FsAccess.c

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#include "NvVarsFileLib.h"
 
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/MemoryAllocationLib.h>
 
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;
}
 
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);
}
 
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;
}
 
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;
}
 
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;
}
 
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
         );
}
 
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
           );
}
 
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;
}