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binutils-gdb/gold/resolve.cc
Ian Lance Taylor 6cb15b7f89 Add licensing text to every source file.
2007-09-22 21:02:10 +00:00

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// resolve.cc -- symbol resolution for gold
// Copyright 2006, 2007 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 "elfcpp.h"
#include "target.h"
#include "object.h"
#include "symtab.h"
namespace gold
{
// Symbol methods used in this file.
// Override the fields in Symbol.
template<int size, bool big_endian>
void
Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
gold_assert(this->source_ == FROM_OBJECT);
this->u_.from_object.object = object;
if (version != NULL && this->version() != version)
{
gold_assert(this->version() == NULL);
this->version_ = version;
}
// FIXME: Handle SHN_XINDEX.
this->u_.from_object.shndx = sym.get_st_shndx();
this->type_ = sym.get_st_type();
this->binding_ = sym.get_st_bind();
this->visibility_ = sym.get_st_visibility();
this->nonvis_ = sym.get_st_nonvis();
if (object->is_dynamic())
this->in_dyn_ = true;
else
this->in_reg_ = true;
}
// Override the fields in Sized_symbol.
template<int size>
template<bool big_endian>
void
Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
this->override_base(sym, object, version);
this->value_ = sym.get_st_value();
this->symsize_ = sym.get_st_size();
}
// The resolve functions build a little code for each symbol.
// Bit 0: 0 for global, 1 for weak.
// Bit 1: 0 for regular object, 1 for shared object
// Bits 2-3: 0 for normal, 1 for undefined, 2 for common
// This gives us values from 0 to 11.
static const int global_or_weak_shift = 0;
static const unsigned int global_flag = 0 << global_or_weak_shift;
static const unsigned int weak_flag = 1 << global_or_weak_shift;
static const int regular_or_dynamic_shift = 1;
static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
static const int def_undef_or_common_shift = 2;
static const unsigned int def_flag = 0 << def_undef_or_common_shift;
static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
static const unsigned int common_flag = 2 << def_undef_or_common_shift;
// Resolve a symbol. This is called the second and subsequent times
// we see a symbol. TO is the pre-existing symbol. SYM is the new
// symbol, seen in OBJECT. VERSION of the version of SYM.
template<int size, bool big_endian>
void
Symbol_table::resolve(Sized_symbol<size>* to,
const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
if (object->target()->has_resolve())
{
Sized_target<size, big_endian>* sized_target;
sized_target = object->sized_target
SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
sized_target->resolve(to, sym, object, version);
return;
}
if (!object->is_dynamic())
{
// Record that we've seen this symbol in a regular object.
to->set_in_reg();
}
else
{
// Record that we've seen this symbol in a dynamic object.
to->set_in_dyn();
}
unsigned int frombits;
switch (sym.get_st_bind())
{
case elfcpp::STB_GLOBAL:
frombits = global_flag;
break;
case elfcpp::STB_WEAK:
frombits = weak_flag;
break;
case elfcpp::STB_LOCAL:
fprintf(stderr,
_("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
program_name, object->name().c_str(), to->name());
gold_exit(false);
default:
fprintf(stderr,
_("%s: %s: unsupported symbol binding %d for symbol %s\n"),
program_name, object->name().c_str(),
static_cast<int>(sym.get_st_bind()), to->name());
gold_exit(false);
}
if (!object->is_dynamic())
frombits |= regular_flag;
else
frombits |= dynamic_flag;
switch (sym.get_st_shndx())
{
case elfcpp::SHN_UNDEF:
frombits |= undef_flag;
break;
case elfcpp::SHN_COMMON:
frombits |= common_flag;
break;
default:
if (sym.get_st_type() == elfcpp::STT_COMMON)
frombits |= common_flag;
else
frombits |= def_flag;
break;
}
bool adjust_common_sizes;
if (Symbol_table::should_override(to, frombits, &adjust_common_sizes))
{
typename Sized_symbol<size>::Size_type tosize = to->symsize();
to->override(sym, object, version);
if (adjust_common_sizes && tosize > to->symsize())
to->set_symsize(tosize);
}
else
{
if (adjust_common_sizes && sym.get_st_size() > to->symsize())
to->set_symsize(sym.get_st_size());
}
}
// Handle the core of symbol resolution. This is called with the
// existing symbol, TO, and a bitflag describing the new symbol. This
// returns true if we should override the existing symbol with the new
// one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to
// true if we should set the symbol size to the maximum of the TO and
// FROM sizes. It handles error conditions.
bool
Symbol_table::should_override(const Symbol* to, unsigned int frombits,
bool* adjust_common_sizes)
{
*adjust_common_sizes = false;
unsigned int tobits;
switch (to->binding())
{
case elfcpp::STB_GLOBAL:
tobits = global_flag;
break;
case elfcpp::STB_WEAK:
tobits = weak_flag;
break;
case elfcpp::STB_LOCAL:
// We should only see externally visible symbols in the symbol
// table.
gold_unreachable();
default:
// Any target which wants to handle STB_LOOS, etc., needs to
// define a resolve method.
gold_unreachable();
}
if (to->source() == Symbol::FROM_OBJECT
&& to->object()->is_dynamic())
tobits |= dynamic_flag;
else
tobits |= regular_flag;
switch (to->shndx())
{
case elfcpp::SHN_UNDEF:
tobits |= undef_flag;
break;
case elfcpp::SHN_COMMON:
tobits |= common_flag;
break;
default:
if (to->type() == elfcpp::STT_COMMON)
tobits |= common_flag;
else
tobits |= def_flag;
break;
}
// FIXME: Warn if either but not both of TO and SYM are STT_TLS.
// We use a giant switch table for symbol resolution. This code is
// unwieldy, but: 1) it is efficient; 2) we definitely handle all
// cases; 3) it is easy to change the handling of a particular case.
// The alternative would be a series of conditionals, but it is easy
// to get the ordering wrong. This could also be done as a table,
// but that is no easier to understand than this large switch
// statement.
// These are the values generated by the bit codes.
enum
{
DEF = global_flag | regular_flag | def_flag,
WEAK_DEF = weak_flag | regular_flag | def_flag,
DYN_DEF = global_flag | dynamic_flag | def_flag,
DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag,
UNDEF = global_flag | regular_flag | undef_flag,
WEAK_UNDEF = weak_flag | regular_flag | undef_flag,
DYN_UNDEF = global_flag | dynamic_flag | undef_flag,
DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag,
COMMON = global_flag | regular_flag | common_flag,
WEAK_COMMON = weak_flag | regular_flag | common_flag,
DYN_COMMON = global_flag | dynamic_flag | common_flag,
DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag
};
switch (tobits * 16 + frombits)
{
case DEF * 16 + DEF:
// Two definitions of the same symbol.
fprintf(stderr, "%s: multiple definition of %s\n",
program_name, to->name());
// FIXME: Report locations. Record that we have seen an error.
return false;
case WEAK_DEF * 16 + DEF:
// We've seen a weak definition, and now we see a strong
// definition. In the original SVR4 linker, this was treated as
// a multiple definition error. In the Solaris linker and the
// GNU linker, a weak definition followed by a regular
// definition causes the weak definition to be overridden. We
// are currently compatible with the GNU linker. In the future
// we should add a target specific option to change this.
// FIXME.
return true;
case DYN_DEF * 16 + DEF:
case DYN_WEAK_DEF * 16 + DEF:
// We've seen a definition in a dynamic object, and now we see a
// definition in a regular object. The definition in the
// regular object overrides the definition in the dynamic
// object.
return true;
case UNDEF * 16 + DEF:
case WEAK_UNDEF * 16 + DEF:
case DYN_UNDEF * 16 + DEF:
case DYN_WEAK_UNDEF * 16 + DEF:
// We've seen an undefined reference, and now we see a
// definition. We use the definition.
return true;
case COMMON * 16 + DEF:
case WEAK_COMMON * 16 + DEF:
case DYN_COMMON * 16 + DEF:
case DYN_WEAK_COMMON * 16 + DEF:
// We've seen a common symbol and now we see a definition. The
// definition overrides. FIXME: We should optionally issue, version a
// warning.
return true;
case DEF * 16 + WEAK_DEF:
case WEAK_DEF * 16 + WEAK_DEF:
// We've seen a definition and now we see a weak definition. We
// ignore the new weak definition.
return false;
case DYN_DEF * 16 + WEAK_DEF:
case DYN_WEAK_DEF * 16 + WEAK_DEF:
// We've seen a dynamic definition and now we see a regular weak
// definition. The regular weak definition overrides.
return true;
case UNDEF * 16 + WEAK_DEF:
case WEAK_UNDEF * 16 + WEAK_DEF:
case DYN_UNDEF * 16 + WEAK_DEF:
case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
// A weak definition of a currently undefined symbol.
return true;
case COMMON * 16 + WEAK_DEF:
case WEAK_COMMON * 16 + WEAK_DEF:
// A weak definition does not override a common definition.
return false;
case DYN_COMMON * 16 + WEAK_DEF:
case DYN_WEAK_COMMON * 16 + WEAK_DEF:
// A weak definition does override a definition in a dynamic
// object. FIXME: We should optionally issue a warning.
return true;
case DEF * 16 + DYN_DEF:
case WEAK_DEF * 16 + DYN_DEF:
case DYN_DEF * 16 + DYN_DEF:
case DYN_WEAK_DEF * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a definition.
return false;
case UNDEF * 16 + DYN_DEF:
case WEAK_UNDEF * 16 + DYN_DEF:
case DYN_UNDEF * 16 + DYN_DEF:
case DYN_WEAK_UNDEF * 16 + DYN_DEF:
// Use a dynamic definition if we have a reference.
return true;
case COMMON * 16 + DYN_DEF:
case WEAK_COMMON * 16 + DYN_DEF:
case DYN_COMMON * 16 + DYN_DEF:
case DYN_WEAK_COMMON * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a common
// definition.
return false;
case DEF * 16 + DYN_WEAK_DEF:
case WEAK_DEF * 16 + DYN_WEAK_DEF:
case DYN_DEF * 16 + DYN_WEAK_DEF:
case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
// Ignore a weak dynamic definition if we already have a
// definition.
return false;
case UNDEF * 16 + DYN_WEAK_DEF:
case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
case DYN_UNDEF * 16 + DYN_WEAK_DEF:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
// Use a weak dynamic definition if we have a reference.
return true;
case COMMON * 16 + DYN_WEAK_DEF:
case WEAK_COMMON * 16 + DYN_WEAK_DEF:
case DYN_COMMON * 16 + DYN_WEAK_DEF:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
// Ignore a weak dynamic definition if we already have a common
// definition.
return false;
case DEF * 16 + UNDEF:
case WEAK_DEF * 16 + UNDEF:
case DYN_DEF * 16 + UNDEF:
case DYN_WEAK_DEF * 16 + UNDEF:
case UNDEF * 16 + UNDEF:
// A new undefined reference tells us nothing.
return false;
case WEAK_UNDEF * 16 + UNDEF:
case DYN_UNDEF * 16 + UNDEF:
case DYN_WEAK_UNDEF * 16 + UNDEF:
// A strong undef overrides a dynamic or weak undef.
return true;
case COMMON * 16 + UNDEF:
case WEAK_COMMON * 16 + UNDEF:
case DYN_COMMON * 16 + UNDEF:
case DYN_WEAK_COMMON * 16 + UNDEF:
// A new undefined reference tells us nothing.
return false;
case DEF * 16 + WEAK_UNDEF:
case WEAK_DEF * 16 + WEAK_UNDEF:
case DYN_DEF * 16 + WEAK_UNDEF:
case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
case UNDEF * 16 + WEAK_UNDEF:
case WEAK_UNDEF * 16 + WEAK_UNDEF:
case DYN_UNDEF * 16 + WEAK_UNDEF:
case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
case COMMON * 16 + WEAK_UNDEF:
case WEAK_COMMON * 16 + WEAK_UNDEF:
case DYN_COMMON * 16 + WEAK_UNDEF:
case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
// A new weak undefined reference tells us nothing.
return false;
case DEF * 16 + DYN_UNDEF:
case WEAK_DEF * 16 + DYN_UNDEF:
case DYN_DEF * 16 + DYN_UNDEF:
case DYN_WEAK_DEF * 16 + DYN_UNDEF:
case UNDEF * 16 + DYN_UNDEF:
case WEAK_UNDEF * 16 + DYN_UNDEF:
case DYN_UNDEF * 16 + DYN_UNDEF:
case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
case COMMON * 16 + DYN_UNDEF:
case WEAK_COMMON * 16 + DYN_UNDEF:
case DYN_COMMON * 16 + DYN_UNDEF:
case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
// A new dynamic undefined reference tells us nothing.
return false;
case DEF * 16 + DYN_WEAK_UNDEF:
case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
case DYN_DEF * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
case UNDEF * 16 + DYN_WEAK_UNDEF:
case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
case COMMON * 16 + DYN_WEAK_UNDEF:
case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
// A new weak dynamic undefined reference tells us nothing.
return false;
case DEF * 16 + COMMON:
// A common symbol does not override a definition.
return false;
case WEAK_DEF * 16 + COMMON:
case DYN_DEF * 16 + COMMON:
case DYN_WEAK_DEF * 16 + COMMON:
// A common symbol does override a weak definition or a dynamic
// definition.
return true;
case UNDEF * 16 + COMMON:
case WEAK_UNDEF * 16 + COMMON:
case DYN_UNDEF * 16 + COMMON:
case DYN_WEAK_UNDEF * 16 + COMMON:
// A common symbol is a definition for a reference.
return true;
case COMMON * 16 + COMMON:
// Set the size to the maximum.
*adjust_common_sizes = true;
return false;
case WEAK_COMMON * 16 + COMMON:
// I'm not sure just what a weak common symbol means, but
// presumably it can be overridden by a regular common symbol.
return true;
case DYN_COMMON * 16 + COMMON:
case DYN_WEAK_COMMON * 16 + COMMON:
// Use the real common symbol, but adjust the size if necessary.
*adjust_common_sizes = true;
return true;
case DEF * 16 + WEAK_COMMON:
case WEAK_DEF * 16 + WEAK_COMMON:
case DYN_DEF * 16 + WEAK_COMMON:
case DYN_WEAK_DEF * 16 + WEAK_COMMON:
// Whatever a weak common symbol is, it won't override a
// definition.
return false;
case UNDEF * 16 + WEAK_COMMON:
case WEAK_UNDEF * 16 + WEAK_COMMON:
case DYN_UNDEF * 16 + WEAK_COMMON:
case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
// A weak common symbol is better than an undefined symbol.
return true;
case COMMON * 16 + WEAK_COMMON:
case WEAK_COMMON * 16 + WEAK_COMMON:
case DYN_COMMON * 16 + WEAK_COMMON:
case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
// Ignore a weak common symbol in the presence of a real common
// symbol.
return false;
case DEF * 16 + DYN_COMMON:
case WEAK_DEF * 16 + DYN_COMMON:
case DYN_DEF * 16 + DYN_COMMON:
case DYN_WEAK_DEF * 16 + DYN_COMMON:
// Ignore a dynamic common symbol in the presence of a
// definition.
return false;
case UNDEF * 16 + DYN_COMMON:
case WEAK_UNDEF * 16 + DYN_COMMON:
case DYN_UNDEF * 16 + DYN_COMMON:
case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
// A dynamic common symbol is a definition of sorts.
return true;
case COMMON * 16 + DYN_COMMON:
case WEAK_COMMON * 16 + DYN_COMMON:
case DYN_COMMON * 16 + DYN_COMMON:
case DYN_WEAK_COMMON * 16 + DYN_COMMON:
// Set the size to the maximum.
*adjust_common_sizes = true;
return false;
case DEF * 16 + DYN_WEAK_COMMON:
case WEAK_DEF * 16 + DYN_WEAK_COMMON:
case DYN_DEF * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
// A common symbol is ignored in the face of a definition.
return false;
case UNDEF * 16 + DYN_WEAK_COMMON:
case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
// I guess a weak common symbol is better than a definition.
return true;
case COMMON * 16 + DYN_WEAK_COMMON:
case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
case DYN_COMMON * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
// Set the size to the maximum.
*adjust_common_sizes = true;
return false;
default:
gold_unreachable();
}
}
// A special case of should_override which is only called for a strong
// defined symbol from a regular object file. This is used when
// defining special symbols.
bool
Symbol_table::should_override_with_special(const Symbol* to)
{
bool adjust_common_sizes;
unsigned int frombits = global_flag | regular_flag | def_flag;
bool ret = Symbol_table::should_override(to, frombits, &adjust_common_sizes);
gold_assert(!adjust_common_sizes);
return ret;
}
// Override symbol base with a special symbol.
void
Symbol::override_base_with_special(const Symbol* from)
{
this->source_ = from->source_;
switch (from->source_)
{
case FROM_OBJECT:
this->u_.from_object = from->u_.from_object;
break;
case IN_OUTPUT_DATA:
this->u_.in_output_data = from->u_.in_output_data;
break;
case IN_OUTPUT_SEGMENT:
this->u_.in_output_segment = from->u_.in_output_segment;
break;
case CONSTANT:
break;
default:
gold_unreachable();
break;
}
if (from->version_ != NULL && this->version_ != from->version_)
{
gold_assert(this->version_ == NULL);
this->version_ = from->version_;
}
this->type_ = from->type_;
this->binding_ = from->binding_;
this->visibility_ = from->visibility_;
this->nonvis_ = from->nonvis_;
// Special symbols are always considered to be regular symbols.
this->in_reg_ = true;
}
// Override a symbol with a special symbol.
template<int size>
void
Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
{
this->override_base_with_special(from);
this->value_ = from->value_;
this->symsize_ = from->symsize_;
}
// Instantiate the templates we need. We could use the configure
// script to restrict this to only the ones needed for implemented
// targets.
#ifdef HAVE_TARGET_32_LITTLE
template
void
Symbol_table::resolve<32, false>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, false>& sym,
Object* object,
const char* version);
#endif
#ifdef HAVE_TARGET_32_BIG
template
void
Symbol_table::resolve<32, true>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, true>& sym,
Object* object,
const char* version);
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
void
Symbol_table::resolve<64, false>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, false>& sym,
Object* object,
const char* version);
#endif
#ifdef HAVE_TARGET_64_BIG
template
void
Symbol_table::resolve<64, true>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, true>& sym,
Object* object,
const char* version);
#endif
#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
template
void
Sized_symbol<32>::override_with_special(const Sized_symbol<32>*);
#endif
#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
template
void
Sized_symbol<64>::override_with_special(const Sized_symbol<64>*);
#endif
} // End namespace gold.
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