Date: Tue, 13 Oct 1998 19:23:59 -0700 From: Mike Smith <mike@smith.net.au> To: Terry Lambert <tlambert@primenet.com> Cc: mike@smith.net.au (Mike Smith), karpen@ocean.campus.luth.se, hackers@FreeBSD.ORG Subject: Re: BETA problems... Message-ID: <199810140223.TAA03030@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 14 Oct 1998 01:31:27 -0000." <199810140131.SAA22082@usr08.primenet.com>
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> > > Actually, you could MD5 the first N sectors of the disk using both VM86() > > > I/O and kernel I/O, and if the MD5 matched, you've found your drive. > > > > Given that we've established that disk I/O via our vm86 interface is > > problematic (you were part of this discussion, remember?), this is a > > non-possibility. It'll have to be done by the bootstrap. > > I was, but I don't rememebr why it was problematic. I remember that > there were issues specific to the attempted implementation, and > which I thought were architectural issues not related to whether or > not the access method was a good idea. My take on it was "If it > can be done by Microsoft engineers, it can be done by FreeBSD engineers". It appears that it would involved bogotising our interrupt handling structure. I don't believe we're willing to take that penalty, so you can effectively write off any hope of vm86-based disk I/O from the kernel. > > > If you have two drives that MD5 the same, tweak an unused portion > > > of one of them using VM86() I/O and see which one got tweaked using > > > kernel I/O, and, again, you've found your drive. > > > > Define "unused". > > Assuming that VM86() is an issue, the bytes in the cylinder following > the disklabel and boot sector, whose end is identifiable by 0xaa55. ... where our bootstrap lives? Where the NT bootstrap lives? > Alternately "anything that won't interfere with me booting, and > which I will know to put back later". For example, if we allowed > FreeBSD to boot off both an 0xa5 partition type and another partition > type, then the partition type could be toggled to one or the other > without affecting the bootability of FreeBSD. There's probably a junk field somewhere, sure. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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