 133 ;   When EBC calls native, on return the VM has to stuff the return
 134 ;   value into a VM register. It's assumed here that the value is still
 135 ;    in the register, so simply return and the caller should get the
 136 ;   return result properly.
 137 ;
 138 ; Arguments:
 139 ;     None.
 140 ;
 141 ; Returns:
 142 ;     The unmodified value returned by the native code.
 143 ;
 144 _EbcLLGetReturnValue   PROC    NEAR    PUBLIC
 145     ret
 146 _EbcLLGetReturnValue    ENDP
 147
 148 END