From 78e03a33628ee801c93f006fa43ebb8cdb8dd243 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 13 Oct 2017 05:02:19 -0700
Subject: [PATCH] gold: Ignore def/ref from a dynamic object for special
 symbols

Since special symbol must be defined in a regular object, definition
from a dynamic object should be ignored.  If special symbol has the
hidden or internal visibility, reference from a dynamic object should
also be ignored.  Also __start and __stop symbols in a dynamic object
shouldn't be preempted.

	PR gold/22291
	* layout.cc (Layout::define_section_symbols): Use STV_PROTECTED
	for __start and __stop symbols.
	* symtab.cc (Symbol_table::define_special_symbol): Add an
	argument, visibility.  Ignore definition and reference from
	a dynamic object, depending on visibility.
	(Symbol_table::do_define_in_output_data): Pass visibility to
	define_special_symbol.
	(Symbol_table::do_define_in_output_segment): Likewise.
	(Symbol_table::do_define_as_constant): Likewise.
	(Symbol_table::add_undefined_symbol_from_command_line): Pass
	STV_DEFAULT to define_special_symbol.
	* symtab.h (Symbol_table::define_special_symbol): Add an
	argument, visibility.

ixx
---
 gold/layout.cc |  4 ++--
 gold/symtab.cc | 51 +++++++++++++++++++++++++++++++++++++++++----------
 gold/symtab.h  |  3 ++-
 3 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/gold/layout.cc b/gold/layout.cc
index 5f25faea55..c9dd823536 100644
--- a/gold/layout.cc
+++ b/gold/layout.cc
@@ -2228,7 +2228,7 @@ Layout::define_section_symbols(Symbol_table* symtab)
 					0, // symsize
 					elfcpp::STT_NOTYPE,
 					elfcpp::STB_GLOBAL,
-					elfcpp::STV_DEFAULT,
+					elfcpp::STV_PROTECTED,
 					0, // nonvis
 					false, // offset_is_from_end
 					true); // only_if_ref
@@ -2241,7 +2241,7 @@ Layout::define_section_symbols(Symbol_table* symtab)
 					0, // symsize
 					elfcpp::STT_NOTYPE,
 					elfcpp::STB_GLOBAL,
-					elfcpp::STV_DEFAULT,
+					elfcpp::STV_PROTECTED,
 					0, // nonvis
 					true, // offset_is_from_end
 					true); // only_if_ref
diff --git a/gold/symtab.cc b/gold/symtab.cc
index 1555de6e5b..13ec5de277 100644
--- a/gold/symtab.cc
+++ b/gold/symtab.cc
@@ -1759,8 +1759,10 @@ template<int size, bool big_endian>
 Sized_symbol<size>*
 Symbol_table::define_special_symbol(const char** pname, const char** pversion,
 				    bool only_if_ref,
+				    elfcpp::STV visibility,
                                     Sized_symbol<size>** poldsym,
-				    bool* resolve_oldsym, bool is_forced_local)
+				    bool* resolve_oldsym,
+				    bool is_forced_local)
 {
   *resolve_oldsym = false;
   *poldsym = NULL;
@@ -1797,8 +1799,21 @@ Symbol_table::define_special_symbol(const char** pname, const char** pversion,
       oldsym = this->lookup(*pname, *pversion);
       if (oldsym == NULL && is_default_version)
 	oldsym = this->lookup(*pname, NULL);
-      if (oldsym == NULL || !oldsym->is_undefined())
+      if (oldsym == NULL)
 	return NULL;
+      if (!oldsym->is_undefined())
+	{
+	  // Skip if the old definition is from a regular object.
+	  if (!oldsym->is_from_dynobj())
+	    return NULL;
+
+	  // If the symbol has the hidden or internal visibility, ignore
+	  // definition and reference from a dynamic object.
+	  if ((visibility == elfcpp::STV_HIDDEN
+	       || visibility == elfcpp::STV_INTERNAL)
+	      && !oldsym->in_reg())
+	    return NULL;
+	}
 
       *pname = oldsym->name();
       if (is_default_version)
@@ -1973,7 +1988,9 @@ Symbol_table::do_define_in_output_data(
     {
 #if defined(HAVE_TARGET_32_BIG) || defined(HAVE_TARGET_64_BIG)
       sym = this->define_special_symbol<size, true>(&name, &version,
-						    only_if_ref, &oldsym,
+						    only_if_ref,
+						    visibility,
+						    &oldsym,
 						    &resolve_oldsym,
 						    is_forced_local);
 #else
@@ -1984,7 +2001,9 @@ Symbol_table::do_define_in_output_data(
     {
 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_64_LITTLE)
       sym = this->define_special_symbol<size, false>(&name, &version,
-						     only_if_ref, &oldsym,
+						     only_if_ref,
+						     visibility,
+						     &oldsym,
 						     &resolve_oldsym,
 						     is_forced_local);
 #else
@@ -2092,7 +2111,9 @@ Symbol_table::do_define_in_output_segment(
     {
 #if defined(HAVE_TARGET_32_BIG) || defined(HAVE_TARGET_64_BIG)
       sym = this->define_special_symbol<size, true>(&name, &version,
-						    only_if_ref, &oldsym,
+						    only_if_ref,
+						    visibility,
+						    &oldsym,
 						    &resolve_oldsym,
 						    is_forced_local);
 #else
@@ -2103,7 +2124,9 @@ Symbol_table::do_define_in_output_segment(
     {
 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_64_LITTLE)
       sym = this->define_special_symbol<size, false>(&name, &version,
-						     only_if_ref, &oldsym,
+						     only_if_ref,
+						     visibility,
+						     &oldsym,
 						     &resolve_oldsym,
 						     is_forced_local);
 #else
@@ -2209,7 +2232,9 @@ Symbol_table::do_define_as_constant(
     {
 #if defined(HAVE_TARGET_32_BIG) || defined(HAVE_TARGET_64_BIG)
       sym = this->define_special_symbol<size, true>(&name, &version,
-						    only_if_ref, &oldsym,
+						    only_if_ref,
+						    visibility,
+						    &oldsym,
 						    &resolve_oldsym,
 						    is_forced_local);
 #else
@@ -2220,7 +2245,9 @@ Symbol_table::do_define_as_constant(
     {
 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_64_LITTLE)
       sym = this->define_special_symbol<size, false>(&name, &version,
-						     only_if_ref, &oldsym,
+						     only_if_ref,
+						     visibility,
+						     &oldsym,
 						     &resolve_oldsym,
 						     is_forced_local);
 #else
@@ -2447,7 +2474,9 @@ Symbol_table::add_undefined_symbol_from_command_line(const char* name)
     {
 #if defined(HAVE_TARGET_32_BIG) || defined(HAVE_TARGET_64_BIG)
       sym = this->define_special_symbol<size, true>(&name, &version,
-						    false, &oldsym,
+						    false,
+						    elfcpp::STV_DEFAULT,
+						    &oldsym,
 						    &resolve_oldsym,
 						    false);
 #else
@@ -2458,7 +2487,9 @@ Symbol_table::add_undefined_symbol_from_command_line(const char* name)
     {
 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_64_LITTLE)
       sym = this->define_special_symbol<size, false>(&name, &version,
-						     false, &oldsym,
+						     false,
+						     elfcpp::STV_DEFAULT,
+						     &oldsym,
 						     &resolve_oldsym,
 						     false);
 #else
diff --git a/gold/symtab.h b/gold/symtab.h
index a67d5eb90d..edf1c1729c 100644
--- a/gold/symtab.h
+++ b/gold/symtab.h
@@ -1830,7 +1830,8 @@ class Symbol_table
   template<int size, bool big_endian>
   Sized_symbol<size>*
   define_special_symbol(const char** pname, const char** pversion,
-			bool only_if_ref, Sized_symbol<size>** poldsym,
+			bool only_if_ref, elfcpp::STV visibility,
+			Sized_symbol<size>** poldsym,
 			bool* resolve_oldsym, bool is_forced_local);
 
   // Define a symbol in an Output_data, sized version.
-- 
2.13.6