我是菜鸟！nios出现了两个错误：

undefined reference to `nr_flash_erase_sector'以及undefined reference to `nr_flash_write'

提示是### nios-build error: last system call returned256

### (Perhaps you need ".global _start" and "start:")

Died at - line 85.

#    256 cd E:/study/niosstudy/s00 ; nios-build --sdk_directory=E:/study/niosstudy/s00/cpu_sdk -np -s -o boot_rom_contents.srec -b 3145728-3147776 E:/study/niosstudy/s00/cpu_sdk/lib/nios_germs_monitor.s

#

ERROR: Could not build Peripheral Contents for cpu
网上也查到以前别人也发贴问过这同样的问题，可惜没有回帖者，今次本人也发一贴，望各位大侠不吝赐教啊