B.1. Where From Here?

I could easily have squeezed a few more chapters into this book. I could have added a chapter about creating new file systems, or about adding new protocol stacks (as if there's a need for that -- you'd have to dig underground to find a protocol stack not supported by Linux). I could have added explanations of the kernel mechanisms we haven't touched upon, such as bootstrapping or the disk interface.

However, I chose not to. My purpose in writing this book was to provide initiation into the mysteries of kernel module programming and to teach the common techniques for that purpose. For people seriously interested in kernel programming, I recommend Juan-Mariano de Goyeneche's list of kernel resources . Also, as Linus said, the best way to learn the kernel is to read the source code yourself.

If you're interested in more examples of short kernel modules, I recommend Phrack magazine. Even if you're not interested in security, and as a programmer you should be, the kernel modules there are good examples of what you can do inside the kernel, and they're short enough not to require too much effort to understand.

I hope I have helped you in your quest to become a better programmer, or at least to have fun through technology. And, if you do write useful kernel modules, I hope you publish them under the GPL, so I can use them too.

 

Index

Symbols

/etc/conf.modules, How Do Modules Get Into The Kernel? /etc/modules.conf, How Do Modules Get Into The Kernel? /proc filesystem, The /proc File System /proc/interrupts, Interrupt Handlers /proc/ksyms, Functions available to modules, Name Space, Common Pitfalls /proc/meminfo, The /proc File System /proc/modules, How Do Modules Get Into The Kernel?, The /proc File System 2.2 changes, Changes between 2.0 and 2.2 _IO, Talking to Device Files (writes and IOCTLs)} _IOR, Talking to Device Files (writes and IOCTLs)} _IOW, Talking to Device Files (writes and IOCTLs)} _IOWR, Talking to Device Files (writes and IOCTLs)} _NSIG_WORDS, Changes between 2.0 and 2.2 __exit, Hello World (part 3): The __init and __exit Macros __init, Hello World (part 3): The __init and __exit Macros __initdata, Hello World (part 3): The __init and __exit Macros __initfunction(), Hello World (part 3): The __init and __exit Macros __NO_VERSION__, Modules Spanning Multiple Files

A

asm

uaccess.h, Changes between 2.0 and 2.2

asm/uaccess.h, Changes between 2.0 and 2.2

B

BH_IMMEDIATE, Interrupt Handlers blocking processes, Blocking Processes blocking, how to avoid, Replacing printk bottom half, Interrupt Handlers busy, Replacing printk

C

carnivore

large, Common Pitfalls

cleanup_module(), Hello, World (part 1): The Simplest Module close, Changes between 2.0 and 2.2 code space, Code space coffee, Major and Minor Numbers CPU

multiple, Symmetrical Multi-Processing

crontab, Scheduling Tasks ctrl-c, Replacing printk current task, Replacing printk

D

DEFAULT_MESSAGE_LOGLEVEL, Introducing printk() defining ioctls, Talking to Device Files (writes and IOCTLs)} device file

character, Character Device Drivers

device files

input to, Talking to Device Files (writes and IOCTLs)}

write to, Talking to Device Files (writes and IOCTLs)}

E

EAGAIN, Replacing printk EINTR, Replacing printk elf_i386, Modules Spanning Multiple Files ENTRY(system call), System Calls entry.S, System Calls

F

file, The file structure filesystem

/proc, The /proc File System

registration, Using /proc For Input

filesystem registration, Using /proc For Input file_operations, The file_operations Structure file_operations structure, Using /proc For Input flush, Changes between 2.0 and 2.2

G

get_user, Using /proc For Input, Changes between 2.0 and 2.2

H

handlers

interrupt, Interrupt Handlers

housekeeping, Scheduling Tasks Hurd, Code space

I

inb, Keyboards on the Intel Architecture init_module(), Hello, World (part 1): The Simplest Module inode, The file structure, The /proc File System inode_operations structure, Using /proc For Input input

using /proc for, Using /proc For Input

insmod, Compiling Kernel Modules, System Calls Intel architecture

keyboard, Keyboards on the Intel Architecture

interrupt 0x80, System Calls interrupt handlers, Interrupt Handlers interruptible_sleep_on, Replacing printk interrupts, Changes between 2.0 and 2.2

disabling, Common Pitfalls

ioctl, Talking to Device Files (writes and IOCTLs)}

defining, Talking to Device Files (writes and IOCTLs)}

official assignment, Talking to Device Files (writes and IOCTLs)}

irqs, Changes between 2.0 and 2.2

K

kernel

versions, Changes between 2.0 and 2.2

kernel versions, Writing Modules for Multiple Kernel Versions kerneld, How Do Modules Get Into The Kernel? kernel/_version, Modules Spanning Multiple Files KERNEL_VERSION, Writing Modules for Multiple Kernel Versions keyboard, Keyboards on the Intel Architecture kmod, How Do Modules Get Into The Kernel?

L

ld, Modules Spanning Multiple Files libraries

standard, Common Pitfalls

library function, Functions available to modules LINUX_VERSION_CODE, Writing Modules for Multiple Kernel Versions

M

major number, Major and Minor Numbers

dynamic allocation, Registering A Device

mark_bh, Interrupt Handlers memory segments, Using /proc For Input microkernel, Code space minor number, Major and Minor Numbers mknod, Major and Minor Numbers modem, Talking to Device Files (writes and IOCTLs)} module

parameters, Changes between 2.0 and 2.2

module parameters, Changes between 2.0 and 2.2 module.h, Modules Spanning Multiple Files modules.conf

alias, How Do Modules Get Into The Kernel?

comment, How Do Modules Get Into The Kernel?

keep, How Do Modules Get Into The Kernel?

options, How Do Modules Get Into The Kernel?

path, How Do Modules Get Into The Kernel?

MODULE_AUTHOR(), Hello World (part 4): Licensing and Module Documentation module_cleanup, Scheduling Tasks MODULE_DESCRIPTION(), Hello World (part 4): Licensing and Module Documentation module_exit, Hello World (part 2) module_init, Hello World (part 2) module_interruptible_sleep_on, Replacing printk MODULE_LICENSE(), Hello World (part 4): Licensing and Module Documentation MODULE_PARM, Changes between 2.0 and 2.2 module_permissions, Using /proc For Input module_sleep_on, Replacing printk, Scheduling Tasks MODULE_SUPPORTED_DEVICE(), Hello World (part 4): Licensing and Module Documentation module_wake_up, Replacing printk MOD_DEC_USE_COUNT, Unregistering A Device MOD_INC_USE_COUNT, Unregistering A Device, System Calls MOD_IN_USE, Unregistering A Device monolithic kernel, Code space multi-processing, Symmetrical Multi-Processing multi-tasking, Replacing printk multitasking, Replacing printk

N

namespace pollution, Name Space Neutrino, Code space non-blocking, Replacing printk

O

official ioctl assignment, Talking to Device Files (writes and IOCTLs)} O_NONBLOCK, Replacing printk

P

permission, Using /proc For Input pointer

current, Using /proc For Input

printk

replacing, Replacing printk

printk(), Introducing printk() proc

using for input, Using /proc For Input

proc file

ksyms, Common Pitfalls

processes

blocking, Blocking Processes

killing, Replacing printk

waking up, Replacing printk

processing

multi, Symmetrical Multi-Processing

proc_dir_entry, Using /proc For Input proc_register, The /proc File System, Changes between 2.0 and 2.2 proc_register_dynamic, The /proc File System, Changes between 2.0 and 2.2 putting processes to sleep, Replacing printk put_user, Using /proc For Input, Changes between 2.0 and 2.2

Q

queue_task, Scheduling Tasks, Interrupt Handlers, Changes between 2.0 and 2.2 queue_task_irq, Interrupt Handlers, Changes between 2.0 and 2.2

R

read, Changes between 2.0 and 2.2

in the kernel, Using /proc For Input

reference count, Scheduling Tasks refund policy, Common Pitfalls register_chrdev, Registering A Device request_irq(), Interrupt Handlers rmmod, System Calls, Scheduling Tasks

preventing, Unregistering A Device

S

SA_INTERRUPT, Interrupt Handlers SA_SHIRQ, Interrupt Handlers scheduler, Replacing printk scheduling tasks, Scheduling Tasks segment

memory, Using /proc For Input

serial port, Talking to Device Files (writes and IOCTLs)} shutdown, System Calls SIGINT, Replacing printk signal, Replacing printk signals, Changes between 2.0 and 2.2 sleep

putting processes to, Replacing printk

sleep_on, Replacing printk, Scheduling Tasks SMP, Symmetrical Multi-Processing, Changes between 2.0 and 2.2 source file

chardev.c, Talking to Device Files (writes and IOCTLs)}

chardev.h, Talking to Device Files (writes and IOCTLs)}

hello-1.c, Hello, World (part 1): The Simplest Module

hello-2.c, Hello World (part 2)

hello-3.c, Hello World (part 3): The __init and __exit Macros

hello-4.c, Hello World (part 4): Licensing and Module Documentation

hello-5.c, Passing Command Line Arguments to a Module

intrpt.c, Keyboards on the Intel Architecture

ioctl.c, Talking to Device Files (writes and IOCTLs)}

print_string.c, Replacing printk

procfs.c, System Calls

sched.c, Scheduling Tasks

sleep.c, Replacing printk

start.c, Modules Spanning Multiple Files

stop.c, Modules Spanning Multiple Files

source files

multiple, Modules Spanning Multiple Files

ssize_t, Changes between 2.0 and 2.2 standard libraries, Common Pitfalls strace, Functions available to modules, System Calls struct

tty, Replacing printk

struct file_operations, Using /proc For Input struct inode_operations, Using /proc For Input structure

file_operations, Changes between 2.0 and 2.2

symbol table, Name Space symmetrical multi-processing, Symmetrical Multi-Processing, Changes between 2.0 and 2.2 sync, System Calls system call, Functions available to modules, System Calls

open, System Calls

system calls, System Calls sys_call_table, System Calls sys_open, System Calls

T

task, Scheduling Tasks

current, Replacing printk

tasks

scheduling, Scheduling Tasks

TASK_INTERRUPTIBLE, Replacing printk tq_immediate, Interrupt Handlers tq_struct, Scheduling Tasks tq_timer, Scheduling Tasks tty_structure, Replacing printk

V

version.h, Modules Spanning Multiple Files

W

waking up processes, Replacing printk write, Changes between 2.0 and 2.2

in the kernel, Using /proc For Input