Memory Protection

The  area  in  the  memory  that  a  process  is  permitted  to  access  is  called  as  process address space . To ensure accurate operation of a computer system, we require ensuring that a process cannot access memory outside the address space. If we don't do this then a process might, accidentally or deliberately, overwrite the address space of another process or memory space belonging to the operating system (such as for the interrupt vector table).

Using two CPU registers, which are specifically designed for this purpose, can give the memory protection. These registered are as follows:

Base register - it contains the smallest legal physical memory address for a process

Limit register - it holds the size of the process

When a process is loaded into memory, the base register is initialized with the beginning address of the process and the limit register is initialized with the size. Memory outside the defined range is secluded because the CPU checks that every address generated by process falls within the memory range defined by the values stored in base and limit registers, as shown in Figure drawn below

Figure Hardware address protection with base and limit registers

In Figure drawn below we use an example to illustrate how the concept given above works. The base and limit registers are initialized to describe the address space of a process. The process begins at memory location 300040 and its size is 120900 bytes (supposing that memory is byte addressable). Throughout the execution of this process, the CPU insures (by using the logic outlined in Figure drawn above) that all the addresses generated by this process are greater than or equal to 300040 and less than the (300040+120900), thereby preventing this process to access any memory area in exterior of its address space. Loading the base and limit registers are the privileged instructions.

Figure Use of Base and Limit Register

Email based Operating System  assignment help - homework help at Expertsmind

Are you searching Operating System expert for help with Memory Protection questions?  Memory Protection topic is not easier to learn without external help?  We at www.expertsmind.com offer finest service of operating system assignment help and operating system homework help. Live experts are available for 24x7 hours helping students in their Memory Protection related problems. We provide step by step Memory Protection question's answers with 100% plagiarism free content. We prepare quality content and notes for Memory Protection topic under operating system theory and study material. These are avail for subscribed users and they can get advantages anytime.

Why Expertsmind for assignment help

1. Higher degree holder and experienced tutors network
2. Punctuality and responsibility of work
3. Quality solution with 100% plagiarism free answers
4. Time on Delivery
5. Privacy of information and details
6. Excellence in solving operating system questions in excels and word format.
7. Best tutoring assistance 24x7 hours