CS 149: Operating Systems May 7 Class Meeting Department of Computer Science San Jose State...

CS 149: Operating SystemsMay 7 Class Meeting

Department of Computer ScienceSan Jose State University

Spring 2015Instructor: Ron Mak

www.cs.sjsu.edu/~mak

http://www.cs.sjsu.edu/~mak

2Computer Science Dept.Spring 2015: May 7

CS 149: Operating Systems© R. Mak

Unofficial Field Trip

Computer History Museum in Mt. View http://www.computerhistory.org/

Saturday, May 9, 11:30 – closing time

Special free admission. Do a self-guided tour of the new Revolution exhibit. See a life-size working model of Charles Babbage’s

Difference Engine in operation, a hand-cranked mechanical computer designed in the early 1800s.

Experience a fully restored IBM 1401 mainframe computer from the early 1960s in operation. General info: http://en.wikipedia.org/wiki/IBM_1401 My summer seminar: http://www.cs.sjsu.edu/~mak/1401/ Restoration:

http://ed-thelen.org/1401Project/1401RestorationPage.html

Extra creditfun quiz!

http://www.computerhistory.org/

http://en.wikipedia.org/wiki/IBM_1401

http://www.cs.sjsu.edu/~mak/1401/

http://ed-thelen.org/1401Project/1401RestorationPage.html



Four Eras of Microsoft Operating Systems

1. MS-DOS Windows 1.0, 2.0

2. MS-DOS-based Windows Windows 3.0, 3.1, 98, ME

3. NT-based Windows Windows XP, Vista, 7

4. Modern Windows Windows 8, 8.1



Modern Windows

Microsoft transformed itself from a PC software company to a devices and services company.

Needed an OS that it could deploy across phones tablets game consoles laptops desktops servers cloud



MinWin Approach

A small OS core that can be extended into different devices.

Extend the core to be the operating systems for specific devices. New user interfaces and features Common experience for users

Support new Intel architectures. Support the ARM architecture.



Modern Windows Programming Layers

Modern Operating Systems, 4th ed.Andrew Tanenbaum and Herbert BosPearson, 2014ISBN: 978-0133591620



Programming Windows

Windows 8.1 removed POSIX compliance.

Modern Software Development Kit Includes the new WinRT set of APIs.

Shift programmers away from a threading model to a task model. Separate resource management (priorities, CPUs)

from the programming model (concurrent activities).

Modern applications run in an AppContainer sandbox for security.



Components to Build NT Subsystems

The NT kernel contains general-purpose facilities for writing OS-specific subsystems.




Kernel-Mode Objects

The NTOS executive layer running in kernel mode implements system calls.

Native NT system calls operate on kernel-mode objects:




Native NT API

Native NT API calls use handles to manipulate objects across process boundaries. Examples:




Win32 API

Library procedures that either Do the work in user mode. Wrap native NT calls that do the work:




Windows-on-Windows (WOW)

WOW32 Used on 32-bit x86 systems. Run 16-bit Windows 3.x applications. Map system calls and parameters between

the 16-bit and 32-bit worlds.

WOW64 Allows 32-bit applications to run on x64 systems.



Windows vs. Unix

Unix Simple OS functions Few parameters Few examples of multiple ways to do something. Kernel panic for a fatal error.

Windows Comprehensive APIs with many parameters. Several ways to do the same thing. Mixed low-level and high-level functions. Blue Screen of Death for a fatal error.



Windows Registry

Registry: A special file system to maintain system configuration information.

Hive: A volume of the registry.

HKLM = HKEY LOCAL MACHINE Modern Operating Systems, 4th ed.Andrew Tanenbaum and Herbert BosPearson, 2014ISBN: 978-0133591620



Kernel-Mode Organization

ISR = Interrupt Service RoutineDPC = Deferred Procedure CallAPC = Asynchronous Procedure CallLPC = Local Procedure Call Modern Operating Systems, 4th ed.

Andrew Tanenbaum and Herbert BosPearson, 2014ISBN: 978-0133591620



Dispatcher Objects

Control dispatching and synchronization: events mutexes semaphores threads timers




Executive Layer

Object manager Manages most kernel-mode objects Processes, threads, files, semaphores, I/O devices

and drivers, timers, etc.

I/O manager Framework for implementing I/O device drivers. Executive services to configure, access, and perform

operations on devices. Plug-and-play



Executive Layer, cont’d

Process manager Create and terminate processes and threads

Memory manager Demand-paged virtual memory Physical page frames Disk pagefile backing store

Cache manager Optimizes I/O performance



Executive Layer, cont’d

Security reference monitor Enforces Windows security mechanisms Supports Common Criteria

U.S. Department of Defense Orange Book requirements

Configuration manager Implements the registry

Advanced local procedure call (ALPC) Highly efficient interprocess communication



Hardware Abstraction Layer (HAL)

Hide machine dependencies.




Device Stacks

IRP = I/O request packet




Object Management

Most important function of the executive.




Object Handles

Handles refer to kernel-mode objects. A handle table translates handles to objects.




Handle Table

A handle table can have up to 16 million handles.




Object Procedures

Supplied when specifying a new object type.




Object Namespace Directories




Creating and Opening a File




Creating and Opening a File, cont’d

1. Executive component passes Unicode pathname for namespace.

2. Object manager searches through directories and symbolic links.

3. Object manager calls the Parse procedure for object type.

4. I/O manager creates IRP, allocate file object, send request to stack of I/O devices.

5. IRP passed down the I/O stack until it reaches device object representing the file system instance.



Creating and Opening a File, cont’d

6. Device objects encountered as the IRP heads toward the file system represent file system filter drivers.

7. File system device object has a link to file system driver object.

8. NTFS fills in file object and returns it to I/O manager, which returns back up through all devices on the stack.

9. Object manager is finished with its namespace lookup.

10. Final step is to return back to the user-mode caller.



Common Executive Object Types




Processes and Threads

Processes can optionally be grouped into jobs.

A thread can schedule multiple fibers. A fiber assumes the identity of the thread that runs it. Lower overhead of switching among threads.




Processes and Threads, cont’d




Processes and Threads, cont’d




Thread Priorities




Thread Priorities, cont’d




Memory Management

Virtual address space layout




Memory Management System Calls




Page Fault Categories

The page referenced is not committed. committed = the page is mapped to a virtual page

Attempted access to a page that is in violation of the permissions.

A shared copy-on-write page was about to be modified.

The stack needs to grow.

The page referenced is committed but not currently mapped in.

These first two are dueto programming errors.

LRU page replacementalgorithm.



I/O API Calls




Device Driver Stacking

Stack device drivers to work with a specific instance of a device.




File System

A volume is the fundamental structure of the Windows 8.1 file system (NTFS).

Created by the Windows 8.1 disk administrator utility.

Based on a logical disk partition. May occupy a portions of a disk, an entire disk,

or span across several disks.

All metadata, such as information about the volume, is stored in a regular file.



NTFS Clusters

A cluster is the underlying unit of disk allocation.

A cluster is a number of disk sectors that is a power of 2.

Because the cluster size is smaller than for the 16-bit FAT file system, the amount of internal fragmentation is reduced.



File System Logging

All file system data structure updates are performed inside transactions that are logged.

Before a data structure is altered, the transaction writes a log record that contains redo and undo information.

After the data structure has been changed, a commit record is written to the log to signify that the transaction succeeded.



File System Recovery

After a crash, the file system data structures can be restored to a consistent state by processing the log records.

This scheme does not guarantee that all the user file data can be recovered after a crash.

It only guarantees that the file system data structures (the metadata files) are undamaged and reflect someconsistent state prior to the crash.



Security

Secure login with anti-spoofing measures

Discretionary access controls

Privileged access controls

Address space protection per process

New pages must be zeroed before being mapped in

Security auditing



Security, cont’d

Each user and group identified by an SID (security ID).

Each process has an access token containing: a SID a DACL (default access control list) other properties

DACL


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