During the
2.4 series of the
Linux Kernel, this option was expanded to contain options to enable debugging on some areas of the kernel. Debugging high memory, memory allocations, and memory mapped I/O, which are of no use in production systems, along with debugging spinlocks and verbose reporting of BUG() options compliment the venerable SysRQ key, which has probably saved countless filesystems from lengthy fscks after a
panic.
Kernel hacking is also what a
kernel hacker does.