Per,
[snip..]
 What do you get when you do:
 $ nm vmlinux | grep linux_banner
 $ readelf -l <dumpfile>
 $ strings -a -t x <dumpfile> | grep "Linux version" 
Here is the result:
nm vmlinux | grep linux_banner
c05bc06b R linux_banner
readelf -l 2013-01-18
Elf file type is CORE (Core file)
Entry point 0x0
There are 2 program headers, starting at offset 52
Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  NOTE           0x000074 0x00000000 0x00000000 0x00000 0x00000     0
  LOAD           0x000074 0xc0000000 0x00000000 0x20000000 0x20000000 RWE 0
strings -a -t x 2013-01-18 | grep "Linux version"
 5bc0df Linux version 3.4.5+ (1@2) (gcc version 4.6.x-google 20120106
(prerelease) (GCC) ) #1 SMP PREEMPT Tue Jan 15 15:51:59 CST 2013
Thanks,
Lei