fvlib.c

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EFI_STATUS
GetSectionByType (
  IN EFI_FFS_FILE_HEADER          *File,
  IN EFI_SECTION_TYPE             SectionType,
  IN UINTN                        Instance,
  OUT EFI_FILE_SECTION_POINTER    *Section
  )
/*++

Routine Description:

  Find a section in a file by type and instance.  An instance of 1 is the first 
  instance.  The function will return NULL if a matching section cannot be found.
  The function will not handle encapsulating sections.

Arguments:

  File        The file to search.
  SectionType Type of file to search for.
  Instance    Instace of the section to return.
  Section     Return pointer.  In the case of an error, contents are undefined.

Returns:

  EFI_SUCCESS             The function completed successfully.
  EFI_ABORTED             An error was encountered.
  EFI_INVALID_PARAMETER   One of the parameters was NULL.
  EFI_NOT_FOUND           No found.
--*/
{
  EFI_FILE_SECTION_POINTER  CurrentSection;
  EFI_STATUS                Status;
  UINTN                     SectionCount;

  //
  // Verify input parameters
  //
  if (File == NULL || Instance == 0) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // Verify FFS header
  //
  Status = VerifyFfsFile (File);
  if (EFI_ERROR (Status)) {
    Error (NULL, 0, 0, "invalid FFS file", NULL);
    return EFI_ABORTED;
  }
  //
  // Initialize the number of matching sections found.
  //
  SectionCount = 0;

  //
  // Get the first section
  //
  CurrentSection.CommonHeader = (EFI_COMMON_SECTION_HEADER *) ((UINTN) File + sizeof (EFI_FFS_FILE_HEADER));

  //
  // Loop as long as we have a valid file
  //
  while ((UINTN) CurrentSection.CommonHeader < (UINTN) File + GetLength (File->Size)) {
    if (CurrentSection.CommonHeader->Type == SectionType) {
      SectionCount++;
    }

    if (SectionCount == Instance) {
      *Section = CurrentSection;
      return EFI_SUCCESS;
    }
    //
    // Find next section (including compensating for alignment issues.
    //
    CurrentSection.CommonHeader = (EFI_COMMON_SECTION_HEADER *) ((((UINTN) CurrentSection.CommonHeader) + GetLength (CurrentSection.CommonHeader->Size) + 0x03) & (-1 << 2));
  }
  //
  // Section not found
  //
  (*Section).Code16Section = NULL;
  return EFI_NOT_FOUND;
}
//
// will not parse compressed sections
//
EFI_STATUS
VerifyFv (
  IN EFI_FIRMWARE_VOLUME_HEADER   *FvHeader
  )
/*++

Routine Description:

  Verify the current pointer points to a valid FV header.

Arguments:

  FvHeader     Pointer to an alleged FV file.

Returns:

  EFI_SUCCESS             The FV header is valid.
  EFI_VOLUME_CORRUPTED    The FV header is not valid.
  EFI_INVALID_PARAMETER   A required parameter was NULL.
  EFI_ABORTED             Operation aborted.

--*/
{
  UINT16  Checksum;

  //
  // Verify input parameters
  //
  if (FvHeader == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  if (FvHeader->Signature != EFI_FVH_SIGNATURE) {
    Error (NULL, 0, 0, "invalid FV header signature", NULL);
    return EFI_VOLUME_CORRUPTED;
  }
  //
  // Verify header checksum
  //
  Checksum = CalculateSum16 ((UINT16 *) FvHeader, FvHeader->HeaderLength / sizeof (UINT16));

  if (Checksum != 0) {
    Error (NULL, 0, 0, "invalid FV header checksum", NULL);
    return EFI_ABORTED;
  }

  return EFI_SUCCESS;
}

EFI_STATUS
VerifyFfsFile (
  IN EFI_FFS_FILE_HEADER  *FfsHeader
  )
/*++

Routine Description:

  Verify the current pointer points to a FFS file header.

Arguments:

  FfsHeader     Pointer to an alleged FFS file.

Returns:

  EFI_SUCCESS           The Ffs header is valid.
  EFI_NOT_FOUND         This "file" is the beginning of free space.
  EFI_VOLUME_CORRUPTED  The Ffs header is not valid.
  EFI_ABORTED           The erase polarity is not known.

--*/
{
  BOOLEAN             ErasePolarity;
  EFI_STATUS          Status;
  EFI_FFS_FILE_HEADER BlankHeader;
  UINT8               Checksum;
  UINT32              FileLength;
  UINT32              OccupiedFileLength;
  EFI_FFS_FILE_TAIL   *Tail;
  UINT8               SavedChecksum;
  UINT8               SavedState;
  UINT8               FileGuidString[80];
  UINT32              TailSize;
  //
  // Verify library has been initialized.
  //
  if (mFvHeader == NULL || mFvLength == 0) {
    return EFI_ABORTED;
  }
  //
  // Verify FV header
  //
  Status = VerifyFv (mFvHeader);
  if (EFI_ERROR (Status)) {
    return EFI_ABORTED;
  }
  //
  // Get the erase polarity.
  //
  Status = GetErasePolarity (&ErasePolarity);
  if (EFI_ERROR (Status)) {
    return EFI_ABORTED;
  }
  //
  // Check if we have free space
  //
  if (ErasePolarity) {
    memset (&BlankHeader, -1, sizeof (EFI_FFS_FILE_HEADER));
  } else {
    memset (&BlankHeader, 0, sizeof (EFI_FFS_FILE_HEADER));
  }

  if (memcmp (&BlankHeader, FfsHeader, sizeof (EFI_FFS_FILE_HEADER)) == 0) {
    return EFI_NOT_FOUND;
  }
  //
  // Convert the GUID to a string so we can at least report which file
  // if we find an error.
  //
  PrintGuidToBuffer (&FfsHeader->Name, FileGuidString, sizeof (FileGuidString), TRUE);
  if (FfsHeader->Attributes & FFS_ATTRIB_TAIL_PRESENT) {
    TailSize = sizeof (EFI_FFS_FILE_TAIL);
  } else {
    TailSize = 0;
  }
  //
  // Verify file header checksum
  //
  SavedState = FfsHeader->State;
  FfsHeader->State = 0;
  SavedChecksum = FfsHeader->IntegrityCheck.Checksum.File;
  FfsHeader->IntegrityCheck.Checksum.File = 0;
  Checksum = CalculateSum8 ((UINT8 *) FfsHeader, sizeof (EFI_FFS_FILE_HEADER));
  FfsHeader->State = SavedState;
  FfsHeader->IntegrityCheck.Checksum.File = SavedChecksum;
  if (Checksum != 0) {
    Error (NULL, 0, 0, FileGuidString, "invalid FFS file header checksum");
    return EFI_ABORTED;
  }
  //
  // Verify file checksum
  //
  if (FfsHeader->Attributes & FFS_ATTRIB_CHECKSUM) {
    //
    // Verify file data checksum
    //
    FileLength          = GetLength (FfsHeader->Size);
    OccupiedFileLength  = (FileLength + 0x07) & (-1 << 3);
    Checksum            = CalculateSum8 ((UINT8 *) FfsHeader, FileLength - TailSize);
    Checksum            = (UINT8) (Checksum - FfsHeader->State);
    if (Checksum != 0) {
      Error (NULL, 0, 0, FileGuidString, "invalid FFS file checksum");
      return EFI_ABORTED;
    }
  } else {
    //
    // File does not have a checksum
    // Verify contents are 0x5A as spec'd
    //
    if (FfsHeader->IntegrityCheck.Checksum.File != FFS_FIXED_CHECKSUM) {
      Error (NULL, 0, 0, FileGuidString, "invalid fixed FFS file header checksum");
      return EFI_ABORTED;
    }
  }
  //
  // Check if the tail is present and verify it if it is.
  //
  if (FfsHeader->Attributes & FFS_ATTRIB_TAIL_PRESENT) {
    //
    // Verify tail is complement of integrity check field in the header.
    //
    Tail = (EFI_FFS_FILE_TAIL *) ((UINTN) FfsHeader + GetLength (FfsHeader->Size) - sizeof (EFI_FFS_FILE_TAIL));
    if (FfsHeader->IntegrityCheck.TailReference != (EFI_FFS_FILE_TAIL)~(*Tail)) {
      Error (NULL, 0, 0, FileGuidString, "invalid FFS file tail");
      return EFI_ABORTED;
    }
  }

  return EFI_SUCCESS;
}

UINT32
GetLength (
  UINT8     *ThreeByteLength
  )
/*++

Routine Description:

  Converts a three byte length value into a UINT32.

Arguments:

  ThreeByteLength   Pointer to the first of the 3 byte length.

Returns:

  UINT32      Size of the section

--*/
{
  UINT32  Length;

  if (ThreeByteLength == NULL) {
    return 0;
  }

  Length  = *((UINT32 *) ThreeByteLength);
  Length  = Length & 0x00FFFFFF;

  return Length;
}

EFI_STATUS
GetErasePolarity (
  OUT BOOLEAN   *ErasePolarity
  )
/*++

Routine Description:

  This function returns with the FV erase polarity.  If the erase polarity
  for a bit is 1, the function return TRUE.

Arguments:

  ErasePolarity   A pointer to the erase polarity.

Returns:

  EFI_SUCCESS              The function completed successfully.
  EFI_INVALID_PARAMETER    One of the input parameters was invalid.
  EFI_ABORTED              Operation aborted.
  
--*/
{
  EFI_STATUS  Status;

  //
  // Verify library has been initialized.
  //
  if (mFvHeader == NULL || mFvLength == 0) {
    return EFI_ABORTED;
  }
  //
  // Verify FV header
  //
  Status = VerifyFv (mFvHeader);
  if (EFI_ERROR (Status)) {
    return EFI_ABORTED;
  }
  //
  // Verify input parameters.
  //
  if (ErasePolarity == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  if (mFvHeader->Attributes & EFI_FVB_ERASE_POLARITY) {
    *ErasePolarity = TRUE;
  } else {
    *ErasePolarity = FALSE;
  }

  return EFI_SUCCESS;
}

UINT8
GetFileState (
  IN BOOLEAN              ErasePolarity,
  IN EFI_FFS_FILE_HEADER  *FfsHeader
  )
/*++

Routine Description:

  This function returns a the highest state bit in the FFS that is set.
  It in no way validate the FFS file.

Arguments:
  
  ErasePolarity The erase polarity for the file state bits.
  FfsHeader     Pointer to a FFS file.

Returns:

  UINT8   The hightest set state of the file.

--*/
{
  UINT8 FileState;
  UINT8 HighestBit;

  FileState = FfsHeader->State;

  if (ErasePolarity) {
    FileState = (UINT8)~FileState;
  }

  HighestBit = 0x80;
  while (HighestBit != 0 && (HighestBit & FileState) == 0) {
    HighestBit >>= 1;
  }

  return HighestBit;
}