Virtual Memory Area
Virtual Memory Area is also called Memory Region in some book.
In the process address spaces, there are many memory areas, contiguous addresses wil be divided into different memory area if the access right of them are different. For example, in one Java Process, there are 359 memory areas.
so the kernel need to find a effective way to insert into, remove from, search from the list of memory areas. The semantics of find_area API is the as the following.
return null if
1. The list itself is empty.
2. The list is not empty, and the address is big than the last memory area.
return found area if
1. the address is in the region of one area.
2. the address is not in the region of any area. but is not bigger than the last area.
it means it is in the hole between areas. right area besides the hole is returned.