x86, asmlinkage, paravirt: Make paravirt thunks global

The paravirt thunks use a hack of using a static reference to a static
function to reference that function from the top level statement.

This assumes that gcc always generates static function names in a specific
format, which is not necessarily true.

Simply make these functions global and asmlinkage or __visible. This way the
static __used variables are not needed and everything works.

Functions with arguments are __visible to keep the register calling
convention on 32bit.

Changed in paravirt and in all users (Xen and vsmp)

v2: Use __visible for functions with arguments

Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ido Yariv <ido@wizery.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1382458079-24450-5-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/paravirt.h

@@ -781,9 +781,9 @@ static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock,
  */
 #define PV_CALLEE_SAVE_REGS_THUNK(func)					\
 	extern typeof(func) __raw_callee_save_##func;			\
-	static void *__##func##__ __used = func;			\
 									\
 	asm(".pushsection .text;"					\
+	    ".globl __raw_callee_save_" #func " ; "			\
 	    "__raw_callee_save_" #func ": "				\
 	    PV_SAVE_ALL_CALLER_REGS					\
 	    "call " #func ";"						\