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Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it.
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.
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.
A memory protection unit (MPU) is a computer hardware unit that provides memory protection. It is usually implemented as part of the central processing unit (CPU). [ 1 ] MPU is a trimmed down version of memory management unit (MMU) providing only memory protection support.
According to the model, the protection state of a computer system can be abstracted as a set of objects , that is the set of entities that needs to be protected (e.g. processes, files, memory pages) and a set of subjects , that consists of all active entities (e.g. users, processes).
In computer security, executable-space protection marks memory regions as non-executable, such that an attempt to execute machine code in these regions will cause an exception. It makes use of hardware features such as the NX bit (no-execute bit), or in some cases software emulation of those features. However, technologies that emulate or ...
For example, Internet Explorer 7 launches its subprocesses with low IL. Windows controls access to objects based on ILs. Named objects, including files, registry keys or other processes and threads, have an entry in their ACL indicating the minimum IL of the process that can use the object. MIC enforces that a process can write to or delete an ...
Some early Intel 64 processors lacked the NX bit required for W^X, but this appeared in later chips. On more limited processors such as the Intel i386, W^X requires using the CS code segment limit as a "line in the sand", a point in the address space above which execution is not permitted and data is located, and below which it is allowed and executable pages are placed.