lib/utimens.c

   1 /* Set file access and modification times.
   2
   3    Copyright (C) 2003-2012 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 <assert.h>
  28 #include <errno.h>
  29 #include <fcntl.h>
  30 #include <stdbool.h>
  31 #include <sys/stat.h>
  32 #include <sys/time.h>
  33 #include <unistd.h>
  34
  35 #include "stat-time.h"
  36 #include "timespec.h"
  37
  38 #if HAVE_UTIME_H
  39 # include <utime.h>
  40 #endif
  41
  42 /* Some systems (even some that do have <utime.h>) don't declare this
  43    structure anywhere.  */
  44 #ifndef HAVE_STRUCT_UTIMBUF
  45 struct utimbuf
  46 {
  47   long actime;
  48   long modtime;
  49 };
  50 #endif
  51
  52 /* Avoid recursion with rpl_futimens or rpl_utimensat.  */
  53 #undef futimens
  54 #undef utimensat
  55
  56 /* Solaris 9 mistakenly succeeds when given a non-directory with a
  57    trailing slash.  Force the use of rpl_stat for a fix.  */
  58 #ifndef REPLACE_FUNC_STAT_FILE
  59 # define REPLACE_FUNC_STAT_FILE 0
  60 #endif
  61
  62 #if HAVE_UTIMENSAT || HAVE_FUTIMENS
  63 /* Cache variables for whether the utimensat syscall works; used to
  64    avoid calling the syscall if we know it will just fail with ENOSYS,
  65    and to avoid unnecessary work in massaging timestamps if the
  66    syscall will work.  Multiple variables are needed, to distinguish
  67    between the following scenarios on Linux:
  68    utimensat doesn't exist, or is in glibc but kernel 2.6.18 fails with ENOSYS
  69    kernel 2.6.22 and earlier rejects AT_SYMLINK_NOFOLLOW
  70    kernel 2.6.25 and earlier reject UTIME_NOW/UTIME_OMIT with non-zero tv_sec
  71    kernel 2.6.32 used with xfs or ntfs-3g fail to honor UTIME_OMIT
  72    utimensat completely works
  73    For each cache variable: 0 = unknown, 1 = yes, -1 = no.  */
  74 static int utimensat_works_really;
  75 static int lutimensat_works_really;
  76 #endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */
  77
  78 /* Validate the requested timestamps.  Return 0 if the resulting
  79    timespec can be used for utimensat (after possibly modifying it to
  80    work around bugs in utimensat).  Return a positive value if the
  81    timespec needs further adjustment based on stat results: 1 if any
  82    adjustment is needed for utimes, and 2 if any adjustment is needed
  83    for Linux utimensat.  Return -1, with errno set to EINVAL, if
  84    timespec is out of range.  */
  85 static int
  86 validate_timespec (struct timespec timespec[2])
  87 {
  88   int result = 0;
  89   int utime_omit_count = 0;
  90   assert (timespec);
  91   if ((timespec[0].tv_nsec != UTIME_NOW
  92        && timespec[0].tv_nsec != UTIME_OMIT
  93        && (timespec[0].tv_nsec < 0 || 1000000000 <= timespec[0].tv_nsec))
  94       || (timespec[1].tv_nsec != UTIME_NOW
  95           && timespec[1].tv_nsec != UTIME_OMIT
  96           && (timespec[1].tv_nsec < 0 || 1000000000 <= timespec[1].tv_nsec)))
  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 time stamps 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 time stamps 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 time stamps
 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__
 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.  FIXME: Simplify this in
 227          2012, when file system bugs are no longer common.  */
 228       if (adjustment_needed == 2)
 229         {
 230           if (fd < 0 ? stat (file, &st) : fstat (fd, &st))
 231             return -1;
 232           if (ts[0].tv_nsec == UTIME_OMIT)
 233             ts[0] = get_stat_atime (&st);
 234           else if (ts[1].tv_nsec == UTIME_OMIT)
 235             ts[1] = get_stat_mtime (&st);
 236           /* Note that st is good, in case utimensat gives ENOSYS.  */
 237           adjustment_needed++;
 238         }
 239 # endif /* __linux__ */
 240 # if HAVE_UTIMENSAT
 241       if (fd < 0)
 242         {
 243           result = utimensat (AT_FDCWD, file, ts, 0);
 244 #  ifdef __linux__
 245           /* Work around a kernel bug:
 246              http://bugzilla.redhat.com/442352
 247              http://bugzilla.redhat.com/449910
 248              It appears that utimensat can mistakenly return 280 rather
 249              than -1 upon ENOSYS failure.
 250              FIXME: remove in 2010 or whenever the offending kernels
 251              are no longer in common use.  */
 252           if (0 < result)
 253             errno = ENOSYS;
 254 #  endif /* __linux__ */
 255           if (result == 0 || errno != ENOSYS)
 256             {
 257               utimensat_works_really = 1;
 258               return result;
 259             }
 260         }
 261 # endif /* HAVE_UTIMENSAT */
 262 # if HAVE_FUTIMENS
 263       if (0 <= fd)
 264         {
 265           result = futimens (fd, ts);
 266 #  ifdef __linux__
 267           /* Work around the same bug as above.  */
 268           if (0 < result)
 269             errno = ENOSYS;
 270 #  endif /* __linux__ */
 271           if (result == 0 || errno != ENOSYS)
 272             {
 273               utimensat_works_really = 1;
 274               return result;
 275             }
 276         }
 277 # endif /* HAVE_FUTIMENS */
 278     }
 279   utimensat_works_really = -1;
 280   lutimensat_works_really = -1;
 281 #endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */
 282
 283   /* The platform lacks an interface to set file timestamps with
 284      nanosecond resolution, so do the best we can, discarding any
 285      fractional part of the timestamp.  */
 286
 287   if (adjustment_needed || (REPLACE_FUNC_STAT_FILE && fd < 0))
 288     {
 289       if (adjustment_needed != 3
 290           && (fd < 0 ? stat (file, &st) : fstat (fd, &st)))
 291         return -1;
 292       if (ts && update_timespec (&st, &ts))
 293         return 0;
 294     }
 295
 296   {
 297 #if HAVE_FUTIMESAT || HAVE_WORKING_UTIMES
 298     struct timeval timeval[2];
 299     struct timeval *t;
 300     if (ts)
 301       {
 302         timeval[0].tv_sec = ts[0].tv_sec;
 303         timeval[0].tv_usec = ts[0].tv_nsec / 1000;
 304         timeval[1].tv_sec = ts[1].tv_sec;
 305         timeval[1].tv_usec = ts[1].tv_nsec / 1000;
 306         t = timeval;
 307       }
 308     else
 309       t = NULL;
 310
 311     if (fd < 0)
 312       {
 313 # if HAVE_FUTIMESAT
 314         return futimesat (AT_FDCWD, file, t);
 315 # endif
 316       }
 317     else
 318       {
 319         /* If futimesat or futimes fails here, don't try to speed things
 320            up by returning right away.  glibc can incorrectly fail with
 321            errno == ENOENT if /proc isn't mounted.  Also, Mandrake 10.0
 322            in high security mode doesn't allow ordinary users to read
 323            /proc/self, so glibc incorrectly fails with errno == EACCES.
 324            If errno == EIO, EPERM, or EROFS, it's probably safe to fail
 325            right away, but these cases are rare enough that they're not
 326            worth optimizing, and who knows what other messed-up systems
 327            are out there?  So play it safe and fall back on the code
 328            below.  */
 329
 330 # if (HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG) || HAVE_FUTIMES
 331 #  if HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG
 332 #   undef futimes
 333 #   define futimes(fd, t) futimesat (fd, NULL, t)
 334 #  endif
 335         if (futimes (fd, t) == 0)
 336           {
 337 #  if __linux__ && __GLIBC__
 338             /* Work around a longstanding glibc bug, still present as
 339                of 2010-12-27.  On older Linux kernels that lack both
 340                utimensat and utimes, glibc's futimes rounds instead of
 341                truncating when falling back on utime.  The same bug
 342                occurs in futimesat with a null 2nd arg.  */
 343             if (t)
 344               {
 345                 bool abig = 500000 <= t[0].tv_usec;
 346                 bool mbig = 500000 <= t[1].tv_usec;
 347                 if ((abig | mbig) && fstat (fd, &st) == 0)
 348                   {
 349                     /* If these two subtractions overflow, they'll
 350                        track the overflows inside the buggy glibc.  */
 351                     time_t adiff = st.st_atime - t[0].tv_sec;
 352                     time_t mdiff = st.st_mtime - t[1].tv_sec;
 353
 354                     struct timeval *tt = NULL;
 355                     struct timeval truncated_timeval[2];
 356                     truncated_timeval[0] = t[0];
 357                     truncated_timeval[1] = t[1];
 358                     if (abig && adiff == 1 && get_stat_atime_ns (&st) == 0)
 359                       {
 360                         tt = truncated_timeval;
 361                         tt[0].tv_usec = 0;
 362                       }
 363                     if (mbig && mdiff == 1 && get_stat_mtime_ns (&st) == 0)
 364                       {
 365                         tt = truncated_timeval;
 366                         tt[1].tv_usec = 0;
 367                       }
 368                     if (tt)
 369                       futimes (fd, tt);
 370                   }
 371               }
 372 #  endif
 373
 374             return 0;
 375           }
 376 # endif
 377       }
 378 #endif /* HAVE_FUTIMESAT || HAVE_WORKING_UTIMES */
 379
 380     if (!file)
 381       {
 382 #if ! ((HAVE_FUTIMESAT && !FUTIMESAT_NULL_BUG)          \
 383         || (HAVE_WORKING_UTIMES && HAVE_FUTIMES))
 384         errno = ENOSYS;
 385 #endif
 386         return -1;
 387       }
 388
 389 #if HAVE_WORKING_UTIMES
 390     return utimes (file, t);
 391 #else
 392     {
 393       struct utimbuf utimbuf;
 394       struct utimbuf *ut;
 395       if (ts)
 396         {
 397           utimbuf.actime = ts[0].tv_sec;
 398           utimbuf.modtime = ts[1].tv_sec;
 399           ut = &utimbuf;
 400         }
 401       else
 402         ut = NULL;
 403
 404       return utime (file, ut);
 405     }
 406 #endif /* !HAVE_WORKING_UTIMES */
 407   }
 408 }
 409
 410 /* Set the access and modification time stamps of FILE to be
 411    TIMESPEC[0] and TIMESPEC[1], respectively.  */
 412 int
 413 utimens (char const *file, struct timespec const timespec[2])
 414 {
 415   return fdutimens (-1, file, timespec);
 416 }
 417
 418 /* Set the access and modification time stamps of FILE to be
 419    TIMESPEC[0] and TIMESPEC[1], respectively, without dereferencing
 420    symlinks.  Fail with ENOSYS if the platform does not support
 421    changing symlink timestamps, but FILE was a symlink.  */
 422 int
 423 lutimens (char const *file, struct timespec const timespec[2])
 424 {
 425   struct timespec adjusted_timespec[2];
 426   struct timespec *ts = timespec ? adjusted_timespec : NULL;
 427   int adjustment_needed = 0;
 428   struct stat st;
 429
 430   if (ts)
 431     {
 432       adjusted_timespec[0] = timespec[0];
 433       adjusted_timespec[1] = timespec[1];
 434       adjustment_needed = validate_timespec (ts);
 435     }
 436   if (adjustment_needed < 0)
 437     return -1;
 438
 439   /* The Linux kernel did not support symlink timestamps until
 440      utimensat, in version 2.6.22, so we don't need to mimic
 441      fdutimens' worry about buggy NFS clients.  But we do have to
 442      worry about bogus return values.  */
 443
 444 #if HAVE_UTIMENSAT
 445   if (0 <= lutimensat_works_really)
 446     {
 447       int result;
 448 # if __linux__
 449       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
 450          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
 451          but work if both times are either explicitly specified or
 452          UTIME_NOW.  Work around it with a preparatory lstat prior to
 453          calling utimensat; fortunately, there is not much timing
 454          impact due to the extra syscall even on file systems where
 455          UTIME_OMIT would have worked.  FIXME: Simplify this in 2012,
 456          when file system bugs are no longer common.  */
 457       if (adjustment_needed == 2)
 458         {
 459           if (lstat (file, &st))
 460             return -1;
 461           if (ts[0].tv_nsec == UTIME_OMIT)
 462             ts[0] = get_stat_atime (&st);
 463           else if (ts[1].tv_nsec == UTIME_OMIT)
 464             ts[1] = get_stat_mtime (&st);
 465           /* Note that st is good, in case utimensat gives ENOSYS.  */
 466           adjustment_needed++;
 467         }
 468 # endif /* __linux__ */
 469       result = utimensat (AT_FDCWD, file, ts, AT_SYMLINK_NOFOLLOW);
 470 # ifdef __linux__
 471       /* Work around a kernel bug:
 472          http://bugzilla.redhat.com/442352
 473          http://bugzilla.redhat.com/449910
 474          It appears that utimensat can mistakenly return 280 rather
 475          than -1 upon ENOSYS failure.
 476          FIXME: remove in 2010 or whenever the offending kernels
 477          are no longer in common use.  */
 478       if (0 < result)
 479         errno = ENOSYS;
 480 # endif
 481       if (result == 0 || errno != ENOSYS)
 482         {
 483           utimensat_works_really = 1;
 484           lutimensat_works_really = 1;
 485           return result;
 486         }
 487     }
 488   lutimensat_works_really = -1;
 489 #endif /* HAVE_UTIMENSAT */
 490
 491   /* The platform lacks an interface to set file timestamps with
 492      nanosecond resolution, so do the best we can, discarding any
 493      fractional part of the timestamp.  */
 494
 495   if (adjustment_needed || REPLACE_FUNC_STAT_FILE)
 496     {
 497       if (adjustment_needed != 3 && lstat (file, &st))
 498         return -1;
 499       if (ts && update_timespec (&st, &ts))
 500         return 0;
 501     }
 502
 503   /* On Linux, lutimes is a thin wrapper around utimensat, so there is
 504      no point trying lutimes if utimensat failed with ENOSYS.  */
 505 #if HAVE_LUTIMES && !HAVE_UTIMENSAT
 506   {
 507     struct timeval timeval[2];
 508     struct timeval *t;
 509     int result;
 510     if (ts)
 511       {
 512         timeval[0].tv_sec = ts[0].tv_sec;
 513         timeval[0].tv_usec = ts[0].tv_nsec / 1000;
 514         timeval[1].tv_sec = ts[1].tv_sec;
 515         timeval[1].tv_usec = ts[1].tv_nsec / 1000;
 516         t = timeval;
 517       }
 518     else
 519       t = NULL;
 520
 521     result = lutimes (file, t);
 522     if (result == 0 || errno != ENOSYS)
 523       return result;
 524   }
 525 #endif /* HAVE_LUTIMES && !HAVE_UTIMENSAT */
 526
 527   /* Out of luck for symlinks, but we still handle regular files.  */
 528   if (!(adjustment_needed || REPLACE_FUNC_STAT_FILE) && lstat (file, &st))
 529     return -1;
 530   if (!S_ISLNK (st.st_mode))
 531     return fdutimens (-1, file, ts);
 532   errno = ENOSYS;
 533   return -1;
 534 }