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Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention

From Stas Sergeev <stsp@list.ru>
Newsgroups linux.kernel
Subject Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention
Date 2017-03-08 23:30 +0100
Message-ID <tiN6q-Q0-29@gated-at.bofh.it> (permalink)
References <tixO1-76a-3@gated-at.bofh.it> <tiKLg-7L9-17@gated-at.bofh.it> <tiN6q-Q0-27@gated-at.bofh.it>
Organization linux.* mail to news gateway

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08.03.2017 19:06, Andy Lutomirski пишет:
> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev <stsp@list.ru> wrote:
>> 08.03.2017 03:32, Ricardo Neri пишет:
>>> These are the instructions covered by UMIP:
>>> * SGDT - Store Global Descriptor Table
>>> * SIDT - Store Interrupt Descriptor Table
>>> * SLDT - Store Local Descriptor Table
>>> * SMSW - Store Machine Status Word
>>> * STR - Store Task Register
>>>
>>> This patchset initially treated tasks running in virtual-8086 mode as a
>>> special case. However, I received clarification that DOSEMU[8] does not
>>> support applications that use these instructions.
> Can you remind me what was special about it?  It looks like you still
> emulate them in v8086 mode.
Indeed, sorry, I meant prot mode here. :)
So I wonder what was cited to be special about v86.

>> Yes, this is the case.
>> But at least in the past there was an attempt to
>> support SLDT as it is used by an ancient pharlap
>> DOS extender (currently unsupported by dosemu1/2).
>> So how difficult would it be to add an optional
>> possibility of delivering such SIGSEGV to userspace
>> so that the kernel's dummy emulation can be overridden?
>> It doesn't need to be a matter of this particular
>> patch set, i.e. this proposal should not trigger a
>> v7 resend of all 21 patches. :) But it would be useful
>> for the future development of dosemu2.
> What I'd actually like to see is a totally separate patchset that adds
> an inheritable (but reset on exec) per-task mask of legacy
> compatibility features to disable.  Maybe:
>
> sys_adjust_compat_mask(int op, int word, u32 mask);
No no, since I meant prot mode, this is not what I need.
I would never need to disable UMIP as to allow the
prot mode apps to do SLDT. Instead it would be good
to have an ability to provide a replacement for the dummy
emulation that is currently being proposed for kernel.
All is needed for this, is just to deliver a SIGSEGV.

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[v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 09/21] x86/insn-eval: Add functions to get default operand and address sizes Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 03/21] x86/mpx: Do not use R/EBP as base in the SIB byte with Mod = 0 Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 08/21] x86/insn-eval: Add utility function to get segment descriptor base address Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 15/21] x86/mm: Relocate page fault error codes to traps.h Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
    Re: [v6 PATCH 15/21] x86/mm: Relocate page fault error codes to traps.h Andy Lutomirski <luto@amacapital.net> - 2017-03-08 17:10 +0100
  [v6 PATCH 11/21] insn/eval: Incorporate segment base in address computation Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 16/21] x86/cpufeature: Add User-Mode Instruction Prevention definitions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 21/21] selftests/x86: Add tests for User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
    Re: [v6 PATCH 21/21] selftests/x86: Add tests for User-Mode  Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-08 17:30 +0100
      Re: [v6 PATCH 21/21] selftests/x86: Add tests for User-Mode  Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 00:40 +0100
  [v6 PATCH 01/21] x86/mpx: Use signed variables to compute effective addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:40 +0100
  [v6 PATCH 20/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 13/21] x86/insn-eval: Add support to resolve 16-bit addressing encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 17/21] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 05/21] x86/insn-eval: Add utility functions to get register offsets Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 12/21] x86/insn: Support both signed 32-bit and 64-bit effective addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 07/21] x86/insn-eval: Add utility function to get segment descriptor Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 18/21] x86/umip: Force a page fault when unable to copy emulated result to user Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 14/21] x86/insn-eval: Add wrapper function for 16-bit and 32-bit address encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 01:50 +0100
  [v6 PATCH 06/21] x86/insn-eval: Add utility functions to get segment selector Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 02:00 +0100
  [v6 PATCH 02/21] x86/mpx: Do not use SIB index if index points to R/ESP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 02:00 +0100
  [v6 PATCH 19/21] x86/traps: Fixup general protection faults caused by UMIP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 02:00 +0100
    Re: [v6 PATCH 19/21] x86/traps: Fixup general protection faults  caused by UMIP Andy Lutomirski <luto@amacapital.net> - 2017-03-08 17:00 +0100
  [v6 PATCH 10/21] x86/insn-eval: Do not use R/EBP as base if mod in ModRM is zero Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 02:10 +0100
  [v6 PATCH 04/21] x86/mpx, x86/insn: Relocate insn util functions to a new insn-kernel Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-08 04:50 +0100
  Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-08 15:30 +0100
    Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-08 18:00 +0100
      Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-09 02:20 +0100
        Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-09 23:10 +0100
        Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@kernel.org> - 2017-03-10 03:50 +0100
          Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-10 22:00 +0100
            Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-10 22:10 +0100
              Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-10 22:40 +0100
    Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-08 18:20 +0100
      Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-09 02:20 +0100
        Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-09 23:20 +0100
          Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-10 03:50 +0100
            Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-10 12:40 +0100
              Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-10 15:20 +0100
                Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 02:30 +0100
              Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 01:10 +0100
            Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 01:00 +0100
    Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-08 23:30 +0100
    Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-08 23:50 +0100
    Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-09 02:50 +0100
      Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-10 02:30 +0100
        Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 00:50 +0100
          Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2017-03-11 01:00 +0100
            Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-03-11 01:20 +0100
  Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2017-03-08 17:20 +0100

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