MdePkg/Library/BaseLib/Ia32/CpuId.c

   1 /** @file
   2   AsmCpuid function.
   3
   4   Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 /**
  10   Retrieves CPUID information.
  11
  12   Executes the CPUID instruction with EAX set to the value specified by Index.
  13   This function always returns Index.
  14   If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
  15   If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
  16   If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
  17   If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
  18   This function is only available on IA-32 and x64.
  19
  20   @param  Index         The 32-bit value to load into EAX prior to invoking the CPUID
  21                         instruction.
  22   @param  RegisterEax   A pointer to the 32-bit EAX value returned by the CPUID
  23                         instruction. This is an optional parameter that may be NULL.
  24   @param  RegisterEbx   A pointer to the 32-bit EBX value returned by the CPUID
  25                         instruction. This is an optional parameter that may be NULL.
  26   @param  RegisterEcx   A pointer to the 32-bit ECX value returned by the CPUID
  27                         instruction. This is an optional parameter that may be NULL.
  28   @param  RegisterEdx   A pointer to the 32-bit EDX value returned by the CPUID
  29                         instruction. This is an optional parameter that may be NULL.
  30
  31   @return Index.
  32
  33 **/
  34 UINT32
  35 EFIAPI
  36 AsmCpuid (
  37   IN      UINT32                    Index,
  38   OUT     UINT32                    *RegisterEax,  OPTIONAL
  39   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  40   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  41   OUT     UINT32                    *RegisterEdx   OPTIONAL
  42   )
  43 {
  44   _asm {
  45     mov     eax, Index
  46     cpuid
  47     push    ecx
  48     mov     ecx, RegisterEax
  49     jecxz   SkipEax
  50     mov     [ecx], eax
  51 SkipEax:
  52     mov     ecx, RegisterEbx
  53     jecxz   SkipEbx
  54     mov     [ecx], ebx
  55 SkipEbx:
  56     pop     eax
  57     mov     ecx, RegisterEcx
  58     jecxz   SkipEcx
  59     mov     [ecx], eax
  60 SkipEcx:
  61     mov     ecx, RegisterEdx
  62     jecxz   SkipEdx
  63     mov     [ecx], edx
  64 SkipEdx:
  65     mov     eax, Index
  66   }
  67 }
  68