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/** @file
AsmCpuid function.
Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
/**
Retrieves CPUID information.
Executes the CPUID instruction with EAX set to the value specified by Index.
This function always returns Index.
If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
This function is only available on IA-32 and x64.
@param Index The 32-bit value to load into EAX prior to invoking the CPUID
instruction.
@param RegisterEax A pointer to the 32-bit EAX value returned by the CPUID
instruction. This is an optional parameter that may be NULL.
@param RegisterEbx A pointer to the 32-bit EBX value returned by the CPUID
instruction. This is an optional parameter that may be NULL.
@param RegisterEcx A pointer to the 32-bit ECX value returned by the CPUID
instruction. This is an optional parameter that may be NULL.
@param RegisterEdx A pointer to the 32-bit EDX value returned by the CPUID
instruction. This is an optional parameter that may be NULL.
@return Index.
**/
UINT32
EFIAPI
AsmCpuid (
IN UINT32 Index,
OUT UINT32 *RegisterEax OPTIONAL,
OUT UINT32 *RegisterEbx OPTIONAL,
OUT UINT32 *RegisterEcx OPTIONAL,
OUT UINT32 *RegisterEdx OPTIONAL
)
{
_asm {
mov eax, Index
cpuid
push ecx
mov ecx, RegisterEax
jecxz SkipEax
mov [ecx], eax
SkipEax:
mov ecx, RegisterEbx
jecxz SkipEbx
mov [ecx], ebx
SkipEbx:
pop eax
mov ecx, RegisterEcx
jecxz SkipEcx
mov [ecx], eax
SkipEcx:
mov ecx, RegisterEdx
jecxz SkipEdx
mov [ecx], edx
SkipEdx:
mov eax, Index
}
}
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