How the nios2-linux boot?

How the nios2-linux boot?

I am puzzled about the procedure of nios's boot up.Here is my question:

After reset, which code execute first?

I am afraid head.S is the bootloader of Nios-linux.But not sure.

In arch\nios2nommu\kernel\head.S, this program flush the cache first,then reset peripheral devices.Last, "callr main".

In i386, when boot, linux will prepare a running environment for itself ,

it will initialize memory,start page manage,and so on...

But nois-linux ,just call main? is main user application?

where starting page manage?

help me!

Thanks in advance!