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    SubjectRe: ESP corruption bug - what CPUs are affected?
    Date
    Gabriel Paubert wrote:
    > Hi,
    >
    >
    >>It does not restore it in any case for the 16bit
    >>stack (no matter whether the code is 16 or 32 in PM).
    >>Petr says V86 is not affected, but I have not tested
    >>that case because why to care? The problem is only for
    >>the 32bit code. For 16bit code (PM or V86) it just
    >>doesn't really matter I think (I don't think using
    >>prefixes for ESP is sane).
    >
    >
    > Well, thrashing a register at any time under the user
    > just because an interrupt happened is even less sane ;-)
    >
    >
    >>>I'm absolutely amazed by the fact that this bug has been there
    >>>since the beginning and only seems to hit users right now.
    >>
    >>No, right now it just hits me:)
    >>It used to hit the dosemu users always, but people just
    >>blamed dosemu itself and that was it. Noone wanted
    >>to spend weeks traceing the DOS programs under dosemu,
    >>then traceing dosemu itself, then traceing kernel,
    >>then looking through the docs to track the problem down
    >>to something known, then writing to Intel's techsup for
    >>clarifications, and then writing to LKML:) And if not
    >>for the great help I got here, this will end up nowhere
    >>again. So that's how it used to stay "unnoticed" for
    >>years.
    >
    >
    > I see. And finally we know that the problem with the
    > processor and that Intel changed the spec to conform
    > to what the hardware does but is rather coy about it.
    >
    >
    >>As for the other instances of that problem, here are some:
    >>
    >>http://www.tenberry.com/dos4g/watcom/rn4gw.html
    >>---
    >>B ** Fixed the mouse32 handler to ignore a Microsoft Windows DOS box bug
    >> which mangles the high word of ESP.
    >
    >
    > But if the bug is also affects Windows DOS box, it means that
    > V86 is affected too, no?
    >
    > I'd like to know what OS/2 did. The DOS boxes and 16 bit mode
    > DPMI applications ran very well and it was very stable, despite
    > the fact that the kernel spent its time switching between 16
    > and 32 bit modes (for example, almost all device drivers were
    > 16 bit code, but the drivers for DOS emulation were 32 bit).
    > But I removed it from all my machines several years ago.

    May I suggest that IBM is a friend of Linux, and that *if* there is a
    simple way to get around the problem they will probably be very willing
    to share it with us.

    --
    -bill davidsen (davidsen@tmr.com)
    "The secret to procrastination is to put things off until the
    last possible moment - but no longer" -me
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