How to share code between /gnu-nat.c with [gdb]/gdbserver/gnu-hurd-low.c?

Hi all,

When I working with porting gdbserver to GNU/Hurd I found I alway need
to duplicate code from [gdb]/gnu-nat.c to my new file
[gdb]/gdb/server/gnu-hurd.low.c. There are too many functions and
structures can be shared between the two file only need a little
change or even without any change.

I don't have good ideal to share the code, can you give me any
suggestions? Thank you.

-- 
Yue Lu (陆岳)