sysdeps/unix/sysv/linux/renameat.c

   1 /* Copyright (C) 2005 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; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stdio.h>
  22 #include <sysdep.h>
  23
  24
  25 /* Rename the file OLD relative to OLDFD to NEW relative to NEWFD.  */
  26 int
  27 renameat (oldfd, old, newfd, new)
  28      int oldfd;
  29      const char *old;
  30      int newfd;
  31      const char *new;
  32 {
  33   static const char procfd[] = "/proc/self/fd/%d/%s";
  34   char *bufold = NULL;
  35
  36   if (oldfd != AT_FDCWD && old[0] != '/')
  37     {
  38       size_t filelen = strlen (old);
  39       /* Buffer for the path name we are going to use.  It consists of
  40          - the string /proc/self/fd/
  41          - the file descriptor number
  42          - the file name provided.
  43          The final NUL is included in the sizeof.   A bit of overhead
  44          due to the format elements compensates for possible negative
  45          numbers.  */
  46       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  47       bufold = alloca (buflen);
  48
  49       __snprintf (bufold, buflen, procfd, oldfd, old);
  50       old = bufold;
  51     }
  52
  53   char *bufnew = NULL;
  54
  55   if (newfd != AT_FDCWD && new[0] != '/')
  56     {
  57       size_t filelen = strlen (new);
  58       /* Buffer for the path name we are going to use.  It consists of
  59          - the string /proc/self/fd/
  60          - the file descriptor number
  61          - the file name provided.
  62          The final NUL is included in the sizeof.   A bit of overhead
  63          due to the format elements compensates for possible negative
  64          numbers.  */
  65       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  66       bufnew = alloca (buflen);
  67
  68       __snprintf (bufnew, buflen, procfd, newfd, new);
  69       new = bufnew;
  70     }
  71
  72   INTERNAL_SYSCALL_DECL (err);
  73
  74   int result = INTERNAL_SYSCALL (rename, err, 2, old,  new);
  75
  76   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  77     {
  78       int errval = INTERNAL_SYSCALL_ERRNO (result, err);
  79       if (errval == ENOTDIR && (bufnew != NULL || bufold != NULL))
  80         {
  81           /* This can mean either the file descriptor is invalid or
  82              /proc is not mounted.  */
  83           struct stat64 st;
  84
  85           if (bufnew != NULL)
  86             {
  87               if (__fxstat64 (_STAT_VER, newfd, &st) != 0)
  88                 /* errno is already set correctly.  */
  89                 return -1;
  90
  91               /* If /proc is not mounted there is nothing we can do.  */
  92               if (S_ISDIR (st.st_mode)
  93                   && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
  94                       || !S_ISDIR (st.st_mode)))
  95                 {
  96                   errval = ENOSYS;
  97                   goto out;
  98                 }
  99             }
 100
 101           if (bufold != NULL)
 102             {
 103               if (__fxstat64 (_STAT_VER, oldfd, &st) != 0)
 104                 /* errno is already set correctly.  */
 105                 return -1;
 106
 107               /* If /proc is not mounted there is nothing we can do.  */
 108               if (S_ISDIR (st.st_mode)
 109                   && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
 110                       || !S_ISDIR (st.st_mode)))
 111                 errval = ENOSYS;
 112             }
 113         }
 114
 115     out:
 116       __set_errno (errval);
 117       result = -1;
 118     }
 119
 120   return result;
 121 }