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
);
107 // Try to merge the new entry in the last one we saw.
108 if (!map
->entries
.empty())
110 Input_merge_entry
& entry(map
->entries
.back());
112 // Use section_size_type to avoid signed/unsigned warnings.
113 section_size_type input_offset_u
= input_offset
;
114 section_size_type output_offset_u
= output_offset
;
116 // If this entry is not in order, we need to sort the vector
117 // before looking anything up.
118 if (input_offset_u
< entry
.input_offset
+ entry
.length
)
120 gold_assert(input_offset
< entry
.input_offset
);
121 gold_assert(input_offset_u
+ length
122 <= static_cast<section_size_type
>(entry
.input_offset
));
125 else if (entry
.input_offset
+ entry
.length
== input_offset_u
126 && (output_offset
== -1
127 ? entry
.output_offset
== -1
128 : entry
.output_offset
+ entry
.length
== output_offset_u
))
130 entry
.length
+= length
;
135 Input_merge_entry entry
;
136 entry
.input_offset
= input_offset
;
137 entry
.length
= length
;
138 entry
.output_offset
= output_offset
;
139 map
->entries
.push_back(entry
);
142 // Get the output offset for an input address.
145 Object_merge_map::get_output_offset(unsigned int shndx
,
146 section_offset_type input_offset
,
147 section_offset_type
* output_offset
)
149 Input_merge_map
* map
= this->get_input_merge_map(shndx
);
155 std::sort(map
->entries
.begin(), map
->entries
.end(),
156 Input_merge_compare());
160 Input_merge_entry entry
;
161 entry
.input_offset
= input_offset
;
162 std::vector
<Input_merge_entry
>::const_iterator p
=
163 std::upper_bound(map
->entries
.begin(), map
->entries
.end(),
164 entry
, Input_merge_compare());
165 if (p
== map
->entries
.begin())
168 gold_assert(p
->input_offset
<= input_offset
);
170 if (input_offset
- p
->input_offset
171 >= static_cast<section_offset_type
>(p
->length
))
174 *output_offset
= p
->output_offset
;
175 if (*output_offset
!= -1)
176 *output_offset
+= (input_offset
- p
->input_offset
);
180 // Return whether this is the merge map for section SHNDX.
182 const Output_section_data
*
183 Object_merge_map::find_merge_section(unsigned int shndx
) const {
184 const Object_merge_map::Input_merge_map
* map
=
185 this->get_input_merge_map(shndx
);
188 return map
->output_data
;
191 // Initialize a mapping from input offsets to output addresses.
195 Object_merge_map::initialize_input_to_output_map(
197 typename
elfcpp::Elf_types
<size
>::Elf_Addr starting_address
,
198 Unordered_map
<section_offset_type
,
199 typename
elfcpp::Elf_types
<size
>::Elf_Addr
>* initialize_map
)
201 Input_merge_map
* map
= this->get_input_merge_map(shndx
);
202 gold_assert(map
!= NULL
);
204 gold_assert(initialize_map
->empty());
205 // We know how many entries we are going to add.
206 // reserve_unordered_map takes an expected count of buckets, not a
207 // count of elements, so double it to try to reduce collisions.
208 reserve_unordered_map(initialize_map
, map
->entries
.size() * 2);
210 for (Input_merge_map::Entries::const_iterator p
= map
->entries
.begin();
211 p
!= map
->entries
.end();
214 section_offset_type output_offset
= p
->output_offset
;
215 if (output_offset
!= -1)
216 output_offset
+= starting_address
;
219 // If we see a relocation against an address we have chosen
220 // to discard, we relocate to zero. FIXME: We could also
221 // issue a warning in this case; that would require
222 // reporting this somehow and checking it in the routines in
226 initialize_map
->insert(std::make_pair(p
->input_offset
, output_offset
));
230 // Class Output_merge_base.
232 // Return the output offset for an input offset. The input address is
233 // at offset OFFSET in section SHNDX in OBJECT. If we know the
234 // offset, set *POUTPUT and return true. Otherwise return false.
237 Output_merge_base::do_output_offset(const Relobj
* object
,
239 section_offset_type offset
,
240 section_offset_type
* poutput
) const
242 return object
->merge_output_offset(shndx
, offset
, poutput
);
245 // Record a merged input section for script processing.
248 Output_merge_base::record_input_section(Relobj
* relobj
, unsigned int shndx
)
250 gold_assert(this->keeps_input_sections_
&& relobj
!= NULL
);
251 // If this is the first input section, record it. We need do this because
252 // this->input_sections_ is unordered.
253 if (this->first_relobj_
== NULL
)
255 this->first_relobj_
= relobj
;
256 this->first_shndx_
= shndx
;
259 std::pair
<Input_sections::iterator
, bool> result
=
260 this->input_sections_
.insert(Section_id(relobj
, shndx
));
261 // We should insert a merge section once only.
262 gold_assert(result
.second
);
265 // Class Output_merge_data.
267 // Compute the hash code for a fixed-size constant.
270 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k
) const
272 const unsigned char* p
= this->pomd_
->constant(k
);
273 section_size_type entsize
=
274 convert_to_section_size_type(this->pomd_
->entsize());
276 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
277 if (sizeof(size_t) == 8)
279 size_t result
= static_cast<size_t>(14695981039346656037ULL);
280 for (section_size_type i
= 0; i
< entsize
; ++i
)
282 result
&= (size_t) *p
++;
283 result
*= 1099511628211ULL;
289 size_t result
= 2166136261UL;
290 for (section_size_type i
= 0; i
< entsize
; ++i
)
292 result
^= (size_t) *p
++;
293 result
*= 16777619UL;
299 // Return whether one hash table key equals another.
302 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1
,
303 Merge_data_key k2
) const
305 const unsigned char* p1
= this->pomd_
->constant(k1
);
306 const unsigned char* p2
= this->pomd_
->constant(k2
);
307 return memcmp(p1
, p2
, this->pomd_
->entsize()) == 0;
310 // Add a constant to the end of the section contents.
313 Output_merge_data::add_constant(const unsigned char* p
)
315 section_size_type entsize
= convert_to_section_size_type(this->entsize());
316 section_size_type addralign
=
317 convert_to_section_size_type(this->addralign());
318 section_size_type addsize
= std::max(entsize
, addralign
);
319 if (this->len_
+ addsize
> this->alc_
)
322 this->alc_
= 128 * addsize
;
325 this->p_
= static_cast<unsigned char*>(realloc(this->p_
, this->alc_
));
326 if (this->p_
== NULL
)
330 memcpy(this->p_
+ this->len_
, p
, entsize
);
331 if (addsize
> entsize
)
332 memset(this->p_
+ this->len_
+ entsize
, 0, addsize
- entsize
);
333 this->len_
+= addsize
;
336 // Add the input section SHNDX in OBJECT to a merged output section
337 // which holds fixed length constants. Return whether we were able to
338 // handle the section; if not, it will be linked as usual without
342 Output_merge_data::do_add_input_section(Relobj
* object
, unsigned int shndx
)
344 section_size_type len
;
346 const unsigned char* p
= object
->decompressed_section_contents(shndx
, &len
,
349 section_size_type entsize
= convert_to_section_size_type(this->entsize());
351 if (len
% entsize
!= 0)
358 this->input_count_
+= len
/ entsize
;
360 for (section_size_type i
= 0; i
< len
; i
+= entsize
, p
+= entsize
)
362 // Add the constant to the section contents. If we find that it
363 // is already in the hash table, we will remove it again.
364 Merge_data_key k
= this->len_
;
365 this->add_constant(p
);
367 std::pair
<Merge_data_hashtable::iterator
, bool> ins
=
368 this->hashtable_
.insert(k
);
372 // Key was already present. Remove the copy we just added.
373 this->len_
-= entsize
;
377 // Record the offset of this constant in the output section.
378 object
->add_merge_mapping(this, shndx
, i
, entsize
, k
);
381 // For script processing, we keep the input sections.
382 if (this->keeps_input_sections())
383 record_input_section(object
, shndx
);
391 // Set the final data size in a merged output section with fixed size
395 Output_merge_data::set_final_data_size()
397 // Release the memory we don't need.
398 this->p_
= static_cast<unsigned char*>(realloc(this->p_
, this->len_
));
399 // An Output_merge_data object may be empty and realloc is allowed
400 // to return a NULL pointer in this case. An Output_merge_data is empty
401 // if all its input sections have sizes that are not multiples of entsize.
402 gold_assert(this->p_
!= NULL
|| this->len_
== 0);
403 this->set_data_size(this->len_
);
406 // Write the data of a merged output section with fixed size constants
410 Output_merge_data::do_write(Output_file
* of
)
412 of
->write(this->offset(), this->p_
, this->len_
);
415 // Write the data to a buffer.
418 Output_merge_data::do_write_to_buffer(unsigned char* buffer
)
420 memcpy(buffer
, this->p_
, this->len_
);
423 // Print merge stats to stderr.
426 Output_merge_data::do_print_merge_stats(const char* section_name
)
429 _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
430 program_name
, section_name
,
431 static_cast<unsigned long>(this->entsize()),
432 this->input_count_
, this->hashtable_
.size());
435 // Class Output_merge_string.
437 // Add an input section to a merged string section.
439 template<typename Char_type
>
441 Output_merge_string
<Char_type
>::do_add_input_section(Relobj
* object
,
444 section_size_type sec_len
;
446 const unsigned char* pdata
= object
->decompressed_section_contents(shndx
,
450 const Char_type
* p
= reinterpret_cast<const Char_type
*>(pdata
);
451 const Char_type
* pend
= p
+ sec_len
/ sizeof(Char_type
);
452 const Char_type
* pend0
= pend
;
454 if (sec_len
% sizeof(Char_type
) != 0)
456 object
->error(_("mergeable string section length not multiple of "
465 gold_warning(_("%s: last entry in mergeable string section '%s' "
466 "not null terminated"),
467 object
->name().c_str(),
468 object
->section_name(shndx
).c_str());
469 // Find the end of the last NULL-terminated string in the buffer.
470 while (pend0
> p
&& pend0
[-1] != 0)
474 Merged_strings_list
* merged_strings_list
=
475 new Merged_strings_list(object
, shndx
);
476 this->merged_strings_lists_
.push_back(merged_strings_list
);
477 Merged_strings
& merged_strings
= merged_strings_list
->merged_strings
;
479 // Count the number of non-null strings in the section and size the list.
481 const Char_type
* pt
= p
;
484 size_t len
= string_length(pt
);
491 merged_strings
.reserve(count
+ 1);
493 // The index I is in bytes, not characters.
494 section_size_type i
= 0;
496 // We assume here that the beginning of the section is correctly
497 // aligned, so each string within the section must retain the same
499 uintptr_t init_align_modulo
= (reinterpret_cast<uintptr_t>(pdata
)
500 & (this->addralign() - 1));
501 bool has_misaligned_strings
= false;
505 size_t len
= p
< pend0
? string_length(p
) : pend
- p
;
507 // Within merge input section each string must be aligned.
509 && ((reinterpret_cast<uintptr_t>(p
) & (this->addralign() - 1))
510 != init_align_modulo
))
511 has_misaligned_strings
= true;
514 this->stringpool_
.add_with_length(p
, len
, true, &key
);
516 merged_strings
.push_back(Merged_string(i
, key
));
518 i
+= (len
+ 1) * sizeof(Char_type
);
521 // Record the last offset in the input section so that we can
522 // compute the length of the last string.
523 merged_strings
.push_back(Merged_string(i
, 0));
525 this->input_count_
+= count
;
526 this->input_size_
+= i
;
528 if (has_misaligned_strings
)
529 gold_warning(_("%s: section %s contains incorrectly aligned strings;"
530 " the alignment of those strings won't be preserved"),
531 object
->name().c_str(),
532 object
->section_name(shndx
).c_str());
534 // For script processing, we keep the input sections.
535 if (this->keeps_input_sections())
536 record_input_section(object
, shndx
);
544 // Finalize the mappings from the input sections to the output
545 // section, and return the final data size.
547 template<typename Char_type
>
549 Output_merge_string
<Char_type
>::finalize_merged_data()
551 this->stringpool_
.set_string_offsets();
553 for (typename
Merged_strings_lists::const_iterator l
=
554 this->merged_strings_lists_
.begin();
555 l
!= this->merged_strings_lists_
.end();
558 section_offset_type last_input_offset
= 0;
559 section_offset_type last_output_offset
= 0;
560 for (typename
Merged_strings::const_iterator p
=
561 (*l
)->merged_strings
.begin();
562 p
!= (*l
)->merged_strings
.end();
565 section_size_type length
= p
->offset
- last_input_offset
;
567 (*l
)->object
->add_merge_mapping(this, (*l
)->shndx
,
568 last_input_offset
, length
, last_output_offset
);
569 last_input_offset
= p
->offset
;
570 if (p
->stringpool_key
!= 0)
572 this->stringpool_
.get_offset_from_key(p
->stringpool_key
);
577 // Save some memory. This also ensures that this function will work
578 // if called twice, as may happen if Layout::set_segment_offsets
579 // finds a better alignment.
580 this->merged_strings_lists_
.clear();
582 return this->stringpool_
.get_strtab_size();
585 template<typename Char_type
>
587 Output_merge_string
<Char_type
>::set_final_data_size()
589 const off_t final_data_size
= this->finalize_merged_data();
590 this->set_data_size(final_data_size
);
593 // Write out a merged string section.
595 template<typename Char_type
>
597 Output_merge_string
<Char_type
>::do_write(Output_file
* of
)
599 this->stringpool_
.write(of
, this->offset());
602 // Write a merged string section to a buffer.
604 template<typename Char_type
>
606 Output_merge_string
<Char_type
>::do_write_to_buffer(unsigned char* buffer
)
608 this->stringpool_
.write_to_buffer(buffer
, this->data_size());
611 // Return the name of the types of string to use with
612 // do_print_merge_stats.
614 template<typename Char_type
>
616 Output_merge_string
<Char_type
>::string_name()
624 Output_merge_string
<char>::string_name()
631 Output_merge_string
<uint16_t>::string_name()
633 return "16-bit strings";
638 Output_merge_string
<uint32_t>::string_name()
640 return "32-bit strings";
643 // Print merge stats to stderr.
645 template<typename Char_type
>
647 Output_merge_string
<Char_type
>::do_print_merge_stats(const char* section_name
)
650 snprintf(buf
, sizeof buf
, "%s merged %s", section_name
, this->string_name());
651 fprintf(stderr
, _("%s: %s input bytes: %zu\n"),
652 program_name
, buf
, this->input_size_
);
653 fprintf(stderr
, _("%s: %s input strings: %zu\n"),
654 program_name
, buf
, this->input_count_
);
655 this->stringpool_
.print_stats(buf
);
658 // Instantiate the templates we need.
661 class Output_merge_string
<char>;
664 class Output_merge_string
<uint16_t>;
667 class Output_merge_string
<uint32_t>;
669 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
672 Object_merge_map::initialize_input_to_output_map
<32>(
674 elfcpp::Elf_types
<32>::Elf_Addr starting_address
,
675 Unordered_map
<section_offset_type
, elfcpp::Elf_types
<32>::Elf_Addr
>*);
678 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
681 Object_merge_map::initialize_input_to_output_map
<64>(
683 elfcpp::Elf_types
<64>::Elf_Addr starting_address
,
684 Unordered_map
<section_offset_type
, elfcpp::Elf_types
<64>::Elf_Addr
>*);
687 } // End namespace gold.