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
+
+#include <linux/types.h>
+
+#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_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)
+
+/*
+ * 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_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)
+
+/* read() structure */
+struct uffd_msg {
+ __u8 event;
+
+ __u8 reserved1;
+ __u16 reserved2;
+ __u32 reserved3;
+
+ union {
+ struct {
+ __u64 flags;
+ __u64 address;
+ } pagefault;
+
+ struct {
+ /* unused reserved fields */
+ __u64 reserved1;
+ __u64 reserved2;
+ __u64 reserved3;
+ } reserved;
+ } arg;
+} __packed;
+
+/*
+ * 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 */
+#define UFFD_PAGEFAULT_FLAG_WP (1<<1) /* If reason is VM_UFFD_WP */
+
+struct uffdio_api {
+ /* userland asks for an API number and the features to enable */
+ __u64 api;
+ /*
+ * Kernel answers below with the all available features for
+ * the API, this notifies userland of which events and/or
+ * which flags for each event are enabled in the current
+ * kernel.
+ *
+ * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
+ * 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;
+};
+
+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" is written by the ioctl and must be at the end: the
+ * copy_from_user will not read the last 8 bytes.
+ */
+ __s64 copy;
+};
+
+struct uffdio_zeropage {
+ struct uffdio_range range;
+#define UFFDIO_ZEROPAGE_MODE_DONTWAKE ((__u64)1<<0)
+ __u64 mode;
+
+ /*
+ * "zeropage" is written by the ioctl and must be at the end:
+ * the copy_from_user will not read the last 8 bytes.
+ */
+ __s64 zeropage;
+};
+
+#endif /* _LINUX_USERFAULTFD_H */