[Qemu-devel] [PATCH 03/23] userfaultfd: uAPI

[Andrea Arcangeli]

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

Signed-off-by: Andrea Arcangeli <address@hidden>
---
 Documentation/ioctl/ioctl-number.txt |  1 +
 include/uapi/linux/Kbuild            |  1 +
 include/uapi/linux/userfaultfd.h     | 81 ++++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+)
 create mode 100644 include/uapi/linux/userfaultfd.h

diff --git a/Documentation/ioctl/ioctl-number.txt 
b/Documentation/ioctl/ioctl-number.txt
index ec7c81b..ed950ad 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -302,6 +302,7 @@ Code  Seq#(hex)     Include File            Comments
 0xA3   80-8F   Port ACL                in development:
                                        <mailto:address@hidden>
 0xA3   90-9F   linux/dtlk.h
+0xAA   00-3F   linux/uapi/linux/userfaultfd.h
 0xAB   00-1F   linux/nbd.h
 0xAC   00-1F   linux/raw.h
 0xAD   00      Netfilter device        in development:
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index 4842a98..47547ea 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -452,3 +452,4 @@ 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 0000000..9a8cd56
--- /dev/null
+++ b/include/uapi/linux/userfaultfd.h
@@ -0,0 +1,81 @@
+/*
+ *  include/linux/userfaultfd.h
+ *
+ *  Copyright (C) 2007  Davide Libenzi <address@hidden>
+ *  Copyright (C) 2015  Red Hat, Inc.
+ *
+ */
+
+#ifndef _LINUX_USERFAULTFD_H
+#define _LINUX_USERFAULTFD_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 */