linux-kernel - Re: [PATCH 1/2] char/mem: Add /dev/io (v2)

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Message-ID: <20120208092611.49ada8c5@pyramind.ukuu.org.uk>
Date:	Wed, 8 Feb 2012 09:26:11 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Adam Jackson <ajax@...hat.com>
Cc:	linux-kernel@...r.kernel.org, arnd@...db.de,
	gregkh@...uxfoundation.org
Subject: Re: [PATCH 1/2] char/mem: Add /dev/io (v2)

> Yeah, I'll be sure to do that right as soon as I can stop supporting the 
> vesa driver.  Until that time I don't really have any choice but to 
> expose the whole of I/O port space, since I have no idea what the video 
> BIOS is going to touch.

I would be surprised if you couldn't make a very good guess, and many
things it might want to touch are things that need blocking/emulating
anyway.

> I don't disagree with wanting to limit access to these services, but 
> /dev/io is at least somewhat containable, whereas iopl is insane.

They are both equally insane and have effectively identical security
semntics. Continuing to use iopl is both faster and avoids adding a kernel
API however. Even better it's x86 specific so that piece of manure
doesn't escape onto other platforms without the legacy vesa mess.

Alan
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