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page ,132
title VM ASSEMBLY LANGUAGE ROUTINES
;****************************************************************************
;*
;* Copyright (c) 2006, 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 05/09/12 Initial creation of file.
;
;****************************************************************************
;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
; This code provides low level routines that support the Virtual Machine
; for option ROMs.
;* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
;---------------------------------------------------------------------------
; Equate files needed.
;---------------------------------------------------------------------------
text SEGMENT
;---------------------------------------------------------------------------
;;GenericPostSegment SEGMENT USE16
;---------------------------------------------------------------------------
;****************************************************************************
; EbcLLCALLEX
;
; This function is called to execute an EBC CALLEX instruction.
; This instruction requires that we thunk out to external native
; code. For x64, we switch stacks, copy the arguments to the stack
; 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)
CopyMem PROTO Destination:PTR DWORD, Source:PTR DWORD, Count:DWORD
EbcLLCALLEXNative PROC NEAR PUBLIC
push rbp
push rbx
mov rbp, rsp
; Function prolog
; Copy FuncAddr to a preserved register.
mov rbx, rcx
; Set stack pointer to new value
sub r8, rdx
sub rsp, r8
mov rcx, rsp
sub rsp, 20h
call CopyMem
add rsp, 20h
; Considering the worst case, load 4 potiential arguments
; into registers.
mov rcx, qword ptr [rsp]
mov rdx, qword ptr [rsp+8h]
mov r8, qword ptr [rsp+10h]
mov r9, qword ptr [rsp+18h]
; Now call the external routine
call rbx
; Function epilog
mov rsp, rbp
pop rbx
pop rbp
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 rax, rsp ; get current stack pointer
; Stack adjusted by this much when we were called,
; For this function, it's 4.
add rax, 4
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
text ENDS
END
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