Re: [PATCH v2] MdePkg/Library: Install dummy variable arch protocol

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Fri, 1 Mar 2019 at 12:14, Jagadeesh Ujja <jagadeesh.ujja@arm.com> wrote:
>
> In a system implementing the variable store in MM, there are no variable
> arch protocol and variable write arch protocol installed into the
> DXE_SMM protocol database. On such systems, it is not required to
> locate these protocols by the DXE runtime variable drivers because
> it can be assumed that these protocols are already installed in the MM
> context. But then such an implementation will deviate from the existing
> traditional MM based variable driver implementation.
>
> So in order to maintain consistency with the traditional MM variable
> driver implementation, allow platforms to install dummy versions of
> these protocols into the DXE protocol database but these protocol will
> not be consumed by non-secure variable service runtime driver.
>
> The Platform which uses StandaloneMM based secure variable storage
> have to include this library as below.
>
>   ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.inf {
>     <LibraryClasses>
>       NULL|MdePkg/Library/VariableMmDependency/VariableMmDependency.inf
>   }
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jagadeesh Ujja <jagadeesh.ujja@arm.com>
> ---
> Changes since v1:
> - This is a next version of patch
>    “MdeModulePkg/VariableSmmRuntimeDxe: Refactor locating Variable Arch Protocol”.
>    [https://lists.01.org/pipermail/edk2-devel/2019-February/036885.html]
> - Addressed the comments from Ard Biesheuvel and Zeng Star
> - Can this library be placed in MdePkg rather then the StandaloneMmPkg?
>

This does not belong in MdePkg. What is wrong with keeping it in
StandaloneMmPkg?

>  MdePkg/Library/VariableMmDependency/VariableMmDependency.c   | 85 ++++++++++++++++++++
>  MdePkg/Library/VariableMmDependency/VariableMmDependency.inf | 48 +++++++++++
>  2 files changed, 133 insertions(+)
>
> diff --git a/MdePkg/Library/VariableMmDependency/VariableMmDependency.c b/MdePkg/Library/VariableMmDependency/VariableMmDependency.c
> new file mode 100644
> index 0000000..6e5117e
> --- /dev/null
> +++ b/MdePkg/Library/VariableMmDependency/VariableMmDependency.c
> @@ -0,0 +1,85 @@
> +/** @file
> +  Runtime DXE part corresponding to StanaloneMM variable module.
> +
> +This module installs dummy variable arch protocol and dummy variable write arch protocol
> +to StandaloneMM runtime variable service.
> +

I think 'dummy' is a misnomer here. They are NULL protocols in the
sense that only their presence is signifcant, and the protocol does
not have an implementation. But this is true for traditional MM as
well.

> +Copyright (c) 2019, ARM Ltd. All rights reserved.
> +
> +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/DebugLib.h>
> +#include <Library/UefiBootServicesTableLib.h>
> +
> +/**
> +  Notify the system that the SMM variable driver is ready.
> +**/
> +VOID
> +VariableNotifySmmReady (
> +  VOID
> +  )
> +{
> +  EFI_STATUS            Status;
> +  EFI_HANDLE            Handle;
> +
> +  Handle = NULL;
> +  Status = gBS->InstallProtocolInterface (
> +                  &Handle,
> +                  &gEfiSmmVariableProtocolGuid,
> +                  EFI_NATIVE_INTERFACE,
> +                  NULL
> +                  );
> +  ASSERT_EFI_ERROR (Status);
> +}
> +
> +/**
> +  Notify the system that the SMM variable write driver is ready.
> +**/
> +VOID
> +VariableNotifySmmWriteReady (
> +  VOID
> +  )
> +{
> +  EFI_STATUS            Status;
> +  EFI_HANDLE            Handle;
> +
> +  Handle = NULL;
> +  Status = gBS->InstallProtocolInterface (
> +                  &Handle,
> +                  &gSmmVariableWriteGuid,
> +                  EFI_NATIVE_INTERFACE,
> +                  NULL
> +                  );
> +  ASSERT_EFI_ERROR (Status);
> +}
> +
> +/**
> +  The constructor function calls and installs dummy variable arch protocol and
> +  dummy variable write arch protocol to StandaloneMM runtime variable service
> +
> +  @param  ImageHandle   The firmware allocated handle for the EFI image.
> +  @param  SystemTable   A pointer to the Management mode System Table.
> +
> +  @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +VariableMmDependencyLibConstructor (
> +  IN EFI_HANDLE                           ImageHandle,
> +  IN EFI_SYSTEM_TABLE                     *SystemTable
> +  )
> +{
> +  VariableNotifySmmReady();
> +  VariableNotifySmmWriteReady();
> +  return EFI_SUCCESS;
> +}
> +

Can we replace all of this with a single call to
InstallMultipleProtocolInterfaces() please?


> diff --git a/MdePkg/Library/VariableMmDependency/VariableMmDependency.inf b/MdePkg/Library/VariableMmDependency/VariableMmDependency.inf
> new file mode 100644
> index 0000000..09fd200
> --- /dev/null
> +++ b/MdePkg/Library/VariableMmDependency/VariableMmDependency.inf
> @@ -0,0 +1,48 @@
> +## @file
> +#  Runtime DXE part corresponding to StanaloneMM variable module.
> +#
> +#  This module installs dummy variable arch protocol and dummy variable write arch protocol
> +#  to StandaloneMM runtime variable service.
> +#
> +# Copyright (c) 2019, ARM Ltd. All rights reserved.
> +# 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                    = 0x0001001A
> +  BASE_NAME                      = VariableMmDependency
> +  FILE_GUID                      = 64BC4129-778E-4867-BA07-13999A4DEC3F
> +  MODULE_TYPE                    = DXE_RUNTIME_DRIVER

Better use DXE_DRIVER here

> +  VERSION_STRING                 = 1.0
> +  PI_SPECIFICATION_VERSION       = 0x00010032

You can drop this

> +  LIBRARY_CLASS                  = NULL
> +  CONSTRUCTOR                    = VariableMmDependencyLibConstructor
> +
> +#
> +# The following information is for reference only and not required by the build tools.
> +#
> +#  VALID_ARCHITECTURES           = AARCH64
> +#
> +#
> +
> +[Sources]
> +  VariableMmDependency.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
> +
> +[Protocols]
> +  gEfiSmmVariableProtocolGuid
> +
> +[Guids]
> +  gSmmVariableWriteGuid
> +

This looks slightly inconsistent, but it actually matches what
MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.inf does.

So perhaps you could add the same annotation here as well:

[Protocols]
  gEfiSmmVariableProtocolGuid                   ## PRODUCES

[Guids]
  gSmmVariableWriteGuid                         ## PRODUCES
 ## GUID # Install protocol


> +[Depex]
> +  TRUE
> --
> 2.7.4
>