Linux内核模块编程指南：自由开源与实践

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《Linux内核模块编程指南》是一本由Peter Jay Salzman、Michael Burian和Ori Pomerantz合著的免费电子书，版权属于2001年Salzman，直至2007年5月18日的版本2.6.4。该书遵循开放软件许可协议（Open Software License, OSL）第1.1版，允许用户在遵守相应条款下自由复制、修改或分发。作者鼓励将此书广泛传播，无论是个人还是商业用途，只要保持完整的版权声明，并且遵循OSL的规定。本书旨在提供对Linux内核模块编程的深入理解和实用指导。它覆盖了从内核模块的基本概念、设计原则到实际开发过程中的关键步骤，包括模块加载、初始化、函数定义、数据结构处理、内存管理以及与内核交互的方法。书中还强调了版权和授权的重要性，确保衍生作品和翻译作品也需遵循相同的开放许可制度，保持原始版权通知不被修改。对于想深入Linux内核编程领域的读者来说，这本指南提供了宝贵的参考资料，帮助他们理解如何编写高效、稳定的内核模块以扩展和优化系统的功能。无论你是系统管理员、开发者还是研究者，都能从中受益匪浅，了解如何遵循开放源码的精神，参与到Linux生态系统的贡献中去。学习本书，读者可以期待掌握以下核心知识点： 1. 内核模块基础：模块的生命周期、加载机制、内核与用户空间通信接口。 2. 编程实践：C语言编程技巧，包括数据结构和函数组织。 3. 模块初始化与清理：了解如何正确处理模块启动和关闭时的资源管理。 4. 错误处理与调试：掌握处理错误和异常的策略，以及如何使用调试工具。 5. 安全与权限：内核模块的安全注意事项，以及访问权限控制。 6. 驱动程序设计：模块如何与硬件设备进行交互，实现设备驱动功能。《Linux内核模块编程指南》不仅是一本技术手册，也是开源精神的体现，对于Linux内核开发者社区具有深远影响。通过阅读和实践这本书中的内容，读者能够提升自己的技能，为Linux世界的繁荣做出贡献。

printk(KERN_INFO "Hello, world 4\n");

return 0;

}

static void __exit cleanup_hello_4(void)

{

printk(KERN_INFO "Goodbye, world 4\n");

}

module_init(init_hello_4);

module_exit(cleanup_hello_4);

* You can use strings, like this:

* Get rid of taint message by declaring code as GPL.

MODULE_LICENSE("GPL");

* Or with defines, like this:

MODULE_AUTHOR(DRIVER_AUTHOR); /* Who wrote this module? */

MODULE_DESCRIPTION(DRIVER_DESC); /* What does this module do */

* This module uses /dev/testdevice. The MODULE_SUPPORTED_DEVICE macro might

* be used in the future to help automatic configuration of modules, but is

* currently unused other than for documentation purposes.

MODULE_SUPPORTED_DEVICE("testdevice");

2.6. Passing Command Line Arguments to a Module

Modules can take command line arguments, but not with the argc/argv you might be used to.

To allow arguments to be passed to your module, declare the variables that will take the values of the

command line arguments as global and then use the module_param() macro, (defined in

linux/moduleparam.h) to set the mechanism up. At runtime, insmod will fill the variables with any

command line arguments that are given, like ./insmod mymodule.ko myvariable=5. The variable

declarations and macros should be placed at the beginning of the module for clarity. The example code should

clear up my admittedly lousy explanation.

The module_param() macro takes 3 arguments: the name of the variable, its type and permissions for the

corresponding file in sysfs. Integer types can be signed as usual or unsigned. If you'd like to use arrays of

integers or strings see module_param_array() and module_param_string().

int myint = 3;

module_param(myint, int, 0);

Arrays are supported too, but things are a bit different now than they were in the 2.4. days. To keep track of

the number of parameters you need to pass a pointer to a count variable as third parameter. At your option,

you could also ignore the count and pass NULL instead. We show both possibilities here:

The Linux Kernel Module Programming Guide

Chapter 2. Hello World 11

int myintarray[2];

module_param_array(myintarray, int, NULL, 0); /* not interested in count */

int myshortarray[4];

int count;

module_parm_array(myshortarray, short, , 0); /* put count into "count" variable */

A good use for this is to have the module variable's default values set, like an port or IO address. If the

variables contain the default values, then perform autodetection (explained elsewhere). Otherwise, keep the

current value. This will be made clear later on.

Lastly, there's a macro function, MODULE_PARM_DESC(), that is used to document arguments that the

module can take. It takes two parameters: a variable name and a free form string describing that variable.

Example 2−7. hello−5.c

* hello−5.c − Demonstrates command line argument passing to a module.

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/stat.h>

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Peter Jay Salzman");

static short int myshort = 1;

static int myint = 420;

static long int mylong = 9999;

static char *mystring = "blah";

static int myintArray[2] = { −1, −1 };

static int arr_argc = 0;

* module_param(foo, int, 0000)

* The first param is the parameters name

* The second param is it's data type

* The final argument is the permissions bits,

* for exposing parameters in sysfs (if non−zero) at a later stage.

module_param(myshort, short, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);

MODULE_PARM_DESC(myshort, "A short integer");

module_param(myint, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

MODULE_PARM_DESC(myint, "An integer");

module_param(mylong, long, S_IRUSR);

MODULE_PARM_DESC(mylong, "A long integer");

module_param(mystring, charp, 0000);

MODULE_PARM_DESC(mystring, "A character string");

* module_param_array(name, type, num, perm);

* The first param is the parameter's (in this case the array's) name

* The second param is the data type of the elements of the array

* The third argument is a pointer to the variable that will store the number

* of elements of the array initialized by the user at module loading time

* The fourth argument is the permission bits

The Linux Kernel Module Programming Guide

Chapter 2. Hello World 12

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Linux内核模块编程指南：自由开源与实践

Linux内核模块编程指南

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