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