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From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199602081838.TAA29988@labinfo.iet.unipi.it>
Subject: Re: kern/383
To: wollman@freefall.freebsd.org (Garrett Wollman)
Date: Thu, 8 Feb 1996 19:38:03 +0100 (MET)
Cc: fredriks@mcs.com, wollman@freefall.freebsd.org,
        freebsd-bugs@freefall.freebsd.org
In-Reply-To: <199602081659.IAA01134@freefall.freebsd.org> from "Garrett Wollman" at Feb 8, 96 08:59:37 am
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> Synopsis: dd to from /dev/mem panics the machine.
> 
> State-Changed-From-To: open-closed
> State-Changed-By: wollman
> State-Changed-When: Thu Feb 8 08:58:24 PST 1996
> State-Changed-Why: 
> It is an error to dd from random regions of /dev/mem.  All
> sorts of nasty things can happen.

I have experienced a similar problem. It occurred when reading from
/dev/mem with "dd" from within an xterm. The same thing from a vty
worked fine, as it did a C program doing random reads from the whole
memory space running from within an xterm.

In my case I don't think the crashes were caused by underlying hw
problems, otherwise they would only depend on the phys. address, not on
the program that uses it or other context-dependant issues. And how can
reads from phys. mem be harmful ?

I would at least like to know why it crashes the system.

	Thanks
	Luigi