x86/speculation: Fix up array_index_nospec_mask() asm constraint

Allow the compiler to handle @size as an immediate value or memory
directly rather than allocating a register.

Reported-by: Linus Torvalds <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/151797010204.1289.1510000292250184993.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 30d40614601641b9fc2dbd5ce734ff86d0cdd731..e1259f043ae999fa21e1f998431ab12cd73a11ea 100644 (file)
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -40,7 +40,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
 
        asm ("cmp %1,%2; sbb %0,%0;"
                        :"=r" (mask)
-                       :"r"(size),"r" (index)
+                       :"g"(size),"r" (index)
                        :"cc");
        return mask;
 }