linux-kernel - Re: [PATCH 3/4] x86/umip: Identify the str and sldt instructions

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Date:   Tue, 14 Nov 2017 08:20:23 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        ricardo.neri@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] x86/umip: Identify the str and sldt instructions


* Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> wrote:

> On Mon, Nov 13, 2017 at 09:12:03AM +0100, Ingo Molnar wrote:
> > 
> > * Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> wrote:
> > 
> > > The instructions str and sldt are not emulated in any case. Thus, it made
> > > sense to not implement functionality to identify them. However, a
> > > subsequent commit will introduce functionality to warn about the use of
> > > all the instructions that UMIP protect, not only those that are emulated.
> > > A first step for that is the ability to identify them.
> > > 
> > > Plus, now that str and sldt are identified, we need to explicitly avoid
> > > their emulation (i.e., not rely on unsuccessful identification). Group
> > > togehter all the cases that we do not want to emulate: str, sldt and user
> > > long mode processes.
> > 
> > Did you notice how in all your previous patches (both in the code and in the 
> > changelogs) I have manually fixed up the capitalization of these instruction 
> > mnenonics?
> 
> I am sorry, I tried to see where you made these changes but I could not find
> any. I did a git diff of arch/x86/kernel/umip.c between the branch rneri/umip_v11
> of my repository [1] and the master branch of the tip tree and I did not find
> any differences.

For example, I turned:

  [PATCH v11 12/12] selftests/x86: Add tests for instruction str and sldt

  The instructions str and sldt are not valid when running on virtual-8086
  mode and generate an invalid operand exception.
  ...

into:

  a9e017d5619e: selftests/x86: Add tests for the STR and SLDT instructions

  The STR and SLDT instructions are not valid when running on virtual-8086
  mode and generate an invalid operand exception.
  ...

I did not catch every case though.

Thanks,

	Ingo