1 // target.h -- target support for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008 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"
43 class General_options
;
45 template<int size
, bool big_endian
>
47 class Relocatable_relocs
;
48 template<int size
, bool big_endian
>
56 // The abstract class for target specific handling.
64 // Return the bit size that this target implements. This should
68 { return this->pti_
->size
; }
70 // Return whether this target is big-endian.
73 { return this->pti_
->is_big_endian
; }
75 // Machine code to store in e_machine field of ELF header.
78 { return this->pti_
->machine_code
; }
80 // Whether this target has a specific make_symbol function.
82 has_make_symbol() const
83 { return this->pti_
->has_make_symbol
; }
85 // Whether this target has a specific resolve function.
88 { return this->pti_
->has_resolve
; }
90 // Whether this target has a specific code fill function.
93 { return this->pti_
->has_code_fill
; }
95 // Return the default name of the dynamic linker.
97 dynamic_linker() const
98 { return this->pti_
->dynamic_linker
; }
100 // Return the default address to use for the text segment.
102 default_text_segment_address() const
103 { return this->pti_
->default_text_segment_address
; }
105 // Return the ABI specified page size.
109 if (parameters
->options().max_page_size() > 0)
110 return parameters
->options().max_page_size();
112 return this->pti_
->abi_pagesize
;
115 // Return the common page size used on actual systems.
117 common_pagesize() const
119 if (parameters
->options().common_page_size() > 0)
120 return std::min(parameters
->options().common_page_size(),
121 this->abi_pagesize());
123 return std::min(this->pti_
->common_pagesize
,
124 this->abi_pagesize());
127 // If we see some object files with .note.GNU-stack sections, and
128 // some objects files without them, this returns whether we should
129 // consider the object files without them to imply that the stack
130 // should be executable.
132 is_default_stack_executable() const
133 { return this->pti_
->is_default_stack_executable
; }
135 // This is called to tell the target to complete any sections it is
136 // handling. After this all sections must have their final size.
138 finalize_sections(Layout
* layout
)
139 { return this->do_finalize_sections(layout
); }
141 // Return the value to use for a global symbol which needs a special
142 // value in the dynamic symbol table. This will only be called if
143 // the backend first calls symbol->set_needs_dynsym_value().
145 dynsym_value(const Symbol
* sym
) const
146 { return this->do_dynsym_value(sym
); }
148 // Return a string to use to fill out a code section. This is
149 // basically one or more NOPS which must fill out the specified
152 code_fill(section_size_type length
) const
153 { return this->do_code_fill(length
); }
155 // Return whether SYM is known to be defined by the ABI. This is
156 // used to avoid inappropriate warnings about undefined symbols.
158 is_defined_by_abi(Symbol
* sym
) const
159 { return this->do_is_defined_by_abi(sym
); }
162 // This struct holds the constant information for a child class. We
163 // use a struct to avoid the overhead of virtual function calls for
164 // simple information.
167 // Address size (32 or 64).
169 // Whether the target is big endian.
171 // The code to store in the e_machine field of the ELF header.
172 elfcpp::EM machine_code
;
173 // Whether this target has a specific make_symbol function.
174 bool has_make_symbol
;
175 // Whether this target has a specific resolve function.
177 // Whether this target has a specific code fill function.
179 // Whether an object file with no .note.GNU-stack sections implies
180 // that the stack should be executable.
181 bool is_default_stack_executable
;
182 // The default dynamic linker name.
183 const char* dynamic_linker
;
184 // The default text segment address.
185 uint64_t default_text_segment_address
;
186 // The ABI specified page size.
187 uint64_t abi_pagesize
;
188 // The common page size used by actual implementations.
189 uint64_t common_pagesize
;
192 Target(const Target_info
* pti
)
196 // Virtual function which may be implemented by the child class.
198 do_finalize_sections(Layout
*)
201 // Virtual function which may be implemented by the child class.
203 do_dynsym_value(const Symbol
*) const
204 { gold_unreachable(); }
206 // Virtual function which must be implemented by the child class if
209 do_code_fill(section_size_type
) const
210 { gold_unreachable(); }
212 // Virtual function which may be implemented by the child class.
214 do_is_defined_by_abi(Symbol
*) const
218 Target(const Target
&);
219 Target
& operator=(const Target
&);
221 // The target information.
222 const Target_info
* pti_
;
225 // The abstract class for a specific size and endianness of target.
226 // Each actual target implementation class should derive from an
227 // instantiation of Sized_target.
229 template<int size
, bool big_endian
>
230 class Sized_target
: public Target
233 // Make a new symbol table entry for the target. This should be
234 // overridden by a target which needs additional information in the
235 // symbol table. This will only be called if has_make_symbol()
237 virtual Sized_symbol
<size
>*
239 { gold_unreachable(); }
241 // Resolve a symbol for the target. This should be overridden by a
242 // target which needs to take special action. TO is the
243 // pre-existing symbol. SYM is the new symbol, seen in OBJECT.
244 // VERSION is the version of SYM. This will only be called if
245 // has_resolve() returns true.
247 resolve(Symbol
*, const elfcpp::Sym
<size
, big_endian
>&, Object
*,
249 { gold_unreachable(); }
251 // Scan the relocs for a section, and record any information
252 // required for the symbol. OPTIONS is the command line options.
253 // SYMTAB is the symbol table. OBJECT is the object in which the
254 // section appears. DATA_SHNDX is the section index that these
255 // relocs apply to. SH_TYPE is the type of the relocation section,
256 // SHT_REL or SHT_RELA. PRELOCS points to the relocation data.
257 // RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the
258 // number of local symbols. OUTPUT_SECTION is the output section.
259 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
260 // sections are not mapped as usual. PLOCAL_SYMBOLS points to the
261 // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of
262 // pointers to the global symbol table from OBJECT.
264 scan_relocs(const General_options
& options
,
265 Symbol_table
* symtab
,
267 Sized_relobj
<size
, big_endian
>* object
,
268 unsigned int data_shndx
,
269 unsigned int sh_type
,
270 const unsigned char* prelocs
,
272 Output_section
* output_section
,
273 bool needs_special_offset_handling
,
274 size_t local_symbol_count
,
275 const unsigned char* plocal_symbols
) = 0;
277 // Relocate section data. SH_TYPE is the type of the relocation
278 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
279 // information. RELOC_COUNT is the number of relocs.
280 // OUTPUT_SECTION is the output section.
281 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
282 // to correspond to the output section. VIEW is a view into the
283 // output file holding the section contents, VIEW_ADDRESS is the
284 // virtual address of the view, and VIEW_SIZE is the size of the
285 // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
286 // parameters refer to the complete output section data, not just
287 // the input section data.
289 relocate_section(const Relocate_info
<size
, big_endian
>*,
290 unsigned int sh_type
,
291 const unsigned char* prelocs
,
293 Output_section
* output_section
,
294 bool needs_special_offset_handling
,
296 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
297 section_size_type view_size
) = 0;
299 // Scan the relocs during a relocatable link. The parameters are
300 // like scan_relocs, with an additional Relocatable_relocs
301 // parameter, used to record the disposition of the relocs.
303 scan_relocatable_relocs(const General_options
& options
,
304 Symbol_table
* symtab
,
306 Sized_relobj
<size
, big_endian
>* object
,
307 unsigned int data_shndx
,
308 unsigned int sh_type
,
309 const unsigned char* prelocs
,
311 Output_section
* output_section
,
312 bool needs_special_offset_handling
,
313 size_t local_symbol_count
,
314 const unsigned char* plocal_symbols
,
315 Relocatable_relocs
*) = 0;
317 // Relocate a section during a relocatable link. The parameters are
318 // like relocate_section, with additional parameters for the view of
319 // the output reloc section.
321 relocate_for_relocatable(const Relocate_info
<size
, big_endian
>*,
322 unsigned int sh_type
,
323 const unsigned char* prelocs
,
325 Output_section
* output_section
,
326 off_t offset_in_output_section
,
327 const Relocatable_relocs
*,
329 typename
elfcpp::Elf_types
<size
>::Elf_Addr
331 section_size_type view_size
,
332 unsigned char* reloc_view
,
333 section_size_type reloc_view_size
) = 0;
336 Sized_target(const Target::Target_info
* pti
)
339 gold_assert(pti
->size
== size
);
340 gold_assert(pti
->is_big_endian
? big_endian
: !big_endian
);
344 } // End namespace gold.
346 #endif // !defined(GOLD_TARGET_H)