I tried to compile a kernel from ftp.netbsd.org and it failed to link:

ld -Ttext F0000000 -e start -x -o netbsd ${SYSTEM_OBJ} vers.o
vm_fault.o: Undefined symbol "_assert_wait" referred to from text segment
vm_fault.o: Undefined symbol "_thread_block" referred to from text segment
vm_fault.o: Undefined symbol "_assert_wait" referred to from text segment
vm_fault.o: Undefined symbol "_thread_block" referred to from text segment
vm_kern.o: Undefined symbol "_assert_wait" referred to from text segment
vm_kern.o: Undefined symbol "_thread_block" referred to from text segment
vm_map.o: Undefined symbol "_iprintf" referred to from text segment
vm_map.o: Undefined symbol "_indent" referred to from text segment
vm_object.o: Undefined symbol "_iprintf" referred to from text segment
vm_object.o: Undefined symbol "_iprintf" referred to from text segment
vm_object.o: Undefined symbol "_iprintf" referred to from text segment
vm_object.o: Undefined symbol "_indent" referred to from text segment

I might not have the exact wording right, because I just wrote them down
in rough, but I did make sure to note down the right symbols and files.

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