linux-kernel - Re: [RFC PATCH v4 01/27] x86/cpufeatures: Add CPUIDs for Control-flow Enforcement Technology (CET)

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Date:   Fri, 28 Sep 2018 09:56:32 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
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@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v4 01/27] x86/cpufeatures: Add CPUIDs for
 Control-flow Enforcement Technology (CET)

On Fri, 2018-09-28 at 18:51 +0200, Borislav Petkov wrote:
> On Fri, Sep 21, 2018 at 08:03:25AM -0700, Yu-cheng Yu wrote:
> > Add CPUIDs for Control-flow Enforcement Technology (CET).
> > 
> > CPUID.(EAX=7,ECX=0):ECX[bit 7] Shadow stack
> > CPUID.(EAX=7,ECX=0):EDX[bit 20] Indirect branch tracking
> > 
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> > ---
> >  arch/x86/include/asm/cpufeatures.h | 2 ++
> >  arch/x86/kernel/cpu/scattered.c    | 1 +
> >  2 files changed, 3 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/cpufeatures.h
> > b/arch/x86/include/asm/cpufeatures.h
> > index 89a048c2faec..fa69651a017e 100644
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -221,6 +221,7 @@
> >  #define X86_FEATURE_ZEN			( 7*32+28) /* "" CPU is AMD
> > family 0x17 (Zen) */
> >  #define X86_FEATURE_L1TF_PTEINV		( 7*32+29) /* "" L1TF
> > workaround PTE inversion */
> >  #define X86_FEATURE_IBRS_ENHANCED	( 7*32+30) /* Enhanced IBRS */
> > +#define X86_FEATURE_IBT			( 7*32+31) /* Indirect
> > Branch Tracking */
> >  
> >  /* Virtualization flags: Linux defined, word 8 */
> >  #define X86_FEATURE_TPR_SHADOW		( 8*32+ 0) /* Intel TPR
> > Shadow */
> > @@ -321,6 +322,7 @@
> >  #define X86_FEATURE_PKU			(16*32+ 3) /* Protection
> > Keys for Userspace */
> >  #define X86_FEATURE_OSPKE		(16*32+ 4) /* OS Protection Keys
> > Enable */
> >  #define X86_FEATURE_AVX512_VBMI2	(16*32+ 6) /* Additional AVX512
> > Vector Bit Manipulation Instructions */
> > +#define X86_FEATURE_SHSTK		(16*32+ 7) /* Shadow Stack */
> >  #define X86_FEATURE_GFNI		(16*32+ 8) /* Galois Field New
> > Instructions */
> >  #define X86_FEATURE_VAES		(16*32+ 9) /* Vector AES */
> >  #define X86_FEATURE_VPCLMULQDQ		(16*32+10) /* Carry-Less
> > Multiplication Double Quadword */
> > diff --git a/arch/x86/kernel/cpu/scattered.c
> > b/arch/x86/kernel/cpu/scattered.c
> > index 772c219b6889..63cbb4d9938e 100644
> > --- a/arch/x86/kernel/cpu/scattered.c
> > +++ b/arch/x86/kernel/cpu/scattered.c
> > @@ -21,6 +21,7 @@ struct cpuid_bit {
> >  static const struct cpuid_bit cpuid_bits[] = {
> >  	{ X86_FEATURE_APERFMPERF,       CPUID_ECX,  0, 0x00000006, 0 },
> >  	{ X86_FEATURE_EPB,		CPUID_ECX,  3, 0x00000006, 0 },
> > +	{ X86_FEATURE_IBT,		CPUID_EDX, 20, 0x00000007, 0},
> 
> If you haven't noticed, there's already a separate leaf:
> 
> /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */
> 
> in arch/x86/include/asm/cpufeatures.h
> 

I will change to that one.  Thanks!

Yu-cheng