linux-kernel - Re: [RFC PATCH v2 6/6] x86/entry/pti: don't switch PGD on when pti

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Message-ID: <CAMFK0gvZ2fPTFFtTeW8A0_gmEovnHnozjxmQ8niHGkxVnpgFow@mail.gmail.com>
Date:   Thu, 11 Jan 2018 20:19:35 +0100
From:   Olivier Galibert <galibert@...ox.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andy Lutomirski <luto@...nel.org>, Willy Tarreau <w@....eu>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH v2 6/6] x86/entry/pti: don't switch PGD on when
 pti_disable is set

Wouldn't the time taken by an easy syscall like getuid be a clear indicator?

  OG.


On Thu, Jan 11, 2018 at 8:17 PM, Dave Hansen
<dave.hansen@...ux.intel.com> wrote:
> On 01/11/2018 11:07 AM, Borislav Petkov wrote:
>> On Thu, Jan 11, 2018 at 10:57:51AM -0800, Dave Hansen wrote:
>>> I'd love to have a tool that tells you for sure "KPTI enabled or not",
>>> but I'd also love to have it be something I can easily distribute
>>> without it being handled like a WMD.
>> You mean this:
>>
>> https://git.kernel.org/tip/87590ce6e373d1a5401f6539f0c59ef92dd924a9
>
> I meant that works across all the kpti implementations.  Those with gunk
> in /sys, /proc/cpuinfo, or with nothing at all like the original KAISER
> patches I posted.
>
> And, yes, I want a pony.  I just though someone had such a pony handy
> and it was trivial.