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