Process Protection
-
Proper protection must be provided to prevent a process from inappropriately
affecting another process or itself.
-
Page tables are kept in the address space of the operating system.
-
Virtual memory systems keep bits in the page table and TLB entries
to indicate the type and level of access that the process has to each
of the pages.
-
Two modes of execution are supported:
-
User mode is used by the process.
-
Kernel mode is used by the operating system.
This mode can be used for updating page tables and accomplishing I/O.
-
A switch from user to kernel mode is accomplished by a system call.
-
A switch from kernel to user mode is accomplished by returning from
an exception (system call).
|
