kernel development in linux

8/14/2019 Kernel Development in LINUX

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KernelKernelDevelopment inDevelopment in

LINUXLINUXPrepared by: Utkarsh ThakkarPrepared by: Utkarsh Thakkar

Guided by: Prof. JitendraGuided by: Prof. JitendraBhatiaBhatia


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ContextContext

KernelKernel DefinitionDefinition

TypesTypes

ArchitectureArchitecture

RequirementsRequirements

ModulesModules

LinuxLinux FeaturesFeatures

AdvantagesAdvantages


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Defination of KernelDefination of Kernel

Kernel is a set of interrelated Modules by whichKernel is a set of interrelated Modules by which

the the operating system can handle all thethe the operating system can handle all the

resources of the system hardware.resources of the system hardware.

The kernel is a program that constitutes theThe kernel is a program that constitutes thecentral core of a computer operating system. Itcentral core of a computer operating system. It

has complete control over everything thathas complete control over everything that

occurs in the system.occurs in the system.

The kernel code is written in C with someThe kernel code is written in C with somemodules as assembly codes.modules as assembly codes.


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How to get the KernelHow to get the Kernel

Code??Code?? We can download the kernel source from theWe can download the kernel source from the

command line, using the wget or curl utilities,command line, using the wget or curl utilities,

both of which should come with your Linuxboth of which should come with your Linux

distribution.distribution.To download the 2.6.17.8 kernel versionTo download the 2.6.17.8 kernel version

using wget, enter:using wget, enter:

$ wget$ wget

http://www.kernel.org/pub/linux/kernel/v2.6/lihttp://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.17.8.tar.gznux-2.6.17.8.tar.gz


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Types of KernelTypes of Kernel

Monolithic KernelMonolithic Kernel

Micro KernelMicro Kernel

Exo KernelExo Kernel Hybrid KernelHybrid Kernel


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Monolithic KernelMonolithic Kernel

Monolithic kernels are part of Unix-Monolithic kernels are part of Unix-

like operating systems like Linuxlike operating systems like Linux

,FreeBSD etc.,FreeBSD etc.

These types of kernels consist of theThese types of kernels consist of the

core functions of the operatingcore functions of the operating

system and the device drivers withsystem and the device drivers with

the ability to load modules atthe ability to load modules atruntime.runtime.


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Micro KernelMicro Kernel

These types of kernels normallyThese types of kernels normally

provide only the minimal servicesprovide only the minimal services

such as defining memory addresssuch as defining memory address

spaces, Inter-process communicationspaces, Inter-process communication(IPC) and the process management.(IPC) and the process management.

The other functions such as runningThe other functions such as running

the hardware processes are notthe hardware processes are nothandled directly by microkernels.handled directly by microkernels.


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Exo KernelExo Kernel

Exokernels are evolving and still underExokernels are evolving and still under

experimental stage in development of anexperimental stage in development of an

operating system that could incorporateoperating system that could incorporate

multiple library operating systems and aremultiple library operating systems and areintended to simultaneously run multipleintended to simultaneously run multiple

operating systems of different kinds like Linuxoperating systems of different kinds like Linux

and Microsoft Windows together usingand Microsoft Windows together using

appropriate Application Programmingappropriate Application ProgrammingInterface (API).Interface (API).


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Traditional Unix KernelTraditional Unix Kernel

Hardware

Hardware control

Kernel levelHardware level

Device drivers

Character Block

Buffer cache

File subsystem

Process control

subsystem

IPC

scheduler

Memory

management

System call interface

LibrariesUser programs

Kernel levelUser level


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Tools to Build the KernelTools to Build the Kernel

Only three packages that are neededOnly three packages that are needed

in order to successfully build a kernelin order to successfully build a kernel A CompilerA Compiler

A LinkerA Linker

A Make utilityA Make utility

Module-init-toolsModule-init-tools


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CompilerCompiler

The Linux kernel is written in the C programmingThe Linux kernel is written in the C programming

language, with a small amount of assemblylanguage, with a small amount of assembly

language in some places. To build the kernel, thelanguage in some places. To build the kernel, the

gcc C compiler must be used.gcc C compiler must be used.

To determine which version of gcc you have onTo determine which version of gcc you have on

your system, run the following command:your system, run the following command:

$ gcc --version$ gcc --version


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LinkerLinker

The C compiler, gcc, does not do all of the compiling onThe C compiler, gcc, does not do all of the compiling on

its own. It needs an additional set of tools known asits own. It needs an additional set of tools known as

binutils to do the linking and assembling of source files.binutils to do the linking and assembling of source files.

The binutils package also contains useful utilities thatThe binutils package also contains useful utilities that

can manipulate object files in lots of useful ways, suchcan manipulate object files in lots of useful ways, suchas to view the contents of a library.as to view the contents of a library.

To determine which version of binutils you have on yourTo determine which version of binutils you have on your

system, run the following command:system, run the following command:

$ ld v$ ld v


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Make UtilityMake Utility

Make is a tool that walks the kernelMake is a tool that walks the kernel

source tree to determine which filessource tree to determine which files

need to be compiled, and then callsneed to be compiled, and then calls

the compiler and other build tools tothe compiler and other build tools todo the work in building the kernel.do the work in building the kernel.


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Module-init-toolsModule-init-tools

The module-init-tools package is neededThe module-init-tools package is needed

if you wish to use Linuxif you wish to use Linux kernel moduleskernel modules..

To determine which version of theTo determine which version of the

module-init-tools package you have onmodule-init-tools package you have onyour system, run the followingyour system, run the following

command:command:

$ depmod -V$ depmod -V
http://c/Documents%20and%20Settings/UTKARSH/Desktop/final%20touch/Kernel%20description.txthttp://c/Documents%20and%20Settings/UTKARSH/Desktop/final%20touch/Kernel%20description.txthttp://c/Documents%20and%20Settings/UTKARSH/Desktop/final%20touch/Kernel%20description.txt


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Metadata In KernelsMetadata In Kernels

All kernels can and should contain metadatadescriptiveAll kernels can and should contain metadatadescriptive

information about the basic kernel data.information about the basic kernel data.

Metadata might convey:Metadata might convey:

when, where, how and by whom the file was madewhen, where, how and by whom the file was made

for what purpose the file was madefor what purpose the file was made what source data were used to make the filewhat source data were used to make the file

key characteristics of the file, such as:key characteristics of the file, such as:

start and stop timesstart and stop times

information about data gapsinformation about data gaps notes on expected data accuracynotes on expected data accuracy

cautions on use of the filecautions on use of the file

whatever else the file creator thinks could be usefulwhatever else the file creator thinks could be useful

to consumers of the data productto consumers of the data product


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Booting of KernelBooting of Kernel

Initially the Kernel image is loadedInitially the Kernel image is loaded

into the primary memory, which is ainto the primary memory, which is a

secured one for the kernel.secured one for the kernel.

Then the Kernel creates a limitedThen the Kernel creates a limited

address space including the kernel'saddress space including the kernel's

code and data segment, the initialcode and data segment, the initial

Page Tables, and a 128KB for somePage Tables, and a 128KB for somedynamic data structures.dynamic data structures.


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Examples of KernelExamples of Kernel

ModulesModules SchedulerScheduler

SupervisorSupervisor

Interrupt HandlerInterrupt Handler

Memory MangerMemory Manger


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Examples of KernelExamples of Kernel

Modules(2)Modules(2) SchedulerScheduler : Which is concerned with the Time of: Which is concerned with the Time of

kernel provided to the processes.kernel provided to the processes.

SupervisorSupervisor : Which grants the Use of Kernel to: Which grants the Use of Kernel toeach process.each process.

Interrupt HandlerInterrupt Handler: Handles all the mask able: Handles all the mask ableand non mask able interrupts like io request,and non mask able interrupts like io request,exception etc.exception etc.

Memory ManagerMemory Manager: Handles the memory: Handles the memory

allocation to the file and maintains the uarea.allocation to the file and maintains the uarea.


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History of LinuxHistory of Linux

Linux was created originally by and named after a youngstudent Linus Torvald at the University of Helsinki in Finland.

Linux began searching for ways to get more out of Minix inthe spring of 1991.

On october 5th 1991, Linus announced his first "official"version of Linux, version 0.02.

Three years later, in 1994, version 1.0 was officially released.

Some Basic Characteristics ofSome Bas c C aracter st cs o


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Some Basic Characteristics ofSome Bas c C aracter st cs oLinuxLinux

Multi-user System

Multiprogramming/Multitasking system

Uses Time Sharing

Access rights for Files and Processes

Uses File and Process hierarchies


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Advantages and DisadvantagesAdvantages and Disadvantages

AdvantagesAdvantages::

(a) Cost(a) Cost

The Linux OS is entirely cost- and license-free. The only expensesThe Linux OS is entirely cost- and license-free. The only expenses

involved are those of hardware and maintenance.involved are those of hardware and maintenance.

(b) OS Stability(b) OS Stability Linux almost never freezes under normal use.Linux almost never freezes under normal use.

Linux has been known to run some applications for months and yearsLinux has been known to run some applications for months and years

at a time.at a time.

(c) Speed(c) SpeedLinux machines are also known to be extremely fast, because theLinux machines are also known to be extremely fast, because the

operating system is very efficient at managing resources .operating system is very efficient at managing resources .


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AdvantagesAdvantages::

(d) Portability(d) Portability

Linux can run on ARMs, DEC Alphas, SUN Sparcs, M68000 machinesLinux can run on ARMs, DEC Alphas, SUN Sparcs, M68000 machines

(like Atari and Amiga), MIPS and PowerPCs, and others. So no matter(like Atari and Amiga), MIPS and PowerPCs, and others. So no matter

what computer you're running, Linux will work on your hardware.what computer you're running, Linux will work on your hardware.(e) Power and Customization(e) Power and Customization

Linux can be tailored to your specific hardware and software needs,Linux can be tailored to your specific hardware and software needs,

as well as other operating systems.as well as other operating systems.

(f) Support(f) SupportSupport for the Linux OS is entirely free. There is extensiveSupport for the Linux OS is entirely free. There is extensive

documentation covering almost everything you will use.documentation covering almost everything you will use.


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Disadvantages:Disadvantages:

(a) Lack of technical support(a) Lack of technical supportHaving no source of technical support for the linuxHaving no source of technical support for the linux

operating system, so for its application.operating system, so for its application.

(b) Hardware problems(b) Hardware problems

Linux can be hard to install and doesnt work on allLinux can be hard to install and doesnt work on allhardware platforms as it is not a commercialhardware platforms as it is not a commercial

program development operation.program development operation.


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Disadvantages:Disadvantages:

(c) Maintainance(c) MaintainanceLinux requires that you learn to perform administrationLinux requires that you learn to perform administration

tasks like adding new users and installing software.tasks like adding new users and installing software.

(d) Lack of experience(d) Lack of experienceIt has many features which require patience to learn, andIt has many features which require patience to learn, and

experience to fully understand.experience to fully understand.

(e) Accountability(e) Accountability

Use of the Linux OS is strictly at-your-own-risk. There is noUse of the Linux OS is strictly at-your-own-risk. There is no

one who is responsible if the OS fails.one who is responsible if the OS fails.


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ApplicationsApplications

Linux contains a wide variety of applications.Linux contains a wide variety of applications.

(a)General Business Applications - Office Suites, Financial(a)General Business Applications - Office Suites, Financial

Programs, Word Processors, Text Editors, SpreadsheetsPrograms, Word Processors, Text Editors, Spreadsheets

(b)Database Tools - Databases, Database Tools and Utilities(b)Database Tools - Databases, Database Tools and Utilities

(c) Development Tools - Programming Software, Tools, and(c) Development Tools - Programming Software, Tools, andUtilitiesUtilities


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ApplicationsApplications

(e(e)) Internet Utilities - HTML Editors, Internet ApplicationsInternet Utilities - HTML Editors, Internet Applications

and Utilities, Email ,Software, Web Browsers, Web Serversand Utilities, Email ,Software, Web Browsers, Web Servers

(f) Networking Tools -- Networking Tools and Utilities(f) Networking Tools -- Networking Tools and Utilities

(g) Miscellaneous Applications(g) Miscellaneous Applications

(h) Linux Software Map (LSM)(h) Linux Software Map (LSM)


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What Next?????????What Next?????????

Hybrid KernelHybrid Kernel

The Kernel with the extendedThe Kernel with the extended

functionalities added by the means offunctionalities added by the means of

the modules.the modules. Ex: Device DriversEx: Device Drivers


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ReferencesReferences

www.wikipedia.orgwww.wikipedia.org

http://it.toolbox.com/http://it.toolbox.com/

www.linuxforumes.orgwww.linuxforumes.org www.kernel.org.inwww.kernel.org.in
http://www.wikipedia.org/http://www.wikipedia.org/http://it.toolbox.com/http://it.toolbox.com/http://www.linuxforumes.org/http://www.linuxforumes.org/http://www.kernel.org.in/http://www.kernel.org.in/http://www.kernel.org.in/http://www.linuxforumes.org/http://it.toolbox.com/http://www.wikipedia.org/


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AnyAny

Questions???????Questions???????