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Change mismatch of bytes 11 to 90 to be a warning, not an error, and

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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.
This commit is contained in:
gdt 2007-03-19 18:30:40 +00:00
parent 5deb14ad9d
commit 9da1e4cf5f
1 changed files with 19 additions and 8 deletions
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27
sbin/fsck_msdos/boot.c
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@ -1,4 +1,4 @@
/* $NetBSD: boot.c,v 1.12 2007/03/10 00:30:36 hubertf Exp $ */
/* $NetBSD: boot.c,v 1.13 2007/03/19 18:30:40 gdt Exp $ */
/*
* Copyright (C) 1995, 1997 Wolfgang Solfrank
@ -35,7 +35,7 @@
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: boot.c,v 1.12 2007/03/10 00:30:36 hubertf Exp $");
__RCSID("$NetBSD: boot.c,v 1.13 2007/03/19 18:30:40 gdt Exp $");
#endif /* not lint */
#include <stdlib.h>
@ -53,6 +53,7 @@ readboot(int dosfs, struct bootblock *boot)
u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
u_char backup[DOSBOOTBLOCKSIZE];
int ret = FSOK;
int i;
if (read(dosfs, block, sizeof block) < sizeof block) {
perr("could not read boot block");
@ -158,12 +159,22 @@ readboot(int dosfs, struct bootblock *boot)
}
backup[65] = block[65]; /* XXX */
if (memcmp(block + 11, backup + 11, 79)) {
/* Correct? XXX */
pfatal("backup doesn't compare to primary bootblock");
if (alwaysno)
pfatal("\n");
else
return FSFATAL;
/*
* XXX We require a reference that explains
* that these bytes need to match, or should
* drop the check. gdt@ has observed
* filesystems that work fine under Windows XP
* and NetBSD that do not match, so the
* requirement is suspect. For now, just
* print out useful information and continue.
*/
pfatal("backup (block %d) mismatch with primary bootblock:\n",
boot->Backup);
for (i = 11; i < 11 + 90; i++) {
if (block[i] != backup[i])
pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
i, block[i], backup[i]);
}
}
/* Check backup FSInfo? XXX */
}