EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseLib/Ia32/WriteDr4.asm

   1 ; Copyright (c) 2004, Intel Corporation
   2 ; All rights reserved. This program and the accompanying materials
   3 ; are licensed and made available under the terms and conditions of the BSD License
   4 ; which accompanies this distribution.  The full text of the license may be found at
   5 ; http://opensource.org/licenses/bsd-license.php
   6 ;
   7 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
   8 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
   9 ;
  10 ; Module Name:
  11 ;
  12 ;   WriteDr4.Asm
  13 ;
  14 ; Abstract:
  15 ;
  16 ;   AsmWriteDr4 function
  17 ;
  18 ; Notes:
  19 ;
  20 ;------------------------------------------------------------------------------
  21
  22     .586p
  23     .model  flat,C
  24     .code
  25
  26 ;------------------------------------------------------------------------------
  27 ; UINTN
  28 ; EFIAPI
  29 ; AsmWriteDr4 (
  30 ;   IN UINTN Value
  31 ;   );
  32 ;------------------------------------------------------------------------------
  33 AsmWriteDr4 PROC
  34     mov     eax, [esp + 4]
  35     ;
  36     ; DR4 is alias to DR6 only if DE (in CR4) is cleared. Otherwise, writing to
  37     ; this register will cause a #UD exception.
  38     ;
  39     ; MS assembler doesn't support this instruction since no one would use it
  40     ; under normal circustances. Here opcode is used.
  41     ;
  42     DB      0fh, 23h, 0e0h
  43     ret
  44 AsmWriteDr4 ENDP
  45
  46     END