Add -ftrivial-auto-var-init option and uninitialized variable attribute.

Initialize automatic variables with either a pattern or with zeroes to increase
the security and predictability of a program by preventing uninitialized memory
disclosure and use.
GCC still considers an automatic variable that doesn't have an explicit
initializer as uninitialized, -Wuninitialized will still report warning messages
on such automatic variables.
With this option, GCC will also initialize any padding of automatic variables
that have structure or union types to zeroes.
You can control this behavior for a specific variable by using the variable
attribute "uninitialized" to control runtime overhead.

gcc/ChangeLog:

2021-09-09  qing zhao  <qing.zhao@oracle.com>

	* builtins.c (expand_builtin_memset): Make external visible.
	* builtins.h (expand_builtin_memset): Declare extern.
	* common.opt (ftrivial-auto-var-init=): New option.
	* doc/extend.texi: Document the uninitialized attribute.
	* doc/invoke.texi: Document -ftrivial-auto-var-init.
	* flag-types.h (enum auto_init_type): New enumerated type
	auto_init_type.
	* gimple-fold.c (clear_padding_type): Add one new parameter.
	(clear_padding_union): Likewise.
	(clear_padding_emit_loop): Likewise.
	(clear_type_padding_in_mask): Likewise.
	(gimple_fold_builtin_clear_padding): Handle this new parameter.
	* gimplify.c (gimple_add_init_for_auto_var): New function.
	(gimple_add_padding_init_for_auto_var): New function.
	(is_var_need_auto_init): New function.
	(gimplify_decl_expr): Add initialization to automatic variables per
	users' requests.
	(gimplify_call_expr): Add one new parameter for call to
	__builtin_clear_padding.
	(gimplify_init_constructor): Add padding initialization in the end.
	* internal-fn.c (INIT_PATTERN_VALUE): New macro.
	(expand_DEFERRED_INIT): New function.
	* internal-fn.def (DEFERRED_INIT): New internal function.
	* tree-cfg.c (verify_gimple_call): Verify calls to .DEFERRED_INIT.
	* tree-sra.c (generate_subtree_deferred_init): New function.
	(scan_function): Avoid setting cannot_scalarize_away_bitmap for
	calls to .DEFERRED_INIT.
	(sra_modify_deferred_init): New function.
	(sra_modify_function_body): Handle calls to DEFERRED_INIT specially.
	* tree-ssa-structalias.c (find_func_aliases_for_call): Likewise.
	* tree-ssa-uninit.c (warn_uninit): Handle calls to DEFERRED_INIT
	specially.
	(check_defs): Likewise.
	(warn_uninitialized_vars): Likewise.
	* tree-ssa.c (ssa_undefined_value_p): Likewise.
	* tree.c (build_common_builtin_nodes): Build tree node for
	BUILT_IN_CLEAR_PADDING when needed.

gcc/c-family/ChangeLog:

2021-09-09  qing zhao  <qing.zhao@oracle.com>

	* c-attribs.c (handle_uninitialized_attribute): New function.
	(c_common_attribute_table): Add "uninitialized" attribute.

gcc/testsuite/ChangeLog:

2021-09-09  qing zhao  <qing.zhao@oracle.com>

	* c-c++-common/auto-init-1.c: New test.
	* c-c++-common/auto-init-10.c: New test.
	* c-c++-common/auto-init-11.c: New test.
	* c-c++-common/auto-init-12.c: New test.
	* c-c++-common/auto-init-13.c: New test.
	* c-c++-common/auto-init-14.c: New test.
	* c-c++-common/auto-init-15.c: New test.
	* c-c++-common/auto-init-16.c: New test.
	* c-c++-common/auto-init-2.c: New test.
	* c-c++-common/auto-init-3.c: New test.
	* c-c++-common/auto-init-4.c: New test.
	* c-c++-common/auto-init-5.c: New test.
	* c-c++-common/auto-init-6.c: New test.
	* c-c++-common/auto-init-7.c: New test.
	* c-c++-common/auto-init-8.c: New test.
	* c-c++-common/auto-init-9.c: New test.
	* c-c++-common/auto-init-esra.c: New test.
	* c-c++-common/auto-init-padding-1.c: New test.
	* c-c++-common/auto-init-padding-2.c: New test.
	* c-c++-common/auto-init-padding-3.c: New test.
	* g++.dg/auto-init-uninit-pred-1_a.C: New test.
	* g++.dg/auto-init-uninit-pred-2_a.C: New test.
	* g++.dg/auto-init-uninit-pred-3_a.C: New test.
	* g++.dg/auto-init-uninit-pred-4.C: New test.
	* gcc.dg/auto-init-sra-1.c: New test.
	* gcc.dg/auto-init-sra-2.c: New test.
	* gcc.dg/auto-init-uninit-1.c: New test.
	* gcc.dg/auto-init-uninit-12.c: New test.
	* gcc.dg/auto-init-uninit-13.c: New test.
	* gcc.dg/auto-init-uninit-14.c: New test.
	* gcc.dg/auto-init-uninit-15.c: New test.
	* gcc.dg/auto-init-uninit-16.c: New test.
	* gcc.dg/auto-init-uninit-17.c: New test.
	* gcc.dg/auto-init-uninit-18.c: New test.
	* gcc.dg/auto-init-uninit-19.c: New test.
	* gcc.dg/auto-init-uninit-2.c: New test.
	* gcc.dg/auto-init-uninit-20.c: New test.
	* gcc.dg/auto-init-uninit-21.c: New test.
	* gcc.dg/auto-init-uninit-22.c: New test.
	* gcc.dg/auto-init-uninit-23.c: New test.
	* gcc.dg/auto-init-uninit-24.c: New test.
	* gcc.dg/auto-init-uninit-25.c: New test.
	* gcc.dg/auto-init-uninit-26.c: New test.
	* gcc.dg/auto-init-uninit-3.c: New test.
	* gcc.dg/auto-init-uninit-34.c: New test.
	* gcc.dg/auto-init-uninit-36.c: New test.
	* gcc.dg/auto-init-uninit-37.c: New test.
	* gcc.dg/auto-init-uninit-4.c: New test.
	* gcc.dg/auto-init-uninit-5.c: New test.
	* gcc.dg/auto-init-uninit-6.c: New test.
	* gcc.dg/auto-init-uninit-8.c: New test.
	* gcc.dg/auto-init-uninit-9.c: New test.
	* gcc.dg/auto-init-uninit-A.c: New test.
	* gcc.dg/auto-init-uninit-B.c: New test.
	* gcc.dg/auto-init-uninit-C.c: New test.
	* gcc.dg/auto-init-uninit-H.c: New test.
	* gcc.dg/auto-init-uninit-I.c: New test.
	* gcc.target/aarch64/auto-init-1.c: New test.
	* gcc.target/aarch64/auto-init-2.c: New test.
	* gcc.target/aarch64/auto-init-3.c: New test.
	* gcc.target/aarch64/auto-init-4.c: New test.
	* gcc.target/aarch64/auto-init-5.c: New test.
	* gcc.target/aarch64/auto-init-6.c: New test.
	* gcc.target/aarch64/auto-init-7.c: New test.
	* gcc.target/aarch64/auto-init-8.c: New test.
	* gcc.target/aarch64/auto-init-padding-1.c: New test.
	* gcc.target/aarch64/auto-init-padding-10.c: New test.
	* gcc.target/aarch64/auto-init-padding-11.c: New test.
	* gcc.target/aarch64/auto-init-padding-12.c: New test.
	* gcc.target/aarch64/auto-init-padding-2.c: New test.
	* gcc.target/aarch64/auto-init-padding-3.c: New test.
	* gcc.target/aarch64/auto-init-padding-4.c: New test.
	* gcc.target/aarch64/auto-init-padding-5.c: New test.
	* gcc.target/aarch64/auto-init-padding-6.c: New test.
	* gcc.target/aarch64/auto-init-padding-7.c: New test.
	* gcc.target/aarch64/auto-init-padding-8.c: New test.
	* gcc.target/aarch64/auto-init-padding-9.c: New test.
	* gcc.target/i386/auto-init-1.c: New test.
	* gcc.target/i386/auto-init-2.c: New test.
	* gcc.target/i386/auto-init-21.c: New test.
	* gcc.target/i386/auto-init-22.c: New test.
	* gcc.target/i386/auto-init-23.c: New test.
	* gcc.target/i386/auto-init-24.c: New test.
	* gcc.target/i386/auto-init-3.c: New test.
	* gcc.target/i386/auto-init-4.c: New test.
	* gcc.target/i386/auto-init-5.c: New test.
	* gcc.target/i386/auto-init-6.c: New test.
	* gcc.target/i386/auto-init-7.c: New test.
	* gcc.target/i386/auto-init-8.c: New test.
	* gcc.target/i386/auto-init-padding-1.c: New test.
	* gcc.target/i386/auto-init-padding-10.c: New test.
	* gcc.target/i386/auto-init-padding-11.c: New test.
	* gcc.target/i386/auto-init-padding-12.c: New test.
	* gcc.target/i386/auto-init-padding-2.c: New test.
	* gcc.target/i386/auto-init-padding-3.c: New test.
	* gcc.target/i386/auto-init-padding-4.c: New test.
	* gcc.target/i386/auto-init-padding-5.c: New test.
	* gcc.target/i386/auto-init-padding-6.c: New test.
	* gcc.target/i386/auto-init-padding-7.c: New test.
	* gcc.target/i386/auto-init-padding-8.c: New test.
	* gcc.target/i386/auto-init-padding-9.c: New test.

1 files changed, 46 insertions, 1 deletions

diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 61b5391..367dcfa 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -3452,11 +3452,56 @@ verify_gimple_call (gcall *stmt)
 	}
     }
 
+  /* For a call to .DEFERRED_INIT,
+     LHS = DEFERRED_INIT (SIZE of the DECL, INIT_TYPE, IS_VLA)
+     we should guarantee that the 1st and the 3rd arguments are consistent:
+     1st argument: SIZE of the DECL;
+     3rd argument: IS_VLA, 0 NO, 1 YES;
+
+     if IS_VLA is false, the 1st argument should be a constant and the same as
+     the size of the LHS.  */
+  if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT))
+    {
+      tree size_of_arg0 = gimple_call_arg (stmt, 0);
+      tree size_of_lhs = TYPE_SIZE_UNIT (TREE_TYPE (lhs));
+      tree is_vla_node = gimple_call_arg (stmt, 2);
+      bool is_vla = (bool) TREE_INT_CST_LOW (is_vla_node);
+
+      if (TREE_CODE (lhs) == SSA_NAME)
+	lhs = SSA_NAME_VAR (lhs);
+
+      poly_uint64 size_from_arg0, size_from_lhs;
+      bool is_constant_size_arg0 = poly_int_tree_p (size_of_arg0,
+						    &size_from_arg0);
+      bool is_constant_size_lhs = poly_int_tree_p (size_of_lhs,
+						   &size_from_lhs);
+      if (!is_vla)
+	{
+	  if (!is_constant_size_arg0)
+	    {
+	      error ("%<DEFFERED_INIT%> calls for non-VLA should have "
+		     "constant size for the first argument");
+	      return true;
+	    }
+	  else if (!is_constant_size_lhs)
+	    {
+	      error ("%<DEFFERED_INIT%> calls for non-VLA should have "
+		     "constant size for the LHS");
+	      return true;
+	    }
+	  else if (maybe_ne (size_from_arg0, size_from_lhs))
+	    {
+	      error ("%<DEFFERED_INIT%> calls for non-VLA should have same "
+		     "constant size for the first argument and LHS");
+	      return true;
+	    }
+	}
+    }
+
   /* ???  The C frontend passes unpromoted arguments in case it
      didn't see a function declaration before the call.  So for now
      leave the call arguments mostly unverified.  Once we gimplify
      unit-at-a-time we have a chance to fix this.  */
-
   for (i = 0; i < gimple_call_num_args (stmt); ++i)
     {
       tree arg = gimple_call_arg (stmt, i);