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