---

yaml
---
r: 326235
b: refs/heads/master
c: 51ae4a2
h: refs/heads/master
i:
  326233: 573f6eb
  326231: a70bbe6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 76f30759f690db21ca567a20665ed2679ad3235b
+refs/heads/master: 51ae4a2d775e1ee456282d7c60e49693d0a8555d

trunk/arch/x86/Kconfig

@@ -1487,6 +1487,17 @@ config ARCH_RANDOM
 	  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

trunk/arch/x86/include/asm/smap.h

@@ -0,0 +1,91 @@
+/*
+ * Supervisor Mode Access Prevention support
+ *
+ * Copyright (C) 2012 Intel Corporation
+ * Author: H. Peter Anvin <hpa@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#ifndef _ASM_X86_SMAP_H
+#define _ASM_X86_SMAP_H
+
+#include <linux/stringify.h>
+#include <asm/nops.h>
+#include <asm/cpufeature.h>
+
+/* "Raw" instruction opcodes */
+#define __ASM_CLAC	.byte 0x0f,0x01,0xca
+#define __ASM_STAC	.byte 0x0f,0x01,0xcb
+
+#ifdef __ASSEMBLY__
+
+#include <asm/alternative-asm.h>
+
+#ifdef CONFIG_X86_SMAP
+
+#define ASM_CLAC							\
+	661: ASM_NOP3 ;							\
+	.pushsection .altinstr_replacement, "ax" ;			\
+	662: __ASM_CLAC ;						\
+	.popsection ;							\
+	.pushsection .altinstructions, "a" ;				\
+	altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ;	\
+	.popsection
+
+#define ASM_STAC							\
+	661: ASM_NOP3 ;							\
+	.pushsection .altinstr_replacement, "ax" ;			\
+	662: __ASM_STAC ;						\
+	.popsection ;							\
+	.pushsection .altinstructions, "a" ;				\
+	altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ;	\
+	.popsection
+
+#else /* CONFIG_X86_SMAP */
+
+#define ASM_CLAC
+#define ASM_STAC
+
+#endif /* CONFIG_X86_SMAP */
+
+#else /* __ASSEMBLY__ */
+
+#include <asm/alternative.h>
+
+#ifdef CONFIG_X86_SMAP
+
+static inline void clac(void)
+{
+	/* Note: a barrier is implicit in alternative() */
+	alternative(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
+}
+
+static inline void stac(void)
+{
+	/* Note: a barrier is implicit in alternative() */
+	alternative(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP);
+}
+
+/* These macros can be used in asm() statements */
+#define ASM_CLAC \
+	ALTERNATIVE(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
+#define ASM_STAC \
+	ALTERNATIVE(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP)
+
+#else /* CONFIG_X86_SMAP */
+
+static inline void clac(void) { }
+static inline void stac(void) { }
+
+#define ASM_CLAC
+#define ASM_STAC
+
+#endif /* CONFIG_X86_SMAP */
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_X86_SMAP_H */