Date: Thu, 6 Dec 2001 10:35:19 -0700 From: Nate Williams <nate@yogotech.com> To: John Baldwin <jhb@FreeBSD.ORG> Cc: Nate Williams <nate@yogotech.com>, freebsd-hackers@FreeBSD.ORG, Ronald G Minnich <rminnich@lanl.gov> Subject: Re: Re[2]: switching to real mode Message-ID: <15375.44119.475426.615975@caddis.yogotech.com> In-Reply-To: <XFMail.011206092458.jhb@FreeBSD.org> References: <15375.42185.608553.610033@caddis.yogotech.com> <XFMail.011206092458.jhb@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
> >> > I saw an example of switching in real mode in linux' sources (it looks > >> > pretty clear) and thouhgt it is possible to do the same under FreeBSD. > >> > The problem is I'm absolutely lost in FreeBSD's physical memory management > >> > implementation (page tables and directory and so on). > >> > >> That code is quite broken. You need to check out the ones I mentioned > >> earlier. All that the code does in the linux kernel is fail badly. > >> > >> Actually there used to be in freebsd some really nice code for popping > >> into real mode and back again. It was to support calling BIOS for certain > >> things. > > > > I believe the code is still there, and it's used for APM bios calls, > > if I remember correctly. > > It uses VM86 mode, not real mode. Going back and forth to real mode is too > expensive. Ahh, that's right. However, if I remember right, in older versions of FreeBSD it did the real-mode switch, because we didn't have the VM86 code. (This would be prior to FreeBSD 4). Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?15375.44119.475426.615975>