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 --- arch/arm/include/asm/barrier.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h index 6f00dac6ad8e..513e03d138ea 100644 --- a/arch/arm/include/asm/barrier.h +++ b/arch/arm/include/asm/barrier.h @@ -75,6 +75,25 @@ extern void arm_heavy_mb(void); #define __smp_rmb() __smp_mb() #define __smp_wmb() dmb(ishst)
+#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__ */