New option -z,keep-text-section prefix.

This option does not merge certain text sections with prefixes
.text.hot, .text.unlikely, .text.startup and .text.exit.

	* layout.cc (Layout::default_section_order): Check for text section
	prefixes.
	(Layout::text_section_name_mapping): New static member.
	(Layout::text_section_name_mapping_count): New static member.
	(Layout::match_section_name): New static function.
	(Layout::output_section_name): Check for text section prefixes.
	* layout.h (Output_section_order::ORDER_TEXT_HOT): New enum value.
	(Output_section_order::ORDER_TEXT_STARTUP): New enum value.
	(Output_section_order::ORDER_TEXT_EXIT): New enum value.
	(Output_section_order::ORDER_TEXT_UNLIKELY): New enum value.
	(Layout::text_section_name_mapping): New static member.
	(Layout::text_section_name_mapping_count): New static member.
	(Layout::match_section_name): New static function.
	* options.h (keep_text_section_prefix): New -z option.
	* testsuite/Makefile.am (keep_text_section_prefix): New test.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/keep_text_section_prefix.cc: New test source.
	* testsuite/keep_text_section_prefix.sh: New test script.

gold/layout.cc

@@ -1905,6 +1905,19 @@ Layout::default_section_order(Output_section* os, bool is_relro_local)
 	    return ORDER_INIT;
 	  else if (strcmp(os->name(), ".fini") == 0)
 	    return ORDER_FINI;
+	  else if (parameters->options().keep_text_section_prefix())
+	    {
+	      // -z,keep-text-section-prefix introduces additional
+	      // output sections.
+	      if (strcmp(os->name(), ".text.hot") == 0)
+		return ORDER_TEXT_HOT;
+	      else if (strcmp(os->name(), ".text.startup") == 0)
+		return ORDER_TEXT_STARTUP;
+	      else if (strcmp(os->name(), ".text.exit") == 0)
+		return ORDER_TEXT_EXIT;
+	      else if (strcmp(os->name(), ".text.unlikely") == 0)
+		return ORDER_TEXT_UNLIKELY;
+	    }
 	}
       return is_execinstr ? ORDER_TEXT : ORDER_READONLY;
     }
@@ -5134,6 +5147,20 @@ const Layout::Section_name_mapping Layout::section_name_mapping[] =
   MAPPING_INIT(".ARM.exidx", ".ARM.exidx"),
   MAPPING_INIT(".gnu.linkonce.armexidx.", ".ARM.exidx"),
 };
+
+// Mapping for ".text" section prefixes with -z,keep-text-section-prefix.
+const Layout::Section_name_mapping Layout::text_section_name_mapping[] =
+{
+  MAPPING_INIT(".text.hot.", ".text.hot"),
+  MAPPING_INIT_EXACT(".text.hot", ".text.hot"),
+  MAPPING_INIT(".text.unlikely.", ".text.unlikely"),
+  MAPPING_INIT_EXACT(".text.unlikely", ".text.unlikely"),
+  MAPPING_INIT(".text.startup.", ".text.startup"),
+  MAPPING_INIT_EXACT(".text.startup", ".text.startup"),
+  MAPPING_INIT(".text.exit.", ".text.exit"),
+  MAPPING_INIT_EXACT(".text.exit", ".text.exit"),
+  MAPPING_INIT(".text.", ".text"),
+};
 #undef MAPPING_INIT
 #undef MAPPING_INIT_EXACT
 
@@ -5141,6 +5168,39 @@ const int Layout::section_name_mapping_count =
   (sizeof(Layout::section_name_mapping)
    / sizeof(Layout::section_name_mapping[0]));
 
+const int Layout::text_section_name_mapping_count =
+  (sizeof(Layout::text_section_name_mapping)
+   / sizeof(Layout::text_section_name_mapping[0]));
+
+// Find section name NAME in PSNM and return the mapped name if found
+// with the length set in PLEN.
+const char *
+Layout::match_section_name(const Layout::Section_name_mapping* psnm,
+			   const int count,
+			   const char* name, size_t* plen)
+{
+  for (int i = 0; i < count; ++i, ++psnm)
+    {
+      if (psnm->fromlen > 0)
+	{
+	  if (strncmp(name, psnm->from, psnm->fromlen) == 0)
+	    {
+	      *plen = psnm->tolen;
+	      return psnm->to;
+	    }
+	}
+      else
+	{
+	  if (strcmp(name, psnm->from) == 0)
+	    {
+	      *plen = psnm->tolen;
+	      return psnm->to;
+	    }
+	}
+    }
+  return NULL;
+}
+
 // Choose the output section name to use given an input section name.
 // Set *PLEN to the length of the name.  *PLEN is initialized to the
 // length of NAME.
@@ -5184,27 +5244,21 @@ Layout::output_section_name(const Relobj* relobj, const char* name,
   // not found in the table, we simply use it as the output section
   // name.
 
-  const Section_name_mapping* psnm = section_name_mapping;
-  for (int i = 0; i < section_name_mapping_count; ++i, ++psnm)
+  if (parameters->options().keep_text_section_prefix()
+      && is_prefix_of(".text", name))
     {
-      if (psnm->fromlen > 0)
-	{
-	  if (strncmp(name, psnm->from, psnm->fromlen) == 0)
-	    {
-	      *plen = psnm->tolen;
-	      return psnm->to;
-	    }
-	}
-      else
-	{
-	  if (strcmp(name, psnm->from) == 0)
-	    {
-	      *plen = psnm->tolen;
-	      return psnm->to;
-	    }
-	}
+      const char* match = match_section_name(text_section_name_mapping,
+					     text_section_name_mapping_count,
+					     name, plen);
+      if (match != NULL)
+	return match;
     }
 
+  const char* match = match_section_name(section_name_mapping,
+					 section_name_mapping_count, name, plen);
+  if (match != NULL)
+    return match;
+
   // As an additional complication, .ctors sections are output in
   // either .ctors or .init_array sections, and .dtors sections are
   // output in either .dtors or .fini_array sections.