exception tables in 2.5.55

[Miles Bader <miles@lsi.nec.co.jp>]

I'm building for the v850, which has no MMU.

Starting with 2.5.55, I'm getting link errors like:

  kernel/extable.c:29: undefined reference to `search_extable'

I didn't have to worry about this with earlier kernels, and it looks
like what happened is that previously arch-specific code was
consolidated into the generic kernel.

As far as I can see, the purpose of exception tables is to deal with
unexpected memory access traps and on the v850, this basically can't
happen (there's no MMU, and no way I know of to detect non-existant
memory).  So I'd like to make the generic exception handling stuff
optional.

However, I'm not sure the best way to do this -- I could try to make it
dependent on CONFIG_MMU, but are there non-MMU processors that _can_
usefully use exception tables (in which case perhaps there should just
be a separate CONFIG_EXTABLES or something)?

[Oh, and also, please tell me if I'm mistaken about the purpose of
these tables and really _should_ just implement them.]

Thanks,

-Miles
-- 
Somebody has to do something, and it's just incredibly pathetic that it
has to be us.  -- Jerry Garcia