Re: Excellent job on the firewire support!

From: Doug Rabson <dfr_at_nlsystems.com>
Date: Wed, 21 Jul 2004 15:59:01 +0100
On Wed, 2004-07-21 at 15:41, Andrew Gallatin wrote:
> Doug Rabson writes:
>  > Actually thats the only downside of dcons. It doesn't cut in until the 
>  > firewire controller attaches. It relies on the fact that the fwohci 
>  > driver allows access to physical memory from any node on the bus 
>  > (implemeted in hardware so you can examine the memory of a hung 
>  > machine). The dconschat program uses this feature to access the dcons 
>  > ring buffers in the target machine.
> 
> Does remote access to physical memory require dcons to be loaded
> on the target?

No. The remote access to physical memory is a hardware-implemented
feature of the firewire ohci hardware. Its enabled in fwohci_attach().
In the long term, I would like to restrict this a bit but right now all
you have to have is fwohci loaded on the target machine.

> 
> If no, assuming I had a Windows or Linux box on the firewire bus, would it be
> possible to access physical memory from a different OS?

Windows XP has some kind of firewire debug driver that you might have to
load (I haven't read the docs on that). I don't think the linux driver
enables physical access by default but it would be easy to hack it in
(just write all ones to the right fwohci register).
Received on Wed Jul 21 2004 - 12:59:10 UTC

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