CONFIG_KERNELBASE is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

Address of the base of kernel code


Linux Kernel Configuration
└─>Address of the base of kernel code
In linux kernel since version 2.6.18 (release Date: 2006-09-19)  
Typically on m68k systems the kernel will not start at the base
of RAM, but usually some small offset from it. Define the start
address of the kernel here. The most common setup will have the
processor vectors at the base of RAM and then the start of the
kernel. On some platforms some RAM is reserved for boot loaders
and the kernel starts after that. The 0x400 default was based on
a system with the RAM based at address 0, and leaving enough room
for the theoretical maximum number of 256 vectors.