[PATCH] s390: add ptr_to_compat()

Add ptr_to_compat() to s390 - needed by the new robust-futex code.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>

untested. CHECKME: am i right about the 0x7fffffffUL masking?
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

include/asm-s390/compat.h

@@ -128,6 +128,11 @@ static inline void __user *compat_ptr(compat_uptr_t uptr)
 	return (void __user *)(unsigned long)(uptr & 0x7fffffffUL);
 }
 
+static inline compat_uptr_t ptr_to_compat(void __user *uptr)
+{
+	return (u32)(unsigned long)uptr;
+}
+
 static inline void __user *compat_alloc_user_space(long len)
 {
 	unsigned long stack;