Compare the session with gdb53 and gdb6...

# /home/pavel/obj/i386/gnu/usr.bin/gdb6/gdb/gdb /netbsd 
GNU gdb 6.5
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386--netbsdelf"...(no debugging symbols found)

(gdb) target kcore
#0  0xc09cada0 in lwp0 ()
(gdb) kvm proc 0xceccd784
#0  0xceccd784 in ?? ()
(gdb) bt
#0  0xceccd784 in ?? ()
#1  0xc5532024 in ?? ()
#2  0x00000000 in ?? ()
(gdb) # 


# /home/pavel/obj/i386/gnu/usr.bin/gdb53/gdb/gdb /netbsd
GNU gdb 5.3nb1
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386--netbsdelf"...(no debugging symbols found)...
(gdb) target kcore /dev/mem
#0  0xc09cada0 in lwp0 ()
(gdb) proc 0xceccd784
(gdb) bt
#0  0xceccd784 in ?? ()
#1  0xc044cda7 in ltsleep ()
#2  0xc0430949 in kevent1 ()
#3  0xc0430ffd in sys_kevent ()
#4  0xc04fe03e in syscall_plain ()