Windows NT A Distributed Architecture Professor Mohamed Khalil CSE 8343 GROUP A5 Dhaval Sanghvi Amit Sharma Ali Abbas Video Tape 1 Agenda Features Design goals of Windows NT Architecture Three Layers Upper Layer Executive Middle Layer Kernel Lower Layer Hardware Abstraction Layer Environment Subsystem Summary Biblography 2 Features Preemptive Multitasking Support for Symmetric Multiprocessing Integrated Networking services Client Server Architecture Support for several file systems Virtual Memory Management Support for 2 GB linear space for application and also 2GB for OS 3 Design goals of Windows NT Extensibility Portability Reliability Compatibility Security Performance Scalability Localization 4 Windows NT Architecture Windows NT is a modular operating system composed of simple modules kernel mode and user mode Kernel Mode composed of mainly 3 layers Upper layer Executive layer Middle layer The kernel Lower layer Hardware Abstraction Layer HAL User Mode is composed of environment subsystems 5 Architecture cont d 6 Executive Layer Each component of NT Executive provides a set of API s Some API s are designed to be invoked by user mode processes Some API s are visible only in the kernel mode inside the Executive NT s API s are flexible enough to implement a wide range of operating system environments NT s Executive has six subsystems Object Manager Process Manager Virtual Memory Manager Security Reference Monitor Local Procedure Call Facility I O subsystem 7 Object Manager An object is a representation of a conceptual or physical entity in the system Examples of Objects Files Directories Processes Threads Synchronization Objects semaphores mutexes events timers Virtual Memory objects Mostly everything passed around and processed within NT is represented as an object 8 Security Reference Monitor Checks for proper authorization before granting access to objects Object Manager is a customer of a SRM it asks SRM if a process has the proper rights to execute a certain type of action on an object Implements auditing functions to keep track of attempts to access an object Implements high level security Resource owners must be able to control who has access to it Unique user name and password identification Audit trail of successful and unsuccessful attempts Protection from unauthorized tampering of files 9 Process Manager Creates deletes and modifies processes and threads Does not dispatch or schedules any work This is done by the kernel A process is represented within NT by a process object Process Object process virtual address space resources visible to the process process threads NT does not maintain parent child information between related processes 10 Virtual Memory Manager VMM Implements a fetch policy when the pager brings a page from disk to memory Uses a demand paging algorithm with the locality of reference clustering Implements shared memory segments used by LPC to transfer large messages Certain parts of the VMM are processor dependent e g page table entries page size virtual address translation Manages file system drivers device drivers and network drivers 11 VMM cont d Drivers can be dynamically loaded unloaded started and stopped without rebooting the system Multiple installable file systems including MSDOS FAT File Allocation Table High Performance File System HPFS the CDROM file system and the NT File System NTFS 12 I O Manager Mapped file I O capabilities for image activation file caching and application use Packet driven I O system Every I O request is represented by an IRP I O Request Packet that moves from one I O system component to the other Manages buffers for I O requests Provides time out support for drivers Records which installable components are loaded in the system 13 I O Manager cont d NTFS extends MS DOS FAT with HPFS with Quick recovery of disk data after system failure Ability to handle very large files 17 billion GB Security features e g execute only files Support for POSIX OS environments Features for future extensibility e g transactionbased operations to enhance fault tolerance usercontrolled file version numbers flexible options for file naming and file attributes 14 Kernel Layer Schedules threads to run Handles hardware interrupts and dispatches them to appropriate drivers and threads Handles software and hardware generated exceptions e g writing to non existing memory position memory parity errors Graceful system shutdown and restoration after power failure Provides an API to the executive to kernel managed objects e g events mutexes semaphores and timers 15 Hardware Abstraction Layer Isolates the kernel from hardware variations Exports an API to upper layers to handle hardware dependent issues such as Processor initialization support for SMP computers Instruction cache and data cache Device driver support e g bus addressing interrupt control DMA functions Timing and interrupt functions Firmware interface functions Low level error handling 16 Environment subsystem User mode process that provides services to applications These services emulate the behavior of a specific OS Converts requests made by an application to requests that NT s kernel mode component understand Implemented using Client Server model Application Client Environment subsystem Server 17 Win32 Subsystem Implements the Win32 API Each Win32 application runs on its own address space separate from Win32 subsystems address space Manages all the keyboard and mouse input and all screen output for entire system acts as a server to the other environment subsystems 18 Win32 Subsystem cont d 19 OS 2 Subsystem Supports OS 2 up to 1 3 character mode applications Each OS 2 application runs on its own separate address space and separate from the OS 2 subsystem s address space POSIX Subsystem Supports POSIX character mode applications Each POSIX application runs on its own separate address space and separate from POSIX subsystem s address space 20 MS DOS Environment Associates each DOS application with Virtual DOS Machines VDM Each DOS applications runs on its own address space A VDM provides the DOS application with Execution of Intel x86 instructions Simulated DOS INT 21 services Simulated DOS BIOS interrupt services Simulated standard PC hardware devices 21 MS DOS Environment Cont d 22 Windows 16 Bit Environment All Win16 applications are supported by a single VDM called WOW Win16 on Win32 WOW is like a virtual windows machine The WOW runs on an address space separate from all other user