V86 without tss

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V86

V86 without tss

Post by V86 »

is it possible to switch into v86 without tss ?
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Brendan
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Re:V86 without tss

Post by Brendan »

Hi,
V86 wrote: is it possible to switch into v86 without tss ?
IIRC, it is possible to switch to v86 mode without a TSS (using "IRET"), but it's impossible to switch back to CPL=0 without the TSS, which means you can't use any IOPL sensitive instructions (CLI/STI, IN, OUT, etc) without causing a triple fault.

Of course you can have heaps of different tasks/threads all using v86 if you feel like using a single TSS....


Cheers,

Brendan
For all things; perfection is, and will always remain, impossible to achieve in practice. However; by striving for perfection we create things that are as perfect as practically possible. Let the pursuit of perfection be our guide.
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mystran

Re:V86 without tss

Post by mystran »

AFAIK Brendan's correct. The only thing you really need TSS for is switching to a more priviledged level, and even then it's only really useful for loading a new stack. But without TSS, no higher priviledge stack, and therefore no switching to higher priviledge level, and therefore triple fault when trying to.
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