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40 lines
1.0 KiB
NASM
40 lines
1.0 KiB
NASM
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;------------------------------------------------------------------------------
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;
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; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;
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; Module Name:
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;
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; WriteDr4.Asm
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;
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; Abstract:
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;
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; AsmWriteDr4 function
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;
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; Notes:
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;
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;------------------------------------------------------------------------------
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SECTION .text
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;------------------------------------------------------------------------------
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; UINTN
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; EFIAPI
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; AsmWriteDr4 (
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; IN UINTN Value
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; );
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;------------------------------------------------------------------------------
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global ASM_PFX(AsmWriteDr4)
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ASM_PFX(AsmWriteDr4):
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mov eax, [esp + 4]
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;
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; DR4 is alias to DR6 only if DE (in CR4) is cleared. Otherwise, writing to
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; this register will cause a #UD exception.
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;
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; MS assembler doesn't support this instruction since no one would use it
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; under normal circustances. Here opcode is used.
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;
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DB 0xf, 0x23, 0xe0
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ret
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