linux-kernel - Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention

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Message-ID: <20161114105911.62a6821c@lxorguk.ukuu.org.uk>
Date:   Mon, 14 Nov 2016 10:59:11 +0000
From:   One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Borislav Petkov <bp@...e.de>, Brian Gerst <brgerst@...il.com>,
        Chen Yucong <slaoub@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        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>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shuah Khan <shuah@...nel.org>, linux-msdos@...r.kernel.org
Subject: Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention

> I took a closer look at the dosemu code. It appears that it does not

That doesn't tell you want DOS itself will try and do...

> purposely utilize SGDT to obtain the descriptor table while in vm86. It
> does use SGDT (in protected mode) to emulate certain functionality such
> as the Virtual xxx Driver. In such a case, UMIP needs to be disabled.
> However, this code seems to be disabled [1]. dosemu includes an i386
> emulator that in some cases uses the actual instructions of the host
> system. In such cases, UMIP might be needed to be disabled.

Is anyone actually still using DOSemu these days or are people all
using DOSbox ?

Alan