/* 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>
Copyright (C) 2008-2014 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/>.
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 <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include "common.h"
#include "fsck.fat.h"
#include "fat.h"
#include "io.h"
#include "boot.h"
#include "check.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 {
uint8_t media;
const 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"},};
/* Unaligned fields must first be accessed byte-wise */
#define GET_UNALIGNED_W(f) \
( (uint16_t)f[0] | ((uint16_t)f[1]<<8) )
static const 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, (const char *)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", le16toh(b->reserved),
le16toh(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",
(unsigned long)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", (unsigned long)fs->clusters,
(unsigned long long)fs->clusters * fs->cluster_size);
printf("%u sectors/track, %u heads\n", le16toh(b->secs_track),
le16toh(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) : le32toh(b->hidden));
sectors = GET_UNALIGNED_W(b->sectors);
printf("%10u sectors total\n", sectors ? sectors : le32toh(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 (le16toh(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 (le16toh(b->reserved) >= 7 && le16toh(b->info_sector) != 6)
bbs = 6;
else {
bbs = le16toh(b->reserved) - 1;
if (bbs == le16toh(b->info_sector))
--bbs; /* this is never 0, as we checked reserved >= 3! */
}
fs->backupboot_start = bbs * lss;
b->backup_boot = htole16(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 */
uint8_t *p, *q;
int i, pos, first = 1;
char buf[20];
printf("There are differences between boot sector and its backup.\n");
printf("This is mostly harmless. Differences: (offset:original/backup)\n ");
pos = 2;
for (p = (uint8_t *) b, q = (uint8_t *) & b2, i = 0; i < sizeof(b2);
++p, ++q, ++i) {
if (*p != *q) {
sprintf(buf, "%s%u:%02x/%02x", first ? "" : ", ",
(unsigned)(p - (uint8_t *) 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 = htole32(0x41615252);
i->signature = htole32(0x61417272);
i->free_clusters = htole32(-1);
i->next_cluster = htole32(2);
i->boot_sign = htole16(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) */
uint32_t s;
for (s = 1; s < le16toh(b->reserved); ++s)
if (s != le16toh(b->backup_boot))
break;
if (s > 0 && s < le16toh(b->reserved)) {
init_fsinfo(&i);
fs_write((loff_t) s * lss, sizeof(i), &i);
b->info_sector = htole16(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 = le16toh(b->info_sector) * lss;
fs_read(fs->fsinfo_start, sizeof(i), &i);
if (i.magic != htole32(0x41615252) ||
i.signature != htole32(0x61417272) || i.boot_sign != htole16(0xaa55)) {
printf("FSINFO sector has bad magic number(s):\n");
if (i.magic != htole32(0x41615252))
printf(" Offset %llu: 0x%08x != expected 0x%08x\n",
(unsigned long long)offsetof(struct info_sector, magic),
le32toh(i.magic), 0x41615252);
if (i.signature != htole32(0x61417272))
printf(" Offset %llu: 0x%08x != expected 0x%08x\n",
(unsigned long long)offsetof(struct info_sector, signature),
le32toh(i.signature), 0x61417272);
if (i.boot_sign != htole16(0xaa55))
printf(" Offset %llu: 0x%04x != expected 0x%04x\n",
(unsigned long long)offsetof(struct info_sector, boot_sign),
le16toh(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 = le32toh(i.free_clusters);
}
static char print_fat_dirty_state(void)
{
printf("Dirty bit is set. Fs was not properly unmounted and"
" some data may be corrupt.\n");
if (interactive) {
printf("1) Remove dirty bit\n" "2) No action\n");
return get_key("12", "?");
} else
printf(" Automatically removing dirty bit.\n");
return '1';
}
static void check_fat_state_bit(DOS_FS * fs, void *b)
{
if (fs->fat_bits == 32) {
struct boot_sector *b32 = b;
if (b32->reserved3 & FAT_STATE_DIRTY) {
printf("0x41: ");
if (print_fat_dirty_state() == '1') {
b32->reserved3 &= ~FAT_STATE_DIRTY;
fs_write(0, sizeof(*b32), b32);
}
}
} else {
struct boot_sector_16 *b16 = b;
if (b16->reserved2 & FAT_STATE_DIRTY) {
printf("0x25: ");
if (print_fat_dirty_state() == '1') {
b16->reserved2 &= ~FAT_STATE_DIRTY;
fs_write(0, sizeof(*b16), b16);
}
}
}
}
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 : le32toh(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 = le16toh(b.fat_length) ?
le16toh(b.fat_length) : le32toh(b.fat32_length);
fs->fat_start = (loff_t) le16toh(b.reserved) * logical_sector_size;
fs->root_start = ((loff_t) le16toh(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 = le32toh(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",
(unsigned long)fs->clusters, FAT16_THRESHOLD);
check_fat_state_bit(fs, &b);
fs->backupboot_start = le16toh(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);
check_fat_state_bit(fs, &b);
} 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(uint8_t));
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 >
((uint64_t)fs->fat_size * 8 / fs->fat_bits) - 2)
die("Filesystem 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)
{
if (fs->fat_bits == 12 || fs->fat_bits == 16) {
struct boot_sector_16 b16;
fs_read(0, sizeof(b16), &b16);
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);
fs_write(0, sizeof(b16), &b16);
} else if (fs->fat_bits == 32) {
struct boot_sector b;
fs_read(0, sizeof(b), &b);
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->backupboot_start)
fs_write(fs->backupboot_start, sizeof(b), &b);
}
}
loff_t find_volume_de(DOS_FS * fs, DIR_ENT * de)
{
uint32_t 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 != VFAT_LN_ATTR && 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 != VFAT_LN_ATTR && 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;
int created;
DIR_ENT de;
created = 0;
offset = find_volume_de(fs, &de);
if (offset == 0) {
created = 1;
offset = alloc_rootdir_entry(fs, &de, label);
}
memcpy(de.name, label, 11);
de.time = htole16((unsigned short)((mtime->tm_sec >> 1) +
(mtime->tm_min << 5) +
(mtime->tm_hour << 11)));
de.date = htole16((unsigned short)(mtime->tm_mday +
((mtime->tm_mon + 1) << 5) +
((mtime->tm_year - 80) << 9)));
if (created) {
de.attr = ATTR_VOLUME;
de.ctime_ms = 0;
de.ctime = de.time;
de.cdate = de.date;
de.adate = de.date;
de.starthi = 0;
de.start = 0;
de.size = 0;
}
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);
}
