linux-headers/linux/userfaultfd.h

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 /*
   3  *  include/linux/userfaultfd.h
   4  *
   5  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
   6  *  Copyright (C) 2015  Red Hat, Inc.
   7  *
   8  */
   9
  10 #ifndef _LINUX_USERFAULTFD_H
  11 #define _LINUX_USERFAULTFD_H
  12
  13 #include <linux/types.h>
  14
  15 /*
  16  * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
  17  * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
  18  * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
  19  * means the userland is reading).
  20  */
  21 #define UFFD_API ((__u64)0xAA)
  22 #define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |            \
  23                            UFFD_FEATURE_EVENT_REMAP |           \
  24                            UFFD_FEATURE_EVENT_REMOVE |  \
  25                            UFFD_FEATURE_EVENT_UNMAP |           \
  26                            UFFD_FEATURE_MISSING_HUGETLBFS |     \
  27                            UFFD_FEATURE_MISSING_SHMEM |         \
  28                            UFFD_FEATURE_SIGBUS |                \
  29                            UFFD_FEATURE_THREAD_ID)
  30 #define UFFD_API_IOCTLS                         \
  31         ((__u64)1 << _UFFDIO_REGISTER |         \
  32          (__u64)1 << _UFFDIO_UNREGISTER |       \
  33          (__u64)1 << _UFFDIO_API)
  34 #define UFFD_API_RANGE_IOCTLS                   \
  35         ((__u64)1 << _UFFDIO_WAKE |             \
  36          (__u64)1 << _UFFDIO_COPY |             \
  37          (__u64)1 << _UFFDIO_ZEROPAGE)
  38 #define UFFD_API_RANGE_IOCTLS_BASIC             \
  39         ((__u64)1 << _UFFDIO_WAKE |             \
  40          (__u64)1 << _UFFDIO_COPY)
  41
  42 /*
  43  * Valid ioctl command number range with this API is from 0x00 to
  44  * 0x3F.  UFFDIO_API is the fixed number, everything else can be
  45  * changed by implementing a different UFFD_API. If sticking to the
  46  * same UFFD_API more ioctl can be added and userland will be aware of
  47  * which ioctl the running kernel implements through the ioctl command
  48  * bitmask written by the UFFDIO_API.
  49  */
  50 #define _UFFDIO_REGISTER                (0x00)
  51 #define _UFFDIO_UNREGISTER              (0x01)
  52 #define _UFFDIO_WAKE                    (0x02)
  53 #define _UFFDIO_COPY                    (0x03)
  54 #define _UFFDIO_ZEROPAGE                (0x04)
  55 #define _UFFDIO_API                     (0x3F)
  56
  57 /* userfaultfd ioctl ids */
  58 #define UFFDIO 0xAA
  59 #define UFFDIO_API              _IOWR(UFFDIO, _UFFDIO_API,      \
  60                                       struct uffdio_api)
  61 #define UFFDIO_REGISTER         _IOWR(UFFDIO, _UFFDIO_REGISTER, \
  62                                       struct uffdio_register)
  63 #define UFFDIO_UNREGISTER       _IOR(UFFDIO, _UFFDIO_UNREGISTER,        \
  64                                      struct uffdio_range)
  65 #define UFFDIO_WAKE             _IOR(UFFDIO, _UFFDIO_WAKE,      \
  66                                      struct uffdio_range)
  67 #define UFFDIO_COPY             _IOWR(UFFDIO, _UFFDIO_COPY,     \
  68                                       struct uffdio_copy)
  69 #define UFFDIO_ZEROPAGE         _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \
  70                                       struct uffdio_zeropage)
  71
  72 /* read() structure */
  73 struct uffd_msg {
  74         __u8    event;
  75
  76         __u8    reserved1;
  77         __u16   reserved2;
  78         __u32   reserved3;
  79
  80         union {
  81                 struct {
  82                         __u64   flags;
  83                         __u64   address;
  84                         union {
  85                                 __u32 ptid;
  86                         } feat;
  87                 } pagefault;
  88
  89                 struct {
  90                         __u32   ufd;
  91                 } fork;
  92
  93                 struct {
  94                         __u64   from;
  95                         __u64   to;
  96                         __u64   len;
  97                 } remap;
  98
  99                 struct {
 100                         __u64   start;
 101                         __u64   end;
 102                 } remove;
 103
 104                 struct {
 105                         /* unused reserved fields */
 106                         __u64   reserved1;
 107                         __u64   reserved2;
 108                         __u64   reserved3;
 109                 } reserved;
 110         } arg;
 111 } __attribute__((packed));
 112
 113 /*
 114  * Start at 0x12 and not at 0 to be more strict against bugs.
 115  */
 116 #define UFFD_EVENT_PAGEFAULT    0x12
 117 #define UFFD_EVENT_FORK         0x13
 118 #define UFFD_EVENT_REMAP        0x14
 119 #define UFFD_EVENT_REMOVE       0x15
 120 #define UFFD_EVENT_UNMAP        0x16
 121
 122 /* flags for UFFD_EVENT_PAGEFAULT */
 123 #define UFFD_PAGEFAULT_FLAG_WRITE       (1<<0)  /* If this was a write fault */
 124 #define UFFD_PAGEFAULT_FLAG_WP          (1<<1)  /* If reason is VM_UFFD_WP */
 125
 126 struct uffdio_api {
 127         /* userland asks for an API number and the features to enable */
 128         __u64 api;
 129         /*
 130          * Kernel answers below with the all available features for
 131          * the API, this notifies userland of which events and/or
 132          * which flags for each event are enabled in the current
 133          * kernel.
 134          *
 135          * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
 136          * are to be considered implicitly always enabled in all kernels as
 137          * long as the uffdio_api.api requested matches UFFD_API.
 138          *
 139          * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
 140          * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
 141          * hugetlbfs virtual memory ranges. Adding or not adding
 142          * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
 143          * no real functional effect after UFFDIO_API returns, but
 144          * it's only useful for an initial feature set probe at
 145          * UFFDIO_API time. There are two ways to use it:
 146          *
 147          * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
 148          *    uffdio_api.features before calling UFFDIO_API, an error
 149          *    will be returned by UFFDIO_API on a kernel without
 150          *    hugetlbfs missing support
 151          *
 152          * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
 153          *    uffdio_api.features and instead it will be set by the
 154          *    kernel in the uffdio_api.features if the kernel supports
 155          *    it, so userland can later check if the feature flag is
 156          *    present in uffdio_api.features after UFFDIO_API
 157          *    succeeded.
 158          *
 159          * UFFD_FEATURE_MISSING_SHMEM works the same as
 160          * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
 161          * (i.e. tmpfs and other shmem based APIs).
 162          *
 163          * UFFD_FEATURE_SIGBUS feature means no page-fault
 164          * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
 165          * a SIGBUS signal will be sent to the faulting process.
 166          *
 167          * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
 168          * be returned, if feature is not requested 0 will be returned.
 169          */
 170 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP          (1<<0)
 171 #define UFFD_FEATURE_EVENT_FORK                 (1<<1)
 172 #define UFFD_FEATURE_EVENT_REMAP                (1<<2)
 173 #define UFFD_FEATURE_EVENT_REMOVE               (1<<3)
 174 #define UFFD_FEATURE_MISSING_HUGETLBFS          (1<<4)
 175 #define UFFD_FEATURE_MISSING_SHMEM              (1<<5)
 176 #define UFFD_FEATURE_EVENT_UNMAP                (1<<6)
 177 #define UFFD_FEATURE_SIGBUS                     (1<<7)
 178 #define UFFD_FEATURE_THREAD_ID                  (1<<8)
 179         __u64 features;
 180
 181         __u64 ioctls;
 182 };
 183
 184 struct uffdio_range {
 185         __u64 start;
 186         __u64 len;
 187 };
 188
 189 struct uffdio_register {
 190         struct uffdio_range range;
 191 #define UFFDIO_REGISTER_MODE_MISSING    ((__u64)1<<0)
 192 #define UFFDIO_REGISTER_MODE_WP         ((__u64)1<<1)
 193         __u64 mode;
 194
 195         /*
 196          * kernel answers which ioctl commands are available for the
 197          * range, keep at the end as the last 8 bytes aren't read.
 198          */
 199         __u64 ioctls;
 200 };
 201
 202 struct uffdio_copy {
 203         __u64 dst;
 204         __u64 src;
 205         __u64 len;
 206         /*
 207          * There will be a wrprotection flag later that allows to map
 208          * pages wrprotected on the fly. And such a flag will be
 209          * available if the wrprotection ioctl are implemented for the
 210          * range according to the uffdio_register.ioctls.
 211          */
 212 #define UFFDIO_COPY_MODE_DONTWAKE               ((__u64)1<<0)
 213         __u64 mode;
 214
 215         /*
 216          * "copy" is written by the ioctl and must be at the end: the
 217          * copy_from_user will not read the last 8 bytes.
 218          */
 219         __s64 copy;
 220 };
 221
 222 struct uffdio_zeropage {
 223         struct uffdio_range range;
 224 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE           ((__u64)1<<0)
 225         __u64 mode;
 226
 227         /*
 228          * "zeropage" is written by the ioctl and must be at the end:
 229          * the copy_from_user will not read the last 8 bytes.
 230          */
 231         __s64 zeropage;
 232 };
 233
 234 #endif /* _LINUX_USERFAULTFD_H */