// common.cc -- handle common symbols for gold // Copyright 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. // Written by Ian Lance Taylor <iant@google.com>. // This file is part of gold. // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, // MA 02110-1301, USA. #include "gold.h" #include <algorithm> #include "workqueue.h" #include "mapfile.h" #include "layout.h" #include "output.h" #include "symtab.h" #include "common.h" namespace gold { // Allocate_commons_task methods. // This task allocates the common symbols. We arrange to run it // before anything else which needs to access the symbol table. Task_token* Allocate_commons_task::is_runnable() { return NULL; } // Release a blocker. void Allocate_commons_task::locks(Task_locker* tl) { tl->add(this, this->blocker_); } // Allocate the common symbols. void Allocate_commons_task::run(Workqueue*) { this->symtab_->allocate_commons(this->layout_, this->mapfile_); } // This class is used to sort the common symbol. We normally put the // larger common symbols first. This can be changed by using // --sort-commons, which tells the linker to sort by alignment. template<int size> class Sort_commons { public: Sort_commons(const Symbol_table* symtab, Symbol_table::Sort_commons_order sort_order) : symtab_(symtab), sort_order_(sort_order) { } bool operator()(const Symbol* a, const Symbol* b) const; private: // The symbol table. const Symbol_table* symtab_; // How to sort. Symbol_table::Sort_commons_order sort_order_; }; template<int size> bool Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const { if (pa == NULL) return false; if (pb == NULL) return true; const Symbol_table* symtab = this->symtab_; const Sized_symbol<size>* psa = symtab->get_sized_symbol<size>(pa); const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb); // The size. typename Sized_symbol<size>::Size_type sa = psa->symsize(); typename Sized_symbol<size>::Size_type sb = psb->symsize(); // The alignment. typename Sized_symbol<size>::Value_type aa = psa->value(); typename Sized_symbol<size>::Value_type ab = psb->value(); if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_DESCENDING) { if (aa < ab) return false; else if (ab < aa) return true; } else if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_ASCENDING) { if (aa < ab) return true; else if (ab < aa) return false; } else gold_assert(this->sort_order_ == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING); // Sort by descending size. if (sa < sb) return false; else if (sb < sa) return true; if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING) { // When the symbols are the same size, we sort them by // alignment, largest alignment first. if (aa < ab) return false; else if (ab < aa) return true; } // Otherwise we stabilize the sort by sorting by name. return strcmp(psa->name(), psb->name()) < 0; } // Allocate the common symbols. void Symbol_table::allocate_commons(Layout* layout, Mapfile* mapfile) { Sort_commons_order sort_order; if (!parameters->options().user_set_sort_common()) sort_order = SORT_COMMONS_BY_SIZE_DESCENDING; else { const char* order = parameters->options().sort_common(); if (*order == '\0' || strcmp(order, "descending") == 0) sort_order = SORT_COMMONS_BY_ALIGNMENT_DESCENDING; else if (strcmp(order, "ascending") == 0) sort_order = SORT_COMMONS_BY_ALIGNMENT_ASCENDING; else { gold_error("invalid --sort-common argument: %s", order); sort_order = SORT_COMMONS_BY_SIZE_DESCENDING; } } if (parameters->target().get_size() == 32) { #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) this->do_allocate_commons<32>(layout, mapfile, sort_order); #else gold_unreachable(); #endif } else if (parameters->target().get_size() == 64) { #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) this->do_allocate_commons<64>(layout, mapfile, sort_order); #else gold_unreachable(); #endif } else gold_unreachable(); } // Allocated the common symbols, sized version. template<int size> void Symbol_table::do_allocate_commons(Layout* layout, Mapfile* mapfile, Sort_commons_order sort_order) { if (!this->commons_.empty()) this->do_allocate_commons_list<size>(layout, COMMONS_NORMAL, &this->commons_, mapfile, sort_order); if (!this->tls_commons_.empty()) this->do_allocate_commons_list<size>(layout, COMMONS_TLS, &this->tls_commons_, mapfile, sort_order); if (!this->small_commons_.empty()) this->do_allocate_commons_list<size>(layout, COMMONS_SMALL, &this->small_commons_, mapfile, sort_order); if (!this->large_commons_.empty()) this->do_allocate_commons_list<size>(layout, COMMONS_LARGE, &this->large_commons_, mapfile, sort_order); } // Allocate the common symbols in a list. IS_TLS indicates whether // these are TLS common symbols. template<int size> void Symbol_table::do_allocate_commons_list( Layout* layout, Commons_section_type commons_section_type, Commons_type* commons, Mapfile* mapfile, Sort_commons_order sort_order) { typedef typename Sized_symbol<size>::Value_type Value_type; typedef typename Sized_symbol<size>::Size_type Size_type; // We've kept a list of all the common symbols. But the symbol may // have been resolved to a defined symbol by now. And it may be a // forwarder. First remove all non-common symbols. bool any = false; uint64_t addralign = 0; for (Commons_type::iterator p = commons->begin(); p != commons->end(); ++p) { Symbol* sym = *p; if (sym->is_forwarder()) { sym = this->resolve_forwards(sym); *p = sym; } if (!sym->is_common()) *p = NULL; else { any = true; Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); if (ssym->value() > addralign) addralign = ssym->value(); } } if (!any) return; // Sort the common symbols. std::sort(commons->begin(), commons->end(), Sort_commons<size>(this, sort_order)); // Place them in a newly allocated BSS section. elfcpp::Elf_Xword flags = elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC; const char* name; const char* ds_name; switch (commons_section_type) { case COMMONS_NORMAL: name = ".bss"; ds_name = "** common"; break; case COMMONS_TLS: flags |= elfcpp::SHF_TLS; name = ".tbss"; ds_name = "** tls common"; break; case COMMONS_SMALL: flags |= parameters->target().small_common_section_flags(); name = ".sbss"; ds_name = "** small common"; break; case COMMONS_LARGE: flags |= parameters->target().large_common_section_flags(); name = ".lbss"; ds_name = "** large common"; break; default: gold_unreachable(); } Output_data_space* poc; Output_section* os; if (!parameters->incremental_update()) { poc = new Output_data_space(addralign, ds_name); os = layout->add_output_section_data(name, elfcpp::SHT_NOBITS, flags, poc, ORDER_INVALID, false); } else { // When doing an incremental update, we need to allocate each common // directly from the output section's free list. poc = NULL; os = layout->find_output_section(name); } if (os != NULL) { if (commons_section_type == COMMONS_SMALL) os->set_is_small_section(); else if (commons_section_type == COMMONS_LARGE) os->set_is_large_section(); } // Allocate them all. off_t off = 0; for (Commons_type::iterator p = commons->begin(); p != commons->end(); ++p) { Symbol* sym = *p; if (sym == NULL) break; // Because we followed forwarding symbols above, but we didn't // do it reliably before adding symbols to the list, it is // possible for us to have the same symbol on the list twice. // This can happen in the horrible case where a program defines // a common symbol with the same name as a versioned libc // symbol. That will show up here as a symbol which has already // been allocated and is therefore no longer a common symbol. if (!sym->is_common()) continue; Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); // Record the symbol in the map file now, before we change its // value. Pass the size in separately so that we don't have to // templatize the map code, which is not performance sensitive. if (mapfile != NULL) mapfile->report_allocate_common(sym, ssym->symsize()); if (poc != NULL) { off = align_address(off, ssym->value()); ssym->allocate_common(poc, off); off += ssym->symsize(); } else { // For an incremental update, allocate from the free list. off = os->allocate(ssym->symsize(), ssym->value()); if (off == -1) gold_fallback(_("out of patch space in section %s; " "relink with --incremental-full"), os->name()); ssym->allocate_common(os, off); } } if (poc != NULL) poc->set_current_data_size(off); commons->clear(); } } // End namespace gold.