MdePkg/Library/BaseLib/Ia32/ReadMsr64.c

   1 /** @file
   2   AsmReadMsr64 function
   3
   4   Copyright (c) 2006 - 2021, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include <Library/RegisterFilterLib.h>
  10
  11 /**
  12   Returns a 64-bit Machine Specific Register(MSR).
  13
  14   Reads and returns the 64-bit MSR specified by Index. No parameter checking is
  15   performed on Index, and some Index values may cause CPU exceptions. The
  16   caller must either guarantee that Index is valid, or the caller must set up
  17   exception handlers to catch the exceptions. This function is only available
  18   on IA-32 and x64.
  19
  20   @param  Index The 32-bit MSR index to read.
  21
  22   @return The value of the MSR identified by Index.
  23
  24 **/
  25 UINT64
  26 AsmReadMsr64Internal (
  27   IN UINT32  Index
  28   )
  29 {
  30   _asm {
  31     mov     ecx, Index
  32     rdmsr
  33   }
  34 }
  35
  36 /**
  37   Returns a 64-bit Machine Specific Register(MSR).
  38
  39   Reads and returns the 64-bit MSR specified by Index. No parameter checking is
  40   performed on Index, and some Index values may cause CPU exceptions. The
  41   caller must either guarantee that Index is valid, or the caller must set up
  42   exception handlers to catch the exceptions. This function is only available
  43   on IA-32 and x64.
  44
  45   @param  Index The 32-bit MSR index to read.
  46
  47   @return The value of the MSR identified by Index.
  48
  49 **/
  50 UINT64
  51 EFIAPI
  52 AsmReadMsr64 (
  53   IN UINT32  Index
  54   )
  55 {
  56   UINT64   Value;
  57   BOOLEAN  Flag;
  58
  59   Flag = FilterBeforeMsrRead (Index, &Value);
  60   if (Flag) {
  61     Value = AsmReadMsr64Internal (Index);
  62   }
  63
  64   FilterAfterMsrRead (Index, &Value);
  65
  66   return Value;
  67 }