x86, smap: Add a header file with macros for STAC/CLAC
The STAC/CLAC instructions are only available with SMAP, but on the
other hand they aren't needed if SMAP is not available, or before we
start to run userspace, so construct them as alternatives which start
out as noops and are enabled by the alternatives mechanism.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1348256595-29119-7-git-send-email-hpa@linux.intel.com
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8ec3a1a..5ce8694 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1487,6 +1487,17 @@
If supported, this is a high bandwidth, cryptographically
secure hardware random number generator.
+config X86_SMAP
+ def_bool y
+ prompt "Supervisor Mode Access Prevention" if EXPERT
+ ---help---
+ Supervisor Mode Access Prevention (SMAP) is a security
+ feature in newer Intel processors. There is a small
+ performance cost if this enabled and turned on; there is
+ also a small increase in the kernel size if this is enabled.
+
+ If unsure, say Y.
+
config EFI
bool "EFI runtime service support"
depends on ACPI
