Date: Wed, 18 May 2011 14:31:15 +0200 From: Oliver Pinter <oliver.pntr@gmail.com> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Fwd: [PATCH v2 3/4] x86, head_32/64.S: Enable SMEP Message-ID: <BANLkTimHmZCO9couAxsW1rf81Qm2FAHrZw@mail.gmail.com> In-Reply-To: <20110518010353.GQ48734@deviant.kiev.zoral.com.ua> References: <1305581685-5144-1-git-send-email-fenghua.yu@intel.com> <1305581685-5144-4-git-send-email-fenghua.yu@intel.com> <BANLkTi=ij7n8qiZ=n7mtUB5uZP-T6S1uRw@mail.gmail.com> <20110518010353.GQ48734@deviant.kiev.zoral.com.ua>
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On 5/18/11, Kostik Belousov <kostikbel@gmail.com> wrote: > On Wed, May 18, 2011 at 02:03:07AM +0200, Oliver Pinter wrote: >> ---------- Forwarded message ---------- >> From: Fenghua Yu <fenghua.yu@intel.com> >> Date: Mon, 16 May 2011 14:34:44 -0700 >> Subject: [PATCH v2 3/4] x86, head_32/64.S: Enable SMEP >> To: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>, >> H Peter Anvin <hpa@zytor.com>, Asit K Mallick >> <asit.k.mallick@intel.com>, Linus Torvalds >> <torvalds@linux-foundation.org>, Avi Kivity <avi@redhat.com>, Arjan >> van de Ven <arjan@infradead.org>, Andrew Morton >> <akpm@linux-foundation.org>, Andi Kleen <andi@firstfloor.org> >> Cc: linux-kernel <linux-kernel@vger.kernel.org>, Fenghua Yu >> <fenghua.yu@intel.com> >> >> From: Fenghua Yu <fenghua.yu@intel.com> >> >> 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 <fenghua.yu@intel.com> > > 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=AE 64 and IA-32 Architectures Software Developer=92s Manual Volume 3 (3A & 3B): System Programming Guide > > Looking forward to hear from you. > >
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