Re: [v2 5/7] x86: Add emulation code for UMIP instructions

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [v2 5/7] x86: Add emulation code for UMIP instructions
Date	2016-12-31 03:10 +0100
Message-ID	<sUhho-57Y-15@gated-at.bofh.it> (permalink)
References	(1 earlier) <sRJtw-6WG-15@gated-at.bofh.it> <sRK6d-7Lj-1@gated-at.bofh.it> <sTarD-O9-9@gated-at.bofh.it> <sTaBj-RM-1@gated-at.bofh.it> <sTXVn-7y-7@gated-at.bofh.it>
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On Thu, Dec 29, 2016 at 9:23 PM, Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
> On Tue, 2016-12-27 at 16:48 -0800, Andy Lutomirski wrote:
>>
>> >> > +               if (nr_copied  > 0)
>> >> > +                       return -EFAULT;
>> >>
>> >> This should be the only EFAULT case.
>> > Should this be EFAULT event if the caller cares only about successful
>> > (return 0) vs failed (return non-0) emulation?
>>
>> In theory this particular error would be a page fault not a general
>> protection fault (in the UMIP off case).  If you were emulating it
>> extra carefully, you could change the signal accordingly.  But, as I
>> said, I really doubt this matters.
>
> If simple enough and for the sake of accuracy, I could try to issue the
> page fault. It seems to me that this entitles calling
> force_sig_info_fault in this particular case as opposed to the
> force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk) that do_general_protection
> calls.

Sure.  You could even do it by sending the signal in the emulation
code and returning true.

--Andy

Thread

[v2 0/7] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
  [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
    Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-24 03:20 +0100
      Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-28 01:40 +0100
        Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-28 01:50 +0100
          Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-30 06:30 +0100
            Re: [v2 5/7] x86: Add emulation code for UMIP instructions Andy Lutomirski <luto@amacapital.net> - 2016-12-31 03:10 +0100
    Re: [v2 5/7] x86: Add emulation code for UMIP instructions Masami Hiramatsu <mhiramat@kernel.org> - 2016-12-25 17:00 +0100
      Re: [v2 5/7] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-28 01:50 +0100
  [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a new insn-utils Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils kbuild test robot <lkp@intel.com> - 2016-12-24 03:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils Masami Hiramatsu <mhiramat@kernel.org> - 2016-12-25 07:20 +0100
      Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a  new insn-utils Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-27 23:40 +0100
    Re: [v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a new  insn-utils Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-03 17:50 +0100
  [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used along with R/EBP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-24 02:50 +0100
    Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Andy Lutomirski <luto@amacapital.net> - 2016-12-24 03:00 +0100
      Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-12-27 23:40 +0100
        Re: [v2 2/7] x86/mpx: Fail when implicit zero-displacement is used  along with R/EBP Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-03 17:50 +0100

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