linux-kernel - Re: [RFC PATCH v2 18/27] x86/cet/shstk: Introduce WRUSS instruction

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Date:   Wed, 11 Jul 2018 17:27:54 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omiun.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v2 18/27] x86/cet/shstk: Introduce WRUSS instruction

On Wed, Jul 11, 2018 at 07:58:09AM -0700, Yu-cheng Yu wrote:
> On Wed, 2018-07-11 at 11:45 +0200, Peter Zijlstra wrote:
> > On Tue, Jul 10, 2018 at 03:26:30PM -0700, Yu-cheng Yu wrote:
> > > 
> > > diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-
> > > opcode-map.txt
> > > index e0b85930dd77..72bb7c48a7df 100644
> > > --- a/arch/x86/lib/x86-opcode-map.txt
> > > +++ b/arch/x86/lib/x86-opcode-map.txt
> > > @@ -789,7 +789,7 @@ f0: MOVBE Gy,My | MOVBE Gw,Mw (66) | CRC32
> > > Gd,Eb (F2) | CRC32 Gd,Eb (66&F2)
> > >  f1: MOVBE My,Gy | MOVBE Mw,Gw (66) | CRC32 Gd,Ey (F2) | CRC32
> > > Gd,Ew (66&F2)
> > >  f2: ANDN Gy,By,Ey (v)
> > >  f3: Grp17 (1A)
> > > -f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey
> > > (F2),(v)
> > > +f5: BZHI Gy,Ey,By (v) | PEXT Gy,By,Ey (F3),(v) | PDEP Gy,By,Ey
> > > (F2),(v) | WRUSS Pq,Qq (66),REX.W
> > >  f6: ADCX Gy,Ey (66) | ADOX Gy,Ey (F3) | MULX By,Gy,rDX,Ey (F2),(v)
> > >  f7: BEXTR Gy,Ey,By (v) | SHLX Gy,Ey,By (66),(v) | SARX Gy,Ey,By
> > > (F3),(v) | SHRX Gy,Ey,By (F2),(v)
> > >  EndTable
> > Where are all the other instructions? ISTR that documentation patch
> > listing a whole bunch of new instructions, not just wuss.
> 
> Currently we only use WRUSS in the kernel code.  Do we want to add all
> instructions here?

Yes, since we also use the in-kernel decoder to decode random userspace
code.