system76-edk2/OvmfPkg/Library/NvVarsFileLib/FsAccess.c

/** @file
  File System Access for NvVarsFileLib

  Copyright (c) 2004 - 2014, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "NvVarsFileLib.h"

#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/MemoryAllocationLib.h>

/**
  Open the NvVars file for reading or writing

  @param[in]  FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance
  @param[in]  ReadingFile - TRUE: open the file for reading.  FALSE: writing
  @param[out] NvVarsFile - If EFI_SUCCESS is returned, then this is updated
                           with the opened NvVars file.

  @return     EFI_SUCCESS if the file was opened

**/
EFI_STATUS
GetNvVarsFile (
  IN  EFI_HANDLE       FsHandle,
  IN  BOOLEAN          ReadingFile,
  OUT EFI_FILE_HANDLE  *NvVarsFile
  )
{
  EFI_STATUS                       Status;
  EFI_SIMPLE_FILE_SYSTEM_PROTOCOL  *Fs;
  EFI_FILE_HANDLE                  Root;

  //
  // Get the FileSystem protocol on that handle
  //
  Status = gBS->HandleProtocol (
                  FsHandle,
                  &gEfiSimpleFileSystemProtocolGuid,
                  (VOID **)&Fs
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Get the volume (the root directory)
  //
  Status = Fs->OpenVolume (Fs, &Root);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Attempt to open the NvVars file in the root directory
  //
  Status = Root->Open (
                   Root,
                   NvVarsFile,
                   L"NvVars",
                   ReadingFile ?
                   EFI_FILE_MODE_READ :
                   (
                    EFI_FILE_MODE_CREATE |
                    EFI_FILE_MODE_READ |
                    EFI_FILE_MODE_WRITE
                   ),
                   0
                   );

  return Status;
}

/**
  Open the NvVars file for reading or writing

  @param[in]  File - The file to inspect
  @param[out] Exists - Returns whether the file exists
  @param[out] Size - Returns the size of the file
                     (0 if the file does not exist)

**/
VOID
NvVarsFileReadCheckup (
  IN  EFI_FILE_HANDLE  File,
  OUT BOOLEAN          *Exists,
  OUT UINTN            *Size
  )
{
  EFI_FILE_INFO  *FileInfo;

  *Exists = FALSE;
  *Size   = 0;

  FileInfo = FileHandleGetInfo (File);
  if (FileInfo == NULL) {
    return;
  }

  if ((FileInfo->Attribute & EFI_FILE_DIRECTORY) != 0) {
    FreePool (FileInfo);
    return;
  }

  *Exists = TRUE;
  *Size   = (UINTN)FileInfo->FileSize;

  FreePool (FileInfo);
}

/**
  Open the NvVars file for reading or writing

  @param[in]  File - The file to inspect
  @param[out] Exists - Returns whether the file exists
  @param[out] Size - Returns the size of the file
                     (0 if the file does not exist)

**/
EFI_STATUS
FileHandleEmpty (
  IN  EFI_FILE_HANDLE  File
  )
{
  EFI_STATUS     Status;
  EFI_FILE_INFO  *FileInfo;

  //
  // Retrieve the FileInfo structure
  //
  FileInfo = FileHandleGetInfo (File);
  if (FileInfo == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If the path is a directory, then return an error
  //
  if ((FileInfo->Attribute & EFI_FILE_DIRECTORY) != 0) {
    FreePool (FileInfo);
    return EFI_INVALID_PARAMETER;
  }

  //
  // If the file size is already 0, then it is empty, so
  // we can return success.
  //
  if (FileInfo->FileSize == 0) {
    FreePool (FileInfo);
    return EFI_SUCCESS;
  }

  //
  // Set the file size to 0.
  //
  FileInfo->FileSize = 0;
  Status             = FileHandleSetInfo (File, FileInfo);

  FreePool (FileInfo);

  return Status;
}

/**
  Reads a file to a newly allocated buffer

  @param[in]  File - The file to read
  @param[in]  ReadSize - The size of data to read from the file

  @return     Pointer to buffer allocated to hold the file
              contents.  NULL if an error occurred.

**/
VOID *
FileHandleReadToNewBuffer (
  IN EFI_FILE_HANDLE  FileHandle,
  IN UINTN            ReadSize
  )
{
  EFI_STATUS  Status;
  UINTN       ActualReadSize;
  VOID        *FileContents;

  ActualReadSize = ReadSize;
  FileContents   = AllocatePool (ReadSize);
  if (FileContents != NULL) {
    Status = FileHandleRead (
               FileHandle,
               &ReadSize,
               FileContents
               );
    if (EFI_ERROR (Status) || (ActualReadSize != ReadSize)) {
      FreePool (FileContents);
      return NULL;
    }
  }

  return FileContents;
}

/**
  Reads the contents of the NvVars file on the file system

  @param[in]  FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance

  @return     EFI_STATUS based on the success or failure of the file read

**/
EFI_STATUS
ReadNvVarsFile (
  IN  EFI_HANDLE  FsHandle
  )
{
  EFI_STATUS       Status;
  EFI_FILE_HANDLE  File;
  UINTN            FileSize;
  BOOLEAN          FileExists;
  VOID             *FileContents;
  EFI_HANDLE       SerializedVariables;

  Status = GetNvVarsFile (FsHandle, TRUE, &File);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_INFO, "FsAccess.c: Could not open NV Variables file on this file system\n"));
    return Status;
  }

  NvVarsFileReadCheckup (File, &FileExists, &FileSize);
  if (FileSize == 0) {
    FileHandleClose (File);
    return EFI_UNSUPPORTED;
  }

  FileContents = FileHandleReadToNewBuffer (File, FileSize);
  if (FileContents == NULL) {
    FileHandleClose (File);
    return EFI_UNSUPPORTED;
  }

  DEBUG ((
    DEBUG_INFO,
    "FsAccess.c: Read %Lu bytes from NV Variables file\n",
    (UINT64)FileSize
    ));

  Status = SerializeVariablesNewInstanceFromBuffer (
             &SerializedVariables,
             FileContents,
             FileSize
             );
  if (!RETURN_ERROR (Status)) {
    Status = SerializeVariablesSetSerializedVariables (SerializedVariables);
  }

  FreePool (FileContents);
  FileHandleClose (File);

  return Status;
}

/**
  Writes a variable to indicate that the NV variables
  have been loaded from the file system.

**/
STATIC
VOID
SetNvVarsVariable (
  VOID
  )
{
  BOOLEAN  VarData;
  UINTN    Size;

  //
  // Write a variable to indicate we've already loaded the
  // variable data.  If it is found, we skip the loading on
  // subsequent attempts.
  //
  Size    = sizeof (VarData);
  VarData = TRUE;
  gRT->SetVariable (
         L"NvVars",
         &gEfiSimpleFileSystemProtocolGuid,
         EFI_VARIABLE_NON_VOLATILE |
         EFI_VARIABLE_BOOTSERVICE_ACCESS |
         EFI_VARIABLE_RUNTIME_ACCESS,
         Size,
         (VOID *)&VarData
         );
}

/**
  Loads the non-volatile variables from the NvVars file on the
  given file system.

  @param[in]  FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance

  @return     EFI_STATUS based on the success or failure of load operation

**/
EFI_STATUS
LoadNvVarsFromFs (
  EFI_HANDLE  FsHandle
  )
{
  EFI_STATUS  Status;
  BOOLEAN     VarData;
  UINTN       Size;

  DEBUG ((DEBUG_INFO, "FsAccess.c: LoadNvVarsFromFs\n"));

  //
  // We write a variable to indicate we've already loaded the
  // variable data.  If it is found, we skip the loading.
  //
  // This is relevant if the non-volatile variable have been
  // able to survive a reboot operation.  In that case, we don't
  // want to re-load the file as it would overwrite newer changes
  // made to the variables.
  //
  Size    = sizeof (VarData);
  VarData = TRUE;
  Status  = gRT->GetVariable (
                   L"NvVars",
                   &gEfiSimpleFileSystemProtocolGuid,
                   NULL,
                   &Size,
                   (VOID *)&VarData
                   );
  if (Status == EFI_SUCCESS) {
    DEBUG ((DEBUG_INFO, "NV Variables were already loaded\n"));
    return EFI_ALREADY_STARTED;
  }

  //
  // Attempt to restore the variables from the NvVars file.
  //
  Status = ReadNvVarsFile (FsHandle);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_INFO, "Error while restoring NV variable data\n"));
    return Status;
  }

  //
  // Write a variable to indicate we've already loaded the
  // variable data.  If it is found, we skip the loading on
  // subsequent attempts.
  //
  SetNvVarsVariable ();

  DEBUG ((
    DEBUG_INFO,
    "FsAccess.c: Read NV Variables file (size=%Lu)\n",
    (UINT64)Size
    ));

  return Status;
}

STATIC
RETURN_STATUS
EFIAPI
IterateVariablesCallbackAddAllNvVariables (
  IN  VOID      *Context,
  IN  CHAR16    *VariableName,
  IN  EFI_GUID  *VendorGuid,
  IN  UINT32    Attributes,
  IN  UINTN     DataSize,
  IN  VOID      *Data
  )
{
  EFI_HANDLE  Instance;

  Instance = (EFI_HANDLE)Context;

  //
  // Only save non-volatile variables
  //
  if ((Attributes & EFI_VARIABLE_NON_VOLATILE) == 0) {
    return RETURN_SUCCESS;
  }

  return SerializeVariablesAddVariable (
           Instance,
           VariableName,
           VendorGuid,
           Attributes,
           DataSize,
           Data
           );
}

/**
  Saves the non-volatile variables into the NvVars file on the
  given file system.

  @param[in]  FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance

  @return     EFI_STATUS based on the success or failure of load operation

**/
EFI_STATUS
SaveNvVarsToFs (
  EFI_HANDLE  FsHandle
  )
{
  EFI_STATUS       Status;
  EFI_FILE_HANDLE  File;
  UINTN            WriteSize;
  UINTN            VariableDataSize;
  VOID             *VariableData;
  EFI_HANDLE       SerializedVariables;

  SerializedVariables = NULL;

  Status = SerializeVariablesNewInstance (&SerializedVariables);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = SerializeVariablesIterateSystemVariables (
             IterateVariablesCallbackAddAllNvVariables,
             (VOID *)SerializedVariables
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  VariableData     = NULL;
  VariableDataSize = 0;
  Status           = SerializeVariablesToBuffer (
                       SerializedVariables,
                       NULL,
                       &VariableDataSize
                       );
  if (Status == RETURN_BUFFER_TOO_SMALL) {
    VariableData = AllocatePool (VariableDataSize);
    if (VariableData == NULL) {
      Status = EFI_OUT_OF_RESOURCES;
    } else {
      Status = SerializeVariablesToBuffer (
                 SerializedVariables,
                 VariableData,
                 &VariableDataSize
                 );
    }
  }

  SerializeVariablesFreeInstance (SerializedVariables);

  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Open the NvVars file for writing.
  //
  Status = GetNvVarsFile (FsHandle, FALSE, &File);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_INFO, "FsAccess.c: Unable to open file to saved NV Variables\n"));
    return Status;
  }

  //
  // Empty the starting file contents.
  //
  Status = FileHandleEmpty (File);
  if (EFI_ERROR (Status)) {
    FileHandleClose (File);
    return Status;
  }

  WriteSize = VariableDataSize;
  Status    = FileHandleWrite (File, &WriteSize, VariableData);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  FileHandleClose (File);

  if (!EFI_ERROR (Status)) {
    //
    // Write a variable to indicate we've already loaded the
    // variable data.  If it is found, we skip the loading on
    // subsequent attempts.
    //
    SetNvVarsVariable ();

    DEBUG ((DEBUG_INFO, "Saved NV Variables to NvVars file\n"));
  }

  return Status;
}