rosapps/sysutils/dosfsck/fat.c

   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 #include "common.h"
  15 #include "dosfsck.h"
  16 #include "io.h"
  17 #include "check.h"
  18 #include "fat.h"
  19
  20 #pragma warning(disable: 4018)
  21
  22 static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
  23 {
  24     unsigned char *ptr;
  25
  26     switch(fs->fat_bits) {
  27       case 12:
  28         ptr = &((unsigned char *) fat)[cluster*3/2];
  29         entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
  30           (ptr[0] | ptr[1] << 8));
  31         break;
  32       case 16:
  33         entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
  34         break;
  35       case 32:
  36         /* According to M$, the high 4 bits of a FAT32 entry are reserved and
  37          * are not part of the cluster number. So we cut them off. */
  38         {
  39             unsigned long e = CF_LE_L(((unsigned int *) fat)[cluster]);
  40             entry->value = e & 0xfffffff;
  41             entry->reserved = e >> 28;
  42         }
  43         break;
  44       default:
  45         die("Bad FAT entry size: %d bits.",fs->fat_bits);
  46     }
  47     entry->owner = NULL;
  48 }
  49
  50
  51 void read_fat(DOS_FS *fs)
  52 {
  53     int eff_size;
  54     unsigned long i;
  55     void *first,*second,*use;
  56     int first_ok,second_ok;
  57
  58     eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;
  59         // TMN: Must round up to disk-sector boundary. For now, assume 512-byte disk.
  60         if (eff_size % 512) {
  61                 eff_size += 512 - (eff_size % 512);
  62         }
  63     first = alloc(eff_size);
  64     fs_read(fs->fat_start,eff_size,first);
  65     use = first;
  66     if (fs->nfats > 1) {
  67         second = alloc(eff_size);
  68         fs_read(fs->fat_start+fs->fat_size,eff_size,second);
  69     }
  70     else
  71         second = NULL;
  72     if (second && memcmp(first,second,eff_size) != 0) {
  73         FAT_ENTRY first_media, second_media;
  74         get_fat(&first_media,first,0,fs);
  75         get_fat(&second_media,second,0,fs);
  76         first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
  77         second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
  78         if (first_ok && !second_ok) {
  79             printf("FATs differ - using first FAT.\n");
  80             fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  81         }
  82         if (!first_ok && second_ok) {
  83             printf("FATs differ - using second FAT.\n");
  84             fs_write(fs->fat_start,eff_size,use = second);
  85         }
  86         if (first_ok && second_ok) {
  87             if (interactive) {
  88                 printf("FATs differ but appear to be intact. Use which FAT ?\n"
  89                   "1) Use first FAT\n2) Use second FAT\n");
  90                 if (get_key("12","?") == '1')
  91                     fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  92                 else fs_write(fs->fat_start,eff_size,use = second);
  93             }
  94             else {
  95                 printf("FATs differ but appear to be intact. Using first "
  96                   "FAT.\n");
  97                 fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  98             }
  99         }
 100         if (!first_ok && !second_ok) {
 101             printf("Both FATs appear to be corrupt. Giving up.\n");
 102             exit(1);
 103         }
 104     }
 105     fs->fat = qalloc(&mem_queue,sizeof(FAT_ENTRY)*(fs->clusters+2));
 106     for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],use,i,fs);
 107     for (i = 2; i < fs->clusters+2; i++)
 108         if (fs->fat[i].value >= fs->clusters+2 &&
 109             (fs->fat[i].value < FAT_MIN_BAD(fs))) {
 110             printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
 111                    i-2,fs->fat[i].value,fs->clusters+2-1);
 112             set_fat(fs,i,-1);
 113         }
 114     free(first);
 115     if (second)
 116         free(second);
 117 }
 118
 119
 120 void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
 121 {
 122     unsigned char data[4];
 123     int size;
 124     loff_t offs;
 125
 126     if ((long)new == -1)
 127         new = FAT_EOF(fs);
 128     else if ((long)new == -2)
 129         new = FAT_BAD(fs);
 130     switch( fs->fat_bits ) {
 131       case 12:
 132         offs = fs->fat_start+cluster*3/2;
 133         if (cluster & 1) {
 134             data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
 135             data[1] = new >> 4;
 136         }
 137         else {
 138             data[0] = new & 0xff;
 139             data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
 140               (0xff & fs->fat[cluster+1].value) << 4);
 141         }
 142         size = 2;
 143         break;
 144       case 16:
 145         offs = fs->fat_start+cluster*2;
 146         *(unsigned short *) data = CT_LE_W(new);
 147         size = 2;
 148         break;
 149       case 32:
 150         offs = fs->fat_start+cluster*4;
 151         /* According to M$, the high 4 bits of a FAT32 entry are reserved and
 152          * are not part of the cluster number. So we never touch them. */
 153         *(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
 154                                            (fs->fat[cluster].reserved << 28) );
 155         size = 4;
 156         break;
 157       default:
 158         die("Bad FAT entry size: %d bits.",fs->fat_bits);
 159     }
 160     fs->fat[cluster].value = new;
 161     fs_write(offs,size,&data);
 162     fs_write(offs+fs->fat_size,size,&data);
 163 }
 164
 165
 166 int bad_cluster(DOS_FS *fs,unsigned long cluster)
 167 {
 168     return FAT_IS_BAD(fs,fs->fat[cluster].value);
 169 }
 170
 171
 172 unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
 173 {
 174     unsigned long value;
 175
 176     value = fs->fat[cluster].value;
 177     if (FAT_IS_BAD(fs,value))
 178         die("Internal error: next_cluster on bad cluster");
 179     return FAT_IS_EOF(fs,value) ? -1 : value;
 180 }
 181
 182
 183 loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
 184 {
 185     return fs->data_start+((loff_t)cluster-2)*fs->cluster_size;
 186 }
 187
 188
 189 void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
 190 {
 191     if (owner && fs->fat[cluster].owner)
 192         die("Internal error: attempt to change file owner");
 193     fs->fat[cluster].owner = owner;
 194 }
 195
 196
 197 DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
 198 {
 199     return fs->fat[cluster].owner;
 200 }
 201
 202
 203 void fix_bad(DOS_FS *fs)
 204 {
 205     unsigned long i;
 206
 207     if (verbose)
 208         printf("Checking for bad clusters.\n");
 209     for (i = 2; i < fs->clusters+2; i++)
 210         if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
 211             if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
 212                 printf("Cluster %lu is unreadable.\n",i);
 213                 set_fat(fs,i,-2);
 214             }
 215 }
 216
 217
 218 void reclaim_free(DOS_FS *fs)
 219 {
 220     int reclaimed;
 221     unsigned long i;
 222
 223     if (verbose)
 224         printf("Checking for unused clusters.\n");
 225     reclaimed = 0;
 226     for (i = 2; i < fs->clusters+2; i++)
 227         if (!get_owner(fs,i) && fs->fat[i].value &&
 228             !FAT_IS_BAD(fs,fs->fat[i].value)) {
 229             set_fat(fs,i,0);
 230             reclaimed++;
 231         }
 232     if (reclaimed)
 233         printf("Reclaimed %d unused cluster%s (%d bytes).\n",reclaimed,
 234           reclaimed == 1 ?  "" : "s",reclaimed*fs->cluster_size);
 235 }
 236
 237
 238 static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
 239 {
 240     DOS_FILE *owner;
 241     int prev;
 242     unsigned long i,walk;
 243
 244     for (i = 2; i < fs->clusters+2; i++)
 245         if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
 246             !get_owner(fs,i) && !fs->fat[i].prev) {
 247             prev = 0;
 248             for (walk = i; walk > 0 && walk != -1;
 249                  walk = next_cluster(fs,walk)) {
 250                 if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
 251                 else if (owner != ptr)
 252                         die("Internal error: free chain collides with file");
 253                     else {
 254                         set_fat(fs,prev,-1);
 255                         break;
 256                     }
 257                 prev = walk;
 258             }
 259         }
 260 }
 261
 262
 263 void reclaim_file(DOS_FS *fs)
 264 {
 265     DOS_FILE dummy;
 266     int reclaimed,files,changed;
 267     unsigned long i,next,walk;
 268
 269     if (verbose)
 270         printf("Reclaiming unconnected clusters.\n");
 271     for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
 272     for (i = 2; i < fs->clusters+2; i++) {
 273         next = fs->fat[i].value;
 274         if (!get_owner(fs,i) && next && next < fs->clusters+2) {
 275             if (get_owner(fs,next) || !fs->fat[next].value ||
 276                 FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
 277             else fs->fat[next].prev++;
 278         }
 279     }
 280     do {
 281         tag_free(fs,&dummy);
 282         changed = 0;
 283         for (i = 2; i < fs->clusters+2; i++)
 284             if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
 285                 !get_owner(fs, i)) {
 286                 if (!fs->fat[fs->fat[i].value].prev--)
 287                     die("Internal error: prev going below zero");
 288                 set_fat(fs,i,-1);
 289                 changed = 1;
 290                 printf("Broke cycle at cluster %lu in free chain.\n",i);
 291                 break;
 292             }
 293     }
 294     while (changed);
 295     files = reclaimed = 0;
 296     for (i = 2; i < fs->clusters+2; i++)
 297         if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
 298             DIR_ENT de;
 299             loff_t offset;
 300             files++;
 301             offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
 302             de.start = CT_LE_W(i&0xffff);
 303             if (fs->fat_bits == 32)
 304                 de.starthi = CT_LE_W(i>>16);
 305             for (walk = i; walk > 0 && walk != -1;
 306                  walk = next_cluster(fs,walk)) {
 307                 de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
 308                 reclaimed++;
 309             }
 310             fs_write(offset,sizeof(DIR_ENT),&de);
 311         }
 312     if (reclaimed)
 313         printf("Reclaimed %d unused cluster%s (%d bytes) in %d chain%s.\n",
 314           reclaimed,reclaimed == 1 ? "" : "s",reclaimed*fs->cluster_size,files,
 315           files == 1 ? "" : "s");
 316 }
 317
 318
 319 unsigned long update_free(DOS_FS *fs)
 320 {
 321     unsigned long i;
 322     unsigned long free = 0;
 323     int do_set = 0;
 324
 325     for (i = 2; i < fs->clusters+2; i++)
 326         if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
 327             ++free;
 328
 329     if (!fs->fsinfo_start)
 330         return free;
 331
 332     if (verbose)
 333         printf("Checking free cluster summary.\n");
 334     if (fs->free_clusters >= 0) {
 335         if (free != fs->free_clusters) {
 336             printf( "Free cluster summary wrong (%ld vs. really %ld)\n",
 337                     fs->free_clusters,free);
 338             if (interactive)
 339                 printf( "1) Correct\n2) Don't correct\n" );
 340             else printf( "  Auto-correcting.\n" );
 341             if (!interactive || get_key("12","?") == '1')
 342                 do_set = 1;
 343         }
 344     }
 345     else {
 346         printf( "Free cluster summary uninitialized (should be %ld)\n", free );
 347         if (interactive)
 348             printf( "1) Set it\n2) Leave it uninitialized\n" );
 349         else printf( "  Auto-setting.\n" );
 350         if (!interactive || get_key("12","?") == '1')
 351             do_set = 1;
 352     }
 353
 354     if (do_set) {
 355         fs->free_clusters = free;
 356         free = CT_LE_L(free);
 357         fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
 358                  sizeof(free),&free);
 359     }
 360
 361     return free;
 362 }
 363
 364 /* Local Variables: */
 365 /* tab-width: 8     */
 366 /* End:             */