linux-headers/linux/userfaultfd.h

   1 /*
   2  *  include/linux/userfaultfd.h
   3  *
   4  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
   5  *  Copyright (C) 2015  Red Hat, Inc.
   6  *
   7  */
   8
   9 #ifndef _LINUX_USERFAULTFD_H
  10 #define _LINUX_USERFAULTFD_H
  11
  12 #include <linux/types.h>
  13
  14 /*
  15  * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
  16  * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
  17  * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
  18  * means the userland is reading).
  19  */
  20 #define UFFD_API ((__u64)0xAA)
  21 #define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |            \
  22                            UFFD_FEATURE_EVENT_REMAP |           \
  23                            UFFD_FEATURE_EVENT_REMOVE |  \
  24                            UFFD_FEATURE_EVENT_UNMAP |           \
  25                            UFFD_FEATURE_MISSING_HUGETLBFS |     \
  26                            UFFD_FEATURE_MISSING_SHMEM |         \
  27                            UFFD_FEATURE_SIGBUS |                \
  28                            UFFD_FEATURE_THREAD_ID)
  29 #define UFFD_API_IOCTLS                         \
  30         ((__u64)1 << _UFFDIO_REGISTER |         \
  31          (__u64)1 << _UFFDIO_UNREGISTER |       \
  32          (__u64)1 << _UFFDIO_API)
  33 #define UFFD_API_RANGE_IOCTLS                   \
  34         ((__u64)1 << _UFFDIO_WAKE |             \
  35          (__u64)1 << _UFFDIO_COPY |             \
  36          (__u64)1 << _UFFDIO_ZEROPAGE)
  37 #define UFFD_API_RANGE_IOCTLS_BASIC             \
  38         ((__u64)1 << _UFFDIO_WAKE |             \
  39          (__u64)1 << _UFFDIO_COPY)
  40
  41 /*
  42  * Valid ioctl command number range with this API is from 0x00 to
  43  * 0x3F.  UFFDIO_API is the fixed number, everything else can be
  44  * changed by implementing a different UFFD_API. If sticking to the
  45  * same UFFD_API more ioctl can be added and userland will be aware of
  46  * which ioctl the running kernel implements through the ioctl command
  47  * bitmask written by the UFFDIO_API.
  48  */
  49 #define _UFFDIO_REGISTER                (0x00)
  50 #define _UFFDIO_UNREGISTER              (0x01)
  51 #define _UFFDIO_WAKE                    (0x02)
  52 #define _UFFDIO_COPY                    (0x03)
  53 #define _UFFDIO_ZEROPAGE                (0x04)
  54 #define _UFFDIO_API                     (0x3F)
  55
  56 /* userfaultfd ioctl ids */
  57 #define UFFDIO 0xAA
  58 #define UFFDIO_API              _IOWR(UFFDIO, _UFFDIO_API,      \
  59                                       struct uffdio_api)
  60 #define UFFDIO_REGISTER         _IOWR(UFFDIO, _UFFDIO_REGISTER, \
  61                                       struct uffdio_register)
  62 #define UFFDIO_UNREGISTER       _IOR(UFFDIO, _UFFDIO_UNREGISTER,        \
  63                                      struct uffdio_range)
  64 #define UFFDIO_WAKE             _IOR(UFFDIO, _UFFDIO_WAKE,      \
  65                                      struct uffdio_range)
  66 #define UFFDIO_COPY             _IOWR(UFFDIO, _UFFDIO_COPY,     \
  67                                       struct uffdio_copy)
  68 #define UFFDIO_ZEROPAGE         _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \
  69                                       struct uffdio_zeropage)
  70
  71 /* read() structure */
  72 struct uffd_msg {
  73         __u8    event;
  74
  75         __u8    reserved1;
  76         __u16   reserved2;
  77         __u32   reserved3;
  78
  79         union {
  80                 struct {
  81                         __u64   flags;
  82                         __u64   address;
  83                         union {
  84                                 __u32 ptid;
  85                         } feat;
  86                 } pagefault;
  87
  88                 struct {
  89                         __u32   ufd;
  90                 } fork;
  91
  92                 struct {
  93                         __u64   from;
  94                         __u64   to;
  95                         __u64   len;
  96                 } remap;
  97
  98                 struct {
  99                         __u64   start;
 100                         __u64   end;
 101                 } remove;
 102
 103                 struct {
 104                         /* unused reserved fields */
 105                         __u64   reserved1;
 106                         __u64   reserved2;
 107                         __u64   reserved3;
 108                 } reserved;
 109         } arg;
 110 } __attribute__((packed));
 111
 112 /*
 113  * Start at 0x12 and not at 0 to be more strict against bugs.
 114  */
 115 #define UFFD_EVENT_PAGEFAULT    0x12
 116 #define UFFD_EVENT_FORK         0x13
 117 #define UFFD_EVENT_REMAP        0x14
 118 #define UFFD_EVENT_REMOVE       0x15
 119 #define UFFD_EVENT_UNMAP        0x16
 120
 121 /* flags for UFFD_EVENT_PAGEFAULT */
 122 #define UFFD_PAGEFAULT_FLAG_WRITE       (1<<0)  /* If this was a write fault */
 123 #define UFFD_PAGEFAULT_FLAG_WP          (1<<1)  /* If reason is VM_UFFD_WP */
 124
 125 struct uffdio_api {
 126         /* userland asks for an API number and the features to enable */
 127         __u64 api;
 128         /*
 129          * Kernel answers below with the all available features for
 130          * the API, this notifies userland of which events and/or
 131          * which flags for each event are enabled in the current
 132          * kernel.
 133          *
 134          * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
 135          * are to be considered implicitly always enabled in all kernels as
 136          * long as the uffdio_api.api requested matches UFFD_API.
 137          *
 138          * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
 139          * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
 140          * hugetlbfs virtual memory ranges. Adding or not adding
 141          * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
 142          * no real functional effect after UFFDIO_API returns, but
 143          * it's only useful for an initial feature set probe at
 144          * UFFDIO_API time. There are two ways to use it:
 145          *
 146          * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
 147          *    uffdio_api.features before calling UFFDIO_API, an error
 148          *    will be returned by UFFDIO_API on a kernel without
 149          *    hugetlbfs missing support
 150          *
 151          * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
 152          *    uffdio_api.features and instead it will be set by the
 153          *    kernel in the uffdio_api.features if the kernel supports
 154          *    it, so userland can later check if the feature flag is
 155          *    present in uffdio_api.features after UFFDIO_API
 156          *    succeeded.
 157          *
 158          * UFFD_FEATURE_MISSING_SHMEM works the same as
 159          * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
 160          * (i.e. tmpfs and other shmem based APIs).
 161          *
 162          * UFFD_FEATURE_SIGBUS feature means no page-fault
 163          * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
 164          * a SIGBUS signal will be sent to the faulting process.
 165          *
 166          * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
 167          * be returned, if feature is not requested 0 will be returned.
 168          */
 169 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP          (1<<0)
 170 #define UFFD_FEATURE_EVENT_FORK                 (1<<1)
 171 #define UFFD_FEATURE_EVENT_REMAP                (1<<2)
 172 #define UFFD_FEATURE_EVENT_REMOVE               (1<<3)
 173 #define UFFD_FEATURE_MISSING_HUGETLBFS          (1<<4)
 174 #define UFFD_FEATURE_MISSING_SHMEM              (1<<5)
 175 #define UFFD_FEATURE_EVENT_UNMAP                (1<<6)
 176 #define UFFD_FEATURE_SIGBUS                     (1<<7)
 177 #define UFFD_FEATURE_THREAD_ID                  (1<<8)
 178         __u64 features;
 179
 180         __u64 ioctls;
 181 };
 182
 183 struct uffdio_range {
 184         __u64 start;
 185         __u64 len;
 186 };
 187
 188 struct uffdio_register {
 189         struct uffdio_range range;
 190 #define UFFDIO_REGISTER_MODE_MISSING    ((__u64)1<<0)
 191 #define UFFDIO_REGISTER_MODE_WP         ((__u64)1<<1)
 192         __u64 mode;
 193
 194         /*
 195          * kernel answers which ioctl commands are available for the
 196          * range, keep at the end as the last 8 bytes aren't read.
 197          */
 198         __u64 ioctls;
 199 };
 200
 201 struct uffdio_copy {
 202         __u64 dst;
 203         __u64 src;
 204         __u64 len;
 205         /*
 206          * There will be a wrprotection flag later that allows to map
 207          * pages wrprotected on the fly. And such a flag will be
 208          * available if the wrprotection ioctl are implemented for the
 209          * range according to the uffdio_register.ioctls.
 210          */
 211 #define UFFDIO_COPY_MODE_DONTWAKE               ((__u64)1<<0)
 212         __u64 mode;
 213
 214         /*
 215          * "copy" is written by the ioctl and must be at the end: the
 216          * copy_from_user will not read the last 8 bytes.
 217          */
 218         __s64 copy;
 219 };
 220
 221 struct uffdio_zeropage {
 222         struct uffdio_range range;
 223 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE           ((__u64)1<<0)
 224         __u64 mode;
 225
 226         /*
 227          * "zeropage" is written by the ioctl and must be at the end:
 228          * the copy_from_user will not read the last 8 bytes.
 229          */
 230         __s64 zeropage;
 231 };
 232
 233 #endif /* _LINUX_USERFAULTFD_H */