9da1e4cf5f
print out the values of the bytes that do not match. Add comment explaining that there is no documented rationale for the check. fsck_msdos checks that several bytes are equal in the primary and backup bootblock. There is no documented rationale. The kernel does not enforce this when mounting a filesystem. I have a FAT32 filesystem on my disk (mounted as /share) which fails this check, but is accepted by both Windows XP and NetBSD. My volume differs in bytes 71-81. The primary contains "SHARE " and the backup NUL bytes. Further, fsck_msdos does not have code to repair the mismatch. As a result such filesystems can be used not checked.
279 lines
9.0 KiB
C
279 lines
9.0 KiB
C
/* $NetBSD: boot.c,v 1.13 2007/03/19 18:30:40 gdt Exp $ */
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/*
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* Copyright (C) 1995, 1997 Wolfgang Solfrank
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* Copyright (c) 1995 Martin Husemann
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Martin Husemann
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* and Wolfgang Solfrank.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#ifndef lint
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__RCSID("$NetBSD: boot.c,v 1.13 2007/03/19 18:30:40 gdt Exp $");
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#endif /* not lint */
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "ext.h"
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#include "fsutil.h"
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int
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readboot(int dosfs, struct bootblock *boot)
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{
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u_char block[DOSBOOTBLOCKSIZE];
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u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
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u_char backup[DOSBOOTBLOCKSIZE];
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int ret = FSOK;
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int i;
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if (read(dosfs, block, sizeof block) < sizeof block) {
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perr("could not read boot block");
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return FSFATAL;
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}
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if (block[510] != 0x55 || block[511] != 0xaa) {
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pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
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return FSFATAL;
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}
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memset(boot, 0, sizeof *boot);
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boot->ValidFat = -1;
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/* decode bios parameter block */
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boot->BytesPerSec = block[11] + (block[12] << 8);
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boot->SecPerClust = block[13];
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boot->ResSectors = block[14] + (block[15] << 8);
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boot->FATs = block[16];
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boot->RootDirEnts = block[17] + (block[18] << 8);
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boot->Sectors = block[19] + (block[20] << 8);
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boot->Media = block[21];
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boot->FATsmall = block[22] + (block[23] << 8);
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boot->SecPerTrack = block[24] + (block[25] << 8);
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boot->Heads = block[26] + (block[27] << 8);
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boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
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boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
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boot->FATsecs = boot->FATsmall;
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if (!boot->RootDirEnts)
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boot->flags |= FAT32;
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if (boot->flags & FAT32) {
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boot->FATsecs = block[36] + (block[37] << 8)
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+ (block[38] << 16) + (block[39] << 24);
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if (block[40] & 0x80)
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boot->ValidFat = block[40] & 0x0f;
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/* check version number: */
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if (block[42] || block[43]) {
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/* Correct? XXX */
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pfatal("Unknown filesystem version: %x.%x",
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block[43], block[42]);
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return FSFATAL;
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}
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boot->RootCl = block[44] + (block[45] << 8)
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+ (block[46] << 16) + (block[47] << 24);
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boot->FSInfo = block[48] + (block[49] << 8);
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boot->Backup = block[50] + (block[51] << 8);
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if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
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!= boot->FSInfo * boot->BytesPerSec
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|| read(dosfs, fsinfo, sizeof fsinfo)
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!= sizeof fsinfo) {
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perr("could not read fsinfo block");
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return FSFATAL;
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}
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if (memcmp(fsinfo, "RRaA", 4)
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|| memcmp(fsinfo + 0x1e4, "rrAa", 4)
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|| fsinfo[0x1fc]
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|| fsinfo[0x1fd]
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|| fsinfo[0x1fe] != 0x55
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|| fsinfo[0x1ff] != 0xaa
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|| fsinfo[0x3fc]
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|| fsinfo[0x3fd]
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|| fsinfo[0x3fe] != 0x55
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|| fsinfo[0x3ff] != 0xaa) {
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pwarn("Invalid signature in fsinfo block");
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if (ask(0, "fix")) {
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memcpy(fsinfo, "RRaA", 4);
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memcpy(fsinfo + 0x1e4, "rrAa", 4);
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fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
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fsinfo[0x1fe] = 0x55;
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fsinfo[0x1ff] = 0xaa;
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fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
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fsinfo[0x3fe] = 0x55;
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fsinfo[0x3ff] = 0xaa;
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if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
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!= boot->FSInfo * boot->BytesPerSec
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|| write(dosfs, fsinfo, sizeof fsinfo)
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!= sizeof fsinfo) {
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perr("Unable to write FSInfo");
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return FSFATAL;
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}
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ret = FSBOOTMOD;
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} else
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boot->FSInfo = 0;
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}
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if (boot->FSInfo) {
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boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
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+ (fsinfo[0x1ea] << 16)
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+ (fsinfo[0x1eb] << 24);
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boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
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+ (fsinfo[0x1ee] << 16)
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+ (fsinfo[0x1ef] << 24);
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}
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if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
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!= boot->Backup * boot->BytesPerSec
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|| read(dosfs, backup, sizeof backup) != sizeof backup) {
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perr("could not read backup bootblock");
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return FSFATAL;
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}
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backup[65] = block[65]; /* XXX */
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if (memcmp(block + 11, backup + 11, 79)) {
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/*
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* XXX We require a reference that explains
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* that these bytes need to match, or should
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* drop the check. gdt@ has observed
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* filesystems that work fine under Windows XP
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* and NetBSD that do not match, so the
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* requirement is suspect. For now, just
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* print out useful information and continue.
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*/
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pfatal("backup (block %d) mismatch with primary bootblock:\n",
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boot->Backup);
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for (i = 11; i < 11 + 90; i++) {
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if (block[i] != backup[i])
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pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
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i, block[i], backup[i]);
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}
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}
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/* Check backup FSInfo? XXX */
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}
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boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
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/ boot->BytesPerSec
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+ boot->ResSectors
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+ boot->FATs * boot->FATsecs
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- CLUST_FIRST * boot->SecPerClust;
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if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
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pfatal("Invalid sector size: %u", boot->BytesPerSec);
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return FSFATAL;
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}
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if (boot->SecPerClust == 0) {
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pfatal("Invalid cluster size: %u", boot->SecPerClust);
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return FSFATAL;
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}
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if (boot->Sectors) {
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boot->HugeSectors = 0;
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boot->NumSectors = boot->Sectors;
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} else
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boot->NumSectors = boot->HugeSectors;
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boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
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if (boot->flags&FAT32)
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boot->ClustMask = CLUST32_MASK;
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else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
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boot->ClustMask = CLUST12_MASK;
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else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
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boot->ClustMask = CLUST16_MASK;
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else {
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pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
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boot->NumClusters);
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return FSFATAL;
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}
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switch (boot->ClustMask) {
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case CLUST32_MASK:
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boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
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break;
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case CLUST16_MASK:
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boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
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break;
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default:
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boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
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break;
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}
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if (boot->NumFatEntries < boot->NumClusters) {
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pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
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boot->NumClusters, boot->FATsecs);
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return FSFATAL;
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}
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boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
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boot->NumFiles = 1;
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boot->NumFree = 0;
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return ret;
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}
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int
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writefsinfo(int dosfs, struct bootblock *boot)
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{
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u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
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if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
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!= boot->FSInfo * boot->BytesPerSec
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|| read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
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perr("could not read fsinfo block");
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return FSFATAL;
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}
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fsinfo[0x1e8] = (u_char)boot->FSFree;
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fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
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fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
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fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
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fsinfo[0x1ec] = (u_char)boot->FSNext;
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fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
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fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
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fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
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if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
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!= boot->FSInfo * boot->BytesPerSec
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|| write(dosfs, fsinfo, sizeof fsinfo)
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!= sizeof fsinfo) {
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perr("Unable to write FSInfo");
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return FSFATAL;
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}
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/*
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* Technically, we should return FSBOOTMOD here.
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*
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* However, since Win95 OSR2 (the first M$ OS that has
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* support for FAT32) doesn't maintain the FSINFO block
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* correctly, it has to be fixed pretty often.
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*
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* Therefor, we handle the FSINFO block only informally,
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* fixing it if necessary, but otherwise ignoring the
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* fact that it was incorrect.
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*/
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return 0;
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}
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