MdePkg/Library/BaseLib/Ia32/CpuIdEx.c

   1 /** @file
   2   AsmCpuidEx function.
   3
   4   Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 /**
  10   Retrieves CPUID information using an extended leaf identifier.
  11
  12   Executes the CPUID instruction with EAX set to the value specified by Index
  13   and ECX set to the value specified by SubIndex. This function always returns
  14   Index. This function is only available on IA-32 and x64.
  15
  16   If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.
  17   If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.
  18   If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.
  19   If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.
  20
  21   @param  Index         The 32-bit value to load into EAX prior to invoking the
  22                         CPUID instruction.
  23   @param  SubIndex      The 32-bit value to load into ECX prior to invoking the
  24                         CPUID instruction.
  25   @param  RegisterEax   A pointer to the 32-bit EAX value returned by the CPUID
  26                         instruction. This is an optional parameter that may be
  27                         NULL.
  28   @param  RegisterEbx   A pointer to the 32-bit EBX value returned by the CPUID
  29                         instruction. This is an optional parameter that may be
  30                         NULL.
  31   @param  RegisterEcx   A pointer to the 32-bit ECX value returned by the CPUID
  32                         instruction. This is an optional parameter that may be
  33                         NULL.
  34   @param  RegisterEdx   A pointer to the 32-bit EDX value returned by the CPUID
  35                         instruction. This is an optional parameter that may be
  36                         NULL.
  37
  38   @return Index.
  39
  40 **/
  41 UINT32
  42 EFIAPI
  43 AsmCpuidEx (
  44   IN      UINT32                    Index,
  45   IN      UINT32                    SubIndex,
  46   OUT     UINT32                    *RegisterEax,  OPTIONAL
  47   OUT     UINT32                    *RegisterEbx,  OPTIONAL
  48   OUT     UINT32                    *RegisterEcx,  OPTIONAL
  49   OUT     UINT32                    *RegisterEdx   OPTIONAL
  50   )
  51 {
  52   _asm {
  53     mov     eax, Index
  54     mov     ecx, SubIndex
  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 }