Commit the vtable verification feature. This feature is designed to

detect, at run time, if/when the vtable pointer in a C++ object has
been corrupted, before allowing virtual calls through that pointer. 
If pointer corruption is detected, execution of the program is halted.

libstdc++-v3 ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        * fragment.am: Add XTEMPLATE_FLAGS.
        * configure.ac: Add definitions for --enable-vtable-verify.
        * acinclude.m4:  Add --enable-vtable-verify and
        --disable-vtable-verify; define --enable-vtable-verify; define
        VTV_CXXFLAGS, VTV_PCH_CXXFLAGS and VTV_CXXLINKFLAGS.
        * config/abi/pre/gnu.ver: Export symbols for vtable verification.
        * libsupc++/Makefile.am: Define vtv_sources and add it to
        libsupc___la_SOURCES and libsupc__convenience_la_SOURCES.
        * libsupc++/vtv_stubs.cc: New file.
        * include/Makefile.am: Add VTV_PCH_CXXFLAGS to PCHFLAGS.
        * src/Makefile.am: Add VTV_CXXFLAGS to AM_CXXFLAGS; add
        VTV_CXXLINKFLAGS to CXXLINK.
        * src/c++98/Makefile.am: Comment out XTEMPLATE_FLAGS; add VTV_CXXFLAGS
        to AM_CXXFLAGS; add VTV_CXXXLINKFLAGS to CXXLINK.
        * src/C++11/Makefile.am: Ditto.
        * doc/xml/manual/configure.xml: Add entry for --enable-vtable-verify.
        * scripts/testsuite_flags.in: Add cxxvtvflags to Usage; cause
        cxxvtvflags to use VTV_CXXFLAGS and VTV_CXXLINKFLAGS.
        * testsuite/lib/libstdc++.exp: Add cxxvtvflags; add code to locate
        libvtv if --enable-vtable-verify was used; set cxxvtvflags; add
        cxxvtvflags to cxx_final.
        * testsuite/18_support/bad_exception/23591_thread-1.c: Add
        -fvtable-verify=none to compiler flags.
        * testsuite/17_intro/freestanding.cc: Add -fvtable-verify=none
        to compiler flags.
        * configure: Regenerated.
        * Makefile.in: Regenerated.
        * python/Makefile.in: Regenerated.
        * include/Makefile.in: Regenerated.
        * libsupc++/Makefile.in: Regenerated.
        * config.h.in: Regenerated.
        * po/Makefile.in: Regenerated.
        * src/Makefile.in: Regenerated.
        * src/c++98/Makefile.in: Regenerated.
        * src/c++11/Makefile.in: Regenerated.
        * doc/Makefile.in: Regenerated.
        * testsuite/Makefile.in: Regenerated.

top level ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        * configure.ac: Add target-libvtv to target_libraries; disable libvtv
        on non-linux systems; add target-libvtv to noconfigdirs; add
        libsupc++/.libs to C++ library search paths.
        * configure: Regenerated.
        * Makefile.def: Add libvtv to target_modules; make libvtv depend on
        libstdc++ and libgcc.
        * Makefile.in: Regenerated.

include/ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        * vtv-change-permission.h: New file.

contrib/ChangeLog:
2013-08-06  Caroline Tice4  <cmtice@google.com>

        * gcc_update: Add libvtv files.

libgcc/ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        config.host (extra_parts): Add vtv_start.o, vtv_end.o
        vtv_start_preinit.o and vtv_end_preinit.o.
        configure.ac: Add code to check/set enable_vtable_verify.
        Makefile.in: Add rules to build vtv_*.o, if enable_vtable_verify is
        true.
        vtv_start_preinit.c: New file.
        vtv_end_preinit.c: New file.
        vtv_start.c: New file.
        vtv_end.c: New file.
        configure: Regenerated.

gcc/ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        * gcc.c (VTABLE_VERIFICATION_SPEC): New definition.
        (LINK_COMMAND_SPEC): Add VTABLE_VERIFICATION_SPEC.
        * tree-pass.h: Add pass_vtable_verify.
        * varasm.c (assemble_variable): Add code to properly set the comdat
        section and name for the .vtable_map_vars section.
        (assemble_vtyv_preinit_initializer): New function.
        (default_sectin_type_flags):  Make sure .vtable_map_vars section has
        LINK_ONCE flag.
        * output.h: Add function decl for assemble_vtv_preinit_initializer.
        * vtable-verify.c: New file.
        * vtable-verify.h: New file.
        * flag-types.h (enum vtv_priority): Defintions for flag_vtable_verify
        initialiation levels.
        * timevar.def (TV_VTABLE_VERIFICATION): New definition.
        * passes.def: Insert pass_vtable_verify.
        * aclocal.m4: Reorder includes.
        * doc/invoke.texi: Add documentation for the flags -fvtable-verify=,
	-fvtv-debug and -fvtv-counts.
        * config/gnu-user.h (GNU_USER_TARGET_STARTFILE_SPEC): Add vtv_start*.o,
as appropriate, if -fvtable-verify=... is used.
        (GNU_USER_TARGET_ENDFILE_SPEC): Add vtv_end*.o as appropriate, if
        -fvtable-verify=... is used.
        * Makefile.in (OBJS):  Add vtable-verify.o to list.
        (vtable-verify.o): Add new build rule.
        (GTFILES): Add vtable-verify.c to list.
        * common.opt (fvtable-verify=): New flag.
        (vtv_priority): Values for fvtable-verify= flag.
        (fvtv-counts): New flag.
(fvtv-debug): New flag.
        * tree.h (save_vtable_map_decl): New extern function decl.


gcc/cp/ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        * Make-lang.in (*CXX_AND_OBJCXX_OBJS):  Add vtable-class-hierarchy.o to
        list.
        (vtable-class-hierarchy.o): Add build rule.
        * cp-tree.h (vtv_start_verification_constructor_init_function): New
        extern function decl.
        (vtv_finish_verification_constructor_init_function): New extern
        function decl.
        (build_vtbl_address): New extern function decl.
        (get_mangled_vtable_map_var_name): New extern function decl.
        (vtv_compute_class_hierarchy_transitive_closure): New extern function
        decl.
        (vtv_generate_init_routine): New extern function decl.
        (vtv_save_class_info): New extern function decl.
        (vtv_recover_class_info): New extern function decl.
        (vtv_build_vtable_verify_fndecl): New extern function decl.
        * class.c (finish_struct_1): Add call to vtv_save_class_info if
        flag_vtable_verify is true.
        * config-lang.in: Add vtable-class-hierarchy.c to gtfiles list.
        * vtable-class-hierarchy.c: New file.
        * mangle.c (get_mangled_vtable_map_var_name):  New function.
        * decl2.c (start_objects): Update function comment.
        (cp_write_global_declarations): Call vtv_recover_class_info,
        vtv_compute_class_hierarchy_transitive_closure and
        vtv_build_vtable_verify_fndecl, before calling
        finalize_compilation_unit, and call vtv_generate_init_rount after, IFF
        flag_vtable_verify is true.
        (vtv_start_verification_constructor_init_function): New function.
        (vtv_finish_verification_constructor_init_function): New function.
        * init.c (build_vtbl_address): Remove static qualifier from function.

libvtv/ChangeLog:
2013-08-06  Caroline Tice  <cmtice@google.com>

        Initial check-in of new vtable verification feature.
        * configure.ac : New file.
        * acinclude.m4 : New file.
        * Makefile.am : New file.
        * aclocal.m4 : New file.
        * configure.tgt : New file.
        * configure: New file (generated).
        * Makefile.in: New file (generated).
        * vtv_set.h : New file.
        * vtv_utils.cc : New file.
        * vtv_utils.h : New file.
        * vtv_malloc.cc : New file.
        * vtv_rts.cc : New file.
        * vtv_malloc.h : New file.
        * vtv_rts.h : New file.
        * vtv_fail.cc : New file.
        * vtv_fail.h : New file.
        * vtv_map.h : New file.
        * scripts/run-testsuite.sh : New file.
        * scripts/sum-vtv-counts.c : New file.
        * testsuite/parts-test-main.h : New file.
        * testusite/dataentry.cc : New file.
        * testsuite/temp_deriv.cc : New file.
        * testsuite/register_pair.cc : New file.
        * testsuite/virtual_inheritance.cc : New file.
        * testsuite/field-test.cc : New file.
        * testsuite/nested_vcall_test.cc : New file.
        * testsuite/template-list-iostream.cc : New file.
        * testsuite/register_pair_inserts.cc : New file.
        * testsuite/register_pair_inserts_mt.cc : New file.
        * testsuite/event.list : New file.
        * testsuite/parts-test-extra-parts-views.cc : New file.
        * testsuite/parts-test-extra-parts-views.h : New file.
        * testsuite/environment-fail-32.s : New file.
        * testsuite/parts-test-extra-parts.h : New file.
        * testsuite/temp_deriv2.cc : New file.
        * testsuite/dlopen_mt.cc : New file.
        * testsuite/event.h : New file.
        * testsuite/template-list.cc : New file.
        * testsuite/replace-fail.cc : New file.
        * testsuite/Makefile.am : New file.
        * testsuite/Makefile.in: New file (generated).
        * testsuite/mempool_negative.c : New file.
        * testsuite/parts-test-main.cc : New file.
        * testsuite/event-private.cc : New file.
        * testsuite/thunk.cc : New file.
        * testsuite/event-defintiions.cc : New file.
        * testsuite/event-private.h : New file.
        * testsuite/parts-test.list : New file.
        * testusite/register_pair_mt.cc : New file.
        * testsuite/povray-derived.cc : New file.
        * testsuite/event-main.cc : New file.
        * testsuite/environment.cc : New file.
        * testsuite/template-list2.cc : New file.
        * testsuite/thunk_vtable_map_attack.cc : New file.
        * testsuite/parts-test-extra-parts.cc : New file.
        * testsuite/environment-fail-64.s : New file.
        * testsuite/dlopen.cc : New file.
        * testsuite/so.cc : New file.
        * testsuite/temp_deriv3.cc : New file.
        * testsuite/const_vtable.cc : New file.
        * testsuite/mempool_positive.c : New file.
        * testsuite/dup_name.cc : New file.




git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@201555 138bc75d-0d04-0410-961f-82ee72b054a4

9 files changed, 332 insertions, 1 deletions

diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index ab4d2c1b049..af42e3e4555 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,16 @@
+2013-08-06  Caroline Tice  <cmtice@google.com>
+
+	config.host (extra_parts): Add vtv_start.o, vtv_end.o
+	vtv_start_preinit.o and vtv_end_preinit.o.
+	configure.ac: Add code to check/set enable_vtable_verify.
+	Makefile.in: Add rules to build vtv_*.o, if enable_vtable_verify is
+	true.
+	vtv_start_preinit.c: New file.
+	vtv_end_preinit.c: New file.
+	vtv_start.c: New file.
+	vtv_end.c: New file.
+	configure: Regenerated.
+
 2013-08-01  Maxim Kuvyrkov  <maxim@kugelworks.com>
 
 	* config/aarch64/sfp-machine.h, config/aarch64/sync-cache.c,
diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index 958be5ec86f..63fd626da40 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -39,6 +39,7 @@ enable_shared = @enable_shared@
 double_type_size = @double_type_size@
 long_double_type_size = @long_double_type_size@
 decimal_float = @decimal_float@
+enable_vtable_verify = @enable_vtable_verify@
 enable_decimal_float = @enable_decimal_float@
 fixed_point = @fixed_point@
 
@@ -971,6 +972,22 @@ crtendS$(objext): $(srcdir)/crtstuff.c
 # This is a version of crtbegin for -static links.
 crtbeginT$(objext): $(srcdir)/crtstuff.c
 	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_BEGIN -DCRTSTUFFT_O
+
+ifeq ($(enable_vtable_verify),yes)
+# These are used in vtable verification; see comments in source files for
+# more details.
+vtv_start$(objext): $(srcdir)/vtv_start.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS_S) -c $(srcdir)/vtv_start.c
+
+vtv_end$(objext): $(srcdir)/vtv_end.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS_S) -c $(srcdir)/vtv_end.c
+
+vtv_start_preinit$(objext): $(srcdir)/vtv_start_preinit.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS_S) -c $(srcdir)/vtv_start_preinit.c
+
+vtv_end_preinit$(objext): $(srcdir)/vtv_end_preinit.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS_S) -c $(srcdir)/vtv_end_preinit.c
+endif
 endif
 
 ifeq ($(CUSTOM_CRTIN),)
diff --git a/libgcc/config.host b/libgcc/config.host
index 9c47e1b4233..f75ae9a571c 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -197,7 +197,7 @@ case ${host} in
   ;;
 *-*-linux* | frv-*-*linux* | *-*-kfreebsd*-gnu | *-*-knetbsd*-gnu | *-*-gnu* | *-*-kopensolaris*-gnu)
   tmake_file="$tmake_file t-crtstuff-pic t-libgcc-pic t-eh-dw2-dip t-slibgcc t-slibgcc-gld t-slibgcc-elf-ver t-linux"
-  extra_parts="crtbegin.o crtbeginS.o crtbeginT.o crtend.o crtendS.o"
+  extra_parts="crtbegin.o crtbeginS.o crtbeginT.o crtend.o crtendS.o vtv_start.o vtv_end.o vtv_start_preinit.o vtv_end_preinit.o"
   ;;
 *-*-lynxos*)
   tmake_file="$tmake_file t-lynx $cpu_type/t-crtstuff t-crtstuff-pic t-libgcc-pic"
diff --git a/libgcc/configure b/libgcc/configure
index bb36889ae56..29fa46f597a 100644
--- a/libgcc/configure
+++ b/libgcc/configure
@@ -608,6 +608,7 @@ build_os
 build_vendor
 build_cpu
 build
+enable_vtable_verify
 enable_shared
 libgcc_topdir
 target_alias
@@ -655,6 +656,7 @@ with_target_subdir
 with_cross_host
 with_ld
 enable_shared
+enable_vtable_verify
 enable_version_specific_runtime_libs
 with_slibdir
 enable_maintainer_mode
@@ -1288,6 +1290,7 @@ Optional Features:
   --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
   --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
   --disable-shared        don't provide a shared libgcc
+  --enable-vtable-verify    Enable vtable verification feature
   --enable-version-specific-runtime-libs    Specify that runtime libraries should be installed in a compiler-specific directory
   --enable-maintainer-mode
                           enable make rules and dependencies not useful (and
@@ -2140,6 +2143,19 @@ fi
 
 
 
+# Check whether --enable-vtable-verify was given.
+if test "${enable_vtable_verify+set}" = set; then :
+  enableval=$enable_vtable_verify; case "$enableval" in
+ yes) enable_vtable_verify=yes ;;
+ no)  enable_vtable_verify=no ;;
+ *)   enable_vtable_verify=no;;
+ esac
+else
+  enable_vtable_verify=no
+fi
+
+
+
 # Make sure we can run config.sub.
 $SHELL "$ac_aux_dir/config.sub" sun4 >/dev/null 2>&1 ||
   as_fn_error "cannot run $SHELL $ac_aux_dir/config.sub" "$LINENO" 5
diff --git a/libgcc/configure.ac b/libgcc/configure.ac
index 8b7aba5823b..186cd6e9cd7 100644
--- a/libgcc/configure.ac
+++ b/libgcc/configure.ac
@@ -66,6 +66,16 @@ AC_ARG_ENABLE(shared,
 ], [enable_shared=yes])
 AC_SUBST(enable_shared)
 
+AC_ARG_ENABLE(vtable-verify,
+[  --enable-vtable-verify    Enable vtable verification feature ],
+[case "$enableval" in
+ yes) enable_vtable_verify=yes ;;
+ no)  enable_vtable_verify=no ;;
+ *)   enable_vtable_verify=no;;
+ esac],
+[enable_vtable_verify=no])
+AC_SUBST(enable_vtable_verify)
+
 GCC_PICFLAG
 AC_SUBST(PICFLAG)
 
diff --git a/libgcc/vtv_end.c b/libgcc/vtv_end.c
new file mode 100644
index 00000000000..83fa101c8e3
--- /dev/null
+++ b/libgcc/vtv_end.c
@@ -0,0 +1,66 @@
+/*  Copyright (C) 2012, 2013
+    Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC 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 General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* This file is part of the vtable verification feature (for a
+   detailed description of the feature, see comments in
+   vtable-verify.c).  The vtable verification feature creates
+   certain global symbols that need to be read-write sometimes during
+   program execution, and read-only at others.  It uses 'mprotect' to
+   change the memory protections of the pages on which these variables
+   are stored.  In order to not affect the protections of other
+   program variables, these variables are put into a special named
+   section, ".vtable_map_vars", which is page-aligned at the start,
+   and which is padded with a page-sized amount of zeros at the end.
+   To make this section page aligned, we create a special symbol,
+   "_vtable_map_vars_start" which we make the very first thing that
+   goes into the section.  That is defined in vtv_start.c (which
+   contains nothing else).  vtv_start.c gest compiled into
+   vtv_start.o, and vtv_start.o gets inserted into the link line
+   immediately after crtbegin.o, if the program is compiled with
+   -fvtable.verify.
+
+   In order to pad the ".vtable_map_vars" section with a page-sized
+   amount of zeros at the end, there is a second symbol,
+   _vtable_map_vars_end.  This file defines that symbol (and only this
+   symbol).  This second symbol is a page-sized array of chars,
+   zero-filled, and is the very last thing to go into the section.
+   When the GCC driver inserts vtv_start.o into the link line (just
+   after crtbegin.o) it also inserts vtv_end.o into the link line,
+   just before crtend.o.  This has the desired effect of making our
+   section page-aligned and page-size paded, ensuring that no other
+   program data lands on our pages.  */
+
+
+#include "vtv-change-permission.h"
+
+__attribute__ ((constructor(100))) void
+__VLTprotect (void)
+{
+  __VLTChangePermission (__VLTP_READ_ONLY);
+}
+
+/* Page-sized variable to mark end of .vtable_map_vars section.  */
+char _vtable_map_vars_end[VTV_PAGE_SIZE]
+  __attribute__ ((__visibility__ ("protected"), used,
+		  section(".vtable_map_vars")));
diff --git a/libgcc/vtv_end_preinit.c b/libgcc/vtv_end_preinit.c
new file mode 100644
index 00000000000..53d12b07ea1
--- /dev/null
+++ b/libgcc/vtv_end_preinit.c
@@ -0,0 +1,71 @@
+/*  Copyright (C) 2012, 2013
+    Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC 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 General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* This file is part of the vtable verification feature (for a
+   detailed description of the feature, see comments in
+   vtable-verify.c).  The vtable verification feature creates
+   certain global symbols that need to be read-write sometimes during
+   program execution, and read-only at others.  It uses 'mprotect' to
+   change the memory protections of the pages on which these variables
+   are stored.  In order to not affect the protections of other
+   program variables, these variables are put into a special named
+   section, ".vtable_map_vars", which is page-aligned at the start,
+   and which is padded with a page-sized amount of zeros at the end.
+   To make this section page aligned, we create a special symbol,
+   "_vtable_map_vars_start" which we make the very first thing that
+   goes into the section.  That is defined in vtv_start.c (which
+   contains nothing else).  vtv_start.c gest compiled into
+   vtv_start.o, and vtv_start.o gets inserted into the link line
+   immediately after crtbegin.o, if the program is compiled with
+   -fvtable.verify.
+
+   In order to pad the ".vtable_map_vars" section with a page-sized
+   amount of zeros at the end, there is a second symbol,
+   _vtable_map_vars_end.  This file defines that symbol (and only this
+   symbol).  This second symbol is a page-sized array of chars,
+   zero-filled, and is the very last thing to go into the section.
+   When the GCC driver inserts vtv_start.o into the link line (just
+   after crtbegin.o) it also inserts vtv_end.o into the link line,
+   just before crtend.o.  This has the desired effect of making our
+   section page-aligned and page-size paded, ensuring that no other
+   program data lands on our pages.  */
+
+#include "vtv-change-permission.h"
+
+void
+__VLTProtectPreinit (void)
+{
+  __VLTChangePermission (__VLTP_READ_ONLY);
+}
+
+/* Page-sized variable to mark end of .vtable_map_vars section.  */
+char _vtable_map_vars_end[VTV_PAGE_SIZE]
+  __attribute__ ((__visibility__ ("protected"), used,
+		  section(".vtable_map_vars")));
+
+/* Put the function __VLTProtectPreinit into the .preinit_array
+   section.  */
+
+__attribute__ ((section (".preinit_array")))
+    typeof (__VLTProtectPreinit) *__preinit_end = __VLTProtectPreinit;
diff --git a/libgcc/vtv_start.c b/libgcc/vtv_start.c
new file mode 100644
index 00000000000..3efb63dfbb0
--- /dev/null
+++ b/libgcc/vtv_start.c
@@ -0,0 +1,65 @@
+/*  Copyright (C) 2012, 2013
+    Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC 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 General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* This file is part of the vtable verification feature (for a
+   detailed description of the feature, see comments in
+   vtable-verify.c).  The vtable verification feature creates
+   certain global symbols that need to be read-write sometimes during
+   program execution, and read-only at others.  It uses 'mprotect' to
+   change the memory protections of the pages on which these variables
+   are stored.  In order to not affect the protections of other
+   program variables, these variables are put into a special named
+   section, ".vtable_map_vars", which is page-aligned at the start,
+   and which is padded with a page-sized amount of zeros at the end.
+   To make this section page aligned, we create a special symbol,
+   "_vtable_map_vars_start" which we make the very first thing that
+   goes into the section.  This file defines that symbol (and only
+   that symbol).  GCC compiles this file into vtv_start.o, and
+   inserts vtv_start.o into the link line immediately after
+   crtbegin.o, if the program is compiled with -fvtable.verify.
+
+   In order to pad the ".vtable_map_vars" section with a page-sized
+   amount of zeros at the end, there is a second symbol,
+   _vtable_map_vars_end, which is defined in another file, vtv_end.c.
+   This second symbol is a page-sized array of chars, zero-filled, and
+   is the very last thing to go into the section.  When the GCC driver
+   inserts vtv_start.o into the link line (just after crtbegin.o) it
+   also inserts vtv_end.o into the link line, just before crtend.o.
+   This has the desired effect of making our section page-aligned and
+   page-size paded, ensuring that no other program data lands on our
+   pages.  */
+
+#include "vtv-change-permission.h"
+
+__attribute__ ((constructor(98))) void
+__VLTunprotect (void)
+{
+  __VLTChangePermission (__VLTP_READ_WRITE);
+}
+
+/* Page-aligned symbol to mark beginning of .vtable_map_vars section.  */
+char _vtable_map_vars_start []
+__attribute__ ((__visibility__ ("protected"), used, aligned(VTV_PAGE_SIZE),
+		section(".vtable_map_vars")))
+  = { };
diff --git a/libgcc/vtv_start_preinit.c b/libgcc/vtv_start_preinit.c
new file mode 100644
index 00000000000..512c8581a28
--- /dev/null
+++ b/libgcc/vtv_start_preinit.c
@@ -0,0 +1,73 @@
+/*  Copyright (C) 2012, 2013
+    Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC 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 General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* This file is part of the vtable verification feature (for a
+   detailed description of the feature, see comments in
+   vtable-verify.c).  The vtable verification feature creates
+   certain global symbols that need to be read-write sometimes during
+   program execution, and read-only at others.  It uses 'mprotect' to
+   change the memory protections of the pages on which these variables
+   are stored.  In order to not affect the protections of other
+   program variables, these variables are put into a special named
+   section, ".vtable_map_vars", which is page-aligned at the start,
+   and which is padded with a page-sized amount of zeros at the end.
+   To make this section page aligned, we create a special symbol,
+   "_vtable_map_vars_start" which we make the very first thing that
+   goes into the section.  This file defines that symbol (and only
+   that symbol).  GCC compiles this file into vtv_start.o, and
+   inserts vtv_start.o into the link line immediately after
+   crtbegin.o, if the program is compiled with -fvtable.verify.
+
+   In order to pad the ".vtable_map_vars" section with a page-sized
+   amount of zeros at the end, there is a second symbol,
+   _vtable_map_vars_end, which is defined in another file, vtv_end.c.
+   This second symbol is a page-sized array of chars, zero-filled, and
+   is the very last thing to go into the section.  When the GCC driver
+   inserts vtv_start.o into the link line (just after crtbegin.o) it
+   also inserts vtv_end.o into the link line, just before crtend.o.
+   This has the desired effect of making our section page-aligned and
+   page-size paded, ensuring that no other program data lands on our
+   pages.  */
+
+#include "vtv-change-permission.h"
+
+void
+__VLTUnprotectPreinit (void)
+{
+  __VLTChangePermission (__VLTP_READ_WRITE);
+}
+
+/* Page-aligned symbol to mark beginning of .vtable_map_vars section.  */
+char _vtable_map_vars_start []
+__attribute__ ((__visibility__ ("protected"), used, aligned(VTV_PAGE_SIZE),
+		section(".vtable_map_vars")))
+  = { };
+
+
+/* Put the function __VLTUnprotectPreinit into the .preinit_array
+   section.  */
+
+__attribute__ ((section (".preinit_array")))
+    typeof (__VLTUnprotectPreinit) *__preinit = __VLTUnprotectPreinit;
+