On Wed, May 18, 2011 at 02:03:07AM +0200, Oliver Pinter wrote: > ---------- Forwarded message ---------- > From: Fenghua Yu <fenghua...@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 <mi...@elte.hu>, Thomas Gleixner <t...@linutronix.de>, > H Peter Anvin <h...@zytor.com>, Asit K Mallick > <asit.k.mall...@intel.com>, Linus Torvalds > <torva...@linux-foundation.org>, Avi Kivity <a...@redhat.com>, Arjan > van de Ven <ar...@infradead.org>, Andrew Morton > <a...@linux-foundation.org>, Andi Kleen <a...@firstfloor.org> > Cc: linux-kernel <linux-ker...@vger.kernel.org>, Fenghua Yu > <fenghua...@intel.com> > > From: Fenghua Yu <fenghua...@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...@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. Looking forward to hear from you.
pgpYcKGUj9rIq.pgp
Description: PGP signature
