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https://github.com/CloverHackyColor/CloverBootloader.git
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49 lines
1.5 KiB
NASM
49 lines
1.5 KiB
NASM
;------------------------------------------------------------------------------
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; @file
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; Copyright (C) 2020, vit9696. All rights reserved.
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;
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; All rights reserved.
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;
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; This program and the accompanying materials
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; are licensed and made available under the terms and conditions of the BSD License
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; which accompanies this distribution. The full text of the license may be found at
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; http://opensource.org/licenses/bsd-license.php
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;
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; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;------------------------------------------------------------------------------
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BITS 64
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DEFAULT REL
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MSR_IA32_BIOS_SIGN_ID equ 00000008Bh
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CPUID_VERSION_INFO equ 1
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SECTION .text
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;------------------------------------------------------------------------------
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; UINT32
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; EFIAPI
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; AsmReadIntelMicrocodeRevision (
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; VOID
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; );
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;------------------------------------------------------------------------------
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align 8
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global ASM_PFX(AsmReadIntelMicrocodeRevision)
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ASM_PFX(AsmReadIntelMicrocodeRevision):
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; Several Intel CPUs, notably Westmere, require a certain assembly
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; sequence to retrieve microcode revision.
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; Reference: https://github.com/acidanthera/bugtracker/issues/621.
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push rbx
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mov ecx, MSR_IA32_BIOS_SIGN_ID
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xor eax, eax
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xor edx, edx
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wrmsr
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mov eax, CPUID_VERSION_INFO
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cpuid
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mov ecx, MSR_IA32_BIOS_SIGN_ID
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rdmsr
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mov eax, edx
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pop rbx
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ret
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