binutils-gdb/gold/object.h

887 lines
25 KiB
C++

// object.h -- support for an object file for linking in gold -*- C++ -*-
// Copyright 2006, 2007 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#ifndef GOLD_OBJECT_H
#define GOLD_OBJECT_H
#include <string>
#include <vector>
#include "elfcpp.h"
#include "elfcpp_file.h"
#include "fileread.h"
#include "target.h"
namespace gold
{
class General_options;
class Layout;
class Output_section;
class Output_file;
class Dynobj;
template<typename Stringpool_char>
class Stringpool_template;
// Data to pass from read_symbols() to add_symbols().
struct Read_symbols_data
{
// Section headers.
File_view* section_headers;
// Section names.
File_view* section_names;
// Size of section name data in bytes.
off_t section_names_size;
// Symbol data.
File_view* symbols;
// Size of symbol data in bytes.
off_t symbols_size;
// Symbol names.
File_view* symbol_names;
// Size of symbol name data in bytes.
off_t symbol_names_size;
// Version information. This is only used on dynamic objects.
// Version symbol data (from SHT_GNU_versym section).
File_view* versym;
off_t versym_size;
// Version definition data (from SHT_GNU_verdef section).
File_view* verdef;
off_t verdef_size;
unsigned int verdef_info;
// Needed version data (from SHT_GNU_verneed section).
File_view* verneed;
off_t verneed_size;
unsigned int verneed_info;
};
// Data about a single relocation section. This is read in
// read_relocs and processed in scan_relocs.
struct Section_relocs
{
// Index of reloc section.
unsigned int reloc_shndx;
// Index of section that relocs apply to.
unsigned int data_shndx;
// Contents of reloc section.
File_view* contents;
// Reloc section type.
unsigned int sh_type;
// Number of reloc entries.
size_t reloc_count;
};
// Relocations in an object file. This is read in read_relocs and
// processed in scan_relocs.
struct Read_relocs_data
{
typedef std::vector<Section_relocs> Relocs_list;
// The relocations.
Relocs_list relocs;
// The local symbols.
File_view* local_symbols;
};
// Object is an abstract base class which represents either a 32-bit
// or a 64-bit input object. This can be a regular object file
// (ET_REL) or a shared object (ET_DYN).
class Object
{
public:
// NAME is the name of the object as we would report it to the user
// (e.g., libfoo.a(bar.o) if this is in an archive. INPUT_FILE is
// used to read the file. OFFSET is the offset within the input
// file--0 for a .o or .so file, something else for a .a file.
Object(const std::string& name, Input_file* input_file, bool is_dynamic,
off_t offset = 0)
: name_(name), input_file_(input_file), offset_(offset), shnum_(-1U),
is_dynamic_(is_dynamic), target_(NULL)
{ }
virtual ~Object()
{ }
// Return the name of the object as we would report it to the tuser.
const std::string&
name() const
{ return this->name_; }
// Get the offset into the file.
off_t
offset() const
{ return this->offset_; }
// Return whether this is a dynamic object.
bool
is_dynamic() const
{ return this->is_dynamic_; }
// Return the target structure associated with this object.
Target*
target() const
{ return this->target_; }
// Lock the underlying file.
void
lock()
{ this->input_file_->file().lock(); }
// Unlock the underlying file.
void
unlock()
{ this->input_file_->file().unlock(); }
// Return whether the underlying file is locked.
bool
is_locked() const
{ return this->input_file_->file().is_locked(); }
// Return the sized target structure associated with this object.
// This is like the target method but it returns a pointer of
// appropriate checked type.
template<int size, bool big_endian>
Sized_target<size, big_endian>*
sized_target(ACCEPT_SIZE_ENDIAN_ONLY);
// Get the number of sections.
unsigned int
shnum() const
{ return this->shnum_; }
// Return a view of the contents of a section. Set *PLEN to the
// size. CACHE is a hint as in File_read::get_view.
const unsigned char*
section_contents(unsigned int shndx, off_t* plen, bool cache);
// Return the name of a section given a section index. This is only
// used for error messages.
std::string
section_name(unsigned int shndx)
{ return this->do_section_name(shndx); }
// Return the section flags given a section index.
uint64_t
section_flags(unsigned int shndx)
{ return this->do_section_flags(shndx); }
// Read the symbol information.
void
read_symbols(Read_symbols_data* sd)
{ return this->do_read_symbols(sd); }
// Pass sections which should be included in the link to the Layout
// object, and record where the sections go in the output file.
void
layout(Symbol_table* symtab, Layout* layout, Read_symbols_data* sd)
{ this->do_layout(symtab, layout, sd); }
// Add symbol information to the global symbol table.
void
add_symbols(Symbol_table* symtab, Read_symbols_data* sd)
{ this->do_add_symbols(symtab, sd); }
// Functions and types for the elfcpp::Elf_file interface. This
// permit us to use Object as the File template parameter for
// elfcpp::Elf_file.
// The View class is returned by view. It must support a single
// method, data(). This is trivial, because get_view does what we
// need.
class View
{
public:
View(const unsigned char* p)
: p_(p)
{ }
const unsigned char*
data() const
{ return this->p_; }
private:
const unsigned char* p_;
};
// Return a View.
View
view(off_t file_offset, off_t data_size)
{ return View(this->get_view(file_offset, data_size, true)); }
// Report an error.
void
error(const char* format, ...) ATTRIBUTE_PRINTF_2;
// A location in the file.
struct Location
{
off_t file_offset;
off_t data_size;
Location(off_t fo, off_t ds)
: file_offset(fo), data_size(ds)
{ }
};
// Get a View given a Location.
View view(Location loc)
{ return View(this->get_view(loc.file_offset, loc.data_size, true)); }
protected:
// Read the symbols--implemented by child class.
virtual void
do_read_symbols(Read_symbols_data*) = 0;
// Lay out sections--implemented by child class.
virtual void
do_layout(Symbol_table*, Layout*, Read_symbols_data*) = 0;
// Add symbol information to the global symbol table--implemented by
// child class.
virtual void
do_add_symbols(Symbol_table*, Read_symbols_data*) = 0;
// Return the location of the contents of a section. Implemented by
// child class.
virtual Location
do_section_contents(unsigned int shndx) = 0;
// Get the name of a section--implemented by child class.
virtual std::string
do_section_name(unsigned int shndx) = 0;
// Get section flags--implemented by child class.
virtual uint64_t
do_section_flags(unsigned int shndx) = 0;
// Get the file.
Input_file*
input_file() const
{ return this->input_file_; }
// Get a view into the underlying file.
const unsigned char*
get_view(off_t start, off_t size, bool cache)
{
return this->input_file_->file().get_view(start + this->offset_, size,
cache);
}
// Get a lasting view into the underlying file.
File_view*
get_lasting_view(off_t start, off_t size, bool cache)
{
return this->input_file_->file().get_lasting_view(start + this->offset_,
size, cache);
}
// Read data from the underlying file.
void
read(off_t start, off_t size, void* p)
{ this->input_file_->file().read(start + this->offset_, size, p); }
// Set the target.
void
set_target(int machine, int size, bool big_endian, int osabi,
int abiversion);
// Set the number of sections.
void
set_shnum(int shnum)
{ this->shnum_ = shnum; }
// Functions used by both Sized_relobj and Sized_dynobj.
// Read the section data into a Read_symbols_data object.
template<int size, bool big_endian>
void
read_section_data(elfcpp::Elf_file<size, big_endian, Object>*,
Read_symbols_data*);
// If NAME is the name of a special .gnu.warning section, arrange
// for the warning to be issued. SHNDX is the section index.
// Return whether it is a warning section.
bool
handle_gnu_warning_section(const char* name, unsigned int shndx,
Symbol_table*);
private:
// This class may not be copied.
Object(const Object&);
Object& operator=(const Object&);
// Name of object as printed to user.
std::string name_;
// For reading the file.
Input_file* input_file_;
// Offset within the file--0 for an object file, non-0 for an
// archive.
off_t offset_;
// Number of input sections.
unsigned int shnum_;
// Whether this is a dynamic object.
bool is_dynamic_;
// Target functions--may be NULL if the target is not known.
Target* target_;
};
// Implement sized_target inline for efficiency. This approach breaks
// static type checking, but is made safe using asserts.
template<int size, bool big_endian>
inline Sized_target<size, big_endian>*
Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY)
{
gold_assert(this->target_->get_size() == size);
gold_assert(this->target_->is_big_endian() ? big_endian : !big_endian);
return static_cast<Sized_target<size, big_endian>*>(this->target_);
}
// A regular object (ET_REL). This is an abstract base class itself.
// The implementation is the template class Sized_relobj.
class Relobj : public Object
{
public:
Relobj(const std::string& name, Input_file* input_file, off_t offset = 0)
: Object(name, input_file, false, offset)
{ }
// Read the relocs.
void
read_relocs(Read_relocs_data* rd)
{ return this->do_read_relocs(rd); }
// Scan the relocs and adjust the symbol table.
void
scan_relocs(const General_options& options, Symbol_table* symtab,
Layout* layout, Read_relocs_data* rd)
{ return this->do_scan_relocs(options, symtab, layout, rd); }
// Initial local symbol processing: set the offset where local
// symbol information will be stored; add local symbol names to
// *POOL; return the new local symbol index.
unsigned int
finalize_local_symbols(unsigned int index, off_t off,
Stringpool_template<char>* pool)
{ return this->do_finalize_local_symbols(index, off, pool); }
// Relocate the input sections and write out the local symbols.
void
relocate(const General_options& options, const Symbol_table* symtab,
const Layout* layout, Output_file* of)
{ return this->do_relocate(options, symtab, layout, of); }
// Return whether an input section is being included in the link.
bool
is_section_included(unsigned int shndx) const
{
gold_assert(shndx < this->map_to_output_.size());
return this->map_to_output_[shndx].output_section != NULL;
}
// Given a section index, return the corresponding Output_section
// (which will be NULL if the section is not included in the link)
// and set *POFF to the offset within that section.
inline Output_section*
output_section(unsigned int shndx, off_t* poff) const;
// Set the offset of an input section within its output section.
void
set_section_offset(unsigned int shndx, off_t off)
{
gold_assert(shndx < this->map_to_output_.size());
this->map_to_output_[shndx].offset = off;
}
protected:
// What we need to know to map an input section to an output
// section. We keep an array of these, one for each input section,
// indexed by the input section number.
struct Map_to_output
{
// The output section. This is NULL if the input section is to be
// discarded.
Output_section* output_section;
// The offset within the output section. This is -1 if the
// section requires special handling.
off_t offset;
};
// Read the relocs--implemented by child class.
virtual void
do_read_relocs(Read_relocs_data*) = 0;
// Scan the relocs--implemented by child class.
virtual void
do_scan_relocs(const General_options&, Symbol_table*, Layout*,
Read_relocs_data*) = 0;
// Finalize local symbols--implemented by child class.
virtual unsigned int
do_finalize_local_symbols(unsigned int, off_t,
Stringpool_template<char>*) = 0;
// Relocate the input sections and write out the local
// symbols--implemented by child class.
virtual void
do_relocate(const General_options& options, const Symbol_table* symtab,
const Layout*, Output_file* of) = 0;
// Return the vector mapping input sections to output sections.
std::vector<Map_to_output>&
map_to_output()
{ return this->map_to_output_; }
const std::vector<Map_to_output>&
map_to_output() const
{ return this->map_to_output_; }
private:
// Mapping from input sections to output section.
std::vector<Map_to_output> map_to_output_;
};
// Implement Object::output_section inline for efficiency.
inline Output_section*
Relobj::output_section(unsigned int shndx, off_t* poff) const
{
gold_assert(shndx < this->map_to_output_.size());
const Map_to_output& mo(this->map_to_output_[shndx]);
*poff = mo.offset;
return mo.output_section;
}
// This POD class is holds the value of a symbol. This is used for
// local symbols, and for all symbols during relocation processing.
// In order to process relocs we need to be able to handle SHF_MERGE
// sections correctly.
template<int size>
class Symbol_value
{
public:
typedef typename elfcpp::Elf_types<size>::Elf_Addr Value;
Symbol_value()
: output_symtab_index_(0), input_shndx_(0), is_section_symbol_(false),
needs_output_address_(false), value_(0)
{ }
// Get the value of this symbol. OBJECT is the object in which this
// symbol is defined, and ADDEND is an addend to add to the value.
template<bool big_endian>
Value
value(const Sized_relobj<size, big_endian>* object, Value addend) const
{
if (!this->needs_output_address_)
return this->value_ + addend;
return object->local_value(this->input_shndx_, this->value_,
this->is_section_symbol_, addend);
}
// Set the value of this symbol in the output symbol table.
void
set_output_value(Value value)
{
this->value_ = value;
this->needs_output_address_ = false;
}
// If this symbol is mapped to an output section which requires
// special handling to determine the output value, we store the
// value of the symbol in the input file. This is used for
// SHF_MERGE sections.
void
set_input_value(Value value)
{
this->value_ = value;
this->needs_output_address_ = true;
}
// Return whether this symbol should go into the output symbol
// table.
bool
needs_output_symtab_entry() const
{
gold_assert(this->output_symtab_index_ != 0);
return this->output_symtab_index_ != -1U;
}
// Return the index in the output symbol table.
unsigned int
output_symtab_index() const
{
gold_assert(this->output_symtab_index_ != 0);
return this->output_symtab_index_;
}
// Set the index in the output symbol table.
void
set_output_symtab_index(unsigned int i)
{
gold_assert(this->output_symtab_index_ == 0);
this->output_symtab_index_ = i;
}
// Record that this symbol should not go into the output symbol
// table.
void
set_no_output_symtab_entry()
{
gold_assert(this->output_symtab_index_ == 0);
this->output_symtab_index_ = -1U;
}
// Set the index of the input section in the input file.
void
set_input_shndx(unsigned int i)
{ this->input_shndx_ = i; }
// Record that this is a section symbol.
void
set_is_section_symbol()
{ this->is_section_symbol_ = true; }
private:
// The index of this local symbol in the output symbol table. This
// will be -1 if the symbol should not go into the symbol table.
unsigned int output_symtab_index_;
// The section index in the input file in which this symbol is
// defined.
unsigned int input_shndx_ : 30;
// Whether this is a STT_SECTION symbol.
bool is_section_symbol_ : 1;
// Whether getting the value of this symbol requires calling an
// Output_section method. For example, this will be true of a
// symbol in a SHF_MERGE section.
bool needs_output_address_ : 1;
// The value of the symbol. If !needs_output_address_, this is the
// value in the output file. If needs_output_address_, this is the
// value in the input file.
Value value_;
};
// A regular object file. This is size and endian specific.
template<int size, bool big_endian>
class Sized_relobj : public Relobj
{
public:
typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
typedef std::vector<Symbol_value<size> > Local_values;
Sized_relobj(const std::string& name, Input_file* input_file, off_t offset,
const typename elfcpp::Ehdr<size, big_endian>&);
~Sized_relobj();
// Set up the object file based on the ELF header.
void
setup(const typename elfcpp::Ehdr<size, big_endian>&);
// Return the index of local symbol SYM in the ordinary symbol
// table. A value of -1U means that the symbol is not being output.
unsigned int
symtab_index(unsigned int sym) const
{
gold_assert(sym < this->local_values_.size());
return this->local_values_[sym].output_symtab_index();
}
// Return the appropriate Sized_target structure.
Sized_target<size, big_endian>*
sized_target()
{
return this->Object::sized_target
SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
}
// Return the value of the local symbol symndx.
Address
local_symbol_value(unsigned int symndx) const;
// Return the value of a local symbol defined in input section
// SHNDX, with value VALUE, adding addend ADDEND. IS_SECTION_SYMBOL
// indicates whether the symbol is a section symbol. This handles
// SHF_MERGE sections.
Address
local_value(unsigned int shndx, Address value, bool is_section_symbol,
Address addend) const;
// Return whether the local symbol SYMNDX has a GOT offset.
bool
local_has_got_offset(unsigned int symndx) const
{
return (this->local_got_offsets_.find(symndx)
!= this->local_got_offsets_.end());
}
// Return the GOT offset of the local symbol SYMNDX.
unsigned int
local_got_offset(unsigned int symndx) const
{
Local_got_offsets::const_iterator p =
this->local_got_offsets_.find(symndx);
gold_assert(p != this->local_got_offsets_.end());
return p->second;
}
// Set the GOT offset of the local symbol SYMNDX to GOT_OFFSET.
void
set_local_got_offset(unsigned int symndx, unsigned int got_offset)
{
std::pair<Local_got_offsets::iterator, bool> ins =
this->local_got_offsets_.insert(std::make_pair(symndx, got_offset));
gold_assert(ins.second);
}
// Read the symbols.
void
do_read_symbols(Read_symbols_data*);
// Lay out the input sections.
void
do_layout(Symbol_table*, Layout*, Read_symbols_data*);
// Add the symbols to the symbol table.
void
do_add_symbols(Symbol_table*, Read_symbols_data*);
// Read the relocs.
void
do_read_relocs(Read_relocs_data*);
// Scan the relocs and adjust the symbol table.
void
do_scan_relocs(const General_options&, Symbol_table*, Layout*,
Read_relocs_data*);
// Finalize the local symbols.
unsigned int
do_finalize_local_symbols(unsigned int, off_t,
Stringpool_template<char>*);
// Relocate the input sections and write out the local symbols.
void
do_relocate(const General_options& options, const Symbol_table* symtab,
const Layout*, Output_file* of);
// Get the name of a section.
std::string
do_section_name(unsigned int shndx)
{ return this->elf_file_.section_name(shndx); }
// Return the location of the contents of a section.
Object::Location
do_section_contents(unsigned int shndx)
{ return this->elf_file_.section_contents(shndx); }
// Return section flags.
uint64_t
do_section_flags(unsigned int shndx)
{ return this->elf_file_.section_flags(shndx); }
private:
// For convenience.
typedef Sized_relobj<size, big_endian> This;
static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
typedef elfcpp::Shdr<size, big_endian> Shdr;
// Find the SHT_SYMTAB section, given the section headers.
void
find_symtab(const unsigned char* pshdrs);
// Whether to include a section group in the link.
bool
include_section_group(Layout*, unsigned int,
const elfcpp::Shdr<size, big_endian>&,
std::vector<bool>*);
// Whether to include a linkonce section in the link.
bool
include_linkonce_section(Layout*, const char*,
const elfcpp::Shdr<size, big_endian>&);
// Views and sizes when relocating.
struct View_size
{
unsigned char* view;
typename elfcpp::Elf_types<size>::Elf_Addr address;
off_t offset;
off_t view_size;
};
typedef std::vector<View_size> Views;
// Write section data to the output file. Record the views and
// sizes in VIEWS for use when relocating.
void
write_sections(const unsigned char* pshdrs, Output_file*, Views*);
// Relocate the sections in the output file.
void
relocate_sections(const General_options& options, const Symbol_table*,
const Layout*, const unsigned char* pshdrs, Views*);
// Write out the local symbols.
void
write_local_symbols(Output_file*,
const Stringpool_template<char>*);
// The GOT offsets of local symbols.
typedef Unordered_map<unsigned int, unsigned int> Local_got_offsets;
// General access to the ELF file.
elfcpp::Elf_file<size, big_endian, Object> elf_file_;
// Index of SHT_SYMTAB section.
unsigned int symtab_shndx_;
// The number of local symbols.
unsigned int local_symbol_count_;
// The number of local symbols which go into the output file.
unsigned int output_local_symbol_count_;
// The entries in the symbol table for the external symbols.
Symbol** symbols_;
// File offset for local symbols.
off_t local_symbol_offset_;
// Values of local symbols.
Local_values local_values_;
// GOT offsets for local symbols, indexed by symbol number.
Local_got_offsets local_got_offsets_;
};
// A class to manage the list of all objects.
class Input_objects
{
public:
Input_objects()
: relobj_list_(), dynobj_list_(), target_(NULL), sonames_()
{ }
// The type of the list of input relocateable objects.
typedef std::vector<Relobj*> Relobj_list;
typedef Relobj_list::const_iterator Relobj_iterator;
// The type of the list of input dynamic objects.
typedef std::vector<Dynobj*> Dynobj_list;
typedef Dynobj_list::const_iterator Dynobj_iterator;
// Add an object to the list. Return true if all is well, or false
// if this object should be ignored.
bool
add_object(Object*);
// Get the target we should use for the output file.
Target*
target() const
{ return this->target_; }
// Iterate over all regular objects.
Relobj_iterator
relobj_begin() const
{ return this->relobj_list_.begin(); }
Relobj_iterator
relobj_end() const
{ return this->relobj_list_.end(); }
// Iterate over all dynamic objects.
Dynobj_iterator
dynobj_begin() const
{ return this->dynobj_list_.begin(); }
Dynobj_iterator
dynobj_end() const
{ return this->dynobj_list_.end(); }
// Return whether we have seen any dynamic objects.
bool
any_dynamic() const
{ return !this->dynobj_list_.empty(); }
private:
Input_objects(const Input_objects&);
Input_objects& operator=(const Input_objects&);
// The list of ordinary objects included in the link.
Relobj_list relobj_list_;
// The list of dynamic objects included in the link.
Dynobj_list dynobj_list_;
// The target.
Target* target_;
// SONAMEs that we have seen.
Unordered_set<std::string> sonames_;
};
// Some of the information we pass to the relocation routines. We
// group this together to avoid passing a dozen different arguments.
template<int size, bool big_endian>
struct Relocate_info
{
// Command line options.
const General_options* options;
// Symbol table.
const Symbol_table* symtab;
// Layout.
const Layout* layout;
// Object being relocated.
Sized_relobj<size, big_endian>* object;
// Number of local symbols.
unsigned int local_symbol_count;
// Values of local symbols.
const typename Sized_relobj<size, big_endian>::Local_values* local_values;
// Global symbols.
const Symbol* const * symbols;
// Section index of relocation section.
unsigned int reloc_shndx;
// Section index of section being relocated.
unsigned int data_shndx;
// Return a string showing the location of a relocation. This is
// only used for error messages.
std::string
location(size_t relnum, off_t reloffset) const;
};
// Return an Object appropriate for the input file. P is BYTES long,
// and holds the ELF header.
extern Object*
make_elf_object(const std::string& name, Input_file*,
off_t offset, const unsigned char* p,
off_t bytes);
} // end namespace gold
#endif // !defined(GOLD_OBJECT_H)