1 // layout.h -- lay out output file sections for gold -*- C++ -*-
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.
31 #include "workqueue.h"
34 #include "stringpool.h"
39 class General_options
;
42 class Output_section_data
;
44 class Output_section_headers
;
47 class Output_data_dynamic
;
50 // This task function handles mapping the input sections to output
51 // sections and laying them out in memory.
53 class Layout_task_runner
: public Task_function_runner
56 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
57 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
59 Layout_task_runner(const General_options
& options
,
60 const Input_objects
* input_objects
,
63 : options_(options
), input_objects_(input_objects
), symtab_(symtab
),
72 Layout_task_runner(const Layout_task_runner
&);
73 Layout_task_runner
& operator=(const Layout_task_runner
&);
75 const General_options
& options_
;
76 const Input_objects
* input_objects_
;
77 Symbol_table
* symtab_
;
81 // This class handles the details of laying out input sections.
86 Layout(const General_options
& options
);
88 // Given an input section SHNDX, named NAME, with data in SHDR, from
89 // the object file OBJECT, return the output section where this
90 // input section should go. Set *OFFSET to the offset within the
92 template<int size
, bool big_endian
>
94 layout(Relobj
*object
, unsigned int shndx
, const char* name
,
95 const elfcpp::Shdr
<size
, big_endian
>& shdr
, off_t
* offset
);
97 // Add an Output_section_data to the layout. This is used for
98 // special sections like the GOT section.
100 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
101 elfcpp::Elf_Xword flags
,
102 Output_section_data
*);
104 // Create dynamic sections if necessary.
106 create_initial_dynamic_sections(const Input_objects
*, Symbol_table
*);
108 // Define __start and __stop symbols for output sections.
110 define_section_symbols(Symbol_table
*, const Target
*);
112 // Return the Stringpool used for symbol names.
115 { return &this->sympool_
; }
117 // Return the Stringpool used for dynamic symbol names and dynamic
121 { return &this->dynpool_
; }
123 // Return whether a section is a .gnu.linkonce section, given the
126 is_linkonce(const char* name
)
127 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
129 // Record the signature of a comdat section, and return whether to
130 // include it in the link. The GROUP parameter is true for a
131 // section group signature, false for a signature derived from a
132 // .gnu.linkonce section.
134 add_comdat(const char*, bool group
);
136 // Finalize the layout after all the input sections have been added.
138 finalize(const Input_objects
*, Symbol_table
*);
140 // Return the TLS segment. This will return NULL if there isn't
144 { return this->tls_segment_
; }
146 // Return the normal symbol table.
148 symtab_section() const
150 gold_assert(this->symtab_section_
!= NULL
);
151 return this->symtab_section_
;
154 // Return the dynamic symbol table.
156 dynsym_section() const
158 gold_assert(this->dynsym_section_
!= NULL
);
159 return this->dynsym_section_
;
162 // Return the dynamic tags.
165 { return this->dynamic_data_
; }
167 // Write out data not associated with an input file or the symbol
170 write_data(const Symbol_table
*, const Target
*, Output_file
*) const;
172 // Return an output section named NAME, or NULL if there is none.
174 find_output_section(const char* name
) const;
176 // Return an output segment of type TYPE, with segment flags SET set
177 // and segment flags CLEAR clear. Return NULL if there is none.
179 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
180 elfcpp::Elf_Word clear
) const;
182 // The list of segments.
184 typedef std::vector
<Output_segment
*> Segment_list
;
186 // The list of sections not attached to a segment.
188 typedef std::vector
<Output_section
*> Section_list
;
190 // The list of information to write out which is not attached to
191 // either a section or a segment.
192 typedef std::vector
<Output_data
*> Data_list
;
195 Layout(const Layout
&);
196 Layout
& operator=(const Layout
&);
198 // Mapping from .gnu.linkonce section names to output section names.
199 struct Linkonce_mapping
206 static const Linkonce_mapping linkonce_mapping
[];
207 static const int linkonce_mapping_count
;
209 // Find the first read-only PT_LOAD segment, creating one if
212 find_first_load_seg();
214 // Create the output sections for the symbol table.
216 create_symtab_sections(int size
, const Input_objects
*, Symbol_table
*,
219 // Create the .shstrtab section.
223 // Create the section header table.
224 Output_section_headers
*
225 create_shdrs(int size
, bool big_endian
, off_t
*);
227 // Create the dynamic symbol table.
229 create_dynamic_symtab(const Target
*, Symbol_table
*, Output_section
** pdynstr
,
230 unsigned int* plocal_dynamic_count
,
231 std::vector
<Symbol
*>* pdynamic_symbols
,
234 // Finish the .dynamic section and PT_DYNAMIC segment.
236 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
238 // Create the .interp section and PT_INTERP segment.
240 create_interp(const Target
* target
);
242 // Create the version sections.
244 create_version_sections(const Target
*, const Versions
*,
245 unsigned int local_symcount
,
246 const std::vector
<Symbol
*>& dynamic_symbols
,
247 const Output_section
* dynstr
);
249 template<int size
, bool big_endian
>
251 sized_create_version_sections(const Versions
* versions
,
252 unsigned int local_symcount
,
253 const std::vector
<Symbol
*>& dynamic_symbols
,
254 const Output_section
* dynstr
257 // Return whether to include this section in the link.
258 template<int size
, bool big_endian
>
260 include_section(Object
* object
, const char* name
,
261 const elfcpp::Shdr
<size
, big_endian
>&);
263 // Return the output section name to use given an input section
264 // name. Set *PLEN to the length of the name. *PLEN must be
265 // initialized to the length of NAME.
267 output_section_name(const char* name
, size_t* plen
);
269 // Return the output section name to use for a linkonce section
270 // name. PLEN is as for output_section_name.
272 linkonce_output_name(const char* name
, size_t* plen
);
274 // Return the output section for NAME, TYPE and FLAGS.
276 get_output_section(const char* name
, Stringpool::Key name_key
,
277 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
);
279 // Create a new Output_section.
281 make_output_section(const char* name
, elfcpp::Elf_Word type
,
282 elfcpp::Elf_Xword flags
);
284 // Set the final file offsets of all the segments.
286 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
288 // Set the final file offsets and section indexes of all the
289 // sections not associated with a segment.
291 set_section_offsets(off_t
, unsigned int *pshndx
);
293 // Return whether SEG1 comes before SEG2 in the output file.
295 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
297 // Map from section flags to segment flags.
298 static elfcpp::Elf_Word
299 section_flags_to_segment(elfcpp::Elf_Xword flags
);
301 // A mapping used for group signatures.
302 typedef Unordered_map
<std::string
, bool> Signatures
;
304 // Mapping from input section name/type/flags to output section. We
305 // use canonicalized strings here.
307 typedef std::pair
<Stringpool::Key
,
308 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
313 operator()(const Key
& k
) const;
316 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
318 // A comparison class for segments.
320 struct Compare_segments
323 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
324 { return Layout::segment_precedes(seg1
, seg2
); }
327 // A reference to the options on the command line.
328 const General_options
& options_
;
329 // The output section names.
330 Stringpool namepool_
;
331 // The output symbol names.
333 // The dynamic strings, if needed.
335 // The list of group sections and linkonce sections which we have seen.
336 Signatures signatures_
;
337 // The mapping from input section name/type/flags to output sections.
338 Section_name_map section_name_map_
;
339 // The list of output segments.
340 Segment_list segment_list_
;
341 // The list of output sections.
342 Section_list section_list_
;
343 // The list of output sections which are not attached to any output
345 Section_list unattached_section_list_
;
346 // The list of unattached Output_data objects which require special
347 // handling because they are not Output_sections.
348 Data_list special_output_list_
;
349 // A pointer to the PT_TLS segment if there is one.
350 Output_segment
* tls_segment_
;
351 // The SHT_SYMTAB output section.
352 Output_section
* symtab_section_
;
353 // The SHT_DYNSYM output section if there is one.
354 Output_section
* dynsym_section_
;
355 // The SHT_DYNAMIC output section if there is one.
356 Output_section
* dynamic_section_
;
357 // The dynamic data which goes into dynamic_section_.
358 Output_data_dynamic
* dynamic_data_
;
361 // This task handles writing out data which is not part of a section
364 class Write_data_task
: public Task
367 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
368 const Target
* target
, Output_file
* of
,
369 Task_token
* final_blocker
)
370 : layout_(layout
), symtab_(symtab
), target_(target
), of_(of
),
371 final_blocker_(final_blocker
)
374 // The standard Task methods.
377 is_runnable(Workqueue
*);
386 const Layout
* layout_
;
387 const Symbol_table
* symtab_
;
388 const Target
* target_
;
390 Task_token
* final_blocker_
;
393 // This task handles writing out the global symbols.
395 class Write_symbols_task
: public Task
398 Write_symbols_task(const Symbol_table
* symtab
, const Target
* target
,
399 const Stringpool
* sympool
, const Stringpool
* dynpool
,
400 Output_file
* of
, Task_token
* final_blocker
)
401 : symtab_(symtab
), target_(target
), sympool_(sympool
), dynpool_(dynpool
),
402 of_(of
), final_blocker_(final_blocker
)
405 // The standard Task methods.
408 is_runnable(Workqueue
*);
417 const Symbol_table
* symtab_
;
418 const Target
* target_
;
419 const Stringpool
* sympool_
;
420 const Stringpool
* dynpool_
;
422 Task_token
* final_blocker_
;
425 // This task function handles closing the file.
427 class Close_task_runner
: public Task_function_runner
430 Close_task_runner(Output_file
* of
)
434 // Run the operation.
442 // A small helper function to align an address.
445 align_address(uint64_t address
, uint64_t addralign
)
448 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
452 } // End namespace gold.
454 #endif // !defined(GOLD_LAYOUT_H)