[PATCH] gcc: Disallow trampolines when -fhardened

[Marek Polacek <polacek@redhat.com>]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
It came up that a good hardening strategy is to disable trampolines
which may require executable stack.  Therefore the following patch
adds -Werror=trampolines to -fhardened.

gcc/ChangeLog:

	* common.opt (Wtrampolines): Enable by -fhardened.
	* doc/invoke.texi: Reflect that -fhardened enables -Werror=trampolines.
	* opts.cc (print_help_hardened): Add -Werror=trampolines.
	* toplev.cc (process_options): Enable -Werror=trampolines for
	-fhardened.

gcc/testsuite/ChangeLog:

	* gcc.dg/fhardened-1.c: New test.
	* gcc.dg/fhardened-2.c: New test.
	* gcc.dg/fhardened-3.c: New test.
	* gcc.dg/fhardened-4.c: New test.
	* gcc.dg/fhardened-5.c: New test.
---
 gcc/common.opt                     |  2 +-
 gcc/doc/invoke.texi                |  1 +
 gcc/opts.cc                        |  1 +
 gcc/testsuite/gcc.dg/fhardened-1.c | 27 +++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/fhardened-2.c | 25 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/fhardened-3.c | 25 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/fhardened-4.c | 25 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/fhardened-5.c | 27 +++++++++++++++++++++++++++
 gcc/toplev.cc                      |  8 +++++++-
 9 files changed, 139 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/fhardened-1.c
 create mode 100644 gcc/testsuite/gcc.dg/fhardened-2.c
 create mode 100644 gcc/testsuite/gcc.dg/fhardened-3.c
 create mode 100644 gcc/testsuite/gcc.dg/fhardened-4.c
 create mode 100644 gcc/testsuite/gcc.dg/fhardened-5.c

diff --git a/gcc/common.opt b/gcc/common.opt
index 161a035d736..9b09c7cb3df 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -807,7 +807,7 @@ Common Var(warn_system_headers) Warning
 Do not suppress warnings from system headers.
 
 Wtrampolines
-Common Var(warn_trampolines) Warning
+Common Var(warn_trampolines) Warning EnabledBy(fhardened)
 Warn whenever a trampoline is generated.
 
 Wtrivial-auto-var-init
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 2fab4c5d71f..c1664a1a0f1 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -17745,6 +17745,7 @@ may change between major releases of GCC, but are currently:
 -fstack-protector-strong
 -fstack-clash-protection
 -fcf-protection=full @r{(x86 GNU/Linux only)}
+-Werror=trampolines
 }
 
 The list of options enabled by @option{-fhardened} can be generated using
diff --git a/gcc/opts.cc b/gcc/opts.cc
index 5d5efaf1b9e..aa062b87cef 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -2517,6 +2517,7 @@ print_help_hardened ()
   printf ("  %s\n", "-fstack-protector-strong");
   printf ("  %s\n", "-fstack-clash-protection");
   printf ("  %s\n", "-fcf-protection=full");
+  printf ("  %s\n", "-Werror=trampolines");
   putchar ('\n');
 }
 
diff --git a/gcc/testsuite/gcc.dg/fhardened-1.c b/gcc/testsuite/gcc.dg/fhardened-1.c
new file mode 100644
index 00000000000..8710959b6f1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fhardened-1.c
@@ -0,0 +1,27 @@
+/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-fhardened -O" } */
+
+static void
+baz (int (*bar) (void))
+{
+  bar ();
+}
+
+int
+main (void)
+{
+  int a = 6;
+
+  int
+  bar (void)	// { dg-error "trampoline" }
+  {
+    return a;
+  }
+
+  baz (bar);
+
+  return 0;
+}
+
+/* { dg-prune-output "some warnings being treated as errors" } */
diff --git a/gcc/testsuite/gcc.dg/fhardened-2.c b/gcc/testsuite/gcc.dg/fhardened-2.c
new file mode 100644
index 00000000000..d47512aa47f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fhardened-2.c
@@ -0,0 +1,25 @@
+/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-fhardened -O -Wno-trampolines" } */
+
+static void
+baz (int (*bar) (void))
+{
+  bar ();
+}
+
+int
+main (void)
+{
+  int a = 6;
+
+  int
+  bar (void)	// { dg-bogus "trampoline" }
+  {
+    return a;
+  }
+
+  baz (bar);
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/fhardened-3.c b/gcc/testsuite/gcc.dg/fhardened-3.c
new file mode 100644
index 00000000000..cebae13d8be
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fhardened-3.c
@@ -0,0 +1,25 @@
+/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-fhardened -O -Wno-error" } */
+
+static void
+baz (int (*bar) (void))
+{
+  bar ();
+}
+
+int
+main (void)
+{
+  int a = 6;
+
+  int
+  bar (void)	// { dg-warning "trampoline" }
+  {
+    return a;
+  }
+
+  baz (bar);
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/fhardened-4.c b/gcc/testsuite/gcc.dg/fhardened-4.c
new file mode 100644
index 00000000000..7e62ed3385d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fhardened-4.c
@@ -0,0 +1,25 @@
+/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-fhardened -O -Wno-error=trampolines" } */
+
+static void
+baz (int (*bar) (void))
+{
+  bar ();
+}
+
+int
+main (void)
+{
+  int a = 6;
+
+  int
+  bar (void)	// { dg-warning "trampoline" }
+  {
+    return a;
+  }
+
+  baz (bar);
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/fhardened-5.c b/gcc/testsuite/gcc.dg/fhardened-5.c
new file mode 100644
index 00000000000..5d3f0dcae8e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fhardened-5.c
@@ -0,0 +1,27 @@
+/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
+/* { dg-require-effective-target trampolines } */
+/* { dg-options "-fhardened -O -Wtrampolines" } */
+
+static void
+baz (int (*bar) (void))
+{
+  bar ();
+}
+
+int
+main (void)
+{
+  int a = 6;
+
+  int
+  bar (void)	// { dg-error "trampoline" }
+  {
+    return a;
+  }
+
+  baz (bar);
+
+  return 0;
+}
+
+/* { dg-prune-output "some warnings being treated as errors" } */
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index 85450d97a1a..2f0ac74dee0 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -1682,7 +1682,7 @@ process_options ()
     flag_ipa_ra = 0;
 
   /* Enable -Werror=coverage-mismatch when -Werror and -Wno-error
-     have not been set.  */
+     have not been set.  Also enable -Werror=trampolines for -fhardened.  */
   if (!OPTION_SET_P (warnings_are_errors))
     {
       if (warn_coverage_mismatch
@@ -1693,6 +1693,12 @@ process_options ()
 	  && option_unspecified_p (OPT_Wcoverage_invalid_line_number))
 	diagnostic_classify_diagnostic (global_dc, OPT_Wcoverage_invalid_line_number,
 					DK_ERROR, UNKNOWN_LOCATION);
+
+      if (flag_hardened
+	  && warn_trampolines
+	  && option_unspecified_p (OPT_Wtrampolines))
+	diagnostic_classify_diagnostic (global_dc, OPT_Wtrampolines,
+					DK_ERROR, UNKNOWN_LOCATION);
     }
 
   /* Save the current optimization options.  */

base-commit: b8edb812ff4934c609fdfafe2e1c7f932bc18305
-- 
2.42.0