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Subject: Re: [OT] Wrapping memory.
To: maze@druid.if.uj.edu.pl (Maciej Zenczykowski)
Date: Sat, 1 Dec 2001 22:24:58 +0000 (GMT)
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <Pine.LNX.4.33.0112012249440.15977-100000@druid.if.uj.edu.pl> from "Maciej Zenczykowski" at Dec 01, 2001 11:03:11 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> I would like to have a 64 KBarray (of char), that's trivial, however what
> I would like is for the last 4 KB [yes thankfully this is exactly one
> page... (assume i386)] to reference the same physical memory as the first
> four.

Yep you can do that.

> Is this at all possible? If so, how would I do this in user space (and
> could it be done without root priv?)?

mmap will do what you need. Create a 60K object on disk and mmap it
at the base address and then 60K further on for 4K. 

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