CloverBootloader/MdePkg/Library/BaseLib/Ia32/ReadDr5.nasm
2019-09-03 12:58:42 +03:00

39 lines
989 B
NASM

;------------------------------------------------------------------------------
;
; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
;
; ReadDr5.Asm
;
; Abstract:
;
; AsmReadDr5 function
;
; Notes:
;
;------------------------------------------------------------------------------
SECTION .text
;------------------------------------------------------------------------------
; UINTN
; EFIAPI
; AsmReadDr5 (
; VOID
; );
;------------------------------------------------------------------------------
global ASM_PFX(AsmReadDr5)
ASM_PFX(AsmReadDr5):
;
; DR5 is alias to DR7 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, 0xe8
ret