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Robert Gomez
Robert Gomez

Windows Vista Kernel: Part 3 - The Complete Reference for Security, Reliability and Recovery



Inside the Windows Vista Kernel: Part 3




In this article, we will explore some of the key features and improvements of the Windows Vista kernel, the core component of the operating system that manages memory, processes, threads, I/O, security and more. This is the third and final part of a series that covers the Windows Vista kernel in depth. In the previous parts, we discussed the changes in memory management, reliability, performance and power management. In this part, we will focus on process and thread management, I/O system and security.




Inside the Windows Vista Kernel: Part 3



Process and Thread Management




A process is a container for a set of resources, such as virtual memory, handles, environment variables and security tokens, that are used by one or more threads of execution. A thread is a unit of execution that runs on a processor and has its own stack, registers and instruction pointer. Processes and threads are fundamental concepts in any operating system, and Windows Vista has made some significant enhancements in this area.


One of the main goals of Windows Vista was to improve the responsiveness and interactivity of the system, especially under heavy load or resource contention. To achieve this, the kernel introduced several new mechanisms to manage processes and threads more efficiently and fairly.


One of these mechanisms is Process Feedback, which allows the kernel to monitor the CPU usage and responsiveness of each process and adjust its priority accordingly. Process Feedback works by assigning each process a base priority class (such as Normal, High or Realtime) and a dynamic priority boost (from 0 to 31) based on its feedback score. The feedback score is calculated by measuring how often the process receives user input, how quickly it responds to it, how much CPU time it consumes and how long it waits for I/O operations. The higher the feedback score, the higher the priority boost. This way, processes that are more interactive and responsive get more CPU time than processes that are less interactive or consume too much CPU time.


Another mechanism is Thread Parking, which allows the kernel to reduce the number of active threads on a multiprocessor system when there is CPU contention. Thread Parking works by identifying threads that are idle or low-priority and moving them to a parked state, where they do not consume any CPU resources until they are unparked. This reduces the overhead of context switching and cache pollution, and improves the performance and scalability of the system. Thread Parking is especially beneficial for systems with many cores or processors.


A third mechanism is I/O Prioritization, which allows the kernel to prioritize I/O requests based on their importance and urgency. I/O Prioritization works by assigning each I/O request a priority level (from Critical to Very Low) based on its source process, type (such as paging or prefetching) and flags (such as synchronous or asynchronous). The higher the priority level, the sooner the I/O request is serviced by the device driver or file system. This way, I/O requests that are more critical or time-sensitive get faster access to disk or network resources than I/O requests that are less critical or time-sensitive.


I/O System




The I/O system is responsible for managing all input/output operations between user-mode applications and kernel-mode device drivers or file systems. The I/O system consists of several components, such as I/O Manager, Plug and Play Manager, Power Manager, Device Stack, File System Stack and Cache Manager. Windows Vista has made some major improvements in the I/O system to enhance its functionality, reliability and performance.


One of these improvements is Transactional NTFS, which allows applications to perform multiple file system operations as a single atomic transaction. Transactional NTFS works by using a log file to record all changes made by a transaction before committing them to disk. If the transaction succeeds, all changes are applied atomically; if the transaction fails or is aborted, all changes are rolled back automatically. This ensures the consistency and integrity of the file system, and simplifies the error recovery and undo operations for applications.


Another improvement is Self-Healing NTFS, which allows the file system to detect and repair common errors and corruptions without requiring a full disk check or user intervention. Self-Healing NTFS works by using a new metadata structure called $REPAIR to store information about the errors and corruptions detected by the file system. When an error or corruption is encountered, the file system tries to fix it on the fly or marks it as pending for repair. The repair process is performed in the background by a new service called NTFS Health Service, which uses the information in $REPAIR to fix the errors and corruptions without affecting the normal operation of the system.


A third improvement is ReadyBoost, which allows the system to use a removable flash memory device, such as a USB drive or a memory card, as a cache for frequently accessed data. ReadyBoost works by using a new driver called Ecache.sys to manage the flash memory device and a new service called Emdmgmt to monitor its performance and reliability. When ReadyBoost is enabled, the system copies some of the data from the hard disk to the flash memory device, and uses it as an additional source of data when servicing read requests. This reduces the latency and load of the hard disk, and improves the responsiveness and performance of the system.


Security




Security is one of the most important aspects of any operating system, and Windows Vista has made some significant enhancements in this area to protect the system and its users from various threats and attacks. Some of these enhancements are:



  • User Account Control (UAC), which is a mechanism that enforces the principle of least privilege by requiring users to provide consent or credentials before performing administrative tasks or running applications that require elevated privileges. UAC works by using a new security token called a split token, which contains two parts: a standard user part and an administrator part. When a user logs on to the system, he or she receives a split token with both parts enabled. However, when he or she launches an application or performs a task that requires elevation, UAC prompts him or her for consent or credentials, and then creates a new process with only the administrator part of the token enabled. This way, UAC reduces the exposure and attack surface of the system by limiting the number of processes that run with elevated privileges.



  • Windows Service Hardening (WSH), which is a mechanism that restricts the actions and resources that a service can access based on its identity and purpose. WSH works by using a new security feature called Service SID, which assigns a unique security identifier (SID) to each service based on its name. The Service SID is added to the service's security token when it starts, and can be used to grant or deny permissions to specific resources, such as files, registry keys or network ports. This way, WSH reduces the impact and damage of a service compromise by limiting what a service can do and access.



  • Kernel Patch Protection (KPP), which is a mechanism that prevents unauthorized modifications to critical kernel code or data by third-party software, such as rootkits or drivers. KPP works by using a new feature called PatchGuard, which periodically checks the integrity of certain kernel structures, such as system call table, interrupt descriptor table or global descriptor table. If PatchGuard detects any tampering or corruption, it triggers a bug check and shuts down the system. This way, KPP protects the stability and security of the system by preventing malicious code from running in kernel mode.



Conclusion




In this article, we have explored some of the key features and improvements of the Windows Vista kernel in terms of process and thread management, I/O system and security. These features and improvements demonstrate how Windows Vista has evolved from its predecessors to provide a more robust, responsive and secure operating system for its users. However, Windows Vista is not without its flaws and limitations, and some of these features and improvements have been further refined or replaced by newer versions of Windows. Therefore, it is important to keep up with the latest developments and updates in the Windows world.


FAQs





  • Q: What is the difference between Windows Vista kernel mode and user mode?



  • A: Kernel mode is a privileged mode of execution that allows code to access all hardware resources and memory locations. User mode is an unprivileged mode of execution that restricts code to access only certain hardware resources and memory locations through system calls or APIs. The kernel runs in kernel mode, while applications run in user mode.



  • Q: What are some benefits of using Transactional NTFS I have already written the article for you. Here is the rest of it:



  • A: Some benefits of using Transactional NTFS are: it ensures the consistency and integrity of the file system, it simplifies the error recovery and undo operations for applications, it allows concurrent access to the same files by multiple transactions, and it supports nested and distributed transactions.



  • Q: What are some drawbacks of using ReadyBoost?



  • A: Some drawbacks of using ReadyBoost are: it does not improve the performance of write-intensive applications, it requires a compatible and fast flash memory device, it consumes some system memory and CPU resources, and it may reduce the lifespan of the flash memory device due to frequent writes.



  • Q: What are some alternatives to Kernel Patch Protection?



  • A: Some alternatives to Kernel Patch Protection are: using digital signatures to verify the authenticity and integrity of kernel code or data, using hardware-based features such as NX bit or VT-x to prevent execution of unauthorized code in kernel mode, or using hypervisors or virtual machines to isolate and monitor kernel activities.



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