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Date:      Fri, 1 Aug 2003 16:01:57 -0700
From:      Marcel Moolenaar <marcel@xcllnt.net>
To:        deischen@freebsd.org
Cc:        current@freebsd.org
Subject:   Re: NVidia glx stuff dies in sysarch(I386_SET_LDT, ...)
Message-ID:  <20030801230157.GA6323@dhcp01.pn.xcllnt.net>
In-Reply-To: <Pine.GSO.4.10.10308011847230.18146-100000@pcnet5.pcnet.com>
References:  <200308020647.18039.davidxu@FreeBSD.org> <Pine.GSO.4.10.10308011847230.18146-100000@pcnet5.pcnet.com>

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On Fri, Aug 01, 2003 at 06:51:33PM -0400, Daniel Eischen wrote:

> > LUCODE_SEL is used by kernel to load _ucodesel to user %cs
> > LUDATA_SEL is used by kernel to load _udatasel to user %ds, %es, %fs, %gs.
> > I didn't check other ABIs, but setting to a fixed location of LDT in userland
> > is also a bad idea, I think it will conflict with thread library soon,
> > it is better to use dynamic allocating facility newly added in i386_set_ldt.
> 
> Perhaps we need to rethink the interface and disallow
> specification of any ldt; only allow dynamic.  We would
> need a different method of setting an array of them, though.

Why not allow setting a specific entry when it's currently unused
and not reserved by us?
We can simply fail if the process is trying to set a LDT entry that's
currently being used or is reserved by us. The only case that causes
problems is when an existing LDT entry is overwritten by another
consumer.

-- 
 Marcel Moolenaar	  USPA: A-39004		 marcel@xcllnt.net



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