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Date: Thu, 5 Jun 1997 05:51:02 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199706041951.FAA14842@godzilla.zeta.org.au>
To: freebsd-hackers@FreeBSD.ORG, peb@george.lbl.gov
Subject: Re: Virtual address question for VM guru's
Sender: owner-hackers@FreeBSD.ORG
X-Loop: FreeBSD.org
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>I am working on a project where I need to access the address space of a
>process when the process is not necessarily the current process.  I am
>working on a device driver which requires that I copy data directly into
>any writable region in the processes address space.  The user informs the
>kernel of the address range which is then verified and wired before any
>such transfers take place.  This _almost_ all works, if the process is not
>active at the time the device driver attempts to write to the buffer the
>virtual address is giberish.

The corresponding problem for DMA is handled by physio().  This is mostly
transparent to drivers.

Bruce