Kernel config option

Here's how you can read your running kernel's configuration:

$ zcat /proc/config.gz | less
#
# Automatically generated make config: don't edit
#
CONFIG_X86_32=y
CONFIG_GENERIC_TIME=y
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_STACKTRACE_SUPPORT=y
CONFIG_SEMAPHORE_SLEEPERS=y
CONFIG_X86=y
CONFIG_MMU=y
...

'y' means that the config option is set, commented lines, starting with '#', are not set (for clarity also 'n' is added) and 'm' means that the driver is compiled as a kernel module that can be loaded and unloaded during uptime. Some kernel config options can have different values assigned to them.