Unreliable Guide To Hacking The Linux Kernel

Paul Rusty Russell

rusty@rustcorp.com.au

Copyright © 2000 by Paul Russell

This is the first release of this document as part of the kernel tarball.

Table of Contents

Introduction

The Players

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

Some Basic Rules

ioctls: Not writing a new system call

Recipes for Deadlock

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

Wait Queues include/linux/wait.h

Declaring
Queuing
Waking Up Queued Tasks

Atomic Operations

EXPORT_SYMBOL() include/linux/module.h
EXPORT_SYMTAB

Routines and Conventions

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

Putting Your Stuff in the Kernel

Kernel Cantrips

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