1/* fat.c  -  Read/write access to the FAT */
2
3/* Written 1993 by Werner Almesberger */
4
5/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
6 * by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
7
8
9#include <stdio.h>
10#include <stdlib.h>
11#include <string.h>
12#include <unistd.h>
13
14#define _LINUX_STRING_H_
15#include <linux/msdos_fs.h>
16
17#include "common.h"
18#include "dosfsck.h"
19#include "io.h"
20#include "check.h"
21#include "fat.h"
22
23
24static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
25{
26    unsigned char *ptr;
27
28    switch(fs->fat_bits) {
29      case 12:
30	ptr = &((unsigned char *) fat)[cluster*3/2];
31	entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
32	  (ptr[0] | ptr[1] << 8));
33	break;
34      case 16:
35	entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
36	break;
37      case 32:
38	/* According to M$, the high 4 bits of a FAT32 entry are reserved and
39	 * are not part of the cluster number. So we cut them off. */
40	{
41	    unsigned long e = CF_LE_L(((unsigned long *) fat)[cluster]);
42	    entry->value = e & 0xfffffff;
43	    entry->reserved = e >> 28;
44	}
45	break;
46      default:
47	die("Bad FAT entry size: %d bits.",fs->fat_bits);
48    }
49    entry->owner = NULL;
50}
51
52
53void read_fat(DOS_FS *fs)
54{
55    int eff_size;
56    unsigned long i;
57    void *first,*second,*use;
58    int first_ok,second_ok;
59
60    eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;
61    first = alloc(eff_size);
62    second = alloc(eff_size);
63    fs_read(fs->fat_start,eff_size,first);
64    fs_read(fs->fat_start+fs->fat_size,eff_size,second);
65    use = first;
66    if (memcmp(first,second,eff_size) != 0) {
67	FAT_ENTRY first_media, second_media;
68	get_fat(&first_media,first,0,fs);
69	get_fat(&second_media,second,0,fs);
70	first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
71	second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
72	if (first_ok && !second_ok) {
73	    printf("FATs differ - using first FAT.\n");
74	    fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
75	}
76	if (!first_ok && second_ok) {
77	    printf("FATs differ - using second FAT.\n");
78	    fs_write(fs->fat_start,eff_size,use = second);
79	}
80	if (first_ok && second_ok) {
81	    if (interactive) {
82		printf("FATs differ but appear to be intact. Use which FAT ?\n"
83		  "1) Use first FAT\n2) Use second FAT\n");
84		if (get_key("12","?") == '1')
85		    fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
86		else fs_write(fs->fat_start,eff_size,use = second);
87	    }
88	    else {
89		printf("FATs differ but appear to be intact. Using first "
90		  "FAT.\n");
91		fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
92	    }
93	}
94	if (!first_ok && !second_ok) {
95	    printf("Both FATs appear to be corrupt. Giving up.\n");
96	    exit(1);
97	}
98    }
99    fs->fat = qalloc(&mem_queue,sizeof(FAT_ENTRY)*(fs->clusters+2));
100    for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],use,i,fs);
101    for (i = 2; i < fs->clusters+2; i++)
102	if (fs->fat[i].value >= fs->clusters+2 &&
103	    (fs->fat[i].value < FAT_MIN_BAD(fs))) {
104	    printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
105		   i-2,fs->fat[i].value,fs->clusters+2-1);
106	    set_fat(fs,i,-1);
107	}
108    free(first);
109    free(second);
110}
111
112
113void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
114{
115    unsigned char data[4];
116    int size;
117    loff_t offs;
118
119    if ((long)new == -1)
120	new = FAT_EOF(fs);
121    else if ((long)new == -2)
122	new = FAT_BAD(fs);
123    switch( fs->fat_bits ) {
124      case 12:
125	offs = fs->fat_start+cluster*3/2;
126	if (cluster & 1) {
127	    data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
128	    data[1] = new >> 4;
129	}
130	else {
131	    data[0] = new & 0xff;
132	    data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
133	      (0xff & fs->fat[cluster+1].value) << 4);
134	}
135	size = 2;
136	break;
137      case 16:
138	offs = fs->fat_start+cluster*2;
139	*(unsigned short *) data = CT_LE_W(new);
140	size = 2;
141	break;
142      case 32:
143	offs = fs->fat_start+cluster*4;
144	/* According to M$, the high 4 bits of a FAT32 entry are reserved and
145	 * are not part of the cluster number. So we never touch them. */
146	*(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
147					   (fs->fat[cluster].reserved << 28) );
148	size = 4;
149	break;
150      default:
151	die("Bad FAT entry size: %d bits.",fs->fat_bits);
152    }
153    fs->fat[cluster].value = new;
154    fs_write(offs,size,&data);
155    fs_write(offs+fs->fat_size,size,&data);
156}
157
158
159int bad_cluster(DOS_FS *fs,unsigned long cluster)
160{
161    return FAT_IS_BAD(fs,fs->fat[cluster].value);
162}
163
164
165unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
166{
167    unsigned long value;
168
169    value = fs->fat[cluster].value;
170    if (FAT_IS_BAD(fs,value))
171	die("Internal error: next_cluster on bad cluster");
172    return FAT_IS_EOF(fs,value) ? -1 : value;
173}
174
175
176loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
177{
178    return fs->data_start+((loff_t)cluster-2)*fs->cluster_size;
179}
180
181
182void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
183{
184    if (owner && fs->fat[cluster].owner)
185	die("Internal error: attempt to change file owner");
186    fs->fat[cluster].owner = owner;
187}
188
189
190DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
191{
192    return fs->fat[cluster].owner;
193}
194
195
196void fix_bad(DOS_FS *fs)
197{
198    unsigned long i;
199
200    if (verbose)
201	printf("Checking for bad clusters.\n");
202    for (i = 2; i < fs->clusters+2; i++)
203	if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
204	    if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
205		printf("Cluster %lu is unreadable.\n",i);
206		set_fat(fs,i,-2);
207	    }
208}
209
210
211void reclaim_free(DOS_FS *fs)
212{
213    int reclaimed;
214    unsigned long i;
215
216    if (verbose)
217	printf("Checking for unused clusters.\n");
218    reclaimed = 0;
219    for (i = 2; i < fs->clusters+2; i++)
220	if (!get_owner(fs,i) && fs->fat[i].value &&
221	    !FAT_IS_BAD(fs,fs->fat[i].value)) {
222	    set_fat(fs,i,0);
223	    reclaimed++;
224	}
225    if (reclaimed)
226	printf("Reclaimed %d unused cluster%s (%d bytes).\n",reclaimed,
227	  reclaimed == 1 ?  "" : "s",reclaimed*fs->cluster_size);
228}
229
230
231static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
232{
233    DOS_FILE *owner;
234    int prev;
235    unsigned long i,walk;
236
237    for (i = 2; i < fs->clusters+2; i++)
238	if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
239	    !get_owner(fs,i) && !fs->fat[i].prev) {
240	    prev = 0;
241	    for (walk = i; walk > 0 && walk != -1;
242		 walk = next_cluster(fs,walk)) {
243		if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
244		else if (owner != ptr)
245		        die("Internal error: free chain collides with file");
246		    else {
247			set_fat(fs,prev,-1);
248			break;
249		    }
250		prev = walk;
251	    }
252	}
253}
254
255
256void reclaim_file(DOS_FS *fs)
257{
258    DOS_FILE dummy;
259    int reclaimed,files,changed;
260    unsigned long i,next,walk;
261
262    if (verbose)
263	printf("Reclaiming unconnected clusters.\n");
264    for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
265    for (i = 2; i < fs->clusters+2; i++) {
266	next = fs->fat[i].value;
267	if (!get_owner(fs,i) && next && next < fs->clusters+2) {
268	    if (get_owner(fs,next) || !fs->fat[next].value ||
269		FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
270	    else fs->fat[next].prev++;
271	}
272    }
273    do {
274	tag_free(fs,&dummy);
275	changed = 0;
276	for (i = 2; i < fs->clusters+2; i++)
277	    if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
278		!get_owner(fs, i)) {
279		if (!fs->fat[fs->fat[i].value].prev--)
280		    die("Internal error: prev going below zero");
281		set_fat(fs,i,-1);
282		changed = 1;
283		printf("Broke cycle at cluster %lu in free chain.\n",i);
284		break;
285	    }
286    }
287    while (changed);
288    files = reclaimed = 0;
289    for (i = 2; i < fs->clusters+2; i++)
290	if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
291	    DIR_ENT de;
292	    loff_t offset;
293	    files++;
294	    offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
295	    de.start = CT_LE_W(i&0xffff);
296	    if (fs->fat_bits == 32)
297		de.starthi = CT_LE_W(i>>16);
298	    for (walk = i; walk > 0 && walk != -1;
299		 walk = next_cluster(fs,walk)) {
300		de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
301		reclaimed++;
302	    }
303	    fs_write(offset,sizeof(DIR_ENT),&de);
304	}
305    if (reclaimed)
306	printf("Reclaimed %d unused cluster%s (%d bytes) in %d chain%s.\n",
307	  reclaimed,reclaimed == 1 ? "" : "s",reclaimed*fs->cluster_size,files,
308	  files == 1 ? "" : "s");
309}
310
311
312unsigned long update_free(DOS_FS *fs)
313{
314    unsigned long i;
315    unsigned long free = 0;
316    int do_set = 0;
317
318    for (i = 2; i < fs->clusters+2; i++)
319	if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
320	    ++free;
321
322    if (!fs->fsinfo_start)
323	return free;
324
325    if (verbose)
326	printf("Checking free cluster summary.\n");
327    if (fs->free_clusters >= 0) {
328	if (free != fs->free_clusters) {
329	    printf( "Free cluster summary wrong (%ld vs. really %ld)\n",
330		    fs->free_clusters,free);
331	    if (interactive)
332		printf( "1) Correct\n2) Don't correct\n" );
333	    else printf( "  Auto-correcting.\n" );
334	    if (!interactive || get_key("12","?") == '1')
335		do_set = 1;
336	}
337    }
338    else {
339	printf( "Free cluster summary uninitialized (should be %ld)\n", free );
340	if (interactive)
341	    printf( "1) Set it\n2) Leave it uninitialized\n" );
342	else printf( "  Auto-setting.\n" );
343	if (!interactive || get_key("12","?") == '1')
344	    do_set = 1;
345    }
346
347    if (do_set) {
348	fs->free_clusters = free;
349	free = CT_LE_L(free);
350	fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
351		 sizeof(free),&free);
352    }
353
354    return free;
355}
356
357/* Local Variables: */
358/* tab-width: 8     */
359/* End:             */
360