For a secure OS, we need to define supervisor and user mode.
OS Kernel must be in supervisor mode and should be able to access all system resources. Privileged Mode.
User application should work in User Mode and should NOT be able to access system and other application resources. It means Unpriviligede mode.
Mode selection should be done during context switching.
User application can make a system call. In that case Kernel passes to supervisor mode when it finished system call, it should return mode back to unprivilege (user) mode.
For a secure OS, we need to define supervisor and user mode.
Mode selection should be done during context switching.
User application can make a system call. In that case Kernel passes to supervisor mode when it finished system call, it should return mode back to unprivilege (user) mode.