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Date: Tue, 10 Nov 2009 12:25:39 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Kees Cook <kees.cook@...onical.com> CC: Arjan van de Ven <arjan@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, x86@...nel.org, Pekka Enberg <penberg@...helsinki.fi>, Jan Beulich <jbeulich@...ell.com>, Vegard Nossum <vegardno@....uio.no>, Yinghai Lu <yinghai@...nel.org>, Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4] [x86] detect and report lack of NX protections The more I stare at the underlying code, the more I'm convinced that the fundamental problem is that the underlying code is insane, with multiple levels of detection for what amounts to cpu_has_nx, each effectively checking what the previous code has done. check_efer(), for example, screws with EFER, but EFER is simply set in head_64.S from CPUID (unless Xen does something insane -- but if so, Xen should clear X86_FEATURE_NX instead.) The 32-bit startup code also sets NX, but yet on 32 bits we wiggle EFER as if it had never been. This code is screaming for cleanup and unification. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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