MdePkg/Library/BaseLib/Ia32/ReadCr4.c

   1 /** @file
   2   AsmReadCr4 function
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10
  11
  12 /**
  13   Reads the current value of the Control Register 4 (CR4).
  14
  15   Reads and returns the current value of CR4. This function is only available
  16   on IA-32 and x64. This returns a 32-bit value on IA-32 and a 64-bit value on
  17   x64.
  18
  19   @return The value of the Control Register 4 (CR4).
  20
  21 **/
  22 UINTN
  23 EFIAPI
  24 AsmReadCr4 (
  25   VOID
  26   )
  27 {
  28   __asm {
  29     _emit  0x0f  // mov  eax, cr4
  30     _emit  0x20
  31     _emit  0xE0
  32   }
  33 }
  34