Overview

This documentation covers system-defined constants used in Windows kernel-mode driver development. These constants are essential for interacting with the Windows operating system kernel and its various components. They represent specific values, flags, or enumerations that control the behavior of drivers and system services.

Key Areas

  • Memory Management Constants: Definitions related to memory allocation, protection, and caching.
  • Object Management Constants: Values used for kernel objects like processes, threads, and events.
  • I/O Manager Constants: Flags and codes for I/O request packets (IRPs) and I/O operations.
  • Synchronization Constants: Defines for synchronization primitives like mutexes, semaphores, and spin locks.
  • Power Management Constants: Values related to system power states and device power management.
  • Registry Constants: Defines for interacting with the Windows Registry.

Commonly Used Constants

Memory Management

Constant Name Description Value (Hex)
PAGE_READONLY Specifies that memory pages can only be read. 0x02
PAGE_READWRITE Specifies that memory pages can be read and written. 0x04
MEM_COMMIT Commits a region of pages, making them accessible. 0x1000
MEM_RESERVE Reserves a range of the process's virtual address space. 0x2000

I/O Manager Flags

Constant Name Description Value (Hex)
IRP_MJ_CREATE Major function code for creating a file or object. 0x00
IRP_MJ_READ Major function code for reading data. 0x02
IRP_MJ_WRITE Major function code for writing data. 0x03
IO_STACK_LOCATION_SIZE Size of an I/O stack location. Calculated

Object Types

Constants like IoDriverObjectType, IoFileObjectType, and IoDeviceObjectType are used when creating or referencing kernel objects.

Using Constants in Drivers

System-defined constants are typically defined in header files provided by the Windows Driver Kit (WDK). For example, memory management constants are found in wdm.h or ntddk.h.

When writing driver code, you'll often use these constants in function calls or conditional statements:

// Example: Allocating memory with specific protections
    PVOID buffer = MmAllocateContiguousMemory(size, startAddress, alignment);
    if (buffer) {
        // Set memory protections (example)
        NTSTATUS status = IoSetIoControl(DeviceObject, IOCTL_MY_DEVICE_SET_MEMORY_PROTECTION, buffer, size, PAGE_READWRITE, ...);
        // ...
    }

Tip

Always refer to the latest WDK documentation for the most accurate and up-to-date definitions of system constants. Some constants may be deprecated or have changed behavior across Windows versions.

Related Topics