[PATCH v2] Support ASan ODR indicators at compiler side.

[Maxim Ostapenko <m dot ostapenko at samsung dot com>]

Hi,

this is the second attempt to support ASan odr indicators in GCC. I've 
fixed issues with several flags (e.g.TREE_ADDRESSABLE) and introduced 
new "asan odr indicator" attribute to distinguish indicators from other 
symbols.
Looks better now?

Tested and ASan bootstrapped on x86_64-unknown-linux-gnu.

-Maxim

config/

	* bootstrap-asan.mk: Replace LSAN_OPTIONS=detect_leaks=0 with
	ASAN_OPTIONS=detect_leaks=0:use_odr_indicator=1.

gcc/

	* asan.c (asan_global_struct): Refactor.
	(create_odr_indicator): New function.
	(asan_needs_odr_indicator_p): Likewise.
	(is_odr_indicator): Likewise.
	(asan_add_global): Introduce odr_indicator_ptr. Pass it into global's
	constructor.
	(asan_protect_global): Do not protect odr indicators.

gcc/c-family/

	* c-attribs.c (asan odr indicator): New attribute.
	(handle_asan_odr_indicator_attribute): New function.

gcc/testsuite/

	* c-c++-common/asan/no-redundant-odr-indicators-1.c: New test.

diff --git a/config/ChangeLog b/config/ChangeLog
index 3b0092b..0c75185 100644
--- a/config/ChangeLog
+++ b/config/ChangeLog
@@ -1,3 +1,8 @@
+2016-11-14  Maxim Ostapenko  <m.ostapenko@samsung.com>
+
+	* bootstrap-asan.mk: Replace LSAN_OPTIONS=detect_leaks=0 with
+	ASAN_OPTIONS=detect_leaks=0:use_odr_indicator=1.
+
 2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>
 
 	* elf.m4: Remove interix support.
diff --git a/config/bootstrap-asan.mk b/config/bootstrap-asan.mk
index 70baaf9..e73d4c2 100644
--- a/config/bootstrap-asan.mk
+++ b/config/bootstrap-asan.mk
@@ -1,7 +1,7 @@
 # This option enables -fsanitize=address for stage2 and stage3.
 
 # Suppress LeakSanitizer in bootstrap.
-export LSAN_OPTIONS="detect_leaks=0"
+export ASAN_OPTIONS=detect_leaks=0:use_odr_indicator=1
 
 STAGE2_CFLAGS += -fsanitize=address
 STAGE3_CFLAGS += -fsanitize=address
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a76e3e8..64744b9 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2016-11-14  Maxim Ostapenko  <m.ostapenko@samsung.com>
+
+	* asan.c (asan_global_struct): Refactor.
+	(create_odr_indicator): New function.
+	(asan_needs_odr_indicator_p): Likewise.
+	(is_odr_indicator): Likewise.
+	(asan_add_global): Introduce odr_indicator_ptr. Pass it into global's
+	constructor.
+	(asan_protect_global): Do not protect odr indicators.
+
 2016-11-09  Kugan Vivekanandarajah  <kuganv@linaro.org>
 
 	* ipa-cp.c (ipa_get_jf_pass_through_result): Handle unary expressions.
diff --git a/gcc/asan.c b/gcc/asan.c
index 6e93ea3..1191ebe 100644
--- a/gcc/asan.c
+++ b/gcc/asan.c
@@ -1388,6 +1388,16 @@ asan_needs_local_alias (tree decl)
   return DECL_WEAK (decl) || !targetm.binds_local_p (decl);
 }
 
+/* Return true if DECL, a global var, is an artificial ODR indicator symbol
+   therefore doesn't need protection.  */
+
+static bool
+is_odr_indicator (tree decl)
+{
+  return DECL_ARTIFICIAL (decl)
+	 && lookup_attribute ("asan odr indicator", DECL_ATTRIBUTES (decl));
+}
+
 /* Return true if DECL is a VAR_DECL that should be protected
    by Address Sanitizer, by appending a red zone with protected
    shadow memory after it and aligning it to at least
@@ -1436,7 +1446,8 @@ asan_protect_global (tree decl)
       || ASAN_RED_ZONE_SIZE * BITS_PER_UNIT > MAX_OFILE_ALIGNMENT
       || !valid_constant_size_p (DECL_SIZE_UNIT (decl))
       || DECL_ALIGN_UNIT (decl) > 2 * ASAN_RED_ZONE_SIZE
-      || TREE_TYPE (decl) == ubsan_get_source_location_type ())
+      || TREE_TYPE (decl) == ubsan_get_source_location_type ()
+      || is_odr_indicator (decl))
     return false;
 
   rtl = DECL_RTL (decl);
@@ -2266,14 +2277,15 @@ asan_dynamic_init_call (bool after_p)
 static tree
 asan_global_struct (void)
 {
-  static const char *field_names[8]
+  static const char *field_names[]
     = { "__beg", "__size", "__size_with_redzone",
-	"__name", "__module_name", "__has_dynamic_init", "__location", "__odr_indicator"};
-  tree fields[8], ret;
-  int i;
+	"__name", "__module_name", "__has_dynamic_init", "__location",
+	"__odr_indicator"};
+  tree fields[ARRAY_SIZE (field_names)], ret;
+  unsigned i;
 
   ret = make_node (RECORD_TYPE);
-  for (i = 0; i < 8; i++)
+  for (i = 0; i < ARRAY_SIZE (field_names); i++)
     {
       fields[i]
 	= build_decl (UNKNOWN_LOCATION, FIELD_DECL,
@@ -2295,6 +2307,56 @@ asan_global_struct (void)
   return ret;
 }
 
+/* Create and return odr indicator symbol for DECL.
+   TYPE is __asan_global struct type as returned by asan_global_struct.  */
+
+static tree
+create_odr_indicator (tree decl, tree type)
+{
+  char sym_name[100], tmp_name[100];
+  static int lasan_odr_ind_cnt = 0;
+  tree uptr = TREE_TYPE (DECL_CHAIN (TYPE_FIELDS (type)));
+
+  snprintf (tmp_name, sizeof (tmp_name), "__odr_asan_%s_",
+	    IDENTIFIER_POINTER (DECL_NAME (decl)));
+  ASM_GENERATE_INTERNAL_LABEL (sym_name, tmp_name, ++lasan_odr_ind_cnt);
+  char *asterisk = sym_name;
+  while ((asterisk = strchr (asterisk, '*')))
+    *asterisk = '_';
+  tree var = build_decl (UNKNOWN_LOCATION, VAR_DECL, get_identifier (sym_name),
+			 char_type_node);
+  TREE_ADDRESSABLE (var) = 1;
+  TREE_READONLY (var) = 0;
+  TREE_THIS_VOLATILE (var) = 1;
+  DECL_GIMPLE_REG_P (var) = 0;
+  DECL_ARTIFICIAL (var) = 1;
+  DECL_IGNORED_P (var) = 1;
+  TREE_STATIC (var) = 1;
+  TREE_PUBLIC (var) = 1;
+  DECL_VISIBILITY (var) = VISIBILITY_DEFAULT;
+  DECL_VISIBILITY_SPECIFIED (var) = 1;
+
+  TREE_USED (var) = 1;
+  tree ctor = build_constructor_va (TREE_TYPE (var), 1, NULL_TREE,
+				    build_int_cst (unsigned_type_node, 0));
+  TREE_CONSTANT (ctor) = 1;
+  TREE_STATIC (ctor) = 1;
+  DECL_INITIAL (var) = ctor;
+  DECL_ATTRIBUTES (var) = tree_cons (get_identifier ("asan odr indicator"),
+				     NULL, DECL_ATTRIBUTES (var));
+  varpool_node::finalize_decl (var);
+  return fold_convert (uptr, build_fold_addr_expr (var));
+}
+
+/* Return true if DECL, a global var, might be overridden and needs
+   an additional odr indicator symbol.  */
+
+static bool
+asan_needs_odr_indicator_p (tree decl)
+{
+  return !DECL_ARTIFICIAL (decl) && !DECL_WEAK (decl) && TREE_PUBLIC (decl);
+}
+
 /* Append description of a single global DECL into vector V.
    TYPE is __asan_global struct type as returned by asan_global_struct.  */
 
@@ -2335,6 +2397,9 @@ asan_add_global (tree decl, tree type, vec<constructor_elt, va_gc> *v)
       assemble_alias (refdecl, DECL_ASSEMBLER_NAME (decl));
     }
 
+  tree odr_indicator_ptr = asan_needs_odr_indicator_p (decl)
+			     ? create_odr_indicator (decl, type)
+			     : build_int_cst (uptr, 0);
   CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE,
 			  fold_convert (const_ptr_type_node,
 					build_fold_addr_expr (refdecl)));
@@ -2382,8 +2447,7 @@ asan_add_global (tree decl, tree type, vec<constructor_elt, va_gc> *v)
   else
     locptr = build_int_cst (uptr, 0);
   CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, locptr);
-  /* TODO: support ODR indicators.  */
-  CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, build_int_cst (uptr, 0));
+  CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, odr_indicator_ptr);
   init = build_constructor (type, vinner);
   CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, init);
 }
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 925f1b2..44b1f51 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -57,6 +57,8 @@ static tree handle_no_address_safety_analysis_attribute (tree *, tree, tree,
 							 int, bool *);
 static tree handle_no_sanitize_undefined_attribute (tree *, tree, tree, int,
 						    bool *);
+static tree handle_asan_odr_indicator_attribute (tree *, tree, tree, int,
+						    bool *);
 static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noinline_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noclone_attribute (tree *, tree, tree, int, bool *);
@@ -292,6 +294,9 @@ const struct attribute_spec c_common_attribute_table[] =
   { "no_sanitize_undefined",  0, 0, true, false, false,
 			      handle_no_sanitize_undefined_attribute,
 			      false },
+  { "asan odr indicator",     0, 0, true, false, false,
+			      handle_asan_odr_indicator_attribute,
+			      false },
   { "warning",		      1, 1, true,  false, false,
 			      handle_error_attribute, false },
   { "error",		      1, 1, true,  false, false,
@@ -591,6 +596,22 @@ handle_no_sanitize_undefined_attribute (tree *node, tree name, tree, int,
   return NULL_TREE;
 }
 
+/* Handle an "asan odr indicator" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_asan_odr_indicator_attribute (tree *node, tree name, tree, int,
+				     bool *no_add_attrs)
+{
+  if (!VAR_P (*node))
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
 /* Handle a "stack_protect" attribute; arguments as in
    struct attribute_spec.handler.  */
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e822e6f..67361a3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2016-11-14  Maxim Ostapenko  <m.ostapenko@samsung.com>
+
+	* c-c++-common/asan/no-redundant-odr-indicators-1.c: New test.
+
 2016-11-09  Kugan Vivekanandarajah  <kuganv@linaro.org>
 
 	* gcc.dg/ipa/vrp7.c: New test.
diff --git a/gcc/testsuite/c-c++-common/asan/no-redundant-odr-indicators-1.c b/gcc/testsuite/c-c++-common/asan/no-redundant-odr-indicators-1.c
new file mode 100644
index 0000000..ff1f272
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/asan/no-redundant-odr-indicators-1.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-skip-if "" { *-*-* } { "*" } { "-O0" } } */
+
+/* Local variables should not have odr indicators.  */
+static int a = 2;
+/* Thread local variables should not have odr indicators.  */
+__thread int b = 3;
+/* Externally visible  variables should have odr indicators.  */
+int c = 1;
+
+int main () {
+    return 0;
+}
+
+/* { dg-final { scan-assembler-not ".*odr_asan_a.*" } } */
+/* { dg-final { scan-assembler-not ".*odr_asan_b.*" } } */
+/* { dg-final { scan-assembler ".*odr_asan_c.*" } } */