From: Russell King rmk+kernel@armlinux.org.uk
Commit 1d4238c56f9816ce0f9c8dbe42d7f2ad81cb6613 upstream.
Add an implementation of the array_index_mask_nospec() function for mitigating Spectre variant 1 throughout the kernel.
Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Acked-by: Mark Rutland mark.rutland@arm.com Boot-tested-by: Tony Lindgren tony@atomide.com Reviewed-by: Tony Lindgren tony@atomide.com Signed-off-by: David A. Long dave.long@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Ard Biesheuvel ardb@kernel.org --- arch/arm/include/asm/barrier.h | 21 ++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h index edd9e633a84b..8514b70704de 100644 --- a/arch/arm/include/asm/barrier.h +++ b/arch/arm/include/asm/barrier.h @@ -108,5 +108,26 @@ do { \ #define smp_mb__before_atomic() smp_mb() #define smp_mb__after_atomic() smp_mb()
+#ifdef CONFIG_CPU_SPECTRE +static inline unsigned long array_index_mask_nospec(unsigned long idx, + unsigned long sz) +{ + unsigned long mask; + + asm volatile( + "cmp %1, %2\n" + " sbc %0, %1, %1\n" + CSDB + : "=r" (mask) + : "r" (idx), "Ir" (sz) + : "cc"); + + return mask; +} +#define array_index_mask_nospec array_index_mask_nospec +#endif + +#include <asm-generic/barrier.h> + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_BARRIER_H */