new file mode 100644
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+/*
+ * 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
+
+#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 | \
+ (__u64)1 << _UFFDIO_COPY | \
+ (__u64)1 << _UFFDIO_ZEROPAGE | \
+ (__u64)1 << _UFFDIO_REMAP)
+
+/*
+ * 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_COPY (0x03)
+#define _UFFDIO_ZEROPAGE (0x04)
+#define _UFFDIO_REMAP (0x05)
+#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)
+#define UFFDIO_COPY _IOWR(UFFDIO, _UFFDIO_COPY, \
+ struct uffdio_copy)
+#define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \
+ struct uffdio_zeropage)
+#define UFFDIO_REMAP _IOWR(UFFDIO, _UFFDIO_REMAP, \
+ struct uffdio_remap)
+
+/*
+ * 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;
+};
+
+struct uffdio_copy {
+ __u64 dst;
+ __u64 src;
+ __u64 len;
+ /*
+ * There will be a wrprotection flag later that allows to map
+ * pages wrprotected on the fly. And such a flag will be
+ * available if the wrprotection ioctl are implemented for the
+ * range according to the uffdio_register.ioctls.
+ */
+#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0)
+ __u64 mode;
+
+ /*
+ * "copy" and "wake" are written by the ioctl and must be at
+ * the end: the copy_from_user will not read the last 16
+ * bytes.
+ */
+ __s64 copy;
+ __s64 wake;
+};
+
+struct uffdio_zeropage {
+ struct uffdio_range range;
+#define UFFDIO_ZEROPAGE_MODE_DONTWAKE ((__u64)1<<0)
+ __u64 mode;
+
+ /*
+ * "zeropage" and "wake" are written by the ioctl and must be
+ * at the end: the copy_from_user will not read the last 16
+ * bytes.
+ */
+ __s64 zeropage;
+ __s64 wake;
+};
+
+struct uffdio_remap {
+ __u64 dst;
+ __u64 src;
+ __u64 len;
+ /*
+ * Especially if used to atomically remove memory from the
+ * address space the wake on the dst range is not needed.
+ */
+#define UFFDIO_REMAP_MODE_DONTWAKE ((__u64)1<<0)
+#define UFFDIO_REMAP_MODE_ALLOW_SRC_HOLES ((__u64)1<<1)
+ __u64 mode;
+
+ /*
+ * "remap" and "wake" are written by the ioctl and must be at
+ * the end: the copy_from_user will not read the last 16
+ * bytes.
+ */
+ __s64 remap;
+ __s64 wake;
+};
+
+#endif /* _LINUX_USERFAULTFD_H */