[PATCH][GOLD] Handle -Ttext, -Tdata and -Tbss options in scripts.

[Doug Kwan (關振德)]

Hi,

    This patch adds support of -Ttext, -Tdata and -Tbss options in
scripts.  Basically, it does a dot assignment at the first section of
the appropriate type.

-Doug

2009-10-15  Doug Kwan  <dougkwan@google.com>

        * script-sections.cc (Script_sections::set_section_addresses):
        Handle -Ttext, -Tdata and -Tbbs options.
        (Script_sections::create_segments): If the -Tbss option is used,
        begin a new segment when seeing a new run of BBS sections.
-------------- next part --------------
Index: gold/script-sections.cc
===================================================================
RCS file: /cvs/src/src/gold/script-sections.cc,v
retrieving revision 1.22
diff -u -p -r1.22 script-sections.cc
--- gold/script-sections.cc	9 Oct 2009 23:18:19 -0000	1.22
+++ gold/script-sections.cc	15 Oct 2009 08:46:55 -0000
@@ -2827,10 +2827,69 @@ Script_sections::set_section_addresses(S
   // For a relocatable link, we implicitly set dot to zero.
   uint64_t dot_value = 0;
   uint64_t load_address = 0;
+
+  bool any_T_segment_address_set =  
+    (parameters->options().user_set_Ttext()
+     || parameters->options().user_set_Tdata()
+     || parameters->options().user_set_Tbss());
+  bool first_read_only_section_seen = false;
+  bool first_writable_section_seen = false;
+  bool first_nobits_section_seen = false;
   for (Sections_elements::iterator p = this->sections_elements_->begin();
        p != this->sections_elements_->end();
        ++p)
-    (*p)->set_section_addresses(symtab, layout, &dot_value, &load_address);
+    {
+      Output_section* os = (*p)->get_output_section();
+
+      // Handle -Ttext, -Tdata and -Tbss options.  We do this by looking for
+      // the first section of the appropriate type for each of these segments
+      // and do a dot assignment right before that. 
+      if (any_T_segment_address_set
+	  && os != NULL
+	  && (os->flags() & elfcpp::SHF_ALLOC) != 0)
+	{
+	  uint64_t new_dot_value = dot_value;
+
+	  if (!first_read_only_section_seen
+	      && (os->flags() & elfcpp::SHF_WRITE) == 0)
+	    {
+	      // We assume the segment containing the first read-only
+	      // section to be the text segment.
+	      if (parameters->options().user_set_Ttext())
+		new_dot_value = parameters->options().Ttext();
+	      first_read_only_section_seen = true;
+	    }
+	  else if (!first_writable_section_seen
+	      && (os->flags() & elfcpp::SHF_WRITE) != 0)
+	    {
+	      // We assume the segment containing the first writable
+	      // section to be the data segment.
+	      if (parameters->options().user_set_Tdata())
+		new_dot_value = parameters->options().Tdata();
+	      first_writable_section_seen = true;
+	    }
+	  else if (!first_nobits_section_seen
+	      && os->type() == elfcpp::SHT_NOBITS)
+	    {
+	      // We assume the segment containing the first NOBITS section to
+	      // be the bss segment.
+	      if (parameters->options().user_set_Tbss())
+		new_dot_value = parameters->options().Tbss();
+	      first_nobits_section_seen = true;
+	    }
+
+	  // Update dot and load address if necessary.
+	  if (new_dot_value < dot_value)
+	    gold_error(_("dot may not move backward"));
+	  else if (new_dot_value != dot_value)
+	    {
+	      dot_value = new_dot_value;
+	      load_address = new_dot_value;
+	    }
+	}
+
+      (*p)->set_section_addresses(symtab, layout, &dot_value, &load_address);
+    } 
 
   if (this->phdrs_elements_ != NULL)
     {
@@ -2995,6 +3054,14 @@ Script_sections::create_segments(Layout*
 	  // skipping a page.
 	  need_new_segment = true;
 	}
+      else if (parameters->options().user_set_Tbss()
+	       && !is_bss_section(*plast)
+	       && is_bss_section(*p))
+	{
+	  // If -Tbss is specified, we need to separate the data and BSS
+	  // segments.
+	  need_new_segment = true;
+	}
       else if (is_bss_section(*plast) && !is_bss_section(*p))
 	{
 	  // A non-BSS section can not follow a BSS section in the