lib/utimensat.c

   1 /* Set the access and modification time of a file relative to directory fd.
   2    Copyright (C) 2009-2017 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* written by Eric Blake */
  18
  19 #include <config.h>
  20
  21 #include <sys/stat.h>
  22
  23 #include <errno.h>
  24 #include <fcntl.h>
  25
  26 #include "stat-time.h"
  27 #include "timespec.h"
  28 #include "utimens.h"
  29
  30 #if HAVE_UTIMENSAT
  31
  32 # undef utimensat
  33
  34 /* If we have a native utimensat, but are compiling this file, then
  35    utimensat was defined to rpl_utimensat by our replacement
  36    sys/stat.h.  We assume the native version might fail with ENOSYS,
  37    or succeed without properly affecting ctime (as is the case when
  38    using newer glibc but older Linux kernel).  In this scenario,
  39    rpl_utimensat checks whether the native version is usable, and
  40    local_utimensat provides the fallback manipulation.  */
  41
  42 static int local_utimensat (int, char const *, struct timespec const[2], int);
  43 # define AT_FUNC_NAME local_utimensat
  44
  45 /* Like utimensat, but work around native bugs.  */
  46
  47 int
  48 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
  49                int flag)
  50 {
  51 # if defined __linux__ || defined __sun
  52   struct timespec ts[2];
  53 # endif
  54
  55   /* See comments in utimens.c for details.  */
  56   static int utimensat_works_really; /* 0 = unknown, 1 = yes, -1 = no.  */
  57   if (0 <= utimensat_works_really)
  58     {
  59       int result;
  60 # if defined __linux__ || defined __sun
  61       struct stat st;
  62       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
  63          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
  64          but work if both times are either explicitly specified or
  65          UTIME_NOW.  Work around it with a preparatory [l]stat prior
  66          to calling utimensat; fortunately, there is not much timing
  67          impact due to the extra syscall even on file systems where
  68          UTIME_OMIT would have worked.
  69
  70          The same bug occurs in Solaris 11.1 (Apr 2013).
  71
  72          FIXME: Simplify this in 2024, when these file system bugs are
  73          no longer common on Gnulib target platforms.  */
  74       if (times && (times[0].tv_nsec == UTIME_OMIT
  75                     || times[1].tv_nsec == UTIME_OMIT))
  76         {
  77           if (fstatat (fd, file, &st, flag))
  78             return -1;
  79           if (times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
  80             return 0;
  81           if (times[0].tv_nsec == UTIME_OMIT)
  82             ts[0] = get_stat_atime (&st);
  83           else
  84             ts[0] = times[0];
  85           if (times[1].tv_nsec == UTIME_OMIT)
  86             ts[1] = get_stat_mtime (&st);
  87           else
  88             ts[1] = times[1];
  89           times = ts;
  90         }
  91 #  ifdef __hppa__
  92       /* Linux kernel 2.6.22.19 on hppa does not reject invalid tv_nsec
  93          values.  */
  94       else if (times
  95                && ((times[0].tv_nsec != UTIME_NOW
  96                     && ! (0 <= times[0].tv_nsec
  97                           && times[0].tv_nsec < TIMESPEC_RESOLUTION))
  98                    || (times[1].tv_nsec != UTIME_NOW
  99                        && ! (0 <= times[1].tv_nsec
 100                              && times[1].tv_nsec < TIMESPEC_RESOLUTION))))
 101         {
 102           errno = EINVAL;
 103           return -1;
 104         }
 105 #  endif
 106 # endif
 107       result = utimensat (fd, file, times, flag);
 108       /* Linux kernel 2.6.25 has a bug where it returns EINVAL for
 109          UTIME_NOW or UTIME_OMIT with non-zero tv_sec, which
 110          local_utimensat works around.  Meanwhile, EINVAL for a bad
 111          flag is indeterminate whether the native utimensat works, but
 112          local_utimensat will also reject it.  */
 113       if (result == -1 && errno == EINVAL && (flag & ~AT_SYMLINK_NOFOLLOW))
 114         return result;
 115       if (result == 0 || (errno != ENOSYS && errno != EINVAL))
 116         {
 117           utimensat_works_really = 1;
 118           return result;
 119         }
 120     }
 121   /* No point in trying openat/futimens, since on Linux, futimens is
 122      implemented with the same syscall as utimensat.  Only avoid the
 123      native utimensat due to an ENOSYS failure; an EINVAL error was
 124      data-dependent, and the next caller may pass valid data.  */
 125   if (0 <= utimensat_works_really && errno == ENOSYS)
 126     utimensat_works_really = -1;
 127   return local_utimensat (fd, file, times, flag);
 128 }
 129
 130 #else /* !HAVE_UTIMENSAT */
 131
 132 # define AT_FUNC_NAME utimensat
 133
 134 #endif /* !HAVE_UTIMENSAT */
 135
 136 /* Set the access and modification timestamps of FILE to be
 137    TIMESPEC[0] and TIMESPEC[1], respectively; relative to directory
 138    FD.  If flag is AT_SYMLINK_NOFOLLOW, change the times of a symlink,
 139    or fail with ENOSYS if not possible.  If TIMESPEC is null, set the
 140    timestamps to the current time.  If possible, do it without
 141    changing the working directory.  Otherwise, resort to using
 142    save_cwd/fchdir, then utimens/restore_cwd.  If either the save_cwd
 143    or the restore_cwd fails, then give a diagnostic and exit nonzero.
 144    Return 0 on success, -1 (setting errno) on failure.  */
 145
 146 /* AT_FUNC_NAME is now utimensat or local_utimensat.  */
 147 #define AT_FUNC_F1 lutimens
 148 #define AT_FUNC_F2 utimens
 149 #define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 150 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct timespec const ts[2], int flag
 151 #define AT_FUNC_POST_FILE_ARGS        , ts
 152 #include "at-func.c"
 153 #undef AT_FUNC_NAME
 154 #undef AT_FUNC_F1
 155 #undef AT_FUNC_F2
 156 #undef AT_FUNC_USE_F1_COND
 157 #undef AT_FUNC_POST_FILE_PARAM_DECLS
 158 #undef AT_FUNC_POST_FILE_ARGS