linux-kernel - Re: [PATCH v24 04/30] x86/cpufeatures: Introduce X86_FEATURE

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Date:   Sat, 10 Apr 2021 11:29:51 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Yu, Yu-cheng" <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@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.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>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>
Subject: Re: [PATCH v24 04/30] x86/cpufeatures: Introduce X86_FEATURE_CET and
 setup functions

On Fri, Apr 09, 2021 at 04:14:09PM -0700, Yu, Yu-cheng wrote:
> > @@ -53,6 +55,8 @@ static short xsave_cpuid_features[] __initdata = {
> >   	X86_FEATURE_INTEL_PT,
> >   	X86_FEATURE_PKU,
> >   	X86_FEATURE_ENQCMD,
> > +	X86_FEATURE_CET, /* XFEATURE_CET_USER */
> > +	X86_FEATURE_CET, /* XFEATURE_CET_KERNEL */
> > 
> > or what is the piece which becomes simpler?
> 
> Yes, this is it.

Those should be X86_FEATURE_SHSTK no?

> Signals, arch_prctl, and ELF header are three places that need to depend on
> either shadow stack or IBT is configured.  To remain simple, we can make all
> three depend on CONFIG_X86_SHADOW_STACK, and in Kconfig, make CONFIG_X86_IBT
> depend on CONFIG_X86_SHADOW_STACK.  Without shadow stack, IBT itself is not
> as useful anyway.

Makes sense to me.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette