Memory protection

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Memory protection is the property of operating systems to divide up the available memory and to separate running programs from one another in such a way that a programming error or crash of an individual program does not impair the stability of other programs or the overall system. Programs are prevented from accidentally or intentionally accessing the memory area of ​​other programs or from using the operating system other than through standardized interfaces ("inputs"). On the hardware side, a memory management unit ( MMU ) or a simpler memory protection unit ( MPU ) can support memory protection. However, pure software solutions are also possible. If a program tries to access a protected address space, a protection violation occurs .

All modern multitasking operating systems have a memory protection mechanism. Operating systems on which only individual applications run, for example in embedded systems , usually do not need this.

In a second meaning of the term is memory protection also be used within a process - the address space to prevent, contain memory areas, the data as code can be accessed, and, conversely, that memory areas containing the code, not (with data) overwritten can be. This is to prevent z. B. code can be changed by buffer overflow or code can be introduced by entering special data ( NX bit , Von Neumann architecture ).

Examples

Operating systems without memory protection

Operating systems with limited memory protection

Operating systems with full memory protection

See also

literature

  • Hermann Eichele: Multiprocessor Systems. BG Teubner Verlag, Stuttgart 1990, ISBN 978-3-519-06128-1 , pp. 221-222.
  • Heinz Schecher: Functional structure of digital computing systems. Springer Verlag Berlin Heidelberg, Berlin Heidelberg 1973, pp. 194–196.
  • Thomas Flik, ​​Hans Liebig: Microprocessor technology. System structure - functional processes - programming, third edition, Springer Verlag Berlin Heidelberg GmbH, Berlin Heidelberg 1990, ISBN 978-3-540-52394-9 , pp. 182-185.

Web links