linux-kernel - Re: [PATCH v2 10/20] x86: avoid W^X being broken during modules loading

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Message-ID: <20190307202521.GI26566@zn.tnic>
Date:   Thu, 7 Mar 2019 21:25:21 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Damian Tometzki <linux_dti@...oud.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux-MM <linux-mm@...ck.org>, Will Deacon <will.deacon@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        "Dock, Deneen T" <deneen.t.dock@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH v2 10/20] x86: avoid W^X being broken during modules
 loading

On Thu, Mar 07, 2019 at 12:02:13PM -0800, Andy Lutomirski wrote:
> Should we maybe rename these functions?  static_cpu_has() is at least
> reasonably obvious.  But cpu_feature_enabled() is different for
> reasons I've never understood, and boot_cpu_has() is IMO terribly
> named.  It's not about the boot cpu -- it's about doing the same thing
> but with less bloat and less performance.

Well, it does test bits in boot_cpu_data. I don't care about "boot" in
the name though so feel free to suggest something better.

> (And can we maybe collapse cpu_feature_enabled() and static_cpu_has()
> into the same function?)

I'm not sure it would be always ok to involve the DISABLED_MASK*
buildtime stuff in the checks. It probably is but it would need careful
auditing to be sure, first.

-- 
Regards/Gruss,
    Boris.

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