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// common.cc -- handle common symbols for gold
// Copyright (C) 2006-2021 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)
{
// 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.