page scheme: protection
memory access ranges
For all processes, there is a range of logical addresses. This is usually the same for all processes.
Only some processes may have restricted addresses. This is attached to eachas a valid bit. When accessing memory, OS checks against this bit.
Sharing physical memory
Read only pages can be shared across pages. For instance c-stdlib, syscalls.
We can have copy on write, as soon as a process tries to write to a page, we duplicate it before modifying (if it isnt the only one accessing).