From 7a633b2249a83678ebe58bfffc47dbd2b1bddb8b Mon Sep 17 00:00:00 2001 From: Russell King Date: Fri, 11 May 2018 15:06:58 +0100 Subject: [PATCH] UPSTREAM: ARM: spectre-v1: add array_index_mask_nospec() implementation Add an implementation of the array_index_mask_nospec() function for mitigating Spectre variant 1 throughout the kernel. Signed-off-by: Russell King Acked-by: Mark Rutland Boot-tested-by: Tony Lindgren Reviewed-by: Tony Lindgren (cherry picked from commit 1d4238c56f9816ce0f9c8dbe42d7f2ad81cb6613) Change-Id: I69fc8c673578a937a06cfdf85ae73492d25d069f --- 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 d705be47a1ad..85eb7ef44a18 100644 --- a/arch/arm/include/asm/barrier.h +++ b/arch/arm/include/asm/barrier.h @@ -106,5 +106,24 @@ 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 + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_BARRIER_H */