Alan M. Evans wrote:
On Fri, 2007-09-21 at 14:10 +0800, Ed Greshko wrote:
So, the only secure line of code is the noop? :-)
That's funny. But I might argue that a noop is the least secure
instruction, because it can typically be easily replaced (with a jmp or
call, for example) without affecting other code function.
Usually[*], the NOP is the smallest instruction, so it may be used
to nullify other instructions, all of which are made to be multiples
of the size of a NOP. A jump type instruction needs at least
an opcode and an address (even if only relative), so is usually
larger than a NOP. On some machines, some short form of jump
may be just one machine word (a couple of architectures come
to mind, like the Z8000 for instance).
[*] I can't think of a counter example, and it wouldn't make sense
for it to be otherwise.
Mike
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