Add support for SHF_MERGE sections.

1 files changed, 333 insertions, 0 deletions

diff --git a/gold/merge.cc b/gold/merge.cc
new file mode 100644
index 0000000..7af4faa
--- /dev/null
+++ b/gold/merge.cc
@@ -0,0 +1,333 @@
+// merge.cc -- handle section merging for gold
+
+#include "gold.h"
+
+#include <cstdlib>
+
+#include "merge.h"
+
+namespace gold
+{
+
+// Sort the entries in a merge mapping.  The key is an input object, a
+// section index in that object, and an offset in that section.
+
+bool
+Output_merge_base::Merge_key_less::operator()(const Merge_key& mk1,
+					      const Merge_key& mk2) const
+{
+  // The order of different objects and different sections doesn't
+  // matter.  We want to get consistent results across links so we
+  // don't use pointer comparison.
+  if (mk1.object != mk2.object)
+    return mk1.object->name() < mk2.object->name();
+  if (mk1.shndx != mk2.shndx)
+    return mk1.shndx < mk2.shndx;
+  return mk1.offset < mk2.offset;
+}
+
+// Add a mapping from an OFFSET in input section SHNDX in object
+// OBJECT to an OUTPUT_OFFSET in a merged output section.  This
+// manages the mapping used to resolve relocations against merged
+// sections.
+
+void
+Output_merge_base::add_mapping(Relobj* object, unsigned int shndx,
+			       off_t offset, off_t output_offset)
+{
+  Merge_key mk;
+  mk.object = object;
+  mk.shndx = shndx;
+  mk.offset = offset;
+  std::pair<Merge_map::iterator, bool> ins =
+    this->merge_map_.insert(std::make_pair(mk, output_offset));
+  gold_assert(ins.second);
+}
+
+// Return the output address for an input address.  The input address
+// is at offset OFFSET in section SHNDX in OBJECT.
+// OUTPUT_SECTION_ADDRESS is the address of the output section.  If we
+// know the address, set *POUTPUT and return true.  Otherwise return
+// false.
+
+bool
+Output_merge_base::do_output_address(const Relobj* object, unsigned int shndx,
+				     off_t offset,
+				     uint64_t output_section_address,
+				     uint64_t* poutput) const
+{
+  gold_assert(output_section_address == this->address());
+
+  Merge_key mk;
+  mk.object = object;
+  mk.shndx = shndx;
+  mk.offset = offset;
+  Merge_map::const_iterator p = this->merge_map_.lower_bound(mk);
+
+  // If MK is not in the map, lower_bound returns the next iterator
+  // larger than it.
+  if (p->first.object != object
+      || p->first.shndx != shndx
+      || p->first.offset != offset)
+    {
+      if (p == this->merge_map_.begin())
+	return false;
+      --p;
+    }
+
+  if (p->first.object != object || p->first.shndx != shndx)
+    return false;
+
+  // Any input section is fully mapped: we don't need to know the size
+  // of the range starting at P->FIRST.OFFSET.
+  *poutput = output_section_address + p->second + (offset - p->first.offset);
+  return true;
+}
+
+// Compute the hash code for a fixed-size constant.
+
+size_t
+Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
+{
+  const unsigned char* p = this->pomd_->constant(k);
+  uint64_t entsize = this->pomd_->entsize();
+
+  // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
+  if (sizeof(size_t) == 8)
+    {
+      size_t result = static_cast<size_t>(14695981039346656037ULL);
+      for (uint64_t i = 0; i < entsize; ++i)
+	{
+	  result &= (size_t) *p++;
+	  result *= 1099511628211ULL;
+	}
+      return result;
+    }
+  else
+    {
+      size_t result = 2166136261UL;
+      for (uint64_t i = 0; i < entsize; ++i)
+	{
+	  result ^= (size_t) *p++;
+	  result *= 16777619UL;
+	}
+      return result;
+    }
+}
+
+// Return whether one hash table key equals another.
+
+bool
+Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
+					     Merge_data_key k2) const
+{
+  const unsigned char* p1 = this->pomd_->constant(k1);
+  const unsigned char* p2 = this->pomd_->constant(k2);
+  return memcmp(p1, p2, this->pomd_->entsize()) == 0;
+}
+
+// Add a constant to the end of the section contents.
+
+void
+Output_merge_data::add_constant(const unsigned char* p)
+{
+  uint64_t entsize = this->entsize();
+  if (this->len_ + entsize > this->alc_)
+    {
+      if (this->alc_ == 0)
+	this->alc_ = 128 * entsize;
+      else
+	this->alc_ *= 2;
+      this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
+      if (this->p_ == NULL)
+	gold_fatal("out of memory", true);
+    }
+
+  memcpy(this->p_ + this->len_, p, entsize);
+  this->len_ += entsize;
+}
+
+// Add the input section SHNDX in OBJECT to a merged output section
+// which holds fixed length constants.  Return whether we were able to
+// handle the section; if not, it will be linked as usual without
+// constant merging.
+
+bool
+Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
+{
+  off_t len;
+  const unsigned char* p = object->section_contents(shndx, &len);
+
+  uint64_t entsize = this->entsize();
+
+  if (len % entsize != 0)
+    return false;
+
+  for (off_t i = 0; i < len; i += entsize, p += entsize)
+    {
+      // Add the constant to the section contents.  If we find that it
+      // is already in the hash table, we will remove it again.
+      Merge_data_key k = this->len_;
+      this->add_constant(p);
+
+      std::pair<Merge_data_hashtable::iterator, bool> ins =
+	this->hashtable_.insert(k);
+
+      if (!ins.second)
+	{
+	  // Key was already present.  Remove the copy we just added.
+	  this->len_ -= entsize;
+	  k = *ins.first;
+	}
+
+      // Record the offset of this constant in the output section.
+      this->add_mapping(object, shndx, i, k);
+    }
+
+  return true;
+}
+
+// Set the final data size in a merged output section with fixed size
+// constants.
+
+void
+Output_merge_data::do_set_address(uint64_t, off_t)
+{
+  // Release the memory we don't need.
+  this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
+  gold_assert(this->p_ != NULL);
+  this->set_data_size(this->len_);
+}
+
+// Write the data of a merged output section with fixed size constants
+// to the file.
+
+void
+Output_merge_data::do_write(Output_file* of)
+{
+  of->write(this->offset(), this->p_, this->len_);
+}
+
+// Compute a hash code for a Merge_string_key, which is an object, a
+// section index, and an offset.
+
+template<typename Char_type>
+size_t
+Output_merge_string<Char_type>::Merge_string_key_hash::operator()(
+    const Merge_string_key& key) const
+{
+  // This is a very simple minded hash code.  Fix it if it we get too
+  // many collisions.
+  const std::string& oname(key.object->name());
+  return oname[0] + oname.length() + key.shndx + key.offset;
+}
+
+// Compare two Merge_string_keys for equality.
+
+template<typename Char_type>
+bool
+Output_merge_string<Char_type>::Merge_string_key_eq::operator()(
+    const Merge_string_key& k1, const Merge_string_key& k2) const
+{
+  return (k1.object == k2.object
+	  && k1.shndx == k2.shndx
+	  && k1.offset == k2.offset);
+}
+
+// Add an input section to a merged string section.
+
+template<typename Char_type>
+bool
+Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
+						     unsigned int shndx)
+{
+  off_t len;
+  const unsigned char* pdata = object->section_contents(shndx, &len);
+
+  const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
+
+  if (len % sizeof(Char_type) != 0)
+    {
+      fprintf(stderr,
+	      _("%s: %s: mergeable string section length not multiple of "
+		"character size\n"),
+	      program_name, object->name().c_str());
+      gold_exit(false);
+    }
+  len /= sizeof(Char_type);
+
+  off_t i = 0;
+  while (i < len)
+    {
+      off_t plen = 0;
+      for (const Char_type* pl = p; *pl != 0; ++pl)
+	{
+	  ++plen;
+	  if (i + plen >= len)
+	    {
+	      fprintf(stderr,
+		      _("%s: %s: entry in mergeable string section "
+			"not null terminated\n"),
+		      program_name, object->name().c_str());
+	      gold_exit(false);
+	    }
+	}
+
+      const Char_type* str = this->stringpool_.add(p, NULL);
+
+      Merge_string_key k(object, shndx, i);
+      typename Merge_string_hashtable::value_type v(k, str);
+      bool b = this->hashtable_.insert(v).second;
+      gold_assert(b);
+
+      p += plen + 1;
+      i += plen + 1;
+    }
+
+  return true;
+}
+
+// Set the final data size of a merged string section.  This is where
+// we finalize the mappings from the input sections to the output
+// section.
+
+template<typename Char_type>
+void
+Output_merge_string<Char_type>::do_set_address(uint64_t, off_t)
+{
+  this->stringpool_.set_string_offsets();
+
+  for (typename Merge_string_hashtable::const_iterator p =
+	 this->hashtable_.begin();
+       p != this->hashtable_.end();
+       ++p)
+    this->add_mapping(p->first.object, p->first.shndx, p->first.offset,
+		      this->stringpool_.get_offset(p->second));
+
+  this->set_data_size(this->stringpool_.get_strtab_size());
+
+  // Save some memory.
+  this->hashtable_.clear();
+}
+
+// Write out a merged string section.
+
+template<typename Char_type>
+void
+Output_merge_string<Char_type>::do_write(Output_file* of)
+{
+  this->stringpool_.write(of, this->offset());
+}
+
+// Instantiate the templates we need.
+
+template
+class Output_merge_string<char>;
+
+template
+class Output_merge_string<uint16_t>;
+
+template
+class Output_merge_string<uint32_t>;
+
+} // End namespace gold.