| Revision as of 16:07, 3 July 2017 edit161.30.211.131 (talk) Revert damage← Previous edit | Revision as of 03:36, 11 August 2017 edit undo2601:587:100:53fe:718d:9d3a:cee4:10da (talk) Redirected to Protection ringNext edit → | ||
| Line 1: | Line 1: | ||
| #redirect ] | |||
| {{merge to|Protection ring|discuss=Talk:Protection ring#Proposed merge with Privilege level|date=June 2017}} | |||
| {{refimprove|date=June 2017}} | |||
| ] | |||
| A '''privilege level''' in the ] and ] ] 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. Most modern operating systems use level 0 for the kernel/executive, and use level 3 for application programs. Any resource available to level n is also available to levels 0 to n, so the privilege levels are "]". When a lesser privileged process tries to access a higher privileged process, a General Protection Fault is reported by the OS. | |||
| It is not necessary to use all four privilege levels, because the current ] like Windows, Linux, etc. mostly are using ] mechanism and Paging only has one bit to specify the privilege level which is either Supervisor or User (U/S Bit). ] uses the two-level system.<ref>Russinovich, Mark E.; David A. Solomon (2005). Microsoft Windows Internals (4 ed.). Microsoft Press. pp. 16. {{ISBN|978-0-7356-1917-3}}</ref> | |||
| The real mode programs in 8086 are executed at level 0 (highest privilege level) whereas virtual mode in 8086 executes all programs at level 3.<ref>Sunil Mathur, "Microprocessor 8086: Architecture, Programming and Interfacing" , Eastern Economy Edition, PHI Learning</ref> | |||
| == See also == | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| ==References== | |||
| {{reflist}} | |||
| * Intel 80386 Programmer's Reference | |||
| ] | ] | ||
Revision as of 03:36, 11 August 2017
Redirect to:
Category: