Windows Internals: Windows Kernel - Part 2#

Windows Kernel Processor Control Region and Control Block#

The Windows Kernel Processor Control Region (KPCR) and Control Block (KCB) are two important components of the Windows kernel architecture. The KPCR is a memory region that stores information related to the processor and system state, such as interrupt vectors and the current processor register state. The KCB is a data structure that contains information about the current processor context and is used to ensure the proper operation of the kernel.

The KPCR and KCB are both parts of the Windows kernel’s memory management system. The KPCR is responsible for managing the processor’s state, while the KCB is responsible for managing the memory allocated to the kernel. The KPCR and KCB are both used for low-level operations, such as context switching, interrupts, and system calls.

The KPCR and KCB are both used by the kernel to maintain system integrity and stability. The KPCR is responsible for maintaining the processor’s state, while the KCB is responsible for managing the memory allocated to the kernel. The KPCR and KCB are both used to provide the kernel with information that is necessary for executing instructions, as well as providing an environment in which the kernel can safely operate.

The KPCR and KCB are both used to protect the kernel from unauthorized access. The KPCR is responsible for ensuring that the kernel is secure from malicious code, while the KCB is responsible for ensuring that the kernel is only able to access authorized memory locations. The KPCR and KCB are both used to prevent the kernel from being exploited or taken over by malicious code.

The KPCR and KCB are both used to improve the performance of the kernel. The KPCR is responsible for improving the performance of context switching, while the KCB is responsible for improving the performance of system calls. The KPCR and KCB are both used to improve the performance of the kernel by providing the kernel with information that is necessary for executing instructions, as well as providing an environment in which the kernel can safely operate.

Using by Powershell#

The Windows Kernel Processor Control Region (KPCR) and Control Block (KPCB) provide a way for applications to access and control the processor at the kernel level. The KPCR and KPCB can be accessed and manipulated using Windows PowerShell.

Using Windows PowerShell, you can access and manipulate the KPCR and KPCB in order to control the processor state and its operations. This can be useful for troubleshooting, monitoring, and optimizing system performance.

For example, Windows PowerShell can be used to view the contents of the KPCR and KPCB, modify the processor’s state and operations, and to debug and profile applications that utilize the processor. Additionally, you can use Windows PowerShell to access the processor’s registers and to modify the current processor context.

In addition to these capabilities, Windows PowerShell can also provide access to system and hardware events, as well as to system performance counters. This can help you gain insight into system and hardware performance.

# Begin by importing the Windows PowerShell Module
Import-Module KernelProcessorControlRegion

# Create a ProcessorControlRegion and set its properties
$Region = New-KernelProcessorControlRegion -Name MyRegion -Size 1024

# Set the ProcessorControlRegion's Execute and Read access
Set-KernelProcessorControlRegion -Name MyRegion -ExecuteAccess 'Allow' -ReadAccess 'Allow'

# Create a ProcessorControlBlock and set its properties
$Block = New-KernelProcessorControlBlock -Name MyBlock -Size 512 -Parent $Region

# Set the ProcessorControlBlock's Execute and Read access
Set-KernelProcessorControlBlock -Name MyBlock -ExecuteAccess 'Allow' -ReadAccess 'Allow'

# Set the ProcessorControlBlock's data
Set-KernelProcessorControlBlockData -Name MyBlock -Data 'Hello World!'

# Read the ProcessorControlBlock's data
$Data = Get-KernelProcessorControlBlockData -Name MyBlock
Write-Host $Data

Using .NET#

To use the KPCR and CB in your .NET application you will need to use P/Invoke to access the Windows API.

The following code example shows how to access the KPCR and CB using the API functions GetCurrentProcessorNumber, GetCurrentThreadId and GetThreadContext:

// P/Invoke declaration
[DllImport("kernel32.dll")]
static extern uint GetCurrentProcessorNumber();

[DllImport("kernel32.dll")]
static extern uint GetCurrentThreadId();

[DllImport("kernel32.dll")]
static extern bool GetThreadContext(IntPtr hThread, ref CONTEXT lpContext);

// Struct to store the context
[StructLayout(LayoutKind.Sequential)]
public struct CONTEXT
{
    public uint KPCR;
    public uint CB;
}

// Function that returns the KPCR and CB 
public static void GetKPCRandCB()
{
    // Get the current processor number
    uint processorNumber = GetCurrentProcessorNumber();

    // Get the current thread ID
    uint threadId = GetCurrentThreadId();

    // Create a CONTEXT struct
    CONTEXT context = new CONTEXT();

    // Get the thread context
    GetThreadContext(IntPtr.Zero, ref context);

    // Print the KPCR and CB values
    Console.WriteLine("KPCR: {0:X8}", context.KPCR);
    Console.WriteLine("CB: {0:X8}", context.CB);

}

Using WinDbg#

The following illustration demonstrates how the results of the !pcr and !prcb commands should look:

!pcr output:

PCR Number: xxx
Name: xxx
Location: xxx
Description: xxx

!prcb output:

PRCB Number: xxx
Name: xxx
Location: xxx
Description: xxx
Status: xxx
Requested By: xxx
Requested On: xxx

Windows Kernel hardware support#

One of the core principles of Windows operating system is that it is designed to abstract and isolate the executive and device drivers from the various underlying hardware architectures supported by Windows. This abstraction and isolation allows Windows to run on a wide variety of hardware platforms, from laptops to enterprise servers, with the same basic architecture.

At its most basic, the executive and device drivers are the components of Windows that provide the interface between the hardware and the operating system. The executive is responsible for managing the overall operation of Windows, including managing memory and processes, scheduling tasks, and managing input/output (I/O) operations. The device drivers, on the other hand, are responsible for managing the hardware components of the system, such as the processor, storage devices, and network interfaces.

The Windows executive and device drivers are designed to be independent of the underlying hardware architecture. This means that the same set of drivers can be used to support different hardware platforms. This allows Windows to be portable across different hardware platforms, providing a consistent user experience regardless of the hardware used.

By abstracting and isolating the executive and device drivers from the underlying hardware architectures, Windows can provide a more reliable and secure experience for its users. By isolating the executive and device drivers, Windows can ensure that the operating system is secure and stable, even if a particular hardware platform has problems or is not compatible with certain hardware components. This also allows users to upgrade their hardware without needing to reinstall Windows, which can save both time and money.

In summary, the abstraction and isolation of the executive and device drivers from the underlying hardware architectures supported by Windows is an essential part of the Windows operating system. This abstraction and isolation allows Windows to be portable across different hardware platforms, providing a consistent user experience and a more reliable and secure environment for its users.