Date: Mon, 01 Apr 2002 10:28:30 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Dmitry Konyshev <daemon@agava.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: finding out boot device Message-ID: <3CA8A6CE.DBB6CEEB@mindspring.com> References: <84434325847.20020401203442@agava.com>
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Dmitry Konyshev wrote: > Could anyone please tell me if there's any way to find out which > device the system booted from in a user application. The loader > sets loaddev and currdev vars, but I see no way to transfer them to > the user environment. Luigi Rizzo posted patches to communicate this information from the loader to sysctl space. Note that it's not definitive, since you don't get a sure mapping between BIOS devices and protected mode OS device drivers (for obvious reasons). One way to obtain this information is to write a program that uses vm86() calls to read the first N sectors of a BIOS disk, then read the same area using the protected mode drivers. When you get a unique MD5 hash match between the BIOS and the boot device, you're there. For CDROM boots, where the floppy image is in a RAM disk that is wedged into the BIOS calls to replace the floppy, after the boot, the BIOS wedge is destroyed, so that's lost. I guess you could infer this one, if you got no MD5 matches. Good luck with the code; normally, wanting to know this information comes with a bad reason for the desire. 8-). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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