1 // common.cc -- handle common symbols for gold 2 3 // Copyright 2006, 2007, 2008 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 need a lock on the 40 // symbol table. 41 42 Task_token* 43 Allocate_commons_task::is_runnable() 44 { 45 if (!this->symtab_lock_->is_writable()) 46 return this->symtab_lock_; 47 return NULL; 48 } 49 50 // Return the locks we hold: one on the symbol table, and one blocker. 51 52 void 53 Allocate_commons_task::locks(Task_locker* tl) 54 { 55 tl->add(this, this->blocker_); 56 tl->add(this, this->symtab_lock_); 57 } 58 59 // Allocate the common symbols. 60 61 void 62 Allocate_commons_task::run(Workqueue*) 63 { 64 this->symtab_->allocate_commons(this->layout_, this->mapfile_); 65 } 66 67 // This class is used to sort the common symbol by size. We put the 68 // larger common symbols first. 69 70 template<int size> 71 class Sort_commons 72 { 73 public: 74 Sort_commons(const Symbol_table* symtab) 75 : symtab_(symtab) 76 { } 77 78 bool operator()(const Symbol* a, const Symbol* b) const; 79 80 private: 81 const Symbol_table* symtab_; 82 }; 83 84 template<int size> 85 bool 86 Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const 87 { 88 if (pa == NULL) 89 return false; 90 if (pb == NULL) 91 return true; 92 93 const Symbol_table* symtab = this->symtab_; 94 const Sized_symbol<size>* psa = symtab->get_sized_symbol<size>(pa); 95 const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb); 96 97 // Sort by largest size first. 98 typename Sized_symbol<size>::Size_type sa = psa->symsize(); 99 typename Sized_symbol<size>::Size_type sb = psb->symsize(); 100 if (sa < sb) 101 return false; 102 else if (sb < sa) 103 return true; 104 105 // When the symbols are the same size, we sort them by alignment, 106 // largest alignment first. 107 typename Sized_symbol<size>::Value_type va = psa->value(); 108 typename Sized_symbol<size>::Value_type vb = psb->value(); 109 if (va < vb) 110 return false; 111 else if (vb < va) 112 return true; 113 114 // Otherwise we stabilize the sort by sorting by name. 115 return strcmp(psa->name(), psb->name()) < 0; 116 } 117 118 // Allocate the common symbols. 119 120 void 121 Symbol_table::allocate_commons(Layout* layout, Mapfile* mapfile) 122 { 123 if (parameters->target().get_size() == 32) 124 { 125 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 126 this->do_allocate_commons<32>(layout, mapfile); 127 #else 128 gold_unreachable(); 129 #endif 130 } 131 else if (parameters->target().get_size() == 64) 132 { 133 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 134 this->do_allocate_commons<64>(layout, mapfile); 135 #else 136 gold_unreachable(); 137 #endif 138 } 139 else 140 gold_unreachable(); 141 } 142 143 // Allocated the common symbols, sized version. 144 145 template<int size> 146 void 147 Symbol_table::do_allocate_commons(Layout* layout, Mapfile* mapfile) 148 { 149 this->do_allocate_commons_list<size>(layout, false, &this->commons_, 150 mapfile); 151 this->do_allocate_commons_list<size>(layout, true, &this->tls_commons_, 152 mapfile); 153 } 154 155 // Allocate the common symbols in a list. IS_TLS indicates whether 156 // these are TLS common symbols. 157 158 template<int size> 159 void 160 Symbol_table::do_allocate_commons_list(Layout* layout, bool is_tls, 161 Commons_type* commons, 162 Mapfile* mapfile) 163 { 164 typedef typename Sized_symbol<size>::Value_type Value_type; 165 typedef typename Sized_symbol<size>::Size_type Size_type; 166 167 // We've kept a list of all the common symbols. But the symbol may 168 // have been resolved to a defined symbol by now. And it may be a 169 // forwarder. First remove all non-common symbols. 170 bool any = false; 171 uint64_t addralign = 0; 172 for (Commons_type::iterator p = commons->begin(); 173 p != commons->end(); 174 ++p) 175 { 176 Symbol* sym = *p; 177 if (sym->is_forwarder()) 178 { 179 sym = this->resolve_forwards(sym); 180 *p = sym; 181 } 182 if (!sym->is_common()) 183 *p = NULL; 184 else 185 { 186 any = true; 187 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 188 if (ssym->value() > addralign) 189 addralign = ssym->value(); 190 } 191 } 192 if (!any) 193 return; 194 195 // Sort the common symbols by size, so that they pack better into 196 // memory. 197 std::sort(commons->begin(), commons->end(), 198 Sort_commons<size>(this)); 199 200 // Place them in a newly allocated BSS section. 201 202 Output_data_space *poc = new Output_data_space(addralign, 203 (is_tls 204 ? "** tls common" 205 : "** common")); 206 207 const char* name = ".bss"; 208 elfcpp::Elf_Xword flags = elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC; 209 if (is_tls) 210 { 211 name = ".tbss"; 212 flags |= elfcpp::SHF_TLS; 213 } 214 layout->add_output_section_data(name, elfcpp::SHT_NOBITS, flags, poc); 215 216 // Allocate them all. 217 218 off_t off = 0; 219 for (Commons_type::iterator p = commons->begin(); 220 p != commons->end(); 221 ++p) 222 { 223 Symbol* sym = *p; 224 if (sym == NULL) 225 break; 226 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 227 228 // Record the symbol in the map file now, before we change its 229 // value. Pass the size in separately so that we don't have to 230 // templatize the map code, which is not performance sensitive. 231 if (mapfile != NULL) 232 mapfile->report_allocate_common(sym, ssym->symsize()); 233 234 off = align_address(off, ssym->value()); 235 ssym->allocate_common(poc, off); 236 off += ssym->symsize(); 237 } 238 239 poc->set_current_data_size(off); 240 241 commons->clear(); 242 } 243 244 } // End namespace gold. 245