/*
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* Supervisor Mode Access Prevention support
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*
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* Copyright (C) 2012 Intel Corporation
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* Author: H. Peter Anvin <hpa@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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#ifndef _ASM_X86_SMAP_H
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#define _ASM_X86_SMAP_H
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#include <linux/stringify.h>
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#include <asm/nops.h>
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#include <asm/cpufeatures.h>
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/* "Raw" instruction opcodes */
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#define __ASM_CLAC .byte 0x0f,0x01,0xca
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#define __ASM_STAC .byte 0x0f,0x01,0xcb
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#ifdef __ASSEMBLY__
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#include <asm/alternative-asm.h>
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#ifdef CONFIG_X86_SMAP
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#define ASM_CLAC \
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ALTERNATIVE "", __stringify(__ASM_CLAC), X86_FEATURE_SMAP
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#define ASM_STAC \
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ALTERNATIVE "", __stringify(__ASM_STAC), X86_FEATURE_SMAP
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#else /* CONFIG_X86_SMAP */
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#define ASM_CLAC
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#define ASM_STAC
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#endif /* CONFIG_X86_SMAP */
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#else /* __ASSEMBLY__ */
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#include <asm/alternative.h>
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#ifdef CONFIG_X86_SMAP
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static __always_inline void clac(void)
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{
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/* Note: a barrier is implicit in alternative() */
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alternative("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
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}
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static __always_inline void stac(void)
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{
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/* Note: a barrier is implicit in alternative() */
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alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
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}
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static __always_inline unsigned long smap_save(void)
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{
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unsigned long flags;
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asm volatile (ALTERNATIVE("", "pushf; pop %0; " __stringify(__ASM_CLAC),
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X86_FEATURE_SMAP)
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: "=rm" (flags) : : "memory", "cc");
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return flags;
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}
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static __always_inline void smap_restore(unsigned long flags)
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{
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asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP)
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: : "g" (flags) : "memory", "cc");
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}
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/* These macros can be used in asm() statements */
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#define ASM_CLAC \
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ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
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#define ASM_STAC \
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ALTERNATIVE("", __stringify(__ASM_STAC), X86_FEATURE_SMAP)
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#else /* CONFIG_X86_SMAP */
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static inline void clac(void) { }
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static inline void stac(void) { }
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static inline unsigned long smap_save(void) { return 0; }
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static inline void smap_restore(unsigned long flags) { }
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#define ASM_CLAC
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#define ASM_STAC
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#endif /* CONFIG_X86_SMAP */
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_SMAP_H */
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