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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** FileX Component */
/** */
/** Utility */
/** */
/**************************************************************************/
/**************************************************************************/
#define FX_SOURCE_CODE
/* Include necessary system files. */
#include "fx_api.h"
#ifdef FX_ENABLE_EXFAT
#include "fx_system.h"
#include "fx_media.h"
#include "fx_utility.h"
#include "fx_directory_exFAT.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _fx_utility_exFAT_geometry_check PORTABLE C */
/* 6.1.10 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function checks exFAT geometry. */
/* */
/* INPUT */
/* */
/* media_ptr Media control block pointer */
/* sector_buffer Pointer to sector buffer */
/* */
/* OUTPUT */
/* */
/* return status */
/* */
/* CALLS */
/* */
/* _fx_exFAT_system_area_checksum_verify Verify SystemArea checksum */
/* _fx_utility_64_unsigned_read Read ULONG64 from memory */
/* */
/* CALLED BY */
/* */
/* FileX System Functions */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 William E. Lamie Modified comment(s), */
/* resulting in version 6.1 */
/* 01-31-2022 Bhupendra Naphade Modified comment(s), replaced */
/* sector size constant, */
/* resulting in version 6.1.10 */
/* */
/**************************************************************************/
UINT _fx_utility_exFAT_geometry_check(FX_MEDIA *media_ptr, UCHAR *sector_buffer)
{
ULONG temp;
ULONG counter;
ULONG calculated_checksum = 0;
ULONG main_system_area_checksum = 0;
ULONG backup_system_area_checksum = 0;
ULONG bitmap_start_sector = 0;
ULONG bitmap_size_in_bytes = 0;
ULONG upcase_table_start_sector = 0;
ULONG upcase_table_size_in_bytes = 0;
ULONG upcase_table_checksum = 0;
UCHAR *dir_entry_ptr = NULL;
ULONG dir_entries_found = 0;
UINT status;
/* Check FAT Size. */
temp = (media_ptr -> fx_media_sectors_per_FAT <<
media_ptr -> fx_media_exfat_bytes_per_sector_shift) >>
FX_EXFAT_SIZE_OF_FAT_ELEMENT_SHIFT;
/* Is the FAT capable of holding the total number of clusters? */
if (temp < media_ptr -> fx_media_total_clusters)
{
/* No, return error. */
return(FX_MEDIA_INVALID);
}
/* Check Cluster Heap Offset. */
temp = media_ptr -> fx_media_reserved_sectors +
media_ptr -> fx_media_sectors_per_FAT;
/* Is the cluster heap placed after the FAT table? */
if (temp > media_ptr -> fx_media_data_sector_start)
{
/* No, the media is invalid. */
return(FX_MEDIA_INVALID);
}
/* Check System Area checksum. */
status = _fx_utility_exFAT_system_area_checksum_verify(media_ptr,
sector_buffer,
FX_EXFAT_FAT_MAIN_BOOT_SECTOR_OFFSET,
&main_system_area_checksum);
/* Is the checksum correct? */
if (FX_SUCCESS != status)
{
/* No, return error. */
return(status);
}
/* Check System Area checksum in backup region. */
status = _fx_utility_exFAT_system_area_checksum_verify(media_ptr,
sector_buffer,
FX_EXFAT_FAT_BACKUP_BOOT_SECTOR_OFFSET,
&backup_system_area_checksum);
/* Is the checksum correct? */
if (FX_SUCCESS != status)
{
/* No, return error. */
return(status);
}
/* Is the main system area checksum equals to the backup system area checksum? */
if (main_system_area_checksum != backup_system_area_checksum)
{
/* No, return error. */
return(FX_MEDIA_INVALID);
}
/* Get Bit Map and Up Case table parameters. */
media_ptr -> fx_media_driver_request = FX_DRIVER_READ;
media_ptr -> fx_media_driver_buffer = sector_buffer;
media_ptr -> fx_media_driver_sectors = 1;
counter = 0;
/* Go through the first cluster of exFAT root directory.
This cluster should contain BitMap allocation Dir Entry
and Up Case table Dir Entry. */
while ((counter < media_ptr -> fx_media_sectors_per_cluster) &&
(EXFAT_NUM_OF_DIR_ENTRIES != dir_entries_found))
{
/* Build the read sector command. */
media_ptr -> fx_media_driver_logical_sector = media_ptr -> fx_media_root_sector_start + counter;
media_ptr -> fx_media_driver_status = FX_IO_ERROR;
/* Invoke the driver to read the directory entry sector. */
(media_ptr -> fx_media_driver_entry)(media_ptr);
/* Determine if the read was successful. */
if (FX_SUCCESS != media_ptr -> fx_media_driver_status)
{
/* Return the error status. */
return(media_ptr -> fx_media_driver_status);
}
/* Move to next sector. */
counter++;
/* Setup directory entry pointer to the sector buffer. */
dir_entry_ptr = sector_buffer;
/* Go through the read buffer and try to find BitMap table and UpCase table dir entries. */
while (dir_entry_ptr < (media_ptr -> fx_media_memory_buffer +
media_ptr -> fx_media_bytes_per_sector) &&
(EXFAT_NUM_OF_DIR_ENTRIES != dir_entries_found))
{
/* Check if we found the bitmap table. */
if (FX_EXFAT_DIR_ENTRY_TYPE_ALLOCATION_BITMAP == dir_entry_ptr[FX_EXFAT_ENTRY_TYPE])
{
/* Calculate BitMap table start sector. */
bitmap_start_sector = media_ptr -> fx_media_data_sector_start +
((_fx_utility_32_unsigned_read(&dir_entry_ptr[FX_EXFAT_FIRST_CLUSTER]) -
FX_FAT_ENTRY_START) << media_ptr -> fx_media_exfat_sector_per_clusters_shift);
bitmap_size_in_bytes = (ULONG)_fx_utility_64_unsigned_read(&dir_entry_ptr[FX_EXFAT_DATA_LENGTH]);
dir_entries_found++;
}
/* Check if we found the upcase table. */
else if (FX_EXFAT_DIR_ENTRY_TYPE_UP_CASE_TABLE == dir_entry_ptr[FX_EXFAT_ENTRY_TYPE])
{
/* Calculate UpCase table start sector. */
upcase_table_start_sector = media_ptr -> fx_media_data_sector_start +
((_fx_utility_32_unsigned_read(&dir_entry_ptr[FX_EXFAT_FIRST_CLUSTER]) -
FX_FAT_ENTRY_START) << media_ptr -> fx_media_exfat_sector_per_clusters_shift);
upcase_table_checksum = _fx_utility_32_unsigned_read(&dir_entry_ptr[FX_EXFAT_UP_CASE_TABLE_CHECK_SUM]);
upcase_table_size_in_bytes = (ULONG)_fx_utility_64_unsigned_read(&dir_entry_ptr[FX_EXFAT_DATA_LENGTH]);
dir_entries_found++;
}
/* Move to next directory entry. */
dir_entry_ptr += FX_EXFAT_DIR_ENTRY_SIZE;
}
}
/* Validate the directory entries. */
if ((0 == bitmap_start_sector) ||
(0 == bitmap_size_in_bytes) ||
(0 == upcase_table_start_sector) ||
(0 == upcase_table_checksum) ||
(0 == upcase_table_size_in_bytes))
{
/* Directory entries have invalid value, return error. */
return(FX_MEDIA_INVALID);
}
/* Check Bit Map size. */
if (media_ptr -> fx_media_total_clusters >
/* 1 Byte = > map to 8 clusters. */
(bitmap_size_in_bytes << BITS_PER_BYTE_SHIFT))
{
/* Bitmap size is not correct, return error. */
return(FX_MEDIA_INVALID);
}
/* Check Up Case Table checksum. */
calculated_checksum = 0;
/* Build driver request to read the upcase table. */
media_ptr -> fx_media_driver_logical_sector = upcase_table_start_sector;
/* Loop to calculate upcase table checksum. */
while (upcase_table_size_in_bytes > 0)
{
/* Build driver request. */
media_ptr -> fx_media_driver_status = FX_IO_ERROR;
/* Invoke the driver to read one sector. */
(media_ptr -> fx_media_driver_entry)(media_ptr);
/* Determine if the read was successful. */
if (FX_SUCCESS != media_ptr -> fx_media_driver_status)
{
/* Return the error status. */
return(media_ptr -> fx_media_driver_status);
}
/* Determine the processing size. */
if (upcase_table_size_in_bytes >= media_ptr -> fx_media_bytes_per_sector)
{
/* Process one sector at a time. */
temp = media_ptr -> fx_media_bytes_per_sector;
upcase_table_size_in_bytes -= media_ptr -> fx_media_bytes_per_sector;
media_ptr -> fx_media_driver_logical_sector++;
}
else
{
/* Remaining data is less than one sector, process all the remaining bytes. */
temp = upcase_table_size_in_bytes;
upcase_table_size_in_bytes = 0;
}
/* Calculate checksum. */
for (counter = 0; counter < temp; counter++)
{
/* Calculate the checksum using the algorithm specified in the specification. */
/* Right rotate the checksum by one bit position and add the data. */
calculated_checksum = ((calculated_checksum >> 1) | (calculated_checksum << 31)) + (ULONG)sector_buffer[counter];
}
}
/* Verify the checksum. */
if (calculated_checksum != upcase_table_checksum)
{
/* Checksum not correct, return error. */
return(FX_MEDIA_INVALID);
}
/* Return success. */
return(FX_SUCCESS);
}
#endif /* FX_ENABLE_EXFAT */
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