lib/utimens.c

   1 /* Set file access and modification times.
   2
   3    Copyright (C) 2003-2017 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU General Public License as published by the
   7    Free Software Foundation; either version 3 of the License, or any
   8    later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 /* derived from a function in touch.c */
  21
  22 #include <config.h>
  23
  24 #define _GL_UTIMENS_INLINE _GL_EXTERN_INLINE
  25 #include "utimens.h"
  26
  27 #include <errno.h>
  28 #include <fcntl.h>
  29 #include <stdbool.h>
  30 #include <sys/stat.h>
  31 #include <sys/time.h>
  32 #include <unistd.h>
  33
  34 #include "stat-time.h"
  35 #include "timespec.h"
  36
  37 #if HAVE_UTIME_H
  38 # include <utime.h>
  39 #endif
  40
  41 /* Some systems (even some that do have <utime.h>) don't declare this
  42    structure anywhere.  */
  43 #ifndef HAVE_STRUCT_UTIMBUF
  44 struct utimbuf
  45 {
  46   long actime;
  47   long modtime;
  48 };
  49 #endif
  50
  51 /* Avoid recursion with rpl_futimens or rpl_utimensat.  */
  52 #undef futimens
  53 #undef utimensat
  54
  55 /* Solaris 9 mistakenly succeeds when given a non-directory with a
  56    trailing slash.  Force the use of rpl_stat for a fix.  */
  57 #ifndef REPLACE_FUNC_STAT_FILE
  58 # define REPLACE_FUNC_STAT_FILE 0
  59 #endif
  60
  61 #if HAVE_UTIMENSAT || HAVE_FUTIMENS
  62 /* Cache variables for whether the utimensat syscall works; used to
  63    avoid calling the syscall if we know it will just fail with ENOSYS,
  64    and to avoid unnecessary work in massaging timestamps if the
  65    syscall will work.  Multiple variables are needed, to distinguish
  66    between the following scenarios on Linux:
  67    utimensat doesn't exist, or is in glibc but kernel 2.6.18 fails with ENOSYS
  68    kernel 2.6.22 and earlier rejects AT_SYMLINK_NOFOLLOW
  69    kernel 2.6.25 and earlier reject UTIME_NOW/UTIME_OMIT with non-zero tv_sec
  70    kernel 2.6.32 used with xfs or ntfs-3g fail to honor UTIME_OMIT
  71    utimensat completely works
  72    For each cache variable: 0 = unknown, 1 = yes, -1 = no.  */
  73 static int utimensat_works_really;
  74 static int lutimensat_works_really;
  75 #endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */
  76
  77 /* Validate the requested timestamps.  Return 0 if the resulting
  78    timespec can be used for utimensat (after possibly modifying it to
  79    work around bugs in utimensat).  Return a positive value if the
  80    timespec needs further adjustment based on stat results: 1 if any
  81    adjustment is needed for utimes, and 2 if any adjustment is needed
  82    for Linux utimensat.  Return -1, with errno set to EINVAL, if
  83    timespec is out of range.  */
  84 static int
  85 validate_timespec (struct timespec timespec[2])
  86 {
  87   int result = 0;
  88   int utime_omit_count = 0;
  89   if ((timespec[0].tv_nsec != UTIME_NOW
  90        && timespec[0].tv_nsec != UTIME_OMIT
  91        && ! (0 <= timespec[0].tv_nsec
  92              && timespec[0].tv_nsec < TIMESPEC_RESOLUTION))
  93       || (timespec[1].tv_nsec != UTIME_NOW
  94           && timespec[1].tv_nsec != UTIME_OMIT
  95           && ! (0 <= timespec[1].tv_nsec
  96                 && timespec[1].tv_nsec < TIMESPEC_RESOLUTION)))
  97     {
  98       errno = EINVAL;
  99       return -1;
 100     }
 101   /* Work around Linux kernel 2.6.25 bug, where utimensat fails with
 102      EINVAL if tv_sec is not 0 when using the flag values of tv_nsec.
 103      Flag a Linux kernel 2.6.32 bug, where an mtime of UTIME_OMIT
 104      fails to bump ctime.  */
 105   if (timespec[0].tv_nsec == UTIME_NOW
 106       || timespec[0].tv_nsec == UTIME_OMIT)
 107     {
 108       timespec[0].tv_sec = 0;
 109       result = 1;
 110       if (timespec[0].tv_nsec == UTIME_OMIT)
 111         utime_omit_count++;
 112     }
 113   if (timespec[1].tv_nsec == UTIME_NOW
 114       || timespec[1].tv_nsec == UTIME_OMIT)
 115     {
 116       timespec[1].tv_sec = 0;
 117       result = 1;
 118       if (timespec[1].tv_nsec == UTIME_OMIT)
 119         utime_omit_count++;
 120     }
 121   return result + (utime_omit_count == 1);
 122 }
 123
 124 /* Normalize any UTIME_NOW or UTIME_OMIT values in *TS, using stat
 125    buffer STATBUF to obtain the current timestamps of the file.  If
 126    both times are UTIME_NOW, set *TS to NULL (as this can avoid some
 127    permissions issues).  If both times are UTIME_OMIT, return true
 128    (nothing further beyond the prior collection of STATBUF is
 129    necessary); otherwise return false.  */
 130 static bool
 131 update_timespec (struct stat const *statbuf, struct timespec *ts[2])
 132 {
 133   struct timespec *timespec = *ts;
 134   if (timespec[0].tv_nsec == UTIME_OMIT
 135       && timespec[1].tv_nsec == UTIME_OMIT)
 136     return true;
 137   if (timespec[0].tv_nsec == UTIME_NOW
 138       && timespec[1].tv_nsec == UTIME_NOW)
 139     {
 140       *ts = NULL;
 141       return false;
 142     }
 143
 144   if (timespec[0].tv_nsec == UTIME_OMIT)
 145     timespec[0] = get_stat_atime (statbuf);
 146   else if (timespec[0].tv_nsec == UTIME_NOW)
 147     gettime (&timespec[0]);
 148
 149   if (timespec[1].tv_nsec == UTIME_OMIT)
 150     timespec[1] = get_stat_mtime (statbuf);
 151   else if (timespec[1].tv_nsec == UTIME_NOW)
 152     gettime (&timespec[1]);
 153
 154   return false;
 155 }
 156
 157 /* Set the access and modification timestamps of FD (a.k.a. FILE) to be
 158    TIMESPEC[0] and TIMESPEC[1], respectively.
 159    FD must be either negative -- in which case it is ignored --
 160    or a file descriptor that is open on FILE.
 161    If FD is nonnegative, then FILE can be NULL, which means
 162    use just futimes (or equivalent) instead of utimes (or equivalent),
 163    and fail if on an old system without futimes (or equivalent).
 164    If TIMESPEC is null, set the timestamps to the current time.
 165    Return 0 on success, -1 (setting errno) on failure.  */
 166
 167 int
 168 fdutimens (int fd, char const *file, struct timespec const timespec[2])
 169 {
 170   struct timespec adjusted_timespec[2];
 171   struct timespec *ts = timespec ? adjusted_timespec : NULL;
 172   int adjustment_needed = 0;
 173   struct stat st;
 174
 175   if (ts)
 176     {
 177       adjusted_timespec[0] = timespec[0];
 178       adjusted_timespec[1] = timespec[1];
 179       adjustment_needed = validate_timespec (ts);
 180     }
 181   if (adjustment_needed < 0)
 182     return -1;
 183
 184   /* Require that at least one of FD or FILE are potentially valid, to avoid
 185      a Linux bug where futimens (AT_FDCWD, NULL) changes "." rather
 186      than failing.  */
 187   if (fd < 0 && !file)
 188     {
 189       errno = EBADF;
 190       return -1;
 191     }
 192
 193   /* Some Linux-based NFS clients are buggy, and mishandle timestamps
 194      of files in NFS file systems in some cases.  We have no
 195      configure-time test for this, but please see
 196      <http://bugs.gentoo.org/show_bug.cgi?id=132673> for references to
 197      some of the problems with Linux 2.6.16.  If this affects you,
 198      compile with -DHAVE_BUGGY_NFS_TIME_STAMPS; this is reported to
 199      help in some cases, albeit at a cost in performance.  But you
 200      really should upgrade your kernel to a fixed version, since the
 201      problem affects many applications.  */
 202
 203 #if HAVE_BUGGY_NFS_TIME_STAMPS
 204   if (fd < 0)
 205     sync ();
 206   else
 207     fsync (fd);
 208 #endif
 209
 210   /* POSIX 2008 added two interfaces to set file timestamps with
 211      nanosecond resolution; newer Linux implements both functions via
 212      a single syscall.  We provide a fallback for ENOSYS (for example,
 213      compiling against Linux 2.6.25 kernel headers and glibc 2.7, but
 214      running on Linux 2.6.18 kernel).  */
 215 #if HAVE_UTIMENSAT || HAVE_FUTIMENS
 216   if (0 <= utimensat_works_really)
 217     {
 218       int result;
 219 # if __linux__ || __sun
 220       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
 221          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
 222          but work if both times are either explicitly specified or
 223          UTIME_NOW.  Work around it with a preparatory [f]stat prior
 224          to calling futimens/utimensat; fortunately, there is not much
 225          timing impact due to the extra syscall even on file systems
 226          where UTIME_OMIT would have worked.
 227
 228          The same bug occurs in Solaris 11.1 (Apr 2013).
 229
 230          FIXME: Simplify this for Linux in 2016 and for Solaris in
 231          2024, when file system bugs are no longer common.  */
 232       if (adjustment_needed == 2)
 233         {
 234           if (fd < 0 ? stat (file, &st) : fstat (fd, &st))
 235             return -1;
 236           if (ts[0].tv_nsec == UTIME_OMIT)
 237             ts[0] = get_stat_atime (&st);
 238           else if (ts[1].tv_nsec == UTIME_OMIT)
 239             ts[1] = get_stat_mtime (&st);
 240           /* Note that st is good, in case utimensat gives ENOSYS.  */
 241           adjustment_needed++;
 242         }
 243 # endif
 244 # if HAVE_UTIMENSAT
 245       if (fd < 0)
 246         {
 247           result = utimensat (AT_FDCWD, file, ts, 0);
 248 #  ifdef __linux__
 249           /* Work around a kernel bug:
 250              http://bugzilla.redhat.com/442352
 251              http://bugzilla.redhat.com/449910
 252              It appears that utimensat can mistakenly return 280 rather
 253              than -1 upon ENOSYS failure.
 254              FIXME: remove in 2010 or whenever the offending kernels
 255              are no longer in common use.  */
 256           if (0 < result)
 257             errno = ENOSYS;
 258 #  endif /* __linux__ */
 259           if (result == 0 || errno != ENOSYS)
 260             {
 261               utimensat_works_really = 1;
 262               return result;
 263             }
 264         }
 265 # endif /* HAVE_UTIMENSAT */
 266 # if HAVE_FUTIMENS
 267       if (0 <= fd)
 268         {
 269           result = futimens (fd, ts);
 270 #  ifdef __linux__
 271           /* Work around the same bug as above.  */
 272           if (0 < result)
 273             errno = ENOSYS;
 274 #  endif /* __linux__ */
 275           if (result == 0 || errno != ENOSYS)
 276             {
 277               utimensat_works_really = 1;
 278               return result;
 279             }
 280         }
 281 # endif /* HAVE_FUTIMENS */
 282     }
 283   utimensat_works_really = -1;
 284   lutimensat_works_really = -1;
 285 #endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */
 286
 287   /* The platform lacks an interface to set file timestamps with
 288      nanosecond resolution, so do the best we can, discarding any
 289      fractional part of the timestamp.  */
 290
 291   if (adjustment_needed || (REPLACE_FUNC_STAT_FILE && fd < 0))
 292     {
 293       if (adjustment_needed != 3
 294           && (fd < 0 ? stat (file, &st) : fstat (fd, &st)))
 295         return -1;
 296       if (ts && update_timespec (&st, &ts))
 297         return 0;
 298     }
 299
 300   {
 301 #if HAVE_FUTIMESAT || HAVE_WORKING_UTIMES
 302     struct timeval timeval[2];
 303     struct timeval *t;
 304     if (ts)
 305       {
 306         timeval[0].tv_sec = ts[0].tv_sec;
 307         timeval[0].tv_usec = ts[0].tv_nsec / 1000;
 308         timeval[1].tv_sec = ts[1].tv_sec;
 309         timeval[1].tv_usec = ts[1].tv_nsec / 1000;
 310         t = timeval;
 311       }
 312     else
 313       t = NULL;
 314
 315     if (fd < 0)
 316       {
 317 # if HAVE_FUTIMESAT
 318         return futimesat (AT_FDCWD, file, t);
 319 # endif
 320       }
 321     else
 322       {
 323         /* If futimesat or futimes fails here, don't try to speed things
 324            up by returning right away.  glibc can incorrectly fail with
 325            errno == ENOENT if /proc isn't mounted.  Also, Mandrake 10.0
 326            in high security mode doesn't allow ordinary users to read
 327            /proc/self, so glibc incorrectly fails with errno == EACCES.
 328            If errno == EIO, EPERM, or EROFS, it's probably safe to fail
 329            right away, but these cases are rare enough that they're not
 330            worth optimizing, and who knows what other messed-up systems
 331            are out there?  So play it safe and fall back on the code
 332            below.  */
 333
 334 # if (HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG) || HAVE_FUTIMES
 335 #  if HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG
 336 #   undef futimes
 337 #   define futimes(fd, t) futimesat (fd, NULL, t)
 338 #  endif
 339         if (futimes (fd, t) == 0)
 340           {
 341 #  if __linux__ && __GLIBC__
 342             /* Work around a longstanding glibc bug, still present as
 343                of 2010-12-27.  On older Linux kernels that lack both
 344                utimensat and utimes, glibc's futimes rounds instead of
 345                truncating when falling back on utime.  The same bug
 346                occurs in futimesat with a null 2nd arg.  */
 347             if (t)
 348               {
 349                 bool abig = 500000 <= t[0].tv_usec;
 350                 bool mbig = 500000 <= t[1].tv_usec;
 351                 if ((abig | mbig) && fstat (fd, &st) == 0)
 352                   {
 353                     /* If these two subtractions overflow, they'll
 354                        track the overflows inside the buggy glibc.  */
 355                     time_t adiff = st.st_atime - t[0].tv_sec;
 356                     time_t mdiff = st.st_mtime - t[1].tv_sec;
 357
 358                     struct timeval *tt = NULL;
 359                     struct timeval truncated_timeval[2];
 360                     truncated_timeval[0] = t[0];
 361                     truncated_timeval[1] = t[1];
 362                     if (abig && adiff == 1 && get_stat_atime_ns (&st) == 0)
 363                       {
 364                         tt = truncated_timeval;
 365                         tt[0].tv_usec = 0;
 366                       }
 367                     if (mbig && mdiff == 1 && get_stat_mtime_ns (&st) == 0)
 368                       {
 369                         tt = truncated_timeval;
 370                         tt[1].tv_usec = 0;
 371                       }
 372                     if (tt)
 373                       futimes (fd, tt);
 374                   }
 375               }
 376 #  endif
 377
 378             return 0;
 379           }
 380 # endif
 381       }
 382 #endif /* HAVE_FUTIMESAT || HAVE_WORKING_UTIMES */
 383
 384     if (!file)
 385       {
 386 #if ! ((HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG)          \
 387         || (HAVE_WORKING_UTIMES && HAVE_FUTIMES))
 388         errno = ENOSYS;
 389 #endif
 390         return -1;
 391       }
 392
 393 #if HAVE_WORKING_UTIMES
 394     return utimes (file, t);
 395 #else
 396     {
 397       struct utimbuf utimbuf;
 398       struct utimbuf *ut;
 399       if (ts)
 400         {
 401           utimbuf.actime = ts[0].tv_sec;
 402           utimbuf.modtime = ts[1].tv_sec;
 403           ut = &utimbuf;
 404         }
 405       else
 406         ut = NULL;
 407
 408       return utime (file, ut);
 409     }
 410 #endif /* !HAVE_WORKING_UTIMES */
 411   }
 412 }
 413
 414 /* Set the access and modification timestamps of FILE to be
 415    TIMESPEC[0] and TIMESPEC[1], respectively.  */
 416 int
 417 utimens (char const *file, struct timespec const timespec[2])
 418 {
 419   return fdutimens (-1, file, timespec);
 420 }
 421
 422 /* Set the access and modification timestamps of FILE to be
 423    TIMESPEC[0] and TIMESPEC[1], respectively, without dereferencing
 424    symlinks.  Fail with ENOSYS if the platform does not support
 425    changing symlink timestamps, but FILE was a symlink.  */
 426 int
 427 lutimens (char const *file, struct timespec const timespec[2])
 428 {
 429   struct timespec adjusted_timespec[2];
 430   struct timespec *ts = timespec ? adjusted_timespec : NULL;
 431   int adjustment_needed = 0;
 432   struct stat st;
 433
 434   if (ts)
 435     {
 436       adjusted_timespec[0] = timespec[0];
 437       adjusted_timespec[1] = timespec[1];
 438       adjustment_needed = validate_timespec (ts);
 439     }
 440   if (adjustment_needed < 0)
 441     return -1;
 442
 443   /* The Linux kernel did not support symlink timestamps until
 444      utimensat, in version 2.6.22, so we don't need to mimic
 445      fdutimens' worry about buggy NFS clients.  But we do have to
 446      worry about bogus return values.  */
 447
 448 #if HAVE_UTIMENSAT
 449   if (0 <= lutimensat_works_really)
 450     {
 451       int result;
 452 # if __linux__ || __sun
 453       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
 454          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
 455          but work if both times are either explicitly specified or
 456          UTIME_NOW.  Work around it with a preparatory lstat prior to
 457          calling utimensat; fortunately, there is not much timing
 458          impact due to the extra syscall even on file systems where
 459          UTIME_OMIT would have worked.
 460
 461          The same bug occurs in Solaris 11.1 (Apr 2013).
 462
 463          FIXME: Simplify this for Linux in 2016 and for Solaris in
 464          2024, when file system bugs are no longer common.  */
 465       if (adjustment_needed == 2)
 466         {
 467           if (lstat (file, &st))
 468             return -1;
 469           if (ts[0].tv_nsec == UTIME_OMIT)
 470             ts[0] = get_stat_atime (&st);
 471           else if (ts[1].tv_nsec == UTIME_OMIT)
 472             ts[1] = get_stat_mtime (&st);
 473           /* Note that st is good, in case utimensat gives ENOSYS.  */
 474           adjustment_needed++;
 475         }
 476 # endif
 477       result = utimensat (AT_FDCWD, file, ts, AT_SYMLINK_NOFOLLOW);
 478 # ifdef __linux__
 479       /* Work around a kernel bug:
 480          http://bugzilla.redhat.com/442352
 481          http://bugzilla.redhat.com/449910
 482          It appears that utimensat can mistakenly return 280 rather
 483          than -1 upon ENOSYS failure.
 484          FIXME: remove in 2010 or whenever the offending kernels
 485          are no longer in common use.  */
 486       if (0 < result)
 487         errno = ENOSYS;
 488 # endif
 489       if (result == 0 || errno != ENOSYS)
 490         {
 491           utimensat_works_really = 1;
 492           lutimensat_works_really = 1;
 493           return result;
 494         }
 495     }
 496   lutimensat_works_really = -1;
 497 #endif /* HAVE_UTIMENSAT */
 498
 499   /* The platform lacks an interface to set file timestamps with
 500      nanosecond resolution, so do the best we can, discarding any
 501      fractional part of the timestamp.  */
 502
 503   if (adjustment_needed || REPLACE_FUNC_STAT_FILE)
 504     {
 505       if (adjustment_needed != 3 && lstat (file, &st))
 506         return -1;
 507       if (ts && update_timespec (&st, &ts))
 508         return 0;
 509     }
 510
 511   /* On Linux, lutimes is a thin wrapper around utimensat, so there is
 512      no point trying lutimes if utimensat failed with ENOSYS.  */
 513 #if HAVE_LUTIMES && !HAVE_UTIMENSAT
 514   {
 515     struct timeval timeval[2];
 516     struct timeval *t;
 517     int result;
 518     if (ts)
 519       {
 520         timeval[0].tv_sec = ts[0].tv_sec;
 521         timeval[0].tv_usec = ts[0].tv_nsec / 1000;
 522         timeval[1].tv_sec = ts[1].tv_sec;
 523         timeval[1].tv_usec = ts[1].tv_nsec / 1000;
 524         t = timeval;
 525       }
 526     else
 527       t = NULL;
 528
 529     result = lutimes (file, t);
 530     if (result == 0 || errno != ENOSYS)
 531       return result;
 532   }
 533 #endif /* HAVE_LUTIMES && !HAVE_UTIMENSAT */
 534
 535   /* Out of luck for symlinks, but we still handle regular files.  */
 536   if (!(adjustment_needed || REPLACE_FUNC_STAT_FILE) && lstat (file, &st))
 537     return -1;
 538   if (!S_ISLNK (st.st_mode))
 539     return fdutimens (-1, file, ts);
 540   errno = ENOSYS;
 541   return -1;
 542 }