diff options
Diffstat (limited to 'fat.c')
-rw-r--r-- | fat.c | 705 |
1 files changed, 705 insertions, 0 deletions
@@ -0,0 +1,705 @@ +/* + * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank + * Copyright (c) 1995 Martin Husemann + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by Martin Husemann + * and Wolfgang Solfrank. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + + +#include <sys/cdefs.h> +#ifndef lint +__RCSID("$NetBSD: fat.c,v 1.12 2000/10/10 20:24:52 is Exp $"); +static const char rcsid[] = + "$FreeBSD: src/sbin/fsck_msdosfs/fat.c,v 1.9 2008/01/31 13:22:13 yar Exp $"; +#endif /* not lint */ + +#include <stdlib.h> +#include <string.h> +#include <ctype.h> +#include <stdio.h> +#include <unistd.h> + +#include "ext.h" +#include "fsutil.h" + +static int checkclnum(struct bootblock *, int, cl_t, cl_t *); +static int clustdiffer(cl_t, cl_t *, cl_t *, int); +static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *); +static int _readfat(int, struct bootblock *, int, u_char **); + +/*- + * The first 2 FAT entries contain pseudo-cluster numbers with the following + * layout: + * + * 31...... ........ ........ .......0 + * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0 + * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1 + * + * 11111111 mmmmmmmm FAT16 entry 0 + * sh111111 11111xxx FAT16 entry 1 + * + * r = reserved + * m = BPB media ID byte + * s = clean flag (1 = dismounted; 0 = still mounted) + * h = hard error flag (1 = ok; 0 = I/O error) + * x = any value ok + */ + +int +checkdirty(int fs, struct bootblock *boot) +{ + off_t off; + u_char *buffer; + int ret = 0; + + if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK) + return 0; + + off = boot->ResSectors; + off *= boot->BytesPerSec; + + buffer = malloc(boot->BytesPerSec); + if (buffer == NULL) { + perror("No space for FAT"); + return 1; + } + + if (lseek(fs, off, SEEK_SET) != off) { + perror("Unable to read FAT"); + goto err; + } + + if (read(fs, buffer, boot->BytesPerSec) != boot->BytesPerSec) { + perror("Unable to read FAT"); + goto err; + } + + /* + * If we don't understand the FAT, then the file system must be + * assumed to be unclean. + */ + if (buffer[0] != boot->Media || buffer[1] != 0xff) + goto err; + if (boot->ClustMask == CLUST16_MASK) { + if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f) + goto err; + } else { + if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f + || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff + || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03) + goto err; + } + + /* + * Now check the actual clean flag (and the no-error flag). + */ + if (boot->ClustMask == CLUST16_MASK) { + if ((buffer[3] & 0xc0) == 0xc0) + ret = 1; + } else { + if ((buffer[7] & 0x0c) == 0x0c) + ret = 1; + } + +err: + free(buffer); + return ret; +} + +/* + * Check a cluster number for valid value + */ +static int +checkclnum(struct bootblock *boot, int fat, cl_t cl, cl_t *next) +{ + if (*next >= (CLUST_RSRVD&boot->ClustMask)) + *next |= ~boot->ClustMask; + if (*next == CLUST_FREE) { + boot->NumFree++; + return FSOK; + } + if (*next == CLUST_BAD) { + boot->NumBad++; + return FSOK; + } + if (*next < CLUST_FIRST + || (*next >= boot->NumClusters && *next < CLUST_EOFS)) { + pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n", + cl, fat, + *next < CLUST_RSRVD ? "out of range" : "reserved", + *next&boot->ClustMask); + if (ask(1, "Truncate")) { + *next = CLUST_EOF; + return FSFATMOD; + } + return FSERROR; + } + return FSOK; +} + +/* + * Read a FAT from disk. Returns 1 if successful, 0 otherwise. + */ +static int +_readfat(int fs, struct bootblock *boot, int no, u_char **buffer) +{ + off_t off; + + printf("Attempting to allocate %u KB for FAT\n", + (boot->FATsecs * boot->BytesPerSec) / 1024); + + *buffer = malloc(boot->FATsecs * boot->BytesPerSec); + if (*buffer == NULL) { + perror("No space for FAT"); + return 0; + } + + off = boot->ResSectors + no * boot->FATsecs; + off *= boot->BytesPerSec; + + if (lseek(fs, off, SEEK_SET) != off) { + perror("Unable to read FAT"); + goto err; + } + + if (read(fs, *buffer, boot->FATsecs * boot->BytesPerSec) + != boot->FATsecs * boot->BytesPerSec) { + perror("Unable to read FAT"); + goto err; + } + + return 1; + + err: + free(*buffer); + return 0; +} + +/* + * Read a FAT and decode it into internal format + */ +int +readfat(int fs, struct bootblock *boot, int no, struct fatEntry **fp) +{ + struct fatEntry *fat; + u_char *buffer, *p; + cl_t cl; + int ret = FSOK; + + boot->NumFree = boot->NumBad = 0; + + if (!_readfat(fs, boot, no, &buffer)) + return FSFATAL; + + fat = calloc(boot->NumClusters, sizeof(struct fatEntry)); + if (fat == NULL) { + perror("No space for FAT"); + free(buffer); + return FSFATAL; + } + + if (buffer[0] != boot->Media + || buffer[1] != 0xff || buffer[2] != 0xff + || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff) + || (boot->ClustMask == CLUST32_MASK + && ((buffer[3]&0x0f) != 0x0f + || buffer[4] != 0xff || buffer[5] != 0xff + || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) { + + /* Windows 95 OSR2 (and possibly any later) changes + * the FAT signature to 0xXXffff7f for FAT16 and to + * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the + * file system is dirty if it doesn't reboot cleanly. + * Check this special condition before errorring out. + */ + if (buffer[0] == boot->Media && buffer[1] == 0xff + && buffer[2] == 0xff + && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f) + || (boot->ClustMask == CLUST32_MASK + && buffer[3] == 0x0f && buffer[4] == 0xff + && buffer[5] == 0xff && buffer[6] == 0xff + && buffer[7] == 0x07))) + ret |= FSDIRTY; + else { + /* just some odd byte sequence in FAT */ + + switch (boot->ClustMask) { + case CLUST32_MASK: + pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n", + "FAT starts with odd byte sequence", + buffer[0], buffer[1], buffer[2], buffer[3], + buffer[4], buffer[5], buffer[6], buffer[7]); + break; + case CLUST16_MASK: + pwarn("%s (%02x%02x%02x%02x)\n", + "FAT starts with odd byte sequence", + buffer[0], buffer[1], buffer[2], buffer[3]); + break; + default: + pwarn("%s (%02x%02x%02x)\n", + "FAT starts with odd byte sequence", + buffer[0], buffer[1], buffer[2]); + break; + } + + + if (ask(1, "Correct")) + ret |= FSFIXFAT; + } + } + switch (boot->ClustMask) { + case CLUST32_MASK: + p = buffer + 8; + break; + case CLUST16_MASK: + p = buffer + 4; + break; + default: + p = buffer + 3; + break; + } + for (cl = CLUST_FIRST; cl < boot->NumClusters;) { + switch (boot->ClustMask) { + case CLUST32_MASK: + fat[cl].next = p[0] + (p[1] << 8) + + (p[2] << 16) + (p[3] << 24); + fat[cl].next &= boot->ClustMask; + ret |= checkclnum(boot, no, cl, &fat[cl].next); + cl++; + p += 4; + break; + case CLUST16_MASK: + fat[cl].next = p[0] + (p[1] << 8); + ret |= checkclnum(boot, no, cl, &fat[cl].next); + cl++; + p += 2; + break; + default: + fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff; + ret |= checkclnum(boot, no, cl, &fat[cl].next); + cl++; + if (cl >= boot->NumClusters) + break; + fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff; + ret |= checkclnum(boot, no, cl, &fat[cl].next); + cl++; + p += 3; + break; + } + } + + free(buffer); + *fp = fat; + return ret; +} + +/* + * Get type of reserved cluster + */ +char * +rsrvdcltype(cl_t cl) +{ + if (cl == CLUST_FREE) + return "free"; + if (cl < CLUST_BAD) + return "reserved"; + if (cl > CLUST_BAD) + return "as EOF"; + return "bad"; +} + +static int +clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, int fatnum) +{ + if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) { + if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { + if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD + && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD) + || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) { + pwarn("Cluster %u is marked %s with different indicators\n", + cl, rsrvdcltype(*cp1)); + if (ask(1, "Fix")) { + *cp2 = *cp1; + return FSFATMOD; + } + return FSFATAL; + } + pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %d\n", + cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum); + if (ask(0, "Use FAT 0's entry")) { + *cp2 = *cp1; + return FSFATMOD; + } + if (ask(0, "Use FAT %d's entry", fatnum)) { + *cp1 = *cp2; + return FSFATMOD; + } + return FSFATAL; + } + pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n", + cl, rsrvdcltype(*cp1), *cp2, fatnum); + if (ask(0, "Use continuation from FAT %d", fatnum)) { + *cp1 = *cp2; + return FSFATMOD; + } + if (ask(0, "Use mark from FAT 0")) { + *cp2 = *cp1; + return FSFATMOD; + } + return FSFATAL; + } + if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) { + pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %d\n", + cl, *cp1, rsrvdcltype(*cp2), fatnum); + if (ask(0, "Use continuation from FAT 0")) { + *cp2 = *cp1; + return FSFATMOD; + } + if (ask(0, "Use mark from FAT %d", fatnum)) { + *cp1 = *cp2; + return FSFATMOD; + } + return FSERROR; + } + pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %d\n", + cl, *cp1, *cp2, fatnum); + if (ask(0, "Use continuation from FAT 0")) { + *cp2 = *cp1; + return FSFATMOD; + } + if (ask(0, "Use continuation from FAT %d", fatnum)) { + *cp1 = *cp2; + return FSFATMOD; + } + return FSERROR; +} + +/* + * Compare two FAT copies in memory. Resolve any conflicts and merge them + * into the first one. + */ +int +comparefat(struct bootblock *boot, struct fatEntry *first, + struct fatEntry *second, int fatnum) +{ + cl_t cl; + int ret = FSOK; + + for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) + if (first[cl].next != second[cl].next) + ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum); + return ret; +} + +void +clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head) +{ + cl_t p, q; + + for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) { + if (fat[p].head != head) + break; + q = fat[p].next; + fat[p].next = fat[p].head = CLUST_FREE; + fat[p].length = 0; + } +} + +int +tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *trunc) +{ + if (ask(1, "Clear chain starting at %u", head)) { + clearchain(boot, fat, head); + return FSFATMOD; + } else if (ask(1, "Truncate")) { + *trunc = CLUST_EOF; + return FSFATMOD; + } else + return FSERROR; +} + +/* + * Check a complete FAT in-memory for crosslinks + */ +int +checkfat(struct bootblock *boot, struct fatEntry *fat) +{ + cl_t head, p, h, n; + u_int len; + int ret = 0; + int conf; + + /* + * pass 1: figure out the cluster chains. + */ + for (head = CLUST_FIRST; head < boot->NumClusters; head++) { + /* find next untravelled chain */ + if (fat[head].head != 0 /* cluster already belongs to some chain */ + || fat[head].next == CLUST_FREE + || fat[head].next == CLUST_BAD) + continue; /* skip it. */ + + /* follow the chain and mark all clusters on the way */ + for (len = 0, p = head; + p >= CLUST_FIRST && p < boot->NumClusters; + p = fat[p].next) { + fat[p].head = head; + len++; + } + + /* the head record gets the length */ + fat[head].length = fat[head].next == CLUST_FREE ? 0 : len; + } + + /* + * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because + * we didn't know the real start of the chain then - would have treated partial + * chains as interlinked with their main chain) + */ + for (head = CLUST_FIRST; head < boot->NumClusters; head++) { + /* find next untravelled chain */ + if (fat[head].head != head) + continue; + + /* follow the chain to its end (hopefully) */ + for (p = head; + (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters; + p = n) + if (fat[n].head != head) + break; + if (n >= CLUST_EOFS) + continue; + + if (n == CLUST_FREE || n >= CLUST_RSRVD) { + pwarn("Cluster chain starting at %u ends with cluster marked %s\n", + head, rsrvdcltype(n)); + ret |= tryclear(boot, fat, head, &fat[p].next); + continue; + } + if (n < CLUST_FIRST || n >= boot->NumClusters) { + pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n", + head, n); + ret |= tryclear(boot, fat, head, &fat[p].next); + continue; + } + pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n", + head, fat[n].head, n); + conf = tryclear(boot, fat, head, &fat[p].next); + if (ask(1, "Clear chain starting at %u", h = fat[n].head)) { + if (conf == FSERROR) { + /* + * Transfer the common chain to the one not cleared above. + */ + for (p = n; + p >= CLUST_FIRST && p < boot->NumClusters; + p = fat[p].next) { + if (h != fat[p].head) { + /* + * Have to reexamine this chain. + */ + head--; + break; + } + fat[p].head = head; + } + } + clearchain(boot, fat, h); + conf |= FSFATMOD; + } + ret |= conf; + } + + return ret; +} + +/* + * Write out FATs encoding them from the internal format + */ +int +writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat) +{ + u_char *buffer, *p; + cl_t cl; + int i; + u_int32_t fatsz; + off_t off; + int ret = FSOK; + + buffer = malloc(fatsz = boot->FATsecs * boot->BytesPerSec); + if (buffer == NULL) { + perror("No space for FAT"); + return FSFATAL; + } + memset(buffer, 0, fatsz); + boot->NumFree = 0; + p = buffer; + if (correct_fat) { + *p++ = (u_char)boot->Media; + *p++ = 0xff; + *p++ = 0xff; + switch (boot->ClustMask) { + case CLUST16_MASK: + *p++ = 0xff; + break; + case CLUST32_MASK: + *p++ = 0x0f; + *p++ = 0xff; + *p++ = 0xff; + *p++ = 0xff; + *p++ = 0x0f; + break; + } + } else { + /* use same FAT signature as the old FAT has */ + int count; + u_char *old_fat; + + switch (boot->ClustMask) { + case CLUST32_MASK: + count = 8; + break; + case CLUST16_MASK: + count = 4; + break; + default: + count = 3; + break; + } + + if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0, + &old_fat)) { + free(buffer); + return FSFATAL; + } + + memcpy(p, old_fat, count); + free(old_fat); + p += count; + } + + for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) { + switch (boot->ClustMask) { + case CLUST32_MASK: + if (fat[cl].next == CLUST_FREE) + boot->NumFree++; + *p++ = (u_char)fat[cl].next; + *p++ = (u_char)(fat[cl].next >> 8); + *p++ = (u_char)(fat[cl].next >> 16); + *p &= 0xf0; + *p++ |= (fat[cl].next >> 24)&0x0f; + break; + case CLUST16_MASK: + if (fat[cl].next == CLUST_FREE) + boot->NumFree++; + *p++ = (u_char)fat[cl].next; + *p++ = (u_char)(fat[cl].next >> 8); + break; + default: + if (fat[cl].next == CLUST_FREE) + boot->NumFree++; + if (cl + 1 < boot->NumClusters + && fat[cl + 1].next == CLUST_FREE) + boot->NumFree++; + *p++ = (u_char)fat[cl].next; + *p++ = (u_char)((fat[cl].next >> 8) & 0xf) + |(u_char)(fat[cl+1].next << 4); + *p++ = (u_char)(fat[++cl].next >> 4); + break; + } + } + for (i = 0; i < boot->FATs; i++) { + off = boot->ResSectors + i * boot->FATsecs; + off *= boot->BytesPerSec; + if (lseek(fs, off, SEEK_SET) != off + || write(fs, buffer, fatsz) != fatsz) { + perror("Unable to write FAT"); + ret = FSFATAL; /* Return immediately? XXX */ + } + } + free(buffer); + return ret; +} + +/* + * Check a complete in-memory FAT for lost cluster chains + */ +int +checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat) +{ + cl_t head; + int mod = FSOK; + int ret; + + for (head = CLUST_FIRST; head < boot->NumClusters; head++) { + /* find next untravelled chain */ + if (fat[head].head != head + || fat[head].next == CLUST_FREE + || (fat[head].next >= CLUST_RSRVD + && fat[head].next < CLUST_EOFS) + || (fat[head].flags & FAT_USED)) + continue; + + pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n", + head, fat[head].length); + mod |= ret = reconnect(dosfs, boot, fat, head); + if (mod & FSFATAL) + break; + if (ret == FSERROR && ask(1, "Clear")) { + clearchain(boot, fat, head); + mod |= FSFATMOD; + } + } + finishlf(); + + if (boot->FSInfo) { + ret = 0; + if (boot->FSFree != boot->NumFree) { + pwarn("Free space in FSInfo block (%d) not correct (%d)\n", + boot->FSFree, boot->NumFree); + if (ask(1, "Fix")) { + boot->FSFree = boot->NumFree; + ret = 1; + } + } + if (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE) { + pwarn("Next free cluster in FSInfo block (%u) not free\n", + boot->FSNext); + if (ask(1, "Fix")) + for (head = CLUST_FIRST; head < boot->NumClusters; head++) + if (fat[head].next == CLUST_FREE) { + boot->FSNext = head; + ret = 1; + break; + } + } + if (ret) + mod |= writefsinfo(dosfs, boot); + } + + return mod; +} |