sysdeps/unix/sysv/linux/unlinkat.c

   1 /* unlinkat -- Remove a link by relative name.
   2    Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sysdep.h>
  26 #include <unistd.h>
  27 #include <kernel-features.h>
  28
  29
  30 /* Remove the link named NAME.  */
  31 int
  32 unlinkat (fd, file, flag)
  33      int fd;
  34      const char *file;
  35      int flag;
  36 {
  37   int result;
  38
  39 #ifdef __NR_unlinkat
  40 # ifndef __ASSUME_ATFCTS
  41   if (__have_atfcts >= 0)
  42 # endif
  43     {
  44       result = INLINE_SYSCALL (unlinkat, 3, fd, file, flag);
  45 # ifndef __ASSUME_ATFCTS
  46       if (result == -1 && errno == ENOSYS)
  47         __have_atfcts = -1;
  48       else
  49 # endif
  50         return result;
  51     }
  52 #endif
  53
  54 #ifndef __ASSUME_ATFCTS
  55   if (flag & ~AT_REMOVEDIR)
  56     {
  57       __set_errno (EINVAL);
  58       return -1;
  59     }
  60
  61   char *buf = NULL;
  62
  63   if (fd != AT_FDCWD && file[0] != '/')
  64     {
  65       size_t filelen = strlen (file);
  66       if (__builtin_expect (filelen == 0, 0))
  67         {
  68           __set_errno (ENOENT);
  69           return -1;
  70         }
  71
  72       static const char procfd[] = "/proc/self/fd/%d/%s";
  73       /* Buffer for the path name we are going to use.  It consists of
  74          - the string /proc/self/fd/
  75          - the file descriptor number
  76          - the file name provided.
  77          The final NUL is included in the sizeof.   A bit of overhead
  78          due to the format elements compensates for possible negative
  79          numbers.  */
  80       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  81       buf = __alloca (buflen);
  82
  83       __snprintf (buf, buflen, procfd, fd, file);
  84       file = buf;
  85     }
  86
  87   INTERNAL_SYSCALL_DECL (err);
  88
  89   if (flag & AT_REMOVEDIR)
  90     result = INTERNAL_SYSCALL (rmdir, err, 1, file);
  91   else
  92     result = INTERNAL_SYSCALL (unlink, err, 1, file);
  93
  94   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  95     {
  96       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
  97       result = -1;
  98     }
  99
 100   return result;
 101 #endif
 102 }