kernel build error

linking kernel.debug
i686_mem.o(.text+0xf6a): In function `i686_mem_drvinit':
/usr/src/sys/i386/i386/i686_mem.c:616: undefined reference to `mem_range_softc'
k6_mem.o(.text+0x433): In function `k6_mem_drvinit':
/usr/src/sys/i386/i386/k6_mem.c:181: undefined reference to `mem_range_softc'
mem.o(.text+0x2a3): In function `memioctl':
/usr/src/sys/i386/i386/mem.c:174: undefined reference to `mem_range_softc'
mem.o(.text+0x2b5):/usr/src/sys/i386/i386/mem.c:178: undefined reference to `mem_range_softc'
mem.o(.text+0x2dc): In function `memioctl':
/usr/src/sys/sys/libkern.h:52: undefined reference to `mem_range_softc'
mem.o(.text+0x31d): In function `memioctl':
/usr/src/sys/i386/i386/mem.c:188: undefined reference to `mem_range_attr_get'
mem.o(.text+0x363):/usr/src/sys/i386/i386/mem.c:195: undefined reference to `mem_range_softc'
mem.o(.text+0x3bb):/usr/src/sys/i386/i386/mem.c:206: undefined reference to `mem_range_attr_set'
mem.o(.text+0x408): In function `dev_mem_md_init':
/usr/src/sys/i386/i386/mem.c:216: undefined reference to `mem_range_softc'
mem.o(.text+0x412):/usr/src/sys/i386/i386/mem.c:217: undefined reference to `mem_range_softc'
mem.o(.text+0x417):/usr/src/sys/i386/i386/mem.c:217: undefined reference to `mem_range_softc'
*** Error code 1

Stop in /usr/obj/usr/src/sys/ROAM.
*** Error code 1

Stop in /usr/src.
*** Error code 1