Date: Mon, 11 Feb 2019 11:09:25 -0800 From: Nadav Amit <nadav.amit@...il.com> To: Borislav Petkov <bp@...en8.de> 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 Feb 11, 2019, at 11:01 AM, Borislav Petkov <bp@...en8.de> wrote: > > 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. I fully agree, if that is the standard. It is just that I find the use of static_cpu_has()/boot_cpu_has() to be very inconsistent. I doubt that show_cpuinfo_misc(), copy_fpstate_to_sigframe(), or i915_memcpy_init_early() that use static_cpu_has() are any hotter than text_poke_early(). Anyhow, I’ll use boot_cpu_has() as you said.
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