[Valgrind-users] [Sort of Off-Topic:] Possible skin idea -- Machine code comparato r to help check SCO's claims

[Brian M. <bm...@di...>]

All,

Firstly, let me apologize for airing a half-baked idea that is probably
crazy. Stop reading now if you are easily offended by ideas that are not
well thought out. No flames please.

A couple days ago there was an article on Slashdot discussing a tool created
by Eric S Raymond called the "comparator" that generated md5sum hashes for
every three lines of source code fed into it. See details here:

	http://slashdot.org/article.pl?sid=03/09/09/2129207

The gist of the Slashdot posting was that you could run this tool on the SCO
source tree and on the linux source tree and see how much code was in
common. The Slashdot community response was mixed as you might expect. They
raised two basic issues:

1. SCO would never let anyone run this tool on their source, and legitimate
licensees may be on shaky legal ground if they were to do it.

2. This would only detect complete cut-and-paste code reuse. Something as
simple as a search-and-replace of variable names would throw off the md5sum
hash enough to prevent a match.

I was thinking about this and was curious if something like this could be
used on the generated machine code as executed at runtime. Could a valgrind
skin be written to md5sum the running system at the micro-code level? It
seems like this might be possible with valgrind and/or user-mode linux
and/or some sort of bastardized Bochs/vmware type thing.

Clearly the compiler/optimizer used would affect the generated machine code.
Assuming that you could somehow compile linux using the same
compiler/optimizer as the SCO release, what are some other problems that
would prevent this from being technically feasible?

Thanks for indulging me,
--Brian