| wdenk | 2262cfe | 2002-11-18 00:14:45 +0000 | [diff] [blame] | 1 | /* |
| 2 | * (C) Copyright 2002 |
| 3 | * Stäubli Faverges - <www.staubli.com> |
| 4 | * Pierre AUBERT p.aubert@staubli.com |
| 5 | * |
| 6 | * See file CREDITS for list of people who contributed to this |
| 7 | * project. |
| 8 | * |
| 9 | * This program is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU General Public License as |
| 11 | * published by the Free Software Foundation; either version 2 of |
| 12 | * the License, or (at your option) any later version. |
| 13 | * |
| 14 | * This program is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 17 | * GNU General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU General Public License |
| 20 | * along with this program; if not, write to the Free Software |
| 21 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, |
| 22 | * MA 02111-1307 USA |
| 23 | */ |
| 24 | |
| 25 | #include <common.h> |
| 26 | #include <config.h> |
| 27 | #include <malloc.h> |
| 28 | |
| 29 | #if (CONFIG_COMMANDS & CFG_CMD_FDOS) |
| 30 | |
| 31 | #include "dos.h" |
| 32 | #include "fdos.h" |
| 33 | |
| 34 | |
| 35 | /*----------------------------------------------------------------------------- |
| 36 | * fat_decode -- |
| 37 | *----------------------------------------------------------------------------- |
| 38 | */ |
| 39 | unsigned int fat_decode (Fs_t *fs, unsigned int num) |
| 40 | { |
| 41 | unsigned int start = num * 3 / 2; |
| 42 | unsigned char *address = fs -> fat_buf + start; |
| 43 | |
| 44 | if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR)) |
| 45 | return 1; |
| 46 | |
| 47 | if (num & 1) |
| 48 | return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4); |
| 49 | else |
| 50 | return ((address [1] & 0xf) << 8) | (address [0] & 0xff ); |
| 51 | } |
| 52 | /*----------------------------------------------------------------------------- |
| 53 | * check_fat -- |
| 54 | *----------------------------------------------------------------------------- |
| 55 | */ |
| 56 | static int check_fat (Fs_t *fs) |
| 57 | { |
| 58 | int i, f; |
| 59 | |
| 60 | /* Cluster verification */ |
| 61 | for (i = 3 ; i < fs -> num_clus; i++){ |
| 62 | f = fat_decode (fs, i); |
| 63 | if (f < FAT12_LAST && f > fs -> num_clus){ |
| 64 | /* Wrong cluster number detected */ |
| 65 | return (-1); |
| 66 | } |
| 67 | } |
| 68 | return (0); |
| 69 | } |
| 70 | /*----------------------------------------------------------------------------- |
| 71 | * read_one_fat -- |
| 72 | *----------------------------------------------------------------------------- |
| 73 | */ |
| 74 | static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat) |
| 75 | { |
| 76 | if (dev_read (fs -> fat_buf, |
| 77 | (fs -> fat_start + nfat * fs -> fat_len), |
| 78 | fs -> fat_len) < 0) { |
| 79 | return (-1); |
| 80 | } |
| 81 | |
| 82 | if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) { |
| 83 | if ((fs -> fat_buf [0] != boot -> descr && |
| 84 | (fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) || |
| 85 | fs -> fat_buf [0] < MEDIA_STD){ |
| 86 | /* Unknown Media */ |
| 87 | return (-1); |
| 88 | } |
| 89 | if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){ |
| 90 | /* FAT doesn't start with good values */ |
| 91 | return (-1); |
| 92 | } |
| 93 | } |
| 94 | |
| 95 | if (fs -> num_clus >= FAT12_MAX_NB) { |
| 96 | /* Too much clusters */ |
| 97 | return (-1); |
| 98 | } |
| 99 | |
| 100 | return check_fat (fs); |
| 101 | } |
| 102 | /*----------------------------------------------------------------------------- |
| 103 | * read_fat -- |
| 104 | *----------------------------------------------------------------------------- |
| 105 | */ |
| 106 | int read_fat (BootSector_t *boot, Fs_t *fs) |
| 107 | { |
| 108 | unsigned int buflen; |
| 109 | int i; |
| 110 | |
| 111 | /* Allocate Fat Buffer */ |
| 112 | buflen = fs -> fat_len * SZ_STD_SECTOR; |
| 113 | if (fs -> fat_buf) { |
| 114 | free (fs -> fat_buf); |
| 115 | } |
| 116 | |
| 117 | if ((fs -> fat_buf = malloc (buflen)) == NULL) { |
| 118 | return (-1); |
| 119 | } |
| 120 | |
| 121 | /* Try to read each Fat */ |
| 122 | for (i = 0; i< fs -> nb_fat; i++){ |
| 123 | if (read_one_fat (boot, fs, i) == 0) { |
| 124 | /* Fat is OK */ |
| 125 | fs -> num_fat = i; |
| 126 | break; |
| 127 | } |
| 128 | } |
| 129 | |
| 130 | if (i == fs -> nb_fat){ |
| 131 | return (-1); |
| 132 | } |
| 133 | |
| 134 | if (fs -> fat_len > (((fs -> num_clus + 2) * |
| 135 | (FAT_BITS / 4) -1 ) / 2 / |
| 136 | SZ_STD_SECTOR + 1)) { |
| 137 | return (-1); |
| 138 | } |
| 139 | return (0); |
| 140 | } |
| 141 | |
| 142 | |
| 143 | |
| 144 | |
| 145 | #endif |