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Principper for Samtidighed og Styresystemer - Interrupts

Principper for Samtidighed og Styresystemer - Interrupts

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User- <strong>og</strong> Kernelmode<br />

Behov <strong>for</strong> at sikre dele af styresystemet mod “andre”<br />

Husk: styresystem mappet ind øverst i process-hukommelse<br />

Sikring af priviligerede instruktioner<br />

Instruktioner der kan påvirke andre processer negativt<br />

Standsning af processoren, mode-change, deaktivering af interrupts, . . .<br />

User-mode: til “almindelige” pr<strong>og</strong>rammer<br />

Kernel-mode: til styresystemet<br />

Hvordan skiftes mode?<br />

Example (Pentium)<br />

Fire modes (kaldet rings): 0–3. Windows <strong>og</strong> Linux bruger kun de to.<br />

PSS’09 (Forelæsning 10) <strong>Interrupts</strong> APR 2009 7 / 19

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