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      1 ;------------------------------------------------------------------------------
      2 ;
      3 ; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
      4 ; This program and the accompanying materials
      5 ; are licensed and made available under the terms and conditions of the BSD License
      6 ; which accompanies this distribution.  The full text of the license may be found at
      7 ; http://opensource.org/licenses/bsd-license.php.
      8 ;
      9 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
     10 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
     11 ;
     12 ; Module Name:
     13 ;
     14 ;   ReadDr5.Asm
     15 ;
     16 ; Abstract:
     17 ;
     18 ;   AsmReadDr5 function
     19 ;
     20 ; Notes:
     21 ;
     22 ;------------------------------------------------------------------------------
     23 
     24     .586p
     25     .model  flat,C
     26     .code
     27 
     28 ;------------------------------------------------------------------------------
     29 ; UINTN
     30 ; EFIAPI
     31 ; AsmReadDr5 (
     32 ;   VOID
     33 ;   );
     34 ;------------------------------------------------------------------------------
     35 AsmReadDr5  PROC
     36     ;
     37     ; DR5 is alias to DR7 only if DE (in CR4) is cleared. Otherwise, reading
     38     ; this register will cause a #UD exception.
     39     ;
     40     ; MS assembler doesn't support this instruction since no one would use it
     41     ; under normal circustances. Here opcode is used.
     42     ;
     43     DB      0fh, 21h, 0e8h
     44     ret
     45 AsmReadDr5  ENDP
     46 
     47     END
     48