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371 lines
13 KiB
C
371 lines
13 KiB
C
/* boot.c - Read and analyze ia PC/MS-DOS boot sector */
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/* Written 1993 by Werner Almesberger */
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/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
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* by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
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#include <stdio.h>
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#include <string.h>
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#include <sys/types.h>
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#include "common.h"
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#include "dosfsck.h"
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#include "io.h"
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#include "boot.h"
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#define ROUND_TO_MULTIPLE(n,m) ((n) && (m) ? (n)+(m)-1-((n)-1)%(m) : 0)
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/* don't divide by zero */
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static struct {
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__u8 media;
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char *descr;
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} mediabytes[] = {
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{ 0xf0, "5.25\" or 3.5\" HD floppy" },
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{ 0xf8, "hard disk" },
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{ 0xf9, "3,5\" 720k floppy 2s/80tr/9sec or "
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"5.25\" 1.2M floppy 2s/80tr/15sec" },
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{ 0xfa, "5.25\" 320k floppy 1s/80tr/8sec" },
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{ 0xfb, "3.5\" 640k floppy 2s/80tr/8sec" },
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{ 0xfc, "5.25\" 180k floppy 1s/40tr/9sec" },
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{ 0xfd, "5.25\" 360k floppy 2s/40tr/9sec" },
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{ 0xfe, "5.25\" 160k floppy 1s/40tr/8sec" },
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{ 0xff, "5.25\" 320k floppy 2s/40tr/8sec" },
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};
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#if defined __alpha || defined __ia64__ || defined __s390x__ || defined __x86_64__ || defined __ppc64__
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/* Unaligned fields must first be copied byte-wise */
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#define GET_UNALIGNED_W(f) \
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({ \
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unsigned short __v; \
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memcpy( &__v, &f, sizeof(__v) ); \
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CF_LE_W( *(unsigned short *)&f ); \
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})
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#else
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#define GET_UNALIGNED_W(f) CF_LE_W( *(unsigned short *)&f )
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#endif
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static char *get_media_descr( unsigned char media )
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{
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int i;
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for( i = 0; i < sizeof(mediabytes)/sizeof(*mediabytes); ++i ) {
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if (mediabytes[i].media == media)
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return( mediabytes[i].descr );
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}
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return( "undefined" );
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}
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static void dump_boot(DOS_FS *fs,struct boot_sector *b,unsigned lss)
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{
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unsigned short sectors;
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printf("Boot sector contents:\n");
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if (!atari_format) {
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char id[9];
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strncpy(id,b->system_id,8);
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id[8] = 0;
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printf("System ID \"%s\"\n",id);
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}
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else {
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/* On Atari, a 24 bit serial number is stored at offset 8 of the boot
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* sector */
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printf("Serial number 0x%x\n",
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b->system_id[5] | (b->system_id[6]<<8) | (b->system_id[7]<<16));
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}
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printf("Media byte 0x%02x (%s)\n",b->media,get_media_descr(b->media));
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printf("%10d bytes per logical sector\n",GET_UNALIGNED_W(b->sector_size));
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printf("%10d bytes per cluster\n",fs->cluster_size);
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printf("%10d reserved sector%s\n",CF_LE_W(b->reserved),
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CF_LE_W(b->reserved) == 1 ? "" : "s");
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printf("First FAT starts at byte %llu (sector %llu)\n",
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(__u64)fs->fat_start,
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(__u64)fs->fat_start/lss);
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printf("%10d FATs, %d bit entries\n",b->fats,fs->fat_bits);
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printf("%10d bytes per FAT (= %u sectors)\n",fs->fat_size,
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fs->fat_size/lss);
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if (!fs->root_cluster) {
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printf("Root directory starts at byte %llu (sector %llu)\n",
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(__u64)fs->root_start,
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(__u64)fs->root_start/lss);
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printf("%10d root directory entries\n",fs->root_entries);
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}
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else {
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printf( "Root directory start at cluster %lu (arbitrary size)\n",
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fs->root_cluster);
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}
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printf("Data area starts at byte %llu (sector %llu)\n",
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(__u64)fs->data_start,
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(__u64)fs->data_start/lss);
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printf("%10lu data clusters (%llu bytes)\n",fs->clusters,
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(__u64)fs->clusters*fs->cluster_size);
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printf("%u sectors/track, %u heads\n",CF_LE_W(b->secs_track),
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CF_LE_W(b->heads));
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printf("%10u hidden sectors\n",
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atari_format ?
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/* On Atari, the hidden field is only 16 bit wide and unused */
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(((unsigned char *)&b->hidden)[0] |
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((unsigned char *)&b->hidden)[1] << 8) :
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CF_LE_L(b->hidden));
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sectors = GET_UNALIGNED_W( b->sectors );
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printf("%10u sectors total\n", sectors ? sectors : CF_LE_L(b->total_sect));
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}
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static void check_backup_boot(DOS_FS *fs, struct boot_sector *b, int lss)
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{
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struct boot_sector b2;
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if (!fs->backupboot_start) {
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printf( "There is no backup boot sector.\n" );
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if (CF_LE_W(b->reserved) < 3) {
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printf( "And there is no space for creating one!\n" );
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return;
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}
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if (interactive)
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printf( "1) Create one\n2) Do without a backup\n" );
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else printf( " Auto-creating backup boot block.\n" );
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if (!interactive || get_key("12","?") == '1') {
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int bbs;
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/* The usual place for the backup boot sector is sector 6. Choose
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* that or the last reserved sector. */
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if (CF_LE_W(b->reserved) >= 7 && CF_LE_W(b->info_sector) != 6)
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bbs = 6;
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else {
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bbs = CF_LE_W(b->reserved) - 1;
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if (bbs == CF_LE_W(b->info_sector))
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--bbs; /* this is never 0, as we checked reserved >= 3! */
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}
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fs->backupboot_start = bbs*lss;
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b->backup_boot = CT_LE_W(bbs);
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fs_write(fs->backupboot_start,sizeof(*b),b);
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fs_write((off_t)offsetof(struct boot_sector,backup_boot),
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sizeof(b->backup_boot),&b->backup_boot);
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printf( "Created backup of boot sector in sector %d\n", bbs );
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return;
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}
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else return;
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}
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fs_read(fs->backupboot_start,sizeof(b2),&b2);
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if (memcmp(b,&b2,sizeof(b2)) != 0) {
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/* there are any differences */
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__u8 *p, *q;
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int i, pos, first = 1;
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char buf[20];
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printf( "There are differences between boot sector and its backup.\n" );
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printf( "Differences: (offset:original/backup)\n " );
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pos = 2;
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for( p = (__u8 *)b, q = (__u8 *)&b2, i = 0; i < sizeof(b2);
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++p, ++q, ++i ) {
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if (*p != *q) {
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sprintf( buf, "%s%u:%02x/%02x", first ? "" : ", ",
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(unsigned)(p-(__u8 *)b), *p, *q );
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if (pos + strlen(buf) > 78) printf( "\n " ), pos = 2;
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printf( "%s", buf );
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pos += strlen(buf);
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first = 0;
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}
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}
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printf( "\n" );
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if (interactive)
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printf( "1) Copy original to backup\n"
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"2) Copy backup to original\n"
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"3) No action\n" );
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else printf( " Not automatically fixing this.\n" );
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switch (interactive ? get_key("123","?") : '3') {
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case '1':
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fs_write(fs->backupboot_start,sizeof(*b),b);
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break;
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case '2':
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fs_write(0,sizeof(b2),&b2);
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break;
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default:
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break;
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}
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}
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}
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static void init_fsinfo(struct info_sector *i)
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{
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i->magic = CT_LE_L(0x41615252);
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i->signature = CT_LE_L(0x61417272);
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i->free_clusters = CT_LE_L(-1);
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i->next_cluster = CT_LE_L(2);
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i->boot_sign = CT_LE_W(0xaa55);
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}
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static void read_fsinfo(DOS_FS *fs, struct boot_sector *b,int lss)
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{
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struct info_sector i;
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if (!b->info_sector) {
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printf( "No FSINFO sector\n" );
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if (interactive)
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printf( "1) Create one\n2) Do without FSINFO\n" );
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else printf( " Not automatically creating it.\n" );
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if (interactive && get_key("12","?") == '1') {
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/* search for a free reserved sector (not boot sector and not
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* backup boot sector) */
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__u32 s;
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for( s = 1; s < CF_LE_W(b->reserved); ++s )
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if (s != CF_LE_W(b->backup_boot)) break;
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if (s > 0 && s < CF_LE_W(b->reserved)) {
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init_fsinfo(&i);
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fs_write((off_t)s*lss,sizeof(i),&i);
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b->info_sector = CT_LE_W(s);
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fs_write((off_t)offsetof(struct boot_sector,info_sector),
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sizeof(b->info_sector),&b->info_sector);
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if (fs->backupboot_start)
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fs_write(fs->backupboot_start+
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offsetof(struct boot_sector,info_sector),
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sizeof(b->info_sector),&b->info_sector);
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}
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else {
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printf( "No free reserved sector found -- "
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"no space for FSINFO sector!\n" );
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return;
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}
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}
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else return;
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}
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fs->fsinfo_start = CF_LE_W(b->info_sector)*lss;
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fs_read(fs->fsinfo_start,sizeof(i),&i);
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if (i.magic != CT_LE_L(0x41615252) ||
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i.signature != CT_LE_L(0x61417272) ||
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i.boot_sign != CT_LE_W(0xaa55)) {
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printf( "FSINFO sector has bad magic number(s):\n" );
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if (i.magic != CT_LE_L(0x41615252))
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printf( " Offset %llu: 0x%08x != expected 0x%08x\n",
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(__u64)offsetof(struct info_sector,magic),
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CF_LE_L(i.magic),0x41615252);
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if (i.signature != CT_LE_L(0x61417272))
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printf( " Offset %llu: 0x%08x != expected 0x%08x\n",
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(__u64)offsetof(struct info_sector,signature),
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CF_LE_L(i.signature),0x61417272);
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if (i.boot_sign != CT_LE_W(0xaa55))
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printf( " Offset %llu: 0x%04x != expected 0x%04x\n",
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(__u64)offsetof(struct info_sector,boot_sign),
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CF_LE_W(i.boot_sign),0xaa55);
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if (interactive)
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printf( "1) Correct\n2) Don't correct (FSINFO invalid then)\n" );
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else printf( " Auto-correcting it.\n" );
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if (!interactive || get_key("12","?") == '1') {
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init_fsinfo(&i);
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fs_write(fs->fsinfo_start,sizeof(i),&i);
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}
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else fs->fsinfo_start = 0;
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}
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if (fs->fsinfo_start)
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fs->free_clusters = CF_LE_L(i.free_clusters);
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}
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void read_boot(DOS_FS *fs)
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{
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struct boot_sector b;
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unsigned total_sectors;
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unsigned short logical_sector_size, sectors;
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unsigned fat_length;
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loff_t data_size;
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fs_read(0,sizeof(b),&b);
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logical_sector_size = GET_UNALIGNED_W(b.sector_size);
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if (!logical_sector_size) die("Logical sector size is zero.");
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fs->cluster_size = b.cluster_size*logical_sector_size;
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if (!fs->cluster_size) die("Cluster size is zero.");
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if (b.fats != 2 && b.fats != 1)
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die("Currently, only 1 or 2 FATs are supported, not %d.\n",b.fats);
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fs->nfats = b.fats;
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sectors = GET_UNALIGNED_W(b.sectors);
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total_sectors = sectors ? sectors : CF_LE_L(b.total_sect);
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if (verbose) printf("Checking we can access the last sector of the filesystem\n");
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/* Can't access last odd sector anyway, so round down */
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fs_test((loff_t)((total_sectors & ~1)-1)*(loff_t)logical_sector_size,
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logical_sector_size);
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fat_length = CF_LE_W(b.fat_length) ?
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CF_LE_W(b.fat_length) : CF_LE_L(b.fat32_length);
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fs->fat_start = (off_t)CF_LE_W(b.reserved)*logical_sector_size;
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fs->root_start = ((off_t)CF_LE_W(b.reserved)+b.fats*fat_length)*
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logical_sector_size;
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fs->root_entries = GET_UNALIGNED_W(b.dir_entries);
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fs->data_start = fs->root_start+ROUND_TO_MULTIPLE(fs->root_entries <<
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MSDOS_DIR_BITS,logical_sector_size);
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data_size = (loff_t)total_sectors*logical_sector_size-fs->data_start;
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fs->clusters = data_size/fs->cluster_size;
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fs->root_cluster = 0; /* indicates standard, pre-FAT32 root dir */
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fs->fsinfo_start = 0; /* no FSINFO structure */
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fs->free_clusters = -1; /* unknown */
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if (!b.fat_length && b.fat32_length) {
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fs->fat_bits = 32;
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fs->root_cluster = CF_LE_L(b.root_cluster);
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if (!fs->root_cluster && fs->root_entries)
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/* M$ hasn't specified this, but it looks reasonable: If
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* root_cluster is 0 but there is a separate root dir
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* (root_entries != 0), we handle the root dir the old way. Give a
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* warning, but convertig to a root dir in a cluster chain seems
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* to complex for now... */
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printf( "Warning: FAT32 root dir not in cluster chain! "
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"Compability mode...\n" );
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else if (!fs->root_cluster && !fs->root_entries)
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die("No root directory!");
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else if (fs->root_cluster && fs->root_entries)
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printf( "Warning: FAT32 root dir is in a cluster chain, but "
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"a separate root dir\n"
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" area is defined. Cannot fix this easily.\n" );
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fs->backupboot_start = CF_LE_W(b.backup_boot)*logical_sector_size;
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check_backup_boot(fs,&b,logical_sector_size);
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read_fsinfo(fs,&b,logical_sector_size);
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}
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else if (!atari_format) {
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/* On real MS-DOS, a 16 bit FAT is used whenever there would be too
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* much clusers otherwise. */
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fs->fat_bits = (fs->clusters > MSDOS_FAT12) ? 16 : 12;
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}
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else {
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/* On Atari, things are more difficult: GEMDOS always uses 12bit FATs
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* on floppies, and always 16 bit on harddisks. */
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fs->fat_bits = 16; /* assume 16 bit FAT for now */
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/* If more clusters than fat entries in 16-bit fat, we assume
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* it's a real MSDOS FS with 12-bit fat. */
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if (fs->clusters+2 > fat_length*logical_sector_size*8/16 ||
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/* if it's a floppy disk --> 12bit fat */
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device_no == 2 ||
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/* if it's a ramdisk or loopback device and has one of the usual
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* floppy sizes -> 12bit FAT */
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((device_no == 1 || device_no == 7) &&
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(total_sectors == 720 || total_sectors == 1440 ||
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total_sectors == 2880)))
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fs->fat_bits = 12;
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}
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/* On FAT32, the high 4 bits of a FAT entry are reserved */
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fs->eff_fat_bits = (fs->fat_bits == 32) ? 28 : fs->fat_bits;
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fs->fat_size = fat_length*logical_sector_size;
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if (fs->clusters > ((__u64)fs->fat_size*8/fs->fat_bits)-2)
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die("File system has %d clusters but only space for %d FAT entries.",
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fs->clusters,((__u64)fs->fat_size*8/fs->fat_bits)-2);
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if (!fs->root_entries && !fs->root_cluster)
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die("Root directory has zero size.");
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if (fs->root_entries & (MSDOS_DPS-1))
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die("Root directory (%d entries) doesn't span an integral number of "
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"sectors.",fs->root_entries);
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if (logical_sector_size & (SECTOR_SIZE-1))
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die("Logical sector size (%d bytes) is not a multiple of the physical "
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"sector size.",logical_sector_size);
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/* ++roman: On Atari, these two fields are often left uninitialized */
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if (!atari_format && (!b.secs_track || !b.heads))
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die("Invalid disk format in boot sector.");
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if (verbose) dump_boot(fs,&b,logical_sector_size);
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}
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/* Local Variables: */
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/* tab-width: 8 */
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/* End: */
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