Re: [PATCH v2 2/5] OvmfPkg: add library to track boot option loading/starting on the console

[Laszlo Ersek <lersek@redhat.com>]

On 02/20/19 09:16, Laszlo Ersek wrote:
> Introduce the Platform Boot Manager Print Status Code Library (for short,
> PlatformBmPrintScLib) class for catching and printing the LoadImage() /
> StartImage() preparations, and return statuses, that are reported by
> UefiBootManagerLib.
> 
> In the primary library instance, catch only such status codes that
> UefiBootManagerLib reports from the same module that contains
> PlatformBmPrintScLib. The intent is to establish a reporting-printing
> channel within BdsDxe, between UefiBootManagerLib and
> PlatformBmPrintScLib. Ignore status codes originating elsewhence, e.g.
> from UiApp's copy of UefiBootManagerLib.
> 
> Cc: Anthony Perard <anthony.perard@citrix.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Julien Grall <julien.grall@linaro.org>
> Cc: Ray Ni <ray.ni@intel.com>
> Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1515418
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     v2:
>     
>     - Split the status code handling to a separate library, so that it's
>       easy to reuse in ArmVirtPkg.
>     
>     - Rework the logic based on
>       <https://bugzilla.tianocore.org/show_bug.cgi?id=1398> and
>       <https://mantis.uefi.org/mantis/view.php?id=1885>, and follow Ray's
>       advice in
>       <http://mid.mail-archive.com/734D49CCEBEEF84792F5B80ED585239D5BACE29B@SHSMSX104.ccr.corp.intel.com>:
>     
>       - The boot option details are fetched via BootCurrent.
>     
>       - For reporting LoadImage() and StartImage() preparations, replace the
>         originally proposed PcdDebugCodeOsLoaderDetail status code with the
>         existent (edk2-specific) PcdProgressCodeOsLoaderLoad and
>         PcdProgressCodeOsLoaderStart status codes.
>     
>       - For reporting LoadImage() and StartImage() return values, replace
>         the originally proposed PcdDebugCodeOsLoaderDetail status code with
>         the standard EFI_SW_DXE_BS_EC_BOOT_OPTION_LOAD_ERROR and
>         EFI_SW_DXE_BS_EC_BOOT_OPTION_FAILED status codes.
>     
>       - For all four kinds of reports, replace the originally proposed "OS
>         Loader Detail" structure (and GUID) with the recently standardized
>         EFI_RETURN_STATUS_EXTENDED_DATA structure.
> 
>  OvmfPkg/OvmfPkg.dec                                           |   5 +
>  OvmfPkg/OvmfPkgIa32.dsc                                       |   1 +
>  OvmfPkg/OvmfPkgIa32X64.dsc                                    |   1 +
>  OvmfPkg/OvmfPkgX64.dsc                                        |   1 +
>  OvmfPkg/Include/Library/PlatformBmPrintScLib.h                |  41 +++
>  OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf |  66 +++++
>  OvmfPkg/Library/PlatformBmPrintScLib/StatusCodeHandler.c      | 310 ++++++++++++++++++++
>  7 files changed, 425 insertions(+)
> 
> diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
> index 7666297cf8f1..e50c6179a249 100644
> --- a/OvmfPkg/OvmfPkg.dec
> +++ b/OvmfPkg/OvmfPkg.dec
> @@ -45,6 +45,11 @@ [LibraryClasses]
>    #                  access.
>    PciCapPciSegmentLib|Include/Library/PciCapPciSegmentLib.h
>  
> +  ##  @libraryclass  Register a status code handler for printing the Boot
> +  #                  Manager's LoadImage() and StartImage() preparations, and
> +  #                  return codes, to the UEFI console.
> +  PlatformBmPrintScLib|Include/Library/PlatformBmPrintScLib.h
> +
>    ##  @libraryclass  Access QEMU's firmware configuration interface
>    #
>    QemuFwCfgLib|Include/Library/QemuFwCfgLib.h
> diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
> index f9216af479f4..5b885590b275 100644
> --- a/OvmfPkg/OvmfPkgIa32.dsc
> +++ b/OvmfPkg/OvmfPkgIa32.dsc
> @@ -348,6 +348,7 @@ [LibraryClasses.common.DXE_DRIVER]
>    UdpIoLib|MdeModulePkg/Library/DxeUdpIoLib/DxeUdpIoLib.inf
>    DpcLib|MdeModulePkg/Library/DxeDpcLib/DxeDpcLib.inf
>    PlatformBootManagerLib|OvmfPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf
> +  PlatformBmPrintScLib|OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf
>    QemuBootOrderLib|OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.inf
>    CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
>  !if $(SMM_REQUIRE) == TRUE
> diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
> index 1e470de74434..bbf0853ee6b9 100644
> --- a/OvmfPkg/OvmfPkgIa32X64.dsc
> +++ b/OvmfPkg/OvmfPkgIa32X64.dsc
> @@ -353,6 +353,7 @@ [LibraryClasses.common.DXE_DRIVER]
>    UdpIoLib|MdeModulePkg/Library/DxeUdpIoLib/DxeUdpIoLib.inf
>    DpcLib|MdeModulePkg/Library/DxeDpcLib/DxeDpcLib.inf
>    PlatformBootManagerLib|OvmfPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf
> +  PlatformBmPrintScLib|OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf
>    QemuBootOrderLib|OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.inf
>    CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
>  !if $(SMM_REQUIRE) == TRUE
> diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
> index e4929d8cf4a8..d81460f52041 100644
> --- a/OvmfPkg/OvmfPkgX64.dsc
> +++ b/OvmfPkg/OvmfPkgX64.dsc
> @@ -353,6 +353,7 @@ [LibraryClasses.common.DXE_DRIVER]
>    UdpIoLib|MdeModulePkg/Library/DxeUdpIoLib/DxeUdpIoLib.inf
>    DpcLib|MdeModulePkg/Library/DxeDpcLib/DxeDpcLib.inf
>    PlatformBootManagerLib|OvmfPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf
> +  PlatformBmPrintScLib|OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf
>    QemuBootOrderLib|OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.inf
>    CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
>  !if $(SMM_REQUIRE) == TRUE
> diff --git a/OvmfPkg/Include/Library/PlatformBmPrintScLib.h b/OvmfPkg/Include/Library/PlatformBmPrintScLib.h
> new file mode 100644
> index 000000000000..1777f9d7c947
> --- /dev/null
> +++ b/OvmfPkg/Include/Library/PlatformBmPrintScLib.h
> @@ -0,0 +1,41 @@
> +/** @file
> +  Register a status code handler for printing the Boot Manager's LoadImage()
> +  and StartImage() preparations, and return codes, to the UEFI console.
> +
> +  This feature enables users that are not accustomed to analyzing the firmware
> +  log to glean some information about UEFI boot option processing (loading and
> +  starting).
> +
> +  Copyright (C) 2019, Red Hat, Inc.
> +
> +  This program and the accompanying materials are licensed and made available
> +  under the terms and conditions of the BSD License which accompanies this
> +  distribution.  The full text of the license may be found at
> +  http://opensource.org/licenses/bsd-license.php
> +
> +  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
> +  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +**/
> +
> +#ifndef __PLATFORM_BM_PRINT_SC_LIB__
> +#define __PLATFORM_BM_PRINT_SC_LIB__
> +
> +#include <Uefi/UefiBaseType.h>
> +
> +/**
> +  Register a status code handler for printing the Boot Manager's LoadImage()
> +  and StartImage() preparations, and return codes, to the UEFI console.
> +
> +  @retval EFI_SUCCESS  The status code handler has been successfully
> +                       registered.
> +
> +  @return              Error codes propagated from boot services and from
> +                       EFI_RSC_HANDLER_PROTOCOL.
> +**/
> +EFI_STATUS
> +EFIAPI
> +PlatformBmPrintScRegisterHandler (
> +  VOID
> +  );
> +
> +#endif // __PLATFORM_BM_PRINT_SC_LIB__
> diff --git a/OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf b/OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf
> new file mode 100644
> index 000000000000..8f02e0b48236
> --- /dev/null
> +++ b/OvmfPkg/Library/PlatformBmPrintScLib/PlatformBmPrintScLib.inf
> @@ -0,0 +1,66 @@
> +## @file
> +# Register a status code handler for printing the Boot Manager's LoadImage()
> +# and StartImage() preparations, and return codes, to the UEFI console.
> +#
> +# This feature enables users that are not accustomed to analyzing the firmware
> +# log to glean some information about UEFI boot option processing (loading and
> +# starting).
> +#
> +# This library instance filters out (ignores) status codes that are not
> +# reported by the containing firmware module. The intent is to link this
> +# library instance into BdsDxe via PlatformBootManagerLib (which BdsDxe depends
> +# upon), then catch only those status codes that BdsDxe reports (which happens
> +# via UefiBootManagerLib). Status codes reported by other modules (such as
> +# UiApp), via UefiBootManagerLib or otherwise, are meant to be ignored.
> +#
> +# Copyright (C) 2019, Red Hat, Inc.
> +#
> +# This program and the accompanying materials are licensed and made available
> +# under the terms and conditions of the BSD License which accompanies this
> +# distribution.  The full text of the license may be found at
> +# http://opensource.org/licenses/bsd-license.php
> +#
> +# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
> +# WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +##
> +
> +[Defines]
> +  INF_VERSION    = 1.27
> +  BASE_NAME      = PlatformBmPrintScLib
> +  FILE_GUID      = 3417c705-903e-41a7-9485-3fafebf60917
> +  MODULE_TYPE    = DXE_DRIVER
> +  VERSION_STRING = 1.0
> +  LIBRARY_CLASS  = PlatformBmPrintScLib|DXE_DRIVER
> +
> +[Sources]
> +  StatusCodeHandler.c
> +
> +[Packages]
> +  MdeModulePkg/MdeModulePkg.dec
> +  MdePkg/MdePkg.dec
> +
> +[LibraryClasses]
> +  BaseMemoryLib
> +  DebugLib
> +  DevicePathLib
> +  MemoryAllocationLib
> +  PcdLib
> +  PrintLib
> +  UefiBootManagerLib
> +  UefiBootServicesTableLib
> +  UefiLib
> +  UefiRuntimeServicesTableLib
> +
> +[Pcd]
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdProgressCodeOsLoaderLoad  ## CONSUMES
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdProgressCodeOsLoaderStart ## CONSUMES
> +
> +[Protocols]
> +  gEfiRscHandlerProtocolGuid                                  ## CONSUMES
> +
> +[Guids]
> +  gEfiGlobalVariableGuid                                      ## CONSUMES
> +  gEfiStatusCodeSpecificDataGuid                              ## CONSUMES
> +
> +[Depex.common.DXE_DRIVER]
> +  gEfiRscHandlerProtocolGuid AND gEfiVariableArchProtocolGuid
> diff --git a/OvmfPkg/Library/PlatformBmPrintScLib/StatusCodeHandler.c b/OvmfPkg/Library/PlatformBmPrintScLib/StatusCodeHandler.c
> new file mode 100644
> index 000000000000..9806d3c7411e
> --- /dev/null
> +++ b/OvmfPkg/Library/PlatformBmPrintScLib/StatusCodeHandler.c
> @@ -0,0 +1,310 @@
> +/** @file
> +  Register a status code handler for printing the Boot Manager's LoadImage()
> +  and StartImage() preparations, and return codes, to the UEFI console.
> +
> +  This feature enables users that are not accustomed to analyzing the firmware
> +  log to glean some information about UEFI boot option processing (loading and
> +  starting).
> +
> +  This library instance filters out (ignores) status codes that are not
> +  reported by the containing firmware module. The intent is to link this
> +  library instance into BdsDxe via PlatformBootManagerLib (which BdsDxe depends
> +  upon), then catch only those status codes that BdsDxe reports (which happens
> +  via UefiBootManagerLib). Status codes reported by other modules (such as
> +  UiApp), via UefiBootManagerLib or otherwise, are meant to be ignored.
> +
> +  Copyright (C) 2019, Red Hat, Inc.
> +
> +  This program and the accompanying materials are licensed and made available
> +  under the terms and conditions of the BSD License which accompanies this
> +  distribution.  The full text of the license may be found at
> +  http://opensource.org/licenses/bsd-license.php
> +
> +  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
> +  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +**/
> +
> +#include <Library/BaseMemoryLib.h>
> +#include <Library/DebugLib.h>
> +#include <Library/DevicePathLib.h>
> +#include <Library/MemoryAllocationLib.h>
> +#include <Library/PcdLib.h>
> +#include <Library/PrintLib.h>
> +#include <Library/UefiBootManagerLib.h>
> +#include <Library/UefiBootServicesTableLib.h>
> +#include <Library/UefiLib.h>
> +#include <Library/UefiRuntimeServicesTableLib.h>
> +
> +#include <Protocol/ReportStatusCodeHandler.h>
> +
> +#include <Guid/GlobalVariable.h>
> +#include <Guid/StatusCodeDataTypeId.h>
> +
> +#include <Pi/PiStatusCode.h>
> +
> +
> +//
> +// Convenience variables for the status codes that are relevant for LoadImage()
> +// and StartImage() preparations and return codes.
> +//
> +STATIC EFI_STATUS_CODE_VALUE mLoadPrep;
> +STATIC EFI_STATUS_CODE_VALUE mLoadFail;
> +STATIC EFI_STATUS_CODE_VALUE mStartPrep;
> +STATIC EFI_STATUS_CODE_VALUE mStartFail;
> +
> +
> +/**
> +  Handle status codes reported through ReportStatusCodeLib /
> +  EFI_STATUS_CODE_PROTOCOL.ReportStatusCode(). Format matching status codes to
> +  the system console.
> +
> +  The highest TPL at which this handler can be registered with
> +  EFI_RSC_HANDLER_PROTOCOL.Register() is TPL_NOTIFY. That's because Print()
> +  uses EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL internally.

Sorry, this is a stale comment from v1; I should have updated it. The
callback now uses the variable services, and those are restricted to <=
TPL_CALLBACK.

The code is correct (it does use TPL_CALLBACK), so if there's no other
change necessary, I could update the comment on push too. I can also
post v3 just for this, if that's preferred.

Thanks
Laszlo

> +
> +  The parameter list of this function precisely matches that of
> +  EFI_STATUS_CODE_PROTOCOL.ReportStatusCode().
> +
> +  The return status of this function is ignored by the caller, but the function
> +  still returns sensible codes:
> +
> +  @retval EFI_SUCCESS               The status code has been processed; either
> +                                    as a no-op, due to filtering, or by
> +                                    formatting it to the system console.
> +
> +  @retval EFI_INVALID_PARAMETER     Unknown or malformed contents have been
> +                                    detected in Data.
> +
> +  @retval EFI_INCOMPATIBLE_VERSION  Unexpected UEFI variable behavior has been
> +                                    encountered.
> +
> +  @return                           Error codes propagated from underlying
> +                                    services.
> +**/
> +STATIC
> +EFI_STATUS
> +EFIAPI
> +HandleStatusCode (
> +  IN EFI_STATUS_CODE_TYPE  CodeType,
> +  IN EFI_STATUS_CODE_VALUE Value,
> +  IN UINT32                Instance,
> +  IN EFI_GUID              *CallerId,
> +  IN EFI_STATUS_CODE_DATA  *Data
> +  )
> +{
> +  UINTN                        VariableSize;
> +  UINT16                       BootCurrent;
> +  EFI_STATUS                   Status;
> +  CHAR16                       BootOptionName[ARRAY_SIZE (L"Boot####")];
> +  EFI_BOOT_MANAGER_LOAD_OPTION BmBootOption;
> +  BOOLEAN                      DevPathStringIsDynamic;
> +  CHAR16                       *DevPathString;
> +
> +  //
> +  // Ignore all status codes that are irrelevant for LoadImage() and
> +  // StartImage() preparations and return codes.
> +  //
> +  if (Value != mLoadPrep && Value != mLoadFail &&
> +      Value != mStartPrep && Value != mStartFail) {
> +    return EFI_SUCCESS;
> +  }
> +  //
> +  // Ignore status codes that are not reported by the same containing module.
> +  //
> +  if (!CompareGuid (CallerId, &gEfiCallerIdGuid)) {
> +    return EFI_SUCCESS;
> +  }
> +
> +  //
> +  // Sanity-check Data in case of failure reports.
> +  //
> +  if ((Value == mLoadFail || Value == mStartFail) &&
> +      (Data == NULL ||
> +       Data->HeaderSize != sizeof *Data ||
> +       Data->Size != sizeof (EFI_RETURN_STATUS_EXTENDED_DATA) - sizeof *Data ||
> +       !CompareGuid (&Data->Type, &gEfiStatusCodeSpecificDataGuid))) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: malformed Data\n", gEfiCallerBaseName,
> +      __FUNCTION__));
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  //
> +  // Get the number of the Boot#### option that the status code applies to.
> +  //
> +  VariableSize = sizeof BootCurrent;
> +  Status = gRT->GetVariable (EFI_BOOT_CURRENT_VARIABLE_NAME,
> +                  &gEfiGlobalVariableGuid, NULL /* Attributes */,
> +                  &VariableSize, &BootCurrent);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to get %g:\"%s\": %r\n",
> +      gEfiCallerBaseName, __FUNCTION__, &gEfiGlobalVariableGuid,
> +      EFI_BOOT_CURRENT_VARIABLE_NAME, Status));
> +    return Status;
> +  }
> +  if (VariableSize != sizeof BootCurrent) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: got %Lu bytes for %g:\"%s\", expected %Lu\n",
> +      gEfiCallerBaseName, __FUNCTION__, (UINT64)VariableSize,
> +      &gEfiGlobalVariableGuid, EFI_BOOT_CURRENT_VARIABLE_NAME,
> +      (UINT64)sizeof BootCurrent));
> +    return EFI_INCOMPATIBLE_VERSION;
> +  }
> +
> +  //
> +  // Get the Boot#### option that the status code applies to.
> +  //
> +  UnicodeSPrint (BootOptionName, sizeof BootOptionName, L"Boot%04x",
> +    BootCurrent);
> +  Status = EfiBootManagerVariableToLoadOption (BootOptionName, &BmBootOption);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR,
> +      "%a:%a: EfiBootManagerVariableToLoadOption(\"%s\"): %r\n",
> +      gEfiCallerBaseName, __FUNCTION__, BootOptionName, Status));
> +    return Status;
> +  }
> +
> +  //
> +  // Format the device path.
> +  //
> +  DevPathStringIsDynamic = TRUE;
> +  DevPathString = ConvertDevicePathToText (
> +                    BmBootOption.FilePath,
> +                    FALSE,                 // DisplayOnly
> +                    FALSE                  // AllowShortcuts
> +                    );
> +  if (DevPathString == NULL) {
> +    DevPathStringIsDynamic = FALSE;
> +    DevPathString = L"<out of memory while formatting device path>";
> +  }
> +
> +  //
> +  // Print the message to the console.
> +  //
> +  if (Value == mLoadPrep || Value == mStartPrep) {
> +    Print (
> +      L"%a: %a %s \"%s\" from %s\n",
> +      gEfiCallerBaseName,
> +      Value == mLoadPrep ? "loading" : "starting",
> +      BootOptionName,
> +      BmBootOption.Description,
> +      DevPathString
> +      );
> +  } else {
> +    Print (
> +      L"%a: failed to %a %s \"%s\" from %s: %r\n",
> +      gEfiCallerBaseName,
> +      Value == mLoadFail ? "load" : "start",
> +      BootOptionName,
> +      BmBootOption.Description,
> +      DevPathString,
> +      ((EFI_RETURN_STATUS_EXTENDED_DATA *)Data)->ReturnStatus
> +      );
> +  }
> +
> +  //
> +  // Done.
> +  //
> +  if (DevPathStringIsDynamic) {
> +    FreePool (DevPathString);
> +  }
> +  EfiBootManagerFreeLoadOption (&BmBootOption);
> +  return EFI_SUCCESS;
> +}
> +
> +
> +/**
> +  Unregister HandleStatusCode() at ExitBootServices().
> +
> +  (See EFI_RSC_HANDLER_PROTOCOL in Volume 3 of the Platform Init spec.)
> +
> +  @param[in] Event    Event whose notification function is being invoked.
> +
> +  @param[in] Context  Pointer to EFI_RSC_HANDLER_PROTOCOL, originally looked up
> +                      when HandleStatusCode() was registered.
> +**/
> +STATIC
> +VOID
> +EFIAPI
> +UnregisterAtExitBootServices (
> +  IN EFI_EVENT Event,
> +  IN VOID      *Context
> +  )
> +{
> +  EFI_RSC_HANDLER_PROTOCOL *StatusCodeRouter;
> +
> +  StatusCodeRouter = Context;
> +  StatusCodeRouter->Unregister (HandleStatusCode);
> +}
> +
> +
> +/**
> +  Register a status code handler for printing the Boot Manager's LoadImage()
> +  and StartImage() preparations, and return codes, to the UEFI console.
> +
> +  @retval EFI_SUCCESS  The status code handler has been successfully
> +                       registered.
> +
> +  @return              Error codes propagated from boot services and from
> +                       EFI_RSC_HANDLER_PROTOCOL.
> +**/
> +EFI_STATUS
> +EFIAPI
> +PlatformBmPrintScRegisterHandler (
> +  VOID
> +  )
> +{
> +  EFI_STATUS               Status;
> +  EFI_RSC_HANDLER_PROTOCOL *StatusCodeRouter;
> +  EFI_EVENT                ExitBootEvent;
> +
> +  Status = gBS->LocateProtocol (&gEfiRscHandlerProtocolGuid,
> +                  NULL /* Registration */, (VOID **)&StatusCodeRouter);
> +  ASSERT_EFI_ERROR (Status);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  //
> +  // Set the EFI_STATUS_CODE_VALUE convenience variables.
> +  //
> +  mLoadPrep  = PcdGet32 (PcdProgressCodeOsLoaderLoad);
> +  mLoadFail  = (EFI_SOFTWARE_DXE_BS_DRIVER |
> +                EFI_SW_DXE_BS_EC_BOOT_OPTION_LOAD_ERROR);
> +  mStartPrep = PcdGet32 (PcdProgressCodeOsLoaderStart);
> +  mStartFail = (EFI_SOFTWARE_DXE_BS_DRIVER |
> +                EFI_SW_DXE_BS_EC_BOOT_OPTION_FAILED);
> +
> +  //
> +  // Register the handler callback.
> +  //
> +  Status = StatusCodeRouter->Register (HandleStatusCode, TPL_CALLBACK);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to register status code handler: %r\n",
> +      gEfiCallerBaseName, __FUNCTION__, Status));
> +    return Status;
> +  }
> +
> +  //
> +  // Status code reporting and routing/handling extend into OS runtime. Since
> +  // we don't want our handler to survive the BDS phase, we have to unregister
> +  // the callback at ExitBootServices(). (See EFI_RSC_HANDLER_PROTOCOL in
> +  // Volume 3 of the Platform Init spec.)
> +  //
> +  Status = gBS->CreateEvent (
> +                  EVT_SIGNAL_EXIT_BOOT_SERVICES, // Type
> +                  TPL_CALLBACK,                  // NotifyTpl
> +                  UnregisterAtExitBootServices,  // NotifyFunction
> +                  StatusCodeRouter,              // NotifyContext
> +                  &ExitBootEvent                 // Event
> +                  );
> +  if (EFI_ERROR (Status)) {
> +    //
> +    // We have to unregister the callback right now, and fail the function.
> +    //
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to create ExitBootServices() event: "
> +      "%r\n", gEfiCallerBaseName, __FUNCTION__, Status));
> +    StatusCodeRouter->Unregister (HandleStatusCode);
> +    return Status;
> +  }
> +
> +  return EFI_SUCCESS;
> +}
>