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binutils-gdb/gold/resolve.cc
Cary Coutant cea6ffbd06 Fix treatment of symbol versions with unused as-needed libraries. 
When we have a weak reference to a symbol defined in an
as-needed library, and that library ends up not-needed, gold
simply clears the version information in the symbol table, even
if the symbol could have been resolved by a needed library later
in the link order. This results in a loss of version information,
which can cause the program to bind to the wrong version at run
time.

This patch lets a dynamic definition override an earlier one if
the earlier one is from a not-needed library, so that we can
retain the version information from the binding to the needed
library. In order to do that, the tracking of needed/not-needed
had to be moved up to symbol resolution time, instead of during
Symbol_table::set_dynsym_indexes().

In cases where we still end up discarding version information,
I've added a warning.

For the original problem report and discussion, see:

https://stackoverflow.com/questions/50751421/undefined-behavior-in-shared-lib-using-libpthread-but-not-having-it-in-elf-as-d

gold/
	* resolve.cc (Symbol_table::resolve): Rename tobinding to
	orig_tobinding.  Call set_is_needed() for objects that resolve
	non-weak references.
	(Symbol_table::should_override): Allow a dynamic definition to
	override an earlier one in a not-needed library.
	* symtab.cc (Symbol_table::set_dynsym_indexes): Remove separate
	processing for as-needed symbols.  Add warning when discarding
	version informatin.
	* testsuite/Makefile.am (weak_as_needed): New test case.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/weak_as_needed.sh: New test script.
	* testsuite/weak_as_needed_a.c: New source file.
	* testsuite/weak_as_needed_b.c: New source file.
	* testsuite/weak_as_needed_b.script: New version script.
	* testsuite/weak_as_needed_c.c: New source file.
	* testsuite/weak_as_needed_c.script: New version script.
2018-06-21 13:54:16 -07:00

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// resolve.cc -- symbol resolution for gold
// Copyright (C) 2006-2018 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"
#include "plugin.h"
namespace gold
{
// Symbol methods used in this file.
// This symbol is being overridden by another symbol whose version is
// VERSION. Update the VERSION_ field accordingly.
inline void
Symbol::override_version(const char* version)
{
if (version == NULL)
{
// This is the case where this symbol is NAME/VERSION, and the
// version was not marked as hidden. That makes it the default
// version, so we create NAME/NULL. Later we see another symbol
// NAME/NULL, and that symbol is overriding this one. In this
// case, since NAME/VERSION is the default, we make NAME/NULL
// override NAME/VERSION as well. They are already the same
// Symbol structure. Setting the VERSION_ field to NULL ensures
// that it will be output with the correct, empty, version.
this->version_ = version;
}
else
{
// This is the case where this symbol is NAME/VERSION_ONE, and
// now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is
// overriding NAME. If VERSION_ONE and VERSION_TWO are
// different, then this can only happen when VERSION_ONE is NULL
// and VERSION_TWO is not hidden.
gold_assert(this->version_ == version || this->version_ == NULL);
this->version_ = version;
}
}
// This symbol is being overidden by another symbol whose visibility
// is VISIBILITY. Updated the VISIBILITY_ field accordingly.
inline void
Symbol::override_visibility(elfcpp::STV visibility)
{
// The rule for combining visibility is that we always choose the
// most constrained visibility. In order of increasing constraint,
// visibility goes PROTECTED, HIDDEN, INTERNAL. This is the reverse
// of the numeric values, so the effect is that we always want the
// smallest non-zero value.
if (visibility != elfcpp::STV_DEFAULT)
{
if (this->visibility_ == elfcpp::STV_DEFAULT)
this->visibility_ = visibility;
else if (this->visibility_ > visibility)
this->visibility_ = visibility;
}
}
// Override the fields in Symbol.
template<int size, bool big_endian>
void
Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
unsigned int st_shndx, bool is_ordinary,
Object* object, const char* version)
{
gold_assert(this->source_ == FROM_OBJECT);
this->u1_.object = object;
this->override_version(version);
this->u2_.shndx = st_shndx;
this->is_ordinary_shndx_ = is_ordinary;
// Don't override st_type from plugin placeholder symbols.
if (object->pluginobj() == NULL)
this->type_ = sym.get_st_type();
this->binding_ = sym.get_st_bind();
this->override_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,
unsigned st_shndx, bool is_ordinary,
Object* object, const char* version)
{
this->override_base(sym, st_shndx, is_ordinary, object, version);
this->value_ = sym.get_st_value();
this->symsize_ = sym.get_st_size();
}
// Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
// VERSION. This handles all aliases of TOSYM.
template<int size, bool big_endian>
void
Symbol_table::override(Sized_symbol<size>* tosym,
const elfcpp::Sym<size, big_endian>& fromsym,
unsigned int st_shndx, bool is_ordinary,
Object* object, const char* version)
{
tosym->override(fromsym, st_shndx, is_ordinary, object, version);
if (tosym->has_alias())
{
Symbol* sym = this->weak_aliases_[tosym];
gold_assert(sym != NULL);
Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
do
{
ssym->override(fromsym, st_shndx, is_ordinary, object, version);
sym = this->weak_aliases_[ssym];
gold_assert(sym != NULL);
ssym = this->get_sized_symbol<size>(sym);
}
while (ssym != tosym);
}
}
// 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;
// This convenience function combines all the flags based on facts
// about the symbol.
static unsigned int
symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
unsigned int shndx, bool is_ordinary)
{
unsigned int bits;
switch (binding)
{
case elfcpp::STB_GLOBAL:
case elfcpp::STB_GNU_UNIQUE:
bits = global_flag;
break;
case elfcpp::STB_WEAK:
bits = weak_flag;
break;
case elfcpp::STB_LOCAL:
// We should only see externally visible symbols in the symbol
// table.
gold_error(_("invalid STB_LOCAL symbol in external symbols"));
bits = global_flag;
break;
default:
// Any target which wants to handle STB_LOOS, etc., needs to
// define a resolve method.
gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding));
bits = global_flag;
}
if (is_dynamic)
bits |= dynamic_flag;
else
bits |= regular_flag;
switch (shndx)
{
case elfcpp::SHN_UNDEF:
bits |= undef_flag;
break;
case elfcpp::SHN_COMMON:
if (!is_ordinary)
bits |= common_flag;
break;
default:
if (!is_ordinary && Symbol::is_common_shndx(shndx))
bits |= common_flag;
else
bits |= def_flag;
break;
}
return bits;
}
// Resolve a symbol. This is called the second and subsequent times
// we see a symbol. TO is the pre-existing symbol. ST_SHNDX is the
// section index for SYM, possibly adjusted for many sections.
// IS_ORDINARY is whether ST_SHNDX is a normal section index rather
// than a special code. ORIG_ST_SHNDX is the original section index,
// before any munging because of discarded sections, except that all
// non-ordinary section indexes are mapped to SHN_UNDEF. VERSION is
// 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,
unsigned int st_shndx, bool is_ordinary,
unsigned int orig_st_shndx,
Object* object, const char* version,
bool is_default_version)
{
bool to_is_ordinary;
const unsigned int to_shndx = to->shndx(&to_is_ordinary);
// It's possible for a symbol to be defined in an object file
// using .symver to give it a version, and for there to also be
// a linker script giving that symbol the same version. We
// don't want to give a multiple-definition error for this
// harmless redefinition.
if (to->source() == Symbol::FROM_OBJECT
&& to->object() == object
&& to->is_defined()
&& is_ordinary
&& to_is_ordinary
&& to_shndx == st_shndx
&& to->value() == sym.get_st_value())
return;
// Likewise for an absolute symbol defined twice with the same value.
if (!is_ordinary
&& st_shndx == elfcpp::SHN_ABS
&& !to_is_ordinary
&& to_shndx == elfcpp::SHN_ABS
&& to->value() == sym.get_st_value())
return;
if (parameters->target().has_resolve())
{
Sized_target<size, big_endian>* sized_target;
sized_target = parameters->sized_target<size, big_endian>();
if (sized_target->resolve(to, sym, object, version))
return;
}
if (!object->is_dynamic())
{
if (sym.get_st_type() == elfcpp::STT_COMMON
&& (is_ordinary || !Symbol::is_common_shndx(st_shndx)))
{
gold_warning(_("STT_COMMON symbol '%s' in %s "
"is not in a common section"),
to->demangled_name().c_str(),
to->object()->name().c_str());
return;
}
// Record that we've seen this symbol in a regular object.
to->set_in_reg();
}
else if (st_shndx == elfcpp::SHN_UNDEF
&& (to->visibility() == elfcpp::STV_HIDDEN
|| to->visibility() == elfcpp::STV_INTERNAL))
{
// The symbol is hidden, so a reference from a shared object
// cannot bind to it. We tried issuing a warning in this case,
// but that produces false positives when the symbol is
// actually resolved in a different shared object (PR 15574).
return;
}
else
{
// Record that we've seen this symbol in a dynamic object.
to->set_in_dyn();
}
// Record if we've seen this symbol in a real ELF object (i.e., the
// symbol is referenced from outside the world known to the plugin).
if (object->pluginobj() == NULL && !object->is_dynamic())
to->set_in_real_elf();
// If we're processing replacement files, allow new symbols to override
// the placeholders from the plugin objects.
// Treat common symbols specially since it is possible that an ELF
// file increased the size of the alignment.
if (to->source() == Symbol::FROM_OBJECT)
{
Pluginobj* obj = to->object()->pluginobj();
if (obj != NULL
&& parameters->options().plugins()->in_replacement_phase())
{
bool adjust_common = false;
typename Sized_symbol<size>::Size_type tosize = 0;
typename Sized_symbol<size>::Value_type tovalue = 0;
if (to->is_common()
&& !is_ordinary && Symbol::is_common_shndx(st_shndx))
{
adjust_common = true;
tosize = to->symsize();
tovalue = to->value();
}
this->override(to, sym, st_shndx, is_ordinary, object, version);
if (adjust_common)
{
if (tosize > to->symsize())
to->set_symsize(tosize);
if (tovalue > to->value())
to->set_value(tovalue);
}
return;
}
}
// A new weak undefined reference, merging with an old weak
// reference, could be a One Definition Rule (ODR) violation --
// especially if the types or sizes of the references differ. We'll
// store such pairs and look them up later to make sure they
// actually refer to the same lines of code. We also check
// combinations of weak and strong, which might occur if one case is
// inline and the other is not. (Note: not all ODR violations can
// be found this way, and not everything this finds is an ODR
// violation. But it's helpful to warn about.)
if (parameters->options().detect_odr_violations()
&& (sym.get_st_bind() == elfcpp::STB_WEAK
|| to->binding() == elfcpp::STB_WEAK)
&& orig_st_shndx != elfcpp::SHN_UNDEF
&& to_is_ordinary
&& to_shndx != elfcpp::SHN_UNDEF
&& sym.get_st_size() != 0 // Ignore weird 0-sized symbols.
&& to->symsize() != 0
&& (sym.get_st_type() != to->type()
|| sym.get_st_size() != to->symsize())
// C does not have a concept of ODR, so we only need to do this
// on C++ symbols. These have (mangled) names starting with _Z.
&& to->name()[0] == '_' && to->name()[1] == 'Z')
{
Symbol_location fromloc
= { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) };
Symbol_location toloc = { to->object(), to_shndx,
static_cast<off_t>(to->value()) };
this->candidate_odr_violations_[to->name()].insert(fromloc);
this->candidate_odr_violations_[to->name()].insert(toloc);
}
// Plugins don't provide a symbol type, so adopt the existing type
// if the FROM symbol is from a plugin.
elfcpp::STT fromtype = (object->pluginobj() != NULL
? to->type()
: sym.get_st_type());
unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
object->is_dynamic(),
st_shndx, is_ordinary);
bool adjust_common_sizes;
bool adjust_dyndef;
typename Sized_symbol<size>::Size_type tosize = to->symsize();
if (Symbol_table::should_override(to, frombits, fromtype, OBJECT,
object, &adjust_common_sizes,
&adjust_dyndef, is_default_version))
{
elfcpp::STB orig_tobinding = to->binding();
typename Sized_symbol<size>::Value_type tovalue = to->value();
this->override(to, sym, st_shndx, is_ordinary, object, version);
if (adjust_common_sizes)
{
if (tosize > to->symsize())
to->set_symsize(tosize);
if (tovalue > to->value())
to->set_value(tovalue);
}
if (adjust_dyndef)
{
// We are overriding an UNDEF or WEAK UNDEF with a DYN DEF.
// Remember which kind of UNDEF it was for future reference.
to->set_undef_binding(orig_tobinding);
}
}
else
{
if (adjust_common_sizes)
{
if (sym.get_st_size() > tosize)
to->set_symsize(sym.get_st_size());
if (sym.get_st_value() > to->value())
to->set_value(sym.get_st_value());
}
if (adjust_dyndef)
{
// We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF.
// Remember which kind of UNDEF it was.
to->set_undef_binding(sym.get_st_bind());
}
// The ELF ABI says that even for a reference to a symbol we
// merge the visibility.
to->override_visibility(sym.get_st_visibility());
}
// If we have a non-WEAK reference from a regular object to a
// dynamic object, mark the dynamic object as needed.
if (to->is_from_dynobj() && to->in_reg() && !to->is_undef_binding_weak())
to->object()->set_is_needed();
if (adjust_common_sizes && parameters->options().warn_common())
{
if (tosize > sym.get_st_size())
Symbol_table::report_resolve_problem(false,
_("common of '%s' overriding "
"smaller common"),
to, OBJECT, object);
else if (tosize < sym.get_st_size())
Symbol_table::report_resolve_problem(false,
_("common of '%s' overidden by "
"larger common"),
to, OBJECT, object);
else
Symbol_table::report_resolve_problem(false,
_("multiple common of '%s'"),
to, OBJECT, object);
}
}
// 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,
elfcpp::STT fromtype, Defined defined,
Object* object, bool* adjust_common_sizes,
bool* adjust_dyndef, bool is_default_version)
{
*adjust_common_sizes = false;
*adjust_dyndef = false;
unsigned int tobits;
if (to->source() == Symbol::IS_UNDEFINED)
tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true);
else if (to->source() != Symbol::FROM_OBJECT)
tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false);
else
{
bool is_ordinary;
unsigned int shndx = to->shndx(&is_ordinary);
tobits = symbol_to_bits(to->binding(),
to->object()->is_dynamic(),
shndx,
is_ordinary);
}
if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS)
&& !to->is_placeholder())
Symbol_table::report_resolve_problem(true,
_("symbol '%s' used as both __thread "
"and non-__thread"),
to, defined, object);
// 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.
// If either symbol is defined by an object included using
// --just-symbols, then don't warn. This is for compatibility
// with the GNU linker. FIXME: This is a hack.
if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
|| (object != NULL && object->just_symbols()))
return false;
if (!parameters->options().muldefs())
Symbol_table::report_resolve_problem(true,
_("multiple definition of '%s'"),
to, defined, object);
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.
if (parameters->options().warn_common())
Symbol_table::report_resolve_problem(false,
_("definition of '%s' overriding "
"common"),
to, defined, object);
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.
if (parameters->options().warn_common())
Symbol_table::report_resolve_problem(false,
_("definition of '%s' overriding "
"dynamic common definition"),
to, defined, object);
return true;
case DEF * 16 + DYN_DEF:
case WEAK_DEF * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a definition.
return false;
case DYN_DEF * 16 + DYN_DEF:
case DYN_WEAK_DEF * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a definition,
// unless the existing definition is an unversioned definition
// in the same dynamic object, and the new definition is a
// default version.
if (to->object() == object
&& to->version() == NULL
&& is_default_version)
return true;
// Or, if the existing definition is in an unused --as-needed library,
// and the reference is weak, let the new definition override.
if (to->in_reg()
&& to->is_undef_binding_weak()
&& to->object()->as_needed()
&& !to->object()->is_needed())
return true;
return false;
case 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 WEAK_UNDEF * 16 + DYN_DEF:
// When overriding a weak undef by a dynamic definition,
// we need to remember that the original undef was weak.
*adjust_dyndef = true;
return true;
case COMMON * 16 + DYN_DEF:
case 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:
// Ignore a weak dynamic definition if we already have a
// definition.
return false;
case UNDEF * 16 + DYN_WEAK_DEF:
// When overriding an undef by a dynamic weak definition,
// we need to remember that the original undef was not weak.
*adjust_dyndef = true;
return true;
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 WEAK_UNDEF * 16 + DYN_WEAK_DEF:
// When overriding a weak undef by a dynamic definition,
// we need to remember that the original undef was weak.
*adjust_dyndef = true;
return true;
case COMMON * 16 + DYN_WEAK_DEF:
case WEAK_COMMON * 16 + DYN_WEAK_DEF:
// Ignore a weak dynamic definition if we already have a common
// definition.
return false;
case DYN_COMMON * 16 + DYN_DEF:
case DYN_WEAK_COMMON * 16 + DYN_DEF:
case DYN_DEF * 16 + DYN_WEAK_DEF:
case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
case DYN_COMMON * 16 + DYN_WEAK_DEF:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
// If the existing definition is in an unused --as-needed library,
// and the reference is weak, let a new dynamic definition override.
if (to->in_reg()
&& to->is_undef_binding_weak()
&& to->object()->as_needed()
&& !to->object()->is_needed())
return true;
return false;
case DEF * 16 + UNDEF:
case WEAK_DEF * 16 + UNDEF:
case UNDEF * 16 + UNDEF:
// A new undefined reference tells us nothing.
return false;
case DYN_DEF * 16 + UNDEF:
case DYN_WEAK_DEF * 16 + UNDEF:
// For a dynamic def, we need to remember which kind of undef we see.
*adjust_dyndef = true;
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 UNDEF * 16 + WEAK_UNDEF:
case WEAK_UNDEF * 16 + WEAK_UNDEF:
case DYN_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 unless the
// exisiting symbol is a dynamic weak reference.
return false;
case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
// A new weak reference overrides an existing dynamic weak reference.
// This is necessary because a dynamic weak reference remembers
// the old binding, which may not be weak. If we keeps the existing
// dynamic weak reference, the weakness may be dropped in the output.
return true;
case DYN_DEF * 16 + WEAK_UNDEF:
case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
// For a dynamic def, we need to remember which kind of undef we see.
*adjust_dyndef = true;
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.
if (parameters->options().warn_common())
Symbol_table::report_resolve_problem(false,
_("common '%s' overridden by "
"previous definition"),
to, defined, object);
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();
}
}
// Issue an error or warning due to symbol resolution. IS_ERROR
// indicates an error rather than a warning. MSG is the error
// message; it is expected to have a %s for the symbol name. TO is
// the existing symbol. DEFINED/OBJECT is where the new symbol was
// found.
// FIXME: We should have better location information here. When the
// symbol is defined, we should be able to pull the location from the
// debug info if there is any.
void
Symbol_table::report_resolve_problem(bool is_error, const char* msg,
const Symbol* to, Defined defined,
Object* object)
{
std::string demangled(to->demangled_name());
size_t len = strlen(msg) + demangled.length() + 10;
char* buf = new char[len];
snprintf(buf, len, msg, demangled.c_str());
const char* objname;
switch (defined)
{
case OBJECT:
objname = object->name().c_str();
break;
case COPY:
objname = _("COPY reloc");
break;
case DEFSYM:
case UNDEFINED:
objname = _("command line");
break;
case SCRIPT:
objname = _("linker script");
break;
case PREDEFINED:
case INCREMENTAL_BASE:
objname = _("linker defined");
break;
default:
gold_unreachable();
}
if (is_error)
gold_error("%s: %s", objname, buf);
else
gold_warning("%s: %s", objname, buf);
delete[] buf;
if (to->source() == Symbol::FROM_OBJECT)
objname = to->object()->name().c_str();
else
objname = _("command line");
gold_info("%s: %s: previous definition here", program_name, objname);
}
// Completely override existing symbol. Everything bar name_,
// version_, and is_forced_local_ flag are copied. version_ is
// cleared if from->version_ is clear. Returns true if this symbol
// should be forced local.
bool
Symbol::clone(const Symbol* from)
{
// Don't allow cloning after dynamic linking info is attached to symbols.
// We aren't prepared to merge such.
gold_assert(!this->has_symtab_index() && !from->has_symtab_index());
gold_assert(!this->has_dynsym_index() && !from->has_dynsym_index());
gold_assert(this->got_offset_list() == NULL
&& from->got_offset_list() == NULL);
gold_assert(!this->has_plt_offset() && !from->has_plt_offset());
if (!from->version_)
this->version_ = from->version_;
this->u1_ = from->u1_;
this->u2_ = from->u2_;
this->type_ = from->type_;
this->binding_ = from->binding_;
this->visibility_ = from->visibility_;
this->nonvis_ = from->nonvis_;
this->source_ = from->source_;
this->is_def_ = from->is_def_;
this->is_forwarder_ = from->is_forwarder_;
this->has_alias_ = from->has_alias_;
this->needs_dynsym_entry_ = from->needs_dynsym_entry_;
this->in_reg_ = from->in_reg_;
this->in_dyn_ = from->in_dyn_;
this->needs_dynsym_value_ = from->needs_dynsym_value_;
this->has_warning_ = from->has_warning_;
this->is_copied_from_dynobj_ = from->is_copied_from_dynobj_;
this->is_ordinary_shndx_ = from->is_ordinary_shndx_;
this->in_real_elf_ = from->in_real_elf_;
this->is_defined_in_discarded_section_
= from->is_defined_in_discarded_section_;
this->undef_binding_set_ = from->undef_binding_set_;
this->undef_binding_weak_ = from->undef_binding_weak_;
this->is_predefined_ = from->is_predefined_;
this->is_protected_ = from->is_protected_;
this->non_zero_localentry_ = from->non_zero_localentry_;
return !this->is_forced_local_ && from->is_forced_local_;
}
template <int size>
bool
Sized_symbol<size>::clone(const Sized_symbol<size>* from)
{
this->value_ = from->value_;
this->symsize_ = from->symsize_;
return Symbol::clone(from);
}
// 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,
elfcpp::STT fromtype,
Defined defined)
{
bool adjust_common_sizes;
bool adjust_dyn_def;
unsigned int frombits = global_flag | regular_flag | def_flag;
bool ret = Symbol_table::should_override(to, frombits, fromtype, defined,
NULL, &adjust_common_sizes,
&adjust_dyn_def, false);
gold_assert(!adjust_common_sizes && !adjust_dyn_def);
return ret;
}
// Override symbol base with a special symbol.
void
Symbol::override_base_with_special(const Symbol* from)
{
bool same_name = this->name_ == from->name_;
gold_assert(same_name || this->has_alias());
// If we are overriding an undef, remember the original binding.
if (this->is_undefined())
this->set_undef_binding(this->binding_);
this->source_ = from->source_;
switch (from->source_)
{
case FROM_OBJECT:
case IN_OUTPUT_DATA:
case IN_OUTPUT_SEGMENT:
this->u1_ = from->u1_;
this->u2_ = from->u2_;
break;
case IS_CONSTANT:
case IS_UNDEFINED:
break;
default:
gold_unreachable();
break;
}
if (same_name)
{
// When overriding a versioned symbol with a special symbol, we
// may be changing the version. This will happen if we see a
// special symbol such as "_end" defined in a shared object with
// one version (from a version script), but we want to define it
// here with a different version (from a different version
// script).
this->version_ = from->version_;
}
this->type_ = from->type_;
this->binding_ = from->binding_;
this->override_visibility(from->visibility_);
this->nonvis_ = from->nonvis_;
// Special symbols are always considered to be regular symbols.
this->in_reg_ = true;
if (from->needs_dynsym_entry_)
this->needs_dynsym_entry_ = true;
if (from->needs_dynsym_value_)
this->needs_dynsym_value_ = true;
this->is_predefined_ = from->is_predefined_;
// We shouldn't see these flags. If we do, we need to handle them
// somehow.
gold_assert(!from->is_forwarder_);
gold_assert(!from->has_plt_offset());
gold_assert(!from->has_warning_);
gold_assert(!from->is_copied_from_dynobj_);
gold_assert(!from->is_forced_local_);
}
// 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_;
}
// Override TOSYM with the special symbol FROMSYM. This handles all
// aliases of TOSYM.
template<int size>
void
Symbol_table::override_with_special(Sized_symbol<size>* tosym,
const Sized_symbol<size>* fromsym)
{
tosym->override_with_special(fromsym);
if (tosym->has_alias())
{
Symbol* sym = this->weak_aliases_[tosym];
gold_assert(sym != NULL);
Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
do
{
ssym->override_with_special(fromsym);
sym = this->weak_aliases_[ssym];
gold_assert(sym != NULL);
ssym = this->get_sized_symbol<size>(sym);
}
while (ssym != tosym);
}
if (tosym->binding() == elfcpp::STB_LOCAL
|| ((tosym->visibility() == elfcpp::STV_HIDDEN
|| tosym->visibility() == elfcpp::STV_INTERNAL)
&& (tosym->binding() == elfcpp::STB_GLOBAL
|| tosym->binding() == elfcpp::STB_GNU_UNIQUE
|| tosym->binding() == elfcpp::STB_WEAK)
&& !parameters->options().relocatable()))
this->force_local(tosym);
}
// Instantiate the templates we need. We could use the configure
// script to restrict this to only the ones needed for implemented
// targets.
// We have to instantiate both big and little endian versions because
// these are used by other templates that depends on size only.
#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
template
void
Symbol_table::resolve<32, false>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, false>& sym,
unsigned int st_shndx,
bool is_ordinary,
unsigned int orig_st_shndx,
Object* object,
const char* version,
bool is_default_version);
template
void
Symbol_table::resolve<32, true>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, true>& sym,
unsigned int st_shndx,
bool is_ordinary,
unsigned int orig_st_shndx,
Object* object,
const char* version,
bool is_default_version);
#endif
#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
template
void
Symbol_table::resolve<64, false>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, false>& sym,
unsigned int st_shndx,
bool is_ordinary,
unsigned int orig_st_shndx,
Object* object,
const char* version,
bool is_default_version);
template
void
Symbol_table::resolve<64, true>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, true>& sym,
unsigned int st_shndx,
bool is_ordinary,
unsigned int orig_st_shndx,
Object* object,
const char* version,
bool is_default_version);
#endif
#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
template
void
Symbol_table::override_with_special<32>(Sized_symbol<32>*,
const Sized_symbol<32>*);
#endif
#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
template
void
Symbol_table::override_with_special<64>(Sized_symbol<64>*,
const Sized_symbol<64>*);
#endif
template
bool
Sized_symbol<32>::clone(const Sized_symbol<32>*);
template
bool
Sized_symbol<64>::clone(const Sized_symbol<64>*);
} // End namespace gold.
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