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ArmPkg: SmmVariablePei: Introduce variable read service in PEI
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This change introduced the Standalone MM based variable read capability
in PEI phase for ARM based platforms.

Similar to the IA32 counterpart, MM communicate PPI is used to request
variable information from TrustZone.

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 <kun.qin@microsoft.com>
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@kuqin12 @rohansenUSA
@pharlikar @kenlautner
4 people authored and kenlautner committed Dec 19, 2023
1 parent 3e3ff42 commit 6305e61
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1 change: 1 addition & 0 deletions ArmPkg/ArmPkg.dsc
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ArmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.inf
ArmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
ArmPkg/Drivers/MmCommunicationPei/MmCommunicationPei.inf
ArmPkg/Drivers/SmmVariablePei/SmmVariablePei.inf
# MU_CHANGE [END]
ArmPkg/Drivers/MmCommunicationPei/MmCommunicationPei.inf

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231 changes: 231 additions & 0 deletions ArmPkg/Drivers/SmmVariablePei/SmmVariablePei.c
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/** @file -- SmmVariablePei.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 "SmmVariablePei.h"

//
// Module globals
//
EFI_PEI_READ_ONLY_VARIABLE2_PPI mPeiSecureVariableRead = {
PeiSmmGetVariable,
PeiSmmGetNextVariableName
};

EFI_PEI_PPI_DESCRIPTOR mPeiSmmVariablePpi = {
(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
PeiSmmVariableInitialize (
IN EFI_PEI_FILE_HANDLE FileHandle,
IN CONST EFI_PEI_SERVICES **PeiServices
)
{
return PeiServicesInstallPpi (&mPeiSmmVariablePpi);
}

/**
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
PeiSmmGetVariable (
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;
EFI_MM_COMMUNICATE_HEADER *CommunicateHeader;
SMM_VARIABLE_COMMUNICATE_HEADER *SmmVarCommsHeader;
SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *SmmVarAccessHeader;
UINT8 *MmCommunicateBuffer;
UINT8 RequiredPages;
EFI_PEI_MM_COMMUNICATION_PPI *MmCommunicationPpi;

// 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;
}

Status = PeiServicesLocatePpi (&gEfiPeiMmCommunicationPpiGuid, 0, NULL, (VOID **)&MmCommunicationPpi);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: Failed to locate PEI MM Communication PPI: %r\n", __FUNCTION__, Status));
return Status;
}

// Allocate required pages to send MM request
RequiredPages = EFI_SIZE_TO_PAGES (
sizeof (EFI_MM_COMMUNICATE_HEADER) + \
sizeof (SMM_VARIABLE_COMMUNICATE_HEADER) + \
sizeof (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE) + \
StrSize (VariableName) + *DataSize
);
MmCommunicateBuffer = (UINT8 *)AllocatePages (RequiredPages);

if (MmCommunicateBuffer == NULL) {
Status = EFI_OUT_OF_RESOURCES;
DEBUG ((DEBUG_ERROR, "%a: Failed to allocate memory: %r\n", __FUNCTION__, Status));
return Status;
}

// Zero the entire Communication Buffer
ZeroMem (MmCommunicateBuffer, (RequiredPages * EFI_PAGE_SIZE));

CommunicateHeader = (EFI_MM_COMMUNICATE_HEADER *)MmCommunicateBuffer;

SmmVarCommsHeader = (SMM_VARIABLE_COMMUNICATE_HEADER *)CommunicateHeader->Data;

SmmVarAccessHeader = (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE *)SmmVarCommsHeader->Data;

// Use gEfiSmmVariableProtocolGuid to request the SMM variable service in S-EL0
CopyMem ((VOID *)&CommunicateHeader->HeaderGuid, &gEfiSmmVariableProtocolGuid, sizeof (GUID));

// We are only supporting GetVariable
SmmVarCommsHeader->Function = SMM_VARIABLE_FUNCTION_GET_VARIABLE;

// Variable GUID
CopyMem ((VOID *)&SmmVarAccessHeader->Guid, VariableGuid, sizeof (GUID));

// Program the max amount of data we accept.
SmmVarAccessHeader->DataSize = *DataSize;

// Get size of the variable name
SmmVarAccessHeader->NameSize = StrSize (VariableName);

//
// Program all data structure sizes
//

// Program the MM header size
CommunicateHeader->MessageLength = sizeof (SMM_VARIABLE_COMMUNICATE_HEADER) - 1 + \
sizeof (SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE) - 1 + \
SmmVarAccessHeader->NameSize + SmmVarAccessHeader->DataSize;

// Size of the entire message sent to the secure world.
MessageSize = CommunicateHeader->MessageLength + \
sizeof (CommunicateHeader->HeaderGuid) + \
sizeof (CommunicateHeader->MessageLength);

CopyMem ((VOID *)&SmmVarAccessHeader->Name, VariableName, SmmVarAccessHeader->NameSize);

// Send the MM request using MmCommunicationPeiLib
Status = MmCommunicationPpi->Communicate (MmCommunicationPpi, CommunicateHeader, &MessageSize);

if (EFI_ERROR (Status)) {
// Received an error from MM interface.
DEBUG ((DEBUG_ERROR, "%a - MM Interface Error: %r\n", __FUNCTION__, Status));
goto Exit;
}

// MM request was successfully handled by the framework.
// Set status to the Variable Service Status Code
Status = SmmVarCommsHeader->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", __FUNCTION__, Status));
}

goto Exit;
}

Status = EFI_SUCCESS;

// User provided buffer is too small
if (*DataSize < SmmVarAccessHeader->DataSize) {
Status = EFI_BUFFER_TOO_SMALL;
}

Exit:
// Check if we need to set Attributes
if (Attributes != NULL) {
*Attributes = SmmVarAccessHeader->Attributes;
}

*DataSize = SmmVarAccessHeader->DataSize;

if (Status == EFI_SUCCESS) {
CopyMem ((VOID *)Data, (UINT8 *)SmmVarAccessHeader->Name + SmmVarAccessHeader->NameSize, *DataSize);
}

// Free the Communication Buffer
if (MmCommunicateBuffer != NULL) {
FreePages (MmCommunicateBuffer, RequiredPages);
}

return Status;
}

/**
* This function is not supported
* @retval EFI_UNSUPPORTED
*
**/
EFI_STATUS
EFIAPI
PeiSmmGetNextVariableName (
IN CONST EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
IN OUT UINTN *VariableNameSize,
IN OUT CHAR16 *VariableName,
IN OUT EFI_GUID *VariableGuid
)
{
return EFI_UNSUPPORTED;
}
110 changes: 110 additions & 0 deletions ArmPkg/Drivers/SmmVariablePei/SmmVariablePei.h
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/** @file -- SmmVariablePei.h
Provides interface for reading Secure System Variables during PEI.
Copyright (c) Microsoft Corporation.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/

#ifndef _PEI_SMM_VARIABLE_LIB_H_
#define _PEI_SMM_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/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
PeiSmmVariableInitialize (
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_COMMUNICATE_ACCESS_VARIABLE
3) Adds the SMM 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
PeiSmmGetVariable (
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
);

/**
* This function is not supported
* @retval EFI_UNSUPPORTED
*
**/
EFI_STATUS
EFIAPI
PeiSmmGetNextVariableName (
IN CONST EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
IN OUT UINTN *VariableNameSize,
IN OUT CHAR16 *VariableName,
IN OUT EFI_GUID *VariableGuid
);

#endif /* _PEI_SMM_VARIABLE_LIB_H_ */
46 changes: 46 additions & 0 deletions ArmPkg/Drivers/SmmVariablePei/SmmVariablePei.inf
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## @file -- SmmVariablePei.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 = SmmVariablePei
FILE_GUID = 7B93DCF8-8F5D-4BC1-A3E5-8288D337CAA0
MODULE_TYPE = PEIM
VERSION_STRING = 1.0
ENTRY_POINT = PeiSmmVariableInitialize

[Sources]
SmmVariablePei.c
SmmVariablePei.h

[Packages]
MdePkg/MdePkg.dec
MdeModulePkg/MdeModulePkg.dec
ArmPkg/ArmPkg.dec

[LibraryClasses]
PcdLib
PeiServicesLib
PeimEntryPoint
MemoryAllocationLib
HobLib

[Pcd]
gArmTokenSpaceGuid.PcdMmBufferBase
gArmTokenSpaceGuid.PcdMmBufferSize
gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize

[Protocols]
gEfiSmmVariableProtocolGuid ## CONSUMES

[Ppis]
gEfiPeiReadOnlyVariable2PpiGuid ## PRODUCES
gEfiPeiMmCommunicationPpiGuid ## CONSUMES

[Depex]
gEfiPeiMmCommunicationPpiGuid

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