linux kernel build system(kbuild)

refs:

http://lxr.linux.no/#linux+v3.10.1/Documentation/kbuild/

=== backgroud ===
- The Linux kernel has amonolithic architecture, which means that the whole kernel code runs in kernel space and shares the same address space.
- not a pure monolithic kernel, it can be extended at runtime using loadable kernel modules
- Even when Linux supports modules, you still need to choose at kernel compile time most of the features that will be built in the kernel image and the ones that will allow you to load specific kernel modules once the kernel is executing.
- an easy and efficient way to manage all these compilation options --  Kernel Build System(kbuild).

=== kbuild main components ===
- Compilation Options: Configuration Symbols
- Defining Configuration Symbols: Kconfig Files
- Storing Symbol Values: .config File
- Compiling the Kernel: Makefiles