sysdeps/unix/sysv/linux/xmknodat.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 <string.h>
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <sys/sysmacros.h>
  26
  27 #include <sysdep.h>
  28 #include <sys/syscall.h>
  29 #include <bp-checks.h>
  30
  31 /* Create a device file named PATH relative to FD, with permission and
  32    special bits MODE and device number DEV (which can be constructed
  33    from major and minor device numbers with the `makedev' macro above).  */
  34 int
  35 __xmknodat (int vers, int fd, const char *file, mode_t mode, dev_t *dev)
  36 {
  37   if (vers != _MKNOD_VER)
  38     {
  39       __set_errno (EINVAL);
  40       return -1;
  41     }
  42
  43   char *buf = NULL;
  44
  45   if (fd != AT_FDCWD && file[0] != '/')
  46     {
  47       size_t filelen = strlen (file);
  48       static const char procfd[] = "/proc/self/fd/%d/%s";
  49       /* Buffer for the path name we are going to use.  It consists of
  50          - the string /proc/self/fd/
  51          - the file descriptor number
  52          - the file name provided.
  53          The final NUL is included in the sizeof.   A bit of overhead
  54          due to the format elements compensates for possible negative
  55          numbers.  */
  56       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  57       buf = alloca (buflen);
  58
  59       __snprintf (buf, buflen, procfd, fd, file);
  60       file = buf;
  61     }
  62
  63   /* We must convert the value to dev_t type used by the kernel.  */
  64   unsigned long long int k_dev =  (*dev) & ((1ULL << 32) - 1);
  65   if (k_dev != *dev)
  66     {
  67       __set_errno (EINVAL);
  68       return -1;
  69     }
  70
  71   return INLINE_SYSCALL (mknod, 3, CHECK_STRING (file), mode,
  72                          (unsigned int) k_dev);
  73 }
  74
  75 libc_hidden_def (__xmknodat)