When building a sparc64 GENERIC kernel on -current (or the netbsd-3
branch), I get:

/usr/src/obj/tooldir.NetBSD-3.99.5-i386/bin/sparc64--netbsd-ld -n -T
/usr/src/sys/arch/sparc64/conf/kern.ldscript -Ttext 01000000 -Tdata
01800000 -e start -S -o netbsd ${SYSTEM_OBJ} ${EXTRA_OBJ} vers.o

/usr/src/obj/tooldir.NetBSD-3.99.5-i386/bin/sparc64--netbsd-ld: section
.data [0000000001800000 -> 000000000184e37f] overlaps section .rodata
[0000000001770340 -> 00000000018c58af]

/usr/src/obj/tooldir.NetBSD-3.99.5-i386/bin/sparc64--netbsd-ld: section
.bss [000000000184e380 -> 000000000189c80f] overlaps section .rodata
[0000000001770340 -> 00000000018c58af]

POWEROFSEVEN, however, builds just fine.  Martin suggested that this
might be an ldscript bug.  Any ideas?