[edk2-platforms] [PATCH v3 4/4] MinPlatformPkg: Add LargeVariableWriteLib

["Nate DeSimone" <nathaniel.l.desimone@intel.com>]

LargeVariableWriteLib is used to store large data sets using
the UEFI Variable Services. At time of writting, most UEFI
Variable Services implementations to not allow more than 64KB
of data to be stored in a single UEFI variable. This library
will split data sets across multiple variables as needed.

It adds the SetLargeVariable() API to provide this service.

The primary use for this library is to create binary compatible
drivers and OpROMs which need to work both with TianoCore and
other UEFI PI implementations. When customizing and recompiling
the platform firmware image is possible, adjusting the value of
PcdMaxVariableSize may provide a simpler solution to this
problem.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Cc: Isaac Oram <isaac.w.oram@intel.com>
Signed-off-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Isaac Oram <isaac.w.oram@intel.com>
---
 .../Include/Dsc/CoreCommonLib.dsc             |   1 +
 .../Include/Library/LargeVariableWriteLib.h   |  64 +++
 .../BaseLargeVariableWriteLib.inf             |  50 ++
 .../LargeVariableWriteLib.c                   | 479 ++++++++++++++++++
 4 files changed, 594 insertions(+)
 create mode 100644 Platform/Intel/MinPlatformPkg/Include/Library/LargeVariableWriteLib.h
 create mode 100644 Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/BaseLargeVariableWriteLib.inf
 create mode 100644 Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/LargeVariableWriteLib.c

diff --git a/Platform/Intel/MinPlatformPkg/Include/Dsc/CoreCommonLib.dsc b/Platform/Intel/MinPlatformPkg/Include/Dsc/CoreCommonLib.dsc
index 5f2ad3f0f0..78d66b9072 100644
--- a/Platform/Intel/MinPlatformPkg/Include/Dsc/CoreCommonLib.dsc
+++ b/Platform/Intel/MinPlatformPkg/Include/Dsc/CoreCommonLib.dsc
@@ -143,6 +143,7 @@
   SafeIntLib|MdePkg/Library/BaseSafeIntLib/BaseSafeIntLib.inf
   BmpSupportLib|MdeModulePkg/Library/BaseBmpSupportLib/BaseBmpSupportLib.inf
   LargeVariableReadLib|MinPlatformPkg/Library/BaseLargeVariableReadLib/BaseLargeVariableReadLib.inf
+  LargeVariableWriteLib|MinPlatformPkg/Library/BaseLargeVariableWriteLib/BaseLargeVariableWriteLib.inf
 
   #
   # CryptLib
diff --git a/Platform/Intel/MinPlatformPkg/Include/Library/LargeVariableWriteLib.h b/Platform/Intel/MinPlatformPkg/Include/Library/LargeVariableWriteLib.h
new file mode 100644
index 0000000000..6d597447f1
--- /dev/null
+++ b/Platform/Intel/MinPlatformPkg/Include/Library/LargeVariableWriteLib.h
@@ -0,0 +1,64 @@
+/** @file
+  Large Variable Write Lib
+
+  This library is used to store large data sets using the UEFI Variable Services.
+  At time of writting, most UEFI Variable Services implementations to not allow
+  more than 64KB of data to be stored in a single UEFI variable. This library
+  will split data sets across multiple variables as needed.
+
+  In the case where more than one variable is needed to store the data, an
+  integer number will be added to the end of the variable name. This number
+  will be incremented for each variable as needed to store the entire data set.
+
+  The primary use for this library is to create binary compatible drivers
+  and OpROMs which need to work both with TianoCore and other UEFI PI
+  implementations. When customizing and recompiling the platform firmware image
+  is possible, adjusting the value of PcdMaxVariableSize may provide a simpler
+  solution to this problem.
+
+  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Uefi/UefiBaseType.h>
+
+/**
+  Sets the value of a large variable.
+
+  @param[in]  VariableName       A Null-terminated string that is the name of the vendor's variable.
+                                 Each VariableName is unique for each VendorGuid. VariableName must
+                                 contain 1 or more characters. If VariableName is an empty string,
+                                 then EFI_INVALID_PARAMETER is returned.
+  @param[in]  VendorGuid         A unique identifier for the vendor.
+  @param[in]  LockVariable       If TRUE, any further writes to the variable will be prevented until the next reset.
+                                 Note: LockVariable must be FALSE when running in SMM or after ExitBootServices.
+  @param[in]  DataSize           The size in bytes of the Data buffer. A size of zero causes the variable to be deleted.
+                                 If DataSize is zero, then LockVariable must be FALSE since a variable that does not
+                                 exist cannot be locked.
+  @param[in]  Data               The contents for the variable.
+
+  @retval EFI_SUCCESS            The firmware has successfully stored the variable and its data as
+                                 defined by the Attributes.
+  @retval EFI_INVALID_PARAMETER  An invalid combination of LockVariable, name, and GUID was supplied, or the
+                                 DataSize exceeds the maximum allowed.
+  @retval EFI_INVALID_PARAMETER  VariableName is an empty string.
+  @retval EFI_INVALID_PARAMETER  DataSize is zero and LockVariable is TRUE
+  @retval EFI_OUT_OF_RESOURCES   Not enough storage is available to hold the variable and its data.
+  @retval EFI_OUT_OF_RESOURCES   The VariableName is longer than 1018 characters
+  @retval EFI_DEVICE_ERROR       The variable could not be retrieved due to a hardware error.
+  @retval EFI_WRITE_PROTECTED    The variable in question is read-only.
+  @retval EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
+
+  @retval EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.
+
+**/
+EFI_STATUS
+EFIAPI
+SetLargeVariable (
+  IN  CHAR16                       *VariableName,
+  IN  EFI_GUID                     *VendorGuid,
+  IN  BOOLEAN                      LockVariable,
+  IN  UINTN                        DataSize,
+  IN  VOID                         *Data
+  );
diff --git a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/BaseLargeVariableWriteLib.inf b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/BaseLargeVariableWriteLib.inf
new file mode 100644
index 0000000000..afecb31e29
--- /dev/null
+++ b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/BaseLargeVariableWriteLib.inf
@@ -0,0 +1,50 @@
+## @file
+# Component description file for Large Variable Write Library
+#
+# This library is used to store large data sets using the UEFI Variable Services.
+# At time of writting, most UEFI Variable Services implementations to not allow
+# more than 64KB of data to be stored in a single UEFI variable. This library
+# will split data sets across multiple variables as needed.
+#
+# In the case where more than one variable is needed to store the data, an
+# integer number will be added to the end of the variable name. This number
+# will be incremented for each variable as needed to store the entire data set.
+#
+# The primary use for this library is to create binary compatible drivers
+# and OpROMs which need to work both with TianoCore and other UEFI PI
+# implementations. When customizing and recompiling the platform firmware image
+# is possible, adjusting the value of PcdMaxVariableSize may provide a simpler
+# solution to this problem.
+#
+# Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = BaseLargeVariableWriteLib
+  FILE_GUID                      = 13E7DD75-FBE0-4B92-87A9-6BED253EB99E
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = LargeVariableWriteLib
+
+#
+#  VALID_ARCHITECTURES           = IA32 X64 EBC
+#
+
+[Sources]
+  LargeVariableWriteLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MinPlatformPkg/MinPlatformPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  PrintLib
+  VariableReadLib
+  VariableWriteLib
diff --git a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/LargeVariableWriteLib.c b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/LargeVariableWriteLib.c
new file mode 100644
index 0000000000..5cf4776707
--- /dev/null
+++ b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableWriteLib/LargeVariableWriteLib.c
@@ -0,0 +1,479 @@
+/** @file
+  Large Variable Write Lib
+
+  This library is used to store large data sets using the UEFI Variable Services.
+  At time of writting, most UEFI Variable Services implementations to not allow
+  more than 64KB of data to be stored in a single UEFI variable. This library
+  will split data sets across multiple variables as needed.
+
+  In the case where more than one variable is needed to store the data, an
+  integer number will be added to the end of the variable name. This number
+  will be incremented for each variable as needed to store the entire data set.
+
+  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Uefi.h>
+#include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/PrintLib.h>
+#include <Library/VariableReadLib.h>
+#include <Library/VariableWriteLib.h>
+
+//
+// 1024 was choosen because this is the size of the SMM communication buffer
+// used by VariableDxeSmm to transfer the VariableName from DXE to SMM. Choosing
+// the same size will prevent this library from limiting variable names any
+// more than the MdeModulePkg implementation of UEFI Variable Services does.
+//
+#define MAX_VARIABLE_NAME_SIZE      1024
+
+//
+// The 2012 Windows Hardware Requirements specified a minimum variable size of
+// 32KB. By setting the maximum allowed number of variables to 0x20000, this
+// allows up to 4GB of data to be stored on most UEFI implementations in
+// existence. Older UEFI implementations were known to only provide 8KB per
+// variable. In this case, up to 1GB can be stored. Since 1GB vastly exceeds the
+// size of any known NvStorage FV, choosing this number should effectively
+// enable all available NvStorage space to be used to store the given data.
+//
+#define MAX_VARIABLE_SPLIT          131072
+
+//
+// There are 6 digits in the number 131072, which means the length of the string
+// representation of this number will be at most 6 characters long.
+//
+#define MAX_VARIABLE_SPLIT_DIGITS   6
+
+//
+// On some architectures (Ex. Itanium) there a requirement to
+// maintain DWORD alignment of the variable data. Hence the
+// maximum possible padding size is 3.
+//
+#define MAX_VARIABLE_NAME_PAD_SIZE  3
+
+/**
+  Returns the amount of space remaining for storage of
+  non-volatile runtime accessible UEFI variables. Runtime accessible UEFI
+  variables are chosen because this is a BASE LibraryClass. Accordingly, it is
+  possible for a Runtime DXE driver to include this library. To simplify
+  implementation we only consider the runtime accessible case.
+
+  @retval The remaining storage space for non-volatile runtime accessible UEFI variables in bytes.
+
+**/
+UINT64
+GetRemainingVariableStorageSpace (
+  VOID
+  )
+{
+  EFI_STATUS      Status;
+  UINT64          MaximumVariableStorageSize;
+  UINT64          RemainingVariableStorageSize;
+  UINT64          MaximumVariableSize;
+
+  Status                        = EFI_SUCCESS;
+  MaximumVariableStorageSize    = 0;
+  RemainingVariableStorageSize  = 0;
+  MaximumVariableSize           = 0;
+
+  Status = VarLibQueryVariableInfo (
+             EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+             &MaximumVariableStorageSize,
+             &RemainingVariableStorageSize,
+             &MaximumVariableSize
+             );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "GetVariableSplitSize: QueryVariableInfo failed, Status = %r\n", Status));
+    ASSERT_EFI_ERROR (Status);
+    return 0;
+  }
+
+  return RemainingVariableStorageSize;
+}
+
+/**
+  Returns the maximum size of an individual non-volatile runtime accessible
+  UEFI variable. Runtime accessible UEFI variables are chosen because this is
+  a BASE LibraryClass. Accordingly, it is possible for a Runtime DXE driver to
+  include this library. To simplify implementation we only consider the runtime
+  accessible case.
+
+  @param[in] VariableNameLength         Length of the variable name
+
+  @retval The maximum size of an individual UEFI variable.
+
+**/
+UINT64
+GetVariableSplitSize (
+  IN  UINTN                        VariableNameLength
+  )
+{
+  EFI_STATUS      Status;
+  UINT64          MaximumVariableStorageSize;
+  UINT64          RemainingVariableStorageSize;
+  UINT64          VariableSplitSize;
+
+  Status                        = EFI_SUCCESS;
+  MaximumVariableStorageSize    = 0;
+  RemainingVariableStorageSize  = 0;
+  VariableSplitSize             = 0;
+
+  Status = VarLibQueryVariableInfo (
+             EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+             &MaximumVariableStorageSize,
+             &RemainingVariableStorageSize,
+             &VariableSplitSize
+             );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "GetVariableSplitSize: QueryVariableInfo failed, Status = %r\n", Status));
+    ASSERT_EFI_ERROR (Status);
+    return 0;
+  } else {
+    //
+    // The Variable Name counts as part of the consumed NV storage
+    // space for a UEFI Variable
+    //
+    if ((((VariableNameLength + 1) * sizeof (CHAR16)) + MAX_VARIABLE_NAME_PAD_SIZE) >= VariableSplitSize) {
+      VariableSplitSize = 0;
+    } else {
+      VariableSplitSize -= ((VariableNameLength + 1) * sizeof (CHAR16)) + MAX_VARIABLE_NAME_PAD_SIZE;
+    }
+  }
+
+  return VariableSplitSize;
+}
+
+/**
+  Deletes a large variable.
+
+  @param[in]  VariableName       A Null-terminated string that is the name of the vendor's variable.
+                                 Each VariableName is unique for each VendorGuid. VariableName must
+                                 contain 1 or more characters. If VariableName is an empty string,
+                                 then EFI_INVALID_PARAMETER is returned.
+  @param[in]  VendorGuid         A unique identifier for the vendor.
+
+  @retval EFI_SUCCESS            The firmware has successfully deleted the variable and its data as
+                                 defined by the Attributes.
+  @retval EFI_INVALID_PARAMETER  An invalid combination of name, and GUID was supplied.
+  @retval EFI_INVALID_PARAMETER  VariableName is an empty string.
+  @retval EFI_OUT_OF_RESOURCES   The VariableName is longer than 1018 characters
+  @retval EFI_DEVICE_ERROR       The variable could not be retrieved due to a hardware error.
+  @retval EFI_WRITE_PROTECTED    The variable in question is read-only.
+  @retval EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
+
+  @retval EFI_NOT_FOUND          The variable trying to be deleted was not found.
+
+**/
+EFI_STATUS
+EFIAPI
+DeleteLargeVariableInternal (
+  IN  CHAR16                       *VariableName,
+  IN  EFI_GUID                     *VendorGuid
+  )
+{
+  CHAR16        TempVariableName[MAX_VARIABLE_NAME_SIZE];
+  EFI_STATUS    Status;
+  EFI_STATUS    Status2;
+  UINTN         VarDataSize;
+  UINTN         Index;
+
+  VarDataSize = 0;
+
+  //
+  // First check if a variable with the given name exists
+  //
+  Status = VarLibGetVariable (VariableName, VendorGuid, NULL, &VarDataSize, NULL);
+  if (Status == EFI_BUFFER_TOO_SMALL) {
+    DEBUG ((DEBUG_INFO, "DeleteLargeVariableInternal: Deleting Single Variable\n"));
+    Status = VarLibSetVariable (
+                VariableName,
+                VendorGuid,
+                EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                0,
+                NULL
+                );
+    goto Done;
+  } else if (Status == EFI_NOT_FOUND) {
+
+    //
+    // Check if the first variable of a multi-variable set exists
+    //
+    if (StrLen (VariableName) >= (MAX_VARIABLE_NAME_SIZE - MAX_VARIABLE_SPLIT_DIGITS)) {
+      DEBUG ((DEBUG_ERROR, "DeleteLargeVariableInternal: Variable name too long\n"));
+      Status = EFI_OUT_OF_RESOURCES;
+      goto Done;
+    }
+    VarDataSize = 0;
+    Index       = 0;
+    ZeroMem (TempVariableName, MAX_VARIABLE_NAME_SIZE);
+    UnicodeSPrint (TempVariableName, MAX_VARIABLE_NAME_SIZE, L"%s%d", VariableName, Index);
+    Status = VarLibGetVariable (TempVariableName, VendorGuid, NULL, &VarDataSize, NULL);
+    if (Status == EFI_BUFFER_TOO_SMALL) {
+
+      //
+      // The first variable exists. Delete all the variables.
+      //
+      DEBUG ((DEBUG_INFO, "DeleteLargeVariableInternal: Multiple Variables Found\n"));
+      Status = EFI_SUCCESS;
+      for (Index = 0; Index < MAX_VARIABLE_SPLIT; Index++) {
+        VarDataSize = 0;
+        ZeroMem (TempVariableName, MAX_VARIABLE_NAME_SIZE);
+        UnicodeSPrint (TempVariableName, MAX_VARIABLE_NAME_SIZE, L"%s%d", VariableName, Index);
+        DEBUG ((DEBUG_INFO, "Deleting %s, Guid = %g\n", TempVariableName, VendorGuid));
+        Status2 = VarLibSetVariable (
+                    TempVariableName,
+                    VendorGuid,
+                    EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                    0,
+                    NULL
+                    );
+        if (Status2 == EFI_NOT_FOUND) {
+          DEBUG ((DEBUG_INFO, "DeleteLargeVariableInternal: Deletion Complete.\n"));
+          break;
+        } else if (EFI_ERROR (Status2)) {
+          DEBUG ((DEBUG_ERROR, "DeleteLargeVariableInternal: Error deleting variable: Status = %r\n", Status2));
+          Status = Status2;
+        }
+      }   // End of for loop
+    } else {
+      Status = EFI_NOT_FOUND;
+    }
+  }
+Done:
+  DEBUG ((DEBUG_ERROR, "DeleteLargeVariableInternal: Status = %r\n", Status));
+  return Status;
+}
+
+/**
+  Sets the value of a large variable.
+
+  @param[in]  VariableName       A Null-terminated string that is the name of the vendor's variable.
+                                 Each VariableName is unique for each VendorGuid. VariableName must
+                                 contain 1 or more characters. If VariableName is an empty string,
+                                 then EFI_INVALID_PARAMETER is returned.
+  @param[in]  VendorGuid         A unique identifier for the vendor.
+  @param[in]  LockVariable       If TRUE, any further writes to the variable will be prevented until the next reset.
+                                 Note: LockVariable must be FALSE when running in SMM or after ExitBootServices.
+  @param[in]  DataSize           The size in bytes of the Data buffer. A size of zero causes the variable to be deleted.
+                                 If DataSize is zero, then LockVariable must be FALSE since a variable that does not
+                                 exist cannot be locked.
+  @param[in]  Data               The contents for the variable.
+
+  @retval EFI_SUCCESS            The firmware has successfully stored the variable and its data as
+                                 defined by the Attributes.
+  @retval EFI_INVALID_PARAMETER  An invalid combination of LockVariable, name, and GUID was supplied, or the
+                                 DataSize exceeds the maximum allowed.
+  @retval EFI_INVALID_PARAMETER  VariableName is an empty string.
+  @retval EFI_INVALID_PARAMETER  DataSize is zero and LockVariable is TRUE
+  @retval EFI_OUT_OF_RESOURCES   Not enough storage is available to hold the variable and its data.
+  @retval EFI_OUT_OF_RESOURCES   The VariableName is longer than 1018 characters
+  @retval EFI_DEVICE_ERROR       The variable could not be retrieved due to a hardware error.
+  @retval EFI_WRITE_PROTECTED    The variable in question is read-only.
+  @retval EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
+
+  @retval EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.
+
+**/
+EFI_STATUS
+EFIAPI
+SetLargeVariable (
+  IN  CHAR16                       *VariableName,
+  IN  EFI_GUID                     *VendorGuid,
+  IN  BOOLEAN                      LockVariable,
+  IN  UINTN                        DataSize,
+  IN  VOID                         *Data
+  )
+{
+  CHAR16        TempVariableName[MAX_VARIABLE_NAME_SIZE];
+  UINT64        VariableSplitSize;
+  UINT64        RemainingVariableStorage;
+  EFI_STATUS    Status;
+  EFI_STATUS    Status2;
+  UINTN         VariableNameLength;
+  UINTN         Index;
+  UINTN         VariablesSaved;
+  UINT8         *OffsetPtr;
+  UINTN         BytesRemaining;
+  UINTN         SizeToSave;
+
+  //
+  // Check input parameters.
+  //
+  if (VariableName == NULL || VariableName[0] == 0 || VendorGuid == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if (DataSize != 0 && Data == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  if (DataSize == 0 && LockVariable) {
+    DEBUG ((DEBUG_ERROR, "SetLargeVariable: Cannot lock a variable that is being deleted\n"));
+    return EFI_INVALID_PARAMETER;
+  }
+
+  VariablesSaved = 0;
+  if (LockVariable && !VarLibIsVariableRequestToLockSupported ()) {
+      Status = EFI_INVALID_PARAMETER;
+      DEBUG ((DEBUG_ERROR, "SetLargeVariable: Variable locking is not currently supported\n"));
+      goto Done;
+  }
+
+  //
+  // Check if the variable is being deleted.
+  //
+  if (DataSize == 0) {
+    DEBUG ((DEBUG_INFO, "SetLargeVariable: Variable is being deleted.\n"));
+    Status = DeleteLargeVariableInternal (VariableName, VendorGuid);
+    goto Done;
+  }
+
+  VariableNameLength  = StrLen (VariableName);
+  VariableSplitSize   = GetVariableSplitSize (VariableNameLength);
+  if (DataSize <= VariableSplitSize) {
+
+    //
+    // A single variable is sufficient to store the data, only create one.
+    //
+    DEBUG ((DEBUG_INFO, "SetLargeVariable: Saving using single variable.\n"));
+    Status = VarLibSetVariable (
+               VariableName,
+               VendorGuid,
+               EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+               DataSize,
+               Data
+               );
+    if (EFI_ERROR (Status)) {
+      goto Done;
+    }
+    if (LockVariable) {
+      Status = VarLibVariableRequestToLock (VariableName, VendorGuid);
+    }
+  } else {
+    //
+    // Multiple variables are needed
+    //
+
+    //
+    // Check the length of the variable name is short enough to allow an integer
+    // to be appended.
+    //
+    if (VariableNameLength >= (MAX_VARIABLE_NAME_SIZE - MAX_VARIABLE_SPLIT_DIGITS)) {
+      Status = EFI_OUT_OF_RESOURCES;
+      DEBUG ((DEBUG_ERROR, "SetLargeVariable: Variable name too long\n"));
+      goto Done;
+    }
+
+    //
+    // Check that it is possible to store the data using less than
+    // MAX_VARIABLE_SPLIT variables
+    //
+    if ((DataSize / (VariableSplitSize - MAX_VARIABLE_SPLIT_DIGITS)) > MAX_VARIABLE_SPLIT) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "SetLargeVariable: More than %d variables are needed to store the data, which exceeds the maximum supported\n",
+        MAX_VARIABLE_SPLIT
+        ));
+      Status = EFI_OUT_OF_RESOURCES;
+      goto Done;
+    }
+
+    //
+    // Check that there is enough space remaining in the UEFI Variable Services
+    // Non-Volatile storage to store the data.
+    //
+    RemainingVariableStorage = GetRemainingVariableStorageSpace ();
+    if (DataSize > RemainingVariableStorage) {
+      DEBUG ((DEBUG_ERROR, "SetLargeVariable: Not enough NV storage space to store the data\n"));
+      Status = EFI_OUT_OF_RESOURCES;
+      goto Done;
+    }
+
+    DEBUG ((DEBUG_INFO, "SetLargeVariable: Saving using multiple variables.\n"));
+    OffsetPtr         = (UINT8 *) Data;
+    BytesRemaining    = DataSize;
+    VariablesSaved    = 0;
+
+    //
+    // Store chunks of data in UEFI variables until all data is stored
+    //
+    for (Index = 0; (Index < MAX_VARIABLE_SPLIT) && (BytesRemaining > 0); Index++) {
+      ZeroMem (TempVariableName, MAX_VARIABLE_NAME_SIZE);
+      UnicodeSPrint (TempVariableName, MAX_VARIABLE_NAME_SIZE, L"%s%d", VariableName, Index);
+
+      SizeToSave          = 0;
+      VariableNameLength  = StrLen (TempVariableName);
+      VariableSplitSize   = GetVariableSplitSize (VariableNameLength);
+      if (VariableSplitSize == 0) {
+        DEBUG ((DEBUG_ERROR, "Unable to save variable, out of NV storage space\n"));
+        Status = EFI_OUT_OF_RESOURCES;
+        goto Done;
+      }
+
+      if (BytesRemaining > VariableSplitSize) {
+        SizeToSave = (UINTN) VariableSplitSize;
+      } else {
+        SizeToSave = BytesRemaining;
+      }
+      DEBUG ((DEBUG_INFO, "Saving %s, Guid = %g, Size %d\n", TempVariableName, VendorGuid, SizeToSave));
+      Status = VarLibSetVariable (
+                TempVariableName,
+                VendorGuid,
+                EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                SizeToSave,
+                (VOID *) OffsetPtr
+                );
+      if (EFI_ERROR (Status)) {
+        DEBUG ((DEBUG_ERROR, "SetLargeVariable: Error writting variable: Status = %r\n", Status));
+        goto Done;
+      }
+      VariablesSaved  = Index;
+      BytesRemaining -= SizeToSave;
+      OffsetPtr += SizeToSave;
+    }   // End of for loop
+
+    //
+    // If the user requested that the variables be locked, lock them now that
+    // all data is saved.
+    //
+    if (LockVariable) {
+      for (Index = 0; Index < VariablesSaved; Index++) {
+        ZeroMem (TempVariableName, MAX_VARIABLE_NAME_SIZE);
+        UnicodeSPrint (TempVariableName, MAX_VARIABLE_NAME_SIZE, L"%s%d", VariableName, Index);
+
+        DEBUG ((DEBUG_INFO, "Locking %s, Guid = %g\n", TempVariableName, VendorGuid));
+        Status = VarLibVariableRequestToLock (TempVariableName, VendorGuid);
+        if (EFI_ERROR (Status)) {
+          DEBUG ((DEBUG_ERROR, "SetLargeVariable: Error locking variable: Status = %r\n", Status));
+          VariablesSaved = 0;
+          goto Done;
+        }
+      }
+    }
+  }
+
+Done:
+  if (EFI_ERROR (Status) && VariablesSaved > 0) {
+    DEBUG ((DEBUG_ERROR, "SetLargeVariable: An error was encountered, deleting variables with partially stored data\n"));
+    for (Index = 0; Index < VariablesSaved; Index++) {
+      ZeroMem (TempVariableName, MAX_VARIABLE_NAME_SIZE);
+      UnicodeSPrint (TempVariableName, MAX_VARIABLE_NAME_SIZE, L"%s%d", VariableName, Index);
+
+      DEBUG ((DEBUG_INFO, "Deleting %s, Guid = %g\n", TempVariableName, VendorGuid));
+      Status2 = VarLibSetVariable (
+                  TempVariableName,
+                  VendorGuid,
+                  EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                  0,
+                  NULL
+                  );
+    DEBUG ((DEBUG_ERROR, "SetLargeVariable: Error deleting variable: Status = %r\n", Status2));
+    }
+  }
+  DEBUG ((DEBUG_ERROR, "SetLargeVariable: Status = %r\n", Status));
+  return Status;
+}
-- 
2.27.0.windows.1