Understanding the Linux Kernel

Appendix C. Source Code Structure

In order to help you to find your way through the files of the source code, we briefly describe the organization of the kernel directory tree. As usual, all pathnames refer to the main directory of the Linux kernel, which is, in most Linux distributions, /usr/src/linux.

Linux source code for all supported architectures is contained in about 4500 C and Assembly files stored in about 270 subdirectories; it consists of about 2 million lines of code, which occupy more than 58 megabytes of disk space.

The following list illustrates the directory tree containing the Linux source code. Please notice that only the subdirectories somehow related to the target of this book have been expanded.

init	Kernel initialization code
kernel	Kernel core: processes, timing, program execution, signals, modules, . . .
mm	Memory handling
arch	Platform-dependent code
—i386	IBM's PC architecture
——kernel	Kernel core
——mm	Memory management
——math-emu	Software emulator for floating point unit
——lib	Hardware-dependent utility functions
——boot	Bootstrapping
———compressed	Compressed kernel handling
———tools	Programs to build compressed kernel image
—alpha	Compaq's Alpha architecture
—s390	IBM's System/390 architecture
—sparc	Sun's SPARC architecture
—sparc64	Sun's Ultra-SPARC architecture
—mips	Silicon Graphics' MIPS architecture
—ppc	Motorola-IBM's PowerPC-based architectures
—m68k	Motorola's MC680x0-based architecture
—arm	Architectures based on ARM processor ...