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In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation , virtual memory , paging and safe multi-tasking designed to increase an operating system's control over application software .
CPU modes (also called processor modes, CPU states, CPU privilege levels and other names) are operating modes for the central processing unit of most computer architectures that place restrictions on the type and scope of operations that can be performed by instructions being executed by the CPU. For example, this design allows an operating ...
A protection ring is one of two or more hierarchical levels or layers of privilege within the architecture of a computer system. This is generally hardware-enforced by some CPU architectures that provide different CPU modes at the hardware or microcode level. Rings are arranged in a hierarchy from most privileged (most trusted, usually numbered ...
Privilege (computing) In computing, privilege is defined as the delegation of authority to perform security-relevant functions on a computer system. [1] A privilege allows a user to perform an action with security consequences. Examples of various privileges include the ability to create a new user, install software, or change kernel functions.
Privilege escalation is the act of exploiting a bug, a design flaw, or a configuration oversight in an operating system or software application to gain elevated access to resources that are normally protected from an application or user. The result is that an application or user with more privileges than intended by the application developer or ...
A separate user mode can also be used to build efficient virtual machines – see Popek and Goldberg virtualization requirements. With enough privileges, processes can request the kernel to map part of another process's memory space to its own, as is the case for debuggers .
In kernel mode, the processor can execute every instruction in its hardware repertoire, whereas in user mode, it can only execute a subset of the instructions. Instructions that can be executed only in kernel mode are called kernel, privileged, or protected instructions to distinguish them from the user mode instructions.
The principle (of least privilege) is widely recognized as an important design consideration towards enhancing and giving a much needed 'Boost' to the protection of data and functionality from faults (fault tolerance) and malicious behavior. Benefits of the principle include: Intellectual Security. When code is limited in the scope of changes ...