MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c

   1 /** @file
   2   PEI Services Table Pointer Library for IA-32 and X64.
   3
   4   According to PI specification, the peiservice pointer is stored prior at IDT
   5   table in IA32 and x64 architecture.
   6
   7   Copyright (c) 2006 - 2007, Intel Corporation.<BR>
   8   All rights reserved. This program and the accompanying materials
   9   are licensed and made available under the terms and conditions of the BSD License
  10   which accompanies this distribution.  The full text of the license may be found at
  11   http://opensource.org/licenses/bsd-license.php
  12
  13   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  14   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  15
  16 **/
  17
  18 #include <PiPei.h>
  19
  20 #include <Library/BaseLib.h>
  21 #include <Library/PeiServicesTablePointerLib.h>
  22 #include <Library/DebugLib.h>
  23
  24 /**
  25
  26   The function returns the pointer to PeiServicee following
  27   PI1.0.
  28
  29   For IA32, the four-bytes field immediately prior to new IDT
  30   base addres is used to save the EFI_PEI_SERVICES**.
  31   For x64, the eight-bytes field immediately prior to new IDT
  32   base addres is used to save the EFI_PEI_SERVICES**
  33
  34   @return  The pointer to PeiServices.
  35
  36 **/
  37 EFI_PEI_SERVICES **
  38 EFIAPI
  39 GetPeiServicesTablePointer (
  40   VOID
  41   )
  42 {
  43   EFI_PEI_SERVICES  **PeiServices;
  44   IA32_DESCRIPTOR   Idtr;
  45
  46   AsmReadIdtr (&Idtr);
  47   PeiServices = (EFI_PEI_SERVICES **) (*(UINTN*)(Idtr.Base - sizeof (UINTN)));
  48   ASSERT (PeiServices != NULL);
  49   return PeiServices;
  50 }
  51
  52 /**
  53
  54   The function sets the pointer to PeiServicee following
  55   PI1.0.
  56
  57   For IA32, the four-bytes field immediately prior to new IDT
  58   base addres is used to save the EFI_PEI_SERVICES**.
  59   For x64, the eight-bytes field immediately prior to new IDT
  60   base addres is used to save the EFI_PEI_SERVICES**
  61
  62   @param PeiServicesTablePointer  The pointer to PeiServices.
  63
  64 **/
  65 VOID
  66 EFIAPI
  67 SetPeiServicesTablePointer (
  68   EFI_PEI_SERVICES ** PeiServicesTablePointer
  69   )
  70 {
  71   IA32_DESCRIPTOR   Idtr;
  72
  73   AsmReadIdtr (&Idtr);
  74   (*(UINTN*)(Idtr.Base - sizeof (UINTN))) = (UINTN)PeiServicesTablePointer;
  75 }
  76
  77