x86: Implement array_index_mask_nospec

[mirror_ubuntu-bionic-kernel.git] / arch / x86 / include / asm / barrier.h

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 7fb336210e1b26b09371483bfb6a6fe0014f8f3c..173b38f5fe88a5cb86276a509cf57a44ea477e58 100644 (file)
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -24,6 +24,30 @@
 #define wmb()  asm volatile("sfence" ::: "memory")
 #endif
 
+/**
+ * array_index_mask_nospec() - generate a mask that is ~0UL when the
+ *     bounds check succeeds and 0 otherwise
+ * @index: array element index
+ * @size: number of elements in array
+ *
+ * Returns:
+ *     0 - (index < size)
+ */
+static inline unsigned long array_index_mask_nospec(unsigned long index,
+               unsigned long size)
+{
+       unsigned long mask;
+
+       asm ("cmp %1,%2; sbb %0,%0;"
+                       :"=r" (mask)
+                       :"r"(size),"r" (index)
+                       :"cc");
+       return mask;
+}
+
+/* Override the default implementation from linux/nospec.h. */
+#define array_index_mask_nospec array_index_mask_nospec
+
 #ifdef CONFIG_X86_PPRO_FENCE
 #define dma_rmb()      rmb()
 #else