1  /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library 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 GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; see the file COPYING.LIB.  If
      16     not, see <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <unistd.h>
      19  #include <hurd.h>
      20  #include <hurd/paths.h>
      21  #include <hurd/fd.h>
      22  #include <fcntl.h>
      23  #include <string.h>
      24  
      25  /* Read the contents of the symbolic link FILE_NAME relative to FD into no more
      26     than LEN bytes of BUF.  The contents are not null-terminated.
      27     Returns the number of characters read, or -1 for errors.  */
      28  ssize_t
      29  __readlinkat (int fd, const char *file_name, char *buf, size_t len)
      30  {
      31    error_t err;
      32    file_t file_stat;
      33    struct stat64 st;
      34    enum retry_type doretry;
      35    char retryname[1024];
      36    file_t file;
      37    char *rbuf = buf;
      38    mach_msg_type_number_t nread = len;
      39  
      40    file_stat = __file_name_lookup_at (fd, 0, file_name, O_NOLINK, 0);
      41    if (file_stat == MACH_PORT_NULL)
      42      return -1;
      43  
      44    err = __io_stat (file_stat, &st);
      45    if (err)
      46      goto out;
      47    if (!S_ISLNK (st.st_mode))
      48      {
      49        err = EINVAL;
      50        goto out;
      51      }
      52  
      53    err = __dir_lookup (file_stat, "", O_READ | O_NOLINK,
      54                        0, &doretry, retryname, &file);
      55    if (err)
      56      goto out;
      57    if (doretry != FS_RETRY_NORMAL || retryname[0] != '\0')
      58      {
      59        err = EGRATUITOUS;
      60        goto out;
      61      }
      62  
      63    err = __io_read (file, &rbuf, &nread, 0, len);
      64    __mach_port_deallocate (__mach_task_self (), file);
      65    if (err)
      66      goto out;
      67  
      68    len = nread;
      69    if (rbuf != buf)
      70      {
      71        memcpy (buf, rbuf, len);
      72        __vm_deallocate (__mach_task_self (), (vm_address_t) rbuf, nread);
      73      }
      74  
      75  
      76   out:
      77    __mach_port_deallocate (__mach_task_self (), file_stat);
      78  
      79    return err ? __hurd_fail (err) : len;
      80  }
      81  weak_alias (__readlinkat, readlinkat)
      82  libc_hidden_def (readlinkat)