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365 lines
9.6 KiB
C++
365 lines
9.6 KiB
C++
// common.cc -- handle common symbols for gold
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// Copyright (C) 2006-2014 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#include "gold.h"
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#include <algorithm>
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#include "workqueue.h"
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#include "mapfile.h"
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#include "layout.h"
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#include "output.h"
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#include "symtab.h"
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#include "common.h"
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namespace gold
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{
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// Allocate_commons_task methods.
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// This task allocates the common symbols. We arrange to run it
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// before anything else which needs to access the symbol table.
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Task_token*
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Allocate_commons_task::is_runnable()
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{
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return NULL;
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}
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// Release a blocker.
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void
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Allocate_commons_task::locks(Task_locker* tl)
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{
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tl->add(this, this->blocker_);
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}
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// Allocate the common symbols.
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void
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Allocate_commons_task::run(Workqueue*)
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{
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this->symtab_->allocate_commons(this->layout_, this->mapfile_);
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}
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// This class is used to sort the common symbol. We normally put the
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// larger common symbols first. This can be changed by using
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// --sort-commons, which tells the linker to sort by alignment.
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template<int size>
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class Sort_commons
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{
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public:
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Sort_commons(const Symbol_table* symtab,
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Symbol_table::Sort_commons_order sort_order)
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: symtab_(symtab), sort_order_(sort_order)
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{ }
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bool operator()(const Symbol* a, const Symbol* b) const;
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private:
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// The symbol table.
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const Symbol_table* symtab_;
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// How to sort.
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Symbol_table::Sort_commons_order sort_order_;
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};
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template<int size>
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bool
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Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const
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{
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if (pa == NULL)
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return false;
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if (pb == NULL)
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return true;
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const Symbol_table* symtab = this->symtab_;
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const Sized_symbol<size>* psa = symtab->get_sized_symbol<size>(pa);
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const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb);
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// The size.
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typename Sized_symbol<size>::Size_type sa = psa->symsize();
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typename Sized_symbol<size>::Size_type sb = psb->symsize();
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// The alignment.
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typename Sized_symbol<size>::Value_type aa = psa->value();
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typename Sized_symbol<size>::Value_type ab = psb->value();
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if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_DESCENDING)
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{
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if (aa < ab)
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return false;
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else if (ab < aa)
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return true;
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}
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else if (this->sort_order_
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== Symbol_table::SORT_COMMONS_BY_ALIGNMENT_ASCENDING)
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{
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if (aa < ab)
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return true;
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else if (ab < aa)
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return false;
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}
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else
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gold_assert(this->sort_order_
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== Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING);
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// Sort by descending size.
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if (sa < sb)
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return false;
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else if (sb < sa)
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return true;
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if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING)
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{
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// When the symbols are the same size, we sort them by
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// alignment, largest alignment first.
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if (aa < ab)
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return false;
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else if (ab < aa)
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return true;
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}
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// Otherwise we stabilize the sort by sorting by name.
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return strcmp(psa->name(), psb->name()) < 0;
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}
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// Allocate the common symbols.
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void
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Symbol_table::allocate_commons(Layout* layout, Mapfile* mapfile)
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{
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Sort_commons_order sort_order;
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if (!parameters->options().user_set_sort_common())
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sort_order = SORT_COMMONS_BY_SIZE_DESCENDING;
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else
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{
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const char* order = parameters->options().sort_common();
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if (*order == '\0' || strcmp(order, "descending") == 0)
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sort_order = SORT_COMMONS_BY_ALIGNMENT_DESCENDING;
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else if (strcmp(order, "ascending") == 0)
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sort_order = SORT_COMMONS_BY_ALIGNMENT_ASCENDING;
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else
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{
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gold_error("invalid --sort-common argument: %s", order);
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sort_order = SORT_COMMONS_BY_SIZE_DESCENDING;
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}
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}
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if (parameters->target().get_size() == 32)
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{
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#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
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this->do_allocate_commons<32>(layout, mapfile, sort_order);
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#else
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gold_unreachable();
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#endif
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}
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else if (parameters->target().get_size() == 64)
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{
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#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
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this->do_allocate_commons<64>(layout, mapfile, sort_order);
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#else
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gold_unreachable();
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#endif
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}
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else
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gold_unreachable();
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}
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// Allocated the common symbols, sized version.
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template<int size>
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void
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Symbol_table::do_allocate_commons(Layout* layout, Mapfile* mapfile,
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Sort_commons_order sort_order)
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{
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if (!this->commons_.empty())
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this->do_allocate_commons_list<size>(layout, COMMONS_NORMAL,
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&this->commons_, mapfile,
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sort_order);
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if (!this->tls_commons_.empty())
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this->do_allocate_commons_list<size>(layout, COMMONS_TLS,
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&this->tls_commons_, mapfile,
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sort_order);
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if (!this->small_commons_.empty())
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this->do_allocate_commons_list<size>(layout, COMMONS_SMALL,
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&this->small_commons_, mapfile,
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sort_order);
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if (!this->large_commons_.empty())
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this->do_allocate_commons_list<size>(layout, COMMONS_LARGE,
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&this->large_commons_, mapfile,
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sort_order);
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}
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// Allocate the common symbols in a list. IS_TLS indicates whether
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// these are TLS common symbols.
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template<int size>
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void
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Symbol_table::do_allocate_commons_list(
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Layout* layout,
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Commons_section_type commons_section_type,
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Commons_type* commons,
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Mapfile* mapfile,
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Sort_commons_order sort_order)
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{
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// We've kept a list of all the common symbols. But the symbol may
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// have been resolved to a defined symbol by now. And it may be a
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// forwarder. First remove all non-common symbols.
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bool any = false;
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uint64_t addralign = 0;
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for (Commons_type::iterator p = commons->begin();
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p != commons->end();
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++p)
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{
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Symbol* sym = *p;
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if (sym->is_forwarder())
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{
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sym = this->resolve_forwards(sym);
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*p = sym;
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}
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if (!sym->is_common())
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*p = NULL;
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else
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{
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any = true;
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Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
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if (ssym->value() > addralign)
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addralign = ssym->value();
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}
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}
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if (!any)
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return;
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// Sort the common symbols.
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std::sort(commons->begin(), commons->end(),
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Sort_commons<size>(this, sort_order));
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// Place them in a newly allocated BSS section.
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elfcpp::Elf_Xword flags = elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC;
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const char* name;
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const char* ds_name;
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switch (commons_section_type)
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{
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case COMMONS_NORMAL:
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name = ".bss";
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ds_name = "** common";
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break;
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case COMMONS_TLS:
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flags |= elfcpp::SHF_TLS;
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name = ".tbss";
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ds_name = "** tls common";
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break;
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case COMMONS_SMALL:
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flags |= parameters->target().small_common_section_flags();
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name = ".sbss";
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ds_name = "** small common";
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break;
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case COMMONS_LARGE:
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flags |= parameters->target().large_common_section_flags();
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name = ".lbss";
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ds_name = "** large common";
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break;
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default:
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gold_unreachable();
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}
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Output_data_space* poc;
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Output_section* os;
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if (!parameters->incremental_update())
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{
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poc = new Output_data_space(addralign, ds_name);
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os = layout->add_output_section_data(name, elfcpp::SHT_NOBITS, flags,
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poc, ORDER_INVALID, false);
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}
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else
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{
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// When doing an incremental update, we need to allocate each common
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// directly from the output section's free list.
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poc = NULL;
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os = layout->find_output_section(name);
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}
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if (os != NULL)
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{
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if (commons_section_type == COMMONS_SMALL)
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os->set_is_small_section();
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else if (commons_section_type == COMMONS_LARGE)
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os->set_is_large_section();
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}
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// Allocate them all.
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off_t off = 0;
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for (Commons_type::iterator p = commons->begin();
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p != commons->end();
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++p)
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{
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Symbol* sym = *p;
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if (sym == NULL)
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break;
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// Because we followed forwarding symbols above, but we didn't
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// do it reliably before adding symbols to the list, it is
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// possible for us to have the same symbol on the list twice.
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// This can happen in the horrible case where a program defines
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// a common symbol with the same name as a versioned libc
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// symbol. That will show up here as a symbol which has already
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// been allocated and is therefore no longer a common symbol.
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if (!sym->is_common())
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continue;
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Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
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// Record the symbol in the map file now, before we change its
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// value. Pass the size in separately so that we don't have to
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// templatize the map code, which is not performance sensitive.
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if (mapfile != NULL)
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mapfile->report_allocate_common(sym, ssym->symsize());
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if (poc != NULL)
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{
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off = align_address(off, ssym->value());
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ssym->allocate_common(poc, off);
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off += ssym->symsize();
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}
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else
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{
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// For an incremental update, allocate from the free list.
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off = os->allocate(ssym->symsize(), ssym->value());
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if (off == -1)
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gold_fallback(_("out of patch space in section %s; "
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"relink with --incremental-full"),
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os->name());
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ssym->allocate_common(os, off);
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}
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}
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if (poc != NULL)
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poc->set_current_data_size(off);
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commons->clear();
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}
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} // End namespace gold.
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