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Linux内核编程(结论)

著者:Ori Pomerantz
翻译:徐辉


其他
Goods and Services
I hope nobody minds the shameless promotions here. They are all things which are likely to be of use to beginning Linux Kernel Module programmers.
Getting this Book in Print
The Coriolis group is going to print this book sometimes in the summer of 99. If this is already summer, and you want this book in print, you can go easy on your printer and buy it in a nice, bound form.
GNU GENERAL PUBLIC LICENSE
Printed below is the GNU General Public License (the GPL or copyleft), under which this book is licensed.
Version 2, June 1991
Copyright ©1989, 1991 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
PREAMBLE
The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software-to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundations software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.
We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.
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GNU GENERAL PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0.
This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The ``Program, below, refers to any such program or work, and a ``work based on the Program means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term ``modification.) Each licensee is addressed as ``you.
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You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.
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You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
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You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
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If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)
These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.
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In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.
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You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
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c.
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NO WARRANTY
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BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
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END OF TERMS AND CONDITIONS
APPENDIX: HOW TO APPLY THESE TERMS TO YOUR NEW PROGRAMS
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the ``copyright line and a pointer to where the full notice is found.
one line to give the programs name and a brief idea of what it does. Copyright ©19yy name of author
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

The hypothetical commands show w and show c should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than show w and show c; they could even be mouse-clicks or menu items-whatever suits your program.
You should also get your employer (if you work as a programmer) or your school, if any, to sign a ``copyright disclaimer for the program, if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program Gnomovision (which makes passes at compilers) written by James Hacker.
signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.



1.1我没有以root身份编译是因为用root做的事情越少,系统就越安全。我是做计算机安全工作的,所以比较偏执。
3.1这是在2.0版本中。在2.2中如果把索引节点设为0这是自动完成的。
4.1这两个的区别是文件操作是处理文件本身,而索引节点操作时处理引用文件的方法,比如创建连接。
5.1注意这里读和写角色再次换位,在ioctl中读是向内核发信息,而写是从内核读信息。
5.2 这是不确切的。比如你不能通过ioctl传递一个结构体,但是可以传递指向它的指针。
6.1 不可能有。因为在C语言中目标文件只有全局变量的地址,而不是类型。这就是为什么头文件是必要的。
8.1 最简单的把文件保持打开状态的方法是用tail –f打开。
8.2 这是说进程仍在内核——对于进程来说,它发出open系统调用,而这个系统调用还没有返回。多数情况下,在发出系统调用和返回之间的时间内,进程不知道别人在使用CPU。
8.3 这是因为我们使用了module_interruptible_sleep_on。我们可以使用module_sleep_on,但是会激怒那些控制程序被打扰的用户。
9.1 Teletype,最初是用来和Unix系统通信的键盘-打印机的结合体,现在成了Unix程序的文本流的概括,无论是物理终端、X显示的一个xterm、网络连接还是其他。
10.1 它们其实是一样的。
11.1 这是Linux发源的Intel结构上的标准方法。
11.2 queue_task_irq是用一个全局锁来保护不受此影响,在2.2中没有queue_task_irq,而queue_task是被锁保护的。
12.1 例外是线连进程,可以同时在几个CPU上运行。
12.2 表示可以在SMP中可以安全使用。