at-func.c 4.3 KB
Newer Older
1
/* Define at-style functions like fstatat, unlinkat, fchownat, etc.
Paul Eggert's avatar
Paul Eggert committed
2
   Copyright (C) 2006, 2009-2013 Free Software Foundation, Inc.
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* written by Jim Meyering */

#include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */

#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
# include <errno.h>
# ifndef ENOTSUP
#  define ENOTSUP EINVAL
# endif
#else
# include "openat.h"
# include "openat-priv.h"
# include "save-cwd.h"
#endif

#ifdef AT_FUNC_USE_F1_COND
# define CALL_FUNC(F)                           \
  (flag == AT_FUNC_USE_F1_COND                  \
    ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS)     \
    : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS))
# define VALIDATE_FLAG(F)                       \
  if (flag & ~AT_FUNC_USE_F1_COND)              \
    {                                           \
      errno = EINVAL;                           \
      return FUNC_FAIL;                         \
    }
#else
# define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS))
# define VALIDATE_FLAG(F) /* empty */
#endif

#ifdef AT_FUNC_RESULT
# define FUNC_RESULT AT_FUNC_RESULT
#else
# define FUNC_RESULT int
#endif

#ifdef AT_FUNC_FAIL
# define FUNC_FAIL AT_FUNC_FAIL
#else
# define FUNC_FAIL -1
#endif

/* Call AT_FUNC_F1 to operate on FILE, which is in the directory
   open on descriptor FD.  If AT_FUNC_USE_F1_COND is defined to a value,
   AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag;
   call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than
   AT_FUNC_USE_F1_COND.  Return int and fail with -1 unless AT_FUNC_RESULT
   or AT_FUNC_FAIL are defined.  If possible, do it without changing the
   working directory.  Otherwise, resort to using save_cwd/fchdir,
   then AT_FUNC_F?/restore_cwd.  If either the save_cwd or the restore_cwd
   fails, then give a diagnostic and exit nonzero.  */
FUNC_RESULT
AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS)
{
  VALIDATE_FLAG (flag);

  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
    return CALL_FUNC (file);

#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
  errno = ENOTSUP;
  return FUNC_FAIL;
#else
  {
  /* Be careful to choose names unlikely to conflict with
     AT_FUNC_POST_FILE_PARAM_DECLS.  */
  struct saved_cwd saved_cwd;
  int saved_errno;
  FUNC_RESULT err;

  {
    char proc_buf[OPENAT_BUFFER_SIZE];
    char *proc_file = openat_proc_name (proc_buf, fd, file);
    if (proc_file)
      {
        FUNC_RESULT proc_result = CALL_FUNC (proc_file);
        int proc_errno = errno;
        if (proc_file != proc_buf)
          free (proc_file);
        /* If the syscall succeeds, or if it fails with an unexpected
           errno value, then return right away.  Otherwise, fall through
           and resort to using save_cwd/restore_cwd.  */
        if (FUNC_FAIL != proc_result)
          return proc_result;
        if (! EXPECTED_ERRNO (proc_errno))
          {
            errno = proc_errno;
            return proc_result;
          }
      }
  }

  if (save_cwd (&saved_cwd) != 0)
    openat_save_fail (errno);
  if (0 <= fd && fd == saved_cwd.desc)
    {
      /* If saving the working directory collides with the user's
         requested fd, then the user's fd must have been closed to
         begin with.  */
      free_cwd (&saved_cwd);
      errno = EBADF;
      return FUNC_FAIL;
    }

  if (fchdir (fd) != 0)
    {
      saved_errno = errno;
      free_cwd (&saved_cwd);
      errno = saved_errno;
      return FUNC_FAIL;
    }

  err = CALL_FUNC (file);
  saved_errno = (err == FUNC_FAIL ? errno : 0);

  if (restore_cwd (&saved_cwd) != 0)
    openat_restore_fail (errno);

  free_cwd (&saved_cwd);

  if (saved_errno)
    errno = saved_errno;
  return err;
  }
#endif
}
#undef CALL_FUNC
#undef FUNC_RESULT
#undef FUNC_FAIL