x86/speculation: Fix up array_index_nospec_mask() asm constraint

commit be3233fbfcb8f5acb6e3bcd0895c3ef9e100d470 upstream.

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

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/151797010204.1289.1510000292250184993.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 8575903..78d1c6a 100644 (file)
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -39,7 +39,7 @@ 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;
 }