MdePkg/Library/BaseLib/Ia32/CpuId.c

   1 /** @file
   2   AsmCpuid function.
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation<BR>
   5   All rights reserved. This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 /**
  16   Retrieves CPUID information.
  17
  18   Executes the CPUID instruction with EAX set to the value specified by Index.
  19   This function always returns Index.
  20   If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
  21   If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
  22   If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
  23   If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
  24   This function is only available on IA-32 and x64.
  25
  26   @param  Index         The 32-bit value to load into EAX prior to invoking the CPUID
  27                         instruction.
  28   @param  RegisterEax   Pointer to the 32-bit EAX value returned by the CPUID
  29                         instruction. This is an optional parameter that may be NULL.
  30   @param  RegisterEbx   Pointer to the 32-bit EBX value returned by the CPUID
  31                         instruction. This is an optional parameter that may be NULL.
  32   @param  RegisterEcx   Pointer to the 32-bit ECX value returned by the CPUID
  33                         instruction. This is an optional parameter that may be NULL.
  34   @param  RegisterEdx   Pointer to the 32-bit EDX value returned by the CPUID
  35                         instruction. This is an optional parameter that may be NULL.
  36
  37   @return Index
  38
  39 **/
  40 UINT32
  41 EFIAPI
  42 AsmCpuid (
  43   IN      UINT32                    Index,
  44   OUT     UINT32                    *RegisterEax,  OPTIONAL
  45   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  46   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  47   OUT     UINT32                    *RegisterEdx   OPTIONAL
  48   )
  49 {
  50   _asm {
  51     mov     eax, Index
  52     cpuid
  53     push    ecx
  54     mov     ecx, RegisterEax
  55     jecxz   SkipEax
  56     mov     [ecx], eax
  57 SkipEax:
  58     mov     ecx, RegisterEbx
  59     jecxz   SkipEbx
  60     mov     [ecx], ebx
  61 SkipEbx:
  62     pop     eax
  63     mov     ecx, RegisterEcx
  64     jecxz   SkipEcx
  65     mov     [ecx], eax
  66 SkipEcx:
  67     mov     ecx, RegisterEdx
  68     jecxz   SkipEdx
  69     mov     [ecx], edx
  70 SkipEdx:
  71     mov     eax, Index
  72   }
  73 }
  74