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      1 /*
      2  * Copyright (C) 1995, 1997 Wolfgang Solfrank
      3  * Copyright (c) 1995 Martin Husemann
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by Martin Husemann
     16  *	and Wolfgang Solfrank.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 
     34 #include <sys/cdefs.h>
     35 #ifndef lint
     36 __RCSID("$NetBSD: boot.c,v 1.9 2003/07/24 19:25:46 ws Exp $");
     37 static const char rcsid[] =
     38   "$FreeBSD: src/sbin/fsck_msdosfs/boot.c,v 1.4.28.1 2009/04/15 03:14:26 kensmith Exp $";
     39 #endif /* not lint */
     40 
     41 #include <stdlib.h>
     42 #include <string.h>
     43 #include <ctype.h>
     44 #include <stdio.h>
     45 #include <unistd.h>
     46 
     47 #include "ext.h"
     48 #include "fsutil.h"
     49 
     50 int
     51 readboot(dosfs, boot)
     52 	int dosfs;
     53 	struct bootblock *boot;
     54 {
     55 	u_char block[DOSBOOTBLOCKSIZE];
     56 	u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
     57 	u_char backup[DOSBOOTBLOCKSIZE];
     58 	int ret = FSOK;
     59 
     60 	if (read(dosfs, block, sizeof block) < sizeof block) {
     61 		perror("could not read boot block");
     62                 exit(2);
     63 	}
     64 
     65 	if (block[510] != 0x55 || block[511] != 0xaa) {
     66 		pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
     67                 exit(2);
     68 	}
     69 
     70 	memset(boot, 0, sizeof *boot);
     71 	boot->ValidFat = -1;
     72 
     73 	/* decode bios parameter block */
     74 	boot->BytesPerSec = block[11] + (block[12] << 8);
     75 	boot->SecPerClust = block[13];
     76 	boot->ResSectors = block[14] + (block[15] << 8);
     77 	boot->FATs = block[16];
     78 	boot->RootDirEnts = block[17] + (block[18] << 8);
     79 	boot->Sectors = block[19] + (block[20] << 8);
     80 	boot->Media = block[21];
     81 	boot->FATsmall = block[22] + (block[23] << 8);
     82 	boot->SecPerTrack = block[24] + (block[25] << 8);
     83 	boot->Heads = block[26] + (block[27] << 8);
     84 	boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
     85 	boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
     86 
     87 	boot->FATsecs = boot->FATsmall;
     88 
     89 	if (!boot->RootDirEnts)
     90 		boot->flags |= FAT32;
     91 	if (boot->flags & FAT32) {
     92 		boot->FATsecs = block[36] + (block[37] << 8)
     93 				+ (block[38] << 16) + (block[39] << 24);
     94 		if (block[40] & 0x80)
     95 			boot->ValidFat = block[40] & 0x0f;
     96 
     97 		/* check version number: */
     98 		if (block[42] || block[43]) {
     99 			/* Correct?				XXX */
    100 			pfatal("Unknown file system version: %x.%x",
    101 			       block[43], block[42]);
    102                         exit(2);
    103 		}
    104 		boot->RootCl = block[44] + (block[45] << 8)
    105 			       + (block[46] << 16) + (block[47] << 24);
    106 		boot->FSInfo = block[48] + (block[49] << 8);
    107 		boot->Backup = block[50] + (block[51] << 8);
    108 
    109 		if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
    110 		    != boot->FSInfo * boot->BytesPerSec
    111 		    || read(dosfs, fsinfo, sizeof fsinfo)
    112 		    != sizeof fsinfo) {
    113 			perror("could not read fsinfo block");
    114 			return FSFATAL;
    115 		}
    116 		if (memcmp(fsinfo, "RRaA", 4)
    117 		    || memcmp(fsinfo + 0x1e4, "rrAa", 4)
    118 		    || fsinfo[0x1fc]
    119 		    || fsinfo[0x1fd]
    120 		    || fsinfo[0x1fe] != 0x55
    121 		    || fsinfo[0x1ff] != 0xaa
    122 		    || fsinfo[0x3fc]
    123 		    || fsinfo[0x3fd]
    124 		    || fsinfo[0x3fe] != 0x55
    125 		    || fsinfo[0x3ff] != 0xaa) {
    126 			pwarn("Invalid signature in fsinfo block\n");
    127 			if (ask(1, "fix")) {
    128 				memcpy(fsinfo, "RRaA", 4);
    129 				memcpy(fsinfo + 0x1e4, "rrAa", 4);
    130 				fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
    131 				fsinfo[0x1fe] = 0x55;
    132 				fsinfo[0x1ff] = 0xaa;
    133 				fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
    134 				fsinfo[0x3fe] = 0x55;
    135 				fsinfo[0x3ff] = 0xaa;
    136 				if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
    137 				    != boot->FSInfo * boot->BytesPerSec
    138 				    || write(dosfs, fsinfo, sizeof fsinfo)
    139 				    != sizeof fsinfo) {
    140 					perror("Unable to write FSInfo");
    141 					return FSFATAL;
    142 				}
    143 				ret = FSBOOTMOD;
    144 			} else
    145 				boot->FSInfo = 0;
    146 		}
    147 		if (boot->FSInfo) {
    148 			boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
    149 				       + (fsinfo[0x1ea] << 16)
    150 				       + (fsinfo[0x1eb] << 24);
    151 			boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
    152 				       + (fsinfo[0x1ee] << 16)
    153 				       + (fsinfo[0x1ef] << 24);
    154 		}
    155 
    156 		if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
    157 		    != boot->Backup * boot->BytesPerSec
    158 		    || read(dosfs, backup, sizeof backup) != sizeof  backup) {
    159 			perror("could not read backup bootblock");
    160 			return FSFATAL;
    161 		}
    162 		backup[65] = block[65];				/* XXX */
    163 		if (memcmp(block + 11, backup + 11, 79)) {
    164                         char tmp[255];
    165                         int i;
    166 
    167 			/*
    168 			 * For now, lets not bail out if they don't match
    169 			 * It seems a lot of sdcards are formatted with
    170 			 * the backup either empty or containing garbage.
    171 			 */
    172 
    173 			pwarn("Primary/Backup bootblock miscompare\n");
    174 
    175                         strcpy(tmp, "");
    176                         pwarn("Primary:\n");
    177 			for (i = 0; i < 79; i++) {
    178 				char tmp2[16];
    179                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", block[11 + i]);
    180 				strcat(tmp, tmp2);
    181                         }
    182                         pwarn("%s\n", tmp);
    183 
    184 			strcpy(tmp, "");
    185                         pwarn("Backup:\n");
    186 			for (i = 0; i < 79; i++) {
    187 				char tmp2[16];
    188                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", backup[11 + i]);
    189 				strcat(tmp, tmp2);
    190                         }
    191                         pwarn("%s\n", tmp);
    192 		}
    193 		/* Check backup FSInfo?					XXX */
    194 	}
    195 
    196 	boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
    197 	    / boot->BytesPerSec
    198 	    + boot->ResSectors
    199 	    + boot->FATs * boot->FATsecs
    200 	    - CLUST_FIRST * boot->SecPerClust;
    201 
    202 	if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
    203 		pfatal("Invalid sector size: %u", boot->BytesPerSec);
    204 		return FSFATAL;
    205 	}
    206 	if (boot->SecPerClust == 0) {
    207 		pfatal("Invalid cluster size: %u", boot->SecPerClust);
    208 		return FSFATAL;
    209 	}
    210 	if (boot->Sectors) {
    211 		boot->HugeSectors = 0;
    212 		boot->NumSectors = boot->Sectors;
    213 	} else
    214 		boot->NumSectors = boot->HugeSectors;
    215 	boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
    216 
    217 	if (boot->flags&FAT32)
    218 		boot->ClustMask = CLUST32_MASK;
    219 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
    220 		boot->ClustMask = CLUST12_MASK;
    221 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
    222 		boot->ClustMask = CLUST16_MASK;
    223 	else {
    224 		pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
    225 		       boot->NumClusters);
    226 		return FSFATAL;
    227 	}
    228 
    229 	switch (boot->ClustMask) {
    230 	case CLUST32_MASK:
    231 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
    232 		break;
    233 	case CLUST16_MASK:
    234 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
    235 		break;
    236 	default:
    237 		boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
    238 		break;
    239 	}
    240 
    241 	if (boot->NumFatEntries < boot->NumClusters) {
    242 		pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
    243 		       boot->NumClusters, boot->FATsecs);
    244 		return FSFATAL;
    245 	}
    246 	boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
    247 
    248 	boot->NumFiles = 1;
    249 	boot->NumFree = 0;
    250 
    251 	return ret;
    252 }
    253 
    254 int
    255 writefsinfo(dosfs, boot)
    256 	int dosfs;
    257 	struct bootblock *boot;
    258 {
    259 	u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
    260 
    261 	if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
    262 	    != boot->FSInfo * boot->BytesPerSec
    263 	    || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
    264 		perror("could not read fsinfo block");
    265 		return FSFATAL;
    266 	}
    267 	fsinfo[0x1e8] = (u_char)boot->FSFree;
    268 	fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
    269 	fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
    270 	fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
    271 	fsinfo[0x1ec] = (u_char)boot->FSNext;
    272 	fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
    273 	fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
    274 	fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
    275 	if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
    276 	    != boot->FSInfo * boot->BytesPerSec
    277 	    || write(dosfs, fsinfo, sizeof fsinfo)
    278 	    != sizeof fsinfo) {
    279 		perror("Unable to write FSInfo");
    280 		return FSFATAL;
    281 	}
    282 	/*
    283 	 * Technically, we should return FSBOOTMOD here.
    284 	 *
    285 	 * However, since Win95 OSR2 (the first M$ OS that has
    286 	 * support for FAT32) doesn't maintain the FSINFO block
    287 	 * correctly, it has to be fixed pretty often.
    288 	 *
    289 	 * Therefor, we handle the FSINFO block only informally,
    290 	 * fixing it if necessary, but otherwise ignoring the
    291 	 * fact that it was incorrect.
    292 	 */
    293 	return 0;
    294 }
    295