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