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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_system_area_checksum_verify 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 */
/* boot_sector_offset Offset of boot sector */
/* calculated_checksum Pointer to checksum value */
/* */
/* OUTPUT */
/* */
/* return status */
/* */
/* CALLS */
/* */
/* Media driver */
/* */
/* 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_system_area_checksum_verify(FX_MEDIA *media_ptr, UCHAR *sector_buffer,
ULONG boot_sector_offset, ULONG *calculated_checksum)
{
ULONG temp;
ULONG counter;
/* Clear the checksum for checksum calculation. */
*calculated_checksum = 0;
/* Prepare driver request. */
media_ptr -> fx_media_driver_request = FX_DRIVER_READ;
media_ptr -> fx_media_driver_buffer = sector_buffer;
media_ptr -> fx_media_driver_sectors = 1;
media_ptr -> fx_media_driver_status = FX_IO_ERROR;
media_ptr -> fx_media_driver_logical_sector = boot_sector_offset;
/* Call driver. */
(media_ptr -> fx_media_driver_entry)(media_ptr);
/* Check driver status. */
if (FX_SUCCESS != media_ptr -> fx_media_driver_status)
{
/* Error, return error status. */
return(media_ptr -> fx_media_driver_status);
}
/* Loop to calculate Boot Sector checksum. */
for (temp = 0; temp < media_ptr -> fx_media_bytes_per_sector; temp++)
{
/* Check if it is VolumeFlags or PercentInUse. */
if ((FX_EF_VOLUME_FLAGS == temp) ||
(FX_EF_VOLUME_FLAGS + 1 == temp) ||
(FX_EF_PERCENT_IN_USE == temp))
{
/* Skip these fields in checksum calculation. */
continue;
}
/* 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[temp];
}
/* Map to Extended boot Sector. */
media_ptr -> fx_media_driver_logical_sector++;
/* Read System Area from Extended Boot Sector
and calculate checksum. */
for (temp = FX_EXFAT_FAT_EXT_BOOT_SECTOR_OFFSET; FX_EXFAT_FAT_CHECK_SUM_OFFSET > temp; temp++)
{
/* Build driver request. */
media_ptr -> fx_media_driver_status = FX_IO_ERROR;
/* Read next sector. */
(media_ptr -> fx_media_driver_entry)(media_ptr);
/* Check status. */
if (FX_SUCCESS != media_ptr -> fx_media_driver_status)
{
/* Clear checksum. */
*calculated_checksum = 0;
/* Error, return error status. */
return(media_ptr -> fx_media_driver_status);
}
/* Move to next logical sector. */
media_ptr -> fx_media_driver_logical_sector++;
/* Check Sector Signature. */
if (((sector_buffer[media_ptr -> fx_media_bytes_per_sector - 2] != FX_SIG_BYTE_1) ||
(sector_buffer[media_ptr -> fx_media_bytes_per_sector - 1] != FX_SIG_BYTE_2)) &&
(FX_EXFAT_FAT_OEM_PARAM_OFFSET > temp))
{
/* Clear checksum. */
*calculated_checksum = 0;
/* Error, return error status. */
return(FX_MEDIA_INVALID);
}
/* Loop to calculate the checksum. */
for (counter = 0; counter < media_ptr -> fx_media_bytes_per_sector; 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];
}
}
/* Build driver request. */
media_ptr -> fx_media_driver_status = FX_IO_ERROR;
/* Read stored checksum. */
(media_ptr -> fx_media_driver_entry)(media_ptr);
/* Determine if the read was successful. */
if (FX_SUCCESS != media_ptr -> fx_media_driver_status)
{
/* Not successful, return error status. */
return(media_ptr -> fx_media_driver_status);
}
/* Loop to check sector content. */
for (counter = 0; counter < media_ptr -> fx_media_bytes_per_sector; counter += sizeof(ULONG))
{
/* Read a 32 bit value from sector buffer. */
temp = _fx_utility_32_unsigned_read(§or_buffer[counter]);
/* Compare the read value with the caclulated checksum. */
if (temp != *calculated_checksum)
{
/* Not equal, checksum verify failed. */
return(FX_MEDIA_INVALID);
}
}
/* Return success. */
return(FX_SUCCESS);
}
#endif /* FX_ENABLE_EXFAT */
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