why kernel debugging needs two machines?

WINDBG
1

Hi,
lets assume that one does a non intrusive debugging of the kernel, for eg
reading the internal data types of the kernel. does that still warrant two
computers for the same?

in principle why does kernel debugging require two machines and that too
over serial “NULL MODEM” cable connection. is that the way with all other
OS?

kutty

2

You can do limited debugging on a single machine - such as your example
of reading the internal data types of the kernel. I’ve also done
deadlock analysis on a machine with the local kernel debugger enabled.

I used to routinely run with /debug enabled. I’ve stopped doing that
because IF you find an application program with an embedded breakpoint,
the kernel debugger will trap it, but since you only wanted to do local
debugging there is nothing attached to allow you to continue the
breakpoint. I’ve found this with a number of applications, including
Media Player and the Google Toolbar. If you run WITHOUT /debug, data
structures required by the kernel debugger are not present in memory.

Another alternative that “looks like” two machines for debugging
purposes but acts like a single machine is to use a Virtual Machine
product, such as the one available from Microsoft (formerly Connectix)
or from VMware (now part of EMC). My experience (I have used both) is
that VMWare has better performance.

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Kutty Banerjee
Sent: Saturday, July 03, 2004 12:22 PM
To: Kernel Debugging Interest List
Subject: [windbg] why kernel debugging needs two machines?

Hi,
lets assume that one does a non intrusive debugging of the kernel, for
eg reading the internal data types of the kernel. does that still
warrant two computers for the same?

in principle why does kernel debugging require two machines and that
too over serial “NULL MODEM” cable connection. is that the way with all
other OS?

kutty

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3

“kd -kl” (with the current Debugging Tools for Windows) will allow
limited non-intrusive single-machine kernel debugging. You can’t do
anything that actually changes CPU state (like breakpoints, single
stepping, etc), but you can examine global variables, disassemble code, etc.

KM