1 // target.h -- target support for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008, 2009 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.
23 // The abstract class Target is the interface for target specific
24 // support. It defines abstract methods which each target must
25 // implement. Typically there will be one target per processor, but
26 // in some cases it may be necessary to have subclasses.
28 // For speed and consistency we want to use inline functions to handle
29 // relocation processing. So besides implementations of the abstract
30 // methods, each target is expected to define a template
31 // specialization of the relocation functions.
38 #include "parameters.h"
46 template<int size
, bool big_endian
>
48 class Relocatable_relocs
;
49 template<int size
, bool big_endian
>
51 class Reloc_symbol_changes
;
59 // The abstract class for target specific handling.
67 // Return the bit size that this target implements. This should
71 { return this->pti_
->size
; }
73 // Return whether this target is big-endian.
76 { return this->pti_
->is_big_endian
; }
78 // Machine code to store in e_machine field of ELF header.
81 { return this->pti_
->machine_code
; }
83 // Processor specific flags to store in e_flags field of ELF header.
85 processor_specific_flags() const
86 { return this->processor_specific_flags_
; }
88 // Whether processor specific flags are set at least once.
90 are_processor_specific_flags_set() const
91 { return this->are_processor_specific_flags_set_
; }
93 // Whether this target has a specific make_symbol function.
95 has_make_symbol() const
96 { return this->pti_
->has_make_symbol
; }
98 // Whether this target has a specific resolve function.
101 { return this->pti_
->has_resolve
; }
103 // Whether this target has a specific code fill function.
105 has_code_fill() const
106 { return this->pti_
->has_code_fill
; }
108 // Return the default name of the dynamic linker.
110 dynamic_linker() const
111 { return this->pti_
->dynamic_linker
; }
113 // Return the default address to use for the text segment.
115 default_text_segment_address() const
116 { return this->pti_
->default_text_segment_address
; }
118 // Return the ABI specified page size.
122 if (parameters
->options().max_page_size() > 0)
123 return parameters
->options().max_page_size();
125 return this->pti_
->abi_pagesize
;
128 // Return the common page size used on actual systems.
130 common_pagesize() const
132 if (parameters
->options().common_page_size() > 0)
133 return std::min(parameters
->options().common_page_size(),
134 this->abi_pagesize());
136 return std::min(this->pti_
->common_pagesize
,
137 this->abi_pagesize());
140 // If we see some object files with .note.GNU-stack sections, and
141 // some objects files without them, this returns whether we should
142 // consider the object files without them to imply that the stack
143 // should be executable.
145 is_default_stack_executable() const
146 { return this->pti_
->is_default_stack_executable
; }
148 // Return a character which may appear as a prefix for a wrap
149 // symbol. If this character appears, we strip it when checking for
150 // wrapping and add it back when forming the final symbol name.
151 // This should be '\0' if not special prefix is required, which is
155 { return this->pti_
->wrap_char
; }
157 // Return the special section index which indicates a small common
158 // symbol. This will return SHN_UNDEF if there are no small common
161 small_common_shndx() const
162 { return this->pti_
->small_common_shndx
; }
164 // Return values to add to the section flags for the section holding
165 // small common symbols.
167 small_common_section_flags() const
169 gold_assert(this->pti_
->small_common_shndx
!= elfcpp::SHN_UNDEF
);
170 return this->pti_
->small_common_section_flags
;
173 // Return the special section index which indicates a large common
174 // symbol. This will return SHN_UNDEF if there are no large common
177 large_common_shndx() const
178 { return this->pti_
->large_common_shndx
; }
180 // Return values to add to the section flags for the section holding
181 // large common symbols.
183 large_common_section_flags() const
185 gold_assert(this->pti_
->large_common_shndx
!= elfcpp::SHN_UNDEF
);
186 return this->pti_
->large_common_section_flags
;
189 // This hook is called when an output section is created.
191 new_output_section(Output_section
* os
) const
192 { this->do_new_output_section(os
); }
194 // This is called to tell the target to complete any sections it is
195 // handling. After this all sections must have their final size.
197 finalize_sections(Layout
* layout
, const Input_objects
* input_objects
,
198 Symbol_table
* symtab
)
199 { return this->do_finalize_sections(layout
, input_objects
, symtab
); }
201 // Return the value to use for a global symbol which needs a special
202 // value in the dynamic symbol table. This will only be called if
203 // the backend first calls symbol->set_needs_dynsym_value().
205 dynsym_value(const Symbol
* sym
) const
206 { return this->do_dynsym_value(sym
); }
208 // Return a string to use to fill out a code section. This is
209 // basically one or more NOPS which must fill out the specified
212 code_fill(section_size_type length
) const
213 { return this->do_code_fill(length
); }
215 // Return whether SYM is known to be defined by the ABI. This is
216 // used to avoid inappropriate warnings about undefined symbols.
218 is_defined_by_abi(const Symbol
* sym
) const
219 { return this->do_is_defined_by_abi(sym
); }
221 // Adjust the output file header before it is written out. VIEW
222 // points to the header in external form. LEN is the length.
224 adjust_elf_header(unsigned char* view
, int len
) const
225 { return this->do_adjust_elf_header(view
, len
); }
227 // Return whether NAME is a local label name. This is used to implement the
228 // --discard-locals options.
230 is_local_label_name(const char* name
) const
231 { return this->do_is_local_label_name(name
); }
233 // Get the symbol index to use for a target specific reloc.
235 reloc_symbol_index(void* arg
, unsigned int type
) const
236 { return this->do_reloc_symbol_index(arg
, type
); }
238 // Get the addend to use for a target specific reloc.
240 reloc_addend(void* arg
, unsigned int type
, uint64_t addend
) const
241 { return this->do_reloc_addend(arg
, type
, addend
); }
243 // A function starts at OFFSET in section SHNDX in OBJECT. That
244 // function was compiled with -fsplit-stack, but it refers to a
245 // function which was compiled without -fsplit-stack. VIEW is a
246 // modifiable view of the section; VIEW_SIZE is the size of the
247 // view. The target has to adjust the function so that it allocates
250 calls_non_split(Relobj
* object
, unsigned int shndx
,
251 section_offset_type fnoffset
, section_size_type fnsize
,
252 unsigned char* view
, section_size_type view_size
,
253 std::string
* from
, std::string
* to
) const
255 this->do_calls_non_split(object
, shndx
, fnoffset
, fnsize
, view
, view_size
,
259 // Make an ELF object.
260 template<int size
, bool big_endian
>
262 make_elf_object(const std::string
& name
, Input_file
* input_file
,
263 off_t offset
, const elfcpp::Ehdr
<size
, big_endian
>& ehdr
)
264 { return this->do_make_elf_object(name
, input_file
, offset
, ehdr
); }
266 // Make an output section.
268 make_output_section(const char* name
, elfcpp::Elf_Word type
,
269 elfcpp::Elf_Xword flags
)
270 { return this->do_make_output_section(name
, type
, flags
); }
272 // Return true if target wants to perform relaxation.
276 // Run the dummy relaxation pass twice if relaxation debugging is enabled.
277 if (is_debugging_enabled(DEBUG_RELAXATION
))
280 return this->do_may_relax();
283 // Perform a relaxation pass. Return true if layout may be changed.
285 relax(int pass
, const Input_objects
* input_objects
, Symbol_table
* symtab
,
288 // Run the dummy relaxation pass twice if relaxation debugging is enabled.
289 if (is_debugging_enabled(DEBUG_RELAXATION
))
292 return this->do_relax(pass
, input_objects
, symtab
, layout
);
295 // Return the target-specific name of attributes section. This is
296 // NULL if a target does not use attributes section or if it uses
297 // the default section name ".gnu.attributes".
299 attributes_section() const
300 { return this->pti_
->attributes_section
; }
302 // Return the vendor name of vendor attributes.
304 attributes_vendor() const
305 { return this->pti_
->attributes_vendor
; }
307 // Whether a section called NAME is an attribute section.
309 is_attributes_section(const char* name
) const
311 return ((this->pti_
->attributes_section
!= NULL
312 && strcmp(name
, this->pti_
->attributes_section
) == 0)
313 || strcmp(name
, ".gnu.attributes") == 0);
316 // Return a bit mask of argument types for attribute with TAG.
318 attribute_arg_type(int tag
) const
319 { return this->do_attribute_arg_type(tag
); }
321 // Return the attribute tag of the position NUM in the list of fixed
322 // attributes. Normally there is no reordering and
323 // attributes_order(NUM) == NUM.
325 attributes_order(int num
) const
326 { return this->do_attributes_order(num
); }
328 // When a target is selected as the default target, we call this method,
329 // which may be used for expensive, target-specific initialization.
331 select_as_default_target()
332 { this->do_select_as_default_target(); }
335 // This struct holds the constant information for a child class. We
336 // use a struct to avoid the overhead of virtual function calls for
337 // simple information.
340 // Address size (32 or 64).
342 // Whether the target is big endian.
344 // The code to store in the e_machine field of the ELF header.
345 elfcpp::EM machine_code
;
346 // Whether this target has a specific make_symbol function.
347 bool has_make_symbol
;
348 // Whether this target has a specific resolve function.
350 // Whether this target has a specific code fill function.
352 // Whether an object file with no .note.GNU-stack sections implies
353 // that the stack should be executable.
354 bool is_default_stack_executable
;
355 // Prefix character to strip when checking for wrapping.
357 // The default dynamic linker name.
358 const char* dynamic_linker
;
359 // The default text segment address.
360 uint64_t default_text_segment_address
;
361 // The ABI specified page size.
362 uint64_t abi_pagesize
;
363 // The common page size used by actual implementations.
364 uint64_t common_pagesize
;
365 // The special section index for small common symbols; SHN_UNDEF
367 elfcpp::Elf_Half small_common_shndx
;
368 // The special section index for large common symbols; SHN_UNDEF
370 elfcpp::Elf_Half large_common_shndx
;
371 // Section flags for small common section.
372 elfcpp::Elf_Xword small_common_section_flags
;
373 // Section flags for large common section.
374 elfcpp::Elf_Xword large_common_section_flags
;
375 // Name of attributes section if it is not ".gnu.attributes".
376 const char* attributes_section
;
377 // Vendor name of vendor attributes.
378 const char* attributes_vendor
;
381 Target(const Target_info
* pti
)
382 : pti_(pti
), processor_specific_flags_(0),
383 are_processor_specific_flags_set_(false)
386 // Virtual function which may be implemented by the child class.
388 do_new_output_section(Output_section
*) const
391 // Virtual function which may be implemented by the child class.
393 do_finalize_sections(Layout
*, const Input_objects
*, Symbol_table
*)
396 // Virtual function which may be implemented by the child class.
398 do_dynsym_value(const Symbol
*) const
399 { gold_unreachable(); }
401 // Virtual function which must be implemented by the child class if
404 do_code_fill(section_size_type
) const
405 { gold_unreachable(); }
407 // Virtual function which may be implemented by the child class.
409 do_is_defined_by_abi(const Symbol
*) const
412 // Adjust the output file header before it is written out. VIEW
413 // points to the header in external form. LEN is the length, and
414 // will be one of the values of elfcpp::Elf_sizes<size>::ehdr_size.
415 // By default, we do nothing.
417 do_adjust_elf_header(unsigned char*, int) const
420 // Virtual function which may be overriden by the child class.
422 do_is_local_label_name(const char*) const;
424 // Virtual function that must be overridden by a target which uses
425 // target specific relocations.
427 do_reloc_symbol_index(void*, unsigned int) const
428 { gold_unreachable(); }
430 // Virtual function that must be overidden by a target which uses
431 // target specific relocations.
433 do_reloc_addend(void*, unsigned int, uint64_t) const
434 { gold_unreachable(); }
436 // Virtual function which may be overridden by the child class.
438 do_calls_non_split(Relobj
* object
, unsigned int, section_offset_type
,
439 section_size_type
, unsigned char*, section_size_type
,
440 std::string
*, std::string
*) const;
442 // make_elf_object hooks. There are four versions of these for
443 // different address sizes and endianities.
445 // Set processor specific flags.
447 set_processor_specific_flags(elfcpp::Elf_Word flags
)
449 this->processor_specific_flags_
= flags
;
450 this->are_processor_specific_flags_set_
= true;
453 #ifdef HAVE_TARGET_32_LITTLE
454 // Virtual functions which may be overriden by the child class.
456 do_make_elf_object(const std::string
&, Input_file
*, off_t
,
457 const elfcpp::Ehdr
<32, false>&);
460 #ifdef HAVE_TARGET_32_BIG
461 // Virtual functions which may be overriden by the child class.
463 do_make_elf_object(const std::string
&, Input_file
*, off_t
,
464 const elfcpp::Ehdr
<32, true>&);
467 #ifdef HAVE_TARGET_64_LITTLE
468 // Virtual functions which may be overriden by the child class.
470 do_make_elf_object(const std::string
&, Input_file
*, off_t
,
471 const elfcpp::Ehdr
<64, false>& ehdr
);
474 #ifdef HAVE_TARGET_64_BIG
475 // Virtual functions which may be overriden by the child class.
477 do_make_elf_object(const std::string
& name
, Input_file
* input_file
,
478 off_t offset
, const elfcpp::Ehdr
<64, true>& ehdr
);
481 // Virtual functions which may be overriden by the child class.
482 virtual Output_section
*
483 do_make_output_section(const char* name
, elfcpp::Elf_Word type
,
484 elfcpp::Elf_Xword flags
);
486 // Virtual function which may be overriden by the child class.
489 { return parameters
->options().relax(); }
491 // Virtual function which may be overriden by the child class.
493 do_relax(int, const Input_objects
*, Symbol_table
*, Layout
*)
496 // A function for targets to call. Return whether BYTES/LEN matches
497 // VIEW/VIEW_SIZE at OFFSET.
499 match_view(const unsigned char* view
, section_size_type view_size
,
500 section_offset_type offset
, const char* bytes
, size_t len
) const;
502 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
505 set_view_to_nop(unsigned char* view
, section_size_type view_size
,
506 section_offset_type offset
, size_t len
) const;
508 // This must be overriden by the child class if it has target-specific
509 // attributes subsection in the attribute section.
511 do_attribute_arg_type(int) const
512 { gold_unreachable(); }
514 // This may be overridden by the child class.
516 do_attributes_order(int num
) const
519 // This may be overridden by the child class.
521 do_select_as_default_target()
525 // The implementations of the four do_make_elf_object virtual functions are
526 // almost identical except for their sizes and endianity. We use a template.
527 // for their implementations.
528 template<int size
, bool big_endian
>
530 do_make_elf_object_implementation(const std::string
&, Input_file
*, off_t
,
531 const elfcpp::Ehdr
<size
, big_endian
>&);
533 Target(const Target
&);
534 Target
& operator=(const Target
&);
536 // The target information.
537 const Target_info
* pti_
;
538 // Processor-specific flags.
539 elfcpp::Elf_Word processor_specific_flags_
;
540 // Whether the processor-specific flags are set at least once.
541 bool are_processor_specific_flags_set_
;
544 // The abstract class for a specific size and endianness of target.
545 // Each actual target implementation class should derive from an
546 // instantiation of Sized_target.
548 template<int size
, bool big_endian
>
549 class Sized_target
: public Target
552 // Make a new symbol table entry for the target. This should be
553 // overridden by a target which needs additional information in the
554 // symbol table. This will only be called if has_make_symbol()
556 virtual Sized_symbol
<size
>*
558 { gold_unreachable(); }
560 // Resolve a symbol for the target. This should be overridden by a
561 // target which needs to take special action. TO is the
562 // pre-existing symbol. SYM is the new symbol, seen in OBJECT.
563 // VERSION is the version of SYM. This will only be called if
564 // has_resolve() returns true.
566 resolve(Symbol
*, const elfcpp::Sym
<size
, big_endian
>&, Object
*,
568 { gold_unreachable(); }
570 // Process the relocs for a section, and record information of the
571 // mapping from source to destination sections. This mapping is later
572 // used to determine unreferenced garbage sections. This procedure is
573 // only called during garbage collection.
575 gc_process_relocs(Symbol_table
* symtab
,
577 Sized_relobj
<size
, big_endian
>* object
,
578 unsigned int data_shndx
,
579 unsigned int sh_type
,
580 const unsigned char* prelocs
,
582 Output_section
* output_section
,
583 bool needs_special_offset_handling
,
584 size_t local_symbol_count
,
585 const unsigned char* plocal_symbols
) = 0;
587 // Scan the relocs for a section, and record any information
588 // required for the symbol. SYMTAB is the symbol table. OBJECT is
589 // the object in which the section appears. DATA_SHNDX is the
590 // section index that these relocs apply to. SH_TYPE is the type of
591 // the relocation section, SHT_REL or SHT_RELA. PRELOCS points to
592 // the relocation data. RELOC_COUNT is the number of relocs.
593 // LOCAL_SYMBOL_COUNT is the number of local symbols.
594 // OUTPUT_SECTION is the output section.
595 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
596 // sections are not mapped as usual. PLOCAL_SYMBOLS points to the
597 // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of
598 // pointers to the global symbol table from OBJECT.
600 scan_relocs(Symbol_table
* symtab
,
602 Sized_relobj
<size
, big_endian
>* object
,
603 unsigned int data_shndx
,
604 unsigned int sh_type
,
605 const unsigned char* prelocs
,
607 Output_section
* output_section
,
608 bool needs_special_offset_handling
,
609 size_t local_symbol_count
,
610 const unsigned char* plocal_symbols
) = 0;
612 // Relocate section data. SH_TYPE is the type of the relocation
613 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
614 // information. RELOC_COUNT is the number of relocs.
615 // OUTPUT_SECTION is the output section.
616 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
617 // to correspond to the output section. VIEW is a view into the
618 // output file holding the section contents, VIEW_ADDRESS is the
619 // virtual address of the view, and VIEW_SIZE is the size of the
620 // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
621 // parameters refer to the complete output section data, not just
622 // the input section data.
624 relocate_section(const Relocate_info
<size
, big_endian
>*,
625 unsigned int sh_type
,
626 const unsigned char* prelocs
,
628 Output_section
* output_section
,
629 bool needs_special_offset_handling
,
631 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
632 section_size_type view_size
,
633 const Reloc_symbol_changes
*) = 0;
635 // Scan the relocs during a relocatable link. The parameters are
636 // like scan_relocs, with an additional Relocatable_relocs
637 // parameter, used to record the disposition of the relocs.
639 scan_relocatable_relocs(Symbol_table
* symtab
,
641 Sized_relobj
<size
, big_endian
>* object
,
642 unsigned int data_shndx
,
643 unsigned int sh_type
,
644 const unsigned char* prelocs
,
646 Output_section
* output_section
,
647 bool needs_special_offset_handling
,
648 size_t local_symbol_count
,
649 const unsigned char* plocal_symbols
,
650 Relocatable_relocs
*) = 0;
652 // Relocate a section during a relocatable link. The parameters are
653 // like relocate_section, with additional parameters for the view of
654 // the output reloc section.
656 relocate_for_relocatable(const Relocate_info
<size
, big_endian
>*,
657 unsigned int sh_type
,
658 const unsigned char* prelocs
,
660 Output_section
* output_section
,
661 off_t offset_in_output_section
,
662 const Relocatable_relocs
*,
664 typename
elfcpp::Elf_types
<size
>::Elf_Addr
666 section_size_type view_size
,
667 unsigned char* reloc_view
,
668 section_size_type reloc_view_size
) = 0;
671 Sized_target(const Target::Target_info
* pti
)
674 gold_assert(pti
->size
== size
);
675 gold_assert(pti
->is_big_endian
? big_endian
: !big_endian
);
679 } // End namespace gold.
681 #endif // !defined(GOLD_TARGET_H)