From owner-freebsd-fs@FreeBSD.ORG  Mon Sep  5 06:46:13 2005
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To: Jeb Campbell <jebc@c4solutions.net>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Mon, 05 Sep 2005 01:44:33 CDT."
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Date: Mon, 05 Sep 2005 08:46:11 +0200
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Cc: freebsd-fs@freebsd.org
Subject: Re: kernel newb -- read/write to a local file from in kernel 
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In message <431BE951.4070101@c4solutions.net>, Jeb Campbell writes:
>I'm trying to learn about kernel programming and as a weekend project 
>I've started writing a Netgraph to file/dev module.
>
>The Netgraph stuff was pretty easy, but I'm at a loss on the file access 
>part as I've never done anything in-kernel.
>
>After much searching (most of it not knowing what I was looking for), I 
>think that I'm looking for something like "Vnode interface mechanics, 
>write to a local file" as taught in Mr. McKusick's "FreeBSD Kernel 
>Internals: An Intensive Code Walkthrough".
>
>I've looked at nullfs/null_vnops.c, but I think that is more of a 
>pass-through example.  Does anyone know of any online code that shows 
>the process of opening a file/device for read/write?

In the spirit of education I won't tell you "how to" but only "where
to look":  ktrace, coredumps and accounting all writes to files
from the kernel.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.