binutils-gdb/gold/symtab.h
Ian Lance Taylor f0641a0b38 Rework stringpool and hash tables so that we always generate the same
output regardless of randomize_va_space.
2006-11-07 04:40:46 +00:00

863 lines
25 KiB
C++

// symtab.h -- the gold symbol table -*- C++ -*-
// Symbol_table
// The symbol table.
#include <string>
#include <utility>
#include <vector>
#include <cassert>
#include "elfcpp.h"
#include "stringpool.h"
#include "object.h"
#ifndef GOLD_SYMTAB_H
#define GOLD_SYMTAB_H
namespace gold
{
class Object;
class Relobj;
class Dynobj;
class Output_data;
class Output_segment;
class Output_file;
class Target;
// The base class of an entry in the symbol table. The symbol table
// can have a lot of entries, so we don't want this class to big.
// Size dependent fields can be found in the template class
// Sized_symbol. Targets may support their own derived classes.
class Symbol
{
public:
// Because we want the class to be small, we don't use any virtual
// functions. But because symbols can be defined in different
// places, we need to classify them. This enum is the different
// sources of symbols we support.
enum Source
{
// Symbol defined in a relocatable or dynamic input file--this is
// the most common case.
FROM_OBJECT,
// Symbol defined in an Output_data, a special section created by
// the target.
IN_OUTPUT_DATA,
// Symbol defined in an Output_segment, with no associated
// section.
IN_OUTPUT_SEGMENT,
// Symbol value is constant.
CONSTANT
};
// When the source is IN_OUTPUT_SEGMENT, we need to describe what
// the offset means.
enum Segment_offset_base
{
// From the start of the segment.
SEGMENT_START,
// From the end of the segment.
SEGMENT_END,
// From the filesz of the segment--i.e., after the loaded bytes
// but before the bytes which are allocated but zeroed.
SEGMENT_BSS
};
// Return the symbol name.
const char*
name() const
{ return this->name_; }
// Return the symbol version. This will return NULL for an
// unversioned symbol.
const char*
version() const
{ return this->version_; }
// Return the symbol source.
Source
source() const
{ return this->source_; }
// Return the object with which this symbol is associated.
Object*
object() const
{
assert(this->source_ == FROM_OBJECT);
return this->u_.from_object.object;
}
// Return the index of the section in the input relocatable or
// dynamic object file.
unsigned int
shnum() const
{
assert(this->source_ == FROM_OBJECT);
return this->u_.from_object.shnum;
}
// Return the output data section with which this symbol is
// associated, if the symbol was specially defined with respect to
// an output data section.
Output_data*
output_data() const
{
assert(this->source_ == IN_OUTPUT_DATA);
return this->u_.in_output_data.output_data;
}
// If this symbol was defined with respect to an output data
// section, return whether the value is an offset from end.
bool
offset_is_from_end() const
{
assert(this->source_ == IN_OUTPUT_DATA);
return this->u_.in_output_data.offset_is_from_end;
}
// Return the output segment with which this symbol is associated,
// if the symbol was specially defined with respect to an output
// segment.
Output_segment*
output_segment() const
{
assert(this->source_ == IN_OUTPUT_SEGMENT);
return this->u_.in_output_segment.output_segment;
}
// If this symbol was defined with respect to an output segment,
// return the offset base.
Segment_offset_base
offset_base() const
{
assert(this->source_ == IN_OUTPUT_SEGMENT);
return this->u_.in_output_segment.offset_base;
}
// Return the symbol binding.
elfcpp::STB
binding() const
{ return this->binding_; }
// Return the symbol type.
elfcpp::STT
type() const
{ return this->type_; }
// Return the symbol visibility.
elfcpp::STV
visibility() const
{ return this->visibility_; }
// Return the non-visibility part of the st_other field.
unsigned char
nonvis() const
{ return this->nonvis_; }
// Return whether this symbol is a forwarder. This will never be
// true of a symbol found in the hash table, but may be true of
// symbol pointers attached to object files.
bool
is_forwarder() const
{ return this->is_forwarder_; }
// Mark this symbol as a forwarder.
void
set_forwarder()
{ this->is_forwarder_ = true; }
// Return whether this symbol was ever seen in a dynamic object.
bool
in_dyn() const
{ return this->in_dyn_; }
// Mark this symbol as having been seen in a dynamic object.
void
set_in_dyn()
{ this->in_dyn_ = true; }
// Return whether this symbol has an entry in the GOT section.
bool
has_got_offset() const
{ return this->has_got_offset_; }
// Return the offset into the GOT section of this symbol.
unsigned int
got_offset() const
{
assert(this->has_got_offset());
return this->got_offset_;
}
// Set the GOT offset of this symbol.
void
set_got_offset(unsigned int got_offset)
{
this->has_got_offset_ = true;
this->got_offset_ = got_offset;
}
// Return whether this symbol is resolved locally. This is always
// true when linking statically. It is true for a symbol defined in
// this object when using -Bsymbolic. It is true for a symbol
// marked local in a version file. FIXME: This needs to be
// completed.
bool
is_resolved_locally() const
{ return !this->in_dyn_; }
// Return whether this is a defined symbol (not undefined or
// common).
bool
is_defined() const
{
return (this->source_ != FROM_OBJECT
|| (this->u_.from_object.shnum != elfcpp::SHN_UNDEF
&& this->u_.from_object.shnum != elfcpp::SHN_COMMON));
}
// Return whether this is an undefined symbol.
bool
is_undefined() const
{
return this->source_ == FROM_OBJECT && this->shnum() == elfcpp::SHN_UNDEF;
}
// Return whether this is a common symbol.
bool
is_common() const
{
return (this->source_ == FROM_OBJECT
&& (this->u_.from_object.shnum == elfcpp::SHN_COMMON
|| this->type_ == elfcpp::STT_COMMON));
}
// Return whether there should be a warning for references to this
// symbol.
bool
has_warning() const
{ return this->has_warning_; }
// Mark this symbol as having a warning.
void
set_has_warning()
{ this->has_warning_ = true; }
protected:
// Instances of this class should always be created at a specific
// size.
Symbol()
{ memset(this, 0, sizeof *this); }
// Initialize the general fields.
void
init_fields(const char* name, const char* version,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis);
// Initialize fields from an ELF symbol in OBJECT.
template<int size, bool big_endian>
void
init_base(const char *name, const char* version, Object* object,
const elfcpp::Sym<size, big_endian>&);
// Initialize fields for an Output_data.
void
init_base(const char* name, Output_data*, elfcpp::STT, elfcpp::STB,
elfcpp::STV, unsigned char nonvis, bool offset_is_from_end);
// Initialize fields for an Output_segment.
void
init_base(const char* name, Output_segment* os, elfcpp::STT type,
elfcpp::STB binding, elfcpp::STV visibility,
unsigned char nonvis, Segment_offset_base offset_base);
// Initialize fields for a constant.
void
init_base(const char* name, elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis);
// Override existing symbol.
template<int size, bool big_endian>
void
override_base(const elfcpp::Sym<size, big_endian>&, Object* object);
private:
Symbol(const Symbol&);
Symbol& operator=(const Symbol&);
// Symbol name (expected to point into a Stringpool).
const char* name_;
// Symbol version (expected to point into a Stringpool). This may
// be NULL.
const char* version_;
union
{
// This struct is used if SOURCE_ == FROM_OBJECT.
struct
{
// Object in which symbol is defined, or in which it was first
// seen.
Object* object;
// Section number in object_ in which symbol is defined.
unsigned int shnum;
} from_object;
// This struct is used if SOURCE_ == IN_OUTPUT_DATA.
struct
{
// Output_data in which symbol is defined. Before
// Layout::finalize the symbol's value is an offset within the
// Output_data.
Output_data* output_data;
// True if the offset is from the end, false if the offset is
// from the beginning.
bool offset_is_from_end;
} in_output_data;
// This struct is used if SOURCE_ == IN_OUTPUT_SEGMENT.
struct
{
// Output_segment in which the symbol is defined. Before
// Layout::finalize the symbol's value is an offset.
Output_segment* output_segment;
// The base to use for the offset before Layout::finalize.
Segment_offset_base offset_base;
} in_output_segment;
} u_;
// If this symbol has an entry in the GOT section (has_got_offset_
// is true), this is the offset.
unsigned int got_offset_;
// Symbol type.
elfcpp::STT type_ : 4;
// Symbol binding.
elfcpp::STB binding_ : 4;
// Symbol visibility.
elfcpp::STV visibility_ : 2;
// Rest of symbol st_other field.
unsigned int nonvis_ : 6;
// The type of symbol.
Source source_ : 3;
// True if this symbol always requires special target-specific
// handling.
bool is_target_special_ : 1;
// True if this is the default version of the symbol.
bool is_def_ : 1;
// True if this symbol really forwards to another symbol. This is
// used when we discover after the fact that two different entries
// in the hash table really refer to the same symbol. This will
// never be set for a symbol found in the hash table, but may be set
// for a symbol found in the list of symbols attached to an Object.
// It forwards to the symbol found in the forwarders_ map of
// Symbol_table.
bool is_forwarder_ : 1;
// True if we've seen this symbol in a dynamic object.
bool in_dyn_ : 1;
// True if the symbol has an entry in the GOT section.
bool has_got_offset_ : 1;
// True if there is a warning for this symbol.
bool has_warning_ : 1;
};
// The parts of a symbol which are size specific. Using a template
// derived class like this helps us use less space on a 32-bit system.
template<int size>
class Sized_symbol : public Symbol
{
public:
typedef typename elfcpp::Elf_types<size>::Elf_Addr Value_type;
typedef typename elfcpp::Elf_types<size>::Elf_WXword Size_type;
Sized_symbol()
{ }
// Initialize fields from an ELF symbol in OBJECT.
template<bool big_endian>
void
init(const char *name, const char* version, Object* object,
const elfcpp::Sym<size, big_endian>&);
// Initialize fields for an Output_data.
void
init(const char* name, Output_data*, Value_type value, Size_type symsize,
elfcpp::STT, elfcpp::STB, elfcpp::STV, unsigned char nonvis,
bool offset_is_from_end);
// Initialize fields for an Output_segment.
void
init(const char* name, Output_segment*, Value_type value, Size_type symsize,
elfcpp::STT, elfcpp::STB, elfcpp::STV, unsigned char nonvis,
Segment_offset_base offset_base);
// Initialize fields for a constant.
void
init(const char* name, Value_type value, Size_type symsize,
elfcpp::STT, elfcpp::STB, elfcpp::STV, unsigned char nonvis);
// Override existing symbol.
template<bool big_endian>
void
override(const elfcpp::Sym<size, big_endian>&, Object* object);
// Return the symbol's value.
Value_type
value() const
{ return this->value_; }
// Return the symbol's size (we can't call this 'size' because that
// is a template parameter).
Size_type
symsize() const
{ return this->symsize_; }
// Set the symbol size. This is used when resolving common symbols.
void
set_symsize(Size_type symsize)
{ this->symsize_ = symsize; }
// Set the symbol value. This is called when we store the final
// values of the symbols into the symbol table.
void
set_value(Value_type value)
{ this->value_ = value; }
private:
Sized_symbol(const Sized_symbol&);
Sized_symbol& operator=(const Sized_symbol&);
// Symbol value. Before Layout::finalize this is the offset in the
// input section. This is set to the final value during
// Layout::finalize.
Value_type value_;
// Symbol size.
Size_type symsize_;
};
// A struct describing a symbol defined by the linker, where the value
// of the symbol is defined based on an output section. This is used
// for symbols defined by the linker, like "_init_array_start".
struct Define_symbol_in_section
{
// The symbol name.
const char* name;
// The name of the output section with which this symbol should be
// associated. If there is no output section with that name, the
// symbol will be defined as zero.
const char* output_section;
// The offset of the symbol within the output section. This is an
// offset from the start of the output section, unless start_at_end
// is true, in which case this is an offset from the end of the
// output section.
uint64_t value;
// The size of the symbol.
uint64_t size;
// The symbol type.
elfcpp::STT type;
// The symbol binding.
elfcpp::STB binding;
// The symbol visibility.
elfcpp::STV visibility;
// The rest of the st_other field.
unsigned char nonvis;
// If true, the value field is an offset from the end of the output
// section.
bool offset_is_from_end;
// If true, this symbol is defined only if we see a reference to it.
bool only_if_ref;
};
// A struct describing a symbol defined by the linker, where the value
// of the symbol is defined based on a segment. This is used for
// symbols defined by the linker, like "_end". We describe the
// segment with which the symbol should be associated by its
// characteristics. If no segment meets these characteristics, the
// symbol will be defined as zero. If there is more than one segment
// which meets these characteristics, we will use the first one.
struct Define_symbol_in_segment
{
// The symbol name.
const char* name;
// The segment type where the symbol should be defined, typically
// PT_LOAD.
elfcpp::PT segment_type;
// Bitmask of segment flags which must be set.
elfcpp::PF segment_flags_set;
// Bitmask of segment flags which must be clear.
elfcpp::PF segment_flags_clear;
// The offset of the symbol within the segment. The offset is
// calculated from the position set by offset_base.
uint64_t value;
// The size of the symbol.
uint64_t size;
// The symbol type.
elfcpp::STT type;
// The symbol binding.
elfcpp::STB binding;
// The symbol visibility.
elfcpp::STV visibility;
// The rest of the st_other field.
unsigned char nonvis;
// The base from which we compute the offset.
Symbol::Segment_offset_base offset_base;
// If true, this symbol is defined only if we see a reference to it.
bool only_if_ref;
};
// This class manages warnings. Warnings are a GNU extension. When
// we see a section named .gnu.warning.SYM in an object file, and if
// we wind using the definition of SYM from that object file, then we
// will issue a warning for any relocation against SYM from a
// different object file. The text of the warning is the contents of
// the section. This is not precisely the definition used by the old
// GNU linker; the old GNU linker treated an occurrence of
// .gnu.warning.SYM as defining a warning symbol. A warning symbol
// would trigger a warning on any reference. However, it was
// inconsistent in that a warning in a dynamic object only triggered
// if there was no definition in a regular object. This linker is
// different in that we only issue a warning if we use the symbol
// definition from the same object file as the warning section.
class Warnings
{
public:
Warnings()
: warnings_()
{ }
// Add a warning for symbol NAME in section SHNDX in object OBJ.
void
add_warning(Symbol_table* symtab, const char* name, Object* obj,
unsigned int shndx);
// For each symbol for which we should give a warning, make a note
// on the symbol.
void
note_warnings(Symbol_table* symtab);
// Issue a warning for a reference to SYM at LOCATION.
void
issue_warning(Symbol* sym, const std::string& location) const;
private:
Warnings(const Warnings&);
Warnings& operator=(const Warnings&);
// What we need to know to get the warning text.
struct Warning_location
{
// The object the warning is in.
Object* object;
// The index of the warning section.
unsigned int shndx;
// The warning text if we have already loaded it.
std::string text;
Warning_location()
: object(NULL), shndx(0), text()
{ }
void
set(Object* o, unsigned int s)
{
this->object = o;
this->shndx = s;
}
void
set_text(const char* t, off_t l)
{ this->text.assign(t, l); }
};
// A mapping from warning symbol names (canonicalized in
// Symbol_table's namepool_ field) to
typedef Unordered_map<const char*, Warning_location> Warning_table;
Warning_table warnings_;
};
// The main linker symbol table.
class Symbol_table
{
public:
Symbol_table();
~Symbol_table();
// Add COUNT external symbols from the relocatable object OBJECT to
// the symbol table. SYMS is the symbols, SYM_NAMES is their names,
// SYM_NAME_SIZE is the size of SYM_NAMES. This sets SYMPOINTERS to
// point to the symbols in the symbol table.
template<int size, bool big_endian>
void
add_from_object(Relobj* object, const unsigned char* syms,
size_t count, const char* sym_names, size_t sym_name_size,
Symbol** sympointers);
// Define a special symbol.
template<int size, bool big_endian>
Sized_symbol<size>*
define_special_symbol(Target* target, const char* name, bool only_if_ref
ACCEPT_SIZE_ENDIAN);
// Define a special symbol based on an Output_data. It is a
// multiple definition error if this symbol is already defined.
void
define_in_output_data(Target*, const char* name, Output_data*,
uint64_t value, uint64_t symsize,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
bool offset_is_from_end, bool only_if_ref);
// Define a special symbol based on an Output_segment. It is a
// multiple definition error if this symbol is already defined.
void
define_in_output_segment(Target*, const char* name, Output_segment*,
uint64_t value, uint64_t symsize,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
Symbol::Segment_offset_base, bool only_if_ref);
// Define a special symbol with a constant value. It is a multiple
// definition error if this symbol is already defined.
void
define_as_constant(Target*, const char* name, uint64_t value,
uint64_t symsize, elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
bool only_if_ref);
// Define a set of symbols in output sections.
void
define_symbols(const Layout*, Target*, int count,
const Define_symbol_in_section*);
// Define a set of symbols in output segments.
void
define_symbols(const Layout*, Target*, int count,
const Define_symbol_in_segment*);
// Look up a symbol.
Symbol*
lookup(const char*, const char* version = NULL) const;
// Return the real symbol associated with the forwarder symbol FROM.
Symbol*
resolve_forwards(Symbol* from) const;
// Return the size of the symbols in the table.
int
get_size() const
{ return this->size_; }
// Return the sized version of a symbol in this table.
template<int size>
Sized_symbol<size>*
get_sized_symbol(Symbol* ACCEPT_SIZE) const;
template<int size>
const Sized_symbol<size>*
get_sized_symbol(const Symbol* ACCEPT_SIZE) const;
// Return the count of undefined symbols seen.
int
saw_undefined() const
{ return this->saw_undefined_; }
// Allocate the common symbols
void
allocate_commons(const General_options&, Layout*);
// Add a warning for symbol NAME in section SHNDX in object OBJ.
void
add_warning(const char* name, Object* obj, unsigned int shndx)
{ this->warnings_.add_warning(this, name, obj, shndx); }
// Canonicalize a symbol name for use in the hash table.
const char*
canonicalize_name(const char* name)
{ return this->namepool_.add(name, NULL); }
// Possibly issue a warning for a reference to SYM at LOCATION which
// is in OBJ.
void
issue_warning(Symbol* sym, const std::string& location) const
{ this->warnings_.issue_warning(sym, location); }
// Finalize the symbol table after we have set the final addresses
// of all the input sections. This sets the final symbol values and
// adds the names to *POOL. It records the file offset OFF, and
// returns the new file offset.
off_t
finalize(off_t, Stringpool*);
// Write out the global symbols.
void
write_globals(const Target*, const Stringpool*, Output_file*) const;
private:
Symbol_table(const Symbol_table&);
Symbol_table& operator=(const Symbol_table&);
// Set the size of the symbols in the table.
void
set_size(int size)
{ this->size_ = size; }
// Make FROM a forwarder symbol to TO.
void
make_forwarder(Symbol* from, Symbol* to);
// Add a symbol.
template<int size, bool big_endian>
Symbol*
add_from_object(Object*, const char *name, Stringpool::Key name_key,
const char *version, Stringpool::Key version_key,
bool def, const elfcpp::Sym<size, big_endian>& sym);
// Resolve symbols.
template<int size, bool big_endian>
static void
resolve(Sized_symbol<size>* to,
const elfcpp::Sym<size, big_endian>& sym,
Object*);
template<int size, bool big_endian>
static void
resolve(Sized_symbol<size>* to, const Sized_symbol<size>* from
ACCEPT_SIZE_ENDIAN);
// Define a symbol in an Output_data, sized version.
template<int size>
void
do_define_in_output_data(Target*, const char* name, Output_data*,
typename elfcpp::Elf_types<size>::Elf_Addr value,
typename elfcpp::Elf_types<size>::Elf_WXword ssize,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
bool offset_is_from_end, bool only_if_ref);
// Define a symbol in an Output_segment, sized version.
template<int size>
void
do_define_in_output_segment(
Target*, const char* name, Output_segment* os,
typename elfcpp::Elf_types<size>::Elf_Addr value,
typename elfcpp::Elf_types<size>::Elf_WXword ssize,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
Symbol::Segment_offset_base offset_base, bool only_if_ref);
// Define a symbol as a constant, sized version.
template<int size>
void
do_define_as_constant(
Target*, const char* name,
typename elfcpp::Elf_types<size>::Elf_Addr value,
typename elfcpp::Elf_types<size>::Elf_WXword ssize,
elfcpp::STT type, elfcpp::STB binding,
elfcpp::STV visibility, unsigned char nonvis,
bool only_if_ref);
// Allocate the common symbols, sized version.
template<int size>
void
do_allocate_commons(const General_options&, Layout*);
// Finalize symbols specialized for size.
template<int size>
off_t
sized_finalize(off_t, Stringpool*);
// Write globals specialized for size and endianness.
template<int size, bool big_endian>
void
sized_write_globals(const Target*, const Stringpool*, Output_file*) const;
// The type of the symbol hash table.
typedef std::pair<Stringpool::Key, Stringpool::Key> Symbol_table_key;
struct Symbol_table_hash
{
size_t
operator()(const Symbol_table_key&) const;
};
struct Symbol_table_eq
{
bool
operator()(const Symbol_table_key&, const Symbol_table_key&) const;
};
typedef Unordered_map<Symbol_table_key, Symbol*, Symbol_table_hash,
Symbol_table_eq> Symbol_table_type;
// The type of the list of common symbols.
typedef std::vector<Symbol*> Commons_type;
// The size of the symbols in the symbol table (32 or 64).
int size_;
// We increment this every time we see a new undefined symbol, for
// use in archive groups.
int saw_undefined_;
// The file offset within the output symtab section where we should
// write the table.
off_t offset_;
// The number of global symbols we want to write out.
size_t output_count_;
// The symbol hash table.
Symbol_table_type table_;
// A pool of symbol names. This is used for all global symbols.
// Entries in the hash table point into this pool.
Stringpool namepool_;
// Forwarding symbols.
Unordered_map<Symbol*, Symbol*> forwarders_;
// We don't expect there to be very many common symbols, so we keep
// a list of them. When we find a common symbol we add it to this
// list. It is possible that by the time we process the list the
// symbol is no longer a common symbol. It may also have become a
// forwarder.
Commons_type commons_;
// Manage symbol warnings.
Warnings warnings_;
};
// We inline get_sized_symbol for efficiency.
template<int size>
Sized_symbol<size>*
Symbol_table::get_sized_symbol(Symbol* sym ACCEPT_SIZE) const
{
assert(size == this->get_size());
return static_cast<Sized_symbol<size>*>(sym);
}
template<int size>
const Sized_symbol<size>*
Symbol_table::get_sized_symbol(const Symbol* sym ACCEPT_SIZE) const
{
assert(size == this->get_size());
return static_cast<const Sized_symbol<size>*>(sym);
}
} // End namespace gold.
#endif // !defined(GOLD_SYMTAB_H)