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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.
Privilege rings for the x86 available in protected mode. This type of privilege escalation occurs when the user or process is able to obtain a higher level of access than an administrator or system developer intended, possibly by performing kernel-level operations.
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.
A privilege level in the x86 instruction set controls the access of the program currently running on the processor to resources such as memory regions, I/O ports, and special instructions. There are 4 privilege levels ranging from 0 which is the most privileged, to 3 which is least privileged.
A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space. [1] [a] Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
System Management Mode (SMM, sometimes called ring −2 in reference to protection rings) [1] [2] is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended.
Other reasons can be the imposition of priority levels as determined by the scheduling policy used for the Low Level Scheduler, and the arrival of a higher priority process into the READY state. RUNNING → BLOCKED: A process is put into the BLOCKED state if it requests something for which it must wait. A request to the OS is usually in the ...
Some operating systems, such as Linux may provide a generic driver for accessing an RPMB device attached to an eMMC. [4] However, in other cases the access to RPMB is controlled through a proprietary driver; this may require use of a Trusted Application instead of a normal application to access the data. [3]