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, 77 insertions, 1 deletions

diff --git a/gold/plugin.cc b/gold/plugin.cc
index 5aadc55..c39e11ec 100644
--- a/gold/plugin.cc
+++ b/gold/plugin.cc
@@ -115,6 +115,15 @@ update_section_order(const struct ld_plugin_section *section_list,
 static enum ld_plugin_status
 allow_section_ordering();
 
+static enum ld_plugin_status
+allow_unique_segment_for_sections();
+
+static enum ld_plugin_status
+unique_segment_for_sections(const char* segment_name,
+			    uint64_t flags,
+			    uint64_t align,
+			    const struct ld_plugin_section *section_list,
+			    unsigned int num_sections);
 };
 
 #endif // ENABLE_PLUGINS
@@ -159,7 +168,7 @@ Plugin::load()
   sscanf(ver, "%d.%d", &major, &minor);
 
   // Allocate and populate a transfer vector.
-  const int tv_fixed_size = 24;
+  const int tv_fixed_size = 26;
 
   int tv_size = this->args_.size() + tv_fixed_size;
   ld_plugin_tv* tv = new ld_plugin_tv[tv_size];
@@ -273,6 +282,15 @@ Plugin::load()
   tv[i].tv_u.tv_allow_section_ordering = allow_section_ordering;
 
   ++i;
+  tv[i].tv_tag = LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS;
+  tv[i].tv_u.tv_allow_unique_segment_for_sections
+    = allow_unique_segment_for_sections;
+
+  ++i;
+  tv[i].tv_tag = LDPT_UNIQUE_SEGMENT_FOR_SECTIONS;
+  tv[i].tv_u.tv_unique_segment_for_sections = unique_segment_for_sections;
+
+  ++i;
   tv[i].tv_tag = LDPT_NULL;
   tv[i].tv_u.tv_val = 0;
 
@@ -1685,6 +1703,64 @@ allow_section_ordering()
   return LDPS_OK;
 }
 
+// Let the linker know that a subset of sections could be mapped
+// to a unique segment.
+
+static enum ld_plugin_status
+allow_unique_segment_for_sections()
+{
+  gold_assert(parameters->options().has_plugins());
+  Layout* layout = parameters->options().plugins()->layout();
+  layout->set_unique_segment_for_sections_specified();
+  return LDPS_OK;
+}
+
+// This function should map the list of sections specified in the
+// SECTION_LIST to a unique segment.  ELF segments do not have names
+// and the NAME is used to identify Output Section which should contain
+// the list of sections.  This Output Section will then be mapped to
+// a unique segment.  FLAGS is used to specify if any additional segment
+// flags need to be set.  For instance, a specific segment flag can be
+// set to identify this segment.  Unsetting segment flags is not possible.
+// ALIGN specifies the alignment of the segment.
+
+static enum ld_plugin_status
+unique_segment_for_sections(const char* segment_name,
+			    uint64_t flags,
+			    uint64_t align,
+			    const struct ld_plugin_section* section_list,
+			    unsigned int num_sections)
+{
+  gold_assert(parameters->options().has_plugins());
+
+  if (num_sections == 0)
+    return LDPS_OK;
+
+  if (section_list == NULL)
+    return LDPS_ERR;
+
+  Layout* layout = parameters->options().plugins()->layout();
+  gold_assert (layout != NULL);
+
+  Layout::Unique_segment_info* s = new Layout::Unique_segment_info;
+  s->name = segment_name;
+  s->flags = flags;
+  s->align = align;
+
+  for (unsigned int i = 0; i < num_sections; ++i)
+    {
+      Object* obj = parameters->options().plugins()->get_elf_object(
+          section_list[i].handle);
+      if (obj == NULL)
+	return LDPS_BAD_HANDLE;
+      unsigned int shndx = section_list[i].shndx;
+      Const_section_id secn_id(obj, shndx);
+      layout->insert_section_segment_map(secn_id, s);
+    }
+
+  return LDPS_OK;
+}
+
 #endif // ENABLE_PLUGINS
 
 // Allocate a Pluginobj object of the appropriate size and endianness.