userfaultfd: uAPI

Defines the uAPI of the userfaultfd, notably the ioctl numbers and protocol.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 84 insertions, 0 deletions

diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index aafb9937b162..70ff1d9abf0d 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -456,3 +456,4 @@ header-y += xfrm.h
 header-y += xilinx-v4l2-controls.h
 header-y += zorro.h
 header-y += zorro_ids.h
+header-y += userfaultfd.h
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
new file mode 100644
index 000000000000..09c2e2a8c9d6
--- /dev/null
+++ b/include/uapi/linux/userfaultfd.h
@@ -0,0 +1,83 @@
+/*
+ *  include/linux/userfaultfd.h
+ *
+ *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
+ *  Copyright (C) 2015  Red Hat, Inc.
+ *
+ */
+
+#ifndef _LINUX_USERFAULTFD_H
+#define _LINUX_USERFAULTFD_H
+
+#include <linux/types.h>
+
+#define UFFD_API ((__u64)0xAA)
+/* FIXME: add "|UFFD_BIT_WP" to UFFD_API_BITS after implementing it */
+#define UFFD_API_BITS (UFFD_BIT_WRITE)
+#define UFFD_API_IOCTLS                         \
+        ((__u64)1 << _UFFDIO_REGISTER |         \
+         (__u64)1 << _UFFDIO_UNREGISTER |       \
+         (__u64)1 << _UFFDIO_API)
+#define UFFD_API_RANGE_IOCTLS                   \
+        ((__u64)1 << _UFFDIO_WAKE)
+
+/*
+ * Valid ioctl command number range with this API is from 0x00 to
+ * 0x3F.  UFFDIO_API is the fixed number, everything else can be
+ * changed by implementing a different UFFD_API. If sticking to the
+ * same UFFD_API more ioctl can be added and userland will be aware of
+ * which ioctl the running kernel implements through the ioctl command
+ * bitmask written by the UFFDIO_API.
+ */
+#define _UFFDIO_REGISTER                (0x00)
+#define _UFFDIO_UNREGISTER              (0x01)
+#define _UFFDIO_WAKE                    (0x02)
+#define _UFFDIO_API                     (0x3F)
+
+/* userfaultfd ioctl ids */
+#define UFFDIO 0xAA
+#define UFFDIO_API              _IOWR(UFFDIO, _UFFDIO_API,      \
+                                      struct uffdio_api)
+#define UFFDIO_REGISTER         _IOWR(UFFDIO, _UFFDIO_REGISTER, \
+                                      struct uffdio_register)
+#define UFFDIO_UNREGISTER       _IOR(UFFDIO, _UFFDIO_UNREGISTER,        \
+                                     struct uffdio_range)
+#define UFFDIO_WAKE             _IOR(UFFDIO, _UFFDIO_WAKE,      \
+                                     struct uffdio_range)
+
+/*
+ * Valid bits below PAGE_SHIFT in the userfault address read through
+ * the read() syscall.
+ */
+#define UFFD_BIT_WRITE  (1<<0)  /* this was a write fault, MISSING or WP */
+#define UFFD_BIT_WP     (1<<1)  /* handle_userfault() reason VM_UFFD_WP */
+#define UFFD_BITS       2       /* two above bits used for UFFD_BIT_* mask */
+
+struct uffdio_api {
+        /* userland asks for an API number */
+        __u64 api;
+
+        /* kernel answers below with the available features for the API */
+        __u64 bits;
+        __u64 ioctls;
+};
+
+struct uffdio_range {
+        __u64 start;
+        __u64 len;
+};
+
+struct uffdio_register {
+        struct uffdio_range range;
+#define UFFDIO_REGISTER_MODE_MISSING    ((__u64)1<<0)
+#define UFFDIO_REGISTER_MODE_WP         ((__u64)1<<1)
+        __u64 mode;
+
+        /*
+         * kernel answers which ioctl commands are available for the
+         * range, keep at the end as the last 8 bytes aren't read.
+         */
+        __u64 ioctls;
+};
+
+#endif /* _LINUX_USERFAULTFD_H */