Linux操作系统的可移植性研究

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"Linux: 一个可移植的操作系统" 在这篇论文中，Linus Torvalds 探讨了 Linux 操作系统的可移植性问题，该问题是在将操作系统移植到多种 CPU 和总线架构时所发现的。论文中还讨论了软件接口的问题。 Linux 是一个开源的操作系统，由 Linus Torvalds 于 1991 年创建。它的设计目标是创建一个免费、开放、可移植的操作系统，可以运行在多种硬件平台上。 Linux 的可移植性是其一个重要特点，它可以运行在多种 CPU 和总线架构上，如 Alpha、Sparc 等。论文中，Linus Torvalds 首先介绍了 Linux 操作系统的背景和发展历史，然后讨论了 Linux 的可移植性问题。在讨论中，Linus Torvalds 指出，Linux 的可移植性是通过使用模块化的设计和抽象层来实现的。模块化的设计使得 Linux 可以轻松地移植到不同的硬件平台上，而抽象层则使得 Linux 可以屏蔽底层硬件的差异。论文还讨论了 Linux 的软件接口问题。软件接口是指操作系统提供给应用程序的接口，用于访问操作系统的服务。Linus Torvalds 指出，Linux 的软件接口是通过使用系统调用和库函数来实现的。系统调用是操作系统提供给应用程序的接口，用于访问操作系统的服务，而库函数则是操作系统提供给应用程序的函数库，用于实现某些功能。本篇论文对 Linux 操作系统的可移植性和软件接口进行了深入的讨论，为我们提供了关于 Linux 操作系统的深入了解。资源链接： * Linux 官方网站：https://www.linux.org/ * Linus Torvalds 的个人网站：https://torvalds.com/ 知识点： * Linux 操作系统的可移植性 * Linux 操作系统的设计目标 * 模块化的设计 * 抽象层 * 软件接口 * 系统调用 * 库函数 * Linux 操作系统的发展历史 * Linus Torvalds 的贡献延伸阅读： * Linux 操作系统的架构 * Linux 操作系统的安全机制 * Linux 操作系统的应用场景 * Linux 操作系统的发展趋势

The problem with abstraction layers is that they add overhead when concepts

have to be translated from layer to layer. This has generally been onereasonhard-

ware abstractio n layers have been shunned: they add extra processing that could be

avoided by pro gramming directly on the bare hardware or software interfa ce. This

has to be taken into account, especially as one of the goals o f Linux in the ﬁrst place

was to be eﬃcient.

2Linux—theDesignandImplementation

Unlike most modern research operating systems, the Linux approach to operating

systems is very pragmatic, and rather than concentrating on the design of a new

kernel the focal point has been on a solid and eﬃcient implementation.Insteadof

throwing away pr oven concepts they have been reﬁned in new ways. [Tor93]

The L inux design is based on three main design issues that have directly inﬂu-

enced the implementation. The main issues are:

• Simplicity. The obviousness of this sometimes means that it is overlooked, but

an operating system kernel is a complex entity that has to be able to work

in an uncontro lled and potentially even hostile environment. Programming

errors in the operating system are much less acceptable than in mostnormal

programs, and the security issues are paramount. A complex design is harder

to verify against either errors or security issues, so simplicity o f the basic

services is required.

• Eﬃciency. The kernel is involved with almost all activity in t he machine, and

as such the kernel must be eﬃcient enough to never be seen as a performance

constraint.

• Compatibility. While the basic operations of a kernel are of supreme interest

to researchers in the operating system area, most p eople do not want to know

what is going on as long as their programs work. As such, one of the most

important features of an operating system is the lack of surprises it o ﬀ ers t o

the user, b e he a normal end-user or a programmer. Even new features should

be oﬀered as a superset,ratherthaninstead of functionality that the user is

accustomed to.

These design issues, coupled with a very pragmatic approach to prog r amming,

has led to a system that shares features o f both the traditional monolithic kernel de-

sign a nd of the newer research projects into modern microkernels. The microkernel

design itself was discarded here due to doubts about the eﬃciency and simplicity of

the appro ach, but during the development many of the features usually associated

with microkernels have been implement ed on top of a more tradit ional monolithic

kernel.

The design ha s also been strongly inﬂuenced by the general availability of Linux

source code to anybody with access to the Internet. That has not only led to a very

dynamic development community that is physically spread all over the world, it has

also directly impacted the design itself.

Rather t han concentrate on a concept of a kernel binary that interfaces to the

rest of the world ( be it hardware or software), the Linux approachhasbeentohave

sources available that can be used to create the binary we want. This approach

allows the actual interfaces to be speciﬁed at compile t ime rather than at run-time.

The more tr aditional link-time and run-time interfa ces are natura lly also avail-

able, and give access to more dynamic feature sets. By using run-time dynamic

linking of modules into the kernel, the user can add and remove features as needed,

but the availability of sources always adds the possibility of increased performance

by specifying the conﬁguration at compile time and letting the compiler handle

interfacing issues.

2.1 The design — compatibili ty

The three main design issues – simplicity, eﬃciency and compatibility – have nat-

urally formed the basis for the kernel implementation. The compatibility issue

essentially deﬁnes the external shape o f the system while the issues of simplicity

and eﬃciency deﬁne the internal implementa t ion of it.

The wish to be compatible with other UNIX-type operating systems more or less

deﬁnes the kernel interface that is exported to system and user applications. Note

that compatibility extends to outside the machine itself: not only doesthecompat-

ibility issue require a compatible programming and user interface to the kernel, it

also involves the integration of the system with other external requirements. These

requirements include following standard protocols on external networks, but also

being able to live together on the same machine with other operating systems. This

can involve suppor ting a common disk partitioning scheme, or a particular boot-up

sequence.

As being compatible so clearly restricts the external interfaces of the system,

many new operating system projects choose to be less compatible in order to be

able to fully express the wishes of the designer. Instead of being constrained by

what others have done, such a project can soar to new heights of design beauty, at

least in the eyes of the designer.

Sadly, those projects invar iably tend to fail in real life, getting only a niche mar-

ket (if t hat) due to t heir lack of common applications or interfaces. As mentioned

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Linux操作系统的可移植性研究

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parallel mode only supports posix system

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嵌入式Linux应用编程常用的API

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