Line data    Source code

       1             : /* Create /proc/self/fd-related names for subfiles of open directories.
       2             : 
       3             :    Copyright (C) 2006 Free Software Foundation, Inc.
       4             : 
       5             :    This program is free software: you can redistribute it and/or modify
       6             :    it under the terms of the GNU General Public License as published by
       7             :    the Free Software Foundation; either version 3 of the License, or
       8             :    (at your option) any later version.
       9             : 
      10             :    This program is distributed in the hope that it will be useful,
      11             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      12             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      13             :    GNU General Public License for more details.
      14             : 
      15             :    You should have received a copy of the GNU General Public License
      16             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
      17             : 
      18             : /* Written by Paul Eggert.  */
      19             : 
      20             : #include <config.h>
      21             : 
      22             : #include "openat-priv.h"
      23             : 
      24             : #include <sys/types.h>
      25             : #include <sys/stat.h>
      26             : #include <fcntl.h>
      27             : 
      28             : #include <stdio.h>
      29             : #include <string.h>
      30             : 
      31             : #include "dirname.h"
      32             : #include "intprops.h"
      33             : #include "same-inode.h"
      34             : #include "xalloc.h"
      35             : 
      36             : /* The results of open() in this file are not used with fchdir,
      37             :    therefore save some unnecessary work in fchdir.c.  */
      38             : #undef open
      39             : #undef close
      40             : 
      41             : #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
      42             : 
      43             : #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
      44             :   (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
      45             :    + INT_STRLEN_BOUND (int) + (len) + 1)
      46             : 
      47             : 
      48             : /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
      49             :    respectively for %d and %s.  If successful, return BUF if the
      50             :    result fits in BUF, dynamically allocated memory otherwise.  But
      51             :    return NULL if /proc is not reliable.  */
      52             : char *
      53      133378 : openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
      54             : {
      55             :   static int proc_status = 0;
      56             : 
      57      133378 :   if (! proc_status)
      58             :     {
      59             :       /* Set PROC_STATUS to a positive value if /proc/self/fd is
      60             :          reliable, and a negative value otherwise.  Solaris 10
      61             :          /proc/self/fd mishandles "..", and any file name might expand
      62             :          to ".." after symbolic link expansion, so avoid /proc/self/fd
      63             :          if it mishandles "..".  Solaris 10 has openat, but this
      64             :          problem is exhibited on code that built on Solaris 8 and
      65             :          running on Solaris 10.  */
      66             : 
      67           1 :       int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
      68           1 :       if (proc_self_fd < 0)
      69           0 :         proc_status = -1;
      70             :       else
      71             :         {
      72             :           struct stat proc_self_fd_dotdot_st;
      73             :           struct stat proc_self_st;
      74             :           char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
      75           1 :           sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
      76           1 :           proc_status =
      77           1 :             ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
      78           1 :               && stat ("/proc/self", &proc_self_st) == 0
      79           1 :               && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
      80           2 :              ? 1 : -1);
      81           1 :           close (proc_self_fd);
      82             :         }
      83             :     }
      84             : 
      85      133378 :   if (proc_status < 0)
      86           0 :     return NULL;
      87             :   else
      88             :     {
      89      133378 :       size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
      90      133378 :       char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
      91      133378 :       sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
      92      133378 :       return result;
      93             :     }
      94             : }