lib/utimensat.c

   1 /* Set the access and modification time of a file relative to directory fd.
   2    Copyright (C) 2009-2020 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 <https://www.gnu.org/licenses/>.  */
  16
  17 /* written by Eric Blake */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include <sys/stat.h>
  23
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <stdlib.h>
  27
  28 #include "stat-time.h"
  29 #include "timespec.h"
  30 #include "utimens.h"
  31
  32 #if HAVE_UTIMENSAT
  33
  34 # undef utimensat
  35
  36 /* If we have a native utimensat, but are compiling this file, then
  37    utimensat was defined to rpl_utimensat by our replacement
  38    sys/stat.h.  We assume the native version might fail with ENOSYS,
  39    or succeed without properly affecting ctime (as is the case when
  40    using newer glibc but older Linux kernel).  In this scenario,
  41    rpl_utimensat checks whether the native version is usable, and
  42    local_utimensat provides the fallback manipulation.  */
  43
  44 static int local_utimensat (int, char const *, struct timespec const[2], int);
  45 # define AT_FUNC_NAME local_utimensat
  46
  47 /* Like utimensat, but work around native bugs.  */
  48
  49 int
  50 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
  51                int flag)
  52 {
  53 # if defined __linux__ || defined __sun
  54   struct timespec ts[2];
  55 # endif
  56
  57   /* See comments in utimens.c for details.  */
  58   static int utimensat_works_really; /* 0 = unknown, 1 = yes, -1 = no.  */
  59   if (0 <= utimensat_works_really)
  60     {
  61       int result;
  62 # if defined __linux__ || defined __sun
  63       struct stat st;
  64       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
  65          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
  66          but work if both times are either explicitly specified or
  67          UTIME_NOW.  Work around it with a preparatory [l]stat prior
  68          to calling utimensat; fortunately, there is not much timing
  69          impact due to the extra syscall even on file systems where
  70          UTIME_OMIT would have worked.
  71
  72          The same bug occurs in Solaris 11.1 (Apr 2013).
  73
  74          FIXME: Simplify this in 2024, when these file system bugs are
  75          no longer common on Gnulib target platforms.  */
  76       if (times && (times[0].tv_nsec == UTIME_OMIT
  77                     || times[1].tv_nsec == UTIME_OMIT))
  78         {
  79           if (fstatat (fd, file, &st, flag))
  80             return -1;
  81           if (times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
  82             return 0;
  83           if (times[0].tv_nsec == UTIME_OMIT)
  84             ts[0] = get_stat_atime (&st);
  85           else
  86             ts[0] = times[0];
  87           if (times[1].tv_nsec == UTIME_OMIT)
  88             ts[1] = get_stat_mtime (&st);
  89           else
  90             ts[1] = times[1];
  91           times = ts;
  92         }
  93 #  ifdef __hppa__
  94       /* Linux kernel 2.6.22.19 on hppa does not reject invalid tv_nsec
  95          values.  */
  96       else if (times
  97                && ((times[0].tv_nsec != UTIME_NOW
  98                     && ! (0 <= times[0].tv_nsec
  99                           && times[0].tv_nsec < TIMESPEC_HZ))
 100                    || (times[1].tv_nsec != UTIME_NOW
 101                        && ! (0 <= times[1].tv_nsec
 102                              && times[1].tv_nsec < TIMESPEC_HZ))))
 103         {
 104           errno = EINVAL;
 105           return -1;
 106         }
 107 #  endif
 108 # endif
 109       result = utimensat (fd, file, times, flag);
 110       /* Linux kernel 2.6.25 has a bug where it returns EINVAL for
 111          UTIME_NOW or UTIME_OMIT with non-zero tv_sec, which
 112          local_utimensat works around.  Meanwhile, EINVAL for a bad
 113          flag is indeterminate whether the native utimensat works, but
 114          local_utimensat will also reject it.  */
 115       if (result == -1 && errno == EINVAL && (flag & ~AT_SYMLINK_NOFOLLOW))
 116         return result;
 117       if (result == 0 || (errno != ENOSYS && errno != EINVAL))
 118         {
 119           utimensat_works_really = 1;
 120           return result;
 121         }
 122     }
 123   /* No point in trying openat/futimens, since on Linux, futimens is
 124      implemented with the same syscall as utimensat.  Only avoid the
 125      native utimensat due to an ENOSYS failure; an EINVAL error was
 126      data-dependent, and the next caller may pass valid data.  */
 127   if (0 <= utimensat_works_really && errno == ENOSYS)
 128     utimensat_works_really = -1;
 129   return local_utimensat (fd, file, times, flag);
 130 }
 131
 132 #else /* !HAVE_UTIMENSAT */
 133
 134 # define AT_FUNC_NAME utimensat
 135
 136 #endif /* !HAVE_UTIMENSAT */
 137
 138 /* Set the access and modification timestamps of FILE to be
 139    TIMESPEC[0] and TIMESPEC[1], respectively; relative to directory
 140    FD.  If flag is AT_SYMLINK_NOFOLLOW, change the times of a symlink,
 141    or fail with ENOSYS if not possible.  If TIMESPEC is null, set the
 142    timestamps to the current time.  If possible, do it without
 143    changing the working directory.  Otherwise, resort to using
 144    save_cwd/fchdir, then utimens/restore_cwd.  If either the save_cwd
 145    or the restore_cwd fails, then give a diagnostic and exit nonzero.
 146    Return 0 on success, -1 (setting errno) on failure.  */
 147
 148 /* AT_FUNC_NAME is now utimensat or local_utimensat.  */
 149 #define AT_FUNC_F1 lutimens
 150 #define AT_FUNC_F2 utimens
 151 #define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 152 #define AT_FUNC_POST_FILE_PARAM_DECLS , struct timespec const ts[2], int flag
 153 #define AT_FUNC_POST_FILE_ARGS        , ts
 154 #include "at-func.c"
 155 #undef AT_FUNC_NAME
 156 #undef AT_FUNC_F1
 157 #undef AT_FUNC_F2
 158 #undef AT_FUNC_USE_F1_COND
 159 #undef AT_FUNC_POST_FILE_PARAM_DECLS
 160 #undef AT_FUNC_POST_FILE_ARGS