system76-edk2/MdeModulePkg/Core/Dxe/FwVol/Ffs.c

/** @file
  FFS file access utilities.

Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "DxeMain.h"
#include "FwVolDriver.h"

/**
  Get the FFS file state by checking the highest bit set in the header's state field.

  @param  ErasePolarity  Erase polarity attribute of the firmware volume
  @param  FfsHeader      Points to the FFS file header

  @return FFS File state

**/
EFI_FFS_FILE_STATE
GetFileState (
  IN UINT8                ErasePolarity,
  IN EFI_FFS_FILE_HEADER  *FfsHeader
  )
{
  EFI_FFS_FILE_STATE  FileState;
  UINT8               HighestBit;

  FileState = FfsHeader->State;

  if (ErasePolarity != 0) {
    FileState = (EFI_FFS_FILE_STATE) ~FileState;
  }

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

  return (EFI_FFS_FILE_STATE)HighestBit;
}

/**
  Check if a block of buffer is erased.

  @param  ErasePolarity  Erase polarity attribute of the firmware volume
  @param  InBuffer       The buffer to be checked
  @param  BufferSize     Size of the buffer in bytes

  @retval TRUE           The block of buffer is erased
  @retval FALSE          The block of buffer is not erased

**/
BOOLEAN
IsBufferErased (
  IN UINT8  ErasePolarity,
  IN VOID   *InBuffer,
  IN UINTN  BufferSize
  )
{
  UINTN  Count;
  UINT8  EraseByte;
  UINT8  *Buffer;

  if (ErasePolarity == 1) {
    EraseByte = 0xFF;
  } else {
    EraseByte = 0;
  }

  Buffer = InBuffer;
  for (Count = 0; Count < BufferSize; Count++) {
    if (Buffer[Count] != EraseByte) {
      return FALSE;
    }
  }

  return TRUE;
}

/**
  Verify checksum of the firmware volume header.

  @param  FvHeader       Points to the firmware volume header to be checked

  @retval TRUE           Checksum verification passed
  @retval FALSE          Checksum verification failed

**/
BOOLEAN
VerifyFvHeaderChecksum (
  IN EFI_FIRMWARE_VOLUME_HEADER  *FvHeader
  )
{
  UINT16  Checksum;

  Checksum = CalculateSum16 ((UINT16 *)FvHeader, FvHeader->HeaderLength);

  if (Checksum == 0) {
    return TRUE;
  } else {
    return FALSE;
  }
}

/**
  Verify checksum of the FFS file header.

  @param  FfsHeader      Points to the FFS file header to be checked

  @retval TRUE           Checksum verification passed
  @retval FALSE          Checksum verification failed

**/
BOOLEAN
VerifyHeaderChecksum (
  IN EFI_FFS_FILE_HEADER  *FfsHeader
  )
{
  UINT8  HeaderChecksum;

  if (IS_FFS_FILE2 (FfsHeader)) {
    HeaderChecksum = CalculateSum8 ((UINT8 *)FfsHeader, sizeof (EFI_FFS_FILE_HEADER2));
  } else {
    HeaderChecksum = CalculateSum8 ((UINT8 *)FfsHeader, sizeof (EFI_FFS_FILE_HEADER));
  }

  HeaderChecksum = (UINT8)(HeaderChecksum - FfsHeader->State - FfsHeader->IntegrityCheck.Checksum.File);

  if (HeaderChecksum == 0) {
    return TRUE;
  } else {
    return FALSE;
  }
}

/**
  Check if it's a valid FFS file header.

  @param  ErasePolarity  Erase polarity attribute of the firmware volume
  @param  FfsHeader      Points to the FFS file header to be checked
  @param  FileState      FFS file state to be returned

  @retval TRUE           Valid FFS file header
  @retval FALSE          Invalid FFS file header

**/
BOOLEAN
IsValidFfsHeader (
  IN UINT8                ErasePolarity,
  IN EFI_FFS_FILE_HEADER  *FfsHeader,
  OUT EFI_FFS_FILE_STATE  *FileState
  )
{
  *FileState = GetFileState (ErasePolarity, FfsHeader);

  switch (*FileState) {
    case EFI_FILE_HEADER_VALID:
    case EFI_FILE_DATA_VALID:
    case EFI_FILE_MARKED_FOR_UPDATE:
    case EFI_FILE_DELETED:
      //
      // Here we need to verify header checksum
      //
      return VerifyHeaderChecksum (FfsHeader);

    case EFI_FILE_HEADER_CONSTRUCTION:
    case EFI_FILE_HEADER_INVALID:
    default:
      return FALSE;
  }
}

/**
  Check if it's a valid FFS file.
  Here we are sure that it has a valid FFS file header since we must call IsValidFfsHeader() first.

  @param  ErasePolarity  Erase polarity attribute of the firmware volume
  @param  FfsHeader      Points to the FFS file to be checked

  @retval TRUE           Valid FFS file
  @retval FALSE          Invalid FFS file

**/
BOOLEAN
IsValidFfsFile (
  IN UINT8                ErasePolarity,
  IN EFI_FFS_FILE_HEADER  *FfsHeader
  )
{
  EFI_FFS_FILE_STATE  FileState;
  UINT8               DataCheckSum;

  FileState = GetFileState (ErasePolarity, FfsHeader);
  switch (FileState) {
    case EFI_FILE_DELETED:
    case EFI_FILE_DATA_VALID:
    case EFI_FILE_MARKED_FOR_UPDATE:
      DataCheckSum = FFS_FIXED_CHECKSUM;
      if ((FfsHeader->Attributes & FFS_ATTRIB_CHECKSUM) == FFS_ATTRIB_CHECKSUM) {
        if (IS_FFS_FILE2 (FfsHeader)) {
          DataCheckSum = CalculateCheckSum8 ((CONST UINT8 *)FfsHeader + sizeof (EFI_FFS_FILE_HEADER2), FFS_FILE2_SIZE (FfsHeader) - sizeof (EFI_FFS_FILE_HEADER2));
        } else {
          DataCheckSum = CalculateCheckSum8 ((CONST UINT8 *)FfsHeader + sizeof (EFI_FFS_FILE_HEADER), FFS_FILE_SIZE (FfsHeader) - sizeof (EFI_FFS_FILE_HEADER));
        }
      }

      if (FfsHeader->IntegrityCheck.Checksum.File == DataCheckSum) {
        return TRUE;
      }

    default:
      return FALSE;
  }
}