2 files changed, 18 insertions, 10 deletions

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 11b92b047a1e..79002bca1f43 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -52,6 +52,9 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
         return vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP);
 }
 
+extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
+extern void dup_userfaultfd_complete(struct list_head *);
+
 #else /* CONFIG_USERFAULTFD */
 
 /* mm helpers */
@@ -76,6 +79,16 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
         return false;
 }
 
+static inline int dup_userfaultfd(struct vm_area_struct *vma,
+                                  struct list_head *l)
+{
+        return 0;
+}
+
+static inline void dup_userfaultfd_complete(struct list_head *l)
+{
+}
+
 #endif /* CONFIG_USERFAULTFD */
 
 #endif /* _LINUX_USERFAULTFD_K_H */
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 94046b8aa6ad..c8953c84fdcc 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -18,12 +18,7 @@
  * means the userland is reading).
  */
 #define UFFD_API ((__u64)0xAA)
-/*
- * After implementing the respective features it will become:
- * #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \
- *                            UFFD_FEATURE_EVENT_FORK)
- */
-#define UFFD_API_FEATURES (0)
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK)
 #define UFFD_API_IOCTLS                         \
         ((__u64)1 << _UFFDIO_REGISTER |         \
          (__u64)1 << _UFFDIO_UNREGISTER |       \
@@ -78,6 +73,10 @@ struct uffd_msg {
                 } pagefault;
 
                 struct {
+                        __u32   ufd;
+                } fork;
+
+                struct {
                         /* unused reserved fields */
                         __u64   reserved1;
                         __u64   reserved2;
@@ -90,9 +89,7 @@ struct uffd_msg {
  * Start at 0x12 and not at 0 to be more strict against bugs.
  */
 #define UFFD_EVENT_PAGEFAULT    0x12
-#if 0 /* not available yet */
 #define UFFD_EVENT_FORK         0x13
-#endif
 
 /* flags for UFFD_EVENT_PAGEFAULT */
 #define UFFD_PAGEFAULT_FLAG_WRITE       (1<<0)  /* If this was a write fault */
@@ -111,10 +108,8 @@ struct uffdio_api {
          * are to be considered implicitly always enabled in all kernels as
          * long as the uffdio_api.api requested matches UFFD_API.
          */
-#if 0 /* not available yet */
 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP          (1<<0)
 #define UFFD_FEATURE_EVENT_FORK                 (1<<1)
-#endif
         __u64 features;
 
         __u64 ioctls;