Same privillege protection

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osnby

Same privillege protection

Post by osnby »

How to perform protection (i386+,pmode) between tasks(segments) of the same privillege level?

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The_Legend

Re: Same privillege protection

Post by The_Legend »

Well for different task, keeps memory regions from one task out of the address space of a different task with the help of paging.
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Re:Same privillege protection

Post by Pype.Clicker »

A possible advanced trick from my wizard-bag (might not work in every situation, though):
  • have a supervisor component that is the one to choose which low-level component is active at a time
  • when giving the access to one of these components, set its descriptor present bit on, leave other descriptors with present bit off.
  • On context switchings between sub-tasks, toggle access bits ...
Now, this has a drawback : the supervisor component can virtually write anything to the table... potentially a protection flaw if not at DPL0 -- or you might have a system call for asking a trusted component to do the "present bit" switch for you ...

Now, this is a never-seen-anywhere-else-and-never-tried idea of mine ... so be wise when using it ;)
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