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- /* boot.c - Read and analyze ia PC/MS-DOS boot sector
- 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 <string.h>
- #include <sys/types.h>
- #include <stdlib.h>
- #include <time.h>
- #include "common.h"
- #include "dosfsck.h"
- #include "fat.h"
- #include "io.h"
- #include "boot.h"
- #define ROUND_TO_MULTIPLE(n,m) ((n) && (m) ? (n)+(m)-1-((n)-1)%(m) : 0)
- /* don't divide by zero */
- /* cut-over cluster counts for FAT12 and FAT16 */
- #define FAT12_THRESHOLD 4085
- #define FAT16_THRESHOLD 65525
- static struct {
- __u8 media;
- char *descr;
- } mediabytes[] = {
- { 0xf0, "5.25\" or 3.5\" HD floppy" },
- { 0xf8, "hard disk" },
- { 0xf9, "3,5\" 720k floppy 2s/80tr/9sec or "
- "5.25\" 1.2M floppy 2s/80tr/15sec" },
- { 0xfa, "5.25\" 320k floppy 1s/80tr/8sec" },
- { 0xfb, "3.5\" 640k floppy 2s/80tr/8sec" },
- { 0xfc, "5.25\" 180k floppy 1s/40tr/9sec" },
- { 0xfd, "5.25\" 360k floppy 2s/40tr/9sec" },
- { 0xfe, "5.25\" 160k floppy 1s/40tr/8sec" },
- { 0xff, "5.25\" 320k floppy 2s/40tr/8sec" },
- };
- #if defined __alpha || defined __arm || defined __arm__ || defined __ia64__ || defined __s390x__ \
- || defined __x86_64__ || defined __ppc64__ || defined __bfin__ \
- || defined __MICROBLAZE__
- /* Unaligned fields must first be copied byte-wise */
- #define GET_UNALIGNED_W(f) \
- ({ \
- unsigned short __v; \
- memcpy( &__v, &f, sizeof(__v) ); \
- CF_LE_W( *(unsigned short *)&__v ); \
- })
- #else
- #define GET_UNALIGNED_W(f) CF_LE_W( *(unsigned short *)&f )
- #endif
- static char *get_media_descr( unsigned char media )
- {
- int i;
- for( i = 0; i < sizeof(mediabytes)/sizeof(*mediabytes); ++i ) {
- if (mediabytes[i].media == media)
- return( mediabytes[i].descr );
- }
- return( "undefined" );
- }
- static void dump_boot(DOS_FS *fs,struct boot_sector *b,unsigned lss)
- {
- unsigned short sectors;
- printf("Boot sector contents:\n");
- if (!atari_format) {
- char id[9];
- strncpy(id,b->system_id,8);
- id[8] = 0;
- printf("System ID \"%s\"\n",id);
- }
- else {
- /* On Atari, a 24 bit serial number is stored at offset 8 of the boot
- * sector */
- printf("Serial number 0x%x\n",
- b->system_id[5] | (b->system_id[6]<<8) | (b->system_id[7]<<16));
- }
- printf("Media byte 0x%02x (%s)\n",b->media,get_media_descr(b->media));
- printf("%10d bytes per logical sector\n",GET_UNALIGNED_W(b->sector_size));
- printf("%10d bytes per cluster\n",fs->cluster_size);
- printf("%10d reserved sector%s\n",CF_LE_W(b->reserved),
- CF_LE_W(b->reserved) == 1 ? "" : "s");
- printf("First FAT starts at byte %llu (sector %llu)\n",
- (unsigned long long)fs->fat_start,
- (unsigned long long)fs->fat_start/lss);
- printf("%10d FATs, %d bit entries\n",b->fats,fs->fat_bits);
- printf("%10d bytes per FAT (= %u sectors)\n",fs->fat_size,
- fs->fat_size/lss);
- if (!fs->root_cluster) {
- printf("Root directory starts at byte %llu (sector %llu)\n",
- (unsigned long long)fs->root_start,
- (unsigned long long)fs->root_start/lss);
- printf("%10d root directory entries\n",fs->root_entries);
- }
- else {
- printf( "Root directory start at cluster %lu (arbitrary size)\n",
- fs->root_cluster);
- }
- printf("Data area starts at byte %llu (sector %llu)\n",
- (unsigned long long)fs->data_start,
- (unsigned long long)fs->data_start/lss);
- printf("%10lu data clusters (%llu bytes)\n",fs->clusters,
- (unsigned long long)fs->clusters*fs->cluster_size);
- printf("%u sectors/track, %u heads\n",CF_LE_W(b->secs_track),
- CF_LE_W(b->heads));
- printf("%10u hidden sectors\n",
- atari_format ?
- /* On Atari, the hidden field is only 16 bit wide and unused */
- (((unsigned char *)&b->hidden)[0] |
- ((unsigned char *)&b->hidden)[1] << 8) :
- CF_LE_L(b->hidden));
- sectors = GET_UNALIGNED_W( b->sectors );
- printf("%10u sectors total\n", sectors ? sectors : CF_LE_L(b->total_sect));
- }
- static void check_backup_boot(DOS_FS *fs, struct boot_sector *b, int lss)
- {
- struct boot_sector b2;
- if (!fs->backupboot_start) {
- printf( "There is no backup boot sector.\n" );
- if (CF_LE_W(b->reserved) < 3) {
- printf( "And there is no space for creating one!\n" );
- return;
- }
- if (interactive)
- printf( "1) Create one\n2) Do without a backup\n" );
- else printf( " Auto-creating backup boot block.\n" );
- if (!interactive || get_key("12","?") == '1') {
- int bbs;
- /* The usual place for the backup boot sector is sector 6. Choose
- * that or the last reserved sector. */
- if (CF_LE_W(b->reserved) >= 7 && CF_LE_W(b->info_sector) != 6)
- bbs = 6;
- else {
- bbs = CF_LE_W(b->reserved) - 1;
- if (bbs == CF_LE_W(b->info_sector))
- --bbs; /* this is never 0, as we checked reserved >= 3! */
- }
- fs->backupboot_start = bbs*lss;
- b->backup_boot = CT_LE_W(bbs);
- fs_write(fs->backupboot_start,sizeof(*b),b);
- fs_write((loff_t)offsetof(struct boot_sector,backup_boot),
- sizeof(b->backup_boot),&b->backup_boot);
- printf( "Created backup of boot sector in sector %d\n", bbs );
- return;
- }
- else return;
- }
- fs_read(fs->backupboot_start,sizeof(b2),&b2);
- if (memcmp(b,&b2,sizeof(b2)) != 0) {
- /* there are any differences */
- __u8 *p, *q;
- int i, pos, first = 1;
- char buf[20];
- printf( "There are differences between boot sector and its backup.\n" );
- printf( "Differences: (offset:original/backup)\n " );
- pos = 2;
- for( p = (__u8 *)b, q = (__u8 *)&b2, i = 0; i < sizeof(b2);
- ++p, ++q, ++i ) {
- if (*p != *q) {
- sprintf( buf, "%s%u:%02x/%02x", first ? "" : ", ",
- (unsigned)(p-(__u8 *)b), *p, *q );
- if (pos + strlen(buf) > 78) printf( "\n " ), pos = 2;
- printf( "%s", buf );
- pos += strlen(buf);
- first = 0;
- }
- }
- printf( "\n" );
- if (interactive)
- printf( "1) Copy original to backup\n"
- "2) Copy backup to original\n"
- "3) No action\n" );
- else printf( " Not automatically fixing this.\n" );
- switch (interactive ? get_key("123","?") : '3') {
- case '1':
- fs_write(fs->backupboot_start,sizeof(*b),b);
- break;
- case '2':
- fs_write(0,sizeof(b2),&b2);
- break;
- default:
- break;
- }
- }
- }
- static void init_fsinfo(struct info_sector *i)
- {
- i->magic = CT_LE_L(0x41615252);
- i->signature = CT_LE_L(0x61417272);
- i->free_clusters = CT_LE_L(-1);
- i->next_cluster = CT_LE_L(2);
- i->boot_sign = CT_LE_W(0xaa55);
- }
- static void read_fsinfo(DOS_FS *fs, struct boot_sector *b,int lss)
- {
- struct info_sector i;
- if (!b->info_sector) {
- printf( "No FSINFO sector\n" );
- if (interactive)
- printf( "1) Create one\n2) Do without FSINFO\n" );
- else printf( " Not automatically creating it.\n" );
- if (interactive && get_key("12","?") == '1') {
- /* search for a free reserved sector (not boot sector and not
- * backup boot sector) */
- __u32 s;
- for( s = 1; s < CF_LE_W(b->reserved); ++s )
- if (s != CF_LE_W(b->backup_boot)) break;
- if (s > 0 && s < CF_LE_W(b->reserved)) {
- init_fsinfo(&i);
- fs_write((loff_t)s*lss,sizeof(i),&i);
- b->info_sector = CT_LE_W(s);
- fs_write((loff_t)offsetof(struct boot_sector,info_sector),
- sizeof(b->info_sector),&b->info_sector);
- if (fs->backupboot_start)
- fs_write(fs->backupboot_start+
- offsetof(struct boot_sector,info_sector),
- sizeof(b->info_sector),&b->info_sector);
- }
- else {
- printf( "No free reserved sector found -- "
- "no space for FSINFO sector!\n" );
- return;
- }
- }
- else return;
- }
- fs->fsinfo_start = CF_LE_W(b->info_sector)*lss;
- fs_read(fs->fsinfo_start,sizeof(i),&i);
- if (i.magic != CT_LE_L(0x41615252) ||
- i.signature != CT_LE_L(0x61417272) ||
- i.boot_sign != CT_LE_W(0xaa55)) {
- printf( "FSINFO sector has bad magic number(s):\n" );
- if (i.magic != CT_LE_L(0x41615252))
- printf( " Offset %llu: 0x%08x != expected 0x%08x\n",
- (unsigned long long)offsetof(struct info_sector,magic),
- CF_LE_L(i.magic),0x41615252);
- if (i.signature != CT_LE_L(0x61417272))
- printf( " Offset %llu: 0x%08x != expected 0x%08x\n",
- (unsigned long long)offsetof(struct info_sector,signature),
- CF_LE_L(i.signature),0x61417272);
- if (i.boot_sign != CT_LE_W(0xaa55))
- printf( " Offset %llu: 0x%04x != expected 0x%04x\n",
- (unsigned long long)offsetof(struct info_sector,boot_sign),
- CF_LE_W(i.boot_sign),0xaa55);
- if (interactive)
- printf( "1) Correct\n2) Don't correct (FSINFO invalid then)\n" );
- else printf( " Auto-correcting it.\n" );
- if (!interactive || get_key("12","?") == '1') {
- init_fsinfo(&i);
- fs_write(fs->fsinfo_start,sizeof(i),&i);
- }
- else fs->fsinfo_start = 0;
- }
- if (fs->fsinfo_start)
- fs->free_clusters = CF_LE_L(i.free_clusters);
- }
- void read_boot(DOS_FS *fs)
- {
- struct boot_sector b;
- unsigned total_sectors;
- unsigned short logical_sector_size, sectors;
- unsigned fat_length;
- loff_t data_size;
- fs_read(0,sizeof(b),&b);
- logical_sector_size = GET_UNALIGNED_W(b.sector_size);
- if (!logical_sector_size) die("Logical sector size is zero.");
- /* This was moved up because it's the first thing that will fail */
- /* if the platform needs special handling of unaligned multibyte accesses */
- /* but such handling isn't being provided. See GET_UNALIGNED_W() above. */
- if (logical_sector_size & (SECTOR_SIZE-1))
- die("Logical sector size (%d bytes) is not a multiple of the physical "
- "sector size.",logical_sector_size);
- fs->cluster_size = b.cluster_size*logical_sector_size;
- if (!fs->cluster_size) die("Cluster size is zero.");
- if (b.fats != 2 && b.fats != 1)
- die("Currently, only 1 or 2 FATs are supported, not %d.\n",b.fats);
- fs->nfats = b.fats;
- sectors = GET_UNALIGNED_W(b.sectors);
- total_sectors = sectors ? sectors : CF_LE_L(b.total_sect);
- if (verbose) printf("Checking we can access the last sector of the filesystem\n");
- /* Can't access last odd sector anyway, so round down */
- fs_test((loff_t)((total_sectors & ~1)-1)*(loff_t)logical_sector_size,
- logical_sector_size);
- fat_length = CF_LE_W(b.fat_length) ?
- CF_LE_W(b.fat_length) : CF_LE_L(b.fat32_length);
- fs->fat_start = (loff_t)CF_LE_W(b.reserved)*logical_sector_size;
- fs->root_start = ((loff_t)CF_LE_W(b.reserved)+b.fats*fat_length)*
- logical_sector_size;
- fs->root_entries = GET_UNALIGNED_W(b.dir_entries);
- fs->data_start = fs->root_start+ROUND_TO_MULTIPLE(fs->root_entries <<
- MSDOS_DIR_BITS,logical_sector_size);
- data_size = (loff_t)total_sectors*logical_sector_size-fs->data_start;
- fs->clusters = data_size/fs->cluster_size;
- fs->root_cluster = 0; /* indicates standard, pre-FAT32 root dir */
- fs->fsinfo_start = 0; /* no FSINFO structure */
- fs->free_clusters = -1; /* unknown */
- if (!b.fat_length && b.fat32_length) {
- fs->fat_bits = 32;
- fs->root_cluster = CF_LE_L(b.root_cluster);
- if (!fs->root_cluster && fs->root_entries)
- /* M$ hasn't specified this, but it looks reasonable: If
- * root_cluster is 0 but there is a separate root dir
- * (root_entries != 0), we handle the root dir the old way. Give a
- * warning, but convertig to a root dir in a cluster chain seems
- * to complex for now... */
- printf( "Warning: FAT32 root dir not in cluster chain! "
- "Compatibility mode...\n" );
- else if (!fs->root_cluster && !fs->root_entries)
- die("No root directory!");
- else if (fs->root_cluster && fs->root_entries)
- printf( "Warning: FAT32 root dir is in a cluster chain, but "
- "a separate root dir\n"
- " area is defined. Cannot fix this easily.\n" );
- if (fs->clusters < FAT16_THRESHOLD)
- printf("Warning: Filesystem is FAT32 according to fat_length "
- "and fat32_length fields,\n"
- " but has only %lu clusters, less than the required "
- "minimum of %d.\n"
- " This may lead to problems on some systems.\n",
- fs->clusters, FAT16_THRESHOLD);
- fs->backupboot_start = CF_LE_W(b.backup_boot)*logical_sector_size;
- check_backup_boot(fs,&b,logical_sector_size);
- read_fsinfo(fs,&b,logical_sector_size);
- }
- else if (!atari_format) {
- /* On real MS-DOS, a 16 bit FAT is used whenever there would be too
- * much clusers otherwise. */
- fs->fat_bits = (fs->clusters >= FAT12_THRESHOLD) ? 16 : 12;
- if (fs->clusters >= FAT16_THRESHOLD)
- die("Too many clusters (%lu) for FAT16 filesystem.",
- fs->clusters);
- }
- else {
- /* On Atari, things are more difficult: GEMDOS always uses 12bit FATs
- * on floppies, and always 16 bit on harddisks. */
- fs->fat_bits = 16; /* assume 16 bit FAT for now */
- /* If more clusters than fat entries in 16-bit fat, we assume
- * it's a real MSDOS FS with 12-bit fat. */
- if (fs->clusters+2 > fat_length*logical_sector_size*8/16 ||
- /* if it's a floppy disk --> 12bit fat */
- device_no == 2 ||
- /* if it's a ramdisk or loopback device and has one of the usual
- * floppy sizes -> 12bit FAT */
- ((device_no == 1 || device_no == 7) &&
- (total_sectors == 720 || total_sectors == 1440 ||
- total_sectors == 2880)))
- fs->fat_bits = 12;
- }
- /* On FAT32, the high 4 bits of a FAT entry are reserved */
- fs->eff_fat_bits = (fs->fat_bits == 32) ? 28 : fs->fat_bits;
- fs->fat_size = fat_length*logical_sector_size;
- fs->label = calloc(12, sizeof (__u8));
- if (fs->fat_bits == 12 || fs->fat_bits == 16) {
- struct boot_sector_16 *b16 = (struct boot_sector_16 *)&b;
- if (b16->extended_sig == 0x29)
- memmove(fs->label, b16->label, 11);
- else
- fs->label = NULL;
- } else if (fs->fat_bits == 32) {
- if (b.extended_sig == 0x29)
- memmove(fs->label, &b.label, 11);
- else
- fs->label = NULL;
- }
- if (fs->clusters > ((unsigned long long)fs->fat_size*8/fs->fat_bits)-2)
- die("File system has %d clusters but only space for %d FAT entries.",
- fs->clusters,((unsigned long long)fs->fat_size*8/fs->fat_bits)-2);
- if (!fs->root_entries && !fs->root_cluster)
- die("Root directory has zero size.");
- if (fs->root_entries & (MSDOS_DPS-1))
- die("Root directory (%d entries) doesn't span an integral number of "
- "sectors.",fs->root_entries);
- if (logical_sector_size & (SECTOR_SIZE-1))
- die("Logical sector size (%d bytes) is not a multiple of the physical "
- "sector size.",logical_sector_size);
- #if 0 /* linux kernel doesn't check that either */
- /* ++roman: On Atari, these two fields are often left uninitialized */
- if (!atari_format && (!b.secs_track || !b.heads))
- die("Invalid disk format in boot sector.");
- #endif
- if (verbose) dump_boot(fs,&b,logical_sector_size);
- }
- static void write_boot_label(DOS_FS *fs, char *label)
- {
- struct boot_sector b;
- struct boot_sector_16 *b16 = (struct boot_sector_16 *)&b;
- fs_read(0, sizeof(b), &b);
- if (fs->fat_bits == 12 || fs->fat_bits == 16) {
- if (b16->extended_sig != 0x29) {
- b16->extended_sig = 0x29;
- b16->serial = 0;
- memmove(b16->fs_type, fs->fat_bits == 12 ?"FAT12 ":"FAT16 ", 8);
- }
- memmove(b16->label, label, 11);
- } else if (fs->fat_bits == 32) {
- if (b.extended_sig != 0x29) {
- b.extended_sig = 0x29;
- b.serial = 0;
- memmove(b.fs_type, "FAT32 ", 8);
- }
- memmove(b.label, label, 11);
- }
- fs_write(0, sizeof(b), &b);
- if (fs->fat_bits == 32 && fs->backupboot_start)
- fs_write(fs->backupboot_start, sizeof(b), &b);
- }
- static loff_t find_volume_de(DOS_FS *fs, DIR_ENT *de)
- {
- unsigned long cluster;
- loff_t offset;
- int i;
- if (fs->root_cluster) {
- for (cluster = fs->root_cluster;
- cluster != 0 && cluster != -1;
- cluster = next_cluster(fs, cluster)) {
- offset = cluster_start(fs, cluster);
- for (i = 0; i * sizeof(DIR_ENT) < fs->cluster_size; i++) {
- fs_read(offset, sizeof(DIR_ENT), de);
- if (de->attr & ATTR_VOLUME)
- return offset;
- offset += sizeof(DIR_ENT);
- }
- }
- } else {
- for (i = 0; i < fs->root_entries; i++) {
- offset = fs->root_start + i * sizeof(DIR_ENT);
- fs_read(offset, sizeof(DIR_ENT), de);
- if (de->attr & ATTR_VOLUME)
- return offset;
- }
- }
- return 0;
- }
- static void write_volume_label(DOS_FS *fs, char *label)
- {
- time_t now = time(NULL);
- struct tm *mtime = localtime(&now);
- loff_t offset;
- DIR_ENT de;
- offset = find_volume_de(fs, &de);
- if (offset == 0)
- return;
- memcpy(de.name, label, 11);
- de.time = CT_LE_W((unsigned short)((mtime->tm_sec >> 1) +
- (mtime->tm_min << 5) +
- (mtime->tm_hour << 11)));
- de.date = CT_LE_W((unsigned short)(mtime->tm_mday +
- ((mtime->tm_mon+1) << 5) +
- ((mtime->tm_year-80) << 9)));
- fs_write(offset, sizeof(DIR_ENT), &de);
- }
- void write_label(DOS_FS *fs, char *label)
- {
- int l = strlen(label);
- while (l < 11)
- label[l++] = ' ';
- write_boot_label(fs, label);
- write_volume_label(fs, label);
- }
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