binutils-gdb/gold/merge.cc

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// merge.cc -- handle section merging for gold
// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
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#include "gold.h"
#include <cstdlib>
#include <algorithm>
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#include "merge.h"
namespace gold
{
// Class Object_merge_map.
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// Destructor.
Object_merge_map::~Object_merge_map()
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{
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for (Section_merge_maps::iterator p = this->section_merge_maps_.begin();
p != this->section_merge_maps_.end();
++p)
delete p->second;
}
// Get the Input_merge_map to use for an input section, or NULL.
Object_merge_map::Input_merge_map*
Object_merge_map::get_input_merge_map(unsigned int shndx)
{
gold_assert(shndx != -1U);
if (shndx == this->first_shnum_)
return &this->first_map_;
if (shndx == this->second_shnum_)
return &this->second_map_;
Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx);
if (p != this->section_merge_maps_.end())
return p->second;
return NULL;
}
// Get or create the Input_merge_map to use for an input section.
Object_merge_map::Input_merge_map*
Object_merge_map::get_or_make_input_merge_map(const Merge_map* merge_map,
unsigned int shndx)
{
Input_merge_map* map = this->get_input_merge_map(shndx);
if (map != NULL)
{
// For a given input section in a given object, every mapping
// must be done with the same Merge_map.
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gold_assert(map->merge_map == merge_map);
return map;
}
// We need to create a new entry.
if (this->first_shnum_ == -1U)
{
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this->first_shnum_ = shndx;
this->first_map_.merge_map = merge_map;
return &this->first_map_;
}
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if (this->second_shnum_ == -1U)
{
this->second_shnum_ = shndx;
this->second_map_.merge_map = merge_map;
return &this->second_map_;
}
Input_merge_map* new_map = new Input_merge_map;
new_map->merge_map = merge_map;
this->section_merge_maps_[shndx] = new_map;
return new_map;
}
// Add a mapping.
void
Object_merge_map::add_mapping(const Merge_map* merge_map, unsigned int shndx,
section_offset_type input_offset,
section_size_type length,
section_offset_type output_offset)
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{
Input_merge_map* map = this->get_or_make_input_merge_map(merge_map, shndx);
// Try to merge the new entry in the last one we saw.
if (!map->entries.empty())
{
Input_merge_entry& entry(map->entries.back());
// Use section_size_type to avoid signed/unsigned warnings.
section_size_type input_offset_u = input_offset;
section_size_type output_offset_u = output_offset;
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// If this entry is not in order, we need to sort the vector
// before looking anything up.
if (input_offset_u < entry.input_offset + entry.length)
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{
gold_assert(input_offset < entry.input_offset);
gold_assert(input_offset_u + length
<= static_cast<section_size_type>(entry.input_offset));
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map->sorted = false;
}
else if (entry.input_offset + entry.length == input_offset_u
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&& (output_offset == -1
? entry.output_offset == -1
: entry.output_offset + entry.length == output_offset_u))
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{
entry.length += length;
return;
}
}
Input_merge_entry entry;
entry.input_offset = input_offset;
entry.length = length;
entry.output_offset = output_offset;
map->entries.push_back(entry);
}
// Get the output offset for an input address.
bool
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Object_merge_map::get_output_offset(const Merge_map* merge_map,
unsigned int shndx,
section_offset_type input_offset,
section_offset_type *output_offset)
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{
Input_merge_map* map = this->get_input_merge_map(shndx);
if (map == NULL
|| (merge_map != NULL && map->merge_map != merge_map))
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return false;
if (!map->sorted)
{
std::sort(map->entries.begin(), map->entries.end(),
Input_merge_compare());
map->sorted = true;
}
Input_merge_entry entry;
entry.input_offset = input_offset;
std::vector<Input_merge_entry>::const_iterator p =
std::lower_bound(map->entries.begin(), map->entries.end(),
entry, Input_merge_compare());
if (p == map->entries.end() || p->input_offset > input_offset)
{
if (p == map->entries.begin())
return false;
--p;
gold_assert(p->input_offset <= input_offset);
}
if (input_offset - p->input_offset
>= static_cast<section_offset_type>(p->length))
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return false;
*output_offset = p->output_offset;
if (*output_offset != -1)
*output_offset += (input_offset - p->input_offset);
return true;
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}
// Return whether this is the merge map for section SHNDX.
inline bool
Object_merge_map::is_merge_section_for(const Merge_map* merge_map,
unsigned int shndx)
{
Input_merge_map* map = this->get_input_merge_map(shndx);
return map != NULL && map->merge_map == merge_map;
}
// Initialize a mapping from input offsets to output addresses.
template<int size>
void
Object_merge_map::initialize_input_to_output_map(
unsigned int shndx,
typename elfcpp::Elf_types<size>::Elf_Addr starting_address,
Unordered_map<section_offset_type,
typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map)
{
Input_merge_map* map = this->get_input_merge_map(shndx);
gold_assert(map != NULL);
gold_assert(initialize_map->empty());
// We know how many entries we are going to add.
// reserve_unordered_map takes an expected count of buckets, not a
// count of elements, so double it to try to reduce collisions.
reserve_unordered_map(initialize_map, map->entries.size() * 2);
for (Input_merge_map::Entries::const_iterator p = map->entries.begin();
p != map->entries.end();
++p)
{
section_offset_type output_offset = p->output_offset;
if (output_offset != -1)
output_offset += starting_address;
else
{
// If we see a relocation against an address we have chosen
// to discard, we relocate to zero. FIXME: We could also
// issue a warning in this case; that would require
// reporting this somehow and checking it in the routines in
// reloc.h.
output_offset = 0;
}
initialize_map->insert(std::make_pair(p->input_offset, output_offset));
}
}
// Class Merge_map.
// Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input
// section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data
// in an output section.
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void
Merge_map::add_mapping(Relobj* object, unsigned int shndx,
section_offset_type offset, section_size_type length,
section_offset_type output_offset)
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{
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Object_merge_map* object_merge_map = object->merge_map();
if (object_merge_map == NULL)
{
object_merge_map = new Object_merge_map();
object->set_merge_map(object_merge_map);
}
object_merge_map->add_mapping(this, shndx, offset, length, output_offset);
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}
// Return the output offset for an input address. The input address
// is at offset OFFSET in section SHNDX in OBJECT. This sets
// *OUTPUT_OFFSET to the offset in the merged data in the output
// section. This returns true if the mapping is known, false
// otherwise.
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bool
Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,
section_offset_type offset,
section_offset_type* output_offset) const
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{
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Object_merge_map* object_merge_map = object->merge_map();
if (object_merge_map == NULL)
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return false;
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return object_merge_map->get_output_offset(this, shndx, offset,
output_offset);
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}
// Return whether this is the merge section for SHNDX in OBJECT.
bool
Merge_map::is_merge_section_for(const Relobj* object, unsigned int shndx) const
{
Object_merge_map* object_merge_map = object->merge_map();
if (object_merge_map == NULL)
return false;
return object_merge_map->is_merge_section_for(this, shndx);
}
// Class Output_merge_base.
// Return the output offset for an input offset. The input address is
// at offset OFFSET in section SHNDX in OBJECT. If we know the
// offset, set *POUTPUT and return true. Otherwise return false.
bool
Output_merge_base::do_output_offset(const Relobj* object,
unsigned int shndx,
section_offset_type offset,
section_offset_type* poutput) const
{
return this->merge_map_.get_output_offset(object, shndx, offset, poutput);
}
// Return whether this is the merge section for SHNDX in OBJECT.
bool
Output_merge_base::do_is_merge_section_for(const Relobj* object,
unsigned int shndx) const
{
return this->merge_map_.is_merge_section_for(object, shndx);
}
// Class Output_merge_data.
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// 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);
section_size_type entsize =
convert_to_section_size_type(this->pomd_->entsize());
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// Fowler/Noll/Vo (FNV) hash (type FNV-1a).
if (sizeof(size_t) == 8)
{
size_t result = static_cast<size_t>(14695981039346656037ULL);
for (section_size_type i = 0; i < entsize; ++i)
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{
result &= (size_t) *p++;
result *= 1099511628211ULL;
}
return result;
}
else
{
size_t result = 2166136261UL;
for (section_size_type i = 0; i < entsize; ++i)
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{
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)
{
section_size_type entsize = convert_to_section_size_type(this->entsize());
section_size_type addralign =
convert_to_section_size_type(this->addralign());
section_size_type addsize = std::max(entsize, addralign);
if (this->len_ + addsize > this->alc_)
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{
if (this->alc_ == 0)
this->alc_ = 128 * addsize;
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else
this->alc_ *= 2;
this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
if (this->p_ == NULL)
gold_nomem();
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}
memcpy(this->p_ + this->len_, p, entsize);
if (addsize > entsize)
memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);
this->len_ += addsize;
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}
// 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)
{
section_size_type len;
const unsigned char* p = object->section_contents(shndx, &len, false);
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section_size_type entsize = convert_to_section_size_type(this->entsize());
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if (len % entsize != 0)
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return false;
this->input_count_ += len / entsize;
for (section_size_type i = 0; i < len; i += entsize, p += entsize)
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{
// 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;
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k = *ins.first;
}
// Record the offset of this constant in the output section.
this->add_mapping(object, shndx, i, entsize, k);
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}
return true;
}
// Set the final data size in a merged output section with fixed size
// constants.
void
Output_merge_data::set_final_data_size()
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{
// Release the memory we don't need.
this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
// An Output_merge_data object may be empty and realloc is allowed
// to return a NULL pointer in this case. An Output_merge_data is empty
// if all its input sections have sizes that are not multiples of entsize.
gold_assert(this->p_ != NULL || this->len_ == 0);
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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_);
}
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// Write the data to a buffer.
void
Output_merge_data::do_write_to_buffer(unsigned char* buffer)
{
memcpy(buffer, this->p_, this->len_);
}
// Print merge stats to stderr.
void
Output_merge_data::do_print_merge_stats(const char* section_name)
{
fprintf(stderr,
_("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
program_name, section_name,
static_cast<unsigned long>(this->entsize()),
this->input_count_, this->hashtable_.size());
}
// Class Output_merge_string.
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// 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)
{
section_size_type len;
const unsigned char* pdata = object->section_contents(shndx, &len, false);
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const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
const Char_type* pend = p + len / sizeof(Char_type);
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if (len % sizeof(Char_type) != 0)
{
object->error(_("mergeable string section length not multiple of "
"character size"));
return false;
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}
size_t count = 0;
// The index I is in bytes, not characters.
section_size_type i = 0;
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while (i < len)
{
const Char_type* pl;
for (pl = p; *pl != 0; ++pl)
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{
if (pl >= pend)
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{
gold_warning(_("%s: last entry in mergeable string section '%s' "
"not null terminated"),
object->name().c_str(),
object->section_name(shndx).c_str());
break;
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}
}
Stringpool::Key key;
const Char_type* str = this->stringpool_.add_with_length(p, pl - p, true,
&key);
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section_size_type bytelen_with_null = ((pl - p) + 1) * sizeof(Char_type);
this->merged_strings_.push_back(Merged_string(object, shndx, i, str,
bytelen_with_null, key));
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p = pl + 1;
i += bytelen_with_null;
++count;
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}
this->input_count_ += count;
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return true;
}
// Finalize the mappings from the input sections to the output
// section, and return the final data size.
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template<typename Char_type>
section_size_type
Output_merge_string<Char_type>::finalize_merged_data()
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{
this->stringpool_.set_string_offsets();
for (typename Merged_strings::const_iterator p =
this->merged_strings_.begin();
p != this->merged_strings_.end();
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++p)
{
section_offset_type offset =
this->stringpool_.get_offset_from_key(p->stringpool_key);
this->add_mapping(p->object, p->shndx, p->offset, p->length, offset);
}
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// Save some memory. This also ensures that this function will work
// if called twice, as may happen if Layout::set_segment_offsets
// finds a better alignment.
this->merged_strings_.clear();
return this->stringpool_.get_strtab_size();
}
template<typename Char_type>
void
Output_merge_string<Char_type>::set_final_data_size()
{
const off_t final_data_size = this->finalize_merged_data();
this->set_data_size(final_data_size);
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}
// 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());
}
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// Write a merged string section to a buffer.
template<typename Char_type>
void
Output_merge_string<Char_type>::do_write_to_buffer(unsigned char* buffer)
{
this->stringpool_.write_to_buffer(buffer, this->data_size());
}
// Return the name of the types of string to use with
// do_print_merge_stats.
template<typename Char_type>
const char*
Output_merge_string<Char_type>::string_name()
{
gold_unreachable();
return NULL;
}
template<>
const char*
Output_merge_string<char>::string_name()
{
return "strings";
}
template<>
const char*
Output_merge_string<uint16_t>::string_name()
{
return "16-bit strings";
}
template<>
const char*
Output_merge_string<uint32_t>::string_name()
{
return "32-bit strings";
}
// Print merge stats to stderr.
template<typename Char_type>
void
Output_merge_string<Char_type>::do_print_merge_stats(const char* section_name)
{
char buf[200];
snprintf(buf, sizeof buf, "%s merged %s", section_name, this->string_name());
fprintf(stderr, _("%s: %s input: %zu\n"),
program_name, buf, this->input_count_);
this->stringpool_.print_stats(buf);
}
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// 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>;
#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
template
void
Object_merge_map::initialize_input_to_output_map<32>(
unsigned int shndx,
elfcpp::Elf_types<32>::Elf_Addr starting_address,
Unordered_map<section_offset_type, elfcpp::Elf_types<32>::Elf_Addr>*);
#endif
#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
template
void
Object_merge_map::initialize_input_to_output_map<64>(
unsigned int shndx,
elfcpp::Elf_types<64>::Elf_Addr starting_address,
Unordered_map<section_offset_type, elfcpp::Elf_types<64>::Elf_Addr>*);
#endif
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} // End namespace gold.