/*
 *  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>

/*
 * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
 * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
 * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
 * means the userland is reading).
 */
#define UFFD_API ((__u64)0xAA)
#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |            \
                           UFFD_FEATURE_EVENT_REMAP |           \
                           UFFD_FEATURE_EVENT_REMOVE |  \
                           UFFD_FEATURE_EVENT_UNMAP |           \
                           UFFD_FEATURE_MISSING_HUGETLBFS |     \
                           UFFD_FEATURE_MISSING_SHMEM |         \
                           UFFD_FEATURE_SIGBUS |                \
                           UFFD_FEATURE_THREAD_ID)
#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)
#define UFFD_API_RANGE_IOCTLS_BASIC             \
        ((__u64)1 << _UFFDIO_WAKE |             \
         (__u64)1 << _UFFDIO_COPY)

/*
 * 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;
                        union {
                                __u32 ptid;
                        } feat;
                } pagefault;

                struct {
                        __u32   ufd;
                } fork;

                struct {
                        __u64   from;
                        __u64   to;
                        __u64   len;
                } remap;

                struct {
                        __u64   start;
                        __u64   end;
                } remove;

                struct {
                        /* unused reserved fields */
                        __u64   reserved1;
                        __u64   reserved2;
                        __u64   reserved3;
                } reserved;
        } arg;
} __attribute__((packed));

/*
 * Start at 0x12 and not at 0 to be more strict against bugs.
 */
#define UFFD_EVENT_PAGEFAULT    0x12
#define UFFD_EVENT_FORK         0x13
#define UFFD_EVENT_REMAP        0x14
#define UFFD_EVENT_REMOVE       0x15
#define UFFD_EVENT_UNMAP        0x16

/* 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.
         *
         * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
         * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
         * hugetlbfs virtual memory ranges. Adding or not adding
         * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
         * no real functional effect after UFFDIO_API returns, but
         * it's only useful for an initial feature set probe at
         * UFFDIO_API time. There are two ways to use it:
         *
         * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
         *    uffdio_api.features before calling UFFDIO_API, an error
         *    will be returned by UFFDIO_API on a kernel without
         *    hugetlbfs missing support
         *
         * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
         *    uffdio_api.features and instead it will be set by the
         *    kernel in the uffdio_api.features if the kernel supports
         *    it, so userland can later check if the feature flag is
         *    present in uffdio_api.features after UFFDIO_API
         *    succeeded.
         *
         * UFFD_FEATURE_MISSING_SHMEM works the same as
         * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
         * (i.e. tmpfs and other shmem based APIs).
         *
         * UFFD_FEATURE_SIGBUS feature means no page-fault
         * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
         * a SIGBUS signal will be sent to the faulting process.
         *
         * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
         * be returned, if feature is not requested 0 will be returned.
         */
#define UFFD_FEATURE_PAGEFAULT_FLAG_WP          (1<<0)
#define UFFD_FEATURE_EVENT_FORK                 (1<<1)
#define UFFD_FEATURE_EVENT_REMAP                (1<<2)
#define UFFD_FEATURE_EVENT_REMOVE               (1<<3)
#define UFFD_FEATURE_MISSING_HUGETLBFS          (1<<4)
#define UFFD_FEATURE_MISSING_SHMEM              (1<<5)
#define UFFD_FEATURE_EVENT_UNMAP                (1<<6)
#define UFFD_FEATURE_SIGBUS                     (1<<7)
#define UFFD_FEATURE_THREAD_ID                  (1<<8)
        __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 */