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wdenk2262cfe2002-11-18 00:14:45 +00001/*
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
wdenk2262cfe2002-11-18 00:14:45 +000029#include "dos.h"
30#include "fdos.h"
31
32
33/*-----------------------------------------------------------------------------
wdenk8bde7f72003-06-27 21:31:46 +000034 * fat_decode --
wdenk2262cfe2002-11-18 00:14:45 +000035 *-----------------------------------------------------------------------------
36 */
37unsigned int fat_decode (Fs_t *fs, unsigned int num)
38{
39 unsigned int start = num * 3 / 2;
40 unsigned char *address = fs -> fat_buf + start;
wdenk8bde7f72003-06-27 21:31:46 +000041
wdenk2262cfe2002-11-18 00:14:45 +000042 if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR))
wdenk8bde7f72003-06-27 21:31:46 +000043 return 1;
44
wdenk2262cfe2002-11-18 00:14:45 +000045 if (num & 1)
wdenk8bde7f72003-06-27 21:31:46 +000046 return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4);
wdenk2262cfe2002-11-18 00:14:45 +000047 else
wdenk8bde7f72003-06-27 21:31:46 +000048 return ((address [1] & 0xf) << 8) | (address [0] & 0xff );
wdenk2262cfe2002-11-18 00:14:45 +000049}
50/*-----------------------------------------------------------------------------
wdenk8bde7f72003-06-27 21:31:46 +000051 * check_fat --
wdenk2262cfe2002-11-18 00:14:45 +000052 *-----------------------------------------------------------------------------
53 */
54static int check_fat (Fs_t *fs)
55{
56 int i, f;
57
58 /* Cluster verification */
59 for (i = 3 ; i < fs -> num_clus; i++){
wdenk8bde7f72003-06-27 21:31:46 +000060 f = fat_decode (fs, i);
61 if (f < FAT12_LAST && f > fs -> num_clus){
62 /* Wrong cluster number detected */
63 return (-1);
64 }
wdenk2262cfe2002-11-18 00:14:45 +000065 }
66 return (0);
67}
68/*-----------------------------------------------------------------------------
wdenk8bde7f72003-06-27 21:31:46 +000069 * read_one_fat --
wdenk2262cfe2002-11-18 00:14:45 +000070 *-----------------------------------------------------------------------------
71 */
72static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat)
73{
74 if (dev_read (fs -> fat_buf,
wdenk8bde7f72003-06-27 21:31:46 +000075 (fs -> fat_start + nfat * fs -> fat_len),
76 fs -> fat_len) < 0) {
77 return (-1);
wdenk2262cfe2002-11-18 00:14:45 +000078 }
79
80 if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) {
wdenk8bde7f72003-06-27 21:31:46 +000081 if ((fs -> fat_buf [0] != boot -> descr &&
82 (fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) ||
83 fs -> fat_buf [0] < MEDIA_STD){
84 /* Unknown Media */
85 return (-1);
86 }
87 if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){
88 /* FAT doesn't start with good values */
89 return (-1);
90 }
wdenk2262cfe2002-11-18 00:14:45 +000091 }
92
93 if (fs -> num_clus >= FAT12_MAX_NB) {
wdenk8bde7f72003-06-27 21:31:46 +000094 /* Too much clusters */
95 return (-1);
wdenk2262cfe2002-11-18 00:14:45 +000096 }
97
98 return check_fat (fs);
99}
100/*-----------------------------------------------------------------------------
wdenk8bde7f72003-06-27 21:31:46 +0000101 * read_fat --
wdenk2262cfe2002-11-18 00:14:45 +0000102 *-----------------------------------------------------------------------------
103 */
104int read_fat (BootSector_t *boot, Fs_t *fs)
105{
106 unsigned int buflen;
107 int i;
108
109 /* Allocate Fat Buffer */
110 buflen = fs -> fat_len * SZ_STD_SECTOR;
111 if (fs -> fat_buf) {
wdenk8bde7f72003-06-27 21:31:46 +0000112 free (fs -> fat_buf);
wdenk2262cfe2002-11-18 00:14:45 +0000113 }
114
115 if ((fs -> fat_buf = malloc (buflen)) == NULL) {
wdenk8bde7f72003-06-27 21:31:46 +0000116 return (-1);
wdenk2262cfe2002-11-18 00:14:45 +0000117 }
118
119 /* Try to read each Fat */
120 for (i = 0; i< fs -> nb_fat; i++){
wdenk8bde7f72003-06-27 21:31:46 +0000121 if (read_one_fat (boot, fs, i) == 0) {
122 /* Fat is OK */
123 fs -> num_fat = i;
124 break;
125 }
wdenk2262cfe2002-11-18 00:14:45 +0000126 }
127
128 if (i == fs -> nb_fat){
wdenk8bde7f72003-06-27 21:31:46 +0000129 return (-1);
wdenk2262cfe2002-11-18 00:14:45 +0000130 }
wdenk8bde7f72003-06-27 21:31:46 +0000131
wdenk2262cfe2002-11-18 00:14:45 +0000132 if (fs -> fat_len > (((fs -> num_clus + 2) *
wdenk8bde7f72003-06-27 21:31:46 +0000133 (FAT_BITS / 4) -1 ) / 2 /
134 SZ_STD_SECTOR + 1)) {
135 return (-1);
wdenk2262cfe2002-11-18 00:14:45 +0000136 }
137 return (0);
138}