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;   ReadDr4.Asm
15;
16; Abstract:
17;
18;   AsmReadDr4 function
19;
20; Notes:
21;
22;------------------------------------------------------------------------------
23
24    .586p
25    .model  flat,C
26    .code
27
28;------------------------------------------------------------------------------
29; UINTN
30; EFIAPI
31; AsmReadDr4 (
32;   VOID
33;   );
34;------------------------------------------------------------------------------
35AsmReadDr4  PROC
36    ;
37    ; DR4 is alias to DR6 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, 0e0h
44    ret
45AsmReadDr4  ENDP
46
47    END
48