"Windows 2000内核：核心态对用户态模式演示课件与保护系统的关键"

the protection of the system from user interference and the protection of user processes from each other. In kernel mode, the processor enforces strict control over memory access, with each memory page marked with the required processor state for access. This helps prevent unauthorized access to critical system data and ensures that the system can access its own resources without interference. Additionally, in kernel mode, the ability to execute privileged instructions is controlled, ensuring that only authorized system software can perform certain operations. Windows NT abstracts this concept into two privilege levels: Ring 0 for kernel mode and Ring 3 for user mode. This distinction helps maintain the integrity and security of the system by restricting the capabilities of user applications and granting necessary privileges to system code. Thread management in Windows NT allows for seamless transitions between user mode and kernel mode. Threads can switch between these modes without affecting the overall scheduling of processes, thanks to the preservation of context and registers during these transitions. This allows for efficient and secure execution of both user and system code. The use of counters in Windows NT, such as "privileged time" and "user time," provides a granular view of system activity at different levels, including threads, processes, processors, and the system as a whole. This enables precise monitoring of system performance and resource utilization. Overall, the core concept of kernel mode and user mode in Windows NT serves to protect the system from user errors or malicious actions, ensuring the stability, security, and efficiency of the operating system. By enforcing strict control over memory access, instruction execution, and privilege levels, Windows NT maintains a robust foundation for running critical system processes while safeguarding user applications from potential harm.