From owner-freebsd-hackers@FreeBSD.ORG Wed May 18 18:48:03 2011 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 64D691065672; Wed, 18 May 2011 18:48:03 +0000 (UTC) (envelope-from oliver.pntr@gmail.com) Received: from mail-wy0-f182.google.com (mail-wy0-f182.google.com [74.125.82.182]) by mx1.freebsd.org (Postfix) with ESMTP id C6E7D8FC17; Wed, 18 May 2011 18:48:02 +0000 (UTC) Received: by wyf23 with SMTP id 23so1930754wyf.13 for ; Wed, 18 May 2011 11:48:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=aqtG2oJ86j0x2nWX3gMyoFBr6QwnmMHejDbmWcE6wcg=; b=wqGuckbuV5g812JZXNRllE2X6bLyGz2Tdw1ZqJc228kK6eld1ImggwU28b04H3HZ8K 74d2yRdG/uJ4JyDZVteN45on7vWkAZTiBG2a3/3WJy4+EV/YdJZbKbl4JTkgQg1+ZawE 2aOIvDjzKQYvYVw6t/GAhiNuD55ibcMQ3GhQk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=ca2I9Ac+P0vUpT6hqmzwRAnC3aU/HohxB8bFPb6GgwvCdG6tvePjR0ymo6x2eOaO+O C2OF8F7OVFqNgccBlaKlOGzPjU4NzPGPgs2TJnYSzEiNNxwztvPU0lOt8C6j/f61X60c 6rzI3iM0fGd/RwNWfI8rUhW3O6QplAS3q6Mkw= MIME-Version: 1.0 Received: by 10.227.55.20 with SMTP id s20mr2238842wbg.15.1305744481136; Wed, 18 May 2011 11:48:01 -0700 (PDT) Received: by 10.227.209.209 with HTTP; Wed, 18 May 2011 11:48:01 -0700 (PDT) In-Reply-To: <20110518154007.GR48734@deviant.kiev.zoral.com.ua> References: <1305581685-5144-1-git-send-email-fenghua.yu@intel.com> <20110518010353.GQ48734@deviant.kiev.zoral.com.ua> <201105181050.30128.jhb@freebsd.org> <20110518154007.GR48734@deviant.kiev.zoral.com.ua> Date: Wed, 18 May 2011 20:48:01 +0200 Message-ID: From: Oliver Pinter To: Kostik Belousov Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-hackers@freebsd.org Subject: Re: Fwd: [PATCH v2 3/4] x86, head_32/64.S: Enable SMEP X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 May 2011 18:48:03 -0000 On 5/18/11, Kostik Belousov wrote: > On Wed, May 18, 2011 at 10:50:30AM -0400, John Baldwin wrote: >> On Wednesday, May 18, 2011 8:31:15 am Oliver Pinter wrote: >> > On 5/18/11, Kostik Belousov wrote: >> > > On Wed, May 18, 2011 at 02:03:07AM +0200, Oliver Pinter wrote: >> > >> ---------- Forwarded message ---------- >> > >> From: Fenghua Yu >> > >> Date: Mon, 16 May 2011 14:34:44 -0700 >> > >> Subject: [PATCH v2 3/4] x86, head_32/64.S: Enable SMEP >> > >> To: Ingo Molnar , Thomas Gleixner >> > >> , >> > >> H Peter Anvin , Asit K Mallick >> > >> , Linus Torvalds >> > >> , Avi Kivity , Arjan >> > >> van de Ven , Andrew Morton >> > >> , Andi Kleen >> > >> Cc: linux-kernel , Fenghua Yu >> > >> >> > >> >> > >> From: Fenghua Yu >> > >> >> > >> Enable newly documented SMEP (Supervisor Mode Execution Protection) >> > >> CPU >> > >> feature in kernel. >> > >> >> > >> SMEP prevents the CPU in kernel-mode to jump to an executable page >> > >> that >> > >> does >> > >> not have the kernel/system flag set in the pte. This prevents the >> > >> kernel >> > >> from executing user-space code accidentally or maliciously, so it for >> > >> example >> > >> prevents kernel exploits from jumping to specially prepared user-mode >> > >> shell >> > >> code. The violation will cause page fault #PF and will have error >> > >> code >> > >> identical to XD violation. >> > >> >> > >> CR4.SMEP (bit 20) is 0 at power-on. If the feature is supported by >> > >> CPU >> > >> (X86_FEATURE_SMEP), enable SMEP by setting CR4.SMEP. New kernel >> > >> option nosmep disables the feature even if the feature is supported >> > >> by >> > >> CPU. >> > >> >> > >> Signed-off-by: Fenghua Yu >> > > >> > > So, where is the mentioned documentation for SMEP ? Rev. 38 of the >> > > Intel(R) 64 and IA-32 Architectures Software Developer's Manual does >> > > not contain the description, at least at the places where I looked and >> > > expected to find it. >> > >> > http://www.intel.com/Assets/PDF/manual/325384.pdf >> > >> > Intel? 64 and IA-32 Architectures Software Developer?s Manual >> > Volume 3 (3A & 3B): >> > System Programming Guide >> >> Which revision? It is not documented in revision 38 from April 2011. >> >> I just downloaded that link, and it is still revision 38 and has no >> mention no, under the original intel link i find rev.39 Order Number: 325384-039US May 2011 uploaded here: http://oliverp.teteny.bme.hu/up/325384.pdf >> 'SMEP'. Also, bit 20 of CR4 is still marked as Reserved in that manual >> (section 2.5). > This is exactly what I said about rev. 38 in my original reply. >