Use fortify macros for b{zero,copy} along decl from strings.h

As described in BZ#20558, bzero and bcopy declaration can only benefit
from fortified macros when decl came from string.h and when __USE_MISC
is defined (default behaviour).

This is due no standard includes those functions in string.h, so they
are only declared if __USE_MISC is defined (as pointed out in comment 4).
However fortification should be orthogona to other features test macros,
i.e, any function should be fortified if that function is declared.

To fix this behavior, the patch moved the bzero, bcopy, and
__explicit_bzero_chk to a common header (string/bits/strings_fortified.h)
and explicit fortified inclusion macros similar to string.h is added
on strings.h.  This allows to get fortified declarions by only including
strings.h.

Checked on x86_64-linux-gnu and along on a bootstrap installation to check
if the fortified are correctly triggered with example from bug report.

	[BZ #20558]
	* string/bits/string3.h [__USE_MISC] (bcopy): Move to
	strings_fortified.h.
	[__USE_MISC] (bzero): Likewise.
	[__USE_MISC] (explicit_bzero): Likewise.
	* string/strings.h: Include strings_fortified.h.
	* string/Makefile (headers): Add strings_fortified.h.
	* string/bits/strings_fortified.h: New file.
	* include/bits/strings_fortified.h: Likewise.

4 files changed, 54 insertions, 21 deletions

diff --git a/string/Makefile b/string/Makefile
index aaa371f..04e9da9 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -24,7 +24,8 @@ include ../Makeconfig
 
 headers	:= string.h strings.h memory.h endian.h bits/endian.h \
 	   argz.h envz.h byteswap.h bits/byteswap.h bits/byteswap-16.h \
-	   bits/string.h bits/string2.h bits/string3.h
+	   bits/string.h bits/string2.h bits/string3.h \
+	   bits/strings_fortified.h
 
 routines	:= strcat strchr strcmp strcoll strcpy strcspn		\
 		   strverscmp strdup strndup				\
diff --git a/string/bits/string3.h b/string/bits/string3.h
index fe0c161..0b0a377 100644
--- a/string/bits/string3.h
+++ b/string/bits/string3.h
@@ -91,26 +91,7 @@ __NTH (memset (void *__dest, int __ch, size_t __len))
 }
 
 #ifdef __USE_MISC
-__fortify_function void
-__NTH (bcopy (const void *__src, void *__dest, size_t __len))
-{
-  (void) __builtin___memmove_chk (__dest, __src, __len, __bos0 (__dest));
-}
-
-__fortify_function void
-__NTH (bzero (void *__dest, size_t __len))
-{
-  (void) __builtin___memset_chk (__dest, '\0', __len, __bos0 (__dest));
-}
-
-void __explicit_bzero_chk (void *__dest, size_t __len, size_t __destlen)
-  __THROW __nonnull ((1));
-
-__fortify_function void
-__NTH (explicit_bzero (void *__dest, size_t __len))
-{
-  __explicit_bzero_chk (__dest, __len, __bos0 (__dest));
-}
+# include <bits/strings_fortified.h>
 #endif
 
 __fortify_function char *
diff --git a/string/bits/strings_fortified.h b/string/bits/strings_fortified.h
new file mode 100644
index 0000000..fd396f9
--- /dev/null
+++ b/string/bits/strings_fortified.h
@@ -0,0 +1,43 @@
+/* Fortify macros for strings.h functions.
+   Copyright (C) 2017 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/>.  */
+
+#ifndef __STRINGS_FORTIFIED
+# define __STRINGS_FORTIFIED 1
+
+__fortify_function void
+__NTH (bcopy (const void *__src, void *__dest, size_t __len))
+{
+  (void) __builtin___memmove_chk (__dest, __src, __len, __bos0 (__dest));
+}
+
+__fortify_function void
+__NTH (bzero (void *__dest, size_t __len))
+{
+  (void) __builtin___memset_chk (__dest, '\0', __len, __bos0 (__dest));
+}
+
+void __explicit_bzero_chk (void *__dest, size_t __len, size_t __destlen)
+  __THROW __nonnull ((1));
+
+__fortify_function void
+__NTH (explicit_bzero (void *__dest, size_t __len))
+{
+  __explicit_bzero_chk (__dest, __len, __bos0 (__dest));
+}
+
+#endif
diff --git a/string/strings.h b/string/strings.h
index ece21c8..69b75b1 100644
--- a/string/strings.h
+++ b/string/strings.h
@@ -136,4 +136,12 @@ __END_DECLS
 
 #endif	/* string.h  */
 
+#if __GNUC_PREREQ (3,4) && __USE_FORTIFY_LEVEL > 0 \
+    && defined __fortify_function
+/* Functions with security checks.  */
+# if defined __USE_MISC || !defined __USE_XOPEN2K8
+#  include <bits/strings_fortified.h>
+# endif
+#endif
+
 #endif	/* strings.h  */