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-rw-r--r--arch/x86/Kconfig11
-rw-r--r--arch/x86/include/asm/smap.h91
2 files changed, 102 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8ec3a1aa4ab..5ce86941333 100644
--- a/arch/x86/Kconfig
+++ b/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
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
new file mode 100644
index 00000000000..3989c2492eb
--- /dev/null
+++ b/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 */