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

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Message-ID: <79ba0fff-4c01-2bfa-06cb-5cfc98dd710c@list.ru>
Date:   Wed, 8 Mar 2017 17:08:54 +0300
From:   Stas Sergeev <stsp@...t.ru>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org
Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention

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.
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.