Device Objects and Device Stacks describes device objects and device stacks. The section includes information about physical device objects (PDOs), functional device objects (FDOs), and filter device objects (filter DOs). Drivers are often built from a set of device objects that work together. This set of device objects is called a stack. Stacks can help you understand the flow of information to and from a driver and how different parts of the driver communicate internally.
A device driver is a set of software code that must integrate into the operating system. To complete this integration, you must write a set of handler routines in your driver that process calls from the operating system. These routines can be simple function calls, but many of them implement the processing of I/O request packets (IRPs), which facilitate communication between drivers and the operating system.
Windows Nt Device Driver Development Pdfrar
Note WDM drivers can also use the Windows Driver Frameworks (WDF) library to make some parts of a device driver easier to write. Specifically, kernel-mode drivers can use the Kernel-Mode Driver Framework (KMDF), which is part of WDF. For more information about KMDF for kernel-mode drivers, see Kernel-Mode Driver Framework Overview. Note that KMDF does not replace WDM. You must still understand many parts of WDM to write a KMDF driver.
Windows updates released August 10, 2021 and later will, by default, require administrative privilege to install drivers. We made this change in default behavior to address the risk in all Windows devices, including devices that do not use Point and Print or print functionality. For more information, see Point and Print Default Behavior Change and CVE-2021-34481.
To mitigate this issue, verify that you are using the latest drivers for all your printing devices. Where possible, use the same version of the print driver on the print client and print server. If updating drivers in your environment does not resolve the issue, please contact support for your printer manufacturer (OEM).
Windows NT is a well-architected, protected operating system. Unlike Windows 95 and previous version of Windows, it is not possible for applications or user-mode DLLs to access devices directly. To add device support for Windows NT, you need to provide a kernel-mode device driver.
Device drivers are loaded and called by the I/O subsystem. Each request to a device driver is sent in an i/o request packet or IRP. An IRP can be routed through several device drivers in a layered manner: for example, when a file system driver is asked to read a file, it may make a request to the disk driver to read a section of the physical disk. Disk mirroring or striping can be implemented as an intermediate driver that receives all IRP requests going from the file-system to the disk driver. Device driver layering is widely used as a mechanism for sharing code and for structuring device drivers.
Programs and subsystems in user mode are limited in terms of what system resources they have access to, while the kernel mode has unrestricted access to the system memory and external devices. Kernel mode in Windows NT has full access to the hardware and system resources of the computer. The Windows NT kernel is a hybrid kernel; the architecture comprises a simple kernel, hardware abstraction layer (HAL), drivers, and a range of services (collectively named Executive), which all exist in kernel mode.[1]
User mode in Windows NT is made of subsystems capable of passing I/O requests to the appropriate kernel mode device drivers by using the I/O manager. The user mode layer of Windows NT is made up of the "Environment subsystems", which run applications written for many different types of operating systems, and the "Integral subsystem", which operates system-specific functions on behalf of environment subsystems. The kernel mode stops user mode services and applications from accessing critical areas of the operating system that they should not have access to.
The Executive interfaces, with all the user mode subsystems, deal with I/O, object management, security and process management. The kernel sits between the hardware abstraction layer and the Executive to provide multiprocessor synchronization, thread and interrupt scheduling and dispatching, and trap handling and exception dispatching. The kernel is also responsible for initializing device drivers at bootup. Kernel mode drivers exist in three levels: highest level drivers, intermediate drivers and low-level drivers. Windows Driver Model (WDM) exists in the intermediate layer and was mainly designed to be binary and source compatible between Windows 98 and Windows 2000. The lowest level drivers are either legacy Windows NT device drivers that control a device directly or can be a plug and play (PnP) hardware bus.
The kernel sits between the HAL and the Executive and provides multiprocessor synchronization, thread and interrupt scheduling and dispatching, and trap handling and exception dispatching; it is also responsible for initializing device drivers at bootup that are necessary to get the operating system up and running. That is, the kernel performs almost all the tasks of a traditional microkernel; the strict distinction between Executive and Kernel is the most prominent remnant of the original microkernel design, and historical design documentation consistently refers to the kernel component as "the microkernel".
The primary operating system personality on Windows is the Windows API, which is always present. The emulation subsystem which implements the Windows personality is called the Client/Server Runtime Subsystem (csrss.exe). On versions of NT prior to 4.0, this subsystem process also contained the window manager, graphics device interface and graphics device drivers. For performance reasons, however, in version 4.0 and later, these modules (which are often implemented in user mode even on monolithic systems, especially those designed without internal graphics support) run as a kernel-mode subsystem.[26]
Applications that run on NT are written to one of the OS personalities (usually the Windows API), and not to the native NT API for which documentation is not publicly available (with the exception of routines used in device driver development). An OS personality is implemented via a set of user-mode DLLs (see Dynamic-link library), which are mapped into application processes' address spaces as required, together with an emulation subsystem server process (as described previously). Applications access system services by calling into the OS personality DLLs mapped into their address spaces, which in turn call into the NT run-time library (ntdll.dll), also mapped into the process address space. The NT run-time library services these requests by trapping into kernel mode to either call kernel-mode Executive routines or make Local Procedure Calls (LPCs) to the appropriate user-mode subsystem server processes, which in turn use the NT API to communicate with application processes, the kernel-mode subsystems and each other.[28]
Thesycon commands expertise in several areas surrounding the development of device drivers and firmware. Below, we give a selection of the projects that have benefited from our expertise. Each item listed below refers to development work that Thesycon successfully completed either under contract to a client company or as product development. In many cases we worked together with partner companies responsible for hardware design.
The kernel executes in a privileged mode: It can directly access memory and hardware. The kernel consists of several Executive subsystems, which are responsible for managing resources, including the Process Manager, the I/O Manager, the Virtual Memory Manager, the Security Reference Monitor, and a microkernel that handles scheduling and interrupts. The system dynamically loads device drivers, which are kernel components that interface NT to different peripheral devices. The hardware abstraction layer (HAL) hides the specific intricacies of an underlying CPU and motherboard from NT. NT's native API is the API that user-mode applications use to speak to the kernel. This native API is mostly undocumented, because applications are supposed to speak Win32, DOS, OS/2, POSIX, or Win16, and these respective OS environments interact with the kernel on the application's behalf.
NT's processes are virtually the same as VMS's processes (Table 2, page 118, shows a comparison of VMS and NT processes). In NT, as in VMS, the process scheduler implements 32 priority levels. The process with the highest priority is always running, and processes with equal priority are scheduled in a round-robin pattern. The system considers the 16 high-priority levels realtime or fixed priorities, because the process scheduler doesn't manipulate priority in processes the system assigns to that range. The 16 low-priority levels (except 0, which the system reserves for the idle thread that executes when nothing else can) are dynamic because the scheduler, often with the input of device drivers, bumps priorities up in reaction to various conditions, such as when the process receives input from a device. This bumping procedure is called boosting. A defining aspect of the NT and VMS schedulers is that they never lower a process' priority below the priority level the application programmed. To handle CPU hogging, in which a process burns CPU cycles without regard to other processes in the system, the scheduler boosts the priority of starved processes that haven't executed for a defined period. Both VMS 5.0 and NT 3.1 schedulers support symmetric multiprocessing (SMP), which let them execute processes simultaneously on different CPUs in order to increase applications' performance.
NT's I/O Manager is closely based on VMS's I/O Manager. Both OS's I/O Manager support a layered-driver model throughout the device driver stacks for different device types and implements asynchronous packet-based I/O commands, and its device drivers dynamically load and unload. Stackable and loadable drivers make NT and VMS very extensible. Either OS can divide functionality among several device drivers, with each driver implementing a different abstraction level. For example, the system can insert a fault-tolerant disk driver between a file system driver and a disk driver. This configuration lets the fault-tolerant disk driver receive a request the system sends to one logical drive (e.g., the C drive), then send the request to multiple physical drives to implement mirroring or striping. Asynchronous I/O enables applications and the kernel subsystems to initiate device requests and work while the requests are in progress, rather than wait idly for the requests to complete. NT's device driver architecture and interrupt-request priority scheme are based on VMS. Descriptions of these aspects of the I/O Manager are applicable to both OSs with little variation. 2ff7e9595c
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