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
  17
  18 /**
  19   Writes a value to Control Register 4 (CR4).
  20
  21   Writes and returns a new value to CR4. This function is only available on
  22   IA-32 and X64. This writes a 32-bit value on IA-32 and a 64-bit value on X64.
  23
  24   @param  Cr4 The value to write to CR4.
  25
  26   @return The value written to CR4.
  27
  28 **/
  29 UINTN
  30 EFIAPI
  31 AsmWriteCr4 (
  32   UINTN  Value
  33   )
  34 {
  35   _asm {
  36     mov     eax, Value
  37     _emit  0x0f  // mov  cr4, eax
  38     _emit  0x22
  39     _emit  0xE0
  40   }
  41 }
  42