1 /* Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
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.
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.
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/>. */
26 #include <kernel-features.h>
29 /* Read the contents of the symbolic link PATH relative to FD into no
30 more than LEN bytes of BUF. */
32 readlinkat (fd
, path
, buf
, len
)
40 #ifdef __NR_readlinkat
41 # ifndef __ASSUME_ATFCTS
42 if (__have_atfcts
>= 0)
45 result
= INLINE_SYSCALL (readlinkat
, 4, fd
, path
, buf
, len
);
46 # ifndef __ASSUME_ATFCTS
47 if (result
== -1 && errno
== ENOSYS
)
55 #ifndef __ASSUME_ATFCTS
58 if (fd
!= AT_FDCWD
&& path
[0] != '/')
60 size_t pathlen
= strlen (path
);
61 if (__builtin_expect (pathlen
== 0, 0))
67 static const char procfd
[] = "/proc/self/fd/%d/%s";
68 /* Buffer for the path name we are going to use. It consists of
69 - the string /proc/self/fd/
70 - the file descriptor number
71 - the file name provided.
72 The final NUL is included in the sizeof. A bit of overhead
73 due to the format elements compensates for possible negative
75 size_t buflen
= sizeof (procfd
) + sizeof (int) * 3 + pathlen
;
76 pathbuf
= __alloca (buflen
);
78 __snprintf (pathbuf
, buflen
, procfd
, fd
, path
);
82 INTERNAL_SYSCALL_DECL (err
);
84 result
= INTERNAL_SYSCALL (readlink
, err
, 3, path
, buf
, len
);
86 if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result
, err
), 0))
88 __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result
, err
), fd
, pathbuf
);
95 libc_hidden_def (readlinkat
)