include/mount-api-utils.h

   1 /*
   2  * No copyright is claimed.  This code is in the public domain; do with
   3  * it what you wish.
   4  */
   5 #ifndef UTIL_LINUX_MOUNT_API_UTILS
   6 #define UTIL_LINUX_MOUNT_API_UTILS
   7
   8 #ifdef HAVE_LINUX_MOUNT_H
   9 #include <sys/mount.h>
  10 #include <linux/mount.h>
  11 #include <linux/unistd.h>
  12 #include <sys/syscall.h>
  13 #include <inttypes.h>
  14
  15 /*
  16  * File descritors based mount API
  17  */
  18 #ifdef HAVE_MOUNTFD_API
  19
  20 /* Accepted by both open_tree() and mount_setattr(). */
  21 #ifndef AT_RECURSIVE
  22 # define AT_RECURSIVE 0x8000
  23 #endif
  24
  25 #ifndef OPEN_TREE_CLONE
  26 # define OPEN_TREE_CLONE 1
  27 #endif
  28
  29 #ifndef OPEN_TREE_CLOEXEC
  30 # define OPEN_TREE_CLOEXEC O_CLOEXEC
  31 #endif
  32
  33 #if !defined(HAVE_OPEN_TREE) && defined(SYS_open_tree)
  34 static inline int open_tree(int dfd, const char *filename, unsigned int flags)
  35 {
  36         return syscall(SYS_open_tree, dfd, filename, flags);
  37 }
  38 #endif
  39
  40 #ifndef MOVE_MOUNT_F_SYMLINKS
  41 # define MOVE_MOUNT_F_SYMLINKS   0x00000001 /* Follow symlinks on from path */
  42 #endif
  43
  44 #ifndef MOVE_MOUNT_F_AUTOMOUNTS
  45 # define MOVE_MOUNT_F_AUTOMOUNTS 0x00000002 /* Follow automounts on from path */
  46 #endif
  47
  48 #ifndef MOVE_MOUNT_F_EMPTY_PATH
  49 # define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 /* Empty from path permitted */
  50 #endif
  51
  52 #ifndef MOVE_MOUNT_T_SYMLINKS
  53 # define MOVE_MOUNT_T_SYMLINKS   0x00000010 /* Follow symlinks on to path */
  54 #endif
  55
  56 #ifndef MOVE_MOUNT_T_AUTOMOUNTS
  57 # define MOVE_MOUNT_T_AUTOMOUNTS 0x00000020 /* Follow automounts on to path */
  58 #endif
  59
  60 #ifndef MOVE_MOUNT_T_EMPTY_PATH
  61 # define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */
  62 #endif
  63
  64 #ifndef MOVE_MOUNT_SET_GROUP
  65 # define MOVE_MOUNT_SET_GROUP    0x00000100 /* Set sharing group instead */
  66 #endif
  67
  68 #ifndef MOVE_MOUNT__MASK
  69 # define MOVE_MOUNT__MASK 0x00000077
  70 #endif
  71
  72 #if !defined(HAVE_MOVE_MOUNT) && defined(SYS_move_mount)
  73 static inline int move_mount(int from_dfd, const char *from_pathname, int to_dfd,
  74                              const char *to_pathname, unsigned int flags)
  75 {
  76         return syscall(SYS_move_mount, from_dfd, from_pathname, to_dfd,
  77                        to_pathname, flags);
  78 }
  79 #endif
  80
  81 #ifndef MOUNT_ATTR_RDONLY
  82 # define MOUNT_ATTR_RDONLY 0x00000001
  83 #endif
  84
  85 #ifndef MOUNT_ATTR_NOSUID
  86 # define MOUNT_ATTR_NOSUID 0x00000002
  87 #endif
  88
  89 #ifndef MOUNT_ATTR_NODEV
  90 # define MOUNT_ATTR_NODEV 0x00000004
  91 #endif
  92
  93 #ifndef MOUNT_ATTR_NOEXEC
  94 # define MOUNT_ATTR_NOEXEC 0x00000008
  95 #endif
  96
  97 #ifndef MOUNT_ATTR__ATIME
  98 # define MOUNT_ATTR__ATIME 0x00000070
  99 #endif
 100
 101 #ifndef MOUNT_ATTR_RELATIME
 102 # define MOUNT_ATTR_RELATIME 0x00000000
 103 #endif
 104
 105 #ifndef MOUNT_ATTR_NOATIME
 106 # define MOUNT_ATTR_NOATIME 0x00000010
 107 #endif
 108
 109 #ifndef MOUNT_ATTR_STRICTATIME
 110 # define MOUNT_ATTR_STRICTATIME 0x00000020
 111 #endif
 112
 113 #ifndef MOUNT_ATTR_NODIRATIME
 114 # define MOUNT_ATTR_NODIRATIME 0x00000080
 115 #endif
 116
 117 #ifndef MOUNT_ATTR_IDMAP
 118 # define MOUNT_ATTR_IDMAP 0x00100000
 119 #endif
 120
 121 #ifndef MOUNT_ATTR_NOSYMFOLLOW
 122 # define MOUNT_ATTR_NOSYMFOLLOW 0x00200000
 123 #endif
 124
 125 #ifndef HAVE_STRUCT_MOUNT_ATTR
 126 # ifndef MOUNT_ATTR_SIZE_VER0 /* For case mount.h comes from a place invisible for autotools/meson */
 127 # include <inttypes.h>
 128 struct mount_attr {
 129         uint64_t attr_set;
 130         uint64_t attr_clr;
 131         uint64_t propagation;
 132         uint64_t userns_fd;
 133 };
 134 # endif
 135 #endif
 136
 137 #if !defined(HAVE_MOUNT_SETATTR) && defined(SYS_mount_setattr)
 138 static inline int mount_setattr(int dfd, const char *path, unsigned int flags,
 139                                 struct mount_attr *attr, size_t size)
 140 {
 141         return syscall(SYS_mount_setattr, dfd, path, flags, attr, size);
 142 }
 143 #endif
 144
 145 #ifndef HAVE_ENUM_FSCONFIG_COMMAND
 146 # ifndef FSOPEN_CLOEXEC /* For case mount.h comes from a place invisible for autotools/meson */
 147 enum fsconfig_command {
 148         FSCONFIG_SET_FLAG       = 0,    /* Set parameter, supplying no value */
 149         FSCONFIG_SET_STRING     = 1,    /* Set parameter, supplying a string value */
 150         FSCONFIG_SET_BINARY     = 2,    /* Set parameter, supplying a binary blob value */
 151         FSCONFIG_SET_PATH       = 3,    /* Set parameter, supplying an object by path */
 152         FSCONFIG_SET_PATH_EMPTY = 4,    /* Set parameter, supplying an object by (empty) path */
 153         FSCONFIG_SET_FD         = 5,    /* Set parameter, supplying an object by fd */
 154         FSCONFIG_CMD_CREATE     = 6,    /* Invoke superblock creation */
 155         FSCONFIG_CMD_RECONFIGURE = 7,   /* Invoke superblock reconfiguration */
 156 };
 157 # endif
 158 #endif
 159
 160 #if !defined(HAVE_FSCONFIG) && defined(SYS_fsconfig)
 161 static inline int fsconfig(int fd, unsigned int cmd, const char *key,
 162                     const void *value, int aux)
 163 {
 164         return syscall(SYS_fsconfig, fd, cmd, key, value, aux);
 165 }
 166 #endif
 167
 168 #ifndef FSOPEN_CLOEXEC
 169 # define FSOPEN_CLOEXEC          0x00000001
 170 #endif
 171
 172 #if !defined(HAVE_FSOPEN) && defined(SYS_fsopen)
 173 static inline int fsopen(const char *fsname, unsigned int flags)
 174 {
 175         return syscall(SYS_fsopen, fsname, flags);
 176 }
 177 #endif
 178
 179 #ifndef FSMOUNT_CLOEXEC
 180 # define FSMOUNT_CLOEXEC         0x00000001
 181 #endif
 182
 183 #if !defined(HAVE_FSMOUNT) && defined(SYS_fsmount)
 184 static inline int fsmount(int fd, unsigned int flags, unsigned int mount_attrs)
 185 {
 186         return syscall(SYS_fsmount, fd, flags, mount_attrs);
 187 }
 188 #endif
 189
 190 #ifndef FSPICK_CLOEXEC
 191 # define FSPICK_CLOEXEC          0x00000001
 192 #endif
 193
 194 #ifndef FSPICK_SYMLINK_NOFOLLOW
 195 # define FSPICK_SYMLINK_NOFOLLOW 0x00000002
 196 #endif
 197
 198 #ifndef FSPICK_NO_AUTOMOUNT
 199 # define FSPICK_NO_AUTOMOUNT     0x00000004
 200 #endif
 201
 202 #ifdef FSPICK_EMPTY_PATH
 203 # define FSPICK_EMPTY_PATH       0x00000008
 204 #endif
 205
 206 #if !defined(HAVE_FSPICK) && defined(SYS_fspick)
 207 static inline int fspick(int dfd, const char *pathname, unsigned int flags)
 208 {
 209         return syscall(SYS_fspick, dfd, pathname, flags);
 210 }
 211 #endif
 212
 213 #endif /* HAVE_MOUNTFD_API */
 214
 215 /*
 216  * statmount() and listmount()
 217  */
 218 #ifdef HAVE_STATMOUNT_API
 219
 220 #ifndef MNT_ID_REQ_SIZE_VER0
 221 # define MNT_ID_REQ_SIZE_VER0    24 /* sizeof first published struct */
 222 #endif
 223 #ifndef MNT_ID_REQ_SIZE_VER1
 224 # define MNT_ID_REQ_SIZE_VER1    32 /* sizeof second published struct */
 225 #endif
 226
 227 /*
 228  * The structs mnt_id_req and statmount may differ between kernel versions, so
 229  * we must ensure that the structs contain everything we need. For now (during
 230  * development), it seems best to define local copies of the structs to avoid
 231  * relying on installed kernel headers and to avoid a storm of #ifdefs.
 232  */
 233
 234 /*
 235  * listmount() and statmount() request
 236  */
 237 struct ul_mnt_id_req {
 238         uint32_t size;
 239         uint32_t spare;
 240         uint64_t mnt_id;
 241         uint64_t param;
 242         uint64_t mnt_ns_id;
 243 };
 244
 245 /*
 246  * Please note that due to the variable length of the statmount buffer, the
 247  * struct cannot be versioned by size (like struct mnt_id_req).
 248  */
 249 struct ul_statmount {
 250         uint32_t size;            /* Total size, including strings */
 251         uint32_t mnt_opts;        /* [str] Mount options of the mount */
 252         uint64_t mask;            /* What results were written */
 253         uint32_t sb_dev_major;    /* Device ID */
 254         uint32_t sb_dev_minor;
 255         uint64_t sb_magic;        /* ..._SUPER_MAGIC */
 256         uint32_t sb_flags;        /* SB_{RDONLY,SYNCHRONOUS,DIRSYNC,LAZYTIME} */
 257         uint32_t fs_type;         /* [str] Filesystem type */
 258         uint64_t mnt_id;          /* Unique ID of mount */
 259         uint64_t mnt_parent_id;   /* Unique ID of parent (for root == mnt_id) */
 260         uint32_t mnt_id_old;      /* Reused IDs used in proc/.../mountinfo */
 261         uint32_t mnt_parent_id_old;
 262         uint64_t mnt_attr;        /* MOUNT_ATTR_... */
 263         uint64_t mnt_propagation; /* MS_{SHARED,SLAVE,PRIVATE,UNBINDABLE} */
 264         uint64_t mnt_peer_group;  /* ID of shared peer group */
 265         uint64_t mnt_master;      /* Mount receives propagation from this ID */
 266         uint64_t propagate_from;  /* Propagation from in current namespace */
 267         uint32_t mnt_root;        /* [str] Root of mount relative to root of fs */
 268         uint32_t mnt_point;       /* [str] Mountpoint relative to current root */
 269         uint64_t mnt_ns_id;       /* ID of the mount namespace */
 270         uint32_t fs_subtype;      /* [str] Subtype of fs_type (if any) */
 271         uint32_t sb_source;       /* [str] Source string of the mount */
 272         uint32_t opt_num;         /* Number of fs options */
 273         uint32_t opt_array;       /* [str] Array of nul terminated fs options */
 274         uint32_t opt_sec_num;     /* Number of security options */
 275         uint32_t opt_sec_array;   /* [str] Array of nul terminated security options */
 276         uint64_t __spare2[46];
 277         char str[];               /* Variable size part containing strings */
 278 };
 279
 280 /* sb_flags (defined in kernel include/linux/fs.h) */
 281 #ifndef SB_RDONLY
 282 # define SB_RDONLY       BIT(0)   /* Mount read-only */
 283 # define SB_NOSUID       BIT(1)   /* Ignore suid and sgid bits */
 284 # define SB_NODEV        BIT(2)   /* Disallow access to device special files */
 285 # define SB_NOEXEC       BIT(3)   /* Disallow program execution */
 286 # define SB_SYNCHRONOUS  BIT(4)   /* Writes are synced at once */
 287 # define SB_MANDLOCK     BIT(6)   /* Allow mandatory locks on an FS */
 288 # define SB_DIRSYNC      BIT(7)   /* Directory modifications are synchronous */
 289 # define SB_NOATIME      BIT(10)  /* Do not update access times. */
 290 # define SB_NODIRATIME   BIT(11)  /* Do not update directory access times */
 291 # define SB_SILENT       BIT(15)
 292 # define SB_POSIXACL     BIT(16)  /* Supports POSIX ACLs */
 293 # define SB_INLINECRYPT  BIT(17)  /* Use blk-crypto for encrypted files */
 294 # define SB_KERNMOUNT    BIT(22)  /* this is a kern_mount call */
 295 # define SB_I_VERSION    BIT(23)  /* Update inode I_version field */
 296 # define SB_LAZYTIME     BIT(25)  /* Update the on-disk [acm]times lazily */
 297 #endif
 298
 299 /*
 300  * @mask bits for statmount(2)
 301  */
 302 #ifndef STATMOUNT_SB_BASIC
 303 # define STATMOUNT_SB_BASIC            0x00000001U   /* Want/got sb_... */
 304 #endif
 305 #ifndef STATMOUNT_MNT_BASIC
 306 # define STATMOUNT_MNT_BASIC           0x00000002U   /* Want/got mnt_... */
 307 #endif
 308 #ifndef STATMOUNT_PROPAGATE_FROM
 309 # define STATMOUNT_PROPAGATE_FROM      0x00000004U   /* Want/got propagate_from */
 310 #endif
 311 #ifndef STATMOUNT_MNT_ROOT
 312 # define STATMOUNT_MNT_ROOT            0x00000008U   /* Want/got mnt_root  */
 313 #endif
 314 #ifndef STATMOUNT_MNT_POINT
 315 # define STATMOUNT_MNT_POINT           0x00000010U   /* Want/got mnt_point */
 316 #endif
 317 #ifndef STATMOUNT_FS_TYPE
 318 # define STATMOUNT_FS_TYPE             0x00000020U   /* Want/got fs_type */
 319 #endif
 320 #ifndef STATMOUNT_MNT_NS_ID
 321 # define STATMOUNT_MNT_NS_ID           0x00000040U   /* Want/got mnt_ns_id */
 322 #endif
 323 #ifndef STATMOUNT_MNT_OPTS
 324 # define STATMOUNT_MNT_OPTS            0x00000080U   /* Want/got mnt_opts */
 325 #endif
 326 #ifndef STATMOUNT_FS_SUBTYPE
 327 # define STATMOUNT_FS_SUBTYPE          0x00000100U   /* Want/got fs_subtype */
 328 #endif
 329 #ifndef STATMOUNT_SB_SOURCE
 330 # define STATMOUNT_SB_SOURCE           0x00000200U   /* Want/got sb_source */
 331 #endif
 332 #ifndef STATMOUNT_OPT_ARRAY
 333 # define STATMOUNT_OPT_ARRAY           0x00000400U   /* Want/got opt_... */
 334 #endif
 335 #ifndef STATMOUNT_OPT_SEC_ARRAY
 336 # define STATMOUNT_OPT_SEC_ARRAY       0x00000800U   /* Want/got opt_sec... */
 337 #endif
 338
 339
 340 /*
 341  * Special @mnt_id values that can be passed to listmount
 342  */
 343 #ifdef LSMT_ROOT
 344 # define LSMT_ROOT              0xffffffffffffffff    /* root mount */
 345 #endif
 346
 347 #ifndef LISTMOUNT_REVERSE
 348 # define LISTMOUNT_REVERSE      BIT(0)               /* List later mounts first */
 349 #endif
 350
 351 /* Don't use this "raw" version. See ul_statmount() below. */
 352 #if defined(SYS_statmount)
 353 static inline int ul_statmount_syscall(uint64_t mnt_id,
 354                         uint64_t ns_id,
 355                         uint64_t mask,
 356                         struct ul_statmount *buf,
 357                         size_t bufsize, unsigned int flags)
 358 {
 359        struct ul_mnt_id_req req = {
 360                 .size = MNT_ID_REQ_SIZE_VER1,
 361                 .mnt_id = mnt_id,
 362                 .param = mask,
 363                 .mnt_ns_id = ns_id
 364        };
 365
 366        return syscall(SYS_statmount, &req, buf, bufsize, flags);
 367 }
 368
 369 static inline int has_statmount(void)
 370 {
 371         errno = 0;
 372
 373         if (ul_statmount_syscall(0, 0, 0, NULL, 0, 0) < 0 && errno == ENOSYS)
 374                 return 0;
 375         return 1;
 376 }
 377
 378 /* This is a version of statmount() that reallocates @buf to be large enough to
 379  * store data for the requested @id. This function never deallocates; it is the
 380  * caller's responsibility.
 381  */
 382 static inline int ul_statmount(uint64_t id,
 383                         uint64_t ns_id,
 384                         uint64_t mask,
 385                         struct ul_statmount **buf,
 386                         size_t *bufsiz,
 387                         unsigned int flags)
 388 {
 389         size_t sz;
 390         int rc = 0;
 391
 392         if (!buf || !bufsiz)
 393                 return -EINVAL;
 394
 395         sz = *bufsiz;
 396         if (!sz)
 397                 sz = 32 * 1024;
 398
 399         do {
 400                 if (sz > *bufsiz) {
 401                         struct ul_statmount *tmp = realloc(*buf, sz);
 402                         if (!tmp)
 403                                 return -ENOMEM;
 404                         *buf = tmp;
 405                         *bufsiz = sz;
 406                 }
 407
 408                 errno = 0;
 409                 rc = ul_statmount_syscall(id, ns_id, mask, *buf, *bufsiz, flags);
 410                 if (!rc)
 411                         break;
 412                 if (errno != EOVERFLOW)
 413                         break;
 414                 if (sz >= SIZE_MAX / 2)
 415                         break;
 416                 sz <<= 1;
 417         } while (rc);
 418
 419         return rc;
 420 }
 421 #endif /* SYS_statmount */
 422
 423
 424 #if defined(SYS_listmount)
 425 static inline ssize_t ul_listmount(uint64_t mnt_id,
 426                         uint64_t ns_id,
 427                         uint64_t last_mnt_id,
 428                         uint64_t list[], size_t num,
 429                         unsigned int flags)
 430 {
 431        struct ul_mnt_id_req req = {
 432                 .size = MNT_ID_REQ_SIZE_VER1,
 433                 .mnt_id = mnt_id,
 434                 .param = last_mnt_id,
 435                 .mnt_ns_id = ns_id
 436        };
 437
 438        return syscall(SYS_listmount, &req, list, num, flags);
 439 }
 440
 441 static inline int has_listmount(void)
 442 {
 443         uint64_t dummy;
 444
 445         errno = 0;
 446
 447         if (ul_listmount(LSMT_ROOT, 0, 0, &dummy, 1, LISTMOUNT_REVERSE) != 1)
 448                 return 0;
 449         return 1;
 450 }
 451 #endif
 452
 453 #endif /* HAVE_STATMOUNT_API */
 454
 455 #endif /* HAVE_LINUX_MOUNT_H */
 456
 457 #endif /* UTIL_LINUX_MOUNT_API_UTILS */