sysdeps/unix/sysv/linux/mkdirat.c

   1 /* Copyright (C) 2005-2014 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <stddef.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <kernel-features.h>
  25 #include <sysdep-cancel.h>
  26
  27
  28 /* Create a new directory with permission bits MODE.  But interpret
  29    relative PATH names relative to the directory associated with FD.  */
  30 int
  31 mkdirat (fd, file, mode)
  32      int fd;
  33      const char *file;
  34      mode_t mode;
  35 {
  36   int res;
  37
  38 #ifdef __NR_mkdirat
  39 #  ifndef __ASSUME_ATFCTS
  40   if (__have_atfcts >= 0)
  41 # endif
  42     {
  43       res = INLINE_SYSCALL (mkdirat, 3, fd, file, mode);
  44 # ifndef __ASSUME_ATFCTS
  45       if (res == -1 && errno == ENOSYS)
  46         __have_atfcts = -1;
  47       else
  48 # endif
  49         return res;
  50     }
  51 #endif
  52
  53 #ifndef __ASSUME_ATFCTS
  54   char *buf = NULL;
  55
  56   if (fd != AT_FDCWD && file[0] != '/')
  57     {
  58       size_t filelen = strlen (file);
  59       if (__builtin_expect (filelen == 0, 0))
  60         {
  61           __set_errno (ENOENT);
  62           return -1;
  63         }
  64
  65       static const char procfd[] = "/proc/self/fd/%d/%s";
  66       /* Buffer for the path name we are going to use.  It consists of
  67          - the string /proc/self/fd/
  68          - the file descriptor number
  69          - the file name provided.
  70          The final NUL is included in the sizeof.   A bit of overhead
  71          due to the format elements compensates for possible negative
  72          numbers.  */
  73       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  74       buf = alloca (buflen);
  75
  76       __snprintf (buf, buflen, procfd, fd, file);
  77       file = buf;
  78     }
  79
  80   INTERNAL_SYSCALL_DECL (err);
  81   res = INTERNAL_SYSCALL (mkdir, err, 2, file, mode);
  82
  83   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
  84     {
  85       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (res, err), fd, buf);
  86       res = -1;
  87     }
  88
  89   return res;
  90 #endif
  91 }