Allow self-assignment for absolute symbols defined in a linker script

Modifies ld machinery tracking linker script assignments to notice all
assignments, not just those symbols mentioned in DEFINED().

ld/
	PR ld/14962
	* ldlang.h (struct lang_definedness_hash_entry): Add by_object and
	by_script.  Make iteration a single bit field.
	(lang_track_definedness, lang_symbol_definition_iteration): Delete.
	(lang_symbol_defined): Declare.
	* ldlang.c (lang_statement_iteration): Expand comment a little.
	(lang_init <lang_definedness_table>): Make it bigger.
	(lang_track_definedness, lang_symbol_definition): Delete.
	(lang_definedness_newfunc): Update.
	(lang_symbol_defined): New function.
	(lang_update_definedness): Create entries here.  Do track whether
	script definition of symbol is valid, even when also defined in
	an object file.
	* ldexp.c (fold_name <DEFINED>): Update.
	(fold_name <NAME>): Allow self-assignment for absolute symbols
	defined in a linker script.
ld/testsuite/
	* ld-scripts/pr14962-2.d,
	* ld-scripts/pr14962-2.t: New test.
	* ld-scripts/expr.exp: Run it.

8 files changed, 98 insertions, 60 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index a022cba..bc46e5f 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,21 @@
+2014-01-20  Alan Modra  <amodra@gmail.com>
+
+	* ldlang.h (struct lang_definedness_hash_entry): Add by_object and
+	by_script.  Make iteration a single bit field.
+	(lang_track_definedness, lang_symbol_definition_iteration): Delete.
+	(lang_symbol_defined): Declare.
+	* ldlang.c (lang_statement_iteration): Expand comment a little.
+	(lang_init <lang_definedness_table>): Make it bigger.
+	(lang_track_definedness, lang_symbol_definition): Delete.
+	(lang_definedness_newfunc): Update.
+	(lang_symbol_defined): New function.
+	(lang_update_definedness): Create entries here.  Do track whether
+	script definition of symbol is valid, even when also defined in
+	an object file.
+	* ldexp.c (fold_name <DEFINED>): Update.
+	(fold_name <NAME>): Allow self-assignment for absolute symbols
+	defined in a linker script.
+
 2014-01-20  Guy Martin <gmsoft@tuxicoman.be>
 	    Alan Modra  <amodra@gmail.com>
 
diff --git a/ld/ldexp.c b/ld/ldexp.c
index 49e7c65..9a529db 100644
--- a/ld/ldexp.c
+++ b/ld/ldexp.c
@@ -575,13 +575,10 @@ fold_name (etree_type *tree)
       break;
 
     case DEFINED:
-      if (expld.phase == lang_first_phase_enum)
-	lang_track_definedness (tree->name.name);
-      else
+      if (expld.phase != lang_first_phase_enum)
 	{
 	  struct bfd_link_hash_entry *h;
-	  int def_iteration
-	    = lang_symbol_definition_iteration (tree->name.name);
+	  struct lang_definedness_hash_entry *def;
 
 	  h = bfd_wrapped_link_hash_lookup (link_info.output_bfd,
 					    &link_info,
@@ -591,15 +588,33 @@ fold_name (etree_type *tree)
 		      && (h->type == bfd_link_hash_defined
 			  || h->type == bfd_link_hash_defweak
 			  || h->type == bfd_link_hash_common)
-		      && (def_iteration == lang_statement_iteration
-			  || def_iteration == -1));
+		      && ((def = lang_symbol_defined (tree->name.name)) == NULL
+			  || def->by_object
+			  || def->iteration == (lang_statement_iteration & 1)));
 	}
       break;
 
     case NAME:
       if (expld.assign_name != NULL
 	  && strcmp (expld.assign_name, tree->name.name) == 0)
-	expld.assign_name = NULL;
+	{
+	  /* Self-assignment is only allowed for absolute symbols
+	     defined in a linker script.  */
+	  struct bfd_link_hash_entry *h;
+	  struct lang_definedness_hash_entry *def;
+
+	  h = bfd_wrapped_link_hash_lookup (link_info.output_bfd,
+					    &link_info,
+					    tree->name.name,
+					    FALSE, FALSE, TRUE);
+	  if (!(h != NULL
+		&& (h->type == bfd_link_hash_defined
+		    || h->type == bfd_link_hash_defweak)
+		&& h->u.def.section == bfd_abs_section_ptr
+		&& (def = lang_symbol_defined (tree->name.name)) != NULL
+		&& def->iteration == (lang_statement_iteration & 1)))
+	    expld.assign_name = NULL;
+	}
       if (expld.phase == lang_first_phase_enum)
 	;
       else if (tree->name.name[0] == '.' && tree->name.name[1] == 0)
diff --git a/ld/ldlang.c b/ld/ldlang.c
index f6d713c..9e35527 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -107,7 +107,7 @@ struct lang_phdr *lang_phdr_list;
 struct lang_nocrossrefs *nocrossref_list;
 
  /* Functions that traverse the linker script and might evaluate
-    DEFINED() need to increment this.  */
+    DEFINED() need to increment this at the start of the traversal.  */
 int lang_statement_iteration = 0;
 
 etree_type *base; /* Relocation base - or null */
@@ -1221,16 +1221,12 @@ lang_init (void)
 
   abs_output_section->bfd_section = bfd_abs_section_ptr;
 
-  /* The value "3" is ad-hoc, somewhat related to the expected number of
-     DEFINED expressions in a linker script.  For most default linker
-     scripts, there are none.  Why a hash table then?  Well, it's somewhat
-     simpler to re-use working machinery than using a linked list in terms
-     of code-complexity here in ld, besides the initialization which just
-     looks like other code here.  */
+  /* The value "13" is ad-hoc, somewhat related to the expected number of
+     assignments in a linker script.  */
   if (!bfd_hash_table_init_n (&lang_definedness_table,
 			      lang_definedness_newfunc,
 			      sizeof (struct lang_definedness_hash_entry),
-			      3))
+			      13))
     einfo (_("%P%F: can not create hash table: %E\n"));
 }
 
@@ -2054,7 +2050,7 @@ lang_map (void)
       obstack_begin (&map_obstack, 1000);
       bfd_link_hash_traverse (link_info.hash, sort_def_symbol, 0);
     }
-  lang_statement_iteration ++;
+  lang_statement_iteration++;
   print_statements ();
 }
 
@@ -3286,15 +3282,6 @@ open_input_bfds (lang_statement_union_type *s, enum open_bfd_mode mode)
     einfo ("%F");
 }
 
-/* Add a symbol to a hash of symbols used in DEFINED (NAME) expressions.  */
-
-void
-lang_track_definedness (const char *name)
-{
-  if (bfd_hash_lookup (&lang_definedness_table, name, TRUE, FALSE) == NULL)
-    einfo (_("%P%F: bfd_hash_lookup failed creating symbol %s\n"), name);
-}
-
 /* New-function for the definedness hash table.  */
 
 static struct bfd_hash_entry *
@@ -3312,28 +3299,22 @@ lang_definedness_newfunc (struct bfd_hash_entry *entry,
   if (ret == NULL)
     einfo (_("%P%F: bfd_hash_allocate failed creating symbol %s\n"), name);
 
-  ret->iteration = -1;
+  ret->by_object = 0;
+  ret->by_script = 0;
+  ret->iteration = 0;
   return &ret->root;
 }
 
-/* Return the iteration when the definition of NAME was last updated.  A
-   value of -1 means that the symbol is not defined in the linker script
-   or the command line, but may be defined in the linker symbol table.  */
+/* Called during processing of linker script script expressions.
+   For symbols assigned in a linker script, return a struct describing
+   where the symbol is defined relative to the current expression,
+   otherwise return NULL.  */
 
-int
-lang_symbol_definition_iteration (const char *name)
+struct lang_definedness_hash_entry *
+lang_symbol_defined (const char *name)
 {
-  struct lang_definedness_hash_entry *defentry
-    = (struct lang_definedness_hash_entry *)
-    bfd_hash_lookup (&lang_definedness_table, name, FALSE, FALSE);
-
-  /* We've already created this one on the presence of DEFINED in the
-     script, so it can't be NULL unless something is borked elsewhere in
-     the code.  */
-  if (defentry == NULL)
-    FAIL ();
-
-  return defentry->iteration;
+  return ((struct lang_definedness_hash_entry *)
+	  bfd_hash_lookup (&lang_definedness_table, name, FALSE, FALSE));
 }
 
 /* Update the definedness state of NAME.  */
@@ -3343,25 +3324,20 @@ lang_update_definedness (const char *name, struct bfd_link_hash_entry *h)
 {
   struct lang_definedness_hash_entry *defentry
     = (struct lang_definedness_hash_entry *)
-    bfd_hash_lookup (&lang_definedness_table, name, FALSE, FALSE);
+    bfd_hash_lookup (&lang_definedness_table, name, TRUE, FALSE);
 
-  /* We don't keep track of symbols not tested with DEFINED.  */
   if (defentry == NULL)
-    return;
+    einfo (_("%P%F: bfd_hash_lookup failed creating symbol %s\n"), name);
 
-  /* If the symbol was already defined, and not from an earlier statement
-     iteration, don't update the definedness iteration, because that'd
-     make the symbol seem defined in the linker script at this point, and
-     it wasn't; it was defined in some object.  If we do anyway, DEFINED
-     would start to yield false before this point and the construct "sym =
-     DEFINED (sym) ? sym : X;" would change sym to X despite being defined
-     in an object.  */
-  if (h->type != bfd_link_hash_undefined
+  /* If the symbol was already defined, and not by a script, then it
+     must be defined by an object file.  */
+  if (!defentry->by_script
+      && h->type != bfd_link_hash_undefined
       && h->type != bfd_link_hash_common
-      && h->type != bfd_link_hash_new
-      && defentry->iteration == -1)
-    return;
+      && h->type != bfd_link_hash_new)
+    defentry->by_object = 1;
 
+  defentry->by_script = 1;
   defentry->iteration = lang_statement_iteration;
 }
 
diff --git a/ld/ldlang.h b/ld/ldlang.h
index e91153c..8c815c6 100644
--- a/ld/ldlang.h
+++ b/ld/ldlang.h
@@ -465,7 +465,9 @@ struct unique_sections
 struct lang_definedness_hash_entry
 {
   struct bfd_hash_entry root;
-  int iteration;
+  unsigned int by_object : 1;
+  unsigned int by_script : 1;
+  unsigned int iteration : 1;
 };
 
 /* Used by place_orphan to keep track of orphan sections and statements.  */
@@ -658,8 +660,7 @@ extern void lang_add_unique
   (const char *);
 extern const char *lang_get_output_target
   (void);
-extern void lang_track_definedness (const char *);
-extern int lang_symbol_definition_iteration (const char *);
+extern struct lang_definedness_hash_entry *lang_symbol_defined (const char *);
 extern void lang_update_definedness
   (const char *, struct bfd_link_hash_entry *);
 
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index 8fbd375..4cfe40d 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2014-01-20  Alan Modra  <amodra@gmail.com>
+
+	* ld-scripts/pr14962-2.d,
+	* ld-scripts/pr14962-2.t: New test.
+	* ld-scripts/expr.exp: Run it.
+
 2014-01-15  Alan Modra  <amodra@gmail.com>
 
 	* ld-elf/ehdr_start-shared.d: New.
diff --git a/ld/testsuite/ld-scripts/expr.exp b/ld/testsuite/ld-scripts/expr.exp
index 0f92d97..ee8da7f 100644
--- a/ld/testsuite/ld-scripts/expr.exp
+++ b/ld/testsuite/ld-scripts/expr.exp
@@ -25,3 +25,4 @@ run_dump_test expr2
 run_dump_test sane1
 run_dump_test assign-loc
 run_dump_test pr14962
+run_dump_test pr14962-2
diff --git a/ld/testsuite/ld-scripts/pr14962-2.d b/ld/testsuite/ld-scripts/pr14962-2.d
new file mode 100644
index 0000000..5e71433
--- /dev/null
+++ b/ld/testsuite/ld-scripts/pr14962-2.d
@@ -0,0 +1,10 @@
+#ld: -T pr14962-2.t
+#source: pr14962a.s
+#nm: -n
+#notarget: rx-*-* frv-linux
+
+#...
+0+2000 [AT] _start
+#...
+0+2000 A x
+#pass
diff --git a/ld/testsuite/ld-scripts/pr14962-2.t b/ld/testsuite/ld-scripts/pr14962-2.t
new file mode 100644
index 0000000..f2c603b
--- /dev/null
+++ b/ld/testsuite/ld-scripts/pr14962-2.t
@@ -0,0 +1,11 @@
+TOTO = 4096;
+TOTO += 4096;
+
+SECTIONS
+{
+  .text TOTO :
+  {
+    x = ABSOLUTE(TOTO);
+    *(*.text)
+  }
+}