OS3 - Principles Of

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Principles of

Operating Systems

Operating System Structures

Saiful Anwar

State Polytechnic of Jakarta

January, 2007


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Computer System Structures

Computer System Operation

IO Structure

Storage Structure

Storage !ierarchy

!ar"ware Protection

#eneral System Architecture


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Computer System Architecture


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Computer System Organi$ation

IO "e%ices an" the CP& e'ecute concurrently(

)ach "e%ice controller is in charge of a particular

"e%ice type

)ach "e%ice controller has a local *uffer( IO is from the"e%ice to local *uffer of controller

CP& mo%es "ata fromto main memory tofrom

the local *uffers

+e%ice controller interrupts CP& on completion

of IO


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Interrupts

Interrupt transfers control to the interrupt ser%ice

routineInterrupt Ser%ice outine- Segments of co"e that

"etermine action to *e taken for each type of interrupt(

Interrupt %ector contains the a""ress of ser%ice routines(

OS preser%es the state of the CP&stores registers an" the program counter .a""ress of

interrupte" instruction/(

Trapsoftware generate" interrupt cause" either *y an error

or a user reuest(


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Interrupt !an"ling

1ypes of interruptPolling

ectore" interrupt system

Incoming interrupts are "isa*le" while another

interrupt is *eing processe" to pre%ent a lost

interrupt(


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IO Structure

Synchronous IOwaitinstruction i"les CP& until ne't interrupt

no simultaneous IO processing, at most one outstan"ing

IO reuest at a time(

Asynchronous IOAfter IO is initiate", control returns to user program without

waiting for IO completion(

System call

+e%ice Status ta*le 3 hol"s type, a""ress an" state foreach "e%ice

OS in"e'es into IO "e%ice ta*le to "etermine "e%ice status

an" mo"ify ta*le entry to inclu"e interrupt(


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+irect 4emory Access .+4A/

&se" for high spee" IO

"e%ices a*le to transmit

information at close to

memory spee"s(

+e%ice controller transfers*locks of "ata from *uffer

storage "irectly to main

memory without CP&

inter%ention(

Only one interrupt is

generate" per *lock, rather

than one per *yte .or wor"/(

MemoryMemory

CPUCPU I/O devicesI/O devicesI/O instructions


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Storage Structure

4ain memory 3 only large storage me"ia that the

CP& can access "irectly(

Secon"ary storage 3 e'tension of main memory

that has large non%olatile storage capacity(4agnetic "isks 3 rigi" metal or glass platters co%ere"

with magnetic recor"ing material(

+isk surface is logically "i%i"e" into tracks,

su*"i%i"e" into sectors(+isk controller "etermines logical interaction

*etween "e%ice an" computer(


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Storage !ierarchy

Storage systems are organi$e" in a hierarchy

*ase" onSpee"

Costolatility

Caching 3 process of copying information into

faster storage system5 main memory can *e

%iewe" as fast cache for secon"ary storage(


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Storage +e%ice !ierarchy


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!ar"ware Protection

+ual 4o"e Operation

IO Protection

4emory Protection

CP& Protection


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+ual3mo"e operation

Sharing system resources reuires operating

system to ensure that an incorrect program

cannot cause other programs to e'ecute

incorrectly(

Pro%i"e har"ware support to "ifferentiate

*etween at least two mo"es of operation-

6( &ser mo"e 33 e'ecution "one on *ehalf of a user(

2( 4onitor mo"e .super%isorkernelsystem mo"e/ 33

e'ecution "one on *ehalf of operating system(


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+ual3mo"e operation.cont(/

4o"e *it a""e" tocomputer har"ware toin"icate the currentmo"e- monitor.0/ oruser.6/(

hen an interrupt orfault occurs, har"wareswitches to monitormo"e(

Pri%ilege" instructionsonly in monitor mo"e(

User

Monitor

Set

user

mode

Interrupt/

fault


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IO Protection

All IO instructions are pri%ilege"

instructions(

4ust ensure that a user program coul"

ne%er gain control of the computer in

monitor mo"e, for e(g( a user program that

as part of its e'ecution, stores a new

a""ress in the interrupt %ector(


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4emory Protection

4ust pro%i"e memoryprotection at least for theinterrupt %ector an" theinterrupt ser%ice routines(

1o pro%i"e memoryprotection, a"" two registersthat "etermine the range oflegal a""resses a programmay a""ress( 8ase egister 3 hol"s smallest

legal physical memory a""ress( 9imit register 3 contains the si$e

of the range(

4emory outsi"e the "efine"range is protecte"(

0

256000

300000

20!0

""0000

#02000

30000

#20!00

$ase re%ister

&imit re%ister

monitor

'o(#

'o( 2

'o(

'o( 3

0


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!ar"ware A""ress Protection


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Protection !ar"ware .cont(/

hen e'ecuting in monitor mo"e, the OS has

unrestricte" access to *oth monitor an" users:

memory(

1he loa" instructions for the basean" limit

registers are pri%ilege" instructions(


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CP& Protection

1imer 3 interrupts computer after specifie"

perio" to ensure that OS maintains control(1imer is "ecremente" e%ery clock tick(

hen timer reaches a %alue of 0, an interrupt occurs(1imer is commonly use" to implement time

sharing(

1imer is also use" to compute the current time(

9oa" timer is a pri%ilege" instruction(


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#eneral System Architecture

#i%en the IO instructions are pri%ilege", how "o

users perform IO;

ia system calls 3 the metho" use" *y a processto reuest action *y the operating system(


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Operating System Structures

Operating System ComponentsProcess 4anagement, 4emory 4anagement,

Secon"ary Storage 4anagement, IO System

4anagement,


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Process 4anagement .Chapters >37/

Process 3 fun"amental concept in OSProcess is a program in e'ecution(

Process nee"s resources 3 CP& time, memory, files"ata

an" IO "e%ices(

OS is responsi*le for the following process

management acti%ities(Process creation an" "eletion

Process suspension an" resumptionProcess synchroni$ation an" interprocess communication

Process interactions 3 "ea"lock "etection, a%oi"ance an"

correction


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4emory 4anagement .Chapters ?3@/

4ain 4emory is an array of a""ressa*le wor"s or

*ytes that is uickly accessi*le(

4ain 4emory is %olatile(

OS is responsi*le for-Allocate an" "eallocate memory to processes(

4anaging multiple processes within memory 3 keep

track of which parts of memory are use" *y which

processes( 4anage the sharing of memory *etweenprocesses(

+etermining which processes to loa" when memory

*ecomes a%aila*le(


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Secon"ary Storage an" IO

4anagement .Chapter 60/

Since primary storage is e'pensi%e an" %olatile,

secon"ary storage is reuire" for *ackup(

+isk is the primary form of secon"ary storage(

OS performs storage allocation, free3spacemanagement an" "isk sche"uling(

IO system in the OS consists of8uffer caching an" management

+e%ice "ri%er interface that a*stracts "e%ice "etails

+ri%ers for specific har"ware "e%ices


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Protection an" Security .Chapter 6>/

Protection mechanisms control access of programs

an" processes to user an" system resources(

Protect user from himself, user from other users, system

from users(

Protection mechanisms must-

+istinguish *etween authori$e" an" unauthori$e" use(

Specify access controls to *e impose" on use(

Pro%i"e mechanisms for enforcement of access control(

Security mechanisms pro%i"e trust in system an"

pri%acy

authentication, certification, encryption etc(


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=etworking .+istri*ute" Systems/

+istri*ute" System is a collection of processors

that "o not share memory or a clock(

Processors are connecte" %ia a communication

network(A"%antages-Allows users an" system to e'change information

pro%i"e computational spee"up

increase" relia*ility an" a%aila*ility of information


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Comman" Interpreter System

Comman"s that are gi%en to the operating

system %ia comman" statements that e'ecuteProcess creation an" "eletion, IO han"ling, Secon"ary

Storage 4anagement, 4ain 4emory 4anagement,


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Operating System Ser%ices

Ser%ices that pro%i"e user3interfaces to OSProgram e'ecution 3 loa" program into memory an" run it

IO Operations 3 since users cannot e'ecute IO operations

"irectly


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System Calls

Interface *etween running program an" the OS(Assem*ly language instructions .macros an"

su*routines/

Some higher le%el languages allow system calls to *ema"e "irectly .e(g( C/

Passing parameters *etween a running program

an" OS %ia registers, memory ta*les or stack(

&ni' has a*out 2 system callsrea"./, write./, open./, close./, fork./, e'ec./, ioctl./,D((


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System Programs

Con%enient en%ironment for program "e%elopment an"

e'ecution( &ser %iew of OS is "efine" *y system

programs, not system calls(

Comman" Interpreter .sh, csh, ksh/ 3 parsese'ecutes othersystem programs


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System +esign an" Implementation

)sta*lish "esign goals&ser #oals

System #oals

Software )ngineering 3Separate mechanism from policy( Policies "etermine

what nee"s to *e "one, mechanisms "etermine how

they are "one(

Choose a high3le%el implementation languagefaster implementation, more compact, easier to "e*ug


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System #eneration

OS written for a class of machines, must *e

configure" for each specific site(SES#)= program o*tains info a*out specific har"ware

configuration an" creates %ersion of OS for har"ware8ooting

8ootstrap program 3 loa"er program loa"s

kernel, kernel loa"s rest of OS(

8ootstrap program store" in O4


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OS Structure 3 Simple Approach

4S3+OS 3 pro%i"es a lot of functionality in little

space(=ot "i%i"e" into mo"ules, Interfaces an" le%els of

functionality are not well separate"&=I 3 limite" structuring, has 2 separa*le partsSystems programs

Fernel

e%erything *elow system call interface an" a*o%ephysical har"ware(


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&=I System Structure


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9ayere" OS Structure

OS "i%i"e" into num*er of

layers 3 *ottom layer is

har"ware, highest layer is

the user interface(

)ach layer uses functions

an" ser%ices of only lower3

le%el layers(

1!) Operating System

Fernel has successi%e

layers of a*straction(


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irtual 4achines

9ogically treats har"warean" OS kernel ashar"ware

Pro%i"es interfacei"entical to un"erlying*are har"ware(

Creates illusion ofmultiple processes 3 eachwith its own processoran" %irtual memory

)ard*are

+irtual mac)ine

,ernel ,ernel ,ernel

processes

processes

processes


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Summary of OS Structures

Operating System Concepts

Operating System Ser%ices, System Programs

an" System calls

Operating System +esign an" Implementation

Structuring Operating Systems


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1he en" of this presentation

1hank you for yours attentionD

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OS3 - Principles Of