diff -u linux-2.6.32.16/arch/x86/include/asm/uaccess.h linux-2.6.32.16-new/arch/x86/include/asm/uaccess.h
--- linux-2.6.32.16/arch/x86/include/asm/uaccess.h	2010-07-09 14:50:35.000000000 -0400
+++ linux-2.6.32.16-new/arch/x86/include/asm/uaccess.h	2010-07-11 20:46:01.000000000 -0400
@@ -213,9 +213,18 @@
 	__ret_gu;							\
 })
 
+#if defined(CONFIG_X86_64) && defined(CONFIG_PAX_MEMORY_UDEREF)
+#define __put_user_x(size, x, ptr, __ret_pu)				\
+	({								\
+		int __dummy;						\
+		asm volatile("call __put_user_" #size : "=a" (__ret_pu), "=c" (__dummy)	\
+			     : "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx", "ecx"); \
+	})
+#else
 #define __put_user_x(size, x, ptr, __ret_pu)			\
 	asm volatile("call __put_user_" #size : "=a" (__ret_pu)	\
 		     : "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
+#endif
 
 #ifdef CONFIG_X86_32
 #define _ASM_LOAD_USER_DS(ds) "movw %w" #ds ",%%ds\n"