Implement no_stack_protector attribute.

gcc/ChangeLog:

2020-05-18  Martin Liska  <mliska@suse.cz>

	PR c/94722
	* cfgexpand.c (stack_protect_decl_phase):
	Guard with lookup_attribute("no_stack_protector") at
	various places.
	(expand_used_vars): Likewise here.
	* doc/extend.texi: Document no_stack_protector attribute.

gcc/ada/ChangeLog:

2020-05-18  Martin Liska  <mliska@suse.cz>

	PR c/94722
	* gcc-interface/utils.c (handle_no_stack_protect_attribute):
	New.
	(handle_stack_protect_attribute): Add error message for a
	no_stack_protector function.

gcc/c-family/ChangeLog:

2020-05-18  Martin Liska  <mliska@suse.cz>

	PR c/94722
	* c-attribs.c (handle_no_stack_protect_function_attribute): New.
	(handle_stack_protect_attribute): Add error message for a
	no_stack_protector function.

gcc/testsuite/ChangeLog:

2020-05-18  Martin Liska  <mliska@suse.cz>

	PR c/94722
	* g++.dg/no-stack-protector-attr-2.C: New test.
	* g++.dg/no-stack-protector-attr-3.C: New test.
	* g++.dg/no-stack-protector-attr.C: New test.

1 files changed, 43 insertions, 39 deletions

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 2ac9aef..f3f17d3 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1831,11 +1831,12 @@ stack_protect_decl_phase (tree decl)
   if (bits & SPCT_HAS_SMALL_CHAR_ARRAY)
     has_short_buffer = true;
 
-  if (flag_stack_protect == SPCT_FLAG_ALL
-      || flag_stack_protect == SPCT_FLAG_STRONG
-      || (flag_stack_protect == SPCT_FLAG_EXPLICIT
-	  && lookup_attribute ("stack_protect",
-			       DECL_ATTRIBUTES (current_function_decl))))
+  tree attribs = DECL_ATTRIBUTES (current_function_decl);
+  if (!lookup_attribute ("no_stack_protector", attribs)
+      && (flag_stack_protect == SPCT_FLAG_ALL
+	  || flag_stack_protect == SPCT_FLAG_STRONG
+	  || (flag_stack_protect == SPCT_FLAG_EXPLICIT
+	      && lookup_attribute ("stack_protect", attribs))))
     {
       if ((bits & (SPCT_HAS_SMALL_CHAR_ARRAY | SPCT_HAS_LARGE_CHAR_ARRAY))
 	  && !(bits & SPCT_HAS_AGGREGATE))
@@ -2136,6 +2137,7 @@ expand_used_vars (void)
      set are actually used by the optimized function.  Lay them out.  */
   expand_used_vars_for_block (outer_block, true);
 
+  tree attribs = DECL_ATTRIBUTES (current_function_decl);
   if (stack_vars_num > 0)
     {
       bool has_addressable_vars = false;
@@ -2145,10 +2147,10 @@ expand_used_vars (void)
       /* If stack protection is enabled, we don't share space between
 	 vulnerable data and non-vulnerable data.  */
       if (flag_stack_protect != 0
+	  && !lookup_attribute ("no_stack_protector", attribs)
 	  && (flag_stack_protect != SPCT_FLAG_EXPLICIT
 	      || (flag_stack_protect == SPCT_FLAG_EXPLICIT
-		  && lookup_attribute ("stack_protect",
-				       DECL_ATTRIBUTES (current_function_decl)))))
+		  && lookup_attribute ("stack_protect", attribs))))
 	has_addressable_vars = add_stack_protection_conflicts ();
 
       if (flag_stack_protect == SPCT_FLAG_STRONG && has_addressable_vars)
@@ -2161,38 +2163,40 @@ expand_used_vars (void)
 	dump_stack_var_partition ();
     }
 
-  switch (flag_stack_protect)
-    {
-    case SPCT_FLAG_ALL:
-      create_stack_guard ();
-      break;
 
-    case SPCT_FLAG_STRONG:
-      if (gen_stack_protect_signal
-	  || cfun->calls_alloca
-	  || has_protected_decls
-	  || lookup_attribute ("stack_protect",
-			       DECL_ATTRIBUTES (current_function_decl)))
+  if (!lookup_attribute ("no_stack_protector", attribs))
+    switch (flag_stack_protect)
+      {
+      case SPCT_FLAG_ALL:
 	create_stack_guard ();
-      break;
+	break;
 
-    case SPCT_FLAG_DEFAULT:
-      if (cfun->calls_alloca
-	  || has_protected_decls
-	  || lookup_attribute ("stack_protect",
-			       DECL_ATTRIBUTES (current_function_decl)))
-	create_stack_guard ();
-      break;
+      case SPCT_FLAG_STRONG:
+	if (gen_stack_protect_signal
+	    || cfun->calls_alloca
+	    || has_protected_decls
+	    || lookup_attribute ("stack_protect",
+				 DECL_ATTRIBUTES (current_function_decl)))
+	  create_stack_guard ();
+	break;
 
-    case SPCT_FLAG_EXPLICIT:
-      if (lookup_attribute ("stack_protect",
-			    DECL_ATTRIBUTES (current_function_decl)))
-	create_stack_guard ();
-      break;
+      case SPCT_FLAG_DEFAULT:
+	if (cfun->calls_alloca
+	    || has_protected_decls
+	    || lookup_attribute ("stack_protect",
+				 DECL_ATTRIBUTES (current_function_decl)))
+	  create_stack_guard ();
+	break;
 
-    default:
-      break;
-    }
+      case SPCT_FLAG_EXPLICIT:
+	if (lookup_attribute ("stack_protect",
+			      DECL_ATTRIBUTES (current_function_decl)))
+	  create_stack_guard ();
+	break;
+
+      default:
+	break;
+      }
 
   /* Assign rtl to each variable based on these partitions.  */
   if (stack_vars_num > 0)
@@ -2213,11 +2217,11 @@ expand_used_vars (void)
 	  expand_stack_vars (stack_protect_decl_phase_1, &data);
 
 	  /* Phase 2 contains other kinds of arrays.  */
-	  if (flag_stack_protect == SPCT_FLAG_ALL
-	      || flag_stack_protect == SPCT_FLAG_STRONG
-	      || (flag_stack_protect == SPCT_FLAG_EXPLICIT
-		  && lookup_attribute ("stack_protect",
-				       DECL_ATTRIBUTES (current_function_decl))))
+	  if (!lookup_attribute ("no_stack_protector", attribs)
+	      && (flag_stack_protect == SPCT_FLAG_ALL
+		  || flag_stack_protect == SPCT_FLAG_STRONG
+		  || (flag_stack_protect == SPCT_FLAG_EXPLICIT
+		      && lookup_attribute ("stack_protect", attribs))))
 	    expand_stack_vars (stack_protect_decl_phase_2, &data);
 	}