1 // target.cc -- target support for gold. 2 3 // Copyright (C) 2009-2016 Free Software Foundation, Inc. 4 // Written by Doug Kwan <dougkwan (at) google.com>. 5 6 // This file is part of gold. 7 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. 12 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. 17 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. 22 23 #include "gold.h" 24 #include "elfcpp.h" 25 #include "dynobj.h" 26 #include "symtab.h" 27 #include "output.h" 28 #include "target.h" 29 30 namespace gold 31 { 32 33 // Return whether NAME is a local label name. This is used to implement the 34 // --discard-locals options and can be overridden by child classes to 35 // implement system-specific behaviour. The logic here is the same as that 36 // in _bfd_elf_is_local_label_name(). 37 38 bool 39 Target::do_is_local_label_name(const char* name) const 40 { 41 // Normal local symbols start with ``.L''. 42 if (name[0] == '.' && name[1] == 'L') 43 return true; 44 45 // At least some SVR4 compilers (e.g., UnixWare 2.1 cc) generate 46 // DWARF debugging symbols starting with ``..''. 47 if (name[0] == '.' && name[1] == '.') 48 return true; 49 50 // gcc will sometimes generate symbols beginning with ``_.L_'' when 51 // emitting DWARF debugging output. I suspect this is actually a 52 // small bug in gcc (it calls ASM_OUTPUT_LABEL when it should call 53 // ASM_GENERATE_INTERNAL_LABEL, and this causes the leading 54 // underscore to be emitted on some ELF targets). For ease of use, 55 // we treat such symbols as local. 56 if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_') 57 return true; 58 59 return false; 60 } 61 62 // Implementations of methods Target::do_make_elf_object are almost identical 63 // except for the address sizes and endianities. So we extract this 64 // into a template. 65 66 template<int size, bool big_endian> 67 inline Object* 68 Target::do_make_elf_object_implementation( 69 const std::string& name, 70 Input_file* input_file, 71 off_t offset, 72 const elfcpp::Ehdr<size, big_endian>& ehdr) 73 { 74 int et = ehdr.get_e_type(); 75 // ET_EXEC files are valid input for --just-symbols/-R, 76 // and we treat them as relocatable objects. 77 if (et == elfcpp::ET_REL 78 || (et == elfcpp::ET_EXEC && input_file->just_symbols())) 79 { 80 Sized_relobj_file<size, big_endian>* obj = 81 new Sized_relobj_file<size, big_endian>(name, input_file, offset, ehdr); 82 obj->setup(); 83 return obj; 84 } 85 else if (et == elfcpp::ET_DYN) 86 { 87 Sized_dynobj<size, big_endian>* obj = 88 new Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr); 89 obj->setup(); 90 return obj; 91 } 92 else 93 { 94 gold_error(_("%s: unsupported ELF file type %d"), 95 name.c_str(), et); 96 return NULL; 97 } 98 } 99 100 // Make an ELF object called NAME by reading INPUT_FILE at OFFSET. EHDR 101 // is the ELF header of the object. There are four versions of this 102 // for different address sizes and endianities. 103 104 #ifdef HAVE_TARGET_32_LITTLE 105 Object* 106 Target::do_make_elf_object(const std::string& name, Input_file* input_file, 107 off_t offset, const elfcpp::Ehdr<32, false>& ehdr) 108 { 109 return this->do_make_elf_object_implementation<32, false>(name, input_file, 110 offset, ehdr); 111 } 112 #endif 113 114 #ifdef HAVE_TARGET_32_BIG 115 Object* 116 Target::do_make_elf_object(const std::string& name, Input_file* input_file, 117 off_t offset, const elfcpp::Ehdr<32, true>& ehdr) 118 { 119 return this->do_make_elf_object_implementation<32, true>(name, input_file, 120 offset, ehdr); 121 } 122 #endif 123 124 #ifdef HAVE_TARGET_64_LITTLE 125 Object* 126 Target::do_make_elf_object(const std::string& name, Input_file* input_file, 127 off_t offset, const elfcpp::Ehdr<64, false>& ehdr) 128 { 129 return this->do_make_elf_object_implementation<64, false>(name, input_file, 130 offset, ehdr); 131 } 132 #endif 133 134 #ifdef HAVE_TARGET_64_BIG 135 Object* 136 Target::do_make_elf_object(const std::string& name, Input_file* input_file, 137 off_t offset, const elfcpp::Ehdr<64, true>& ehdr) 138 { 139 return this->do_make_elf_object_implementation<64, true>(name, input_file, 140 offset, ehdr); 141 } 142 #endif 143 144 Output_section* 145 Target::do_make_output_section(const char* name, elfcpp::Elf_Word type, 146 elfcpp::Elf_Xword flags) 147 { 148 return new Output_section(name, type, flags); 149 } 150 151 // Default for whether a reloc is a call to a non-split function is 152 // whether the symbol is a function. 153 154 bool 155 Target::do_is_call_to_non_split(const Symbol* sym, const unsigned char*, 156 const unsigned char*, section_size_type) const 157 { 158 return sym->type() == elfcpp::STT_FUNC; 159 } 160 161 // Default conversion for -fsplit-stack is to give an error. 162 163 void 164 Target::do_calls_non_split(Relobj* object, unsigned int, section_offset_type, 165 section_size_type, const unsigned char*, size_t, 166 unsigned char*, section_size_type, 167 std::string*, std::string*) const 168 { 169 static bool warned; 170 if (!warned) 171 { 172 gold_error(_("linker does not include stack split support " 173 "required by %s"), 174 object->name().c_str()); 175 warned = true; 176 } 177 } 178 179 // Return whether BYTES/LEN matches VIEW/VIEW_SIZE at OFFSET. 180 181 bool 182 Target::match_view(const unsigned char* view, section_size_type view_size, 183 section_offset_type offset, const char* bytes, 184 size_t len) const 185 { 186 if (offset + len > view_size) 187 return false; 188 return memcmp(view + offset, bytes, len) == 0; 189 } 190 191 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET 192 // for LEN bytes. 193 194 void 195 Target::set_view_to_nop(unsigned char* view, section_size_type view_size, 196 section_offset_type offset, size_t len) const 197 { 198 gold_assert(offset >= 0 && offset + len <= view_size); 199 if (!this->has_code_fill()) 200 memset(view + offset, 0, len); 201 else 202 { 203 std::string fill = this->code_fill(len); 204 memcpy(view + offset, fill.data(), len); 205 } 206 } 207 208 // Return address and size to plug into eh_frame FDEs associated with a PLT. 209 void 210 Target::do_plt_fde_location(const Output_data* plt, unsigned char*, 211 uint64_t* address, off_t* len) const 212 { 213 *address = plt->address(); 214 *len = plt->data_size(); 215 } 216 217 // Class Sized_target. 218 219 // Set the EI_OSABI field of the ELF header if requested. 220 221 template<int size, bool big_endian> 222 void 223 Sized_target<size, big_endian>::do_adjust_elf_header(unsigned char* view, 224 int len) 225 { 226 elfcpp::ELFOSABI osabi = this->osabi(); 227 if (osabi != elfcpp::ELFOSABI_NONE) 228 { 229 gold_assert(len == elfcpp::Elf_sizes<size>::ehdr_size); 230 231 elfcpp::Ehdr<size, big_endian> ehdr(view); 232 unsigned char e_ident[elfcpp::EI_NIDENT]; 233 memcpy(e_ident, ehdr.get_e_ident(), elfcpp::EI_NIDENT); 234 235 e_ident[elfcpp::EI_OSABI] = osabi; 236 237 elfcpp::Ehdr_write<size, big_endian> oehdr(view); 238 oehdr.put_e_ident(e_ident); 239 } 240 } 241 242 #ifdef HAVE_TARGET_32_LITTLE 243 template 244 class Sized_target<32, false>; 245 #endif 246 247 #ifdef HAVE_TARGET_32_BIG 248 template 249 class Sized_target<32, true>; 250 #endif 251 252 #ifdef HAVE_TARGET_64_LITTLE 253 template 254 class Sized_target<64, false>; 255 #endif 256 257 #ifdef HAVE_TARGET_64_BIG 258 template 259 class Sized_target<64, true>; 260 #endif 261 262 } // End namespace gold. 263
