MdePkg/Library/BaseLib/Ia32/CpuIdEx.c

   1 /** @file
   2   AsmCpuidEx function.
   3
   4   Copyright (c) 2006 - 2007, 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 // Include common header file for this module.
  17 //
  18
  19
  20 /**
  21   Retrieves CPUID information using an extended leaf identifier.
  22
  23   Executes the CPUID instruction with EAX set to the value specified by Index
  24   and ECX set to the value specified by SubIndex. This function always returns
  25   Index. This function is only available on IA-32 and x64.
  26
  27   If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
  28   If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
  29   If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
  30   If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
  31
  32   @param  Index     The 32-bit value to load into EAX prior to invoking the
  33                     CPUID instruction.
  34   @param  SubIndex  The 32-bit value to load into ECX prior to invoking the
  35                     CPUID instruction.
  36   @param  Eax       Pointer to the 32-bit EAX value returned by the CPUID
  37                     instruction. This is an optional parameter that may be
  38                     NULL.
  39   @param  Ebx       Pointer to the 32-bit EBX value returned by the CPUID
  40                     instruction. This is an optional parameter that may be
  41                     NULL.
  42   @param  Ecx       Pointer to the 32-bit ECX value returned by the CPUID
  43                     instruction. This is an optional parameter that may be
  44                     NULL.
  45   @param  Edx       Pointer to the 32-bit EDX value returned by the CPUID
  46                     instruction. This is an optional parameter that may be
  47                     NULL.
  48
  49   @return Index
  50
  51 **/
  52 UINT32
  53 EFIAPI
  54 AsmCpuidEx (
  55   IN      UINT32                    Index,
  56   IN      UINT32                    SubIndex,
  57   OUT     UINT32                    *RegisterEax,  OPTIONAL
  58   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  59   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  60   OUT     UINT32                    *RegisterEdx   OPTIONAL
  61   )
  62 {
  63   _asm {
  64     mov     eax, Index
  65     mov     ecx, SubIndex
  66     cpuid
  67     push    ecx
  68     mov     ecx, RegisterEax
  69     jecxz   SkipEax
  70     mov     [ecx], eax
  71 SkipEax:
  72     mov     ecx, RegisterEbx
  73     jecxz   SkipEbx
  74     mov     [ecx], ebx
  75 SkipEbx:
  76     pop     eax
  77     mov     ecx, RegisterEcx
  78     jecxz   SkipEcx
  79     mov     [ecx], eax
  80 SkipEcx:
  81     mov     ecx, RegisterEdx
  82     jecxz   SkipEdx
  83     mov     [ecx], edx
  84 SkipEdx:
  85     mov     eax, Index
  86   }
  87 }