binutils-gdb/gold/merge.cc

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// merge.cc -- handle section merging for gold
// Copyright 2006, 2007 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 Merge_map::Merge_key_less.
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// 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
Merge_map::Merge_key_less::operator()(const Merge_key& mk1,
const Merge_key& mk2) const
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{
// 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)
{
// Two different object files can have the same name: if foo.a
// includes both bar/qux.o and baz/qux.o, then both end up with
// the name foo.a(qux.o). But it's impossible for two different
// object files to have both the same name and the same offset.
if (mk1.object->offset() != mk2.object->offset())
return mk1.object->offset() < mk2.object->offset();
return mk1.object->name() < mk2.object->name();
}
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if (mk1.shndx != mk2.shndx)
return mk1.shndx < mk2.shndx;
return mk1.offset < mk2.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 a merged
// output section.
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void
Merge_map::add_mapping(Relobj* object, unsigned int shndx,
off_t offset, off_t length, off_t output_offset)
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{
Merge_key mk;
mk.object = object;
mk.shndx = shndx;
mk.offset = offset;
Merge_value mv;
mv.length = length;
mv.output_offset = output_offset;
std::pair<Merge_mapping::iterator, bool> ins =
this->merge_map_.insert(std::make_pair(mk, mv));
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gold_assert(ins.second);
}
// 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 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,
off_t offset, off_t* output_offset) const
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{
Merge_key mk;
mk.object = object;
mk.shndx = shndx;
mk.offset = offset;
Merge_mapping::const_iterator p = this->merge_map_.lower_bound(mk);
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// If MK is not in the map, lower_bound returns the next iterator
// larger than it.
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if (p == this->merge_map_.end()
|| p->first.object != object
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|| 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;
if (offset - p->first.offset >= p->second.length)
return false;
*output_offset = p->second.output_offset;
if (*output_offset != -1)
*output_offset += (offset - p->first.offset);
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return true;
}
// 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,
off_t offset,
off_t* poutput) const
{
return this->merge_map_.get_output_offset(object, shndx, offset, poutput);
}
// 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);
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();
uint64_t addsize = std::max(entsize, this->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)
{
off_t len;
const unsigned char* p = object->section_contents(shndx, &len, false);
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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, 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::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_);
}
// 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)
{
off_t 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);
if (len % sizeof(Char_type) != 0)
{
object->error(_("mergeable string section length not multiple of "
"character size"));
return false;
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}
// The index I is in bytes, not characters.
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off_t i = 0;
while (i < len)
{
off_t plen = 0;
for (const Char_type* pl = p; *pl != 0; ++pl)
{
// The length PLEN is in characters, not bytes.
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++plen;
if (i + plen * static_cast<off_t>(sizeof(Char_type)) >= len)
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{
object->error(_("entry in mergeable string section "
"not null terminated"));
break;
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}
}
const Char_type* str = this->stringpool_.add(p, true, NULL);
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off_t bytelen_with_null = (plen + 1) * sizeof(Char_type);
this->merged_strings_.push_back(Merged_string(object, shndx, i, str,
bytelen_with_null));
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p += plen + 1;
i += bytelen_with_null;
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}
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 Merged_strings::const_iterator p =
this->merged_strings_.begin();
p != this->merged_strings_.end();
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++p)
this->add_mapping(p->object, p->shndx, p->offset, p->length,
this->stringpool_.get_offset(p->string));
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this->set_data_size(this->stringpool_.get_strtab_size());
// Save some memory.
this->merged_strings_.clear();
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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());
}
// 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.