Question

Define the protection mechanism in 80386 microprocessors?

Answer 1

Answer:

The 80386 provides four protection levels for supporting a multitasking operating system to isolate and protect user programs from each other and the operating system. The privilege level controls the use of privileged instructions, I/O instructions, and access to segments and segment descriptors.

Answer 2

The protection mechanism in 80386 microprocessors is as follows:

•               The protection mechanism consists of four layers. They provide an additional protection on page basis. These Protection/Privilege layers are divided from PL0 - PL3, PL0 being the most trusted layer. There are 3 different Privilege Levels:

• Current Privilege Level: CPL refers to the he privilege level(PL) of the currently executing task. It is also called Task Privilege Level(TPL).

• Descriptor Privilege Level: DPL refers to the PL of target segment. It is generally contained in the descriptor of the segment.

• Requester Privilege Level: RPL refers to lowest two bits of any selector. Here, the EPL is calculated as, EPL = max (CPL, RPL) (here numbers).