[PATCH 2/3] ARM: spectre-v1: add array_index_mask_nospec() implementation
From: Russell King <hidden>
Date: 2018-05-31 13:31:17
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Add an implementation of the array_index_mask_nospec() function for mitigating Spectre variant 1 throughout the kernel. Signed-off-by: Russell King <redacted> --- arch/arm/include/asm/barrier.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h
index 3d9c1d4b7e75..a89adcf53b99 100644
--- a/arch/arm/include/asm/barrier.h
+++ b/arch/arm/include/asm/barrier.h@@ -76,6 +76,24 @@ 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( "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__ */
--
2.7.4