MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c

   1 /** @file
   2   UEFI Dxe DebugLib constructor that prevent some debug service after ExitBootServices event,
   3   because some pointer is nulled at that phase.
   4
   5   Copyright (c) 2018, Microsoft Corporation
   6   Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>
   7
   8   SPDX-License-Identifier: BSD-2-Clause-Patent
   9 **/
  10
  11 #include <Uefi.h>
  12 #include <Library/BaseLib.h>
  13 #include <Library/BaseMemoryLib.h>
  14
  15 //
  16 // BOOLEAN value to indicate if it is at the post ExitBootServices pahse
  17 //
  18 BOOLEAN  mPostEBS = FALSE;
  19
  20 static EFI_EVENT  mExitBootServicesEvent;
  21
  22 //
  23 // Pointer to SystemTable
  24 // This library instance may have a cycle consume with UefiBootServicesTableLib
  25 // because of the constructors.
  26 //
  27 EFI_SYSTEM_TABLE  *mDebugST;
  28
  29 /**
  30   This routine sets the mPostEBS for exit boot servies true
  31   to prevent DebugPort protocol dereferences when the pointer is nulled.
  32
  33   @param  Event        Event whose notification function is being invoked.
  34   @param  Context      Pointer to the notification function's context.
  35
  36 **/
  37 VOID
  38 EFIAPI
  39 ExitBootServicesCallback (
  40   EFI_EVENT  Event,
  41   VOID       *Context
  42   )
  43 {
  44   mPostEBS = TRUE;
  45   return;
  46 }
  47
  48 /**
  49   The constructor gets the pointers to the system table.
  50   And create a event to indicate it is after ExitBootServices.
  51
  52   @param  ImageHandle     The firmware allocated handle for the EFI image.
  53   @param  SystemTable     A pointer to the EFI System Table.
  54
  55   @retval EFI_SUCCESS     The constructor always returns EFI_SUCCESS.
  56
  57 **/
  58 EFI_STATUS
  59 EFIAPI
  60 DxeDebugLibConstructor (
  61   IN EFI_HANDLE        ImageHandle,
  62   IN EFI_SYSTEM_TABLE  *SystemTable
  63   )
  64 {
  65   mDebugST = SystemTable;
  66
  67   SystemTable->BootServices->CreateEvent (
  68                                EVT_SIGNAL_EXIT_BOOT_SERVICES,
  69                                TPL_NOTIFY,
  70                                ExitBootServicesCallback,
  71                                NULL,
  72                                &mExitBootServicesEvent
  73                                );
  74
  75   return EFI_SUCCESS;
  76 }
  77
  78 /**
  79   The destructor closes Exit Boot Services Event.
  80
  81   @param  ImageHandle   The firmware allocated handle for the EFI image.
  82   @param  SystemTable   A pointer to the EFI System Table.
  83
  84   @retval EFI_SUCCESS   The destructor always returns EFI_SUCCESS.
  85
  86 **/
  87 EFI_STATUS
  88 EFIAPI
  89 DxeDebugLibDestructor (
  90   IN EFI_HANDLE        ImageHandle,
  91   IN EFI_SYSTEM_TABLE  *SystemTable
  92   )
  93 {
  94   if (mExitBootServicesEvent != NULL) {
  95     SystemTable->BootServices->CloseEvent (mExitBootServicesEvent);
  96   }
  97
  98   return EFI_SUCCESS;
  99 }