1 // reloc.h -- relocate input files 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.
28 #include "workqueue.h"
33 class General_options;
35 class Read_relocs_data;
42 template<int size, bool big_endian>
48 template<int sh_type, bool dynamic, int size, bool big_endian>
49 class Output_data_reloc;
51 // A class to read the relocations for an object file, and then queue
52 // up a task to see if they require any GOT/PLT/COPY relocations in
55 class Read_relocs : public Task
58 // SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be
59 // unblocked when the Scan_relocs task completes.
60 Read_relocs(const General_options& options, Symbol_table* symtab,
61 Layout* layout, Relobj* object, Task_token* symtab_lock,
63 : options_(options), symtab_(symtab), layout_(layout), object_(object),
64 symtab_lock_(symtab_lock), blocker_(blocker)
67 // The standard Task methods.
70 is_runnable(Workqueue*);
79 const General_options& options_;
80 Symbol_table* symtab_;
83 Task_token* symtab_lock_;
87 // Scan the relocations for an object to see if they require any
88 // GOT/PLT/COPY relocations.
90 class Scan_relocs : public Task
93 // SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be
94 // unblocked when the task completes.
95 Scan_relocs(const General_options& options, Symbol_table* symtab,
96 Layout* layout, Relobj* object, Read_relocs_data* rd,
97 Task_token* symtab_lock, Task_token* blocker)
98 : options_(options), symtab_(symtab), layout_(layout), object_(object),
99 rd_(rd), symtab_lock_(symtab_lock), blocker_(blocker)
102 // The standard Task methods.
105 is_runnable(Workqueue*);
114 class Scan_relocs_locker;
116 const General_options& options_;
117 Symbol_table* symtab_;
120 Read_relocs_data* rd_;
121 Task_token* symtab_lock_;
122 Task_token* blocker_;
125 // A class to perform all the relocations for an object file.
127 class Relocate_task : public Task
130 Relocate_task(const General_options& options, const Symbol_table* symtab,
131 const Layout* layout, Relobj* object, Output_file* of,
132 Task_token* final_blocker)
133 : options_(options), symtab_(symtab), layout_(layout), object_(object),
134 of_(of), final_blocker_(final_blocker)
137 // The standard Task methods.
140 is_runnable(Workqueue*);
149 class Relocate_locker;
151 const General_options& options_;
152 const Symbol_table* symtab_;
153 const Layout* layout_;
156 Task_token* final_blocker_;
159 // Standard relocation routines which are used on many targets. Here
160 // SIZE and BIG_ENDIAN refer to the target, not the relocation type.
162 template<int size, bool big_endian>
163 class Relocate_functions
166 // Do a simple relocation with the addend in the section contents.
167 // VALSIZE is the size of the value.
168 template<int valsize>
170 rel(unsigned char* view,
171 typename elfcpp::Swap<valsize, big_endian>::Valtype value)
173 typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
174 Valtype* wv = reinterpret_cast<Valtype*>(view);
175 Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
176 elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value);
179 // Do a simple relocation using a Symbol_value with the addend in
180 // the section contents. VALSIZE is the size of the value to
182 template<int valsize>
184 rel(unsigned char* view,
185 const Sized_relobj<size, big_endian>* object,
186 const Symbol_value<size>* psymval)
188 typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
189 Valtype* wv = reinterpret_cast<Valtype*>(view);
190 Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
191 x = psymval->value(object, x);
192 elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
195 // Like rel(), but sign-extends the value to SIZE.
196 template<int valsize>
198 signedrel(unsigned char* view,
199 const Sized_relobj<size, big_endian>* object,
200 const Symbol_value<size>* psymval)
202 typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
203 typedef typename elfcpp::Swap<size, big_endian>::Valtype Sizetype;
204 Valtype* wv = reinterpret_cast<Valtype*>(view);
205 Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
206 // Fancy formula to sign-extend x to size.
207 const Sizetype mask = 1U << (sizeof(valsize) * 8 - 1);
208 Sizetype sign_extended_x = x;
209 sign_extended_x = (sign_extended_x ^ mask) - mask;
210 x = psymval->value(object, sign_extended_x);
211 elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
214 // Do a simple PC relative relocation with the addend in the section
215 // contents. VALSIZE is the size of the value.
216 template<int valsize>
218 pcrel(unsigned char* view,
219 typename elfcpp::Swap<valsize, big_endian>::Valtype value,
220 typename elfcpp::Elf_types<size>::Elf_Addr address)
222 typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
223 Valtype* wv = reinterpret_cast<Valtype*>(view);
224 Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
225 elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address);
228 // Do a simple PC relative relocation with a Symbol_value with the
229 // addend in the section contents. VALSIZE is the size of the
231 template<int valsize>
233 pcrel(unsigned char* view,
234 const Sized_relobj<size, big_endian>* object,
235 const Symbol_value<size>* psymval,
236 typename elfcpp::Elf_types<size>::Elf_Addr address)
238 typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
239 Valtype* wv = reinterpret_cast<Valtype*>(view);
240 Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
241 x = psymval->value(object, x);
242 elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
245 typedef Relocate_functions<size, big_endian> This;
248 // Do a simple 8-bit REL relocation with the addend in the section
251 rel8(unsigned char* view, unsigned char value)
252 { This::template rel<8>(view, value); }
255 rel8(unsigned char* view,
256 const Sized_relobj<size, big_endian>* object,
257 const Symbol_value<size>* psymval)
258 { This::template rel<8>(view, object, psymval); }
260 // Do an 8-bit REL relocation, sign extending the addend to SIZE.
262 rel8s(unsigned char* view,
263 const Sized_relobj<size, big_endian>* object,
264 const Symbol_value<size>* psymval)
265 { This::template signedrel<8>(view, object, psymval); }
267 // Do a simple 8-bit PC relative relocation with the addend in the
270 pcrel8(unsigned char* view, unsigned char value,
271 typename elfcpp::Elf_types<size>::Elf_Addr address)
272 { This::template pcrel<8>(view, value, address); }
275 pcrel8(unsigned char* view,
276 const Sized_relobj<size, big_endian>* object,
277 const Symbol_value<size>* psymval,
278 typename elfcpp::Elf_types<size>::Elf_Addr address)
279 { This::template pcrel<8>(view, object, psymval, address); }
281 // Do a simple 16-bit REL relocation with the addend in the section
284 rel16(unsigned char* view, elfcpp::Elf_Half value)
285 { This::template rel<16>(view, value); }
288 rel16(unsigned char* view,
289 const Sized_relobj<size, big_endian>* object,
290 const Symbol_value<size>* psymval)
291 { This::template rel<16>(view, object, psymval); }
293 // Do a 16-bit REL relocation, sign extending the addend to SIZE.
295 rel16s(unsigned char* view,
296 const Sized_relobj<size, big_endian>* object,
297 const Symbol_value<size>* psymval)
298 { This::template signedrel<16>(view, object, psymval); }
300 // Do a simple 32-bit PC relative REL relocation with the addend in
301 // the section contents.
303 pcrel16(unsigned char* view, elfcpp::Elf_Word value,
304 typename elfcpp::Elf_types<size>::Elf_Addr address)
305 { This::template pcrel<16>(view, value, address); }
308 pcrel16(unsigned char* view,
309 const Sized_relobj<size, big_endian>* object,
310 const Symbol_value<size>* psymval,
311 typename elfcpp::Elf_types<size>::Elf_Addr address)
312 { This::template pcrel<16>(view, object, psymval, address); }
314 // Do a simple 32-bit REL relocation with the addend in the section
317 rel32(unsigned char* view, elfcpp::Elf_Word value)
318 { This::template rel<32>(view, value); }
321 rel32(unsigned char* view,
322 const Sized_relobj<size, big_endian>* object,
323 const Symbol_value<size>* psymval)
324 { This::template rel<32>(view, object, psymval); }
326 // Do a 32-bit REL relocation, sign extending the addend to SIZE.
328 rel32s(unsigned char* view,
329 const Sized_relobj<size, big_endian>* object,
330 const Symbol_value<size>* psymval)
331 { This::template signedrel<32>(view, object, psymval); }
333 // Do a simple 32-bit PC relative REL relocation with the addend in
334 // the section contents.
336 pcrel32(unsigned char* view, elfcpp::Elf_Word value,
337 typename elfcpp::Elf_types<size>::Elf_Addr address)
338 { This::template pcrel<32>(view, value, address); }
341 pcrel32(unsigned char* view,
342 const Sized_relobj<size, big_endian>* object,
343 const Symbol_value<size>* psymval,
344 typename elfcpp::Elf_types<size>::Elf_Addr address)
345 { This::template pcrel<32>(view, object, psymval, address); }
347 // Do a simple 64-bit REL relocation with the addend in the section
350 rel64(unsigned char* view, elfcpp::Elf_Xword value)
351 { This::template rel<64>(view, value); }
354 rel64(unsigned char* view,
355 const Sized_relobj<size, big_endian>* object,
356 const Symbol_value<size>* psymval)
357 { This::template rel<64>(view, object, psymval); }
359 // Do a simple 64-bit PC relative REL relocation with the addend in
360 // the section contents.
362 pcrel64(unsigned char* view, elfcpp::Elf_Xword value,
363 typename elfcpp::Elf_types<size>::Elf_Addr address)
364 { This::template pcrel<64>(view, value, address); }
367 pcrel64(unsigned char* view,
368 const Sized_relobj<size, big_endian>* object,
369 const Symbol_value<size>* psymval,
370 typename elfcpp::Elf_types<size>::Elf_Addr address)
371 { This::template pcrel<64>(view, object, psymval, address); }
374 // We try to avoid COPY relocations when possible. A COPY relocation
375 // may be required when an executable refers to a variable defined in
376 // a shared library. COPY relocations are problematic because they
377 // tie the executable to the exact size of the variable in the shared
378 // library. We can avoid them if all the references to the variable
379 // are in a writeable section. In that case we can simply use dynamic
380 // relocations. However, when scanning relocs, we don't know when we
381 // see the relocation whether we will be forced to use a COPY
382 // relocation or not. So we have to save the relocation during the
383 // reloc scanning, and then emit it as a dynamic relocation if
384 // necessary. This class implements that. It is used by the target
387 template<int size, bool big_endian>
395 // Return whether we need a COPY reloc for a reloc against GSYM,
396 // which is being applied to section SHNDX in OBJECT.
398 need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx,
399 Sized_symbol<size>* gsym);
401 // Save a Rel against SYM for possible emission later. SHNDX is the
402 // index of the section to which the reloc is being applied.
404 save(Symbol* sym, Relobj*, unsigned int shndx,
405 const elfcpp::Rel<size, big_endian>&);
407 // Save a Rela against SYM for possible emission later.
409 save(Symbol* sym, Relobj*, unsigned int shndx,
410 const elfcpp::Rela<size, big_endian>&);
412 // Return whether there are any relocs to emit. This also discards
413 // entries which need not be emitted.
417 // Emit relocs for each symbol which did not get a COPY reloc (i.e.,
418 // is still defined in the dynamic object).
419 template<int sh_type>
421 emit(Output_data_reloc<sh_type, true, size, big_endian>*);
424 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
425 typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
427 // This POD class holds the entries we are saving.
428 class Copy_reloc_entry
431 Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
432 Relobj* relobj, unsigned int shndx,
433 Address address, Addend addend)
434 : sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
435 shndx_(shndx), address_(address), addend_(addend)
438 // Return whether we should emit this reloc. If we should not
439 // emit, we clear it.
446 emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*);
449 emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*);
453 unsigned int reloc_type_;
460 // A list of relocs to be saved.
461 typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
463 // The list of relocs we are saving.
464 Copy_reloc_entries entries_;
467 } // End namespace gold.
469 #endif // !defined(GOLD_RELOC_H)