From owner-freebsd-hackers@FreeBSD.ORG Wed Jul 10 22:50:27 2013 Return-Path: Delivered-To: hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id A8EBF305 for ; Wed, 10 Jul 2013 22:50:27 +0000 (UTC) (envelope-from bakul@bitblocks.com) Received: from mail.bitblocks.com (ns1.bitblocks.com [173.228.5.8]) by mx1.freebsd.org (Postfix) with ESMTP id 8DF881FE2 for ; Wed, 10 Jul 2013 22:50:27 +0000 (UTC) Received: from bitblocks.com (localhost [127.0.0.1]) by mail.bitblocks.com (Postfix) with ESMTP id 621EFB827; Wed, 10 Jul 2013 15:42:29 -0700 (PDT) To: Jordan Hubbard Subject: Re: Kernel dumps [was Re: possible changes from Panzura] In-reply-to: Your message of "Wed, 10 Jul 2013 14:50:19 PDT." <3592BFB7-0663-4381-AFF5-C7DE0AE16858@mail.turbofuzz.com> References: <9890DFF1-892A-4DCA-9E33-B70681154F43@mail.turbofuzz.com> <3592BFB7-0663-4381-AFF5-C7DE0AE16858@mail.turbofuzz.com> Comments: In-reply-to Jordan Hubbard message dated "Wed, 10 Jul 2013 14:50:19 -0700." Date: Wed, 10 Jul 2013 15:42:29 -0700 From: Bakul Shah Message-Id: <20130710224229.621EFB827@mail.bitblocks.com> Cc: asomers@gmail.com, hackers@freebsd.org, Julian Elischer X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Jul 2013 22:50:27 -0000 On Wed, 10 Jul 2013 14:50:19 PDT Jordan Hubbard wrote: > > On Jul 10, 2013, at 1:04 PM, asomers@gmail.com wrote: > > > I don't doubt that it would be useful to have an emergency network > > stack. But have you ever looked into debugging over firewire? > > My point was more that actually being able to debug a machine over the networ > k is such a step up in terms of convenience/awesomeness that if anyone is thi > nking of putting any time and attention into this area at all, that's definit > ely the target to go for. You have to use this just once to see how convenient it is! For a previous company James Da Silva did this in 1997 by adding a network console (IIRC in a day or two). A new ethernet type was used + a host specific ethernet multicast address so you could connect from any machine on the same ethernet segment. Either as a remote console for the usual console IO & ddb, or to run remote gdb. Quite insecure but that didn't matter as this was used in a test network. There was no emegerency network stack; just a polling function added to an ethernet driver since this had to work even when the kernel was on the operating table under anaesthetic! No new gdb hacks were necessary since the invoking program set things up for it. If I was doing this today, I'd probably still do the same and make sure that the interface used for remote debugging is on an isolated network.