Fix internal error in gold when script uses section address in assignment.

When processing assignment expressions in a linker script, gold processes
absolute assignments early, but when one of those assignments involves the
address of a section that has not yet been finalized, we get an internal
error in address. This patch fixes the problem by gracefully returning
from expression evaluation even if the address is not yet valid, and
deferring the assignment in such a case.

gold/
	PR gold/14746
	* expression.cc (Expression::Expression_eval_info): Add
	is_valid_pointer field.
	(Expression::eval_maybe_dot): Add is_valid_pointer parameter.
	Adjust all callers.
	(Addr_expression::value_from_output_section): Check whether address
	is valid.
	* script.cc (Symbol_assignment::set_if_absolute): Defer assignment
	if evaluation failed due to address that is not yet valid.
	* script.h: (Expression::eval_maybe_dot): Add is_valid_pointer
	parameter.

4 files changed, 53 insertions, 14 deletions

diff --git a/gold/ChangeLog b/gold/ChangeLog
index 5190e7e..ebed52b 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,5 +1,19 @@
 2015-08-25  Cary Coutant  <ccoutant@gmail.com>
 
+	PR gold/14746
+	* expression.cc (Expression::Expression_eval_info): Add
+	is_valid_pointer field.
+	(Expression::eval_maybe_dot): Add is_valid_pointer parameter.
+	Adjust all callers.
+	(Addr_expression::value_from_output_section): Check whether address
+	is valid.
+	* script.cc (Symbol_assignment::set_if_absolute): Defer assignment
+	if evaluation failed due to address that is not yet valid.
+	* script.h: (Expression::eval_maybe_dot): Add is_valid_pointer
+	parameter.
+
+2015-08-25  Cary Coutant  <ccoutant@gmail.com>
+
 	PR gold/18866
 	PR gold/18703
 	* symtab.cc (Symbol_table): Reorder conditions to avoid internal error.
diff --git a/gold/expression.cc b/gold/expression.cc
index a64fa42..484a493 100644
--- a/gold/expression.cc
+++ b/gold/expression.cc
@@ -74,6 +74,10 @@ struct Expression::Expression_eval_info
   elfcpp::STV* vis_pointer;
   // Pointer to where the rest of the symbol's st_other field should be stored.
   unsigned char* nonvis_pointer;
+  // Whether the value is valid.  In Symbol_assignment::set_if_absolute, we
+  // may be trying to evaluate the address of a section whose address is not
+  // yet finalized, and we need to fail the evaluation gracefully.
+  bool *is_valid_pointer;
 };
 
 // Evaluate an expression.
@@ -83,7 +87,7 @@ Expression::eval(const Symbol_table* symtab, const Layout* layout,
 		 bool check_assertions)
 {
   return this->eval_maybe_dot(symtab, layout, check_assertions, false, 0,
-			      NULL, NULL, NULL, NULL, NULL, NULL, false);
+			      NULL, NULL, NULL, NULL, NULL, NULL, false, NULL);
 }
 
 // Evaluate an expression which may refer to the dot symbol.
@@ -99,7 +103,7 @@ Expression::eval_with_dot(const Symbol_table* symtab, const Layout* layout,
   return this->eval_maybe_dot(symtab, layout, check_assertions, true,
 			      dot_value, dot_section, result_section_pointer,
 			      result_alignment_pointer, NULL, NULL, NULL,
-			      is_section_dot_assignment);
+			      is_section_dot_assignment, NULL);
 }
 
 // Evaluate an expression which may or may not refer to the dot
@@ -114,7 +118,8 @@ Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
 			   elfcpp::STT* type_pointer,
 			   elfcpp::STV* vis_pointer,
 			   unsigned char* nonvis_pointer,
-			   bool is_section_dot_assignment)
+			   bool is_section_dot_assignment,
+			   bool* is_valid_pointer)
 {
   Expression_eval_info eei;
   eei.symtab = symtab;
@@ -138,8 +143,18 @@ Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
 
   eei.result_alignment_pointer = result_alignment_pointer;
 
+  // Assume the value is valid until we try to evaluate an expression
+  // that can't be evaluated yet.
+  bool is_valid = true;
+  eei.is_valid_pointer = &is_valid;
+
   uint64_t val = this->value(&eei);
 
+  if (is_valid_pointer != NULL)
+    *is_valid_pointer = is_valid;
+  else
+    gold_assert(is_valid);
+
   // If this is an assignment to dot within a section, and the value
   // is absolute, treat it as a section-relative offset.
   if (is_section_dot_assignment && *result_section_pointer == NULL)
@@ -295,7 +310,8 @@ class Unary_expression : public Expression
 				      NULL,
 				      NULL,
 				      NULL,
-				      false);
+				      false,
+				      eei->is_valid_pointer);
   }
 
   void
@@ -378,7 +394,8 @@ class Binary_expression : public Expression
 				       NULL,
 				       NULL,
 				       NULL,
-				       false);
+				       false,
+				       eei->is_valid_pointer);
   }
 
   uint64_t
@@ -396,7 +413,8 @@ class Binary_expression : public Expression
 					NULL,
 					NULL,
 					NULL,
-					false);
+					false,
+					eei->is_valid_pointer);
   }
 
   void
@@ -550,7 +568,8 @@ class Trinary_expression : public Expression
 				       NULL,
 				       NULL,
 				       NULL,
-				       false);
+				       false,
+				       eei->is_valid_pointer);
   }
 
   uint64_t
@@ -568,7 +587,8 @@ class Trinary_expression : public Expression
 				       NULL,
 				       NULL,
 				       NULL,
-				       false);
+				       false,
+				       eei->is_valid_pointer);
   }
 
   uint64_t
@@ -586,7 +606,8 @@ class Trinary_expression : public Expression
 				       NULL,
 				       NULL,
 				       NULL,
-				       false);
+				       false,
+				       eei->is_valid_pointer);
   }
 
   void
@@ -945,7 +966,10 @@ class Addr_expression : public Section_expression
   {
     if (eei->result_section_pointer != NULL)
       *eei->result_section_pointer = os;
-    return os->address();
+    if (os->is_address_valid())
+      return os->address();
+    *eei->is_valid_pointer = false;
+    return 0;
   }
 
   uint64_t
diff --git a/gold/script.cc b/gold/script.cc
index 56f126c..cfa3116 100644
--- a/gold/script.cc
+++ b/gold/script.cc
@@ -987,7 +987,7 @@ Symbol_assignment::sized_finalize(Symbol_table* symtab, const Layout* layout,
 						  is_dot_available,
 						  dot_value, dot_section,
 						  &section, NULL, &type,
-						  &vis, &nonvis, false);
+						  &vis, &nonvis, false, NULL);
   Sized_symbol<size>* ssym = symtab->get_sized_symbol<size>(this->sym_);
   ssym->set_value(final_val);
   ssym->set_type(type);
@@ -1009,11 +1009,12 @@ Symbol_assignment::set_if_absolute(Symbol_table* symtab, const Layout* layout,
     return;
 
   Output_section* val_section;
+  bool is_valid;
   uint64_t val = this->val_->eval_maybe_dot(symtab, layout, false,
 					    is_dot_available, dot_value,
 					    dot_section, &val_section, NULL,
-					    NULL, NULL, NULL, false);
-  if (val_section != NULL && val_section != dot_section)
+					    NULL, NULL, NULL, false, &is_valid);
+  if (!is_valid || (val_section != NULL && val_section != dot_section))
     return;
 
   if (parameters->target().get_size() == 32)
diff --git a/gold/script.h b/gold/script.h
index 1731985..739baf1 100644
--- a/gold/script.h
+++ b/gold/script.h
@@ -113,7 +113,7 @@ class Expression
 		 Output_section* dot_section,
 		 Output_section** result_section, uint64_t* result_alignment,
 		 elfcpp::STT* type, elfcpp::STV* vis, unsigned char* nonvis,
-		 bool is_section_dot_assignment);
+		 bool is_section_dot_assignment, bool* is_valid_pointer);
 
   // Print the expression to the FILE.  This is for debugging.
   virtual void