Unreliable Guide To Hacking The Linux Kernel

Paul Rusty Russell

rusty@rustcorp.com.au

Copyright © 2000 by Paul Russell

Table of Contents

1. Introduction

2. The Players

User Context
Hardware Interrupts (Hard IRQs)
Software Interrupt Context: Bottom Halves, Tasklets, softirqs

3. Some Basic Rules

4. ioctls: Not writing a new system call

5. Recipes for Deadlock

6. Common Routines

printk() include/linux/kernel.h
copy_[to/from]_user() / get_user() / put_user() include/asm/uaccess.h
kmalloc()/kfree() include/linux/slab.h
current include/asm/current.h
udelay()/mdelay() include/asm/delay.h include/linux/delay.h
local_irq_save()/local_irq_restore() include/asm/system.h
local_bh_disable()/local_bh_enable() include/asm/softirq.h
smp_processor_id()/cpu_[number/logical]_map() include/asm/smp.h
__init/__exit/__initdata include/linux/init.h
__initcall()/module_init() include/linux/init.h
module_exit() include/linux/init.h
MOD_INC_USE_COUNT/MOD_DEC_USE_COUNT include/linux/module.h

7. Wait Queues include/linux/wait.h

Declaring
Queuing
Waking Up Queued Tasks

8. Atomic Operations

EXPORT_SYMBOL() include/linux/module.h
EXPORT_SYMTAB

10. Routines and Conventions

Double-linked lists include/linux/list.h
Return Conventions
Breaking Compilation
Initializing structure members
GNU Extensions
C++
#if

11. Putting Your Stuff in the Kernel

12. Kernel Cantrips

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		Introduction