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;------------------------------------------------------------------------------
;
; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
;
; ReadDr4.Asm
;
; Abstract:
;
; AsmReadDr4 function
;
; Notes:
;
;------------------------------------------------------------------------------
SECTION .text
;------------------------------------------------------------------------------
; UINTN
; EFIAPI
; AsmReadDr4 (
; VOID
; );
;------------------------------------------------------------------------------
global ASM_PFX(AsmReadDr4)
ASM_PFX(AsmReadDr4):
;
; DR4 is alias to DR6 only if DE (in CR4) is cleared. Otherwise, reading
; this register will cause a #UD exception.
;
; MS assembler doesn't support this instruction since no one would use it
; under normal circustances. Here opcode is used.
;
DB 0xf, 0x21, 0xe0
ret
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