1 // target.h -- target support 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.
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.
41 class General_options
;
43 template<int size
, bool big_endian
>
45 template<int size
, bool big_endian
>
53 // The abstract class for target specific handling.
61 // Return the bit size that this target implements. This should
65 { return this->pti_
->size
; }
67 // Return whether this target is big-endian.
70 { return this->pti_
->is_big_endian
; }
72 // Machine code to store in e_machine field of ELF header.
75 { return this->pti_
->machine_code
; }
77 // Whether this target has a specific make_symbol function.
79 has_make_symbol() const
80 { return this->pti_
->has_make_symbol
; }
82 // Whether this target has a specific resolve function.
85 { return this->pti_
->has_resolve
; }
87 // Whether this target has a specific code fill function.
90 { return this->pti_
->has_code_fill
; }
92 // Return the default name of the dynamic linker.
94 dynamic_linker() const
95 { return this->pti_
->dynamic_linker
; }
97 // Return the default address to use for the text segment.
99 default_text_segment_address() const
100 { return this->pti_
->default_text_segment_address
; }
102 // Return the ABI specified page size.
105 { return this->pti_
->abi_pagesize
; }
107 // Return the common page size used on actual systems.
109 common_pagesize() const
110 { return this->pti_
->common_pagesize
; }
112 // If we see some object files with .note.GNU-stack sections, and
113 // some objects files without them, this returns whether we should
114 // consider the object files without them to imply that the stack
115 // should be executable.
117 is_default_stack_executable() const
118 { return this->pti_
->is_default_stack_executable
; }
120 // This is called to tell the target to complete any sections it is
121 // handling. After this all sections must have their final size.
123 finalize_sections(Layout
* layout
)
124 { return this->do_finalize_sections(layout
); }
126 // Return the value to use for a global symbol which needs a special
127 // value in the dynamic symbol table. This will only be called if
128 // the backend first calls symbol->set_needs_dynsym_value().
130 dynsym_value(const Symbol
* sym
) const
131 { return this->do_dynsym_value(sym
); }
133 // Return a string to use to fill out a code section. This is
134 // basically one or more NOPS which must fill out the specified
137 code_fill(off_t length
)
138 { return this->do_code_fill(length
); }
140 // Return whether SYM is a special symbol which is known to be
141 // defined. This is used to avoid inappropriate warnings about
142 // undefined symbols.
144 is_always_defined(Symbol
* sym
) const
145 { return this->do_is_always_defined(sym
); }
148 // This struct holds the constant information for a child class. We
149 // use a struct to avoid the overhead of virtual function calls for
150 // simple information.
153 // Address size (32 or 64).
155 // Whether the target is big endian.
157 // The code to store in the e_machine field of the ELF header.
158 elfcpp::EM machine_code
;
159 // Whether this target has a specific make_symbol function.
160 bool has_make_symbol
;
161 // Whether this target has a specific resolve function.
163 // Whether this target has a specific code fill function.
165 // Whether an object file with no .note.GNU-stack sections implies
166 // that the stack should be executable.
167 bool is_default_stack_executable
;
168 // The default dynamic linker name.
169 const char* dynamic_linker
;
170 // The default text segment address.
171 uint64_t default_text_segment_address
;
172 // The ABI specified page size.
173 uint64_t abi_pagesize
;
174 // The common page size used by actual implementations.
175 uint64_t common_pagesize
;
178 Target(const Target_info
* pti
)
182 // Virtual function which may be implemented by the child class.
184 do_finalize_sections(Layout
*)
187 // Virtual function which may be implemented by the child class.
189 do_dynsym_value(const Symbol
*) const
190 { gold_unreachable(); }
192 // Virtual function which must be implemented by the child class if
196 { gold_unreachable(); }
198 // Virtual function which may be implemented by the child class if
201 do_is_always_defined(Symbol
*) const
205 Target(const Target
&);
206 Target
& operator=(const Target
&);
208 // The target information.
209 const Target_info
* pti_
;
212 // The abstract class for a specific size and endianness of target.
213 // Each actual target implementation class should derive from an
214 // instantiation of Sized_target.
216 template<int size
, bool big_endian
>
217 class Sized_target
: public Target
220 // Make a new symbol table entry for the target. This should be
221 // overridden by a target which needs additional information in the
222 // symbol table. This will only be called if has_make_symbol()
224 virtual Sized_symbol
<size
>*
226 { gold_unreachable(); }
228 // Resolve a symbol for the target. This should be overridden by a
229 // target which needs to take special action. TO is the
230 // pre-existing symbol. SYM is the new symbol, seen in OBJECT.
231 // VERSION is the version of SYM. This will only be called if
232 // has_resolve() returns true.
234 resolve(Symbol
*, const elfcpp::Sym
<size
, big_endian
>&, Object
*,
236 { gold_unreachable(); }
238 // Scan the relocs for a section, and record any information
239 // required for the symbol. OPTIONS is the command line options.
240 // SYMTAB is the symbol table. OBJECT is the object in which the
241 // section appears. DATA_SHNDX is the section index that these
242 // relocs apply to. SH_TYPE is the type of the relocation section,
243 // SHT_REL or SHT_RELA. PRELOCS points to the relocation data.
244 // RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the
245 // number of local symbols. OUTPUT_SECTION is the output section.
246 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
247 // sections are not mapped as usual. PLOCAL_SYMBOLS points to the
248 // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of
249 // pointers to the global symbol table from OBJECT.
251 scan_relocs(const General_options
& options
,
252 Symbol_table
* symtab
,
254 Sized_relobj
<size
, big_endian
>* object
,
255 unsigned int data_shndx
,
256 unsigned int sh_type
,
257 const unsigned char* prelocs
,
259 Output_section
* output_section
,
260 bool needs_special_offset_handling
,
261 size_t local_symbol_count
,
262 const unsigned char* plocal_symbols
) = 0;
264 // Relocate section data. SH_TYPE is the type of the relocation
265 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
266 // information. RELOC_COUNT is the number of relocs.
267 // OUTPUT_SECTION is the output section.
268 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
269 // to correspond to the output section. VIEW is a view into the
270 // output file holding the section contents, VIEW_ADDRESS is the
271 // virtual address of the view, and VIEW_SIZE is the size of the
272 // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
273 // parameters refer to the complete output section data, not just
274 // the input section data.
276 relocate_section(const Relocate_info
<size
, big_endian
>*,
277 unsigned int sh_type
,
278 const unsigned char* prelocs
,
280 Output_section
* output_section
,
281 bool needs_special_offset_handling
,
283 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
284 off_t view_size
) = 0;
287 Sized_target(const Target::Target_info
* pti
)
290 gold_assert(pti
->size
== size
);
291 gold_assert(pti
->is_big_endian
? big_endian
: !big_endian
);
295 } // End namespace gold.
297 #endif // !defined(GOLD_TARGET_H)