Encyclopedia

privileged instruction

privileged instruction

[′priv·ə·lijd in′strək·shən]
(computer science)
A class of instructions, usually including storage protection setting, interrupt handling, timer control, input/output, and special processor status-setting instructions, that can be executed only when the computer is in a special privileged mode that is generally available to an operating or executive system, but not to user programs.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

privileged instruction

A machine code instruction that may only be executed when the processor is running in supervisor mode. Privileged instructions include operations such as I/O and memory management.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
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References in periodicals archive
KFUPM also supplies students with privileged instruction and training to make them able to contribute to comprehensive development after graduation, the rector said.
Underlying hardware mechanisms, such as the MMU, privileged instruction access control (i.e.
Exception Level I (ELI), which executes an OS and anything else that executes privileged instructions;
To perform the emulation of privileged instructions, Disco additionally maintains the privileged registers and TLB contents of the virtual CPU in this structure.
Supervisor mode allows the operating system to use a protected portion of the address space (the supervisor segment), but does not give access to privileged instructions or physical memory.
To reduce this overhead, we patched the HAL of IRIX to convert these frequently used privileged instructions to use nontrapping load and store instructions to a special page of the address space that contains these registers.
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