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-rw-r--r--dosfstools/src/fat.c547
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diff --git a/dosfstools/src/fat.c b/dosfstools/src/fat.c
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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>
+
+ 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 */
+ free(fs->fat);
+ 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;
+}