>
>
> The v86 monitor in "arch/i386/kernel/vm86.c" has a number of
> problems:
>
> 1. The operand size prefix ("0x66") will sometimes be emulated as
> a "pushf" instruction. Obviously most clients will crash
> right away when that happens.
>
> The cause is that the inner switch of handle_vm86_fault() does
> not have a default case.
>
> 2. Extra prefixes will utterly confuse the monitor. This results
> in clients receiving signals they shouldn't have had. For
> example "0x2e 0xcd 0x21" (int 0x21 with a segment prefix) will
> cause a signal.
>
> To solve this, the structure should be rewritten into something
> like
>
> while <prefix>
> <record or discard>
> switch <instruction>
> ...
>
> 3. Instructions "int3" and "into" are not emulated.
>
> 4. The "pushw", "popw", "pushl", and "popl" macros are wrong.
> Pushing and popping shouldn't cause wrap-arounds but exceptions.
I'm not quite sure here. Isn't that a feature of v8086 mode? Or is it
left to the supervisor program. I know that some programs depend on
that (bad) behaviour.
>
>
> All the above is from reading the code, not running it. I might
> have gotten some detail wrong.
>
> Morten Welinder
Ulrich