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    SubjectRE: RFC: WMI Enhancements
    Date
    > -----Original Message-----
    > From: Andy Lutomirski [mailto:luto@kernel.org]
    > Sent: Thursday, April 13, 2017 12:44 PM
    > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
    > Cc: Darren Hart <dvhart@infradead.org>; Andrew Lutomirski <luto@kernel.org>;
    > Michał Kępień <kernel@kempniu.pl>; Rafael J. Wysocki <rjw@rjwysocki.net>; Len
    > Brown <len.brown@intel.com>; Pali Rohár <pali.rohar@gmail.com>; Corentin
    > Chary <corentin.chary@gmail.com>; Andy Shevchenko
    > <andriy.shevchenko@linux.intel.com>; linux-kernel@vger.kernel.org; platform-
    > driver-x86@vger.kernel.org; linux-pm@vger.kernel.org
    > Subject: Re: RFC: WMI Enhancements
    >
    > On Thu, Apr 13, 2017 at 10:39 AM, <Mario.Limonciello@dell.com> wrote:
    > >> -----Original Message-----
    > >> From: Darren Hart [mailto:dvhart@infradead.org]
    > >> Sent: Thursday, April 13, 2017 12:06 PM
    > >> To: Limonciello, Mario <Mario_Limonciello@Dell.com>
    > >> Cc: luto@kernel.org; kernel@kempniu.pl; rjw@rjwysocki.net;
    > >> len.brown@intel.com; pali.rohar@gmail.com; corentin.chary@gmail.com;
    > >> andriy.shevchenko@linux.intel.com; linux-kernel@vger.kernel.org; platform-
    > >> driver-x86@vger.kernel.org; linux-pm@vger.kernel.org
    > >> Subject: Re: RFC: WMI Enhancements
    > >>
    >
    > > Well the "most" interesting to me is the SMBIOS calling interface on the
    > > regular Dell GUID (WMBA IIRC). That's what is used to manipulate keyboard
    > > LED timeouts in dell-laptop (although through direct SMI today).
    > >
    > > It's also what is used for other SMBIOS calls like changing random BIOS settings
    > > that shouldn't be generically exposed in sysfs but should be controlled by
    > > manageability tools.
    > >
    > > Example: turning on/off legacy option ROM or changing legacy boot order.
    > >
    >
    > IIUC we basically can't expose the SMI--based interface to this entry
    > point to userspace because of its use of physical addressing. It is
    > reasonably safe to expose the WMI version? (IOW should be expect that
    > it doesn't enable kernel-mode or SMM code execution?)

    The SMI based entry is already exposed using dcdbas.

    The WMI version when executing a call that would be run as a SMI
    will copy the buffer to an area of memory that the BIOS has already
    been marked reserved to execute the SMI and copy the result out.

    >
    > TBH, I've occasionally considered writing a driver to expose SMM code
    > execution on systems with a known reliable exploit :)

    On Dell HW? I'm sure our security folks would be very interested in this.
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