| 1 | // common.cc -- handle common symbols for gold |
| 2 | |
| 3 | // Copyright (C) 2006-2018 Free Software Foundation, Inc. |
| 4 | // Written by Ian Lance Taylor <iant@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 | |
| 25 | #include <algorithm> |
| 26 | |
| 27 | #include "workqueue.h" |
| 28 | #include "mapfile.h" |
| 29 | #include "layout.h" |
| 30 | #include "output.h" |
| 31 | #include "symtab.h" |
| 32 | #include "common.h" |
| 33 | |
| 34 | namespace gold |
| 35 | { |
| 36 | |
| 37 | // Allocate_commons_task methods. |
| 38 | |
| 39 | // This task allocates the common symbols. We arrange to run it |
| 40 | // before anything else which needs to access the symbol table. |
| 41 | |
| 42 | Task_token* |
| 43 | Allocate_commons_task::is_runnable() |
| 44 | { |
| 45 | return NULL; |
| 46 | } |
| 47 | |
| 48 | // Release a blocker. |
| 49 | |
| 50 | void |
| 51 | Allocate_commons_task::locks(Task_locker* tl) |
| 52 | { |
| 53 | tl->add(this, this->blocker_); |
| 54 | } |
| 55 | |
| 56 | // Allocate the common symbols. |
| 57 | |
| 58 | void |
| 59 | Allocate_commons_task::run(Workqueue*) |
| 60 | { |
| 61 | this->symtab_->allocate_commons(this->layout_, this->mapfile_); |
| 62 | } |
| 63 | |
| 64 | // This class is used to sort the common symbol. We normally put the |
| 65 | // larger common symbols first. This can be changed by using |
| 66 | // --sort-commons, which tells the linker to sort by alignment. |
| 67 | |
| 68 | template<int size> |
| 69 | class Sort_commons |
| 70 | { |
| 71 | public: |
| 72 | Sort_commons(const Symbol_table* symtab, |
| 73 | Symbol_table::Sort_commons_order sort_order) |
| 74 | : symtab_(symtab), sort_order_(sort_order) |
| 75 | { } |
| 76 | |
| 77 | bool operator()(const Symbol* a, const Symbol* b) const; |
| 78 | |
| 79 | private: |
| 80 | // The symbol table. |
| 81 | const Symbol_table* symtab_; |
| 82 | // How to sort. |
| 83 | Symbol_table::Sort_commons_order sort_order_; |
| 84 | }; |
| 85 | |
| 86 | template<int size> |
| 87 | bool |
| 88 | Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const |
| 89 | { |
| 90 | if (pa == NULL) |
| 91 | return false; |
| 92 | if (pb == NULL) |
| 93 | return true; |
| 94 | |
| 95 | const Symbol_table* symtab = this->symtab_; |
| 96 | const Sized_symbol<size>* psa = symtab->get_sized_symbol<size>(pa); |
| 97 | const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb); |
| 98 | |
| 99 | // The size. |
| 100 | typename Sized_symbol<size>::Size_type sa = psa->symsize(); |
| 101 | typename Sized_symbol<size>::Size_type sb = psb->symsize(); |
| 102 | |
| 103 | // The alignment. |
| 104 | typename Sized_symbol<size>::Value_type aa = psa->value(); |
| 105 | typename Sized_symbol<size>::Value_type ab = psb->value(); |
| 106 | |
| 107 | if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_DESCENDING) |
| 108 | { |
| 109 | if (aa < ab) |
| 110 | return false; |
| 111 | else if (ab < aa) |
| 112 | return true; |
| 113 | } |
| 114 | else if (this->sort_order_ |
| 115 | == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_ASCENDING) |
| 116 | { |
| 117 | if (aa < ab) |
| 118 | return true; |
| 119 | else if (ab < aa) |
| 120 | return false; |
| 121 | } |
| 122 | else |
| 123 | gold_assert(this->sort_order_ |
| 124 | == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING); |
| 125 | |
| 126 | // Sort by descending size. |
| 127 | if (sa < sb) |
| 128 | return false; |
| 129 | else if (sb < sa) |
| 130 | return true; |
| 131 | |
| 132 | if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING) |
| 133 | { |
| 134 | // When the symbols are the same size, we sort them by |
| 135 | // alignment, largest alignment first. |
| 136 | if (aa < ab) |
| 137 | return false; |
| 138 | else if (ab < aa) |
| 139 | return true; |
| 140 | } |
| 141 | |
| 142 | // Otherwise we stabilize the sort by sorting by name. |
| 143 | return strcmp(psa->name(), psb->name()) < 0; |
| 144 | } |
| 145 | |
| 146 | // Allocate the common symbols. |
| 147 | |
| 148 | void |
| 149 | Symbol_table::allocate_commons(Layout* layout, Mapfile* mapfile) |
| 150 | { |
| 151 | Sort_commons_order sort_order; |
| 152 | if (!parameters->options().user_set_sort_common()) |
| 153 | sort_order = SORT_COMMONS_BY_SIZE_DESCENDING; |
| 154 | else |
| 155 | { |
| 156 | const char* order = parameters->options().sort_common(); |
| 157 | if (*order == '\0' || strcmp(order, "descending") == 0) |
| 158 | sort_order = SORT_COMMONS_BY_ALIGNMENT_DESCENDING; |
| 159 | else if (strcmp(order, "ascending") == 0) |
| 160 | sort_order = SORT_COMMONS_BY_ALIGNMENT_ASCENDING; |
| 161 | else |
| 162 | { |
| 163 | gold_error("invalid --sort-common argument: %s", order); |
| 164 | sort_order = SORT_COMMONS_BY_SIZE_DESCENDING; |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | if (parameters->target().get_size() == 32) |
| 169 | { |
| 170 | #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) |
| 171 | this->do_allocate_commons<32>(layout, mapfile, sort_order); |
| 172 | #else |
| 173 | gold_unreachable(); |
| 174 | #endif |
| 175 | } |
| 176 | else if (parameters->target().get_size() == 64) |
| 177 | { |
| 178 | #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) |
| 179 | this->do_allocate_commons<64>(layout, mapfile, sort_order); |
| 180 | #else |
| 181 | gold_unreachable(); |
| 182 | #endif |
| 183 | } |
| 184 | else |
| 185 | gold_unreachable(); |
| 186 | } |
| 187 | |
| 188 | // Allocated the common symbols, sized version. |
| 189 | |
| 190 | template<int size> |
| 191 | void |
| 192 | Symbol_table::do_allocate_commons(Layout* layout, Mapfile* mapfile, |
| 193 | Sort_commons_order sort_order) |
| 194 | { |
| 195 | if (!this->commons_.empty()) |
| 196 | this->do_allocate_commons_list<size>(layout, COMMONS_NORMAL, |
| 197 | &this->commons_, mapfile, |
| 198 | sort_order); |
| 199 | if (!this->tls_commons_.empty()) |
| 200 | this->do_allocate_commons_list<size>(layout, COMMONS_TLS, |
| 201 | &this->tls_commons_, mapfile, |
| 202 | sort_order); |
| 203 | if (!this->small_commons_.empty()) |
| 204 | this->do_allocate_commons_list<size>(layout, COMMONS_SMALL, |
| 205 | &this->small_commons_, mapfile, |
| 206 | sort_order); |
| 207 | if (!this->large_commons_.empty()) |
| 208 | this->do_allocate_commons_list<size>(layout, COMMONS_LARGE, |
| 209 | &this->large_commons_, mapfile, |
| 210 | sort_order); |
| 211 | } |
| 212 | |
| 213 | // Allocate the common symbols in a list. IS_TLS indicates whether |
| 214 | // these are TLS common symbols. |
| 215 | |
| 216 | template<int size> |
| 217 | void |
| 218 | Symbol_table::do_allocate_commons_list( |
| 219 | Layout* layout, |
| 220 | Commons_section_type commons_section_type, |
| 221 | Commons_type* commons, |
| 222 | Mapfile* mapfile, |
| 223 | Sort_commons_order sort_order) |
| 224 | { |
| 225 | // We've kept a list of all the common symbols. But the symbol may |
| 226 | // have been resolved to a defined symbol by now. And it may be a |
| 227 | // forwarder. First remove all non-common symbols. |
| 228 | bool any = false; |
| 229 | uint64_t addralign = 0; |
| 230 | for (Commons_type::iterator p = commons->begin(); |
| 231 | p != commons->end(); |
| 232 | ++p) |
| 233 | { |
| 234 | Symbol* sym = *p; |
| 235 | if (sym->is_forwarder()) |
| 236 | { |
| 237 | sym = this->resolve_forwards(sym); |
| 238 | *p = sym; |
| 239 | } |
| 240 | if (!sym->is_common()) |
| 241 | *p = NULL; |
| 242 | else |
| 243 | { |
| 244 | any = true; |
| 245 | Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); |
| 246 | if (ssym->value() > addralign) |
| 247 | addralign = ssym->value(); |
| 248 | } |
| 249 | } |
| 250 | if (!any) |
| 251 | return; |
| 252 | |
| 253 | // Sort the common symbols. |
| 254 | std::sort(commons->begin(), commons->end(), |
| 255 | Sort_commons<size>(this, sort_order)); |
| 256 | |
| 257 | // Place them in a newly allocated BSS section. |
| 258 | elfcpp::Elf_Xword flags = elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC; |
| 259 | const char* name; |
| 260 | const char* ds_name; |
| 261 | switch (commons_section_type) |
| 262 | { |
| 263 | case COMMONS_NORMAL: |
| 264 | name = ".bss"; |
| 265 | ds_name = "** common"; |
| 266 | break; |
| 267 | case COMMONS_TLS: |
| 268 | flags |= elfcpp::SHF_TLS; |
| 269 | name = ".tbss"; |
| 270 | ds_name = "** tls common"; |
| 271 | break; |
| 272 | case COMMONS_SMALL: |
| 273 | flags |= parameters->target().small_common_section_flags(); |
| 274 | name = ".sbss"; |
| 275 | ds_name = "** small common"; |
| 276 | break; |
| 277 | case COMMONS_LARGE: |
| 278 | flags |= parameters->target().large_common_section_flags(); |
| 279 | name = ".lbss"; |
| 280 | ds_name = "** large common"; |
| 281 | break; |
| 282 | default: |
| 283 | gold_unreachable(); |
| 284 | } |
| 285 | |
| 286 | Output_data_space* poc; |
| 287 | Output_section* os; |
| 288 | |
| 289 | if (!parameters->incremental_update()) |
| 290 | { |
| 291 | poc = new Output_data_space(addralign, ds_name); |
| 292 | os = layout->add_output_section_data(name, elfcpp::SHT_NOBITS, flags, |
| 293 | poc, ORDER_INVALID, false); |
| 294 | } |
| 295 | else |
| 296 | { |
| 297 | // When doing an incremental update, we need to allocate each common |
| 298 | // directly from the output section's free list. |
| 299 | poc = NULL; |
| 300 | os = layout->find_output_section(name); |
| 301 | } |
| 302 | |
| 303 | if (os != NULL) |
| 304 | { |
| 305 | if (commons_section_type == COMMONS_SMALL) |
| 306 | os->set_is_small_section(); |
| 307 | else if (commons_section_type == COMMONS_LARGE) |
| 308 | os->set_is_large_section(); |
| 309 | } |
| 310 | |
| 311 | // Allocate them all. |
| 312 | |
| 313 | off_t off = 0; |
| 314 | for (Commons_type::iterator p = commons->begin(); |
| 315 | p != commons->end(); |
| 316 | ++p) |
| 317 | { |
| 318 | Symbol* sym = *p; |
| 319 | if (sym == NULL) |
| 320 | break; |
| 321 | |
| 322 | // Because we followed forwarding symbols above, but we didn't |
| 323 | // do it reliably before adding symbols to the list, it is |
| 324 | // possible for us to have the same symbol on the list twice. |
| 325 | // This can happen in the horrible case where a program defines |
| 326 | // a common symbol with the same name as a versioned libc |
| 327 | // symbol. That will show up here as a symbol which has already |
| 328 | // been allocated and is therefore no longer a common symbol. |
| 329 | if (!sym->is_common()) |
| 330 | continue; |
| 331 | |
| 332 | Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); |
| 333 | |
| 334 | // Record the symbol in the map file now, before we change its |
| 335 | // value. Pass the size in separately so that we don't have to |
| 336 | // templatize the map code, which is not performance sensitive. |
| 337 | if (mapfile != NULL) |
| 338 | mapfile->report_allocate_common(sym, ssym->symsize()); |
| 339 | |
| 340 | if (poc != NULL) |
| 341 | { |
| 342 | off = align_address(off, ssym->value()); |
| 343 | ssym->allocate_common(poc, off); |
| 344 | off += ssym->symsize(); |
| 345 | } |
| 346 | else |
| 347 | { |
| 348 | // For an incremental update, allocate from the free list. |
| 349 | off = os->allocate(ssym->symsize(), ssym->value()); |
| 350 | if (off == -1) |
| 351 | gold_fallback(_("out of patch space in section %s; " |
| 352 | "relink with --incremental-full"), |
| 353 | os->name()); |
| 354 | ssym->allocate_common(os, off); |
| 355 | } |
| 356 | } |
| 357 | |
| 358 | if (poc != NULL) |
| 359 | poc->set_current_data_size(off); |
| 360 | |
| 361 | commons->clear(); |
| 362 | } |
| 363 | |
| 364 | } // End namespace gold. |