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