Date:	Thu, 13 Jan 2000 18:00:16 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	Martin Stromberg <Martin DOT Stromberg AT lu DOT erisoft DOT se>
cc:	DJGPP <djgpp AT delorie DOT com>
Subject:	Re: Problems with protected_mode_int
In-Reply-To:	<200001131558.QAA14542@spica-144.lu.erisoft.se>
Message-ID:	<Pine.SUN.3.91.1000113175705.12754K-100000@is>
MIME-Version:	1.0
Reply-To:	djgpp AT delorie DOT com
Errors-To:	dj-admin AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

On Thu, 13 Jan 100, Martin Stromberg wrote:

> > This will most probably crash, for several good reasons:
> > 
> >   - stack is allocated off the DS selector whose access rights forbid 
> >     executing any address accessed via that selector;
> > 
> >   - the only segment register that is guaranteed to be loaded with the 
> >     application's selector is CS, so you cannot trust SS.
> 
> Are you saying the base and offsets of CS is different than those of DS?
> If yes, then it won't work. 

The base and limit are the same, but not the access rights.  If you 
pass _my_ss() to the functions which installes the handler, it will
use the SS (actually, the DS) selector, and trigger a GPF due to access
rights.

In addition, in this specific case, the user reported he was using DJGPP 
v1.x, where SS was loaded with a different selector (which was the reason 
why -fomit-frame-pointer didn't work).

- Raw text -