C considered harmful: was Debian attacker may have used new exploit
Peter Hiscocks
phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org
Fri Dec 5 03:29:53 UTC 2003
Interesting examples. Given that any code can be executed by a Turing
machine (albeit somewhat slowly ;), I would bet that it is possible to do
all these things in a way that separates the code and the data (ie, without
generating code on the fly), but possibly not in a way that satisfies the
current speed requirements. Or it might be that these approaches were taken
at a time when this was the only way to get the necessary speed. So in the
long run, it might even become more feasible to avoid what is effectively
'self modifying code' as processors get faster and memory gets cheaper.
Peter
On Thu, Dec 04, 2003 at 08:20:56PM -0500, Henry Spencer wrote:
> It's highly desirable in cases where performance is critical and there are
> too many different cases to just include one of each in a precompiled
> binary. The classic example is Rob Pike's dynamically-compiled
> implementation of RasterOp -- operations on one-bit-deep frame buffers --
> where the number of cases is the product of a dozen different variables
> each with several values. Similar things can be done for applications
> like network routing.
>
> Similarly, it's heavily used for implementing languages whose full
> generality must be interpretive, but for which special cases can be
> identified at run time and compiled into hard code.
>
> > Isn't it much safer to have a rigid demarcation between code generation and
> > code execution?
>
> Safer, but less powerful.
>
> Henry Spencer
> henry-lqW1N6Cllo0sV2N9l4h3zg at public.gmane.org
>
> --
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Peter D. Hiscocks
Department of Electrical and Computer Engineering
Ryerson University,
350 Victoria Street,
Toronto, Ontario, M5B 2K3, Canada
Phone: (416) 979-5000 Ext 6109
Fax: (416) 979-5280
Email: phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org
URL: http://www.ee.ryerson.ca/~phiscock
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