Download OS Structures

Chapter 2:
Operating System Structures
Joe McCarthy
CSS 430: Operating Systems - OS Structures
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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
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Comfort, Growth & Panic Zones
http://www.alljapaneseallthetime.com/blog/comfort-zone-growth-zone-panic-zone
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
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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
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Chapter 2: OS Structures
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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
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A View of Operating System Services
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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)
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Example of System Calls
• System call sequence to copy the contents of
one file to another file
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Example of System Calls
• System call sequence to copy the contents of
one file to another file
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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
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API – System Call – OS Relationship
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Standard C Library Example
• printf() C library call  write() system call
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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
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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?
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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
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Parameter Passing via Table
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Types of System Calls
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Process control
File management
Device management
Status Information
Communications
Protection
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Process Control
Process: a program loaded in memory and able to execute
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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
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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]
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fork()
int main( ) {
int fd[2];
int pid;
pid = fork()
Process id
of child (>0)
if ( pipe( fd ) < 0 ) {
perror( "pipe error" );
exit( EXIT_FAILURE );
}
if ( ( pid = fork() ) < 0 ) {
perror ( "fork error" );
exit( EXIT_FAILURE );
}
…
0
parent
fd[0]
fd[1]
pid
…
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fd[0]
fd[1]
pid
…
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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" );
exit( EXIT_FAILURE );
}
…
http://vip.cs.utsa.edu/classes/cs3733s2009/notes/USP-06.html
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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" );
exit( EXIT_FAILURE );
}
…
http://vip.cs.utsa.edu/classes/cs3733s2009/notes/USP-06.html
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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
close( fd[0] );
dup2( fd[1], 1 );
close( fd[1] );
execlp( "ps", "ps", "-A",
NULL );
}
…
http://vip.cs.utsa.edu/classes/cs3733s2009/notes/USP-06.html
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fork() + execlp()
(pipedup2a.cpp)
int main( ) {
int fd[2];
int pid;
parent
if ( pipe( fd ) < 0 ) {
… }
if ( ( pid = fork() ) < 0 ) {
… }
if ( pid > 0 ) { // parent
close( fd[1] );
dup2( fd[0], 0 );
close( fd[0] );
… }
else { // child
close( fd[0] );
fd[0]
dup2( fd[1], 1 );
fd[1]
pid
close( fd[1] );
…
execlp( "ps", "ps", "-A",
NULL );
}
…
child
fd[0]
fd[1]
pid
…
pipedup2a
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ps -A
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Resource Management
• File Management
[joemcc@uw1-320-18 ThreadOS]$ ls -l
-rw------- 1 css430 users 10193 Nov
-rw------- 1 css430 users 8603 Dec
-rw-r--r-- 1 css430 users 8395 Nov
-rw------- 1 css430 users 8817 Nov
Kernel*.java
11 2004 Kernel_fil.java
23 2010 Kernel_hw3part1.java
13 2004 Kernel.java
11 2004 Kernel_org.java
• Device Management
[joemcc@uw1-320-18 ThreadOS]$ stat Kernel.java
File: `Kernel.java'
Size: 8395
Blocks: 24
IO Block: 32768 regular file
Device: 17h/23d Inode: 130884
Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1803/ css430)
Gid: ( 100/
users)
Access: 2011-11-12 19:40:45.000000000 -0800
Modify: 2004-11-13 20:36:20.000000000 -0800
Change: 2011-10-17 14:00:43.000000000 -0700
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Resource Management
• File Management
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Create file, delete file
Open, close
Read, write, reposition file pointer
Get file attributes, set file attributes
• Device Management
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Request device, release device
Read, write, reposition read/write head
Get device attributes, set device attributes
Logically attach (mount) or detach (unmount) devices
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Maintaining info / connections
• Information Maintenance
• Communication
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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
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Windows & Unix System Calls
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MS-DOS execution
(a) At system startup (b) running a program
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FreeBSD Running Multiple Programs
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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
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Simple Structure
• MS-DOS
– Goal: most functionality
in the least space
– Not divided into modules
– Interfaces & levels of
functionality not well
separated
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Layered Approach
• Modularity:
– Each layer (level)
uses functions & services only
from layer(s) directly below
– Provides functions & services
only to layer(s) directly above
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Layered Approach to Networking
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Traditional UNIX System Structure
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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
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Microkernel System Structure
• Moves as much from the kernel into “user” space
• Communication takes place between user modules
using message passing
• Benefits:
• Detriments:
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Microkernel System Structure
• Moves as much from the kernel into “user” space
• Communication takes place between user modules
using message passing
• Benefits:
–
–
–
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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
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Mac OS X Structure
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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
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Solaris Modular Approach
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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.
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Virtual Machines
(a) Nonvirtual machine (b) virtual machine
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Solaris 10 with Two Containers
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VMware Architecture
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Java
• Java consists of:
1. Programming language specification
2. Application programming interface (API)
3. Virtual machine specification
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The Java Development Kit
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Cloud Computing
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http://news.cnet.com/8301-13953_3-9917409-80.html
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Amazon Web Services
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The Cost of Convenience
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For next time
• Readings
– Chapters 3: Processes
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