1 // merge.cc -- handle section merging for gold
3 // Copyright (C) 2006-2015 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.
29 #include "compressed_output.h"
34 // Class Object_merge_map.
38 Object_merge_map::~Object_merge_map()
40 for (Section_merge_maps::iterator p
= this->section_merge_maps_
.begin();
41 p
!= this->section_merge_maps_
.end();
46 // Get the Input_merge_map to use for an input section, or NULL.
48 const Object_merge_map::Input_merge_map
*
49 Object_merge_map::get_input_merge_map(unsigned int shndx
) const
51 gold_assert(shndx
!= -1U);
52 if (shndx
== this->first_shnum_
)
53 return &this->first_map_
;
54 if (shndx
== this->second_shnum_
)
55 return &this->second_map_
;
56 Section_merge_maps::const_iterator p
= this->section_merge_maps_
.find(shndx
);
57 if (p
!= this->section_merge_maps_
.end())
62 // Get or create the Input_merge_map to use for an input section.
64 Object_merge_map::Input_merge_map
*
65 Object_merge_map::get_or_make_input_merge_map(
66 const Output_section_data
* output_data
, unsigned int shndx
) {
67 Input_merge_map
* map
= this->get_input_merge_map(shndx
);
70 // For a given input section in a given object, every mapping
71 // must be done with the same Merge_map.
72 gold_assert(map
->output_data
== output_data
);
76 // We need to create a new entry.
77 if (this->first_shnum_
== -1U)
79 this->first_shnum_
= shndx
;
80 this->first_map_
.output_data
= output_data
;
81 return &this->first_map_
;
83 if (this->second_shnum_
== -1U)
85 this->second_shnum_
= shndx
;
86 this->second_map_
.output_data
= output_data
;
87 return &this->second_map_
;
90 Input_merge_map
* new_map
= new Input_merge_map
;
91 new_map
->output_data
= output_data
;
92 this->section_merge_maps_
[shndx
] = new_map
;
99 Object_merge_map::add_mapping(const Output_section_data
* output_data
,
101 section_offset_type input_offset
,
102 section_size_type length
,
103 section_offset_type output_offset
)
105 Input_merge_map
* map
= this->get_or_make_input_merge_map(output_data
, shndx
);
106 map
->add_mapping(input_offset
, length
, output_offset
);
110 Object_merge_map::Input_merge_map::add_mapping(
111 section_offset_type input_offset
, section_size_type length
,
112 section_offset_type output_offset
) {
113 // Try to merge the new entry in the last one we saw.
114 if (!this->entries
.empty())
116 Input_merge_entry
& entry(this->entries
.back());
118 // Use section_size_type to avoid signed/unsigned warnings.
119 section_size_type input_offset_u
= input_offset
;
120 section_size_type output_offset_u
= output_offset
;
122 // If this entry is not in order, we need to sort the vector
123 // before looking anything up.
124 if (input_offset_u
< entry
.input_offset
+ entry
.length
)
126 gold_assert(input_offset
< entry
.input_offset
);
127 gold_assert(input_offset_u
+ length
128 <= static_cast<section_size_type
>(entry
.input_offset
));
129 this->sorted
= false;
131 else if (entry
.input_offset
+ entry
.length
== input_offset_u
132 && (output_offset
== -1
133 ? entry
.output_offset
== -1
134 : entry
.output_offset
+ entry
.length
== output_offset_u
))
136 entry
.length
+= length
;
141 Input_merge_entry entry
;
142 entry
.input_offset
= input_offset
;
143 entry
.length
= length
;
144 entry
.output_offset
= output_offset
;
145 this->entries
.push_back(entry
);
148 // Get the output offset for an input address.
151 Object_merge_map::get_output_offset(unsigned int shndx
,
152 section_offset_type input_offset
,
153 section_offset_type
* output_offset
)
155 Input_merge_map
* map
= this->get_input_merge_map(shndx
);
161 std::sort(map
->entries
.begin(), map
->entries
.end(),
162 Input_merge_compare());
166 Input_merge_entry entry
;
167 entry
.input_offset
= input_offset
;
168 std::vector
<Input_merge_entry
>::const_iterator p
=
169 std::upper_bound(map
->entries
.begin(), map
->entries
.end(),
170 entry
, Input_merge_compare());
171 if (p
== map
->entries
.begin())
174 gold_assert(p
->input_offset
<= input_offset
);
176 if (input_offset
- p
->input_offset
177 >= static_cast<section_offset_type
>(p
->length
))
180 *output_offset
= p
->output_offset
;
181 if (*output_offset
!= -1)
182 *output_offset
+= (input_offset
- p
->input_offset
);
186 // Return whether this is the merge map for section SHNDX.
188 const Output_section_data
*
189 Object_merge_map::find_merge_section(unsigned int shndx
) const {
190 const Object_merge_map::Input_merge_map
* map
=
191 this->get_input_merge_map(shndx
);
194 return map
->output_data
;
197 // Initialize a mapping from input offsets to output addresses.
201 Object_merge_map::initialize_input_to_output_map(
203 typename
elfcpp::Elf_types
<size
>::Elf_Addr starting_address
,
204 Unordered_map
<section_offset_type
,
205 typename
elfcpp::Elf_types
<size
>::Elf_Addr
>* initialize_map
)
207 Input_merge_map
* map
= this->get_input_merge_map(shndx
);
208 gold_assert(map
!= NULL
);
210 gold_assert(initialize_map
->empty());
211 // We know how many entries we are going to add.
212 // reserve_unordered_map takes an expected count of buckets, not a
213 // count of elements, so double it to try to reduce collisions.
214 reserve_unordered_map(initialize_map
, map
->entries
.size() * 2);
216 for (Input_merge_map::Entries::const_iterator p
= map
->entries
.begin();
217 p
!= map
->entries
.end();
220 section_offset_type output_offset
= p
->output_offset
;
221 if (output_offset
!= -1)
222 output_offset
+= starting_address
;
225 // If we see a relocation against an address we have chosen
226 // to discard, we relocate to zero. FIXME: We could also
227 // issue a warning in this case; that would require
228 // reporting this somehow and checking it in the routines in
232 initialize_map
->insert(std::make_pair(p
->input_offset
, output_offset
));
236 // Class Output_merge_base.
238 // Return the output offset for an input offset. The input address is
239 // at offset OFFSET in section SHNDX in OBJECT. If we know the
240 // offset, set *POUTPUT and return true. Otherwise return false.
243 Output_merge_base::do_output_offset(const Relobj
* object
,
245 section_offset_type offset
,
246 section_offset_type
* poutput
) const
248 return object
->merge_output_offset(shndx
, offset
, poutput
);
251 // Record a merged input section for script processing.
254 Output_merge_base::record_input_section(Relobj
* relobj
, unsigned int shndx
)
256 gold_assert(this->keeps_input_sections_
&& relobj
!= NULL
);
257 // If this is the first input section, record it. We need do this because
258 // this->input_sections_ is unordered.
259 if (this->first_relobj_
== NULL
)
261 this->first_relobj_
= relobj
;
262 this->first_shndx_
= shndx
;
265 std::pair
<Input_sections::iterator
, bool> result
=
266 this->input_sections_
.insert(Section_id(relobj
, shndx
));
267 // We should insert a merge section once only.
268 gold_assert(result
.second
);
271 // Class Output_merge_data.
273 // Compute the hash code for a fixed-size constant.
276 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k
) const
278 const unsigned char* p
= this->pomd_
->constant(k
);
279 section_size_type entsize
=
280 convert_to_section_size_type(this->pomd_
->entsize());
282 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
283 if (sizeof(size_t) == 8)
285 size_t result
= static_cast<size_t>(14695981039346656037ULL);
286 for (section_size_type i
= 0; i
< entsize
; ++i
)
288 result
&= (size_t) *p
++;
289 result
*= 1099511628211ULL;
295 size_t result
= 2166136261UL;
296 for (section_size_type i
= 0; i
< entsize
; ++i
)
298 result
^= (size_t) *p
++;
299 result
*= 16777619UL;
305 // Return whether one hash table key equals another.
308 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1
,
309 Merge_data_key k2
) const
311 const unsigned char* p1
= this->pomd_
->constant(k1
);
312 const unsigned char* p2
= this->pomd_
->constant(k2
);
313 return memcmp(p1
, p2
, this->pomd_
->entsize()) == 0;
316 // Add a constant to the end of the section contents.
319 Output_merge_data::add_constant(const unsigned char* p
)
321 section_size_type entsize
= convert_to_section_size_type(this->entsize());
322 section_size_type addralign
=
323 convert_to_section_size_type(this->addralign());
324 section_size_type addsize
= std::max(entsize
, addralign
);
325 if (this->len_
+ addsize
> this->alc_
)
328 this->alc_
= 128 * addsize
;
331 this->p_
= static_cast<unsigned char*>(realloc(this->p_
, this->alc_
));
332 if (this->p_
== NULL
)
336 memcpy(this->p_
+ this->len_
, p
, entsize
);
337 if (addsize
> entsize
)
338 memset(this->p_
+ this->len_
+ entsize
, 0, addsize
- entsize
);
339 this->len_
+= addsize
;
342 // Add the input section SHNDX in OBJECT to a merged output section
343 // which holds fixed length constants. Return whether we were able to
344 // handle the section; if not, it will be linked as usual without
348 Output_merge_data::do_add_input_section(Relobj
* object
, unsigned int shndx
)
350 section_size_type len
;
352 const unsigned char* p
= object
->decompressed_section_contents(shndx
, &len
,
355 section_size_type entsize
= convert_to_section_size_type(this->entsize());
357 if (len
% entsize
!= 0)
364 this->input_count_
+= len
/ entsize
;
366 Object_merge_map
* merge_map
= object
->get_or_create_merge_map();
367 Object_merge_map::Input_merge_map
* input_merge_map
=
368 merge_map
->get_or_make_input_merge_map(this, shndx
);
370 for (section_size_type i
= 0; i
< len
; i
+= entsize
, p
+= entsize
)
372 // Add the constant to the section contents. If we find that it
373 // is already in the hash table, we will remove it again.
374 Merge_data_key k
= this->len_
;
375 this->add_constant(p
);
377 std::pair
<Merge_data_hashtable::iterator
, bool> ins
=
378 this->hashtable_
.insert(k
);
382 // Key was already present. Remove the copy we just added.
383 this->len_
-= entsize
;
387 // Record the offset of this constant in the output section.
388 input_merge_map
->add_mapping(i
, entsize
, k
);
391 // For script processing, we keep the input sections.
392 if (this->keeps_input_sections())
393 record_input_section(object
, shndx
);
401 // Set the final data size in a merged output section with fixed size
405 Output_merge_data::set_final_data_size()
407 // Release the memory we don't need.
408 this->p_
= static_cast<unsigned char*>(realloc(this->p_
, this->len_
));
409 // An Output_merge_data object may be empty and realloc is allowed
410 // to return a NULL pointer in this case. An Output_merge_data is empty
411 // if all its input sections have sizes that are not multiples of entsize.
412 gold_assert(this->p_
!= NULL
|| this->len_
== 0);
413 this->set_data_size(this->len_
);
416 // Write the data of a merged output section with fixed size constants
420 Output_merge_data::do_write(Output_file
* of
)
422 of
->write(this->offset(), this->p_
, this->len_
);
425 // Write the data to a buffer.
428 Output_merge_data::do_write_to_buffer(unsigned char* buffer
)
430 memcpy(buffer
, this->p_
, this->len_
);
433 // Print merge stats to stderr.
436 Output_merge_data::do_print_merge_stats(const char* section_name
)
439 _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
440 program_name
, section_name
,
441 static_cast<unsigned long>(this->entsize()),
442 this->input_count_
, this->hashtable_
.size());
445 // Class Output_merge_string.
447 // Add an input section to a merged string section.
449 template<typename Char_type
>
451 Output_merge_string
<Char_type
>::do_add_input_section(Relobj
* object
,
454 section_size_type sec_len
;
456 const unsigned char* pdata
= object
->decompressed_section_contents(shndx
,
460 const Char_type
* p
= reinterpret_cast<const Char_type
*>(pdata
);
461 const Char_type
* pend
= p
+ sec_len
/ sizeof(Char_type
);
462 const Char_type
* pend0
= pend
;
464 if (sec_len
% sizeof(Char_type
) != 0)
466 object
->error(_("mergeable string section length not multiple of "
475 gold_warning(_("%s: last entry in mergeable string section '%s' "
476 "not null terminated"),
477 object
->name().c_str(),
478 object
->section_name(shndx
).c_str());
479 // Find the end of the last NULL-terminated string in the buffer.
480 while (pend0
> p
&& pend0
[-1] != 0)
484 Merged_strings_list
* merged_strings_list
=
485 new Merged_strings_list(object
, shndx
);
486 this->merged_strings_lists_
.push_back(merged_strings_list
);
487 Merged_strings
& merged_strings
= merged_strings_list
->merged_strings
;
489 // Count the number of non-null strings in the section and size the list.
491 const Char_type
* pt
= p
;
494 size_t len
= string_length(pt
);
501 merged_strings
.reserve(count
+ 1);
503 // The index I is in bytes, not characters.
504 section_size_type i
= 0;
506 // We assume here that the beginning of the section is correctly
507 // aligned, so each string within the section must retain the same
509 uintptr_t init_align_modulo
= (reinterpret_cast<uintptr_t>(pdata
)
510 & (this->addralign() - 1));
511 bool has_misaligned_strings
= false;
515 size_t len
= p
< pend0
? string_length(p
) : pend
- p
;
517 // Within merge input section each string must be aligned.
519 && ((reinterpret_cast<uintptr_t>(p
) & (this->addralign() - 1))
520 != init_align_modulo
))
521 has_misaligned_strings
= true;
524 this->stringpool_
.add_with_length(p
, len
, true, &key
);
526 merged_strings
.push_back(Merged_string(i
, key
));
528 i
+= (len
+ 1) * sizeof(Char_type
);
531 // Record the last offset in the input section so that we can
532 // compute the length of the last string.
533 merged_strings
.push_back(Merged_string(i
, 0));
535 this->input_count_
+= count
;
536 this->input_size_
+= i
;
538 if (has_misaligned_strings
)
539 gold_warning(_("%s: section %s contains incorrectly aligned strings;"
540 " the alignment of those strings won't be preserved"),
541 object
->name().c_str(),
542 object
->section_name(shndx
).c_str());
544 // For script processing, we keep the input sections.
545 if (this->keeps_input_sections())
546 record_input_section(object
, shndx
);
554 // Finalize the mappings from the input sections to the output
555 // section, and return the final data size.
557 template<typename Char_type
>
559 Output_merge_string
<Char_type
>::finalize_merged_data()
561 this->stringpool_
.set_string_offsets();
563 for (typename
Merged_strings_lists::const_iterator l
=
564 this->merged_strings_lists_
.begin();
565 l
!= this->merged_strings_lists_
.end();
568 section_offset_type last_input_offset
= 0;
569 section_offset_type last_output_offset
= 0;
570 Relobj
*object
= (*l
)->object
;
571 Object_merge_map
* merge_map
= object
->get_or_create_merge_map();
572 Object_merge_map::Input_merge_map
* input_merge_map
=
573 merge_map
->get_or_make_input_merge_map(this, (*l
)->shndx
);
575 for (typename
Merged_strings::const_iterator p
=
576 (*l
)->merged_strings
.begin();
577 p
!= (*l
)->merged_strings
.end();
580 section_size_type length
= p
->offset
- last_input_offset
;
582 input_merge_map
->add_mapping(last_input_offset
, length
,
584 last_input_offset
= p
->offset
;
585 if (p
->stringpool_key
!= 0)
587 this->stringpool_
.get_offset_from_key(p
->stringpool_key
);
592 // Save some memory. This also ensures that this function will work
593 // if called twice, as may happen if Layout::set_segment_offsets
594 // finds a better alignment.
595 this->merged_strings_lists_
.clear();
597 return this->stringpool_
.get_strtab_size();
600 template<typename Char_type
>
602 Output_merge_string
<Char_type
>::set_final_data_size()
604 const off_t final_data_size
= this->finalize_merged_data();
605 this->set_data_size(final_data_size
);
608 // Write out a merged string section.
610 template<typename Char_type
>
612 Output_merge_string
<Char_type
>::do_write(Output_file
* of
)
614 this->stringpool_
.write(of
, this->offset());
617 // Write a merged string section to a buffer.
619 template<typename Char_type
>
621 Output_merge_string
<Char_type
>::do_write_to_buffer(unsigned char* buffer
)
623 this->stringpool_
.write_to_buffer(buffer
, this->data_size());
626 // Return the name of the types of string to use with
627 // do_print_merge_stats.
629 template<typename Char_type
>
631 Output_merge_string
<Char_type
>::string_name()
639 Output_merge_string
<char>::string_name()
646 Output_merge_string
<uint16_t>::string_name()
648 return "16-bit strings";
653 Output_merge_string
<uint32_t>::string_name()
655 return "32-bit strings";
658 // Print merge stats to stderr.
660 template<typename Char_type
>
662 Output_merge_string
<Char_type
>::do_print_merge_stats(const char* section_name
)
665 snprintf(buf
, sizeof buf
, "%s merged %s", section_name
, this->string_name());
666 fprintf(stderr
, _("%s: %s input bytes: %zu\n"),
667 program_name
, buf
, this->input_size_
);
668 fprintf(stderr
, _("%s: %s input strings: %zu\n"),
669 program_name
, buf
, this->input_count_
);
670 this->stringpool_
.print_stats(buf
);
673 // Instantiate the templates we need.
676 class Output_merge_string
<char>;
679 class Output_merge_string
<uint16_t>;
682 class Output_merge_string
<uint32_t>;
684 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
687 Object_merge_map::initialize_input_to_output_map
<32>(
689 elfcpp::Elf_types
<32>::Elf_Addr starting_address
,
690 Unordered_map
<section_offset_type
, elfcpp::Elf_types
<32>::Elf_Addr
>*);
693 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
696 Object_merge_map::initialize_input_to_output_map
<64>(
698 elfcpp::Elf_types
<64>::Elf_Addr starting_address
,
699 Unordered_map
<section_offset_type
, elfcpp::Elf_types
<64>::Elf_Addr
>*);
702 } // End namespace gold.