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SubjectRe: More on the pentium workaround - the gotchas


On Sat, 15 Nov 1997, Linus Torvalds wrote:
>
>Note that you don't even need to use SMP to have problems: you can use
>self-modifying code on a UP Pentium. Something like this is likely to
>cause _major_ problems if the BSDi patches really do re-map the IDT (I
>also thought that it might be a good idea to re-map the IDT to make the
>CPU itself to the right thing, but I'm now of the opinion that trying to
>do that is just stupid).
>
>movl $0xf00fc7c8,1f
>1: int3
>
>which will take the int3 trap (because it has been pre-fetched), but then
if the page fault handler notices that it was an

Writing to the prefetch queue will flush it on Pentiums or better.
The move 486->Pentium broke my old DOS routines which tried to detect
whether they
are run single-stepped :-(

regards
chris



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