beaglebone: unknown symbols ioremap iounmap

I’m using beaglebon rev. A5. I’ve installed Debian wheezy and it works well.

Now, I’m trying to insert a module but I receive the message “Unknown symbol in module”
and using the “dmesg” command the unknown symbols are the following:

“Unknown symbol omap_iounmap (err 0)”
“Unknown symbol omap_ioremap (err 0)”

in my code I use ioremap () and iounmap () functions.