I am using FreeRTOS on a NiosII processor. We had problems to use the NiosII port of FreeRTOS because symbols which are defined in assembler files were not accessible for the linker (error message: undefined reference to …).
My solution: the assembler file port_asm.S can be renamed to port_asm.s because there are no preprocessor commands inside. The new file extension means that the preprocessor will not process this assembler file.
I hope I could help someone with this information…