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 /* ioctls for /dev/userfaultfd */
  16 #define USERFAULTFD_IOC 0xAA
  17 #define USERFAULTFD_IOC_NEW _IO(USERFAULTFD_IOC, 0x00)
  18
  19 /*
  20  * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
  21  * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
  22  * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
  23  * means the userland is reading).
  24  */
  25 #define UFFD_API ((__u64)0xAA)
  26 #define UFFD_API_REGISTER_MODES (UFFDIO_REGISTER_MODE_MISSING | \
  27                                  UFFDIO_REGISTER_MODE_WP |      \
  28                                  UFFDIO_REGISTER_MODE_MINOR)
  29 #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP |     \
  30                            UFFD_FEATURE_EVENT_FORK |            \
  31                            UFFD_FEATURE_EVENT_REMAP |           \
  32                            UFFD_FEATURE_EVENT_REMOVE |          \
  33                            UFFD_FEATURE_EVENT_UNMAP |           \
  34                            UFFD_FEATURE_MISSING_HUGETLBFS |     \
  35                            UFFD_FEATURE_MISSING_SHMEM |         \
  36                            UFFD_FEATURE_SIGBUS |                \
  37                            UFFD_FEATURE_THREAD_ID |             \
  38                            UFFD_FEATURE_MINOR_HUGETLBFS |       \
  39                            UFFD_FEATURE_MINOR_SHMEM |           \
  40                            UFFD_FEATURE_EXACT_ADDRESS |         \
  41                            UFFD_FEATURE_WP_HUGETLBFS_SHMEM |    \
  42                            UFFD_FEATURE_WP_UNPOPULATED |        \
  43                            UFFD_FEATURE_POISON |                \
  44                            UFFD_FEATURE_WP_ASYNC |              \
  45                            UFFD_FEATURE_MOVE)
  46 #define UFFD_API_IOCTLS                         \
  47         ((__u64)1 << _UFFDIO_REGISTER |         \
  48          (__u64)1 << _UFFDIO_UNREGISTER |       \
  49          (__u64)1 << _UFFDIO_API)
  50 #define UFFD_API_RANGE_IOCTLS                   \
  51         ((__u64)1 << _UFFDIO_WAKE |             \
  52          (__u64)1 << _UFFDIO_COPY |             \
  53          (__u64)1 << _UFFDIO_ZEROPAGE |         \
  54          (__u64)1 << _UFFDIO_MOVE |             \
  55          (__u64)1 << _UFFDIO_WRITEPROTECT |     \
  56          (__u64)1 << _UFFDIO_CONTINUE |         \
  57          (__u64)1 << _UFFDIO_POISON)
  58 #define UFFD_API_RANGE_IOCTLS_BASIC             \
  59         ((__u64)1 << _UFFDIO_WAKE |             \
  60          (__u64)1 << _UFFDIO_COPY |             \
  61          (__u64)1 << _UFFDIO_WRITEPROTECT |     \
  62          (__u64)1 << _UFFDIO_CONTINUE |         \
  63          (__u64)1 << _UFFDIO_POISON)
  64
  65 /*
  66  * Valid ioctl command number range with this API is from 0x00 to
  67  * 0x3F.  UFFDIO_API is the fixed number, everything else can be
  68  * changed by implementing a different UFFD_API. If sticking to the
  69  * same UFFD_API more ioctl can be added and userland will be aware of
  70  * which ioctl the running kernel implements through the ioctl command
  71  * bitmask written by the UFFDIO_API.
  72  */
  73 #define _UFFDIO_REGISTER                (0x00)
  74 #define _UFFDIO_UNREGISTER              (0x01)
  75 #define _UFFDIO_WAKE                    (0x02)
  76 #define _UFFDIO_COPY                    (0x03)
  77 #define _UFFDIO_ZEROPAGE                (0x04)
  78 #define _UFFDIO_MOVE                    (0x05)
  79 #define _UFFDIO_WRITEPROTECT            (0x06)
  80 #define _UFFDIO_CONTINUE                (0x07)
  81 #define _UFFDIO_POISON                  (0x08)
  82 #define _UFFDIO_API                     (0x3F)
  83
  84 /* userfaultfd ioctl ids */
  85 #define UFFDIO 0xAA
  86 #define UFFDIO_API              _IOWR(UFFDIO, _UFFDIO_API,      \
  87                                       struct uffdio_api)
  88 #define UFFDIO_REGISTER         _IOWR(UFFDIO, _UFFDIO_REGISTER, \
  89                                       struct uffdio_register)
  90 #define UFFDIO_UNREGISTER       _IOR(UFFDIO, _UFFDIO_UNREGISTER,        \
  91                                      struct uffdio_range)
  92 #define UFFDIO_WAKE             _IOR(UFFDIO, _UFFDIO_WAKE,      \
  93                                      struct uffdio_range)
  94 #define UFFDIO_COPY             _IOWR(UFFDIO, _UFFDIO_COPY,     \
  95                                       struct uffdio_copy)
  96 #define UFFDIO_ZEROPAGE         _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \
  97                                       struct uffdio_zeropage)
  98 #define UFFDIO_MOVE             _IOWR(UFFDIO, _UFFDIO_MOVE,     \
  99                                       struct uffdio_move)
 100 #define UFFDIO_WRITEPROTECT     _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \
 101                                       struct uffdio_writeprotect)
 102 #define UFFDIO_CONTINUE         _IOWR(UFFDIO, _UFFDIO_CONTINUE, \
 103                                       struct uffdio_continue)
 104 #define UFFDIO_POISON           _IOWR(UFFDIO, _UFFDIO_POISON, \
 105                                       struct uffdio_poison)
 106
 107 /* read() structure */
 108 struct uffd_msg {
 109         __u8    event;
 110
 111         __u8    reserved1;
 112         __u16   reserved2;
 113         __u32   reserved3;
 114
 115         union {
 116                 struct {
 117                         __u64   flags;
 118                         __u64   address;
 119                         union {
 120                                 __u32 ptid;
 121                         } feat;
 122                 } pagefault;
 123
 124                 struct {
 125                         __u32   ufd;
 126                 } fork;
 127
 128                 struct {
 129                         __u64   from;
 130                         __u64   to;
 131                         __u64   len;
 132                 } remap;
 133
 134                 struct {
 135                         __u64   start;
 136                         __u64   end;
 137                 } remove;
 138
 139                 struct {
 140                         /* unused reserved fields */
 141                         __u64   reserved1;
 142                         __u64   reserved2;
 143                         __u64   reserved3;
 144                 } reserved;
 145         } arg;
 146 } __attribute__((packed));
 147
 148 /*
 149  * Start at 0x12 and not at 0 to be more strict against bugs.
 150  */
 151 #define UFFD_EVENT_PAGEFAULT    0x12
 152 #define UFFD_EVENT_FORK         0x13
 153 #define UFFD_EVENT_REMAP        0x14
 154 #define UFFD_EVENT_REMOVE       0x15
 155 #define UFFD_EVENT_UNMAP        0x16
 156
 157 /* flags for UFFD_EVENT_PAGEFAULT */
 158 #define UFFD_PAGEFAULT_FLAG_WRITE       (1<<0)  /* If this was a write fault */
 159 #define UFFD_PAGEFAULT_FLAG_WP          (1<<1)  /* If reason is VM_UFFD_WP */
 160 #define UFFD_PAGEFAULT_FLAG_MINOR       (1<<2)  /* If reason is VM_UFFD_MINOR */
 161
 162 struct uffdio_api {
 163         /* userland asks for an API number and the features to enable */
 164         __u64 api;
 165         /*
 166          * Kernel answers below with the all available features for
 167          * the API, this notifies userland of which events and/or
 168          * which flags for each event are enabled in the current
 169          * kernel.
 170          *
 171          * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
 172          * are to be considered implicitly always enabled in all kernels as
 173          * long as the uffdio_api.api requested matches UFFD_API.
 174          *
 175          * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
 176          * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
 177          * hugetlbfs virtual memory ranges. Adding or not adding
 178          * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
 179          * no real functional effect after UFFDIO_API returns, but
 180          * it's only useful for an initial feature set probe at
 181          * UFFDIO_API time. There are two ways to use it:
 182          *
 183          * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
 184          *    uffdio_api.features before calling UFFDIO_API, an error
 185          *    will be returned by UFFDIO_API on a kernel without
 186          *    hugetlbfs missing support
 187          *
 188          * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
 189          *    uffdio_api.features and instead it will be set by the
 190          *    kernel in the uffdio_api.features if the kernel supports
 191          *    it, so userland can later check if the feature flag is
 192          *    present in uffdio_api.features after UFFDIO_API
 193          *    succeeded.
 194          *
 195          * UFFD_FEATURE_MISSING_SHMEM works the same as
 196          * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
 197          * (i.e. tmpfs and other shmem based APIs).
 198          *
 199          * UFFD_FEATURE_SIGBUS feature means no page-fault
 200          * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
 201          * a SIGBUS signal will be sent to the faulting process.
 202          *
 203          * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
 204          * be returned, if feature is not requested 0 will be returned.
 205          *
 206          * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults
 207          * can be intercepted (via REGISTER_MODE_MINOR) for
 208          * hugetlbfs-backed pages.
 209          *
 210          * UFFD_FEATURE_MINOR_SHMEM indicates the same support as
 211          * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead.
 212          *
 213          * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page
 214          * faults would be provided and the offset within the page would not be
 215          * masked.
 216          *
 217          * UFFD_FEATURE_WP_HUGETLBFS_SHMEM indicates that userfaultfd
 218          * write-protection mode is supported on both shmem and hugetlbfs.
 219          *
 220          * UFFD_FEATURE_WP_UNPOPULATED indicates that userfaultfd
 221          * write-protection mode will always apply to unpopulated pages
 222          * (i.e. empty ptes).  This will be the default behavior for shmem
 223          * & hugetlbfs, so this flag only affects anonymous memory behavior
 224          * when userfault write-protection mode is registered.
 225          *
 226          * UFFD_FEATURE_WP_ASYNC indicates that userfaultfd write-protection
 227          * asynchronous mode is supported in which the write fault is
 228          * automatically resolved and write-protection is un-set.
 229          * It implies UFFD_FEATURE_WP_UNPOPULATED.
 230          *
 231          * UFFD_FEATURE_MOVE indicates that the kernel supports moving an
 232          * existing page contents from userspace.
 233          */
 234 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP          (1<<0)
 235 #define UFFD_FEATURE_EVENT_FORK                 (1<<1)
 236 #define UFFD_FEATURE_EVENT_REMAP                (1<<2)
 237 #define UFFD_FEATURE_EVENT_REMOVE               (1<<3)
 238 #define UFFD_FEATURE_MISSING_HUGETLBFS          (1<<4)
 239 #define UFFD_FEATURE_MISSING_SHMEM              (1<<5)
 240 #define UFFD_FEATURE_EVENT_UNMAP                (1<<6)
 241 #define UFFD_FEATURE_SIGBUS                     (1<<7)
 242 #define UFFD_FEATURE_THREAD_ID                  (1<<8)
 243 #define UFFD_FEATURE_MINOR_HUGETLBFS            (1<<9)
 244 #define UFFD_FEATURE_MINOR_SHMEM                (1<<10)
 245 #define UFFD_FEATURE_EXACT_ADDRESS              (1<<11)
 246 #define UFFD_FEATURE_WP_HUGETLBFS_SHMEM         (1<<12)
 247 #define UFFD_FEATURE_WP_UNPOPULATED             (1<<13)
 248 #define UFFD_FEATURE_POISON                     (1<<14)
 249 #define UFFD_FEATURE_WP_ASYNC                   (1<<15)
 250 #define UFFD_FEATURE_MOVE                       (1<<16)
 251         __u64 features;
 252
 253         __u64 ioctls;
 254 };
 255
 256 struct uffdio_range {
 257         __u64 start;
 258         __u64 len;
 259 };
 260
 261 struct uffdio_register {
 262         struct uffdio_range range;
 263 #define UFFDIO_REGISTER_MODE_MISSING    ((__u64)1<<0)
 264 #define UFFDIO_REGISTER_MODE_WP         ((__u64)1<<1)
 265 #define UFFDIO_REGISTER_MODE_MINOR      ((__u64)1<<2)
 266         __u64 mode;
 267
 268         /*
 269          * kernel answers which ioctl commands are available for the
 270          * range, keep at the end as the last 8 bytes aren't read.
 271          */
 272         __u64 ioctls;
 273 };
 274
 275 struct uffdio_copy {
 276         __u64 dst;
 277         __u64 src;
 278         __u64 len;
 279 #define UFFDIO_COPY_MODE_DONTWAKE               ((__u64)1<<0)
 280         /*
 281          * UFFDIO_COPY_MODE_WP will map the page write protected on
 282          * the fly.  UFFDIO_COPY_MODE_WP is available only if the
 283          * write protected ioctl is implemented for the range
 284          * according to the uffdio_register.ioctls.
 285          */
 286 #define UFFDIO_COPY_MODE_WP                     ((__u64)1<<1)
 287         __u64 mode;
 288
 289         /*
 290          * "copy" is written by the ioctl and must be at the end: the
 291          * copy_from_user will not read the last 8 bytes.
 292          */
 293         __s64 copy;
 294 };
 295
 296 struct uffdio_zeropage {
 297         struct uffdio_range range;
 298 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE           ((__u64)1<<0)
 299         __u64 mode;
 300
 301         /*
 302          * "zeropage" is written by the ioctl and must be at the end:
 303          * the copy_from_user will not read the last 8 bytes.
 304          */
 305         __s64 zeropage;
 306 };
 307
 308 struct uffdio_writeprotect {
 309         struct uffdio_range range;
 310 /*
 311  * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range,
 312  * unset the flag to undo protection of a range which was previously
 313  * write protected.
 314  *
 315  * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up
 316  * any wait thread after the operation succeeds.
 317  *
 318  * NOTE: Write protecting a region (WP=1) is unrelated to page faults,
 319  * therefore DONTWAKE flag is meaningless with WP=1.  Removing write
 320  * protection (WP=0) in response to a page fault wakes the faulting
 321  * task unless DONTWAKE is set.
 322  */
 323 #define UFFDIO_WRITEPROTECT_MODE_WP             ((__u64)1<<0)
 324 #define UFFDIO_WRITEPROTECT_MODE_DONTWAKE       ((__u64)1<<1)
 325         __u64 mode;
 326 };
 327
 328 struct uffdio_continue {
 329         struct uffdio_range range;
 330 #define UFFDIO_CONTINUE_MODE_DONTWAKE           ((__u64)1<<0)
 331         /*
 332          * UFFDIO_CONTINUE_MODE_WP will map the page write protected on
 333          * the fly.  UFFDIO_CONTINUE_MODE_WP is available only if the
 334          * write protected ioctl is implemented for the range
 335          * according to the uffdio_register.ioctls.
 336          */
 337 #define UFFDIO_CONTINUE_MODE_WP                 ((__u64)1<<1)
 338         __u64 mode;
 339
 340         /*
 341          * Fields below here are written by the ioctl and must be at the end:
 342          * the copy_from_user will not read past here.
 343          */
 344         __s64 mapped;
 345 };
 346
 347 struct uffdio_poison {
 348         struct uffdio_range range;
 349 #define UFFDIO_POISON_MODE_DONTWAKE             ((__u64)1<<0)
 350         __u64 mode;
 351
 352         /*
 353          * Fields below here are written by the ioctl and must be at the end:
 354          * the copy_from_user will not read past here.
 355          */
 356         __s64 updated;
 357 };
 358
 359 struct uffdio_move {
 360         __u64 dst;
 361         __u64 src;
 362         __u64 len;
 363         /*
 364          * Especially if used to atomically remove memory from the
 365          * address space the wake on the dst range is not needed.
 366          */
 367 #define UFFDIO_MOVE_MODE_DONTWAKE               ((__u64)1<<0)
 368 #define UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES        ((__u64)1<<1)
 369         __u64 mode;
 370         /*
 371          * "move" is written by the ioctl and must be at the end: the
 372          * copy_from_user will not read the last 8 bytes.
 373          */
 374         __s64 move;
 375 };
 376
 377 /*
 378  * Flags for the userfaultfd(2) system call itself.
 379  */
 380
 381 /*
 382  * Create a userfaultfd that can handle page faults only in user mode.
 383  */
 384 #define UFFD_USER_MODE_ONLY 1
 385
 386 #endif /* _LINUX_USERFAULTFD_H */