4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Boot-tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
Reviewed-by: Tony Lindgren <tony@xxxxxxxxxxx>
Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/barrier.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
--- 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__ */
