Re: Pentium emulation

Russell Coker - mailing lists account (bofh@snoopy.virtual.net.au)
Wed, 30 Jul 97 18:51:52 +1100


>> > Couldn't the kernel provide emulation of the Pentium instructions
>> > for the 386/486, to solve this problem? I guess it could be done
>> > since it would be very similar to the FPU emulator.
>> >
>> > So the question is mainly: Would it make sense?
>>
>> Not really. Except for BSWAP the 386/486/586 user mode stuff is basically
>> all down to how you order instructions and how you align them not to new
>> instructions

>I thought there was some problem with 386s not write faulting correctly
>when you had kernel level privileges? Hence the 386/486 differences in
>verify_area.

A couple of years ago someone posted some assembly that would lock any
386 up solid. It didn't require kernel mode and worked on OS/2 as well as
Linux (so I doubt that it was related to a Linux bug). It was apparently
impossible to work-around this bug, thus if you want to run a multi-user
system in a hostile environment then you need something other than a 386.

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