Unix Internals-Lec1

7/24/2019 Unix Internals-Lec1

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UNIX Internals

Rohit Jnagal

[email protected]


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Introduction

First Steps


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0perating System 3efresher

+hy an 0perating System:

you dont want to know what goes into making pepperoni

Process 4 3esources (memory5 dis-5 cpu5 net/or-!

0perating System 6oals:

7 Create 3esource A,stractions

7 Create Process A,stractions

7 8anage 3esource Sharing

7 Process &solation

7 0thers 9


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0perating System 3efresher

Computer System Components:

ard/are

7 pro*ides ,asic computing resources (CP$5 8emory5 &0!

0perating System7 controls and coordinates the use of hard/are among *arious

application programs for *arious users;

Application Programs (Processes!

7 /ays in /hich system used to sol*e pro,lems of a user (compilers5

data,ase systems5 *ideo games and ma-ing tea! $sers

7 (people5 machines5 other computers!


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0perating Systems 3efresher

+hy learn 0perating Systems:


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0perating System istory

0perating Systems through the ages:

=ar- Ages ( >?@ 7 !

acuum


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0perating Systems through the ages: >st6eneration (>? 7 !

Mainframe Systems

7 Batching similar Do,s

7 0ne Do, at a time7 Automatic Do, sequencing

7 3esident 8onitor

&nitiate control in monitor

Control transfer to a Do,

+hen Do, completes5 transfer ,ac- tomonitor

7 Se*ere &0 ,ottlenec-


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0perating Systems through the ages: 2nd6eneration ( >? 7 E !

Integrated ICs Renaissance

7 8ulti.programmed Batch Systems

7 %otion of computer architecture

7 =is- dri*es

7 0n.line terminals

7 Se*eral Do,s in memory at the same

time7 0S features

Go, scheduling

8emory management ( 0*erlays!

CP$ scheduling

Protection


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2nd6eneration (>? 7 E !


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A )ong


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Hrd6eneration (>?E . !

)S&s5 )S&s5 %ano K mobile an ant can use

Architecture Ad*ances:

7 Smaller5 faster 8icroprocessors

7 Caches

7 )arger Faster Storage

7 0ffloading CP$ /or-

8odern 0S feature7 6$&

7 8ultimedia

7 &nternet 4 +e,

7 %et/or-ed5 =istri,uted5 etc


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Current $%&' Systems:

P P.$'

P ( =igital (Compaq! !


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0perating System Classifications

8ulti.user Single user 8ultiprogramming

8ulti.threaded

7 $ser threads thread li,raries

7 SystemLernel threads

8onolithic Lernel 8icro.-ernels

Functional Classification

7 8ainframe

7 Ser*er

7 =es-top


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$%&' 0perating System

$%&' Structure

hardwareProc/threadmgmt

File systems

applications

MP

daemons

Misc...

cmds

shells

Memory

Mgmt

IPCdrivers

LVM

I/ O


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$%&' features

Files andProcesses

File system has places ( *s C:5 =: !

Processes ha*e life

"*erything is a file

Processing en*ironment ard/are mode support

&nterrupts and "#ceptions

Processor "#ecution )e*els

Process 8anagement Su,system 8emory 8anagement Su,system

LernelSystem &nterfaces

So5 /hatJs different in a %on.$%&' system 9


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Processor 8odes

Super*isor or $ser 8ode

Super*isor 8ode

Can e#ecute all instructions

Can reference all memory locations

Lernel e#ecute in this mode

$ser 8ode

Can e#ecute su,set of instructions

Can reference a su,set of memory locations


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System ierarchies

Hardware Level

LibrariesUser program

Systemcall interfacelightweight system calls

MemoryManagementSubsystem

device drivers

LVM

User Level

Kernel Level

Hardware control

Process ManagementSubsystem

Scheduling

IP

!u"er ache

Phys #ileSystem

Virtual #ile System

I$ %


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Primary Su,systems

Process 8anagement

8anages all acti*e processes and threads8emory 8anagement

Allocates memory for processes at run.time

Performs translations of physical memory locations to *irtual memorylocations

File Su,system

irtual File System )ayer

7 A,stracts and manages data for different file system types

Physical File System )ayer

7 8anages access for specific file systems of *arious types&0 Su,system

8anages system &0 resources5 dri*ers5 and data structures

=ri*es system configuration process


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&s my system $%&' or $%&' compliant 9

A


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P.$' istory

P$' release istory

e/lett Pac-ard $%&'

P$' >; in >?EH

P$' >; (>??! : ,ased on S3@ $%&' standard

P$' >>; (>??M! : First @.,it *ersion

P$' >>;>>(2>! .N >>i series (+orld +ar > Armistice! P$' >>;2 (22!: First &tanium release

P$' >>;2H >>i *2 (2H!: supports ,oth PA and &tanium5

supports cc%$8A


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P.$' Specials

P.$' features

First to use access control lists for file access permissionsFirst $%&' system /ith ,uilt in olume 8anager

"nhanced 3elia,ility5 security and partitioning

Clustering technology

Cell Based5 cc%$8A architecture support

irtual Ser*er "n*ironment (S"!

Scaling

>2E processors (e#panda,le to 2!

>


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Learning

check


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Computer Architecture 3efresher

Components: CP$

7 &nstruction Set Architecture 3&SC s C&SC

x86 CISC -> RISC +micro-ops

&AH25 &A@5 PA.3&SC5 Po/erPC5 A38

"P&C: &tanium

7 Pipelining Fetch5 =ecode5 "#ecute

Superpipelined5 Superscalar

7 3egisters 6eneral Purpose 3egisters

Program Counters

Program Status +ord (PS+!

8emory 4 8emory ierarchy

7 Caches

7 3A8

7 =is-s

7


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0S and Architecture : 8utual &nteraction

7 0S functionality limited ,y Architecture features

8ultiprogramming on EE

7 0S structure can ,e simplified /ith Architecture support &nterrupt5 =8A5 etc

7 8ost proprietary 0S are de*eloped for a particular architecture

PA.3&SC 5 &PF

#E

SPA3C


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Architecture support for 0S:

&nterrupt and "#ceptions7 o/ does the -ernel notice an &0 has finished

Polling

ard/are &nterrupt

7 &nterrupts

6enerated ,y ard/are =e*ices

Asynchronous

7 "#ceptions

6enerated ,y e#ecuting instructions

Synchronous


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&0 0perations7 =ata


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0S Protection7 o/ does the processor -no/ if a protected instruction should ,e

e#ecuted9

3ings or 8odes of 0peration

Access 3ights

Crossing Protection Boundaries

$ser process call Lernel to do something pri*ileged

0S defined sequence of System Calls

8odes5 Conte#ts and S/itches

8emory Protection

Protect user programs from each other

Protect itself from user programs 8emory 8anagement $nit

Segmentation

Virtual Memory

Page table, Page protection, !"s

"ase an# !imit Registers


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SynchroniOation7 Pro,lems

&nterrupt may occur at any time and may interfere /ith interrupted code

SynchroniOation of Concurrent Processes

8ulti.processor synchroniOation

7 Solutions


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Learning

check


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System Calls

8ethods to request system action on ,ehalf of a user

3equest

System Action 0n ,ehalf of a user

A Single program ma-es numerous system calls;

Program: 3ead from one file and /rite to another


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System Calls

Passing Parameters


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System Calls


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8a-ing a System Call

Gust use the stu,

&nternally5

7 Stu, pushes the syscall num,er on stac-registeru.area

7Arguments go on stac-registersu.area

7A special trap instruction is called

Changes e#ecution mode to -ernel


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Learning

check


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