Patch adds support to allow plugins to map selected subset of sections to unique

segments.


2012-08-24  Sriraman Tallam  <tmsriram@google.com>

	* gold.cc (queue_middle_tasks): Call layout again when unique
	segments for sections is desired.
	* layout.cc (Layout::Layout): Initialize new members.
	(Layout::get_output_section_flags): New function.
	(Layout::choose_output_section): Call get_output_section_flags.
	(Layout::layout): Make output section for mapping to a unique segment.
	(Layout::insert_section_segment_map): New function.
	(Layout::attach_allocated_section_to_segment): Make unique segment for
	output sections marked so.
	(Layout::segment_precedes): Check for unique segments when sorting.
	* layout.h (Layout::Unique_segment_info): New struct.
	(Layout::Section_segment_map): New typedef.
	(Layout::insert_section_segment_map): New function.
	(Layout::get_output_section_flags): New function.
	(Layout::is_unique_segment_for_sections_specified): New function.
	(Layout::set_unique_segment_for_sections_specified): New function.
	(Layout::unique_segment_for_sections_specified_): New member.
	(Layout::section_segment_map_): New member.
	* object.cc (Sized_relobj_file<size, big_endian>::do_layout):
	Rename is_gc_pass_one to is_pass_one.
	Rename is_gc_pass_two to is_pass_two.
	Rename is_gc_or_icf to is_two_pass.
	Check for which pass based on whether symbols data is present.
	Make it two pass when unique segments for sections is desired.
	* output.cc (Output_section::Output_section): Initialize new
	members.
	* output.h (Output_section::is_unique_segment): New function.
	(Output_section::set_is_unique_segment): New function.
	(Output_section::is_unique_segment_): New member.
	(Output_section::extra_segment_flags): New function.
	(Output_section::set_extra_segment_flags): New function.
	(Output_section::extra_segment_flags_): New member.
	(Output_section::segment_alignment): New function.
	(Output_section::set_segment_alignment): New function.
	(Output_section::segment_alignment_): New member.
	(Output_segment::Output_segment): Initialize is_unique_segment_.
	(Output_segment::is_unique_segment): New function.
	(Output_segment::set_is_unique_segment): New function.
	(Output_segment::is_unique_segment_): New member.
	* plugin.cc (allow_unique_segment_for_sections): New function.
	(unique_segment_for_sections): New function.
	(Plugin::load): Add new functions to transfer vector.
	* Makefile.am (plugin_final_layout.readelf.stdout): Add readelf output.
	* Makefile.in: Regenerate.
	* testsuite/plugin_final_layout.sh: Check if unique segment
	functionality works.
	* testsuite/plugin_section_order.c (onload): Check if new interfaces
	are available.
	(allow_unique_segment_for_sections): New global.
	(unique_segment_for_sections): New global.
	(claim_file_hook): Call allow_unique_segment_for_sections.
	(all_symbols_read_hook): Call unique_segment_for_sections.


2012-08-24  Sriraman Tallam  <tmsriram@google.com>

	* plugin-api.h (ld_plugin_allow_unique_segment_for_sections):
	New interface.
	(ld_plugin_unique_segment_for_sections): New interface.
	(LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS): New enum val.
	(LDPT_UNIQUE_SEGMENT_FOR_SECTIONS): New enum val.
	(tv_allow_unique_segment_for_sections): New member.
	(tv_unique_segment_for_sections): New member.

1 files changed, 46 insertions, 0 deletions

diff --git a/gold/layout.h b/gold/layout.h
index fe5c696..94745a6 100644
--- a/gold/layout.h
+++ b/gold/layout.h
@@ -528,6 +528,31 @@ class Layout
   get_section_order_map()
   { return &this->section_order_map_; }
 
+  // Struct to store segment info when mapping some input sections to
+  // unique segments using linker plugins.  Mapping an input section to
+  // a unique segment is done by first placing such input sections in
+  // unique output sections and then mapping the output section to a
+  // unique segment.  NAME is the name of the output section.  FLAGS
+  // and ALIGN are the extra flags and alignment of the segment.
+  struct Unique_segment_info
+  {
+    // Identifier for the segment.  ELF segments dont have names.  This
+    // is used as the name of the output section mapped to the segment.
+    const char* name;
+    // Additional segment flags.
+    uint64_t flags;
+    // Segment alignment.
+    uint64_t align;
+  };
+
+  // Mapping from input section to segment.
+  typedef std::map<Const_section_id, Unique_segment_info*>
+  Section_segment_map;
+
+  // Maps section SECN to SEGMENT s.
+  void
+  insert_section_segment_map(Const_section_id secn, Unique_segment_info *s);
+  
   bool
   is_section_ordering_specified()
   { return this->section_ordering_specified_; }
@@ -536,6 +561,14 @@ class Layout
   set_section_ordering_specified()
   { this->section_ordering_specified_ = true; }
 
+  bool
+  is_unique_segment_for_sections_specified() const
+  { return this->unique_segment_for_sections_specified_; }
+
+  void
+  set_unique_segment_for_sections_specified()
+  { this->unique_segment_for_sections_specified_ = true; }
+
   // For incremental updates, allocate a block of memory from the
   // free list.  Find a block starting at or after MINOFF.
   off_t
@@ -1070,6 +1103,11 @@ class Layout
 		     elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
 		     Output_section_order order, bool is_relro);
 
+  // Clear the input section flags that should not be copied to the
+  // output section.
+  elfcpp::Elf_Xword
+  get_output_section_flags (elfcpp::Elf_Xword input_section_flags);
+
   // Choose the output section for NAME in RELOBJ.
   Output_section*
   choose_output_section(const Relobj* relobj, const char* name,
@@ -1336,6 +1374,9 @@ class Layout
   // True if the input sections in the output sections should be sorted
   // as specified in a section ordering file.
   bool section_ordering_specified_;
+  // True if some input sections need to be mapped to a unique segment,
+  // after being mapped to a unique Output_section.
+  bool unique_segment_for_sections_specified_;
   // In incremental build, holds information check the inputs and build the
   // .gnu_incremental_inputs section.
   Incremental_inputs* incremental_inputs_;
@@ -1350,6 +1391,11 @@ class Layout
   // Plugins specify section_ordering using this map.  This is set in
   // update_section_order in plugin.cc
   std::map<Section_id, unsigned int> section_order_map_;
+  // This maps an input section to a unique segment. This is done by first
+  // placing such input sections in unique output sections and then mapping
+  // the output section to a unique segment.  Unique_segment_info stores
+  // any additional flags and alignment of the new segment.
+  Section_segment_map section_segment_map_;
   // Hash a pattern to its position in the section ordering file.
   Unordered_map<std::string, unsigned int> input_section_position_;
   // Vector of glob only patterns in the section_ordering file.