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[4.9,17/24] ARM: spectre-v1: add array_index_mask_nospec() implementation

Message ID 20181031135713.2873-18-dave.long@linaro.org
State Superseded
Headers show
Series V4.9 backport of 32-bit arm spectre patches | expand

Commit Message

David Long Oct. 31, 2018, 1:57 p.m. UTC 
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(+)

-- 
2.17.1
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Patch

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__ */