MdePkg/Library/BaseLib/Ia32/CpuIdEx.c

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