From 51ae4a2d775e1ee456282d7c60e49693d0a8555d Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 21 Sep 2012 12:43:10 -0700 Subject: [PATCH] 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 Link: http://lkml.kernel.org/r/1348256595-29119-7-git-send-email-hpa@linux.intel.com --- arch/x86/Kconfig | 11 +++++ arch/x86/include/asm/smap.h | 91 +++++++++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+) create mode 100644 arch/x86/include/asm/smap.h diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 8ec3a1aa4abd..5ce86941333f 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 000000000000..3989c2492eb5 --- /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 + * + * 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 +#include +#include + +/* "Raw" instruction opcodes */ +#define __ASM_CLAC .byte 0x0f,0x01,0xca +#define __ASM_STAC .byte 0x0f,0x01,0xcb + +#ifdef __ASSEMBLY__ + +#include + +#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 + +#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 */ -- GitLab