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Date:      Wed, 18 Nov 1998 12:13:41 +0100
From:      Marius Bendiksen <Marius.Bendiksen@scancall.no>
To:        Matthew Dillon <dillon@apollo.backplane.com>, Terry Lambert <tlambert@primenet.com>
Cc:        rnordier@nordier.com, freebsd-hackers@FreeBSD.ORG
Subject:   Re: FreeBSD on i386 memory model
Message-ID:  <3.0.5.32.19981118121341.00975ac0@mail.scancall.no>
In-Reply-To: <199811172208.OAA29032@apollo.backplane.com>
References:  <199811171806.LAA03809@usr09.primenet.com>

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>    The only differences between a normal call gate and an
>    interrupt is that an interrupt disables interrupts on call
>    (cli equivalent), while a call gate does not, and a

Ehrm. Allow me to note that, unless I'm way off mark here, there is a
difference between an interrupt gate and a trap gate. One of these does
indeed disable interrupts; the other does not. I believe it is the trap
gate which does not.

>    call gate has extra garbage to handle argument copying
>    (which we don't use), while an interrupt does not.

The part about argument copying yields an extra layer of isolation, by
giving you the ability to stick everything on a completely different stack.

>    There are constructs that make call gates sound like a
>    walk in the park, though... a task gate, for example.
>    What a holy mess.

I doubt the divinities played a hand in the creation of *that* particular
mechanism.

>    Interrupt gates are definitely faster.

Okay. I seemed to recall it being the other way around. Obtw; are they only
faster upon entry, or do they return quicker, too?



---
Marius Bendiksen, IT-Trainee, ScanCall AS <marius@scancall.no>

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