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u-boot/include/fat.h
Mikhail Zolotaryov 3831530dcb VFAT: fix processing of scattered long file name entries 
The U-Boot code has the following bugs related to the processing of Long File
Name (LFN) entries scattered across several clusters/sectors :

1) get_vfatname() function is designed to gather scattered LFN entries by
cluster chain processing - that doesn't work for FAT12/16 root directory.
In other words, the function expects the following input data:
 1.1) FAT32 directory (which is cluster chain based);
        OR
 1.2) FAT12/16 non-root directory (which is also cluster chain based);
        OR
 1.3) FAT12/16 root directory (allocated as contiguous sectors area), but
 all necessary information MUST be within the input buffer of filesystem cluster
 size (thus cluster-chain jump is never initiated).

In order to accomplish the last condition, root directory parsing code in
do_fat_read() uses the following trick: read-out cluster-size block, process
only first sector (512 bytes), then shift 512 forward, read-out cluster-size
block and so on. This works great unless cluster size is equal to 512 bytes
(in a case you have a small partition), or long file name entries are scattered
across three sectors, see 4) for details.

2) Despite of the fact that get_vfatname() supports FAT32 root directory
browsing, do_fat_read() function doesn't send current cluster number correctly,
so root directory look-up doesn't work correctly.

3) get_vfatname() doesn't gather scattered entries correctly also is the case
when all LFN entries are located at the end of the source cluster, but real
directory entry (which must be returned) is at the only beginning of the
next one. No error detected, the resulting directory entry returned contains
a semi-random information (wrong size, wrong start cluster number and so on)
i.e. the entry is not accessible.

4) LFN (VFAT) allows up to 20 entries (slots) each containing 26 bytes (13
UTF-16 code units) to represent a single long file name i.e. up to 520 bytes.
U-Boot allocates 256 bytes buffer instead, i.e. 10 or more LFN slots record
may cause buffer overflow / memory corruption.
Also, it's worth to mention that 20+1 slots occupy 672 bytes space which may
take more than one cluster of 512 bytes (medium-size FAT32 or small FAT16
partition) - get_vfatname() function doesn't support such case as well.

The patch attached fixes these problems in the following way:
- keep using 256 bytes buffer for a long file name, but safely prevent a
possible buffer overflow (skip LFN processing, if it contains 10 or more
slots).

- explicitly specify FAT12/16 root directory parsing buffer size, instead
of relying on cluster size. The value used is a double sector size (to store
current sector and the next one). This fixes the first problem and increases
performance on big FAT12/16 partitions;

- send current cluster number (FAT32) to get_vfatname() during root
directory processing;

- use LFN counter to seek the real directory entry in get_vfatname() - fixes the
third problem;

- skip deleted entries in the root directory (to prevent bogus buffer
overflow detection and LFN counter steps).

Note: it's not advised to split up the patch, because a separate part may
operate incorrectly.

Signed-off-by: Mikhail Zolotaryov <lebon@lebon.org.ua>
2010-10-12 22:39:14 +02:00

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/*
* R/O (V)FAT 12/16/32 filesystem implementation by Marcus Sundberg
*
* 2002-07-28 - rjones@nexus-tech.net - ported to ppcboot v1.1.6
* 2003-03-10 - kharris@nexus-tech.net - ported to u-boot
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*
*/
#ifndef _FAT_H_
#define _FAT_H_
#include <asm/byteorder.h>
#define CONFIG_SUPPORT_VFAT
/* Maximum Long File Name length supported here is 128 UTF-16 code units */
#define VFAT_MAXLEN_BYTES 256 /* Maximum LFN buffer in bytes */
#define VFAT_MAXSEQ 9 /* Up to 9 of 13 2-byte UTF-16 entries */
#define LINEAR_PREFETCH_SIZE (SECTOR_SIZE*2) /* Prefetch buffer size */
#define SECTOR_SIZE FS_BLOCK_SIZE
#define FS_BLOCK_SIZE 512
#if FS_BLOCK_SIZE != SECTOR_SIZE
#error FS_BLOCK_SIZE != SECTOR_SIZE - This code needs to be fixed!
#endif
#define MAX_CLUSTSIZE 65536
#define DIRENTSPERBLOCK (FS_BLOCK_SIZE/sizeof(dir_entry))
#define DIRENTSPERCLUST ((mydata->clust_size*SECTOR_SIZE)/sizeof(dir_entry))
#define FATBUFBLOCKS 6
#define FATBUFSIZE (FS_BLOCK_SIZE*FATBUFBLOCKS)
#define FAT12BUFSIZE ((FATBUFSIZE*2)/3)
#define FAT16BUFSIZE (FATBUFSIZE/2)
#define FAT32BUFSIZE (FATBUFSIZE/4)
/* Filesystem identifiers */
#define FAT12_SIGN "FAT12 "
#define FAT16_SIGN "FAT16 "
#define FAT32_SIGN "FAT32 "
#define SIGNLEN 8
/* File attributes */
#define ATTR_RO 1
#define ATTR_HIDDEN 2
#define ATTR_SYS 4
#define ATTR_VOLUME 8
#define ATTR_DIR 16
#define ATTR_ARCH 32
#define ATTR_VFAT (ATTR_RO | ATTR_HIDDEN | ATTR_SYS | ATTR_VOLUME)
#define DELETED_FLAG ((char)0xe5) /* Marks deleted files when in name[0] */
#define aRING 0x05 /* Used as special character in name[0] */
/*
* Indicates that the entry is the last long entry in a set of long
* dir entries
*/
#define LAST_LONG_ENTRY_MASK 0x40
/* Flags telling whether we should read a file or list a directory */
#define LS_NO 0
#define LS_YES 1
#define LS_DIR 1
#define LS_ROOT 2
#define ISDIRDELIM(c) ((c) == '/' || (c) == '\\')
#define FSTYPE_NONE (-1)
#if defined(__linux__) && defined(__KERNEL__)
#define FAT2CPU16 le16_to_cpu
#define FAT2CPU32 le32_to_cpu
#else
#if __LITTLE_ENDIAN
#define FAT2CPU16(x) (x)
#define FAT2CPU32(x) (x)
#else
#define FAT2CPU16(x) ((((x) & 0x00ff) << 8) | (((x) & 0xff00) >> 8))
#define FAT2CPU32(x) ((((x) & 0x000000ff) << 24) | \
(((x) & 0x0000ff00) << 8) | \
(((x) & 0x00ff0000) >> 8) | \
(((x) & 0xff000000) >> 24))
#endif
#endif
#define TOLOWER(c) if((c) >= 'A' && (c) <= 'Z'){(c)+=('a' - 'A');}
#define START(dent) (FAT2CPU16((dent)->start) \
+ (mydata->fatsize != 32 ? 0 : \
(FAT2CPU16((dent)->starthi) << 16)))
#define CHECK_CLUST(x, fatsize) ((x) <= 1 || \
(x) >= ((fatsize) != 32 ? 0xfff0 : 0xffffff0))
typedef struct boot_sector {
__u8 ignored[3]; /* Bootstrap code */
char system_id[8]; /* Name of fs */
__u8 sector_size[2]; /* Bytes/sector */
__u8 cluster_size; /* Sectors/cluster */
__u16 reserved; /* Number of reserved sectors */
__u8 fats; /* Number of FATs */
__u8 dir_entries[2]; /* Number of root directory entries */
__u8 sectors[2]; /* Number of sectors */
__u8 media; /* Media code */
__u16 fat_length; /* Sectors/FAT */
__u16 secs_track; /* Sectors/track */
__u16 heads; /* Number of heads */
__u32 hidden; /* Number of hidden sectors */
__u32 total_sect; /* Number of sectors (if sectors == 0) */
/* FAT32 only */
__u32 fat32_length; /* Sectors/FAT */
__u16 flags; /* Bit 8: fat mirroring, low 4: active fat */
__u8 version[2]; /* Filesystem version */
__u32 root_cluster; /* First cluster in root directory */
__u16 info_sector; /* Filesystem info sector */
__u16 backup_boot; /* Backup boot sector */
__u16 reserved2[6]; /* Unused */
} boot_sector;
typedef struct volume_info
{
__u8 drive_number; /* BIOS drive number */
__u8 reserved; /* Unused */
__u8 ext_boot_sign; /* 0x29 if fields below exist (DOS 3.3+) */
__u8 volume_id[4]; /* Volume ID number */
char volume_label[11]; /* Volume label */
char fs_type[8]; /* Typically FAT12, FAT16, or FAT32 */
/* Boot code comes next, all but 2 bytes to fill up sector */
/* Boot sign comes last, 2 bytes */
} volume_info;
typedef struct dir_entry {
char name[8],ext[3]; /* Name and extension */
__u8 attr; /* Attribute bits */
__u8 lcase; /* Case for base and extension */
__u8 ctime_ms; /* Creation time, milliseconds */
__u16 ctime; /* Creation time */
__u16 cdate; /* Creation date */
__u16 adate; /* Last access date */
__u16 starthi; /* High 16 bits of cluster in FAT32 */
__u16 time,date,start;/* Time, date and first cluster */
__u32 size; /* File size in bytes */
} dir_entry;
typedef struct dir_slot {
__u8 id; /* Sequence number for slot */
__u8 name0_4[10]; /* First 5 characters in name */
__u8 attr; /* Attribute byte */
__u8 reserved; /* Unused */
__u8 alias_checksum;/* Checksum for 8.3 alias */
__u8 name5_10[12]; /* 6 more characters in name */
__u16 start; /* Unused */
__u8 name11_12[4]; /* Last 2 characters in name */
} dir_slot;
/*
* Private filesystem parameters
*
* Note: FAT buffer has to be 32 bit aligned
* (see FAT32 accesses)
*/
typedef struct {
__u8 fatbuf[FATBUFSIZE]; /* Current FAT buffer */
int fatsize; /* Size of FAT in bits */
__u16 fatlength; /* Length of FAT in sectors */
__u16 fat_sect; /* Starting sector of the FAT */
__u16 rootdir_sect; /* Start sector of root directory */
__u16 clust_size; /* Size of clusters in sectors */
short data_begin; /* The sector of the first cluster, can be negative */
int fatbufnum; /* Used by get_fatent, init to -1 */
} fsdata;
typedef int (file_detectfs_func)(void);
typedef int (file_ls_func)(const char *dir);
typedef long (file_read_func)(const char *filename, void *buffer,
unsigned long maxsize);
struct filesystem {
file_detectfs_func *detect;
file_ls_func *ls;
file_read_func *read;
const char name[12];
};
/* FAT tables */
file_detectfs_func file_fat_detectfs;
file_ls_func file_fat_ls;
file_read_func file_fat_read;
/* Currently this doesn't check if the dir exists or is valid... */
int file_cd(const char *path);
int file_fat_detectfs(void);
int file_fat_ls(const char *dir);
long file_fat_read(const char *filename, void *buffer, unsigned long maxsize);
const char *file_getfsname(int idx);
int fat_register_device(block_dev_desc_t *dev_desc, int part_no);
#endif /* _FAT_H_ */
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