1 // layout.h -- lay out output file sections for gold -*- C++ -*-
11 #include "workqueue.h"
14 #include "stringpool.h"
19 class General_options;
22 class Output_section_data;
24 class Output_section_headers;
27 class Output_data_dynamic;
30 // This task function handles mapping the input sections to output
31 // sections and laying them out in memory.
33 class Layout_task_runner : public Task_function_runner
36 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
37 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
39 Layout_task_runner(const General_options& options,
40 const Input_objects* input_objects,
43 : options_(options), input_objects_(input_objects), symtab_(symtab),
52 Layout_task_runner(const Layout_task_runner&);
53 Layout_task_runner& operator=(const Layout_task_runner&);
55 const General_options& options_;
56 const Input_objects* input_objects_;
57 Symbol_table* symtab_;
61 // This class handles the details of laying out input sections.
66 Layout(const General_options& options);
68 // Given an input section SHNDX, named NAME, with data in SHDR, from
69 // the object file OBJECT, return the output section where this
70 // input section should go. Set *OFFSET to the offset within the
72 template<int size, bool big_endian>
74 layout(Relobj *object, unsigned int shndx, const char* name,
75 const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
77 // Add an Output_section_data to the layout. This is used for
78 // special sections like the GOT section.
80 add_output_section_data(const char* name, elfcpp::Elf_Word type,
81 elfcpp::Elf_Xword flags,
82 Output_section_data*);
84 // Create dynamic sections if necessary.
86 create_initial_dynamic_sections(const Input_objects*, Symbol_table*);
88 // Define __start and __stop symbols for output sections.
90 define_section_symbols(Symbol_table*, const Target*);
92 // Return the Stringpool used for symbol names.
95 { return &this->sympool_; }
97 // Return the Stringpool used for dynamic symbol names and dynamic
101 { return &this->dynpool_; }
103 // Return whether a section is a .gnu.linkonce section, given the
106 is_linkonce(const char* name)
107 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
109 // Record the signature of a comdat section, and return whether to
110 // include it in the link. The GROUP parameter is true for a
111 // section group signature, false for a signature derived from a
112 // .gnu.linkonce section.
114 add_comdat(const char*, bool group);
116 // Finalize the layout after all the input sections have been added.
118 finalize(const Input_objects*, Symbol_table*);
120 // Return the TLS segment. This will return NULL if there isn't
124 { return this->tls_segment_; }
126 // Return the normal symbol table.
128 symtab_section() const
130 gold_assert(this->symtab_section_ != NULL);
131 return this->symtab_section_;
134 // Return the dynamic symbol table.
136 dynsym_section() const
138 gold_assert(this->dynsym_section_ != NULL);
139 return this->dynsym_section_;
142 // Return the dynamic tags.
145 { return this->dynamic_data_; }
147 // Write out data not associated with an input file or the symbol
150 write_data(const Symbol_table*, const Target*, Output_file*) const;
152 // Return an output section named NAME, or NULL if there is none.
154 find_output_section(const char* name) const;
156 // Return an output segment of type TYPE, with segment flags SET set
157 // and segment flags CLEAR clear. Return NULL if there is none.
159 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
160 elfcpp::Elf_Word clear) const;
162 // The list of segments.
164 typedef std::vector<Output_segment*> Segment_list;
166 // The list of sections not attached to a segment.
168 typedef std::vector<Output_section*> Section_list;
170 // The list of information to write out which is not attached to
171 // either a section or a segment.
172 typedef std::vector<Output_data*> Data_list;
175 Layout(const Layout&);
176 Layout& operator=(const Layout&);
178 // Mapping from .gnu.linkonce section names to output section names.
179 struct Linkonce_mapping
186 static const Linkonce_mapping linkonce_mapping[];
187 static const int linkonce_mapping_count;
189 // Find the first read-only PT_LOAD segment, creating one if
192 find_first_load_seg();
194 // Create the output sections for the symbol table.
196 create_symtab_sections(int size, const Input_objects*, Symbol_table*,
199 // Create the .shstrtab section.
203 // Create the section header table.
204 Output_section_headers*
205 create_shdrs(int size, bool big_endian, off_t*);
207 // Create the dynamic symbol table.
209 create_dynamic_symtab(const Target*, Symbol_table*, Output_section** pdynstr,
210 unsigned int* plocal_dynamic_count,
211 std::vector<Symbol*>* pdynamic_symbols,
214 // Finish the .dynamic section and PT_DYNAMIC segment.
216 finish_dynamic_section(const Input_objects*, const Symbol_table*);
218 // Create the .interp section and PT_INTERP segment.
220 create_interp(const Target* target);
222 // Create the version sections.
224 create_version_sections(const Target*, const Versions*,
225 unsigned int local_symcount,
226 const std::vector<Symbol*>& dynamic_symbols,
227 const Output_section* dynstr);
229 template<int size, bool big_endian>
231 sized_create_version_sections(const Versions* versions,
232 unsigned int local_symcount,
233 const std::vector<Symbol*>& dynamic_symbols,
234 const Output_section* dynstr
237 // Return whether to include this section in the link.
238 template<int size, bool big_endian>
240 include_section(Object* object, const char* name,
241 const elfcpp::Shdr<size, big_endian>&);
243 // Return the output section name to use given an input section
244 // name. Set *PLEN to the length of the name. *PLEN must be
245 // initialized to the length of NAME.
247 output_section_name(const char* name, size_t* plen);
249 // Return the output section name to use for a linkonce section
250 // name. PLEN is as for output_section_name.
252 linkonce_output_name(const char* name, size_t* plen);
254 // Return the output section for NAME, TYPE and FLAGS.
256 get_output_section(const char* name, Stringpool::Key name_key,
257 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
259 // Create a new Output_section.
261 make_output_section(const char* name, elfcpp::Elf_Word type,
262 elfcpp::Elf_Xword flags);
264 // Set the final file offsets of all the segments.
266 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
268 // Set the final file offsets and section indexes of all the
269 // sections not associated with a segment.
271 set_section_offsets(off_t, unsigned int *pshndx);
273 // Return whether SEG1 comes before SEG2 in the output file.
275 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
277 // Map from section flags to segment flags.
278 static elfcpp::Elf_Word
279 section_flags_to_segment(elfcpp::Elf_Xword flags);
281 // A mapping used for group signatures.
282 typedef Unordered_map<std::string, bool> Signatures;
284 // Mapping from input section name/type/flags to output section. We
285 // use canonicalized strings here.
287 typedef std::pair<Stringpool::Key,
288 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
293 operator()(const Key& k) const;
296 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
298 // A comparison class for segments.
300 struct Compare_segments
303 operator()(const Output_segment* seg1, const Output_segment* seg2)
304 { return Layout::segment_precedes(seg1, seg2); }
307 // A reference to the options on the command line.
308 const General_options& options_;
309 // The output section names.
310 Stringpool namepool_;
311 // The output symbol names.
313 // The dynamic strings, if needed.
315 // The list of group sections and linkonce sections which we have seen.
316 Signatures signatures_;
317 // The mapping from input section name/type/flags to output sections.
318 Section_name_map section_name_map_;
319 // The list of output segments.
320 Segment_list segment_list_;
321 // The list of output sections.
322 Section_list section_list_;
323 // The list of output sections which are not attached to any output
325 Section_list unattached_section_list_;
326 // The list of unattached Output_data objects which require special
327 // handling because they are not Output_sections.
328 Data_list special_output_list_;
329 // A pointer to the PT_TLS segment if there is one.
330 Output_segment* tls_segment_;
331 // The SHT_SYMTAB output section.
332 Output_section* symtab_section_;
333 // The SHT_DYNSYM output section if there is one.
334 Output_section* dynsym_section_;
335 // The SHT_DYNAMIC output section if there is one.
336 Output_section* dynamic_section_;
337 // The dynamic data which goes into dynamic_section_.
338 Output_data_dynamic* dynamic_data_;
341 // This task handles writing out data which is not part of a section
344 class Write_data_task : public Task
347 Write_data_task(const Layout* layout, const Symbol_table* symtab,
348 const Target* target, Output_file* of,
349 Task_token* final_blocker)
350 : layout_(layout), symtab_(symtab), target_(target), of_(of),
351 final_blocker_(final_blocker)
354 // The standard Task methods.
357 is_runnable(Workqueue*);
366 const Layout* layout_;
367 const Symbol_table* symtab_;
368 const Target* target_;
370 Task_token* final_blocker_;
373 // This task handles writing out the global symbols.
375 class Write_symbols_task : public Task
378 Write_symbols_task(const Symbol_table* symtab, const Target* target,
379 const Stringpool* sympool, const Stringpool* dynpool,
380 Output_file* of, Task_token* final_blocker)
381 : symtab_(symtab), target_(target), sympool_(sympool), dynpool_(dynpool),
382 of_(of), final_blocker_(final_blocker)
385 // The standard Task methods.
388 is_runnable(Workqueue*);
397 const Symbol_table* symtab_;
398 const Target* target_;
399 const Stringpool* sympool_;
400 const Stringpool* dynpool_;
402 Task_token* final_blocker_;
405 // This task function handles closing the file.
407 class Close_task_runner : public Task_function_runner
410 Close_task_runner(Output_file* of)
414 // Run the operation.
422 // A small helper function to align an address.
425 align_address(uint64_t address, uint64_t addralign)
428 address = (address + addralign - 1) &~ (addralign - 1);
432 } // End namespace gold.
434 #endif // !defined(GOLD_LAYOUT_H)