Date: Fri, 16 Aug 2002 11:50:06 -0700 (PDT) From: "Artem 'Zazoobr' Ignatjev" <timon@memphis.mephi.ru> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/20633: fdisk doesn't handle LBA correctly Message-ID: <200208161850.g7GIo6ZQ047726@freefall.freebsd.org>
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The following reply was made to PR bin/20633; it has been noted by GNATS.
From: "Artem 'Zazoobr' Ignatjev" <timon@memphis.mephi.ru>
To: Bruce Evans <bde@zeta.org.au>, freebsd-gnats-submit@FreeBSD.org
Cc:
Subject: Re: bin/20633: fdisk doesn't handle LBA correctly
Date: Fri, 16 Aug 2002 22:42:35 +0400
On Sat, Aug 17, 2002 at 03:56:57AM +1000, Bruce Evans wrote:
> On Fri, 16 Aug 2002, Artem 'Zazoobr' Ignatjev wrote:
> > Hi, if I understand what jhb said in audit trail, following patch
> > should solve the issue. Stephen, if it still bothers you, could you try
> > it?
> >
> > --- sbin/i386/fdisk/fdisk.c Fri Aug 16 16:24:27 2002
> > +++ sbin/i386/fdisk/fdisk.c Fri Aug 16 16:33:28 2002
> > @@ -468,13 +468,21 @@
[skip]
> > - printf("\tbeg: cyl %d/ head %d/ sector %d;\n\tend: cyl %d/ head %d/ sector %d\n"
[skip]
> > + /*
> > + * if C/H/S of start or end are all set to 0xff, then C/H/S don't have
> > + * enough bits to hold the address, and one should use LBA instead.
> > + */
> > + if ((partp->dp_scyl != 0xff || partp->dp_ssect != 0xff ||
> > + partp->dp_shd != 0xff) && (partp->dp_ecyl != 0xff ||
> > + partp->dp_esect != 0xff || partp->dp_ehd != 0xff))
> > + printf("\tbeg: cyl %d/ head %d/ sector %d;\n"
[skip]
>
> Fdisk should print these values, at least optionally, since they are needed
> for debugging. The magic values might be non-magic on old systems.
Debugging WHAT? And, I can hardly imagine such a situation inside hard
drives & slice tables.
> Also, the usual magic number of cylinders seems to be 1022, not 1023.
I disagree. Now i'm hacking fdisk to work with extended slices, it can
now dump partition table of the whole disk, since this inability dove me
mad when I was installing FreeBSD into extended (there was another issue
to make it boot :-) ), when i'll finish it, I'll send the proposed
sources/patches to -hackers, also I hope I make boot2 more friendly to
extended slices (I've got already hack for boot1 to allow booting from
bootmanagers ala ntloader).
Take a look at the dump (I've cut all entries regarding extendeds below
the top-level slicetable, since them all take space, but are of no
interest now)
Script started on Fri Aug 16 22:23:06 2002
******* Working on device /dev/ad4 *******
parameters extracted from in-core disklabel are:
cylinders=7476 heads=255 sectors/track=63 (16065 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=7476 heads=255 sectors/track=63 (16065 blks/cyl)
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 6 (Primary 'big' DOS (> 32MB)),
start 63, size 2088387 (1019 Meg), flag 0
beg: cyl 0/ head 1/ sector 1;
end: cyl 129/ head 254/ sector 63
The data for partition 2 is:
sysid 7 (OS/2 HPFS, NTFS, QNX-2 (16 bit)),
start 2088450, size 8385930 (4094 Meg), flag 80 (active)
beg: cyl 130/ head 0/ sector 1;
end: cyl 651/ head 254/ sector 63
The data for partition 3 is:
sysid 131 (Linux filesystem),
start 10474380, size 4192965 (2047 Meg), flag 0
beg: cyl 652/ head 0/ sector 1;
end: cyl 912/ head 254/ sector 63
The data for partition 4 is:
sysid 15 (Extended DOS, LBA),
start 14667345, size 105435855 (51482 Meg), flag 0
beg: cyl 913/ head 0/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 5 is:
sysid 130 (Linux swap or Solaris x86),
start 14667408, size 256977 (125 Meg), flag 0
beg: cyl 913/ head 1/ sector 1;
end: cyl 928/ head 254/ sector 63
The data for partition 7 is:
sysid 131 (Linux filesystem),
start 14924448, size 16771797 (8189 Meg), flag 0
beg: cyl 929/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 9 is:
sysid 7 (OS/2 HPFS, NTFS, QNX-2 (16 bit)),
start 31696308, size 40965687 (20002 Meg), flag 0
beg: cyl 1023/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 11 is:
sysid 12 (FAT-32, LBA),
start 72662058, size 7389837 (3608 Meg), flag 0
beg: cyl 1023/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 13 is:
sysid 165 (FreeBSD/NetBSD/386BSD),
start 80051958, size 8401932 (4102 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63
The data for partition 15 is:
sysid 7 (OS/2 HPFS, NTFS, QNX-2 (16 bit)),
start 88453953, size 25398702 (12401 Meg), flag 0
beg: cyl 1023/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
Script done on Fri Aug 16 22:23:06 2002
A-ha! Better see once, than hear many times: magic value for start is
1023/1/1, and for end is 1023/254/63, but note my FreeBSD slice - it was
created using linux fdisk, but even these strange values works ok.
> Writing the correct magic numbers is more interesting. fdisk(8) doesn't
> support it directly. You may have to change the C/H/S values to the magic
> ones manually.
Is there any papers on the subject? All my knowledge was obtained experimentally, watching how my dad revives dead hds....
It looks like the magic is cyl=1023, regardless of h/s values...
Sinceherely yours, Artem 'Zazoobr' Ignatjev.
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