From owner-freebsd-hackers Thu Dec 6 11:34:21 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from salmon.maths.tcd.ie (salmon.maths.tcd.ie [134.226.81.11]) by hub.freebsd.org (Postfix) with SMTP id 5D71B37B405; Thu, 6 Dec 2001 11:34:19 -0800 (PST) Received: from walton.maths.tcd.ie by salmon.maths.tcd.ie with SMTP id ; 6 Dec 2001 19:34:18 +0000 (GMT) To: John Baldwin Cc: Dmitry Konyshev , freebsd-hackers@FreeBSD.org Subject: Re: switching to real mode In-Reply-To: Your message of "Thu, 06 Dec 2001 09:24:58 PST." Date: Thu, 06 Dec 2001 19:34:12 +0000 From: Ian Dowse Message-ID: <200112061934.aa63585@salmon.maths.tcd.ie> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG In message , John Baldwin writes: >The short form is htat you need to hack the cpu_halt to call a function that >puts a stub down in low memory, and calls it. This code needs to be mapped 1:1 >so that the logical address == physical address. The first thing you will Yeah, I attempted something like this a few years ago without much success. I've just updated the code to compile on -stable, and it seems to half-work in that it appears to successfully switch to real mode and clear the screen using the video BIOS, but then it just hangs. That's pretty close to what I remember it doing originally, although I think it might have worked before the VM86 stuff was enabled by default in FreeBSD. Getting this sort of code to work reliably is almost impossible... Source is at http://www.maths.tcd.ie/~iedowse/FreeBSD/diskboot/ (loading the resulting KLD immediately shuts down to real mode). Ian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message