1 files changed, 27 insertions, 1 deletions

diff --git a/include/asm-powerpc/futex.h b/include/asm-powerpc/futex.h
index f1b3c00bc1ce..936422e54891 100644
--- a/include/asm-powerpc/futex.h
+++ b/include/asm-powerpc/futex.h
@@ -84,7 +84,33 @@ static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 static inline int
 futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
-        return -ENOSYS;
+        int prev;
+
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+                return -EFAULT;
+
+        __asm__ __volatile__ (
+        LWSYNC_ON_SMP
+"1:     lwarx   %0,0,%2         # futex_atomic_cmpxchg_inatomic\n\
+        cmpw    0,%0,%3\n\
+        bne-    3f\n"
+        PPC405_ERR77(0,%2)
+"2:     stwcx.  %4,0,%2\n\
+        bne-    1b\n"
+        ISYNC_ON_SMP
+"3:     .section .fixup,\"ax\"\n\
+4:      li      %0,%5\n\
+        b       3b\n\
+        .previous\n\
+        .section __ex_table,\"a\"\n\
+        .align 3\n\
+        " PPC_LONG "1b,4b,2b,4b\n\
+        .previous" \
+        : "=&r" (prev), "+m" (*uaddr)
+        : "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT)
+        : "cc", "memory");
+
+        return prev;
 }
 
 #endif /* __KERNEL__ */