MdePkg/Library/BaseLib/Ia32/CpuId.c

   1 /** @file
   2   AsmCpuid 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.
  22
  23   Executes the CPUID instruction with EAX set to the value specified by Index.
  24   This function always returns Index.
  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   This function is only available on IA-32 and X64.
  30
  31   @param  Index The 32-bit value to load into EAX prior to invoking the CPUID
  32                 instruction.
  33   @param  Eax   Pointer to the 32-bit EAX value returned by the CPUID
  34                 instruction. This is an optional parameter that may be NULL.
  35   @param  Ebx   Pointer to the 32-bit EBX value returned by the CPUID
  36                 instruction. This is an optional parameter that may be NULL.
  37   @param  Ecx   Pointer to the 32-bit ECX value returned by the CPUID
  38                 instruction. This is an optional parameter that may be NULL.
  39   @param  Edx   Pointer to the 32-bit EDX value returned by the CPUID
  40                 instruction. This is an optional parameter that may be NULL.
  41
  42   @return Index
  43
  44 **/
  45 UINT32
  46 EFIAPI
  47 AsmCpuid (
  48   IN      UINT32                    Index,
  49   OUT     UINT32                    *RegisterEax,  OPTIONAL
  50   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  51   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  52   OUT     UINT32                    *RegisterEdx   OPTIONAL
  53   )
  54 {
  55   _asm {
  56     mov     eax, Index
  57     cpuid
  58     push    ecx
  59     mov     ecx, RegisterEax
  60     jecxz   SkipEax
  61     mov     [ecx], eax
  62 SkipEax:
  63     mov     ecx, RegisterEbx
  64     jecxz   SkipEbx
  65     mov     [ecx], ebx
  66 SkipEbx:
  67     pop     eax
  68     mov     ecx, RegisterEcx
  69     jecxz   SkipEcx
  70     mov     [ecx], eax
  71 SkipEcx:
  72     mov     ecx, RegisterEdx
  73     jecxz   SkipEdx
  74     mov     [ecx], edx
  75 SkipEdx:
  76     mov     eax, Index
  77   }
  78 }
  79