MdePkg/Library/BaseLib/Ia32/WriteCr4.c

   1 /** @file
   2   AsmWriteCr4 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   Writes a value to Control Register 4 (CR4).
  22
  23   Writes and returns a new value to CR4. This function is only available on
  24   IA-32 and X64. This writes a 32-bit value on IA-32 and a 64-bit value on X64.
  25
  26   @param  Cr4 The value to write to CR4.
  27
  28   @return The value written to CR4.
  29
  30 **/
  31 UINTN
  32 EFIAPI
  33 AsmWriteCr4 (
  34   UINTN  Value
  35   )
  36 {
  37   _asm {
  38     mov     eax, Value
  39     _emit  0x0f  // mov  cr4, eax
  40     _emit  0x22
  41     _emit  0xE0
  42   }
  43 }
  44