ssp: add Object Size Checking for unistd.h, part 1

The implementation is from NetBSD, with the addition of feature test macros
for readlink.  glibc also wraps the following functions:
confstr, getdomainname, getgroups, gethostname, getlogin_r, getwd, pread,
readlinkat, ttyname_r.

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>

newlib/libc/include/ssp/unistd.h

@@ -0,0 +1,53 @@
+/*	$NetBSD: unistd.h,v 1.7 2015/06/25 18:41:03 joerg Exp $	*/
+
+/*-
+ * Copyright (c) 2006 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Christos Zoulas.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef _SSP_UNISTD_H_
+#define _SSP_UNISTD_H_
+
+#include <ssp/ssp.h>
+
+#if __SSP_FORTIFY_LEVEL > 0
+__BEGIN_DECLS
+
+__ssp_redirect0(_READ_WRITE_RETURN_TYPE, read, \
+    (int __fd, void *__buf, size_t __len), (__fd, __buf, __len));
+
+#if __BSD_VISIBLE || __POSIX_VISIBLE >= 200112 || __XSI_VISIBLE >= 4
+__ssp_redirect(ssize_t, readlink, (const char *__restrict __path, \
+    char *__restrict __buf, size_t __len), (__path, __buf, __len));
+#endif
+
+__ssp_redirect_raw(char *, getcwd, (char *__buf, size_t __len),
+    (__buf, __len), __buf != 0, __ssp_bos);
+
+__END_DECLS
+
+#endif /* __SSP_FORTIFY_LEVEL > 0 */
+#endif /* _SSP_UNISTD_H_ */

newlib/libc/include/sys/unistd.h

@@ -567,4 +567,9 @@ int	_EXFUN(unlinkat, (int, const char *, int));
 #ifdef __cplusplus
 }
 #endif
+
+#if __SSP_FORTIFY_LEVEL > 0
+#include <ssp/unistd.h>
+#endif
+
 #endif /* _SYS_UNISTD_H */