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[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / CpuId.c

/** @file\r
  AsmCpuid function.\r
\r
  Copyright (c) 2006 - 2007, Intel Corporation<BR>\r
  All rights reserved. This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
//\r
// Include common header file for this module.\r
//\r
\r
\r
/**\r
  Retrieves CPUID information.\r
\r
  Executes the CPUID instruction with EAX set to the value specified by Index.\r
  This function always returns Index.\r
  If Eax is not NULL, then the value of EAX after CPUID is returned in Eax.\r
  If Ebx is not NULL, then the value of EBX after CPUID is returned in Ebx.\r
  If Ecx is not NULL, then the value of ECX after CPUID is returned in Ecx.\r
  If Edx is not NULL, then the value of EDX after CPUID is returned in Edx.\r
  This function is only available on IA-32 and X64.\r
\r
  @param  Index The 32-bit value to load into EAX prior to invoking the CPUID\r
                instruction.\r
  @param  Eax   Pointer to the 32-bit EAX value returned by the CPUID\r
                instruction. This is an optional parameter that may be NULL.\r
  @param  Ebx   Pointer to the 32-bit EBX value returned by the CPUID\r
                instruction. This is an optional parameter that may be NULL.\r
  @param  Ecx   Pointer to the 32-bit ECX value returned by the CPUID\r
                instruction. This is an optional parameter that may be NULL.\r
  @param  Edx   Pointer to the 32-bit EDX value returned by the CPUID\r
                instruction. This is an optional parameter that may be NULL.\r
\r
  @return Index\r
\r
**/\r
UINT32\r
EFIAPI\r
AsmCpuid (\r
  IN      UINT32                    Index,\r
  OUT     UINT32                    *RegisterEax,  OPTIONAL\r
  OUT     UINT32                    *RegisterEbx,  OPTIONAL\r
  OUT     UINT32                    *RegisterEcx,  OPTIONAL\r
  OUT     UINT32                    *RegisterEdx   OPTIONAL\r
  )\r
{\r
  _asm {\r
    mov     eax, Index\r
    cpuid\r
    push    ecx\r
    mov     ecx, RegisterEax\r
    jecxz   SkipEax\r
    mov     [ecx], eax\r
SkipEax:\r
    mov     ecx, RegisterEbx\r
    jecxz   SkipEbx\r
    mov     [ecx], ebx\r
SkipEbx:\r
    pop     eax\r
    mov     ecx, RegisterEcx\r
    jecxz   SkipEcx\r
    mov     [ecx], eax\r
SkipEcx:\r
    mov     ecx, RegisterEdx\r
    jecxz   SkipEdx\r
    mov     [ecx], edx\r
SkipEdx:\r
    mov     eax, Index\r
  }\r
}\r
\r