MdePkg/Library/BaseLib/Ia32/WriteCr4.c

   1 /** @file
   2   AsmWriteCr4 function
   3
   4   Copyright (c) 2006 - 2008, 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   Writes a value to Control Register 4 (CR4).
  17
  18   Writes and returns a new value to CR4. This function is only available on
  19   IA-32 and x64. This writes a 32-bit value on IA-32 and a 64-bit value on x64.
  20
  21   @param  Value The value to write to CR4.
  22
  23   @return The value written to CR4.
  24
  25 **/
  26 UINTN
  27 EFIAPI
  28 AsmWriteCr4 (
  29   UINTN  Value
  30   )
  31 {
  32   _asm {
  33     mov     eax, Value
  34     _emit  0x0f  // mov  cr4, eax
  35     _emit  0x22
  36     _emit  0xE0
  37   }
  38 }
  39