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>
52 // The abstract class for target specific handling.
60 // Return the bit size that this target implements. This should
64 { return this->pti_->size; }
66 // Return whether this target is big-endian.
69 { return this->pti_->is_big_endian; }
71 // Machine code to store in e_machine field of ELF header.
74 { return this->pti_->machine_code; }
76 // Whether this target has a specific make_symbol function.
78 has_make_symbol() const
79 { return this->pti_->has_make_symbol; }
81 // Whether this target has a specific resolve function.
84 { return this->pti_->has_resolve; }
86 // Whether this target has a specific code fill function.
89 { return this->pti_->has_code_fill; }
91 // Return the default name of the dynamic linker.
93 dynamic_linker() const
94 { return this->pti_->dynamic_linker; }
96 // Return the default address to use for the text segment.
98 default_text_segment_address() const
99 { return this->pti_->default_text_segment_address; }
101 // Return the ABI specified page size.
104 { return this->pti_->abi_pagesize; }
106 // Return the common page size used on actual systems.
108 common_pagesize() const
109 { return this->pti_->common_pagesize; }
111 // If we see some object files with .note.GNU-stack sections, and
112 // some objects files without them, this returns whether we should
113 // consider the object files without them to imply that the stack
114 // should be executable.
116 is_default_stack_executable() const
117 { return this->pti_->is_default_stack_executable; }
119 // This is called to tell the target to complete any sections it is
120 // handling. After this all sections must have their final size.
122 finalize_sections(Layout* layout)
123 { return this->do_finalize_sections(layout); }
125 // Return the value to use for a global symbol which needs a special
126 // value in the dynamic symbol table. This will only be called if
127 // the backend first calls symbol->set_needs_dynsym_value().
129 dynsym_value(const Symbol* sym) const
130 { return this->do_dynsym_value(sym); }
132 // Return a string to use to fill out a code section. This is
133 // basically one or more NOPS which must fill out the specified
136 code_fill(off_t length)
137 { return this->do_code_fill(length); }
140 // This struct holds the constant information for a child class. We
141 // use a struct to avoid the overhead of virtual function calls for
142 // simple information.
145 // Address size (32 or 64).
147 // Whether the target is big endian.
149 // The code to store in the e_machine field of the ELF header.
150 elfcpp::EM machine_code;
151 // Whether this target has a specific make_symbol function.
152 bool has_make_symbol;
153 // Whether this target has a specific resolve function.
155 // Whether this target has a specific code fill function.
157 // Whether an object file with no .note.GNU-stack sections implies
158 // that the stack should be executable.
159 bool is_default_stack_executable;
160 // The default dynamic linker name.
161 const char* dynamic_linker;
162 // The default text segment address.
163 uint64_t default_text_segment_address;
164 // The ABI specified page size.
165 uint64_t abi_pagesize;
166 // The common page size used by actual implementations.
167 uint64_t common_pagesize;
170 Target(const Target_info* pti)
174 // Virtual function which may be implemented by the child class.
176 do_finalize_sections(Layout*)
179 // Virtual function which may be implemented by the child class.
181 do_dynsym_value(const Symbol*) const
182 { gold_unreachable(); }
184 // Virtual function which must be implemented by the child class if
188 { gold_unreachable(); }
191 Target(const Target&);
192 Target& operator=(const Target&);
194 // The target information.
195 const Target_info* pti_;
198 // The abstract class for a specific size and endianness of target.
199 // Each actual target implementation class should derive from an
200 // instantiation of Sized_target.
202 template<int size, bool big_endian>
203 class Sized_target : public Target
206 // Make a new symbol table entry for the target. This should be
207 // overridden by a target which needs additional information in the
208 // symbol table. This will only be called if has_make_symbol()
210 virtual Sized_symbol<size>*
212 { gold_unreachable(); }
214 // Resolve a symbol for the target. This should be overridden by a
215 // target which needs to take special action. TO is the
216 // pre-existing symbol. SYM is the new symbol, seen in OBJECT.
217 // VERSION is the version of SYM. This will only be called if
218 // has_resolve() returns true.
220 resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
222 { gold_unreachable(); }
224 // Scan the relocs for a section, and record any information
225 // required for the symbol. OPTIONS is the command line options.
226 // SYMTAB is the symbol table. OBJECT is the object in which the
227 // section appears. DATA_SHNDX is the section index that these
228 // relocs apply to. SH_TYPE is the type of the relocation section,
229 // SHT_REL or SHT_RELA. PRELOCS points to the relocation data.
230 // RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the
231 // number of local symbols. PLOCAL_SYMBOLS points to the local
232 // symbol data from OBJECT. GLOBAL_SYMBOLS is the array of pointers
233 // to the global symbol table from OBJECT.
235 scan_relocs(const General_options& options,
236 Symbol_table* symtab,
238 Sized_relobj<size, big_endian>* object,
239 unsigned int data_shndx,
240 unsigned int sh_type,
241 const unsigned char* prelocs,
243 size_t local_symbol_count,
244 const unsigned char* plocal_symbols,
245 Symbol** global_symbols) = 0;
247 // Relocate section data. SH_TYPE is the type of the relocation
248 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
249 // information. RELOC_COUNT is the number of relocs. VIEW is a
250 // view into the output file holding the section contents,
251 // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
252 // the size of the view.
254 relocate_section(const Relocate_info<size, big_endian>*,
255 unsigned int sh_type,
256 const unsigned char* prelocs,
259 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
260 off_t view_size) = 0;
263 Sized_target(const Target::Target_info* pti)
266 gold_assert(pti->size == size);
267 gold_assert(pti->is_big_endian ? big_endian : !big_endian);
271 } // End namespace gold.
273 #endif // !defined(GOLD_TARGET_H)