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

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Message-ID: <20190211190108.GP19618@zn.tnic>
Date:   Mon, 11 Feb 2019 20:01:08 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        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 Mon, Feb 11, 2019 at 10:45:26AM -0800, Nadav Amit wrote:
> Are you sure about that? This path is still used when modules are loaded.

Yes, I'm sure. Loading a module does a gazillion things so saving a
couple of insns - yes, boot_cpu_has() is usually a RIP-relative MOV and a
TEST - doesn't show even as a blip on any radar.

-- 
Regards/Gruss,
    Boris.

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