Linux kernel porting (i)--linux kernel introduction

One: The origins of Linux

Linux is an open-source computer operating system kernel. It is a Unix-like operating system written in C and POSIX compliant, and Linux was originally developed by Finnish hacker Linus Torvalds to try to provide free and free Unix-like operating systems on the Intel x86 architecture. The program began in 1991 with the help of some minix hackers in the early stages of the program, and today countless programmers around the world are helping out with the program for free.

II: Linux kernel version

(1) linux0.01. First edition, followed by the 0.02, 0.03, 0.10, 0.11, 0.12, 0.95, 0.96, 0.97, 0.98, 0.99, and subsequent 1.0.

(2) linux0.11. Many of the Linux kernel source code parsing books are based on this version of the original

Originally said. "The art of graphic Linux kernel design"

(3) linux2.4. Compared to the modern version, many classic books are in the 2.4 version

For example, "LDD3". The late kernel of linux2.4 is often used in previous years

met with useful.

(4) Early linux2.6. The early 2.6 and the late 2.4 kernel are quite similar.

(5) Late linux2.6. The late kernel of 2.6 has some changes in the earlier kernel, especially the drive

The location of the related parts and some header files. The late kernel of 2.6 is now more of a master

Flow.

(6) Linux3.x 4.x, now the latest version is linux4.7.1

Three: kernel and distribution differences

Difference: Kernel is the kernel of the operating system, kernel is responsible for implementing the core of the operating system

Function (Resource management module, such as memory management, scheduling system ...) ), the kernel does not include

Application. So it's not possible for a kernel person to do anything because people do everything

The appropriate application to complete. So the people who sell the operating system put the kernel and some common

Applications are packaged together for regular users, which is the release of the operating system

(i.e. the operating system in the ordinary sense).

(1) There is only one kernel. www.kernel.org

(2) There are a lot of distributions. such as Ubuntu, Redhat, SuSE, CentOS ...

Four: Modular design of the Linux kernel

1: What is modular design

(1) Because the Linux kernel is very large, the code is very large, a lot of things, if the design is completely

Designed as one (tightly coupled between individual files and functions), the complexity exceeds the

can understand the scope. So modular design is also a necessity.

(2) Modular design is the core of each function module in the code is independent of each other, such as

There is no reference to the global variables between the dispatch system and the memory management system, even

The number of calls to each other is also very small, even if there is an interface specification is followed. The modular Design

The purpose is to realize the loose coupling of functional modules.

2: The embodiment of modular design

(1) can be cropped when configured. The Linux kernel can be configured before compiling, and the configuration can be configured with the choice of the thousands of modules that make up the kernel each one or the other. After that, there are a few more details to configure.

(2) Modular compilation and installation. For ease of operation, gradually from the static upgrade to a dynamic upgrade (no need to restart the system, but also do not need to re-burn the system). This dynamic upgrade is also supported by modularity.

(3) Use conditional compilation in source code. This has already been seen in the Uboot .

Linux kernel porting (i)--linux kernel introduction