usbloadergx/source/libfat/partition.c

/*
 partition.c
 Functions for mounting and dismounting partitions
 on various block devices.

 Copyright (c) 2006 Michael "Chishm" Chisholm

 Redistribution and use in source and binary forms, with or without modification,
 are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice,
     this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright notice,
     this list of conditions and the following disclaimer in the documentation and/or
     other materials provided with the distribution.
  3. The name of the author may not be used to endorse or promote products derived
     from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "partition.h"
#include "bit_ops.h"
#include "file_allocation_table.h"
#include "directory.h"
#include "mem_allocate.h"
#include "fatfile.h"

#include <string.h>
#include <ctype.h>
#include <sys/iosupport.h>

sec_t _FAT_startSector;

/*
This device name, as known by devkitPro toolchains
*/
const char* DEVICE_NAME = "fat";

/*
Data offsets
*/

// BIOS Parameter Block offsets
enum BPB
{
    BPB_jmpBoot = 0x00,
    BPB_OEMName = 0x03,
    // BIOS Parameter Block
    BPB_bytesPerSector = 0x0B,
    BPB_sectorsPerCluster = 0x0D,
    BPB_reservedSectors = 0x0E,
    BPB_numFATs = 0x10,
    BPB_rootEntries = 0x11,
    BPB_numSectorsSmall = 0x13,
    BPB_mediaDesc = 0x15,
    BPB_sectorsPerFAT = 0x16,
    BPB_sectorsPerTrk = 0x18,
    BPB_numHeads = 0x1A,
    BPB_numHiddenSectors = 0x1C,
    BPB_numSectors = 0x20,
    // Ext BIOS Parameter Block for FAT16
    BPB_FAT16_driveNumber = 0x24,
    BPB_FAT16_reserved1 = 0x25,
    BPB_FAT16_extBootSig = 0x26,
    BPB_FAT16_volumeID = 0x27,
    BPB_FAT16_volumeLabel = 0x2B,
    BPB_FAT16_fileSysType = 0x36,
    // Bootcode
    BPB_FAT16_bootCode = 0x3E,
    // FAT32 extended block
    BPB_FAT32_sectorsPerFAT32 = 0x24,
    BPB_FAT32_extFlags = 0x28,
    BPB_FAT32_fsVer = 0x2A,
    BPB_FAT32_rootClus = 0x2C,
    BPB_FAT32_fsInfo = 0x30,
    BPB_FAT32_bkBootSec = 0x32,
    // Ext BIOS Parameter Block for FAT32
    BPB_FAT32_driveNumber = 0x40,
    BPB_FAT32_reserved1 = 0x41,
    BPB_FAT32_extBootSig = 0x42,
    BPB_FAT32_volumeID = 0x43,
    BPB_FAT32_volumeLabel = 0x47,
    BPB_FAT32_fileSysType = 0x52,
    // Bootcode
    BPB_FAT32_bootCode = 0x5A,
    BPB_bootSig_55 = 0x1FE,
    BPB_bootSig_AA = 0x1FF
};

static const char FAT_SIG[3] = {'F', 'A', 'T'};


sec_t FindFirstValidPartition( const DISC_INTERFACE* disc )
{
    uint8_t part_table[16*4];
    uint8_t *ptr;
    int i;

    uint8_t sectorBuffer[BYTES_PER_READ] = {0};

    // Read first sector of disc
    if ( !_FAT_disc_readSectors ( disc, 0, 1, sectorBuffer ) )
    {
        return 0;
    }

    memcpy( part_table, sectorBuffer + 0x1BE, 16*4 );
    ptr = part_table;

    for ( i = 0; i < 4; i++, ptr += 16 )
    {
        sec_t part_lba = u8array_to_u32( ptr, 0x8 );

        if ( !memcmp( sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) ||
                !memcmp( sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
        {
            return part_lba;
        }

        if ( ptr[4] == 0 ) continue;

        if ( ptr[4] == 0x0F )
        {
            sec_t part_lba2 = part_lba;
            sec_t next_lba2 = 0;
            int n;

            for ( n = 0; n < 8; n++ ) // max 8 logic partitions
            {
                if ( !_FAT_disc_readSectors ( disc, part_lba + next_lba2, 1, sectorBuffer ) ) return 0;

                part_lba2 = part_lba + next_lba2 + u8array_to_u32( sectorBuffer, 0x1C6 ) ;
                next_lba2 = u8array_to_u32( sectorBuffer, 0x1D6 );

                if ( !_FAT_disc_readSectors ( disc, part_lba2, 1, sectorBuffer ) ) return 0;

                if ( !memcmp( sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) ||
                        !memcmp( sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
                {
                    return part_lba2;
                }

                if ( next_lba2 == 0 ) break;
            }
        }
        else
        {
            if ( !_FAT_disc_readSectors ( disc, part_lba, 1, sectorBuffer ) ) return 0;
            if ( !memcmp( sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) ||
                    !memcmp( sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
            {
                return part_lba;
            }
        }
    }
    return 0;
}

PARTITION* _FAT_partition_constructor ( const DISC_INTERFACE* disc, uint32_t cacheSize, uint32_t sectorsPerPage, sec_t startSector )
{
    PARTITION* partition;
    uint8_t sectorBuffer[BYTES_PER_READ] = {0};

    // Read first sector of disc
    if ( !_FAT_disc_readSectors ( disc, startSector, 1, sectorBuffer ) )
    {
        return NULL;
    }

    // Make sure it is a valid MBR or boot sector
    if ( ( sectorBuffer[BPB_bootSig_55] != 0x55 ) || ( sectorBuffer[BPB_bootSig_AA] != 0xAA ) )
    {
        return NULL;
    }

    if ( startSector != 0 )
    {
        // We're told where to start the partition, so just accept it
    }
    else if ( !memcmp( sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
    {
        // Check if there is a FAT string, which indicates this is a boot sector
        startSector = 0;
    }
    else if ( !memcmp( sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
    {
        // Check for FAT32
        startSector = 0;
    }
    else
    {
        startSector = FindFirstValidPartition( disc );
        if ( !_FAT_disc_readSectors ( disc, startSector, 1, sectorBuffer ) )
        {
            return NULL;
        }
    }

    // Now verify that this is indeed a FAT partition
    if ( memcmp( sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) &&
            memcmp( sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof( FAT_SIG ) ) )
    {
        return NULL;
    }

    // check again for the last two cases to make sure that we really have a FAT filesystem here
    // and won't corrupt any data
    if ( memcmp( sectorBuffer + BPB_FAT16_fileSysType, "FAT", 3 ) != 0 && memcmp( sectorBuffer + BPB_FAT32_fileSysType, "FAT32", 5 ) != 0 )
    {
        return NULL;
    }

    partition = ( PARTITION* ) _FAT_mem_allocate ( sizeof( PARTITION ) );
    if ( partition == NULL )
    {
        return NULL;
    }

    _FAT_startSector = startSector;

    // Init the partition lock
    _FAT_lock_init( &partition->lock );

    // Set partition's disc interface
    partition->disc = disc;

    // Store required information about the file system
    partition->fat.sectorsPerFat = u8array_to_u16( sectorBuffer, BPB_sectorsPerFAT );
    if ( partition->fat.sectorsPerFat == 0 )
    {
        partition->fat.sectorsPerFat = u8array_to_u32( sectorBuffer, BPB_FAT32_sectorsPerFAT32 );
    }

    partition->numberOfSectors = u8array_to_u16( sectorBuffer, BPB_numSectorsSmall );
    if ( partition->numberOfSectors == 0 )
    {
        partition->numberOfSectors = u8array_to_u32( sectorBuffer, BPB_numSectors );
    }

    partition->bytesPerSector = BYTES_PER_READ; // Sector size is redefined to be 512 bytes
    partition->sectorsPerCluster = sectorBuffer[BPB_sectorsPerCluster] * u8array_to_u16( sectorBuffer, BPB_bytesPerSector ) / BYTES_PER_READ;
    partition->bytesPerCluster = partition->bytesPerSector * partition->sectorsPerCluster;
    partition->fat.fatStart = startSector + u8array_to_u16( sectorBuffer, BPB_reservedSectors );

    partition->rootDirStart = partition->fat.fatStart + ( sectorBuffer[BPB_numFATs] * partition->fat.sectorsPerFat );
    partition->dataStart = partition->rootDirStart +
                           ( ( u8array_to_u16( sectorBuffer, BPB_rootEntries ) * DIR_ENTRY_DATA_SIZE ) / partition->bytesPerSector );

    partition->totalSize = ( ( uint64_t )partition->numberOfSectors - ( partition->dataStart - startSector ) ) * ( uint64_t )partition->bytesPerSector;

    // Store info about FAT
    uint32_t clusterCount = ( partition->numberOfSectors - ( uint32_t )( partition->dataStart - startSector ) ) / partition->sectorsPerCluster;
    partition->fat.lastCluster = clusterCount + CLUSTER_FIRST - 1;
    partition->fat.firstFree = CLUSTER_FIRST;

    if ( clusterCount < CLUSTERS_PER_FAT12 )
    {
        partition->filesysType = FS_FAT12;  // FAT12 volume
    }
    else if ( clusterCount < CLUSTERS_PER_FAT16 )
    {
        partition->filesysType = FS_FAT16;  // FAT16 volume
    }
    else
    {
        partition->filesysType = FS_FAT32;  // FAT32 volume
    }

    if ( partition->filesysType != FS_FAT32 )
    {
        partition->rootDirCluster = FAT16_ROOT_DIR_CLUSTER;
    }
    else
    {
        // Set up for the FAT32 way
        partition->rootDirCluster = u8array_to_u32( sectorBuffer, BPB_FAT32_rootClus );
        // Check if FAT mirroring is enabled
        if ( !( sectorBuffer[BPB_FAT32_extFlags] & 0x80 ) )
        {
            // Use the active FAT
            partition->fat.fatStart = partition->fat.fatStart + ( partition->fat.sectorsPerFat * ( sectorBuffer[BPB_FAT32_extFlags] & 0x0F ) );
        }
    }

    // Create a cache to use
    partition->cache = _FAT_cache_constructor ( cacheSize, sectorsPerPage, partition->disc, startSector + partition->numberOfSectors );

    // Set current directory to the root
    partition->cwdCluster = partition->rootDirCluster;

    // Check if this disc is writable, and set the readOnly property appropriately
    partition->readOnly = !( _FAT_disc_features( disc ) & FEATURE_MEDIUM_CANWRITE );

    // There are currently no open files on this partition
    partition->openFileCount = 0;
    partition->firstOpenFile = NULL;

    return partition;
}

void _FAT_partition_destructor ( PARTITION* partition )
{
    FILE_STRUCT* nextFile;

    _FAT_lock( &partition->lock );

    // Synchronize open files
    nextFile = partition->firstOpenFile;
    while ( nextFile )
    {
        _FAT_syncToDisc ( nextFile );
        nextFile = nextFile->nextOpenFile;
    }

    // Free memory used by the cache, writing it to disc at the same time
    _FAT_cache_destructor ( partition->cache );

    // Unlock the partition and destroy the lock
    _FAT_unlock( &partition->lock );
    _FAT_lock_deinit( &partition->lock );

    // Free memory used by the partition
    _FAT_mem_free ( partition );
}

PARTITION* _FAT_partition_getPartitionFromPath ( const char* path )
{
    const devoptab_t *devops;

    devops = GetDeviceOpTab ( path );

    if ( !devops )
    {
        return NULL;
    }

    return ( PARTITION* )devops->deviceData;
}