Hey Sean,
I'm just a newbie user, but I think if you look at your map file it will probably tell you that you haven't set up that segment of memory. If that's the case, check this page http://rtsc.eclipse.org/docs-tip/Memory_Management and it will tell you how to use the platform wizard to set up that memory. That page also has a lot of good info on the inards of the platform.xdc files and linker cmd files. Hope this helps.
Dave