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
  17
  18 /**
  19   Retrieves CPUID information.
  20
  21   Executes the CPUID instruction with EAX set to the value specified by Index.
  22   This function always returns Index.
  23   If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
  24   If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
  25   If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
  26   If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
  27   This function is only available on IA-32 and X64.
  28
  29   @param  Index The 32-bit value to load into EAX prior to invoking the CPUID
  30                 instruction.
  31   @param  Eax   Pointer to the 32-bit EAX value returned by the CPUID
  32                 instruction. This is an optional parameter that may be NULL.
  33   @param  Ebx   Pointer to the 32-bit EBX value returned by the CPUID
  34                 instruction. This is an optional parameter that may be NULL.
  35   @param  Ecx   Pointer to the 32-bit ECX value returned by the CPUID
  36                 instruction. This is an optional parameter that may be NULL.
  37   @param  Edx   Pointer to the 32-bit EDX value returned by the CPUID
  38                 instruction. This is an optional parameter that may be NULL.
  39
  40   @return Index
  41
  42 **/
  43 UINT32
  44 EFIAPI
  45 AsmCpuid (
  46   IN      UINT32                    Index,
  47   OUT     UINT32                    *RegisterEax,  OPTIONAL
  48   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  49   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  50   OUT     UINT32                    *RegisterEdx   OPTIONAL
  51   )
  52 {
  53   _asm {
  54     mov     eax, Index
  55     cpuid
  56     push    ecx
  57     mov     ecx, RegisterEax
  58     jecxz   SkipEax
  59     mov     [ecx], eax
  60 SkipEax:
  61     mov     ecx, RegisterEbx
  62     jecxz   SkipEbx
  63     mov     [ecx], ebx
  64 SkipEbx:
  65     pop     eax
  66     mov     ecx, RegisterEcx
  67     jecxz   SkipEcx
  68     mov     [ecx], eax
  69 SkipEcx:
  70     mov     ecx, RegisterEdx
  71     jecxz   SkipEdx
  72     mov     [ecx], edx
  73 SkipEdx:
  74     mov     eax, Index
  75   }
  76 }
  77