On Thu, Oct 19, 2023 at 02:24:11PM +0200, Richard Biener wrote:
> On Wed, Oct 11, 2023 at 10:48 PM Marek Polacek <pola...@redhat.com> wrote:
> >
> > On Tue, Sep 19, 2023 at 10:58:19AM -0400, Marek Polacek wrote:
> > > On Mon, Sep 18, 2023 at 08:57:39AM +0200, Richard Biener wrote:
> > > > On Fri, Sep 15, 2023 at 5:09 PM Marek Polacek via Gcc-patches
> > > > <gcc-patches@gcc.gnu.org> wrote:
> > > > >
> > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, 
> > > > > powerpc64le-unknown-linux-gnu,
> > > > > and aarch64-unknown-linux-gnu; ok for trunk?
> > > > >
> > > > > -- >8 --
> > > > > In <https://gcc.gnu.org/pipermail/gcc-patches/2023-August/628748.html>
> > > > > I proposed -fhardened, a new umbrella option that enables a 
> > > > > reasonable set
> > > > > of hardening flags.  The read of the room seems to be that the option
> > > > > would be useful.  So here's a patch implementing that option.
> > > > >
> > > > > Currently, -fhardened enables:
> > > > >
> > > > >   -D_FORTIFY_SOURCE=3 (or =2 for older glibcs)
> > > > >   -D_GLIBCXX_ASSERTIONS
> > > > >   -ftrivial-auto-var-init=pattern
> 
> I think =zero is much better here given the overhead is way
> cheaper and pointers get a more reliable behavior.

Ok, changed now.
 
> > > > >   -fPIE  -pie  -Wl,-z,relro,-z,now
> > > > >   -fstack-protector-strong
> > > > >   -fstack-clash-protection
> > > > >   -fcf-protection=full (x86 GNU/Linux only)
> > > > >
> > > > > -fhardened will not override options that were specified on the 
> > > > > command line
> > > > > (before or after -fhardened).  For example,
> > > > >
> > > > >      -D_FORTIFY_SOURCE=1 -fhardened
> > > > >
> > > > > means that _FORTIFY_SOURCE=1 will be used.  Similarly,
> > > > >
> > > > >       -fhardened -fstack-protector
> > > > >
> > > > > will not enable -fstack-protector-strong.
> > > > >
> > > > > In DW_AT_producer it is reflected only as -fhardened; it doesn't 
> > > > > expand
> > > > > to anything.  I think we need a better way to show what it actually
> > > > > enables.
> > > >
> > > > I do think we need to find a solution here to solve asserting 
> > > > compliance.
> > >
> > > Fair enough.
> > >
> > > > Maybe we can have -Whardened that will diagnose any altering of
> > > > -fhardened by other options on the command-line or by missed target
> > > > implementations?  People might for example use -fstack-protector
> > > > but don't really want to make protection lower than requested with 
> > > > -fhardened.
> > > >
> > > > Any such conflict is much less appearant than when you use the
> > > > flags -fhardened composes.
> > >
> > > How about: --help=hardened says which options -fhardened attempts to
> > > enable, and -Whardened warns when it didn't enable an option?  E.g.,
> > >
> > >   -fstack-protector -fhardened -Whardened
> > >
> > > would say that it didn't enable -fstack-protector-strong because
> > > -fstack-protector was specified on the command line?
> > >
> > > If !HAVE_LD_NOW_SUPPORT, --help=hardened probably doesn't even have to
> > > list -z now, likewise for -z relro.
> > >
> > > Unclear if -Whardened should be enabled by default, but probably yes?
> >
> > Here's v2 which adds -Whardened (enabled by default).
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> I think it's OK but I'd like to see a second ACK here.  

Thanks!

> Can you see how our
> primary and secondary targets (+ host OS) behave here?

That's very reasonable.  I tried to build gcc on Compile Farm 119 (AIX) but
that fails with:

ar  -X64 x ../ppc64/libgcc/libgcc_s.a shr.o
ar: 0707-100 ../ppc64/libgcc/libgcc_s.a does not exist.
make[2]: *** [/home/polacek/gcc/libgcc/config/rs6000/t-slibgcc-aix:98: all] 
Error 1
make[2]: Leaving directory '/home/polacek/x/trunk/powerpc-ibm-aix7.3.1.0/libgcc'

and I tried Darwin (104) and that fails with

*** Configuration aarch64-apple-darwin21.6.0 not supported

Is anyone else able to build gcc on those machines, or test the attached
patch?

> I think the
> documentation should elaborate a bit on expectations for non-Linux/GNU
> targets, specifically I think the default configuration for a target should
> with -fhardened _not_ have any -Whardened diagnostics.  Maybe we can
> have a testcase for this?

Sorry, I'm not sure how to test that.  I suppose if -fhardened enables
something not supported on those systems, and it's something for which
we have a configure test, then we shouldn't warn.  This is already the
case for -pie, -z relro, and -z now.  

Should the docs say something like the following for features without
configure checks?

@option{-fhardened} can, on certain systems, attempt to enable features
not supported on that particular system.  In that case, it's possible to
prevent the warning using the @option{-Wno-hardened} option.

I've added a line saying:

+This option is intended to be used in production builds, not merely
+in debug builds.

-- >8 --
In <https://gcc.gnu.org/pipermail/gcc-patches/2023-August/628748.html>
I proposed -fhardened, a new umbrella option that enables a reasonable set
of hardening flags.  The read of the room seems to be that the option
would be useful.  So here's a patch implementing that option.

Currently, -fhardened enables:

  -D_FORTIFY_SOURCE=3 (or =2 for older glibcs)
  -D_GLIBCXX_ASSERTIONS
  -ftrivial-auto-var-init=zero
  -fPIE  -pie  -Wl,-z,relro,-z,now
  -fstack-protector-strong
  -fstack-clash-protection
  -fcf-protection=full (x86 GNU/Linux only)

-fhardened will not override options that were specified on the command line
(before or after -fhardened).  For example,

     -D_FORTIFY_SOURCE=1 -fhardened

means that _FORTIFY_SOURCE=1 will be used.  Similarly,

      -fhardened -fstack-protector

will not enable -fstack-protector-strong.

In DW_AT_producer it is reflected only as -fhardened; it doesn't expand
to anything.  This patch provides -Whardened, enabled by default, which
warns when -fhardened couldn't enable a particular option.  I think most
often it will say that _FORTIFY_SOURCE wasn't enabled because optimization
were not enabled.

gcc/c-family/ChangeLog:

        * c-opts.cc (c_finish_options): Maybe cpp_define _FORTIFY_SOURCE
        and _GLIBCXX_ASSERTIONS.

gcc/ChangeLog:

        * common.opt (Whardened, fhardened): New options.
        * config.in: Regenerate.
        * config/bpf/bpf.cc: Include "opts.h".
        (bpf_option_override): If flag_stack_protector_set_by_fhardened_p, do
        not inform that -fstack-protector does not work.
        * config/i386/i386-options.cc (ix86_option_override_internal): When
        -fhardened, maybe enable -fcf-protection=full.
        * configure: Regenerate.
        * configure.ac: Check if the linker supports '-z now' and '-z relro'.
        * doc/invoke.texi: Document -fhardened and -Whardened.
        * gcc.cc (driver_handle_option): Remember if any link options or -static
        were specified on the command line.
        (process_command): When -fhardened, maybe enable -pie and
        -Wl,-z,relro,-z,now.
        * opts.cc (flag_stack_protector_set_by_fhardened_p): New global.
        (finish_options): When -fhardened, enable
        -ftrivial-auto-var-init=zero and -fstack-protector-strong.
        (print_help_hardened): New.
        (print_help): Call it.
        * toplev.cc (process_options): When -fhardened, enable
        -fstack-clash-protection.  If flag_stack_protector_set_by_fhardened_p,
        do not warn that -fstack-protector not supported for this target.

gcc/testsuite/ChangeLog:

        * gcc.misc-tests/help.exp: Test -fhardened.
        * c-c++-common/fhardened-1.S: New test.
        * c-c++-common/fhardened-1.c: New test.
        * c-c++-common/fhardened-10.c: New test.
        * c-c++-common/fhardened-11.c: New test.
        * c-c++-common/fhardened-12.c: New test.
        * c-c++-common/fhardened-13.c: New test.
        * c-c++-common/fhardened-14.c: New test.
        * c-c++-common/fhardened-15.c: New test.
        * c-c++-common/fhardened-2.c: New test.
        * c-c++-common/fhardened-3.c: New test.
        * c-c++-common/fhardened-4.c: New test.
        * c-c++-common/fhardened-5.c: New test.
        * c-c++-common/fhardened-6.c: New test.
        * c-c++-common/fhardened-7.c: New test.
        * c-c++-common/fhardened-8.c: New test.
        * c-c++-common/fhardened-9.c: New test.
        * gcc.target/i386/cf_check-6.c: New test.
---
 gcc/c-family/c-opts.cc                     | 42 ++++++++++++++
 gcc/common.opt                             |  8 +++
 gcc/config.in                              | 12 ++++
 gcc/config/bpf/bpf.cc                      |  8 ++-
 gcc/config/i386/i386-options.cc            | 17 +++++-
 gcc/configure                              | 50 +++++++++++++++-
 gcc/configure.ac                           | 42 +++++++++++++-
 gcc/doc/invoke.texi                        | 47 ++++++++++++++-
 gcc/gcc.cc                                 | 48 +++++++++++++++-
 gcc/opts.cc                                | 67 +++++++++++++++++++++-
 gcc/opts.h                                 |  1 +
 gcc/testsuite/c-c++-common/fhardened-1.S   |  6 ++
 gcc/testsuite/c-c++-common/fhardened-1.c   | 14 +++++
 gcc/testsuite/c-c++-common/fhardened-10.c  | 12 ++++
 gcc/testsuite/c-c++-common/fhardened-11.c  | 10 ++++
 gcc/testsuite/c-c++-common/fhardened-12.c  | 11 ++++
 gcc/testsuite/c-c++-common/fhardened-13.c  |  6 ++
 gcc/testsuite/c-c++-common/fhardened-14.c  |  6 ++
 gcc/testsuite/c-c++-common/fhardened-15.c  |  5 ++
 gcc/testsuite/c-c++-common/fhardened-2.c   | 12 ++++
 gcc/testsuite/c-c++-common/fhardened-3.c   | 14 +++++
 gcc/testsuite/c-c++-common/fhardened-4.c   |  4 ++
 gcc/testsuite/c-c++-common/fhardened-5.c   | 11 ++++
 gcc/testsuite/c-c++-common/fhardened-6.c   | 12 ++++
 gcc/testsuite/c-c++-common/fhardened-7.c   |  7 +++
 gcc/testsuite/c-c++-common/fhardened-8.c   |  7 +++
 gcc/testsuite/c-c++-common/fhardened-9.c   |  9 +++
 gcc/testsuite/gcc.misc-tests/help.exp      |  2 +
 gcc/testsuite/gcc.target/i386/cf_check-6.c | 12 ++++
 gcc/toplev.cc                              | 18 +++++-
 30 files changed, 506 insertions(+), 14 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-1.S
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-1.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-10.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-11.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-12.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-13.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-14.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-15.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-2.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-3.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-4.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-5.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-6.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-7.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-8.c
 create mode 100644 gcc/testsuite/c-c++-common/fhardened-9.c
 create mode 100644 gcc/testsuite/gcc.target/i386/cf_check-6.c

diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
index ce2e021e69d..f5f6ba24290 100644
--- a/gcc/c-family/c-opts.cc
+++ b/gcc/c-family/c-opts.cc
@@ -1556,6 +1556,9 @@ c_finish_options (void)
       cb_file_change (parse_in, cmd_map);
       linemap_line_start (line_table, 0, 1);
 
+      bool fortify_seen_p = false;
+      bool cxx_assert_seen_p = false;
+
       /* All command line defines must have the same location.  */
       cpp_force_token_locations (parse_in, line_table->highest_line);
       for (size_t i = 0; i < deferred_count; i++)
@@ -1573,6 +1576,45 @@ c_finish_options (void)
              else
                cpp_assert (parse_in, opt->arg);
            }
+
+         if (UNLIKELY (flag_hardened)
+             && (opt->code == OPT_D || opt->code == OPT_U))
+           {
+             if (!fortify_seen_p)
+               fortify_seen_p
+                 = (!strncmp (opt->arg, "_FORTIFY_SOURCE", 15)
+                    && (opt->arg[15] == '\0' || opt->arg[15] == '='));
+             if (!cxx_assert_seen_p)
+               cxx_assert_seen_p
+                 = (!strncmp (opt->arg, "_GLIBCXX_ASSERTIONS", 19)
+                    && (opt->arg[19] == '\0' || opt->arg[19] == '='));
+           }
+       }
+
+      if (flag_hardened)
+       {
+         if (!fortify_seen_p && optimize > 0)
+           {
+             if (TARGET_GLIBC_MAJOR == 2 && TARGET_GLIBC_MINOR >= 35)
+               cpp_define (parse_in, "_FORTIFY_SOURCE=3");
+             else
+               cpp_define (parse_in, "_FORTIFY_SOURCE=2");
+           }
+         else if (optimize == 0)
+           warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+                       "%<_FORTIFY_SOURCE%> is not enabled by %<-fhardened%> "
+                       "because optimizations are turned off");
+         else
+           warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+                       "%<_FORTIFY_SOURCE%> is not enabled by %<-fhardened%> "
+                       "because it was specified in %<-D%> or %<-U%>");
+         if (!cxx_assert_seen_p)
+           cpp_define (parse_in, "_GLIBCXX_ASSERTIONS");
+         else
+           warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+                       "%<_GLIBCXX_ASSERTIONS%> is not enabled by "
+                       "%<-fhardened%> because it was specified in %<-D%> "
+                       "or %<-U%>");
        }
 
       cpp_stop_forcing_token_locations (parse_in);
diff --git a/gcc/common.opt b/gcc/common.opt
index 1cf3bdd3b51..48a15f077ef 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -634,6 +634,10 @@ Wfree-nonheap-object
 Common Var(warn_free_nonheap_object) Init(1) Warning
 Warn when attempting to free a non-heap object.
 
+Whardened
+Common Var(warn_hardened) Init(1) Warning
+Warn when -fhardened did not enable an option from its set.
+
 Whsa
 Common Ignore Warning
 Does nothing.  Preserved for backward compatibility.
@@ -1823,6 +1827,10 @@ fguess-branch-probability
 Common Var(flag_guess_branch_prob) Optimization
 Enable guessing of branch probabilities.
 
+fhardened
+Common Driver Var(flag_hardened)
+Enable various security-relevant flags.
+
 fharden-compares
 Common Var(flag_harden_compares) Optimization
 Harden conditionals not used in branches, checking reversed conditions.
diff --git a/gcc/config.in b/gcc/config.in
index 03faee1c6ac..327b1e3e2ee 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1695,6 +1695,12 @@
 #endif
 
 
+/* Define 0/1 if your linker supports -z now */
+#ifndef USED_FOR_TARGET
+#undef HAVE_LD_NOW_SUPPORT
+#endif
+
+
 /* Define if your PowerPC64 linker only needs function descriptor syms. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_LD_NO_DOT_SYMS
@@ -1738,6 +1744,12 @@
 #endif
 
 
+/* Define 0/1 if your linker supports -z relro */
+#ifndef USED_FOR_TARGET
+#undef HAVE_LD_RELRO_SUPPORT
+#endif
+
+
 /* Define if your linker links a mix of read-only and read-write sections into
    a read-write section. */
 #ifndef USED_FOR_TARGET
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index 437bd652de3..41dc7fd3dae 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -70,6 +70,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify-me.h"
 
 #include "core-builtins.h"
+#include "opts.h"
 
 /* Per-function machine data.  */
 struct GTY(()) machine_function
@@ -250,9 +251,10 @@ bpf_option_override (void)
   /* Disable -fstack-protector as it is not supported in BPF.  */
   if (flag_stack_protect)
     {
-      inform (input_location,
-              "%<-fstack-protector%> does not work "
-             "on this architecture");
+      if (!flag_stack_protector_set_by_fhardened_p)
+       inform (input_location,
+               "%<-fstack-protector%> does not work "
+               "on this architecture");
       flag_stack_protect = 0;
     }
 
diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc
index 072bbc628e2..8b31ee5b80c 100644
--- a/gcc/config/i386/i386-options.cc
+++ b/gcc/config/i386/i386-options.cc
@@ -3069,10 +3069,25 @@ ix86_option_override_internal (bool main_args_p,
         = build_target_option_node (opts, opts_set);
     }
 
+  const bool cf_okay_p = (TARGET_64BIT || TARGET_CMOV);
+  /* When -fhardened, enable -fcf-protection=full, but only when it's
+     compatible with this target, and when it wasn't already specified
+     on the command line.  */
+  if (opts->x_flag_hardened && cf_okay_p)
+    {
+      if (opts->x_flag_cf_protection == CF_NONE)
+       opts->x_flag_cf_protection = CF_FULL;
+      else if (opts->x_flag_cf_protection != CF_FULL)
+       warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+                   "%<-fcf-protection=full%> is not enabled by "
+                   "%<-fhardened%> because it was specified on the command "
+                   "line");
+    }
+
   if (opts->x_flag_cf_protection != CF_NONE)
     {
       if ((opts->x_flag_cf_protection & CF_BRANCH) == CF_BRANCH
-         && !TARGET_64BIT && !TARGET_CMOV)
+         && !cf_okay_p)
        error ("%<-fcf-protection%> is not compatible with this target");
 
       opts->x_flag_cf_protection
diff --git a/gcc/configure b/gcc/configure
index 77f33ee4df6..00ffc82ced8 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -32883,7 +32883,7 @@ if test x"$ld_is_gold" = xno; then
       ld_bndplt_support=yes
     fi
   elif test x$gcc_cv_ld != x; then
-    # Check if linker supports -a bndplt option
+    # Check if linker supports -z bndplt option
     if $gcc_cv_ld --help 2>&1 | grep -- '-z bndplt' > /dev/null; then
       ld_bndplt_support=yes
     fi
@@ -33012,6 +33012,54 @@ $as_echo "#define ENABLE_S390_EXCESS_FLOAT_PRECISION 
1" >>confdefs.h
   ;;
 esac
 
+# Check if the linker supports '-z now'
+ld_now_support=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking linker -z now option" >&5
+$as_echo_n "checking linker -z now option... " >&6; }
+if test x"$ld_is_gold" = xyes; then
+  ld_now_support=yes
+elif test $in_tree_ld = yes ; then
+  if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 
14 -o "$gcc_cv_gld_major_version" -gt 2; then
+    ld_now_support=yes
+  fi
+elif test x$gcc_cv_ld != x; then
+  # Check if linker supports -z now
+  if $gcc_cv_ld --help 2>&1 | grep -- '-z now' > /dev/null; then
+    ld_now_support=yes
+  fi
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_LD_NOW_SUPPORT `if test x"$ld_now_support" = xyes; then echo 1; 
else echo 0; fi`
+_ACEOF
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ld_now_support" >&5
+$as_echo "$ld_now_support" >&6; }
+
+# Check if the linker supports '-z relro'
+ld_relro_support=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking linker -z relro option" >&5
+$as_echo_n "checking linker -z relro option... " >&6; }
+if test x"$ld_is_gold" = xyes; then
+  ld_relro_support=yes
+elif test $in_tree_ld = yes ; then
+  if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 
15 -o "$gcc_cv_gld_major_version" -gt 2; then
+    ld_relro_support=yes
+  fi
+elif test x$gcc_cv_ld != x; then
+  # Check if linker supports -z relro
+  if $gcc_cv_ld --help 2>&1 | grep -- '-z relro' > /dev/null; then
+    ld_relro_support=yes
+  fi
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_LD_RELRO_SUPPORT `if test x"$ld_relro_support" = xyes; then echo 
1; else echo 0; fi`
+_ACEOF
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ld_relro_support" >&5
+$as_echo "$ld_relro_support" >&6; }
+
 # Configure the subdirectories
 # AC_CONFIG_SUBDIRS($subdirs)
 
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 10982cdfc09..fd845308a24 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -7701,7 +7701,7 @@ if test x"$ld_is_gold" = xno; then
       ld_bndplt_support=yes
     fi
   elif test x$gcc_cv_ld != x; then
-    # Check if linker supports -a bndplt option
+    # Check if linker supports -z bndplt option
     if $gcc_cv_ld --help 2>&1 | grep -- '-z bndplt' > /dev/null; then
       ld_bndplt_support=yes
     fi
@@ -7802,6 +7802,46 @@ standards-compatible mode on s390 targets.])
   ;;
 esac
 
+# Check if the linker supports '-z now'
+ld_now_support=no
+AC_MSG_CHECKING(linker -z now option)
+if test x"$ld_is_gold" = xyes; then
+  ld_now_support=yes
+elif test $in_tree_ld = yes ; then
+  if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 
14 -o "$gcc_cv_gld_major_version" -gt 2; then
+    ld_now_support=yes
+  fi
+elif test x$gcc_cv_ld != x; then
+  # Check if linker supports -z now
+  if $gcc_cv_ld --help 2>&1 | grep -- '-z now' > /dev/null; then
+    ld_now_support=yes
+  fi
+fi
+AC_DEFINE_UNQUOTED(HAVE_LD_NOW_SUPPORT,
+  [`if test x"$ld_now_support" = xyes; then echo 1; else echo 0; fi`],
+  [Define 0/1 if your linker supports -z now])
+AC_MSG_RESULT($ld_now_support)
+
+# Check if the linker supports '-z relro'
+ld_relro_support=no
+AC_MSG_CHECKING(linker -z relro option)
+if test x"$ld_is_gold" = xyes; then
+  ld_relro_support=yes
+elif test $in_tree_ld = yes ; then
+  if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 
15 -o "$gcc_cv_gld_major_version" -gt 2; then
+    ld_relro_support=yes
+  fi
+elif test x$gcc_cv_ld != x; then
+  # Check if linker supports -z relro
+  if $gcc_cv_ld --help 2>&1 | grep -- '-z relro' > /dev/null; then
+    ld_relro_support=yes
+  fi
+fi
+AC_DEFINE_UNQUOTED(HAVE_LD_RELRO_SUPPORT,
+  [`if test x"$ld_relro_support" = xyes; then echo 1; else echo 0; fi`],
+  [Define 0/1 if your linker supports -z relro])
+AC_MSG_RESULT($ld_relro_support)
+
 # Configure the subdirectories
 # AC_CONFIG_SUBDIRS($subdirs)
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5a9284d635c..e4237c28608 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -366,7 +366,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wformat-y2k  -Wframe-address
 -Wframe-larger-than=@var{byte-size}  -Wno-free-nonheap-object
 -Wno-if-not-aligned  -Wno-ignored-attributes
--Wignored-qualifiers  -Wno-incompatible-pointer-types
+-Wignored-qualifiers  -Wno-incompatible-pointer-types  -Whardened
 -Wimplicit  -Wimplicit-fallthrough  -Wimplicit-fallthrough=@var{n}
 -Wno-implicit-function-declaration  -Wno-implicit-int
 -Winfinite-recursion
@@ -641,7 +641,7 @@ Objective-C and Objective-C++ Dialects}.
 -fasan-shadow-offset=@var{number}  -fsanitize-sections=@var{s1},@var{s2},...
 -fsanitize-undefined-trap-on-error  -fbounds-check
 -fcf-protection=@r{[}full@r{|}branch@r{|}return@r{|}none@r{|}check@r{]}
--fharden-compares -fharden-conditional-branches
+-fharden-compares -fharden-conditional-branches  -fhardened
 -fharden-control-flow-redundancy  -fhardcfr-skip-leaf
 -fhardcfr-check-exceptions  -fhardcfr-check-returning-calls
 
-fhardcfr-check-noreturn-calls=@r{[}always@r{|}no-xthrow@r{|}nothrow@r{|}never@r{]}
@@ -6860,6 +6860,18 @@ This warning is upgraded to an error by 
@option{-pedantic-errors}.
 Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}.
 This warning is enabled by @option{-Wall}.
 
+@opindex Whardened
+@opindex Wno-hardened
+@item -Whardened
+Warn when @option{-fhardened} did not enable an option from its set (for
+which see @option{-fhardened}).  For instance, using @option{-fhardened}
+and @option{-fstack-protector} at the same time on the command line causes
+@option{-Whardened} to warn because @option{-fstack-protector-strong} is
+not enabled by @option{-fhardened}.
+
+This warning is enabled by default and has effect only when @option{-fhardened}
+is enabled.
+
 @opindex Wimplicit-fallthrough
 @opindex Wno-implicit-fallthrough
 @item -Wimplicit-fallthrough
@@ -17542,6 +17554,37 @@ made @option{no-xthrow} the default setting for this 
option: it excludes
 from the @code{noreturn} treatment only internal functions used to
 (re)raise exceptions, that are not affected by these optimizations.
 
+@opindex fhardened
+@item -fhardened
+Enable a set of flags for C and C++ that improve the security of the
+generated code without affecting its ABI.  The precise flags enabled
+may change between major releases of GCC, but are currently:
+
+@c Keep this in sync with print_help_hardened!
+@gccoptlist{
+-D_FORTIFY_SOURCE=3
+-D_GLIBCXX_ASSERTIONS
+-ftrivial-auto-var-init=zero
+-fPIE  -pie  -Wl,-z,relro,-z,now
+-fstack-protector-strong
+-fstack-clash-protection
+-fcf-protection=full @r{(x86 GNU/Linux only)}
+}
+
+The list of options enabled by @option{-fhardened} can be generated using
+the @option{--help=hardened} option.
+
+When the system glibc is older than 2.35, @option{-D_FORTIFY_SOURCE=2}
+is used instead.
+
+This option is intended to be used in production builds, not merely
+in debug builds.
+
+@option{-fhardened} only enables a particular option if it wasn't
+already specified anywhere on the command line.  For instance,
+@option{-fhardened} @option{-fstack-protector} will only enable
+@option{-fstack-protector}, but not @option{-fstack-protector-strong}.
+
 @opindex fstack-protector
 @item -fstack-protector
 Emit extra code to check for buffer overflows, such as stack smashing
diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index 884284e66b4..a7e5774dcfa 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -302,6 +302,13 @@ static size_t dumpdir_length = 0;
    driver added to dumpdir after dumpbase or linker output name.  */
 static bool dumpdir_trailing_dash_added = false;
 
+/* True if -r, -shared, -pie, or -no-pie were specified on the command
+   line.  */
+static bool any_link_options_p;
+
+/* True if -static was specified on the command line.  */
+static bool static_p;
+
 /* Basename of dump and aux outputs, computed from dumpbase (given or
    derived from output name), to override input_basename in non-%w %b
    et al.  */
@@ -4606,10 +4613,20 @@ driver_handle_option (struct gcc_options *opts,
       save_switch ("-o", 1, &arg, validated, true);
       return true;
 
-#ifdef ENABLE_DEFAULT_PIE
     case OPT_pie:
+#ifdef ENABLE_DEFAULT_PIE
       /* -pie is turned on by default.  */
+      validated = true;
 #endif
+    case OPT_r:
+    case OPT_shared:
+    case OPT_no_pie:
+      any_link_options_p = true;
+      break;
+
+    case OPT_static:
+      static_p = true;
+      break;
 
     case OPT_static_libgcc:
     case OPT_shared_libgcc:
@@ -4985,6 +5002,35 @@ process_command (unsigned int decoded_options_count,
 #endif
     }
 
+  /* TODO: check if -static -pie works and maybe use it.  */
+  if (flag_hardened)
+    {
+      if (!any_link_options_p && !static_p)
+       {
+#ifdef HAVE_LD_PIE
+         save_switch (LD_PIE_SPEC, 0, NULL, /*validated=*/true, 
/*known=*/false);
+#endif
+         /* These are passed straight down to collect2 so we have to break
+            it up like this.  */
+         if (HAVE_LD_NOW_SUPPORT)
+           {
+             add_infile ("-z", "*");
+             add_infile ("now", "*");
+           }
+         if (HAVE_LD_RELRO_SUPPORT)
+           {
+             add_infile ("-z", "*");
+             add_infile ("relro", "*");
+           }
+       }
+      /* We can't use OPT_Whardened yet.  Sigh.  */
+      else if (warn_hardened)
+       warning_at (UNKNOWN_LOCATION, 0,
+                   "linker hardening options not enabled by %<-fhardened%> "
+                   "because other link options were specified on the command "
+                   "line");
+    }
+
   /* Handle -gtoggle as it would later in toplev.cc:process_options to
      make the debug-level-gt spec function work as expected.  */
   if (flag_gtoggle)
diff --git a/gcc/opts.cc b/gcc/opts.cc
index 573dcf8e497..c5fc065ce68 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -43,6 +43,10 @@ along with GCC; see the file COPYING3.  If not see
 /* Set by -fcanon-prefix-map.  */
 bool flag_canon_prefix_map;
 
+/* Set by finish_options when flag_stack_protector was set only because of
+   -fhardened.  Yuck.  */
+bool flag_stack_protector_set_by_fhardened_p;
+
 static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
 
 /* Names of fundamental debug info formats indexed by enum
@@ -1093,6 +1097,17 @@ finish_options (struct gcc_options *opts, struct 
gcc_options *opts_set,
       opts->x_flag_section_anchors = 0;
     }
 
+  if (opts->x_flag_hardened)
+    {
+      if (!opts_set->x_flag_auto_var_init)
+       opts->x_flag_auto_var_init = AUTO_INIT_ZERO;
+      else if (opts->x_flag_auto_var_init != AUTO_INIT_ZERO)
+       warning_at (loc, OPT_Whardened,
+                   "%<-ftrivial-auto-var-init=zero%> is not enabled by "
+                   "%<-fhardened%> because it was specified on the command "
+                   "line");
+    }
+
   if (!opts->x_flag_opts_finished)
     {
       /* We initialize opts->x_flag_pie to -1 so that targets can set a
@@ -1102,7 +1117,8 @@ finish_options (struct gcc_options *opts, struct 
gcc_options *opts_set,
          /* We initialize opts->x_flag_pic to -1 so that we can tell if
             -fpic, -fPIC, -fno-pic or -fno-PIC is used.  */
          if (opts->x_flag_pic == -1)
-           opts->x_flag_pie = DEFAULT_FLAG_PIE;
+           opts->x_flag_pie = (opts->x_flag_hardened
+                               ? /*-fPIE*/ 2 : DEFAULT_FLAG_PIE);
          else
            opts->x_flag_pie = 0;
        }
@@ -1117,9 +1133,29 @@ finish_options (struct gcc_options *opts, struct 
gcc_options *opts_set,
     }
 
   /* We initialize opts->x_flag_stack_protect to -1 so that targets
-     can set a default value.  */
+     can set a default value.  With --enable-default-ssp or -fhardened
+     the default is -fstack-protector-strong.  */
   if (opts->x_flag_stack_protect == -1)
-    opts->x_flag_stack_protect = DEFAULT_FLAG_SSP;
+    {
+      /* This should check FRAME_GROWS_DOWNWARD, but on some targets it's
+        defined in such a way that it uses flag_stack_protect which can't
+        be used here.  Moreover, some targets like BPF don't support
+        -fstack-protector at all but we don't know that here.  So remember
+        that flag_stack_protect was set at the behest of -fhardened.  */
+      if (opts->x_flag_hardened)
+       {
+         opts->x_flag_stack_protect = SPCT_FLAG_STRONG;
+         flag_stack_protector_set_by_fhardened_p = true;
+       }
+      else
+       opts->x_flag_stack_protect = DEFAULT_FLAG_SSP;
+    }
+  else if (opts->x_flag_hardened
+          && opts->x_flag_stack_protect != SPCT_FLAG_STRONG)
+    warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+               "%<-fstack-protector-strong%> is not enabled by "
+               "%<-fhardened%> because it was specified on the command "
+               "line");
 
   if (opts->x_optimize == 0)
     {
@@ -2461,6 +2497,29 @@ parse_and_check_patch_area (const char *arg, bool 
report_error,
   free (patch_area_arg);
 }
 
+/* Print options enabled by -fhardened.  Keep this in sync with the manual!  */
+
+static void
+print_help_hardened ()
+{
+  printf ("%s\n", "The following options are enabled by -fhardened:");
+  printf ("  %s=%d\n", "-D_FORTIFY_SOURCE",
+         (TARGET_GLIBC_MAJOR == 2 && TARGET_GLIBC_MINOR >= 35) ? 3 : 2);
+  printf ("  %s\n", "-D_GLIBCXX_ASSERTIONS");
+  printf ("  %s\n", "-ftrivial-auto-var-init=zero");
+#ifdef HAVE_LD_PIE
+  printf ("  %s  %s\n", "-fPIE", "-pie");
+#endif
+  if (HAVE_LD_NOW_SUPPORT)
+    printf ("  %s\n", "-Wl,-z,now");
+  if (HAVE_LD_RELRO_SUPPORT)
+    printf ("  %s\n", "-Wl,-z,relro");
+  printf ("  %s\n", "-fstack-protector-strong");
+  printf ("  %s\n", "-fstack-clash-protection");
+  printf ("  %s\n", "-fcf-protection=full");
+  putchar ('\n');
+}
+
 /* Print help when OPT__help_ is set.  */
 
 void
@@ -2576,6 +2635,8 @@ print_help (struct gcc_options *opts, unsigned int 
lang_mask,
        }
       else if (lang_flag != 0)
        *pflags |= lang_flag;
+      else if (strncasecmp (a, "hardened", len) == 0)
+       print_help_hardened ();
       else
        warning (0,
                 "unrecognized argument to %<--help=%> option: %q.*s",
diff --git a/gcc/opts.h b/gcc/opts.h
index 00f377f9ca7..d89c5de8114 100644
--- a/gcc/opts.h
+++ b/gcc/opts.h
@@ -344,6 +344,7 @@ struct cl_option_handlers
 /* Hold command-line options associated with stack limitation.  */
 extern const char *opt_fstack_limit_symbol_arg;
 extern int opt_fstack_limit_register_no;
+extern bool flag_stack_protector_set_by_fhardened_p;
 
 /* Input file names.  */
 
diff --git a/gcc/testsuite/c-c++-common/fhardened-1.S 
b/gcc/testsuite/c-c++-common/fhardened-1.S
new file mode 100644
index 00000000000..4dd22cdfe45
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-1.S
@@ -0,0 +1,6 @@
+/* { dg-do preprocess { target pie } } */
+/* { dg-options "-fhardened -O" } */
+
+#if __PIE__ != 2
+# error "-fPIE not enabled"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-1.c 
b/gcc/testsuite/c-c++-common/fhardened-1.c
new file mode 100644
index 00000000000..dd3cde93805
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O" } */
+
+#ifndef __SSP_STRONG__
+# error "-fstack-protector-strong not enabled"
+#endif
+
+#if _FORTIFY_SOURCE < 2
+# error "_FORTIFY_SOURCE not enabled"
+#endif
+
+#ifndef _GLIBCXX_ASSERTIONS
+# error "_GLIBCXX_ASSERTIONS not enabled"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-10.c 
b/gcc/testsuite/c-c++-common/fhardened-10.c
new file mode 100644
index 00000000000..8242530bc4d
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-10.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -D_FORTIFY_SOURCE=1" } */
+
+#if _FORTIFY_SOURCE != 1
+# error "_FORTIFY_SOURCE != 1"
+#endif
+
+#ifndef _GLIBCXX_ASSERTIONS
+# error "_GLIBCXX_ASSERTIONS disabled when it should not be"
+#endif
+
+/* { dg-warning "._FORTIFY_SOURCE. is not enabled" "" { target *-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-11.c 
b/gcc/testsuite/c-c++-common/fhardened-11.c
new file mode 100644
index 00000000000..b8fd65a960c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-11.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O -D_FORTIFY_SOURCE_ -D_GLIBCXX_ASSERTIONS_" } */
+
+#ifndef _FORTIFY_SOURCE
+# error "_FORTIFY_SOURCE disabled when it should not be"
+#endif
+
+#ifndef _GLIBCXX_ASSERTIONS
+# error "_GLIBCXX_ASSERTIONS disabled when it should not be"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-12.c 
b/gcc/testsuite/c-c++-common/fhardened-12.c
new file mode 100644
index 00000000000..42594e4c0e0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-12.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O -fdump-tree-gimple" } */
+
+int
+foo ()
+{
+  int i;
+  return i;
+}
+
+/* { dg-final { scan-tree-dump ".DEFERRED_INIT" "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-13.c 
b/gcc/testsuite/c-c++-common/fhardened-13.c
new file mode 100644
index 00000000000..6945a6391a9
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-13.c
@@ -0,0 +1,6 @@
+/* { dg-do compile { target pie } } */
+/* { dg-options "-fhardened -O" } */
+
+#if __PIE__ != 2
+# error "-fPIE not enabled"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-14.c 
b/gcc/testsuite/c-c++-common/fhardened-14.c
new file mode 100644
index 00000000000..652ece3d4c4
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-14.c
@@ -0,0 +1,6 @@
+/* { dg-do compile { target pie } } */
+/* { dg-options "-fhardened -O -fno-PIE" } */
+
+#ifdef __PIE__
+# error "PIE enabled when it should not be"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-15.c 
b/gcc/testsuite/c-c++-common/fhardened-15.c
new file mode 100644
index 00000000000..c6202754bf5
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-15.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+/* { dg-require-stack-check "specific" } */
+/* { dg-options "-fhardened -O -fstack-check" } */
+
+/* { dg-warning ".-fstack-clash-protection. is not enabled by .-fhardened. 
because .-fstack-check. was specified" "" { target *-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-2.c 
b/gcc/testsuite/c-c++-common/fhardened-2.c
new file mode 100644
index 00000000000..283867ca806
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -fstack-protector" } */
+
+#ifdef __SSP_STRONG__
+# error "-fstack-protector-strong enabled when it should not be"
+#endif
+#ifndef __SSP__
+# error "-fstack-protector not enabled"
+#endif
+
+/* { dg-warning ".-fstack-protector-strong. is not enabled" "" { target *-*-* 
} 0 } */
+/* { dg-warning "._FORTIFY_SOURCE. is not enabled" "" { target *-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-3.c 
b/gcc/testsuite/c-c++-common/fhardened-3.c
new file mode 100644
index 00000000000..6924ba242f0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-3.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O0" } */
+/* Test that we don't get any diagnostic coming from libc headers.  */
+
+#include <stdio.h>
+
+/* The most useful C program known to man.  */
+
+int
+main ()
+{
+}
+
+/* { dg-warning "._FORTIFY_SOURCE. is not enabled" "" { target *-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-4.c 
b/gcc/testsuite/c-c++-common/fhardened-4.c
new file mode 100644
index 00000000000..7d44d299f19
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-4.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O0 -Wno-hardened" } */
+
+/* { dg-bogus "._FORTIFY_SOURCE. is not enabled" "" { target *-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-5.c 
b/gcc/testsuite/c-c++-common/fhardened-5.c
new file mode 100644
index 00000000000..42594e4c0e0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-5.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O -fdump-tree-gimple" } */
+
+int
+foo ()
+{
+  int i;
+  return i;
+}
+
+/* { dg-final { scan-tree-dump ".DEFERRED_INIT" "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-6.c 
b/gcc/testsuite/c-c++-common/fhardened-6.c
new file mode 100644
index 00000000000..744384f317f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-6.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -O -ftrivial-auto-var-init=uninitialized 
-fdump-tree-gimple" } */
+
+int
+foo ()
+{
+  int i;
+  return i;
+}
+
+/* { dg-final { scan-tree-dump-not ".DEFERRED_INIT" "gimple" } } */
+/* { dg-warning ".-ftrivial-auto-var-init=zero. is not enabled" "" { target 
*-*-* } 0 } */
diff --git a/gcc/testsuite/c-c++-common/fhardened-7.c 
b/gcc/testsuite/c-c++-common/fhardened-7.c
new file mode 100644
index 00000000000..32f35eb2595
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-7.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target pie } } */
+/* { dg-options "-fhardened -O -fpie" } */
+
+/* -fpie takes precedence over -fhardened */
+#if __PIE__ != 1
+# error "__PIE__ != 1"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-8.c 
b/gcc/testsuite/c-c++-common/fhardened-8.c
new file mode 100644
index 00000000000..5b3162b4d1f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-8.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target pie } } */
+/* { dg-options "-fhardened -O -fPIC" } */
+
+/* -fPIC takes precedence over -fhardened */
+#ifdef __PIE__
+# error "PIE enabled when it should not be"
+#endif
diff --git a/gcc/testsuite/c-c++-common/fhardened-9.c 
b/gcc/testsuite/c-c++-common/fhardened-9.c
new file mode 100644
index 00000000000..d3b9e79b9b6
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fhardened-9.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-fhardened -U_FORTIFY_SOURCE -U_GLIBCXX_ASSERTIONS" } */
+
+#if defined(_FORTIFY_SOURCE) || defined(_GLIBCXX_ASSERTIONS)
+# error "hardening enabled when it should not be"
+#endif
+
+/* { dg-warning "._FORTIFY_SOURCE. is not enabled" "" { target *-*-* } 0 } */
+/* { dg-warning "._GLIBCXX_ASSERTIONS. is not enabled" "" { target *-*-* } 0 } 
*/
diff --git a/gcc/testsuite/gcc.misc-tests/help.exp 
b/gcc/testsuite/gcc.misc-tests/help.exp
index 52b9cb0ab90..15d618a2528 100644
--- a/gcc/testsuite/gcc.misc-tests/help.exp
+++ b/gcc/testsuite/gcc.misc-tests/help.exp
@@ -151,6 +151,8 @@ foreach cls { "ada" "c" "c++" "d" "fortran" "go" \
 # Listing only excludes gives empty results.
 check_for_options c "--help=^joined,^separate" "" "" ""
 
+check_for_options c "--help=hardened" "The following options are enabled by 
-fhardened" "" ""
+
 if [ info exists prev_columns ] {
     # Reset the enviroment variable to its oriuginal value.
     set env(COLUMNS) $prev_columns
diff --git a/gcc/testsuite/gcc.target/i386/cf_check-6.c 
b/gcc/testsuite/gcc.target/i386/cf_check-6.c
new file mode 100644
index 00000000000..73b78dce889
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cf_check-6.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fhardened -mno-manual-endbr" } */
+/* { dg-final { scan-assembler-times {\mendbr} 1 } } */
+/* Test that -fhardened enables CET.  */
+
+extern void bar (void) __attribute__((__cf_check__));
+
+void
+foo (void)
+{
+  bar ();
+}
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index 8af9bf5090e..743a3a91684 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -1575,6 +1575,19 @@ process_options (bool no_backend)
                  "where the stack grows from lower to higher addresses");
       flag_stack_clash_protection = 0;
     }
+  else if (flag_hardened)
+    {
+      if (!flag_stack_clash_protection
+          /* Don't enable -fstack-clash-protection when -fstack-check=
+             is used: it would result in confusing errors.  */
+          && flag_stack_check == NO_STACK_CHECK)
+       flag_stack_clash_protection = 1;
+      else if (flag_stack_check != NO_STACK_CHECK)
+       warning_at (UNKNOWN_LOCATION, OPT_Whardened,
+                   "%<-fstack-clash-protection%> is not enabled by "
+                   "%<-fhardened%> because %<-fstack-check%> was "
+                   "specified on the command line");
+    }
 
   /* We cannot support -fstack-check= and -fstack-clash-protection at
      the same time.  */
@@ -1590,8 +1603,9 @@ process_options (bool no_backend)
      target already uses a soft frame pointer, the transition is trivial.  */
   if (!FRAME_GROWS_DOWNWARD && flag_stack_protect)
     {
-      warning_at (UNKNOWN_LOCATION, 0,
-                 "%<-fstack-protector%> not supported for this target");
+      if (!flag_stack_protector_set_by_fhardened_p)
+       warning_at (UNKNOWN_LOCATION, 0,
+                   "%<-fstack-protector%> not supported for this target");
       flag_stack_protect = 0;
     }
   if (!flag_stack_protect)

base-commit: 32b74c9e1d46932a4bbb1f46353bfc43c702c20a
-- 
2.41.0

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