Undefined symbol "__sbmaskrune" -> box doesn't even boot

[Ewald Jenisch]

Hi,

After downgrading my kernel (i.e. cvsup-ing the 6-STABLE sources as
per end of August), re-building kernel and system as per the handbook
I end up with a problem that neither the new nor the old kernel boots.

After doing a "make installkernel..." and rebooting the box to
single-user mode I went through the usual step of "mergemaster -p" and
"make installworld". Soon after "make installworld" the process
stopped with an error

/libexec/ld-elf.so.1: Undefined symbol "__sbmaskrune"

So I rebooted to the old kernel (i.e. 6 at the loader prompt and "boot
kernel.old") but I couldn't even get to the shell prompt: When
single-user mode asks me for the program to be executed (default
/bin/sh) as soon as I hit enter I get the same error message as above.

Does anybody out there know how I could get up the box running again??

Thanks much in advance for your help,
-ewald