| 1 | // target.cc -- target support for gold. |
| 2 | |
| 3 | // Copyright (C) 2009-2020 Free Software Foundation, Inc. |
| 4 | // Written by Doug Kwan <dougkwan@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. |