From a recent cross build while linking in src/gnu/usr.bin/gdb53/gdb:

    nbsd-thread.o: In function `nbsd_thread_fetch_registers':
    nbsd-thread.o(.text+0x7c0): undefined reference to `supply_gregset'
    nbsd-thread.o(.text+0x7c8): undefined reference to `supply_fpregset'
    nbsd-thread.o: In function `nbsd_thread_store_registers':
    nbsd-thread.o(.text+0x8dc): undefined reference to `fill_gregset'
    nbsd-thread.o(.text+0x8e8): undefined reference to `fill_fpregset'
    ...

The missing functions are in sparc-tdep.c but are protected by

   #ifdef  USE_PROC_FS

which seems to be undefined.

-- 
Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)