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x86: use alternative mechanism to define CLAC/STAC
This patch use alternative mechanism to define CLAC/STAC. Signed-off-by: Feng Wu <feng.wu@intel.com> Reviewed-by: Andrew Cooper <andrew.cooper@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
This commit is contained in:
Feng Wu authored and 
Jan Beulich committed
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5542ac7f90
commit
b5b60656bf
1 file changed
+13
-10
@@ -10,6 +10,7 @@
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#include <asm/percpu.h>
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#include <xen/stringify.h>
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#include <asm/cpufeature.h>
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#include <asm/alternative.h>
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#ifndef __ASSEMBLY__
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void ret_from_intr(void);
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@@ -166,26 +167,28 @@ void ret_from_intr(void);
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#define __ASM_STAC .byte 0x0f,0x01,0xcb
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#ifdef __ASSEMBLY__
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#define ASM_AC(op) \
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btl $X86_FEATURE_SMAP & 31, \
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CPUINFO_FEATURE_OFFSET(X86_FEATURE_SMAP)+boot_cpu_data(%rip); \
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jnc 881f; \
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__ASM_##op; \
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881:
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#define ASM_AC(op) \
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661: ASM_NOP3; \
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.pushsection .altinstr_replacement, "ax"; \
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662: __ASM_##op; \
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.popsection; \
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.pushsection .altinstructions, "a"; \
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altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3; \
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.popsection
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#define ASM_STAC ASM_AC(STAC)
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#define ASM_CLAC ASM_AC(CLAC)
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#else
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static inline void clac(void)
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{
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if ( boot_cpu_has(X86_FEATURE_SMAP) )
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asm volatile (__stringify(__ASM_CLAC) : : : "memory");
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/* Note: a barrier is implicit in alternative() */
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alternative(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
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}
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static inline void stac(void)
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{
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if ( boot_cpu_has(X86_FEATURE_SMAP) )
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asm volatile (__stringify(__ASM_STAC) : : : "memory");
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/* Note: a barrier is implicit in alternative() */
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alternative(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP);
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}
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#endif
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