creating Nios program, loading, booting ...

I have successfully got Linux up & running with my Atlas(de0-nano-soc) board - application works , yada yada yada ...

- but would like to offload some processing from the Arm(s) - to a NIOS sub processor

essentially hold the NIOS in reset - upload code (from linux ) - release NIOS (boot)

- I have read over an458.pdf (alternate boot methods) & examined the code -

but am still at a loss of how to produce file with a obvious NIOS entry point ?

should i be using an .elf ? sof ?

my code is quite small - is the nios environment really the best way ?

(test program is only 3 lines, proved ARM code is ~100 lines)

any ideas ? links ? or code ?