fat.c 10 KB

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