1 // merge.cc -- handle section merging for gold
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
33 // Sort the entries in a merge mapping. The key is an input object, a
34 // section index in that object, and an offset in that section.
37 Output_merge_base::Merge_key_less::operator()(const Merge_key& mk1,
38 const Merge_key& mk2) const
40 // The order of different objects and different sections doesn't
41 // matter. We want to get consistent results across links so we
42 // don't use pointer comparison.
43 if (mk1.object != mk2.object)
45 // Two different object files can have the same name: if foo.a
46 // includes both bar/qux.o and baz/qux.o, then both end up with
47 // the name foo.a(qux.o). But it's impossible for two different
48 // object files to have both the same name and the same offset.
49 if (mk1.object->offset() != mk2.object->offset())
50 return mk1.object->offset() < mk2.object->offset();
51 return mk1.object->name() < mk2.object->name();
53 if (mk1.shndx != mk2.shndx)
54 return mk1.shndx < mk2.shndx;
55 return mk1.offset < mk2.offset;
58 // Add a mapping from an OFFSET in input section SHNDX in object
59 // OBJECT to an OUTPUT_OFFSET in a merged output section. This
60 // manages the mapping used to resolve relocations against merged
64 Output_merge_base::add_mapping(Relobj* object, unsigned int shndx,
65 off_t offset, off_t output_offset)
71 std::pair<Merge_map::iterator, bool> ins =
72 this->merge_map_.insert(std::make_pair(mk, output_offset));
73 gold_assert(ins.second);
76 // Return the output address for an input address. The input address
77 // is at offset OFFSET in section SHNDX in OBJECT.
78 // OUTPUT_SECTION_ADDRESS is the address of the output section. If we
79 // know the address, set *POUTPUT and return true. Otherwise return
83 Output_merge_base::do_output_address(const Relobj* object, unsigned int shndx,
85 uint64_t output_section_address,
86 uint64_t* poutput) const
88 gold_assert(output_section_address == this->address());
94 Merge_map::const_iterator p = this->merge_map_.lower_bound(mk);
96 // If MK is not in the map, lower_bound returns the next iterator
98 if (p == this->merge_map_.end()
99 || p->first.object != object
100 || p->first.shndx != shndx
101 || p->first.offset != offset)
103 if (p == this->merge_map_.begin())
108 if (p->first.object != object || p->first.shndx != shndx)
111 // Any input section is fully mapped: we don't need to know the size
112 // of the range starting at P->FIRST.OFFSET.
113 *poutput = output_section_address + p->second + (offset - p->first.offset);
117 // Compute the hash code for a fixed-size constant.
120 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
122 const unsigned char* p = this->pomd_->constant(k);
123 uint64_t entsize = this->pomd_->entsize();
125 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
126 if (sizeof(size_t) == 8)
128 size_t result = static_cast<size_t>(14695981039346656037ULL);
129 for (uint64_t i = 0; i < entsize; ++i)
131 result &= (size_t) *p++;
132 result *= 1099511628211ULL;
138 size_t result = 2166136261UL;
139 for (uint64_t i = 0; i < entsize; ++i)
141 result ^= (size_t) *p++;
142 result *= 16777619UL;
148 // Return whether one hash table key equals another.
151 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
152 Merge_data_key k2) const
154 const unsigned char* p1 = this->pomd_->constant(k1);
155 const unsigned char* p2 = this->pomd_->constant(k2);
156 return memcmp(p1, p2, this->pomd_->entsize()) == 0;
159 // Add a constant to the end of the section contents.
162 Output_merge_data::add_constant(const unsigned char* p)
164 uint64_t entsize = this->entsize();
165 uint64_t addsize = std::max(entsize, this->addralign());
166 if (this->len_ + addsize > this->alc_)
169 this->alc_ = 128 * addsize;
172 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
173 if (this->p_ == NULL)
177 memcpy(this->p_ + this->len_, p, entsize);
178 if (addsize > entsize)
179 memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);
180 this->len_ += addsize;
183 // Add the input section SHNDX in OBJECT to a merged output section
184 // which holds fixed length constants. Return whether we were able to
185 // handle the section; if not, it will be linked as usual without
189 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
192 const unsigned char* p = object->section_contents(shndx, &len, false);
194 uint64_t entsize = this->entsize();
196 if (len % entsize != 0)
199 for (off_t i = 0; i < len; i += entsize, p += entsize)
201 // Add the constant to the section contents. If we find that it
202 // is already in the hash table, we will remove it again.
203 Merge_data_key k = this->len_;
204 this->add_constant(p);
206 std::pair<Merge_data_hashtable::iterator, bool> ins =
207 this->hashtable_.insert(k);
211 // Key was already present. Remove the copy we just added.
212 this->len_ -= entsize;
216 // Record the offset of this constant in the output section.
217 this->add_mapping(object, shndx, i, k);
223 // Set the final data size in a merged output section with fixed size
227 Output_merge_data::do_set_address(uint64_t, off_t)
229 // Release the memory we don't need.
230 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
231 gold_assert(this->p_ != NULL);
232 this->set_data_size(this->len_);
235 // Write the data of a merged output section with fixed size constants
239 Output_merge_data::do_write(Output_file* of)
241 of->write(this->offset(), this->p_, this->len_);
244 // Add an input section to a merged string section.
246 template<typename Char_type>
248 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
252 const unsigned char* pdata = object->section_contents(shndx, &len, false);
254 const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
256 if (len % sizeof(Char_type) != 0)
258 object->error(_("mergeable string section length not multiple of "
262 len /= sizeof(Char_type);
268 for (const Char_type* pl = p; *pl != 0; ++pl)
273 object->error(_("entry in mergeable string section "
274 "not null terminated"));
279 const Char_type* str = this->stringpool_.add(p, true, NULL);
281 this->merged_strings_.push_back(Merged_string(object, shndx, i, str));
290 // Set the final data size of a merged string section. This is where
291 // we finalize the mappings from the input sections to the output
294 template<typename Char_type>
296 Output_merge_string<Char_type>::do_set_address(uint64_t, off_t)
298 this->stringpool_.set_string_offsets();
300 for (typename Merged_strings::const_iterator p =
301 this->merged_strings_.begin();
302 p != this->merged_strings_.end();
304 this->add_mapping(p->object, p->shndx, p->offset,
305 this->stringpool_.get_offset(p->string));
307 this->set_data_size(this->stringpool_.get_strtab_size());
310 this->merged_strings_.clear();
313 // Write out a merged string section.
315 template<typename Char_type>
317 Output_merge_string<Char_type>::do_write(Output_file* of)
319 this->stringpool_.write(of, this->offset());
322 // Instantiate the templates we need.
325 class Output_merge_string<char>;
328 class Output_merge_string<uint16_t>;
331 class Output_merge_string<uint32_t>;
333 } // End namespace gold.