On Sat, 2007-07-21 at 15:21 -0400, Robert P. J. Day wrote:
> again, probably displaying my abject ignorance, but i wrote a
> trivial module that tries to "var % 15", and i get:
>
> WARNING: "__moddi3" undefined!
>
> and, not surprisingly, when i try to insmod:
>
> insmod: error inserting 'seq.ko': -1 Unknown symbol in module
>
> (using 16 rather than 15 works fine, as i assume that the modulus
> call is simply replaced by an optimized bitwise comparison.)
>
> so ... from where comes __moddi3? i know there are places in the
> kernel source tree that do non-power-of-2 moduli, and they work fine,
> no? thanks.
let me guess, 32 bit kernel, and var is 64 bit?
gcc translates that into a libgcc call, which we _explicitly_ do not
have because 64bit divisions are expensive!
use do_div().
16 works because gcc translates that into a right shift.
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