linux-kernel - Re: Matching hard disks to BIOS boot order

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri, 12 Jun 2009 15:38:24 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Harvey Chapman <hchapman-linux-kernel@...p.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Matching hard disks to BIOS boot order

Alan Cox wrote:
> On Fri, 12 Jun 2009 00:26:16 -0400
> Harvey Chapman <hchapman-linux-kernel@...p.com> wrote:
> 
>> Is there a way to figure out which hard disks match the BIOS boot order?
>>
>> I'm trying to tell a Linux program which disk to use based on the disk 
>> numbers (0,1,...) used by Windows. The best solution I've found so far 
>> is disk serial number, but that hasn't been terribly reliable for other 
>> reasons.
> 
> There is a BIOS interface for this on newer systems, although the kernel
> doesn't capture enough data to make it completely reliable below EDD 3.0
> (in theory if we grabbed a few more bits we could do EDD 1.x as well)
> 
> Most PCs today do EDD 3.0 however
> 

Actually, the best option is to completely forget about BIOS boot order
-- on some systems it can literally change from one boot to the next --
and instead rely on MBR signatures.  As far as I know, Windows requires
all hard drives to have unique signatures and will "rebrand" the disks
to make it so if necessary.

The MBR signature is 4 bytes starting at offset 440 decimal.

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/