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- /* fat.c - Read/write access to the FAT
- Copyright (C) 1993 Werner Almesberger <werner.almesberger@lrc.di.epfl.ch>
- Copyright (C) 1998 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
- Copyright (C) 2008-2013 Daniel Baumann <mail@daniel-baumann.ch>
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
- On Debian systems, the complete text of the GNU General Public License
- can be found in /usr/share/common-licenses/GPL-3 file.
- */
- /* FAT32, VFAT, Atari format support, and various fixes additions May 1998
- * by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
- #include "common.h"
- #include "dosfsck.h"
- #include "io.h"
- #include "check.h"
- #include "fat.h"
- /**
- * Fetch the FAT entry for a specified cluster.
- *
- * @param[out] entry Cluster to which cluster of interest is linked
- * @param[in] fat FAT table for the partition
- * @param[in] cluster Cluster of interest
- * @param[in] fs Information from the FAT boot sectors (bits per FAT entry)
- */
- void get_fat(FAT_ENTRY * entry, void *fat, unsigned long cluster, DOS_FS * fs)
- {
- unsigned char *ptr;
- switch (fs->fat_bits) {
- case 12:
- ptr = &((unsigned char *)fat)[cluster * 3 / 2];
- entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
- (ptr[0] | ptr[1] << 8));
- break;
- case 16:
- entry->value = CF_LE_W(((unsigned short *)fat)[cluster]);
- break;
- case 32:
- /* According to M$, the high 4 bits of a FAT32 entry are reserved and
- * are not part of the cluster number. So we cut them off. */
- {
- unsigned long e = CF_LE_L(((unsigned int *)fat)[cluster]);
- entry->value = e & 0xfffffff;
- entry->reserved = e >> 28;
- }
- break;
- default:
- die("Bad FAT entry size: %d bits.", fs->fat_bits);
- }
- }
- /**
- * Build a bookkeeping structure from the partition's FAT table.
- * If the partition has multiple FATs and they don't agree, try to pick a winner,
- * and queue a command to overwrite the loser.
- * One error that is fixed here is a cluster that links to something out of range.
- *
- * @param[inout] fs Information about the filesystem
- */
- void read_fat(DOS_FS * fs)
- {
- int eff_size;
- unsigned long i;
- void *first, *second = NULL;
- int first_ok, second_ok;
- unsigned long total_num_clusters;
- /* Clean up from previous pass */
- if (fs->fat)
- free(fs->fat);
- if (fs->cluster_owner)
- free(fs->cluster_owner);
- fs->fat = NULL;
- fs->cluster_owner = NULL;
- total_num_clusters = fs->clusters + 2UL;
- eff_size = (total_num_clusters * fs->fat_bits + 7) / 8ULL;
- first = alloc(eff_size);
- fs_read(fs->fat_start, eff_size, first);
- if (fs->nfats > 1) {
- second = alloc(eff_size);
- fs_read(fs->fat_start + fs->fat_size, eff_size, second);
- }
- if (second && memcmp(first, second, eff_size) != 0) {
- FAT_ENTRY first_media, second_media;
- get_fat(&first_media, first, 0, fs);
- get_fat(&second_media, second, 0, fs);
- first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
- second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
- if (first_ok && !second_ok) {
- printf("FATs differ - using first FAT.\n");
- fs_write(fs->fat_start + fs->fat_size, eff_size, first);
- }
- if (!first_ok && second_ok) {
- printf("FATs differ - using second FAT.\n");
- fs_write(fs->fat_start, eff_size, second);
- memcpy(first, second, eff_size);
- }
- if (first_ok && second_ok) {
- if (interactive) {
- printf("FATs differ but appear to be intact. Use which FAT ?\n"
- "1) Use first FAT\n2) Use second FAT\n");
- if (get_key("12", "?") == '1') {
- fs_write(fs->fat_start + fs->fat_size, eff_size, first);
- } else {
- fs_write(fs->fat_start, eff_size, second);
- memcpy(first, second, eff_size);
- }
- } else {
- printf("FATs differ but appear to be intact. Using first "
- "FAT.\n");
- fs_write(fs->fat_start + fs->fat_size, eff_size, first);
- }
- }
- if (!first_ok && !second_ok) {
- printf("Both FATs appear to be corrupt. Giving up.\n");
- exit(1);
- }
- }
- if (second) {
- free(second);
- }
- fs->fat = (unsigned char *)first;
- fs->cluster_owner = alloc(total_num_clusters * sizeof(DOS_FILE *));
- memset(fs->cluster_owner, 0, (total_num_clusters * sizeof(DOS_FILE *)));
- /* Truncate any cluster chains that link to something out of range */
- for (i = 2; i < fs->clusters + 2; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- if (curEntry.value == 1) {
- printf("Cluster %ld out of range (1). Setting to EOF.\n", i - 2);
- set_fat(fs, i, -1);
- }
- if (curEntry.value >= fs->clusters + 2 &&
- (curEntry.value < FAT_MIN_BAD(fs))) {
- printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
- i - 2, curEntry.value, fs->clusters + 2 - 1);
- set_fat(fs, i, -1);
- }
- }
- }
- /**
- * Update the FAT entry for a specified cluster
- * (i.e., change the cluster it links to).
- * Queue a command to write out this change.
- *
- * @param[in,out] fs Information about the filesystem
- * @param[in] cluster Cluster to change
- * @param[in] new Cluster to link to
- * Special values:
- * 0 == free cluster
- * -1 == end-of-chain
- * -2 == bad cluster
- */
- void set_fat(DOS_FS * fs, unsigned long cluster, unsigned long new)
- {
- unsigned char *data = NULL;
- int size;
- loff_t offs;
- if ((long)new == -1)
- new = FAT_EOF(fs);
- else if ((long)new == -2)
- new = FAT_BAD(fs);
- switch (fs->fat_bits) {
- case 12:
- data = fs->fat + cluster * 3 / 2;
- offs = fs->fat_start + cluster * 3 / 2;
- if (cluster & 1) {
- FAT_ENTRY prevEntry;
- get_fat(&prevEntry, fs->fat, cluster - 1, fs);
- data[0] = ((new & 0xf) << 4) | (prevEntry.value >> 8);
- data[1] = new >> 4;
- } else {
- FAT_ENTRY subseqEntry;
- get_fat(&subseqEntry, fs->fat, cluster + 1, fs);
- data[0] = new & 0xff;
- data[1] = (new >> 8) | (cluster == fs->clusters - 1 ? 0 :
- (0xff & subseqEntry.value) << 4);
- }
- size = 2;
- break;
- case 16:
- data = fs->fat + cluster * 2;
- offs = fs->fat_start + cluster * 2;
- *(unsigned short *)data = CT_LE_W(new);
- size = 2;
- break;
- case 32:
- {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, cluster, fs);
- data = fs->fat + cluster * 4;
- offs = fs->fat_start + cluster * 4;
- /* According to M$, the high 4 bits of a FAT32 entry are reserved and
- * are not part of the cluster number. So we never touch them. */
- *(unsigned long *)data = CT_LE_L((new & 0xfffffff) |
- (curEntry.reserved << 28));
- size = 4;
- }
- break;
- default:
- die("Bad FAT entry size: %d bits.", fs->fat_bits);
- }
- fs_write(offs, size, data);
- if (fs->nfats > 1) {
- fs_write(offs + fs->fat_size, size, data);
- }
- }
- int bad_cluster(DOS_FS * fs, unsigned long cluster)
- {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, cluster, fs);
- return FAT_IS_BAD(fs, curEntry.value);
- }
- /**
- * Get the cluster to which the specified cluster is linked.
- * If the linked cluster is marked bad, abort.
- *
- * @param[in] fs Information about the filesystem
- * @param[in] cluster Cluster to follow
- *
- * @return -1 'cluster' is at the end of the chain
- * @return Other values Next cluster in this chain
- */
- unsigned long next_cluster(DOS_FS * fs, unsigned long cluster)
- {
- unsigned long value;
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, cluster, fs);
- value = curEntry.value;
- if (FAT_IS_BAD(fs, value))
- die("Internal error: next_cluster on bad cluster");
- return FAT_IS_EOF(fs, value) ? -1 : value;
- }
- loff_t cluster_start(DOS_FS * fs, unsigned long cluster)
- {
- return fs->data_start + ((loff_t) cluster -
- 2) * (unsigned long long)fs->cluster_size;
- }
- /**
- * Update internal bookkeeping to show that the specified cluster belongs
- * to the specified dentry.
- *
- * @param[in,out] fs Information about the filesystem
- * @param[in] cluster Cluster being assigned
- * @param[in] owner Information on dentry that owns this cluster
- * (may be NULL)
- */
- void set_owner(DOS_FS * fs, unsigned long cluster, DOS_FILE * owner)
- {
- if (fs->cluster_owner == NULL)
- die("Internal error: attempt to set owner in non-existent table");
- if (owner && fs->cluster_owner[cluster]
- && (fs->cluster_owner[cluster] != owner))
- die("Internal error: attempt to change file owner");
- fs->cluster_owner[cluster] = owner;
- }
- DOS_FILE *get_owner(DOS_FS * fs, unsigned long cluster)
- {
- if (fs->cluster_owner == NULL)
- return NULL;
- else
- return fs->cluster_owner[cluster];
- }
- void fix_bad(DOS_FS * fs)
- {
- unsigned long i;
- if (verbose)
- printf("Checking for bad clusters.\n");
- for (i = 2; i < fs->clusters + 2; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- if (!get_owner(fs, i) && !FAT_IS_BAD(fs, curEntry.value))
- if (!fs_test(cluster_start(fs, i), fs->cluster_size)) {
- printf("Cluster %lu is unreadable.\n", i);
- set_fat(fs, i, -2);
- }
- }
- }
- void reclaim_free(DOS_FS * fs)
- {
- int reclaimed;
- unsigned long i;
- if (verbose)
- printf("Checking for unused clusters.\n");
- reclaimed = 0;
- for (i = 2; i < fs->clusters + 2; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- if (!get_owner(fs, i) && curEntry.value &&
- !FAT_IS_BAD(fs, curEntry.value)) {
- set_fat(fs, i, 0);
- reclaimed++;
- }
- }
- if (reclaimed)
- printf("Reclaimed %d unused cluster%s (%llu bytes).\n", reclaimed,
- reclaimed == 1 ? "" : "s",
- (unsigned long long)reclaimed * fs->cluster_size);
- }
- /**
- * Assign the specified owner to all orphan chains (except cycles).
- * Break cross-links between orphan chains.
- *
- * @param[in,out] fs Information about the filesystem
- * @param[in] owner dentry to be assigned ownership of orphans
- * @param[in,out] num_refs For each orphan cluster [index], how many
- * clusters link to it.
- * @param[in] start_cluster Where to start scanning for orphans
- */
- static void tag_free(DOS_FS * fs, DOS_FILE * owner, unsigned long *num_refs,
- unsigned long start_cluster)
- {
- int prev;
- unsigned long i, walk;
- if (start_cluster == 0)
- start_cluster = 2;
- for (i = start_cluster; i < fs->clusters + 2; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- /* If the current entry is the head of an un-owned chain... */
- if (curEntry.value && !FAT_IS_BAD(fs, curEntry.value) &&
- !get_owner(fs, i) && !num_refs[i]) {
- prev = 0;
- /* Walk the chain, claiming ownership as we go */
- for (walk = i; walk != -1; walk = next_cluster(fs, walk)) {
- if (!get_owner(fs, walk)) {
- set_owner(fs, walk, owner);
- } else {
- /* We've run into cross-links between orphaned chains,
- * or a cycle with a tail.
- * Terminate this orphan chain (break the link)
- */
- set_fat(fs, prev, -1);
- /* This is not necessary because 'walk' is owned and thus
- * will never become the head of a chain (the only case
- * that would matter during reclaim to files).
- * It's easier to decrement than to prove that it's
- * unnecessary.
- */
- num_refs[walk]--;
- break;
- }
- prev = walk;
- }
- }
- }
- }
- /**
- * Recover orphan chains to files, handling any cycles or cross-links.
- *
- * @param[in,out] fs Information about the filesystem
- */
- void reclaim_file(DOS_FS * fs)
- {
- DOS_FILE orphan;
- int reclaimed, files;
- int changed = 0;
- unsigned long i, next, walk;
- unsigned long *num_refs = NULL; /* Only for orphaned clusters */
- unsigned long total_num_clusters;
- if (verbose)
- printf("Reclaiming unconnected clusters.\n");
- total_num_clusters = fs->clusters + 2UL;
- num_refs = alloc(total_num_clusters * sizeof(unsigned long));
- memset(num_refs, 0, (total_num_clusters * sizeof(unsigned long)));
- /* Guarantee that all orphan chains (except cycles) end cleanly
- * with an end-of-chain mark.
- */
- for (i = 2; i < total_num_clusters; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- next = curEntry.value;
- if (!get_owner(fs, i) && next && next < fs->clusters + 2) {
- /* Cluster is linked, but not owned (orphan) */
- FAT_ENTRY nextEntry;
- get_fat(&nextEntry, fs->fat, next, fs);
- /* Mark it end-of-chain if it links into an owned cluster,
- * a free cluster, or a bad cluster.
- */
- if (get_owner(fs, next) || !nextEntry.value ||
- FAT_IS_BAD(fs, nextEntry.value))
- set_fat(fs, i, -1);
- else
- num_refs[next]++;
- }
- }
- /* Scan until all the orphans are accounted for,
- * and all cycles and cross-links are broken
- */
- do {
- tag_free(fs, &orphan, num_refs, changed);
- changed = 0;
- /* Any unaccounted-for orphans must be part of a cycle */
- for (i = 2; i < total_num_clusters; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- if (curEntry.value && !FAT_IS_BAD(fs, curEntry.value) &&
- !get_owner(fs, i)) {
- if (!num_refs[curEntry.value]--)
- die("Internal error: num_refs going below zero");
- set_fat(fs, i, -1);
- changed = curEntry.value;
- printf("Broke cycle at cluster %lu in free chain.\n", i);
- /* If we've created a new chain head,
- * tag_free() can claim it
- */
- if (num_refs[curEntry.value] == 0)
- break;
- }
- }
- }
- while (changed);
- /* Now we can start recovery */
- files = reclaimed = 0;
- for (i = 2; i < total_num_clusters; i++)
- /* If this cluster is the head of an orphan chain... */
- if (get_owner(fs, i) == &orphan && !num_refs[i]) {
- DIR_ENT de;
- loff_t offset;
- files++;
- offset = alloc_rootdir_entry(fs, &de, "FSCK%04d");
- de.start = CT_LE_W(i & 0xffff);
- if (fs->fat_bits == 32)
- de.starthi = CT_LE_W(i >> 16);
- for (walk = i; walk > 0 && walk != -1;
- walk = next_cluster(fs, walk)) {
- de.size = CT_LE_L(CF_LE_L(de.size) + fs->cluster_size);
- reclaimed++;
- }
- fs_write(offset, sizeof(DIR_ENT), &de);
- }
- if (reclaimed)
- printf("Reclaimed %d unused cluster%s (%llu bytes) in %d chain%s.\n",
- reclaimed, reclaimed == 1 ? "" : "s",
- (unsigned long long)reclaimed * fs->cluster_size, files,
- files == 1 ? "" : "s");
- free(num_refs);
- }
- unsigned long update_free(DOS_FS * fs)
- {
- unsigned long i;
- unsigned long free = 0;
- int do_set = 0;
- for (i = 2; i < fs->clusters + 2; i++) {
- FAT_ENTRY curEntry;
- get_fat(&curEntry, fs->fat, i, fs);
- if (!get_owner(fs, i) && !FAT_IS_BAD(fs, curEntry.value))
- ++free;
- }
- if (!fs->fsinfo_start)
- return free;
- if (verbose)
- printf("Checking free cluster summary.\n");
- if (fs->free_clusters != 0xFFFFFFFF) {
- if (free != fs->free_clusters) {
- printf("Free cluster summary wrong (%ld vs. really %ld)\n",
- fs->free_clusters, free);
- if (interactive)
- printf("1) Correct\n2) Don't correct\n");
- else
- printf(" Auto-correcting.\n");
- if (!interactive || get_key("12", "?") == '1')
- do_set = 1;
- }
- } else {
- printf("Free cluster summary uninitialized (should be %ld)\n", free);
- if (rw) {
- if (interactive)
- printf("1) Set it\n2) Leave it uninitialized\n");
- else
- printf(" Auto-setting.\n");
- if (!interactive || get_key("12", "?") == '1')
- do_set = 1;
- }
- }
- if (do_set) {
- unsigned long le_free = CT_LE_L(free);
- fs->free_clusters = free;
- fs_write(fs->fsinfo_start + offsetof(struct info_sector, free_clusters),
- sizeof(le_free), &le_free);
- }
- return free;
- }
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