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