Security in Computing, Third Edition

4.3. Control of Access to General Objects

Protecting memory is a specific case of the more general problem of protecting objects. As multiprogramming has developed, the numbers and kinds of objects shared have also increased. Here are some examples of the kinds of objects for which protection is desirable:

• memory

• a file or data set on an auxiliary storage device

• an executing program in memory

• a directory of files

• a hardware device

• a data structure, such as a stack

• a table of the operating system

• instructions, especially privileged instructions

• passwords and the user authentication mechanism

• the protection mechanism itself

The memory protection mechanism can be fairly simple because every memory access is guaranteed to go through certain points in the ...