1. Chapter 2: Operating System Structures
Joe McCarthy
CSS 430: Operating Systems - OS Structures

2. CSS 430: Operating Systems - OS Structures
Outline
Announcements / updates
Gayle Laakman McDowell, Th, 10/11, 4:30pm, UW2-005
GUIs / IDEs for remotely accessing uw1-320-lab
Catalyst GoPost guidelines
Questions on Programming Assignment 1?
Sample programs
Using fork(), pipe(), dup2(), close(), execlp()
Chapter 2: Operating Systems Structures
Including more on fork(), pipe(), dup2(), close(), execlp()
Live programming experiments (time permitting)
Next time
Chapter 3: Processes
CSS 430: Operating Systems - OS Structures

3. Comfort, Growth & Panic Zones
Goal: stretch as much as possible from your comfort zone into your growth zone while avoiding your panic zone
TMI / too much help [on forum]  comfort zone
CSS 430: Operating Systems - OS Structures

4. CSS 430: Operating Systems - OS Structures
Sample Programs
C++ programs using fork(), pipe(), dup2()
~css430/examples/processmgmt on uw1-320-lab
Recommendation:
Decompose problem into small[er] chunks
Experiment with small changes (compile, test, debug)
testpipe[0-2].cpp
Send “hello” through pipe to STDOUT
Differences:
hardcoded string vs. argv[1], write() vs execlp()
pipedup2[a-f].cpp
Using system calls to do ‘ps –A | tr a-z A-Z’
Differences
Parent vs. child calling ps vs. tr
Using read() & write() vs. execlp() for tr
CSS 430: Operating Systems - OS Structures

5. Chapter 2: OS Structures
Operating System Services
User Operating System Interface
System Calls
Types of System Calls
System Programs
Operating System Design and Implementation
Operating System Structure
Virtual Machines
Operating System Debugging
Operating System Generation
System Boot
Material derived, in part, from Operating Systems Concepts with Java, 8th Ed. © 2009 Silberschatz, Galvin & Gagne
CSS 430: Operating Systems - OS Structures

6. A View of Operating System Services
CSS 430: Operating Systems - OS Structures

7. CSS 430: Operating Systems - OS Structures
System Calls
Programming interface to the services provided by the OS
Typically written in a high-level language (C or C++)
Mostly accessed by programs via a high-level Application Program Interface (API) rather than direct system call use
Three common APIs are
Win32 API for Windows
POSIX API for POSIX-based systems UNIX, Linux, Mac OS X)
Java API for the Java virtual machine (JVM)
Why use APIs rather than system calls?
(Note that the system-call names used throughout this text are generic)
CSS 430: Operating Systems - OS Structures

8. Example of System Calls
System call sequence to copy the contents of one file to another file
CSS 430: Operating Systems - OS Structures

9. Example of System Calls
System call sequence to copy the contents of one file to another file
CSS 430: Operating Systems - OS Structures

10. Example of Standard API
Consider the ReadFile() function in the Win32 API—a function for reading from a file
A description of the parameters passed to ReadFile()
HANDLE file—the file to be read
LPVOID buffer—a buffer where the data will be read into and written from
DWORD bytesToRead—the number of bytes to be read into the buffer
LPDWORD bytesRead—the number of bytes read during the last read
LPOVERLAPPED ovl—indicates if overlapped I/O is being used
CSS 430: Operating Systems - OS Structures

11. API – System Call – OS Relationship
CSS 430: Operating Systems - OS Structures

12. Standard C Library Example
printf() C library call  write() system call
CSS 430: Operating Systems - OS Structures

13. System Call Parameter Passing
Often, more information is required than simply the name of the desired system call
Exact type & amount of information vary according to OS & call
Three general methods used to pass parameters to the OS
CSS 430: Operating Systems - OS Structures

14. System Call Parameter Passing
Often, more information is required than simply the name of the desired system call
Exact type & amount of information vary according to OS & call
3 general methods used to pass parameters to the OS
Simplest: pass the parameters in registers
Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register
This approach taken by Linux and Solaris
Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system
Advantages / disadvantages?
CSS 430: Operating Systems - OS Structures

15. System Call Parameter Passing
Often, more information is required than simply the name of the desired system call
Exact type & amount of information vary according to OS & call
3 general methods used to pass parameters to the OS
Simplest: pass the parameters in registers
Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register
This approach taken by Linux and Solaris
Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system
Advantages / disadvantages
Block and stack methods do not limit the number or length of parameters being passed
CSS 430: Operating Systems - OS Structures

16. Parameter Passing via Table
CSS 430: Operating Systems - OS Structures

17. CSS 430: Operating Systems - OS Structures
Types of System Calls
Process control
File management
Device management
Status Information
Communications
Protection
CSS 430: Operating Systems - OS Structures

18. CSS 430: Operating Systems - OS Structures
Process Control
Process: a program loaded in memory and able to execute
CSS 430: Operating Systems - OS Structures

19. CSS 430: Operating Systems - OS Structures
Process Control
Process: a program loaded in memory and able to execute
OS Operations:
Create/terminate process
Get/set process attributes
Wait for time, event, signal
Allocate/free memory
CSS 430: Operating Systems - OS Structures

20. CSS 430: Operating Systems - OS Structures
Process Control
Process: a program loaded in memory and able to execute
Process states
Memory
File Descriptor Table
Registers
OS Operations:
Create/terminate process
Get/set process attributes
Wait for time, event, signal
Allocate/free memory
[Preview of Chapter 3]
CSS 430: Operating Systems - OS Structures

21. CSS 430: Operating Systems - OS Structures
fork()
int main( ) {
int fd[2];
int pid;
if ( pipe( fd ) < 0 ) {
perror( "pipe error" );
exit( EXIT_FAILURE ); }
if ( ( pid = fork() ) < 0 ) {
perror ( "fork error" ); …
pid = fork()
Process id of child (>0)
parent
child
fd[0]
fd[1] pid …
fd[0]
fd[1] pid …
CSS 430: Operating Systems - OS Structures

22. CSS 430: Operating Systems - OS Structures
pipe()
int main( ) {
int fd[2];
int pid;
if ( pipe( fd ) < 0 ) {
perror( "pipe error" );
exit( EXIT_FAILURE ); }
if ( ( pid = fork() ) < 0 ) {
perror ( "fork error" ); …
CSS 430: Operating Systems - OS Structures

23. CSS 430: Operating Systems - OS Structures
pipe() + fork()
int main( ) {
int fd[2];
int pid;
if ( pipe( fd ) < 0 ) {
perror( "pipe error" );
exit( EXIT_FAILURE ); }
if ( ( pid = fork() ) < 0 ) {
perror ( "fork error" ); …
CSS 430: Operating Systems - OS Structures

24. CSS 430: Operating Systems - OS Structures
close() + dup2()
int main( ) {
int fd[2];
int pid;
if ( pipe( fd ) < 0 ) {
… }
if ( ( pid = fork() ) < 0 ) { …} …
if ( pid > 0 ) { // parent
close( fd[1] );
dup2( fd[0], 0 );
close( fd[0] );
else { // child
dup2( fd[1], 1 );
execlp( "ps", "ps", "-A",
NULL ); }
CSS 430: Operating Systems - OS Structures

25. CSS 430: Operating Systems - OS Structures
fork() + execlp()
(pipedup2a.cpp)
int main( ) {
int fd[2];
int pid;
if ( pipe( fd ) < 0 ) {
… }
if ( ( pid = fork() ) < 0 ) {
if ( pid > 0 ) { // parent
close( fd[1] );
dup2( fd[0], 0 );
close( fd[0] );
else { // child
dup2( fd[1], 1 );
execlp( "ps", "ps", "-A",
NULL ); } …
parent
child
fd[0]
fd[1] pid …
fd[0]
fd[1] pid …
pipedup2a
ps -A
CSS 430: Operating Systems - OS Structures

26. CSS 430: Operating Systems - OS Structures
Resource Management
File Management
Device Management
ThreadOS]$ ls -l Kernel*.java
-rw css430 users Nov Kernel_fil.java
-rw css430 users Dec Kernel_hw3part1.java
-rw-r--r-- 1 css430 users Nov Kernel.java
-rw css430 users Nov Kernel_org.java
ThreadOS]$ stat Kernel.java
File: `Kernel.java'
Size: Blocks: IO Block: regular file
Device: 17h/23d Inode: Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1803/ css430) Gid: ( 100/ users)
Access: :40:
Modify: :36:
Change: :00:
CSS 430: Operating Systems - OS Structures

27. CSS 430: Operating Systems - OS Structures
Resource Management
File Management
Create file, delete file
Open, close
Read, write, reposition file pointer
Get file attributes, set file attributes
Device Management
Request device, release device
Read, write, reposition read/write head
Get device attributes, set device attributes
Logically attach (mount) or detach (unmount) devices
CSS 430: Operating Systems - OS Structures

28. Maintaining info / connections
Information Maintenance
Communication
CSS 430: Operating Systems - OS Structures

29. Maintaining info / connections
Information Maintenance
Get/set time or date
Get/set system data
Get/set process, file or device attributes
Communication
Create/delete communication connection
Send/receive messages
Maintain communication status information
CSS 430: Operating Systems - OS Structures

30. Windows & Unix System Calls
CSS 430: Operating Systems - OS Structures

31. CSS 430: Operating Systems - OS Structures
MS-DOS execution
(a) At system startup (b) running a program
CSS 430: Operating Systems - OS Structures

32. FreeBSD Running Multiple Programs
CSS 430: Operating Systems - OS Structures

33. OS Design & Implementation
Important distinction:
Policy: What will be done?
Mechanism: How to do it?
Benefits:
Maximum flexibility
Policy changes need not entail mechanism changes & vice versa
CSS 430: Operating Systems - OS Structures

34. CSS 430: Operating Systems - OS Structures
Simple Structure
MS-DOS
Goal: most functionality in the least space
Not divided into modules
Interfaces & levels of functionality not well separated
CSS 430: Operating Systems - OS Structures

35. CSS 430: Operating Systems - OS Structures
Layered Approach
Modularity:
Each layer (level) uses functions & services only from layer(s) directly below
Provides functions & services only to layer(s) directly above
CSS 430: Operating Systems - OS Structures

36. Layered Approach to Networking
CSS 430: Operating Systems - OS Structures

37. Traditional UNIX System Structure
CSS 430: Operating Systems - OS Structures

38. CSS 430: Operating Systems - OS Structures
UNIX
Two components
Systems programs
ls, rm, cp, mv, ps, grep, wc, …
The kernel
Everything below the system-call interface and above the physical hardware
Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level
CSS 430: Operating Systems - OS Structures

39. Microkernel System Structure
Moves as much from the kernel into “user” space
Communication takes place between user modules using message passing
Benefits:
Detriments:
CSS 430: Operating Systems - OS Structures

40. Microkernel System Structure
Moves as much from the kernel into “user” space
Communication takes place between user modules using message passing
Benefits:
Easier to extend a microkernel
Easier to port the operating system to new architectures
More reliable (less code is running in kernel mode)
More secure
Detriments:
Performance overhead of user space to kernel space communication
CSS 430: Operating Systems - OS Structures

41. CSS 430: Operating Systems - OS Structures
Mac OS X Structure
CSS 430: Operating Systems - OS Structures

42. CSS 430: Operating Systems - OS Structures
Modules
Most modern operating systems implement kernel modules
Uses object-oriented approach
Each core component is separate
Each talks to the others over known interfaces
Each is loadable as needed within the kernel
Overall, similar to layers but with more flexible
CSS 430: Operating Systems - OS Structures

43. Solaris Modular Approach
CSS 430: Operating Systems - OS Structures

44. CSS 430: Operating Systems - OS Structures
Virtual Machines
A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware.
A virtual machine provides an interface identical to the underlying bare hardware.
The operating system host creates the illusion that a process has its own processor and (virtual memory).
Each guest is provided with a (virtual) copy of underlying computer.
CSS 430: Operating Systems - OS Structures

45. CSS 430: Operating Systems - OS Structures
Virtual Machines
(a) Nonvirtual machine (b) virtual machine
CSS 430: Operating Systems - OS Structures

46. Solaris 10 with Two Containers
CSS 430: Operating Systems - OS Structures

47. CSS 430: Operating Systems - OS Structures
VMware Architecture
CSS 430: Operating Systems - OS Structures

48. CSS 430: Operating Systems - OS Structures
Java
Java consists of:
Programming language specification
Application programming interface (API)
Virtual machine specification
CSS 430: Operating Systems - OS Structures

49. The Java Development Kit
CSS 430: Operating Systems - OS Structures

50. CSS 430: Operating Systems - OS Structures
Cloud Computing
CSS 430: Operating Systems - OS Structures

51. CSS 430: Operating Systems - OS Structures
CSS 430: Operating Systems - OS Structures

52. CSS 430: Operating Systems - OS Structures
Amazon Web Services
CSS 430: Operating Systems - OS Structures

53. CSS 430: Operating Systems - OS Structures

54. CSS 430: Operating Systems - OS Structures

55. The Cost of Convenience
CSS 430: Operating Systems - OS Structures

56. CSS 430: Operating Systems - OS Structures
For next time
Readings
Chapters 3: Processes
CSS 430: Operating Systems - OS Structures