using Dual Port Memory with simple Nios II Qsys system

If you are trying to do very specific assignments of code and data to specific memory blocks (eg because of the way they need to be dual-ported, or because you want all code and data accesses to by 'tightly coupled') then you'll almost certainly need to write your own linker script.

In particular, if you want the code to be 'pure' (ie contain no data), the .rodata (etc) will need to linked with the read-write data and not the code. You also can't use the Altera-built gcc4 as that puts switch statement jump tables directly into the code segment.