old-cross-binutils/gold/symtab.cc
2006-09-29 22:34:01 +00:00

537 lines
15 KiB
C++

// symtab.cc -- the gold symbol table
#include "gold.h"
#include <cassert>
#include <stdint.h>
#include <string>
#include <utility>
#include "object.h"
#include "output.h"
#include "target.h"
#include "symtab.h"
namespace gold
{
// Class Symbol.
// Initialize the fields in the base class Symbol.
template<int size, bool big_endian>
void
Symbol::init_base(const char* name, const char* version, Object* object,
const elfcpp::Sym<size, big_endian>& sym)
{
this->name_ = name;
this->version_ = version;
this->object_ = object;
this->shnum_ = sym.get_st_shndx(); // FIXME: Handle SHN_XINDEX.
this->type_ = sym.get_st_type();
this->binding_ = sym.get_st_bind();
this->visibility_ = sym.get_st_visibility();
this->other_ = sym.get_st_nonvis();
this->is_special_ = false;
this->is_def_ = false;
this->is_forwarder_ = false;
this->in_dyn_ = object->is_dynamic();
}
// Initialize the fields in Sized_symbol.
template<int size>
template<bool big_endian>
void
Sized_symbol<size>::init(const char* name, const char* version, Object* object,
const elfcpp::Sym<size, big_endian>& sym)
{
this->init_base(name, version, object, sym);
this->value_ = sym.get_st_value();
this->size_ = sym.get_st_size();
}
// Class Symbol_table.
Symbol_table::Symbol_table()
: size_(0), offset_(0), table_(), namepool_(), forwarders_()
{
}
Symbol_table::~Symbol_table()
{
}
// The hash function. The key is always canonicalized, so we use a
// simple combination of the pointers.
size_t
Symbol_table::Symbol_table_hash::operator()(const Symbol_table_key& key) const
{
return (reinterpret_cast<size_t>(key.first)
^ reinterpret_cast<size_t>(key.second));
}
// The symbol table key equality function. This is only called with
// canonicalized name and version strings, so we can use pointer
// comparison.
bool
Symbol_table::Symbol_table_eq::operator()(const Symbol_table_key& k1,
const Symbol_table_key& k2) const
{
return k1.first == k2.first && k1.second == k2.second;
}
// Make TO a symbol which forwards to FROM.
void
Symbol_table::make_forwarder(Symbol* from, Symbol* to)
{
assert(!from->is_forwarder() && !to->is_forwarder());
this->forwarders_[from] = to;
from->set_forwarder();
}
// Resolve the forwards from FROM, returning the real symbol.
Symbol*
Symbol_table::resolve_forwards(Symbol* from) const
{
assert(from->is_forwarder());
Unordered_map<Symbol*, Symbol*>::const_iterator p =
this->forwarders_.find(from);
assert(p != this->forwarders_.end());
return p->second;
}
// Look up a symbol by name.
Symbol*
Symbol_table::lookup(const char* name, const char* version) const
{
name = this->namepool_.find(name);
if (name == NULL)
return NULL;
if (version != NULL)
{
version = this->namepool_.find(version);
if (version == NULL)
return NULL;
}
Symbol_table_key key(name, version);
Symbol_table::Symbol_table_type::const_iterator p = this->table_.find(key);
if (p == this->table_.end())
return NULL;
return p->second;
}
// Resolve a Symbol with another Symbol. This is only used in the
// unusual case where there are references to both an unversioned
// symbol and a symbol with a version, and we then discover that that
// version is the default version. Because this is unusual, we do
// this the slow way, by converting back to an ELF symbol.
template<int size, bool big_endian>
void
Symbol_table::resolve(Sized_symbol<size>* to, const Sized_symbol<size>* from
ACCEPT_SIZE_ENDIAN)
{
unsigned char buf[elfcpp::Elf_sizes<size>::sym_size];
elfcpp::Sym_write<size, big_endian> esym(buf);
// We don't bother to set the st_name field.
esym.put_st_value(from->value());
esym.put_st_size(from->symsize());
esym.put_st_info(from->binding(), from->type());
esym.put_st_other(from->visibility(), from->other());
esym.put_st_shndx(from->shnum());
Symbol_table::resolve(to, esym.sym(), from->object());
}
// Add one symbol from OBJECT to the symbol table. NAME is symbol
// name and VERSION is the version; both are canonicalized. DEF is
// whether this is the default version.
// If DEF is true, then this is the definition of a default version of
// a symbol. That means that any lookup of NAME/NULL and any lookup
// of NAME/VERSION should always return the same symbol. This is
// obvious for references, but in particular we want to do this for
// definitions: overriding NAME/NULL should also override
// NAME/VERSION. If we don't do that, it would be very hard to
// override functions in a shared library which uses versioning.
// We implement this by simply making both entries in the hash table
// point to the same Symbol structure. That is easy enough if this is
// the first time we see NAME/NULL or NAME/VERSION, but it is possible
// that we have seen both already, in which case they will both have
// independent entries in the symbol table. We can't simply change
// the symbol table entry, because we have pointers to the entries
// attached to the object files. So we mark the entry attached to the
// object file as a forwarder, and record it in the forwarders_ map.
// Note that entries in the hash table will never be marked as
// forwarders.
template<int size, bool big_endian>
Symbol*
Symbol_table::add_from_object(Sized_object<size, big_endian>* object,
const char *name,
const char *version, bool def,
const elfcpp::Sym<size, big_endian>& sym)
{
Symbol* const snull = NULL;
std::pair<typename Symbol_table_type::iterator, bool> ins =
this->table_.insert(std::make_pair(std::make_pair(name, version), snull));
std::pair<typename Symbol_table_type::iterator, bool> insdef =
std::make_pair(this->table_.end(), false);
if (def)
{
const char* const vnull = NULL;
insdef = this->table_.insert(std::make_pair(std::make_pair(name, vnull),
snull));
}
// ins.first: an iterator, which is a pointer to a pair.
// ins.first->first: the key (a pair of name and version).
// ins.first->second: the value (Symbol*).
// ins.second: true if new entry was inserted, false if not.
Sized_symbol<size>* ret;
if (!ins.second)
{
// We already have an entry for NAME/VERSION.
ret = this->get_sized_symbol SELECT_SIZE_NAME (ins.first->second
SELECT_SIZE(size));
assert(ret != NULL);
Symbol_table::resolve(ret, sym, object);
if (def)
{
if (insdef.second)
{
// This is the first time we have seen NAME/NULL. Make
// NAME/NULL point to NAME/VERSION.
insdef.first->second = ret;
}
else
{
// This is the unfortunate case where we already have
// entries for both NAME/VERSION and NAME/NULL.
const Sized_symbol<size>* sym2;
sym2 = this->get_sized_symbol SELECT_SIZE_NAME (
insdef.first->second
SELECT_SIZE(size));
Symbol_table::resolve SELECT_SIZE_ENDIAN_NAME (
ret, sym2 SELECT_SIZE_ENDIAN(size, big_endian));
this->make_forwarder(insdef.first->second, ret);
insdef.first->second = ret;
}
}
}
else
{
// This is the first time we have seen NAME/VERSION.
assert(ins.first->second == NULL);
if (def && !insdef.second)
{
// We already have an entry for NAME/NULL. Make
// NAME/VERSION point to it.
ret = this->get_sized_symbol SELECT_SIZE_NAME (insdef.first->second
SELECT_SIZE(size));
Symbol_table::resolve(ret, sym, object);
ins.first->second = ret;
}
else
{
Sized_target<size, big_endian>* target = object->sized_target();
if (!target->has_make_symbol())
ret = new Sized_symbol<size>();
else
{
ret = target->make_symbol();
if (ret == NULL)
{
// This means that we don't want a symbol table
// entry after all.
if (!def)
this->table_.erase(ins.first);
else
{
this->table_.erase(insdef.first);
// Inserting insdef invalidated ins.
this->table_.erase(std::make_pair(name, version));
}
return NULL;
}
}
ret->init(name, version, object, sym);
ins.first->second = ret;
if (def)
{
// This is the first time we have seen NAME/NULL. Point
// it at the new entry for NAME/VERSION.
assert(insdef.second);
insdef.first->second = ret;
}
}
}
return ret;
}
// Add all the symbols in an object to the hash table.
template<int size, bool big_endian>
void
Symbol_table::add_from_object(
Sized_object<size, big_endian>* object,
const elfcpp::Sym<size, big_endian>* syms,
size_t count,
const char* sym_names,
size_t sym_name_size,
Symbol** sympointers)
{
// We take the size from the first object we see.
if (this->get_size() == 0)
this->set_size(size);
if (size != this->get_size() || size != object->target()->get_size())
{
fprintf(stderr, _("%s: %s: mixing 32-bit and 64-bit ELF objects\n"),
program_name, object->name().c_str());
gold_exit(false);
}
const unsigned char* p = reinterpret_cast<const unsigned char*>(syms);
for (size_t i = 0; i < count; ++i)
{
elfcpp::Sym<size, big_endian> sym(p);
unsigned int st_name = sym.get_st_name();
if (st_name >= sym_name_size)
{
fprintf(stderr,
_("%s: %s: bad global symbol name offset %u at %lu\n"),
program_name, object->name().c_str(), st_name,
static_cast<unsigned long>(i));
gold_exit(false);
}
const char* name = sym_names + st_name;
// In an object file, an '@' in the name separates the symbol
// name from the version name. If there are two '@' characters,
// this is the default version.
const char* ver = strchr(name, '@');
Symbol* res;
if (ver == NULL)
{
name = this->namepool_.add(name);
res = this->add_from_object(object, name, NULL, false, sym);
}
else
{
name = this->namepool_.add(name, ver - name);
bool def = false;
++ver;
if (*ver == '@')
{
def = true;
++ver;
}
ver = this->namepool_.add(ver);
res = this->add_from_object(object, name, ver, def, sym);
}
*sympointers++ = res;
p += elfcpp::Elf_sizes<size>::sym_size;
}
}
// Set the final values for all the symbols. Record the file offset
// OFF. Add their names to POOL. Return the new file offset.
off_t
Symbol_table::finalize(off_t off, Stringpool* pool)
{
if (this->size_ == 32)
return this->sized_finalize<32>(off, pool);
else if (this->size_ == 64)
return this->sized_finalize<64>(off, pool);
else
abort();
}
// Set the final value for all the symbols.
template<int size>
off_t
Symbol_table::sized_finalize(off_t off, Stringpool* pool)
{
off = (off + (size >> 3) - 1) & ~ ((size >> 3) - 1);
this->offset_ = off;
const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
Symbol_table_type::iterator p = this->table_.begin();
size_t count = 0;
while (p != this->table_.end())
{
Sized_symbol<size>* sym = static_cast<Sized_symbol<size>*>(p->second);
// FIXME: Here we need to decide which symbols should go into
// the output file.
// FIXME: This is wrong.
if (sym->shnum() >= elfcpp::SHN_LORESERVE)
{
++p;
continue;
}
const Object::Map_to_output* mo =
sym->object()->section_output_info(sym->shnum());
if (mo->output_section == NULL)
{
// We should be able to erase this symbol from the symbol
// table, but at least with gcc 4.0.2
// std::unordered_map::erase doesn't appear to return the
// new iterator.
// p = this->table_.erase(p);
++p;
}
else
{
sym->set_value(sym->value()
+ mo->output_section->address()
+ mo->offset);
pool->add(sym->name());
++p;
++count;
off += sym_size;
}
}
this->output_count_ = count;
return off;
}
// Write out the global symbols.
void
Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
Output_file* of) const
{
if (this->size_ == 32)
{
if (target->is_big_endian())
this->sized_write_globals<32, true>(target, sympool, of);
else
this->sized_write_globals<32, false>(target, sympool, of);
}
else if (this->size_ == 64)
{
if (target->is_big_endian())
this->sized_write_globals<64, true>(target, sympool, of);
else
this->sized_write_globals<64, false>(target, sympool, of);
}
else
abort();
}
// Write out the global symbols.
template<int size, bool big_endian>
void
Symbol_table::sized_write_globals(const Target*,
const Stringpool* sympool,
Output_file* of) const
{
const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
unsigned char* psyms = of->get_output_view(this->offset_,
this->output_count_ * sym_size);
unsigned char* ps = psyms;
for (Symbol_table_type::const_iterator p = this->table_.begin();
p != this->table_.end();
++p)
{
Sized_symbol<size>* sym = static_cast<Sized_symbol<size>*>(p->second);
// FIXME: This repeats sized_finalize().
// FIXME: This is wrong.
if (sym->shnum() >= elfcpp::SHN_LORESERVE)
continue;
const Object::Map_to_output* mo =
sym->object()->section_output_info(sym->shnum());
if (mo->output_section == NULL)
continue;
elfcpp::Sym_write<size, big_endian> osym(ps);
osym.put_st_name(sympool->get_offset(sym->name()));
osym.put_st_value(sym->value());
osym.put_st_size(sym->symsize());
osym.put_st_info(elfcpp::elf_st_info(sym->binding(), sym->type()));
osym.put_st_other(elfcpp::elf_st_other(sym->visibility(), sym->other()));
osym.put_st_shndx(mo->output_section->shndx());
ps += sym_size;
}
of->write_output_view(this->offset_, this->output_count_ * sym_size, psyms);
}
// Instantiate the templates we need. We could use the configure
// script to restrict this to only the ones needed for implemented
// targets.
template
void
Symbol_table::add_from_object<32, true>(
Sized_object<32, true>* object,
const elfcpp::Sym<32, true>* syms,
size_t count,
const char* sym_names,
size_t sym_name_size,
Symbol** sympointers);
template
void
Symbol_table::add_from_object<32, false>(
Sized_object<32, false>* object,
const elfcpp::Sym<32, false>* syms,
size_t count,
const char* sym_names,
size_t sym_name_size,
Symbol** sympointers);
template
void
Symbol_table::add_from_object<64, true>(
Sized_object<64, true>* object,
const elfcpp::Sym<64, true>* syms,
size_t count,
const char* sym_names,
size_t sym_name_size,
Symbol** sympointers);
template
void
Symbol_table::add_from_object<64, false>(
Sized_object<64, false>* object,
const elfcpp::Sym<64, false>* syms,
size_t count,
const char* sym_names,
size_t sym_name_size,
Symbol** sympointers);
} // End namespace gold.