Silberschatz, Galvin and Gagne 2002 2.22 Operating System Concepts Memory Protection Must provide memory protection at least for the interrupt vector and the interrupt service routines. In order to have memory protection, add two registers that determine the range of legal addresses a program may access: Base register – holds the smallest legal physical memory address. Limit register – contains the size of the range Memory outside the defined range is protected.
Silberschatz, Galvin and Gagne 2002 2.23 Operating System Concepts Use of A Base and Limit Register
Silberschatz, Galvin and Gagne 2002 2.24 Operating System Concepts Hardware Address Protection
Silberschatz, Galvin and Gagne 2002 2.25 Operating System Concepts Hardware Protection When executing in monitor mode, the operating system has unrestricted access to both monitor and user’s memory. The load instructions for the base and limit registers are privileged instructions.
Silberschatz, Galvin and Gagne 2002 2.26 Operating System Concepts CPU Protection Timer – interrupts computer after specified period to ensure operating system maintains control. Timer is decremented every clock tick. When timer reaches the value 0, an interrupt occurs. Timer commonly used to implement time sharing. Time also used to compute the current time. Load-timer is a privileged instruction.
Silberschatz, Galvin and Gagne 2002 2.27 Operating System Concepts Network Structure Local Area Networks (LAN) Wide Area Networks (WAN)
Silberschatz, Galvin and Gagne 2002 2.28 Operating System Concepts Local Area Network Structure
Silberschatz, Galvin and Gagne 2002 2.29 Operating System Concepts Wide Area Network Structure
You've reached the end of your free preview.
Want to read all 29 pages?
- Fall '19