+
−/* Create a hard link relative to open directories.
+
−   Copyright (C) 2009 Free Software Foundation, Inc.
+
−
+
−   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 Eric Blake */
+
−
+
−#include <config.h>
+
−
+
−#include <unistd.h>
+
−
+
−#include <errno.h>
+
−#include <fcntl.h>
+
−#include <limits.h>
+
−#include <sys/stat.h>
+
−
+
−#include "areadlink.h"
+
−#include "dirname.h"
+
−#include "filenamecat.h"
+
−#include "openat-priv.h"
+
−
+
−#if HAVE_SYS_PARAM_H
+
−# include <sys/param.h>
+
−#endif
+
−#ifndef MAXSYMLINKS
+
−# ifdef SYMLOOP_MAX
+
−#  define MAXSYMLINKS SYMLOOP_MAX
+
−# else
+
−#  define MAXSYMLINKS 20
+
−# endif
+
−#endif
+
−
+
−/* Create a link.  If FILE1 is a symlink, either create a hardlink to
+
−   that symlink, or fake it by creating an identical symlink.  */
+
−#if LINK_FOLLOWS_SYMLINKS == 0
+
−# define link_immediate link
+
−#else
+
−static int
+
−link_immediate (char const *file1, char const *file2)
+
−{
+
−  char *target = areadlink (file1);
+
−  if (target)
+
−    {
+
−      /* A symlink cannot be modified in-place.  Therefore, creating
+
−         an identical symlink behaves like a hard link to a symlink,
+
−         except for incorrect st_ino and st_nlink.  However, we must
+
−         be careful of EXDEV.  */
+
−      struct stat st1;
+
−      struct stat st2;
+
−      char *dir = mdir_name (file2);
+
−      if (!dir)
+
−        {
+
−          free (target);
+
−          errno = ENOMEM;
+
−          return -1;
+
−        }
+
−      if (lstat (file1, &st1) == 0 && stat (dir, &st2) == 0)
+
−        {
+
−          if (st1.st_dev == st2.st_dev)
+
−            {
+
−              int result = symlink (target, file2);
+
−              int saved_errno = errno;
+
−              free (target);
+
−              free (dir);
+
−              errno = saved_errno;
+
−              return result;
+
−            }
+
−          free (target);
+
−          free (dir);
+
−          errno = EXDEV;
+
−          return -1;
+
−        }
+
−      free (target);
+
−      free (dir);
+
−    }
+
−  if (errno == ENOMEM)
+
−    return -1;
+
−  return link (file1, file2);
+
−}
+
−#endif
+
−
+
−/* Create a link.  If FILE1 is a symlink, create a hardlink to the
+
−   canonicalized file.  */
+
−#if 0 < LINK_FOLLOWS_SYMLINKS
+
−# define link_follow link
+
−#else
+
−static int
+
−link_follow (char const *file1, char const *file2)
+
−{
+
−  char *name = (char *) file1;
+
−  char *target;
+
−  int result;
+
−  int i = MAXSYMLINKS;
+
−
+
−  /* Using realpath or canonicalize_file_name is too heavy-handed: we
+
−     don't need an absolute name, and we don't need to resolve
+
−     intermediate symlinks, just the basename of each iteration.  */
+
−  while (i-- && (target = areadlink (name)))
+
−    {
+
−      if (IS_ABSOLUTE_FILE_NAME (target))
+
−        {
+
−          if (name != file1)
+
−            free (name);
+
−          name = target;
+
−        }
+
−      else
+
−        {
+
−          char *dir = mdir_name (name);
+
−          if (name != file1)
+
−            free (name);
+
−          if (!dir)
+
−            {
+
−              free (target);
+
−              errno = ENOMEM;
+
−              return -1;
+
−            }
+
−          name = mfile_name_concat (dir, target, NULL);
+
−          free (dir);
+
−          free (target);
+
−          if (!name)
+
−            {
+
−              errno = ENOMEM;
+
−              return -1;
+
−            }
+
−        }
+
−    }
+
−  if (i < 0)
+
−    {
+
−      target = NULL;
+
−      errno = ELOOP;
+
−    }
+
−  if (!target && errno != EINVAL)
+
−    {
+
−      if (name != file1)
+
−        {
+
−          int saved_errno = errno;
+
−          free (name);
+
−          errno = saved_errno;
+
−        }
+
−      return -1;
+
−    }
+
−  result = link (name, file2);
+
−  if (name != file1)
+
−    {
+
−      int saved_errno = errno;
+
−      free (name);
+
−      errno = saved_errno;
+
−    }
+
−  return result;
+
−}
+
−#endif
+
−
+
−/* Create a link to FILE1, in the directory open on descriptor FD1, to FILE2,
+
−   in the directory open on descriptor FD2.  If FILE1 is a symlink, FLAG
+
−   controls whether to dereference FILE1 first.  If possible, do it without
+
−   changing the working directory.  Otherwise, resort to using
+
−   save_cwd/fchdir, then rename/restore_cwd.  If either the save_cwd or
+
−   the restore_cwd fails, then give a diagnostic and exit nonzero.  */
+
−
+
−int
+
−linkat (int fd1, char const *file1, int fd2, char const *file2, int flag)
+
−{
+
−  if (flag & ~AT_SYMLINK_FOLLOW)
+
−    {
+
−      errno = EINVAL;
+
−      return -1;
+
−    }
+
−  return at_func2 (fd1, file1, fd2, file2,
+
−                   flag ? link_follow : link_immediate);
+
−}