Date: Sat, 14 Oct 1995 12:10:30 +0200 (UKR) From: Sergey Shkonda <serg@bcs1.bcs.zaporizhzhe.ua> To: bde@zeta.org.au (Bruce Evans) Cc: hackers@freebsd.org Subject: Re: netboot patch Message-ID: <199510141010.AA02527@bcs1.bcs.zaporizhzhe.ua> In-Reply-To: <199510140008.KAA25340@godzilla.zeta.org.au> from "Bruce Evans" at Oct 14, 95 10:08:09 am
next in thread | previous in thread | raw e-mail | index | archive | help
> > >> > Troubles detected when DOS memory managers used > >> > after netboot.com. (I type 'N' when question "Boot from Network") > >> > IMHO there are incorrect switching from P-mode to R-mode at exit. > >> > >> I have heard this from other people as well, but I don't really know > >> what I'm doing incorrectly on the switch back. > > I found this bug. You need to load selector with limit 64k > > to ss, ds, es, fs and fs registers _before_ cleaning PE flag. > > Then shadow registers filled correctly. > > fs and gs need not be switched back because they aren't switched to. > > The standard boot loader probably doesn't need this because it doesn't > support an 'N' question. It seems unlikely that there are any BIOSes > sensitive to the segment limits. It's more likely that there are > BIOSes sensitive to gateA20, and we don't bother switching gateA20 > back and forth. > > Bruce > If this question not supported, then you can't boot from floppy with boot ROM. -- Serg | Relcom: (Sergey Shkonda) | serg@bcs1.bcs.zaporizhzhe.ua
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199510141010.AA02527>