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/* Copyright (C) 2005-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysdep.h>
#include <unistd.h>
#include <kernel-features.h>
/* Read the contents of the symbolic link PATH relative to FD into no
more than LEN bytes of BUF. */
ssize_t
readlinkat (fd, path, buf, len)
int fd;
const char *path;
char *buf;
size_t len;
{
int result;
#ifdef __NR_readlinkat
# ifndef __ASSUME_ATFCTS
if (__have_atfcts >= 0)
# endif
{
result = INLINE_SYSCALL (readlinkat, 4, fd, path, buf, len);
# ifndef __ASSUME_ATFCTS
if (result == -1 && errno == ENOSYS)
__have_atfcts = -1;
else
# endif
return result;
}
#endif
#ifndef __ASSUME_ATFCTS
char *pathbuf = NULL;
if (fd != AT_FDCWD && path[0] != '/')
{
size_t pathlen = strlen (path);
if (__builtin_expect (pathlen == 0, 0))
{
__set_errno (ENOENT);
return -1;
}
static const char procfd[] = "/proc/self/fd/%d/%s";
/* Buffer for the path name we are going to use. It consists of
- the string /proc/self/fd/
- the file descriptor number
- the file name provided.
The final NUL is included in the sizeof. A bit of overhead
due to the format elements compensates for possible negative
numbers. */
size_t buflen = sizeof (procfd) + sizeof (int) * 3 + pathlen;
pathbuf = __alloca (buflen);
__snprintf (pathbuf, buflen, procfd, fd, path);
path = pathbuf;
}
INTERNAL_SYSCALL_DECL (err);
result = INTERNAL_SYSCALL (readlink, err, 3, path, buf, len);
if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
{
__atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, pathbuf);
result = -1;
}
return result;
#endif
}
libc_hidden_def (readlinkat)
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