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    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 time stamps 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    time stamps 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