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page ,132
title VM ASSEMBLY LANGUAGE ROUTINES
;****************************************************************************
;*
;* Copyright (c) 2006 - 2007, Intel Corporation
;* All rights reserved. This program and the accompanying materials
;* are licensed and made available under the terms and conditions of the BSD License
;* which accompanies this distribution. The full text of the license may be found at
;* http://opensource.org/licenses/bsd-license.php
;*
;* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
;* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;*
;****************************************************************************
;****************************************************************************
; REV 1.0
;****************************************************************************
;
; Rev Date Description
; --- -------- ------------------------------------------------------------
; 1.0 03/14/01 Initial creation of file.
;
;****************************************************************************
;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
; This code provides low level routines that support the Virtual Machine
; for option ROMs.
;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
;---------------------------------------------------------------------------
; Equate files needed.
;---------------------------------------------------------------------------
.XLIST
.LIST
;---------------------------------------------------------------------------
; Assembler options
;---------------------------------------------------------------------------
.686p
.model flat
.code
;---------------------------------------------------------------------------
;;GenericPostSegment SEGMENT USE16
;---------------------------------------------------------------------------
CopyMem PROTO C Destination:PTR DWORD, Source:PTR DWORD, Count:DWORD
;****************************************************************************
; EbcLLCALLEXNative
;
; This function is called to execute an EBC CALLEX instruction
; to native code.
; This instruction requires that we thunk out to external native
; code. For IA32, we simply switch stacks and jump to the
; specified function. On return, we restore the stack pointer
; to its original location.
;
; Destroys no working registers.
;****************************************************************************
; VOID EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)
_EbcLLCALLEXNative PROC NEAR PUBLIC
push ebp
push ebx
mov ebp, esp ; standard function prolog
; Get function address in a register
; mov ecx, FuncAddr => mov ecx, dword ptr [FuncAddr]
mov ecx, dword ptr [esp]+0Ch
; Set stack pointer to new value
; mov eax, NewStackPointer => mov eax, dword ptr [NewSp]
mov eax, dword ptr [esp] + 14h
mov edx, dword ptr [esp] + 10h
sub eax, edx
sub esp, eax
mov ebx, esp
push ecx
push eax
push edx
push ebx
call CopyMem
pop eax
pop eax
pop eax
pop ecx
; Now call the external routine
call ecx
; ebp is preserved by the callee. In this function it
; equals the original esp, so set them equal
mov esp, ebp
; Standard function epilog
mov esp, ebp
pop ebx
pop ebp
ret
_EbcLLCALLEXNative ENDP
; UINTN EbcLLGetEbcEntryPoint(VOID);
; Routine Description:
; The VM thunk code stuffs an EBC entry point into a processor
; register. Since we can't use inline assembly to get it from
; the interpreter C code, stuff it into the return value
; register and return.
;
; Arguments:
; None.
;
; Returns:
; The contents of the register in which the entry point is passed.
;
_EbcLLGetEbcEntryPoint PROC NEAR PUBLIC
ret
_EbcLLGetEbcEntryPoint ENDP
;/*++
;
;Routine Description:
;
; Return the caller's value of the stack pointer.
;
;Arguments:
;
; None.
;
;Returns:
;
; The current value of the stack pointer for the caller. We
; adjust it by 4 here because when they called us, the return address
; is put on the stack, thereby lowering it by 4 bytes.
;
;--*/
; UINTN EbcLLGetStackPointer()
_EbcLLGetStackPointer PROC NEAR PUBLIC
mov eax, esp ; get current stack pointer
add eax, 4 ; stack adjusted by this much when we were called
ret
_EbcLLGetStackPointer ENDP
; UINT64 EbcLLGetReturnValue(VOID);
; Routine Description:
; When EBC calls native, on return the VM has to stuff the return
; value into a VM register. It's assumed here that the value is still
; in the register, so simply return and the caller should get the
; return result properly.
;
; Arguments:
; None.
;
; Returns:
; The unmodified value returned by the native code.
;
_EbcLLGetReturnValue PROC NEAR PUBLIC
ret
_EbcLLGetReturnValue ENDP
END
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