回复: [edk2-devel] [PATCH v1 2/2] MdeModulePkg: Variable: Introduce MM based variable read service in PEI

["gaoliming" <gaoliming@byosoft.com.cn>]

Kun:
  Seemly, PcdMaxVariableSize is not used by this module. It can be removed. 

  And, has its functionality been verified in the real platform?

Thanks
Liming
> -----邮件原件-----
> 发件人: devel@edk2.groups.io <devel@edk2.groups.io> 代表 Kun Qin
> 发送时间: 2023年6月9日 4:45
> 收件人: devel@edk2.groups.io
> 抄送: Hao A Wu <hao.a.wu@intel.com>; Liming Gao
> <gaoliming@byosoft.com.cn>; Jian J Wang <jian.j.wang@intel.com>; Ronny
> Hansen <hansen.ronny@microsoft.com>; Shriram Masanamuthu
> Chinnathurai <shriramma@microsoft.com>; Preshit Harlikar
> <pharlikar@microsoft.com>
> 主题: [edk2-devel] [PATCH v1 2/2] MdeModulePkg: Variable: Introduce MM
> based variable read service in PEI
> 
> From: Kun Qin <kuqin@microsoft.com>
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4464
> 
> This change introduced the Standalone MM based variable read capability
> in PEI phase for applicable platforms (such as ARM platforms).
> 
> Similar to the x86 counterpart, MM communicate PPI is used to request
> variable information from Standalone MM environment.
> 
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> 
> Co-authored-by: Ronny Hansen <hansen.ronny@microsoft.com>
> Co-authored-by: Shriram Masanamuthu Chinnathurai
> <shriramma@microsoft.com>
> Co-authored-by: Preshit Harlikar <pharlikar@microsoft.com>
> Signed-off-by: Kun Qin <kuqin@microsoft.com>
> ---
>  MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c   |
> 381 ++++++++++++++++++++
>  MdeModulePkg/MdeModulePkg.dsc
> |   1 +
>  MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h   |
> 134 +++++++
>  MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf |
> 43 +++
>  4 files changed, 559 insertions(+)
> 
> diff --git
> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
> new file mode 100644
> index 000000000000..4f937e22e89e
> --- /dev/null
> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.c
> @@ -0,0 +1,381 @@
> +/** @file -- MmVariablePei.c
> 
> +  Provides interface for reading Secure System Variables during PEI.
> 
> +
> 
> +  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
> 
> +  Copyright (c) Microsoft Corporation.<BR>
> 
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> 
> +**/
> 
> +
> 
> +#include "MmVariablePei.h"
> 
> +
> 
> +#define MM_VARIABLE_COMM_BUFFER_OFFSET
> (SMM_COMMUNICATE_HEADER_SIZE +
> SMM_VARIABLE_COMMUNICATE_HEADER_SIZE)
> 
> +
> 
> +//
> 
> +// Module globals
> 
> +//
> 
> +EFI_PEI_READ_ONLY_VARIABLE2_PPI  mPeiSecureVariableRead = {
> 
> +  PeiMmGetVariable,
> 
> +  PeiMmGetNextVariableName
> 
> +};
> 
> +
> 
> +EFI_PEI_PPI_DESCRIPTOR  mPeiMmVariablePpi = {
> 
> +  (EFI_PEI_PPI_DESCRIPTOR_PPI |
> EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST),
> 
> +  &gEfiPeiReadOnlyVariable2PpiGuid,
> 
> +  &mPeiSecureVariableRead
> 
> +};
> 
> +
> 
> +/**
> 
> +  Entry point of PEI Secure Variable read driver
> 
> +
> 
> +  @param  FileHandle   Handle of the file being invoked.
> 
> +                       Type EFI_PEI_FILE_HANDLE is defined in
> FfsFindNextFile().
> 
> +  @param  PeiServices  General purpose services available to every
> PEIM.
> 
> +
> 
> +  @retval EFI_SUCCESS  If the interface could be successfully installed
> 
> +  @retval Others       Returned from PeiServicesInstallPpi()
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmVariableInitialize (
> 
> +  IN       EFI_PEI_FILE_HANDLE  FileHandle,
> 
> +  IN CONST EFI_PEI_SERVICES     **PeiServices
> 
> +  )
> 
> +{
> 
> +  return PeiServicesInstallPpi (&mPeiMmVariablePpi);
> 
> +}
> 
> +
> 
> +/**
> 
> +  Helper function to populate MM communicate header and variable
> communicate header
> 
> +  and then communicate to PEI.
> 
> +
> 
> +  @param[in, out] CommunicateBuffer       Size of the variable name.
> 
> +  @param[in]      CommunicateBufferSize   The entire buffer size to be
> sent to MM.
> 
> +  @param[in]      Function                The MM variable function
> value.
> 
> +
> 
> +  @retval EFI_INVALID_PARAMETER      Invalid parameter.
> 
> +  @retval EFI_SUCCESS                Find the specified variable.
> 
> +  @retval Others                     Errors returned by MM
> communicate or variable service.
> 
> +
> 
> +**/
> 
> +EFI_STATUS
> 
> +PopulateHeaderAndCommunicate (
> 
> +  IN OUT  UINT8  *CommunicateBuffer,
> 
> +  IN UINTN       CommunicateBufferSize,
> 
> +  IN UINTN       Function
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                       Status;
> 
> +  EFI_PEI_MM_COMMUNICATION_PPI     *MmCommunicationPpi;
> 
> +  EFI_MM_COMMUNICATE_HEADER        *MmCommunicateHeader;
> 
> +  SMM_VARIABLE_COMMUNICATE_HEADER  *MmVarCommsHeader;
> 
> +
> 
> +  // Minimal sanity check
> 
> +  if ((CommunicateBuffer == NULL) ||
> 
> +      (CommunicateBufferSize <
> MM_VARIABLE_COMM_BUFFER_OFFSET))
> 
> +  {
> 
> +    Status = EFI_INVALID_PARAMETER;
> 
> +    DEBUG ((DEBUG_ERROR, "%a: Invalid incoming parameters: %p and
> 0x%x\n", __func__, CommunicateBuffer, CommunicateBufferSize));
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  if ((Function !=
> SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME) &&
> 
> +      (Function != SMM_VARIABLE_FUNCTION_GET_VARIABLE))
> 
> +  {
> 
> +    Status = EFI_INVALID_PARAMETER;
> 
> +    DEBUG ((DEBUG_ERROR, "%a: Invalid function value: 0x%x\n",
> __func__, Function));
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  Status = PeiServicesLocatePpi (&gEfiPeiMmCommunicationPpiGuid, 0,
> NULL, (VOID **)&MmCommunicationPpi);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    DEBUG ((DEBUG_ERROR, "%a: Failed to locate PEI MM Communication
> PPI: %r\n", __func__, Status));
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  // Zero the entire Communication Buffer Header
> 
> +  MmCommunicateHeader = (EFI_MM_COMMUNICATE_HEADER
> *)CommunicateBuffer;
> 
> +
> 
> +  ZeroMem (MmCommunicateHeader,
> SMM_COMMUNICATE_HEADER_SIZE);
> 
> +
> 
> +  // Use gEfiSmmVariableProtocolGuid to request the MM variable service
> in Standalone MM
> 
> +  CopyMem ((VOID *)&MmCommunicateHeader->HeaderGuid,
> &gEfiSmmVariableProtocolGuid, sizeof (GUID));
> 
> +
> 
> +  // Program the MM header size
> 
> +  MmCommunicateHeader->MessageLength = CommunicateBufferSize -
> SMM_COMMUNICATE_HEADER_SIZE;
> 
> +
> 
> +  MmVarCommsHeader = (SMM_VARIABLE_COMMUNICATE_HEADER
> *)(CommunicateBuffer + SMM_COMMUNICATE_HEADER_SIZE);
> 
> +
> 
> +  // We are only supporting GetVariable and GetNextVariableName
> 
> +  MmVarCommsHeader->Function = Function;
> 
> +
> 
> +  // Send the MM request using MmCommunicationPei
> 
> +  Status = MmCommunicationPpi->Communicate (MmCommunicationPpi,
> CommunicateBuffer, &CommunicateBufferSize);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    // Received an error from MM interface.
> 
> +    DEBUG ((DEBUG_ERROR, "%a - MM Interface Error: %r\n", __func__,
> Status));
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  // MM request was successfully handled by the framework.
> 
> +  // Set status to the Variable Service Status Code
> 
> +  Status = MmVarCommsHeader->ReturnStatus;
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    // We received an error from Variable Service.
> 
> +    // We cant do anymore so return Status
> 
> +    if (Status != EFI_BUFFER_TOO_SMALL) {
> 
> +      DEBUG ((DEBUG_ERROR, "%a - Variable Service Error: %r\n",
> __func__, Status));
> 
> +    }
> 
> +
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +Exit:
> 
> +  return Status;
> 
> +}
> 
> +
> 
> +/**
> 
> +  This service retrieves a variable's value using its name and GUID.
> 
> +
> 
> +  This function is using the Secure Variable Store. If the Data
> 
> +  buffer is too small to hold the contents of the variable, the error
> 
> +  EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the required
> buffer
> 
> +  size to obtain the data.
> 
> +
> 
> +  @param  This                  A pointer to this instance of the
> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
> 
> +  @param  VariableName          A pointer to a null-terminated string
> that is the variable's name.
> 
> +  @param  VariableGuid          A pointer to an EFI_GUID that is the
> variable's GUID. The combination of
> 
> +                                VariableGuid and VariableName
> must be unique.
> 
> +  @param  Attributes            If non-NULL, on return, points to the
> variable's attributes.
> 
> +  @param  DataSize              On entry, points to the size in bytes
> of the Data buffer.
> 
> +                                On return, points to the size of the
> data returned in Data.
> 
> +  @param  Data                  Points to the buffer which will hold
> the returned variable value.
> 
> +                                May be NULL with a zero DataSize in
> order to determine the size of the buffer needed.
> 
> +
> 
> +  @retval EFI_SUCCESS           The variable was read successfully.
> 
> +  @retval EFI_NOT_FOUND         The variable was not found.
> 
> +  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the
> resulting data.
> 
> +                                DataSize is updated with the size
> required for
> 
> +                                the specified variable.
> 
> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize
> or Data is NULL.
> 
> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
> because of a device error.
> 
> +
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmGetVariable (
> 
> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
> 
> +  IN CONST  CHAR16 *VariableName,
> 
> +  IN CONST  EFI_GUID *VariableGuid,
> 
> +  OUT       UINT32 *Attributes, OPTIONAL
> 
> +  IN OUT    UINTN                            *DataSize,
> 
> +  OUT       VOID                             *Data OPTIONAL
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                                Status;
> 
> +  UINTN                                     MessageSize;
> 
> +  SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE
> *MmVarAccessHeader;
> 
> +  UINT8
> *MmCommunicateBuffer;
> 
> +  UINTN                                     RequiredPages;
> 
> +
> 
> +  // Check input parameters
> 
> +  if ((VariableName == NULL) || (VariableGuid == NULL) || (DataSize ==
> NULL)) {
> 
> +    return EFI_INVALID_PARAMETER;
> 
> +  }
> 
> +
> 
> +  if (VariableName[0] == 0) {
> 
> +    return EFI_NOT_FOUND;
> 
> +  }
> 
> +
> 
> +  if ((*DataSize > 0) && (Data == NULL)) {
> 
> +    return EFI_INVALID_PARAMETER;
> 
> +  }
> 
> +
> 
> +  // Allocate required pages to send MM request
> 
> +  MessageSize = MM_VARIABLE_COMM_BUFFER_OFFSET +
> 
> +                OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) +
> 
> +                StrSize (VariableName) + *DataSize;
> 
> +
> 
> +  RequiredPages       = EFI_SIZE_TO_PAGES (MessageSize);
> 
> +  MmCommunicateBuffer = (UINT8 *)AllocatePages (RequiredPages);
> 
> +
> 
> +  if (MmCommunicateBuffer == NULL) {
> 
> +    Status = EFI_OUT_OF_RESOURCES;
> 
> +    DEBUG ((DEBUG_ERROR, "%a: Failed to allocate memory: %r\n",
> __func__, Status));
> 
> +    return Status;
> 
> +  }
> 
> +
> 
> +  // Zero the entire Communication Buffer
> 
> +  ZeroMem (MmCommunicateBuffer, (RequiredPages * EFI_PAGE_SIZE));
> 
> +
> 
> +  //
> 
> +  // Program all payload structure contents
> 
> +  //
> 
> +  MmVarAccessHeader =
> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE
> *)(MmCommunicateBuffer + MM_VARIABLE_COMM_BUFFER_OFFSET);
> 
> +
> 
> +  // Variable GUID
> 
> +  CopyMem ((VOID *)&MmVarAccessHeader->Guid, VariableGuid, sizeof
> (GUID));
> 
> +
> 
> +  // Program the max amount of data we accept.
> 
> +  MmVarAccessHeader->DataSize = *DataSize;
> 
> +
> 
> +  // Get size of the variable name
> 
> +  MmVarAccessHeader->NameSize = StrSize (VariableName);
> 
> +
> 
> +  // Populate incoming variable name
> 
> +  CopyMem ((VOID *)&MmVarAccessHeader->Name, VariableName,
> MmVarAccessHeader->NameSize);
> 
> +
> 
> +  Status = PopulateHeaderAndCommunicate (MmCommunicateBuffer,
> MessageSize, SMM_VARIABLE_FUNCTION_GET_VARIABLE);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    // We received an error from either communicate or Variable Service.
> 
> +    if (Status != EFI_BUFFER_TOO_SMALL) {
> 
> +      DEBUG ((DEBUG_ERROR, "%a - Communite to MM for variable
> service errored: %r\n", __func__, Status));
> 
> +    }
> 
> +
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  Status = EFI_SUCCESS;
> 
> +
> 
> +  // User provided buffer is too small
> 
> +  if (*DataSize < MmVarAccessHeader->DataSize) {
> 
> +    Status = EFI_BUFFER_TOO_SMALL;
> 
> +  }
> 
> +
> 
> +Exit:
> 
> +  // Check if we need to set Attributes
> 
> +  if (Attributes != NULL) {
> 
> +    *Attributes = MmVarAccessHeader->Attributes;
> 
> +  }
> 
> +
> 
> +  *DataSize = MmVarAccessHeader->DataSize;
> 
> +
> 
> +  if (Status == EFI_SUCCESS) {
> 
> +    CopyMem ((VOID *)Data, (UINT8 *)MmVarAccessHeader->Name +
> MmVarAccessHeader->NameSize, *DataSize);
> 
> +  }
> 
> +
> 
> +  // Free the Communication Buffer
> 
> +  if (MmCommunicateBuffer != NULL) {
> 
> +    FreePages (MmCommunicateBuffer, RequiredPages);
> 
> +  }
> 
> +
> 
> +  return Status;
> 
> +}
> 
> +
> 
> +/**
> 
> +  Return the next variable name and GUID.
> 
> +
> 
> +  This function is called multiple times to retrieve the VariableName
> 
> +  and VariableGuid of all variables currently available in the system.
> 
> +  On each call, the previous results are passed into the interface,
> 
> +  and, on return, the interface returns the data for the next
> 
> +  interface. When the entire variable list has been returned,
> 
> +  EFI_NOT_FOUND is returned.
> 
> +
> 
> +  @param  This              A pointer to this instance of the
> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
> 
> +
> 
> +  @param  VariableNameSize  On entry, points to the size of the buffer
> pointed to by VariableName.
> 
> +                            On return, the size of the variable name
> buffer.
> 
> +  @param  VariableName      On entry, a pointer to a null-terminated
> string that is the variable's name.
> 
> +                            On return, points to the next variable's
> null-terminated name string.
> 
> +
> 
> +  @param  VariableGuid      On entry, a pointer to an EFI_GUID that is
> the variable's GUID.
> 
> +                            On return, a pointer to the next variable's
> GUID.
> 
> +
> 
> +  @retval EFI_SUCCESS           The variable was read successfully.
> 
> +  @retval EFI_NOT_FOUND         The variable could not be found.
> 
> +  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small
> for the resulting
> 
> +                                data. VariableNameSize is updated
> with the size
> 
> +                                required for the specified variable.
> 
> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
> 
> +                                VariableNameSize is NULL.
> 
> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
> because of a device error.
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmGetNextVariableName (
> 
> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
> 
> +  IN OUT UINTN                               *VariableNameSize,
> 
> +  IN OUT CHAR16                              *VariableName,
> 
> +  IN OUT EFI_GUID                            *VariableGuid
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                                       Status;
> 
> +  UINTN
> MessageSize;
> 
> +  UINT8
> *MmCommunicateBuffer;
> 
> +  SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME
> *MmVarGetNextVarHeader;
> 
> +  UINTN
> RequiredPages;
> 
> +
> 
> +  // Check input parameters
> 
> +  if ((VariableName == NULL) ||
> 
> +      (VariableGuid == NULL) ||
> 
> +      (VariableNameSize == NULL) ||
> 
> +      (*VariableNameSize == 0))
> 
> +  {
> 
> +    return EFI_INVALID_PARAMETER;
> 
> +  }
> 
> +
> 
> +  // Allocate required pages to send MM request
> 
> +  MessageSize = MM_VARIABLE_COMM_BUFFER_OFFSET +
> 
> +                OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE, Name) +
> 
> +                StrSize (VariableName) + *VariableNameSize;
> 
> +
> 
> +  RequiredPages       = EFI_SIZE_TO_PAGES (MessageSize);
> 
> +  MmCommunicateBuffer = (UINT8 *)AllocatePages (RequiredPages);
> 
> +
> 
> +  if (MmCommunicateBuffer == NULL) {
> 
> +    Status = EFI_OUT_OF_RESOURCES;
> 
> +    DEBUG ((DEBUG_ERROR, "%a: Failed to allocate memory: %r\n",
> __func__, Status));
> 
> +    return Status;
> 
> +  }
> 
> +
> 
> +  // Zero the entire Communication Buffer
> 
> +  ZeroMem (MmCommunicateBuffer, (RequiredPages * EFI_PAGE_SIZE));
> 
> +
> 
> +  //
> 
> +  // Program all payload structure contents
> 
> +  //
> 
> +  MmVarGetNextVarHeader =
> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME
> *)(MmCommunicateBuffer + MM_VARIABLE_COMM_BUFFER_OFFSET);
> 
> +
> 
> +  // Variable GUID
> 
> +  CopyMem ((VOID *)&MmVarGetNextVarHeader->Guid, VariableGuid,
> sizeof (GUID));
> 
> +
> 
> +  // Program the maximal length of name we can accept.
> 
> +  MmVarGetNextVarHeader->NameSize = *VariableNameSize;
> 
> +
> 
> +  // Populate incoming variable name
> 
> +  CopyMem ((VOID *)&MmVarGetNextVarHeader->Name, VariableName,
> MmVarGetNextVarHeader->NameSize);
> 
> +
> 
> +  // Send the MM request using MmCommunicationPei
> 
> +  Status = PopulateHeaderAndCommunicate (MmCommunicateBuffer,
> MessageSize, SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    // We received an error from either communicate or Variable Service.
> 
> +    if (Status != EFI_BUFFER_TOO_SMALL) {
> 
> +      DEBUG ((DEBUG_ERROR, "%a - Communite to MM for variable
> service errored: %r\n", __func__, Status));
> 
> +    }
> 
> +
> 
> +    goto Exit;
> 
> +  }
> 
> +
> 
> +  Status = EFI_SUCCESS;
> 
> +
> 
> +  // User provided buffer is too small
> 
> +  if (*VariableNameSize < MmVarGetNextVarHeader->NameSize) {
> 
> +    Status = EFI_BUFFER_TOO_SMALL;
> 
> +  }
> 
> +
> 
> +Exit:
> 
> +  // Update the name size to be returned
> 
> +  *VariableNameSize = MmVarGetNextVarHeader->NameSize;
> 
> +
> 
> +  if (Status == EFI_SUCCESS) {
> 
> +    CopyMem ((VOID *)VariableName, (UINT8
> *)MmVarGetNextVarHeader->Name, *VariableNameSize);
> 
> +    CopyMem ((VOID *)VariableGuid, (UINT8
> *)&(MmVarGetNextVarHeader->Guid), sizeof (EFI_GUID));
> 
> +  }
> 
> +
> 
> +  // Free the Communication Buffer
> 
> +  if (MmCommunicateBuffer != NULL) {
> 
> +    FreePages (MmCommunicateBuffer, RequiredPages);
> 
> +  }
> 
> +
> 
> +  return Status;
> 
> +}
> 
> diff --git a/MdeModulePkg/MdeModulePkg.dsc
> b/MdeModulePkg/MdeModulePkg.dsc
> index 5b1f50e9c084..1aedfe280ae1 100644
> --- a/MdeModulePkg/MdeModulePkg.dsc
> +++ b/MdeModulePkg/MdeModulePkg.dsc
> @@ -400,6 +400,7 @@ [Components]
>    MdeModulePkg/Application/VariableInfo/VariableInfo.inf
> 
> 
> MdeModulePkg/Universal/FaultTolerantWritePei/FaultTolerantWritePei.inf
> 
>    MdeModulePkg/Universal/Variable/Pei/VariablePei.inf
> 
> +  MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
> 
>    MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
> 
>    MdeModulePkg/Universal/TimestampDxe/TimestampDxe.inf
> 
> 
> MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
> 
> diff --git
> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
> new file mode 100644
> index 000000000000..0feed8cd1cb6
> --- /dev/null
> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.h
> @@ -0,0 +1,134 @@
> +/** @file -- MmVariablePei.h
> 
> +  Provides interface for reading Secure System Variables during PEI.
> 
> +
> 
> +  Copyright (c) Microsoft Corporation.
> 
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> 
> +**/
> 
> +
> 
> +#ifndef PEI_MM_VARIABLE_LIB_H_
> 
> +#define PEI_MM_VARIABLE_LIB_H_
> 
> +
> 
> +#include <PiPei.h>
> 
> +#include <Uefi/UefiSpec.h>
> 
> +
> 
> +#include <Library/DebugLib.h>
> 
> +#include <Library/PcdLib.h>
> 
> +#include <Library/BaseMemoryLib.h>
> 
> +#include <Library/PeimEntryPoint.h>
> 
> +#include <Library/PeiServicesLib.h>
> 
> +#include <Library/MemoryAllocationLib.h>
> 
> +#include <Library/HobLib.h>
> 
> +
> 
> +#include <Guid/SmmVariableCommon.h>
> 
> +
> 
> +#include <Ppi/ReadOnlyVariable2.h>
> 
> +#include <Ppi/MmCommunication.h>
> 
> +
> 
> +#include <Protocol/SmmVariable.h>
> 
> +#include <Protocol/MmCommunication.h>
> 
> +
> 
> +/**
> 
> +  Entry point of PEI Secure Variable read driver
> 
> +
> 
> +  @param  FileHandle   Handle of the file being invoked.
> 
> +                       Type EFI_PEI_FILE_HANDLE is defined in
> FfsFindNextFile().
> 
> +  @param  PeiServices  General purpose services available to every
> PEIM.
> 
> +
> 
> +  @retval EFI_SUCCESS  If the interface could be successfully installed
> 
> +  @retval Others       Returned from PeiServicesInstallPpi()
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmVariableInitialize (
> 
> +  IN       EFI_PEI_FILE_HANDLE  FileHandle,
> 
> +  IN CONST EFI_PEI_SERVICES     **PeiServices
> 
> +  );
> 
> +
> 
> +/**
> 
> +
> 
> +  This function enables the read of Secure Variables during PEI.
> 
> +
> 
> +  This function is using the Secure Variable Store.If the Data
> 
> +  buffer is too small to hold the contents of the variable, the error
> 
> +  EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the required
> buffer
> 
> +  size to obtain the data.
> 
> +
> 
> +  The function performs the following:
> 
> +
> 
> +  1) Creates an MM request
> 
> +  2) Fills out the following data structures for the Secure Variable
Service
> 
> +
> SMM_VARIABLE_COMMUNICATE_HEADER/SMM_VARIABLE_COMMUNICAT
> E_ACCESS_VARIABLE
> 
> +  3) Adds the MM data structures to the MM request.
> 
> +  4) Sends the MM request to EL3 using MmCommunicationPeiLib.
> 
> +  5) The MM request is sent to S-EL0.
> 
> +  6) The MM request is then handled by the registered handler with GUID:
> gEfiSmmVariableProtocolGuid
> 
> +
> 
> +  @param  This                  A pointer to this instance of the
> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
> 
> +  @param  VariableName          A pointer to a null-terminated string
> that is the variable's name.
> 
> +  @param  VariableGuid          A pointer to an EFI_GUID that is the
> variable's GUID. The combination of
> 
> +                                VariableGuid and VariableName
> must be unique.
> 
> +  @param  Attributes            If non-NULL, on return, points to the
> variable's attributes.
> 
> +  @param  DataSize              On entry, points to the size in bytes
> of the Data buffer.
> 
> +                                On return, points to the size of the
> data returned in Data.
> 
> +  @param  Data                  Points to the buffer which will hold
> the returned variable value.
> 
> +                                May be NULL with a zero DataSize in
> order to determine the size of the buffer needed.
> 
> +
> 
> +  @retval EFI_SUCCESS           The variable was read successfully.
> 
> +  @retval EFI_NOT_FOUND         The variable was not found.
> 
> +  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the
> resulting data.
> 
> +                                DataSize is updated with the size
> required for
> 
> +                                the specified variable.
> 
> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize
> or Data is NULL.
> 
> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
> because of a device error.
> 
> +
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmGetVariable (
> 
> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
> 
> +  IN CONST  CHAR16                           *VariableName,
> 
> +  IN CONST  EFI_GUID                         *VariableGuid,
> 
> +  OUT       UINT32                           *Attributes,
> 
> +  IN OUT    UINTN                            *DataSize,
> 
> +  OUT       VOID                             *Data OPTIONAL
> 
> +  );
> 
> +
> 
> +/**
> 
> +  Return the next variable name and GUID.
> 
> +
> 
> +  This function is called multiple times to retrieve the VariableName
> 
> +  and VariableGuid of all variables currently available in the system.
> 
> +  On each call, the previous results are passed into the interface,
> 
> +  and, on return, the interface returns the data for the next
> 
> +  interface. When the entire variable list has been returned,
> 
> +  EFI_NOT_FOUND is returned.
> 
> +
> 
> +  @param  This              A pointer to this instance of the
> EFI_PEI_READ_ONLY_VARIABLE2_PPI.
> 
> +
> 
> +  @param  VariableNameSize  On entry, points to the size of the buffer
> pointed to by VariableName.
> 
> +                            On return, the size of the variable name
> buffer.
> 
> +  @param  VariableName      On entry, a pointer to a null-terminated
> string that is the variable's name.
> 
> +                            On return, points to the next variable's
> null-terminated name string.
> 
> +
> 
> +  @param  VariableGuid      On entry, a pointer to an EFI_GUID that is
> the variable's GUID.
> 
> +                            On return, a pointer to the next variable's
> GUID.
> 
> +
> 
> +  @retval EFI_SUCCESS           The variable was read successfully.
> 
> +  @retval EFI_NOT_FOUND         The variable could not be found.
> 
> +  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small
> for the resulting
> 
> +                                data. VariableNameSize is updated
> with the size
> 
> +                                required for the specified variable.
> 
> +  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
> 
> +                                VariableNameSize is NULL.
> 
> +  @retval EFI_DEVICE_ERROR      The variable could not be retrieved
> because of a device error.
> 
> +**/
> 
> +EFI_STATUS
> 
> +EFIAPI
> 
> +PeiMmGetNextVariableName (
> 
> +  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI  *This,
> 
> +  IN OUT UINTN                               *VariableNameSize,
> 
> +  IN OUT CHAR16                              *VariableName,
> 
> +  IN OUT EFI_GUID                            *VariableGuid
> 
> +  );
> 
> +
> 
> +#endif /* PEI_MM_VARIABLE_LIB_H_ */
> 
> diff --git
> a/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
> b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
> new file mode 100644
> index 000000000000..d122703e9b5d
> --- /dev/null
> +++ b/MdeModulePkg/Universal/Variable/MmVariablePei/MmVariablePei.inf
> @@ -0,0 +1,43 @@
> +## @file -- MmVariablePei.inf
> 
> +# Provides interface for reading Secure System Variables during PEI.
> 
> +#
> 
> +# Copyright (c) Microsoft Corporation.
> 
> +# SPDX-License-Identifier: BSD-2-Clause-Patent
> 
> +##
> 
> +
> 
> +
> 
> +[Defines]
> 
> +  INF_VERSION                    = 0x00010005
> 
> +  BASE_NAME                      = MmVariablePei
> 
> +  FILE_GUID                      =
> CD660A87-454B-4346-A35C-3D89BF8ECFAF
> 
> +  MODULE_TYPE                    = PEIM
> 
> +  VERSION_STRING                 = 1.0
> 
> +  ENTRY_POINT                    = PeiMmVariableInitialize
> 
> +
> 
> +[Sources]
> 
> +  MmVariablePei.c
> 
> +  MmVariablePei.h
> 
> +
> 
> +[Packages]
> 
> +  MdePkg/MdePkg.dec
> 
> +  MdeModulePkg/MdeModulePkg.dec
> 
> +
> 
> +[LibraryClasses]
> 
> +  PcdLib
> 
> +  PeiServicesLib
> 
> +  PeimEntryPoint
> 
> +  MemoryAllocationLib
> 
> +  HobLib
> 
> +
> 
> +[Pcd]
> 
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize
> 
> +
> 
> +[Protocols]
> 
> +  gEfiSmmVariableProtocolGuid             ## CONSUMES
> 
> +
> 
> +[Ppis]
> 
> +  gEfiPeiReadOnlyVariable2PpiGuid         ## PRODUCES
> 
> +  gEfiPeiMmCommunicationPpiGuid           ## CONSUMES
> 
> +
> 
> +[Depex]
> 
> +  gEfiPeiMmCommunicationPpiGuid
> 
> --
> 2.40.1.windows.1
> 
> 
> 
> -=-=-=-=-=-=
> Groups.io Links: You receive all messages sent to this group.
> View/Reply Online (#105956):
> https://edk2.groups.io/g/devel/message/105956
> Mute This Topic: https://groups.io/mt/99415826/4905953
> Group Owner: devel+owner@edk2.groups.io
> Unsubscribe: https://edk2.groups.io/g/devel/unsub
> [gaoliming@byosoft.com.cn]
> -=-=-=-=-=-=
>