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Date:      Wed, 10 Jul 2013 14:50:19 -0700
From:      Jordan Hubbard <jkh@mail.turbofuzz.com>
To:        asomers@gmail.com
Cc:        hackers@freebsd.org, Julian Elischer <julian@elischer.org>
Subject:   Re: Kernel dumps [was Re: possible changes from Panzura]
Message-ID:  <3592BFB7-0663-4381-AFF5-C7DE0AE16858@mail.turbofuzz.com>
In-Reply-To: <CAOtMX2hLvYnQsZnCn9hC8GjukBy4ad=48yLpqJfuT_7Utq2vEA@mail.gmail.com>
References:  <FDEEB55D-823B-4899-8EEC-7F5306D91F5B@elischer.org> <9890DFF1-892A-4DCA-9E33-B70681154F43@mail.turbofuzz.com> <CAOtMX2hLvYnQsZnCn9hC8GjukBy4ad=48yLpqJfuT_7Utq2vEA@mail.gmail.com>

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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?

Absolutely.  In fact, before the advent of remote network debugging, FW =
was totally the debugging method of choice since firewire target DMA =
lets you do all kinds of useful things (as well as a few things that =
simply scare the security guys to death ;-) ).

My point was more that actually being able to debug a machine over the =
network is such a step up in terms of convenience/awesomeness that if =
anyone is thinking of putting any time and attention into this area at =
all, that's definitely the target to go for.

Looking at =
http://www.opensource.apple.com/tarballs/xnu/xnu-2050.22.13.tar.gz =
there's even reasonable "documentation" on the kernel debugging protocol =
in xnu/osfmk/kdp.  Folks could do worse than try to clone it.  The gdb =
debugger macros in support of it are also in xnu/kgmacros.  None of it =
is going to be 'drop in' for FreeBSD by any stretch of the imagination, =
but it's always easier to get to a destination when you have a map. :-)  =
  Anyone with a Mac can also ""nvram boot-args=3D"debug=3D0x144"" and =
test-drive it around, just to see how it works in actual practice.  See =
also:  =
https://developer.apple.com/library/mac/#documentation/Darwin/Conceptual/K=
EXTConcept/KEXTConceptDebugger/debug_tutorial.html

- Jordan





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