Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!tektronix!orca!tekecs!frip!andrew
From: andrew@frip.gwd.tek.com (Andrew Klossner)
Newsgroups: comp.arch
Subject: Re: PEP: Page Execution Priviledge
Message-ID: <10435@tekecs.TEK.COM>
Date: 6 Oct 88 19:21:43 GMT
References: <2550@sultra.UUCP> <76700049@p.cs.uiuc.edu> <16017@ames.arc.nasa.gov>
Sender: andrew@tekecs.TEK.COM
Organization: Tektronix, Wilsonville, Oregon
Lines: 15

[]

	"This mechanism would seem to be a very low overhead means of
	providing "top half of the kernel" type services to a process,
	since it provides a protection mechanism which doesn't require
	a context switch."

It also doesn't give you any of the benefits of a context switch.  If
all you want is naked entry to kernel code, you can usually get it on a
conventional system with little overhead.  For example, the "trap to
kernel" instructions on the M88k take just three cycles.  Then the
kernel is responsible for saving registers, etc.

  -=- Andrew Klossner   (decvax!tektronix!tekecs!andrew)       [UUCP]
                        (andrew%tekecs.tek.com@relay.cs.net)   [ARPA]