Re: The difference between programmable and non-programmable logic--if there is one.

From	Andrew Reilly <areilly---@bigpond.net.au>
Newsgroups	comp.arch
Subject	Re: The difference between programmable and non-programmable logic--if there is one.
Date	2011-10-23 03:06 +0000
Message-ID	<9ghem6F1tdU1@mid.individual.net> (permalink)
References	<y7Ioq.5255$ZO7.5060@newsfe05.iad> <j7vs0p$kcr$1@dont-email.me>

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On Sat, 22 Oct 2011 20:52:28 -0500, Del Cecchi wrote:

> The current model is not the only model.  However, it is quite useful.
> It will endure until it is replaced by something more useful.  It would
> be quite easy (Harvard architecture) to separate instructions from data.
>   I think the truth is that, to my surprise, few give much of a hoot
> about security and reliability.

Separating instructions from data doesn't necessarily contribute 
significantly to security *or* reliability.  Now that stacks are not-
executable and code segments are not-writeable, the cool kids are making 
exploits do what they want by chaining little threaded interpreters 
together out of the selection of instructions available just before 
return statements in the attacked programs.  All you need then is a 
buffer overrun that lets you set up a "program" composed of return 
addresses on the stack.  This tactic would, of course, work just as well 
if the code were in a separate memory space, rather than just visible but 
not writeable.

If you want secure and reliable, using this theory, you probably have to 
abandon the whole notion of dynamically reprogrammable (i.e., go 
embedded: turn all computers into "devices").  At that point it doesn't 
matter much if your logic is programmable or not...

You could also restrict yourself (not a large restriction, it seems to 
me) to one of the many programming environments that don't admit that 
mode of failure.  There will still be failures though, just as there are 
failures in non-reprogrammable, Harvard-architected embedded systems: 
people make mistakes.  Most of the recent web (in)security news seems to 
center around protocol errors, which is a design-level problem, not 
especially related to the implementation technology.

Cheers,

-- 
Andrew

Thread

The difference between programmable and non-programmable logic--if there is one. Robert Myers <rbmyersusa@gmail.com> - 2011-10-22 19:14 -0400
  Re: The difference between programmable and non-programmable logic--if there is one. Del Cecchi <delcecchi@gmail.com> - 2011-10-22 20:52 -0500
    Re: The difference between programmable and non-programmable logic--if there is one. Andrew Reilly <areilly---@bigpond.net.au> - 2011-10-23 03:06 +0000
      Re: The difference between programmable and non-programmable logic--if there is one. nmm1@cam.ac.uk - 2011-10-23 09:50 +0100
    Re: The difference between programmable and non-programmable logic--if there is one. Quadibloc <jsavard@ecn.ab.ca> - 2011-10-23 09:22 -0700
  Re: The difference between programmable and non-programmable logic--if kenney@cix.compulink.co.uk - 2011-10-23 11:20 -0500
    Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-23 18:23 -0400
      Re: The difference between programmable and non-programmable logic--if Del Cecchi <delcecchi@gmail.com> - 2011-10-23 19:46 -0500
        Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-23 21:27 -0400
      Re: The difference between programmable and non-programmable logic--if torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-10-24 10:36 +0200
        Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-24 19:01 -0400
          Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-24 22:56 -0400
            Re: The difference between programmable and non-programmable logic--if Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-25 09:18 +0200
          Re: The difference between programmable and non-programmable logic--if "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-10-24 21:08 -0700
            Re: The difference between programmable and non-programmable logic--if Mark Thorson <nospam@sonic.net> - 2011-10-25 18:25 -0800
              Re: The difference between programmable and non-programmable logic--if BGB <cr88192@hotmail.com> - 2011-10-25 19:45 -0700
            Re: The difference between programmable and non-programmable logic--if Mark Thorson <nospam@sonic.net> - 2011-10-29 16:39 -0800
              Re: The difference between programmable and non-programmable logic--if BGB <cr88192@hotmail.com> - 2011-10-30 09:54 -0700
                Re: The difference between programmable and non-programmable logic--if Stefan Monnier <monnier@iro.umontreal.ca> - 2011-10-30 13:50 -0400
                Re: The difference between programmable and non-programmable logic--if BGB <cr88192@hotmail.com> - 2011-10-30 15:12 -0700
          Re: The difference between programmable and non-programmable logic--if Del Cecchi <delcecchi@gmail.com> - 2011-10-25 19:53 -0500
            Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-25 21:29 -0400
              Re: The difference between programmable and non-programmable logic--if Quadibloc <jsavard@ecn.ab.ca> - 2011-10-26 08:57 -0700
                Re: The difference between programmable and non-programmable logic--if Robert Myers <rbmyersusa@gmail.com> - 2011-10-26 11:11 -0700
                Re: The difference between programmable and non-programmable logic--if Del Cecchi <delcecchi@gmail.com> - 2011-10-26 16:43 -0500
                Re: The difference between programmable and non-programmable logic--if jacko <jackokring@gmail.com> - 2011-10-26 14:45 -0700
            Re: The difference between programmable and non-programmable logic--if nmm1@cam.ac.uk - 2011-10-26 07:55 +0100
          Re: The difference between programmable and non-programmable logic--if MitchAlsup <MitchAlsup@aol.com> - 2011-10-26 18:03 -0700
            Re: The difference between programmable and non-programmable logic--if Stefan Monnier <monnier@iro.umontreal.ca> - 2011-10-26 21:43 -0400
  Re: The difference between programmable and non-programmable logic--if there is one. Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-23 23:28 +0200

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