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|
// reloc.h -- relocate input files for 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_RELOC_H
#define GOLD_RELOC_H
#include <vector>
#include <byteswap.h>
#include "elfcpp.h"
#include "workqueue.h"
namespace gold
{
class General_options;
class Object;
class Relobj;
class Read_relocs_data;
class Symbol;
class Layout;
class Output_data;
class Output_section;
template<int size>
class Sized_symbol;
template<int size, bool big_endian>
class Sized_relobj;
template<int size>
class Symbol_value;
template<int sh_type, bool dynamic, int size, bool big_endian>
class Output_data_reloc;
// A class to read the relocations for an object file, and then queue
// up a task to see if they require any GOT/PLT/COPY relocations in
// the symbol table.
class Read_relocs : public Task
{
public:
// SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be
// unblocked when the Scan_relocs task completes.
Read_relocs(const General_options& options, Symbol_table* symtab,
Layout* layout, Relobj* object, Task_token* symtab_lock,
Task_token* blocker)
: options_(options), symtab_(symtab), layout_(layout), object_(object),
symtab_lock_(symtab_lock), blocker_(blocker)
{ }
// The standard Task methods.
Task_token*
is_runnable();
void
locks(Task_locker*);
void
run(Workqueue*);
std::string
get_name() const;
private:
const General_options& options_;
Symbol_table* symtab_;
Layout* layout_;
Relobj* object_;
Task_token* symtab_lock_;
Task_token* blocker_;
};
// Scan the relocations for an object to see if they require any
// GOT/PLT/COPY relocations.
class Scan_relocs : public Task
{
public:
// SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be
// unblocked when the task completes.
Scan_relocs(const General_options& options, Symbol_table* symtab,
Layout* layout, Relobj* object, Read_relocs_data* rd,
Task_token* symtab_lock, Task_token* blocker)
: options_(options), symtab_(symtab), layout_(layout), object_(object),
rd_(rd), symtab_lock_(symtab_lock), blocker_(blocker)
{ }
// The standard Task methods.
Task_token*
is_runnable();
void
locks(Task_locker*);
void
run(Workqueue*);
std::string
get_name() const;
private:
const General_options& options_;
Symbol_table* symtab_;
Layout* layout_;
Relobj* object_;
Read_relocs_data* rd_;
Task_token* symtab_lock_;
Task_token* blocker_;
};
// A class to perform all the relocations for an object file.
class Relocate_task : public Task
{
public:
Relocate_task(const General_options& options, const Symbol_table* symtab,
const Layout* layout, Relobj* object, Output_file* of,
Task_token* input_sections_blocker,
Task_token* output_sections_blocker, Task_token* final_blocker)
: options_(options), symtab_(symtab), layout_(layout), object_(object),
of_(of), input_sections_blocker_(input_sections_blocker),
output_sections_blocker_(output_sections_blocker),
final_blocker_(final_blocker)
{ }
// The standard Task methods.
Task_token*
is_runnable();
void
locks(Task_locker*);
void
run(Workqueue*);
std::string
get_name() const;
private:
const General_options& options_;
const Symbol_table* symtab_;
const Layout* layout_;
Relobj* object_;
Output_file* of_;
Task_token* input_sections_blocker_;
Task_token* output_sections_blocker_;
Task_token* final_blocker_;
};
// During a relocatable link, this class records how relocations
// should be handled for a single input reloc section. An instance of
// this class is created while scanning relocs, and it is used while
// processing relocs.
class Relocatable_relocs
{
public:
// We use a vector of unsigned char to indicate how the input relocs
// should be handled. Each element is one of the following values.
// We create this vector when we initially scan the relocations.
enum Reloc_strategy
{
// Copy the input reloc. Don't modify it other than updating the
// r_offset field and the r_sym part of the r_info field.
RELOC_COPY,
// Copy the input reloc which is against an STT_SECTION symbol.
// Update the r_offset and r_sym part of the r_info field. Adjust
// the addend by subtracting the value of the old local symbol and
// adding the value of the new local symbol. The addend is in the
// SHT_RELA reloc and the contents of the data section do not need
// to be changed.
RELOC_ADJUST_FOR_SECTION_RELA,
// Like RELOC_ADJUST_FOR_SECTION_RELA but the contents of the
// section need to be changed. The number indicates the number of
// bytes in the addend in the section contents.
RELOC_ADJUST_FOR_SECTION_1,
RELOC_ADJUST_FOR_SECTION_2,
RELOC_ADJUST_FOR_SECTION_4,
RELOC_ADJUST_FOR_SECTION_8,
// Discard the input reloc--process it completely when relocating
// the data section contents.
RELOC_DISCARD,
// An input reloc which is not discarded, but which requires
// target specific processing in order to update it.
RELOC_SPECIAL
};
Relocatable_relocs()
: reloc_strategies_(), output_reloc_count_(0), posd_(NULL)
{ }
// Record the number of relocs.
void
set_reloc_count(size_t reloc_count)
{ this->reloc_strategies_.reserve(reloc_count); }
// Record what to do for the next reloc.
void
set_next_reloc_strategy(Reloc_strategy strategy)
{
this->reloc_strategies_.push_back(static_cast<unsigned char>(strategy));
if (strategy != RELOC_DISCARD)
++this->output_reloc_count_;
}
// Record the Output_data associated with this reloc section.
void
set_output_data(Output_data* posd)
{
gold_assert(this->posd_ == NULL);
this->posd_ = posd;
}
// Return the Output_data associated with this reloc section.
Output_data*
output_data() const
{ return this->posd_; }
// Return what to do for reloc I.
Reloc_strategy
strategy(unsigned int i) const
{
gold_assert(i < this->reloc_strategies_.size());
return static_cast<Reloc_strategy>(this->reloc_strategies_[i]);
}
// Return the number of relocations to create in the output file.
size_t
output_reloc_count() const
{ return this->output_reloc_count_; }
private:
typedef std::vector<unsigned char> Reloc_strategies;
// The strategies for the input reloc. There is one entry in this
// vector for each relocation in the input section.
Reloc_strategies reloc_strategies_;
// The number of relocations to be created in the output file.
size_t output_reloc_count_;
// The output data structure associated with this relocation.
Output_data* posd_;
};
// Standard relocation routines which are used on many targets. Here
// SIZE and BIG_ENDIAN refer to the target, not the relocation type.
template<int size, bool big_endian>
class Relocate_functions
{
private:
// Do a simple relocation with the addend in the section contents.
// VALSIZE is the size of the value.
template<int valsize>
static inline void
rel(unsigned char* view,
typename elfcpp::Swap<valsize, big_endian>::Valtype value)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value);
}
// Do a simple relocation using a Symbol_value with the addend in
// the section contents. VALSIZE is the size of the value to
// relocate.
template<int valsize>
static inline void
rel(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
x = psymval->value(object, x);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
}
// Do a simple relocation with the addend in the relocation.
// VALSIZE is the size of the value.
template<int valsize>
static inline void
rela(unsigned char* view,
typename elfcpp::Swap<valsize, big_endian>::Valtype value,
typename elfcpp::Swap<valsize, big_endian>::Valtype addend)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
elfcpp::Swap<valsize, big_endian>::writeval(wv, value + addend);
}
// Do a simple relocation using a symbol value with the addend in
// the relocation. VALSIZE is the size of the value.
template<int valsize>
static inline void
rela(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Swap<valsize, big_endian>::Valtype addend)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = psymval->value(object, addend);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
}
// Do a simple PC relative relocation with the addend in the section
// contents. VALSIZE is the size of the value.
template<int valsize>
static inline void
pcrel(unsigned char* view,
typename elfcpp::Swap<valsize, big_endian>::Valtype value,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address);
}
// Do a simple PC relative relocation with a Symbol_value with the
// addend in the section contents. VALSIZE is the size of the
// value.
template<int valsize>
static inline void
pcrel(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
x = psymval->value(object, x);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
}
// Do a simple PC relative relocation with the addend in the
// relocation. VALSIZE is the size of the value.
template<int valsize>
static inline void
pcrela(unsigned char* view,
typename elfcpp::Swap<valsize, big_endian>::Valtype value,
typename elfcpp::Swap<valsize, big_endian>::Valtype addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
elfcpp::Swap<valsize, big_endian>::writeval(wv, value + addend - address);
}
// Do a simple PC relative relocation with a Symbol_value with the
// addend in the relocation. VALSIZE is the size of the value.
template<int valsize>
static inline void
pcrela(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Swap<valsize, big_endian>::Valtype addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{
typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
Valtype* wv = reinterpret_cast<Valtype*>(view);
Valtype x = psymval->value(object, addend);
elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
}
typedef Relocate_functions<size, big_endian> This;
public:
// Do a simple 8-bit REL relocation with the addend in the section
// contents.
static inline void
rel8(unsigned char* view, unsigned char value)
{ This::template rel<8>(view, value); }
static inline void
rel8(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval)
{ This::template rel<8>(view, object, psymval); }
// Do an 8-bit RELA relocation with the addend in the relocation.
static inline void
rela8(unsigned char* view, unsigned char value, unsigned char addend)
{ This::template rela<8>(view, value, addend); }
static inline void
rela8(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
unsigned char addend)
{ This::template rela<8>(view, object, psymval, addend); }
// Do a simple 8-bit PC relative relocation with the addend in the
// section contents.
static inline void
pcrel8(unsigned char* view, unsigned char value,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<8>(view, value, address); }
static inline void
pcrel8(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<8>(view, object, psymval, address); }
// Do a simple 8-bit PC relative RELA relocation with the addend in
// the reloc.
static inline void
pcrela8(unsigned char* view, unsigned char value, unsigned char addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<8>(view, value, addend, address); }
static inline void
pcrela8(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
unsigned char addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<8>(view, object, psymval, addend, address); }
// Do a simple 16-bit REL relocation with the addend in the section
// contents.
static inline void
rel16(unsigned char* view, elfcpp::Elf_Half value)
{ This::template rel<16>(view, value); }
static inline void
rel16(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval)
{ This::template rel<16>(view, object, psymval); }
// Do an 16-bit RELA relocation with the addend in the relocation.
static inline void
rela16(unsigned char* view, elfcpp::Elf_Half value, elfcpp::Elf_Half addend)
{ This::template rela<16>(view, value, addend); }
static inline void
rela16(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Half addend)
{ This::template rela<16>(view, object, psymval, addend); }
// Do a simple 16-bit PC relative REL relocation with the addend in
// the section contents.
static inline void
pcrel16(unsigned char* view, elfcpp::Elf_Half value,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<16>(view, value, address); }
static inline void
pcrel16(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<16>(view, object, psymval, address); }
// Do a simple 16-bit PC relative RELA relocation with the addend in
// the reloc.
static inline void
pcrela16(unsigned char* view, elfcpp::Elf_Half value,
elfcpp::Elf_Half addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<16>(view, value, addend, address); }
static inline void
pcrela16(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Half addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<16>(view, object, psymval, addend, address); }
// Do a simple 32-bit REL relocation with the addend in the section
// contents.
static inline void
rel32(unsigned char* view, elfcpp::Elf_Word value)
{ This::template rel<32>(view, value); }
static inline void
rel32(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval)
{ This::template rel<32>(view, object, psymval); }
// Do an 32-bit RELA relocation with the addend in the relocation.
static inline void
rela32(unsigned char* view, elfcpp::Elf_Word value, elfcpp::Elf_Word addend)
{ This::template rela<32>(view, value, addend); }
static inline void
rela32(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Word addend)
{ This::template rela<32>(view, object, psymval, addend); }
// Do a simple 32-bit PC relative REL relocation with the addend in
// the section contents.
static inline void
pcrel32(unsigned char* view, elfcpp::Elf_Word value,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<32>(view, value, address); }
static inline void
pcrel32(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<32>(view, object, psymval, address); }
// Do a simple 32-bit PC relative RELA relocation with the addend in
// the relocation.
static inline void
pcrela32(unsigned char* view, elfcpp::Elf_Word value,
elfcpp::Elf_Word addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<32>(view, value, addend, address); }
static inline void
pcrela32(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Word addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<32>(view, object, psymval, addend, address); }
// Do a simple 64-bit REL relocation with the addend in the section
// contents.
static inline void
rel64(unsigned char* view, elfcpp::Elf_Xword value)
{ This::template rel<64>(view, value); }
static inline void
rel64(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval)
{ This::template rel<64>(view, object, psymval); }
// Do a 64-bit RELA relocation with the addend in the relocation.
static inline void
rela64(unsigned char* view, elfcpp::Elf_Xword value,
elfcpp::Elf_Xword addend)
{ This::template rela<64>(view, value, addend); }
static inline void
rela64(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Xword addend)
{ This::template rela<64>(view, object, psymval, addend); }
// Do a simple 64-bit PC relative REL relocation with the addend in
// the section contents.
static inline void
pcrel64(unsigned char* view, elfcpp::Elf_Xword value,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<64>(view, value, address); }
static inline void
pcrel64(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrel<64>(view, object, psymval, address); }
// Do a simple 64-bit PC relative RELA relocation with the addend in
// the relocation.
static inline void
pcrela64(unsigned char* view, elfcpp::Elf_Xword value,
elfcpp::Elf_Xword addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<64>(view, value, addend, address); }
static inline void
pcrela64(unsigned char* view,
const Sized_relobj<size, big_endian>* object,
const Symbol_value<size>* psymval,
elfcpp::Elf_Xword addend,
typename elfcpp::Elf_types<size>::Elf_Addr address)
{ This::template pcrela<64>(view, object, psymval, addend, address); }
};
// We try to avoid COPY relocations when possible. A COPY relocation
// may be required when an executable refers to a variable defined in
// a shared library. COPY relocations are problematic because they
// tie the executable to the exact size of the variable in the shared
// library. We can avoid them if all the references to the variable
// are in a writeable section. In that case we can simply use dynamic
// relocations. However, when scanning relocs, we don't know when we
// see the relocation whether we will be forced to use a COPY
// relocation or not. So we have to save the relocation during the
// reloc scanning, and then emit it as a dynamic relocation if
// necessary. This class implements that. It is used by the target
// specific code.
template<int size, bool big_endian>
class Copy_relocs
{
public:
Copy_relocs()
: entries_()
{ }
// Return whether we need a COPY reloc for a reloc against GSYM,
// which is being applied to section SHNDX in OBJECT.
static bool
need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx,
Sized_symbol<size>* gsym);
// Save a Rel against SYM for possible emission later. SHNDX is the
// index of the section to which the reloc is being applied.
void
save(Symbol* sym, Relobj*, unsigned int shndx,
Output_section* output_section, const elfcpp::Rel<size, big_endian>&);
// Save a Rela against SYM for possible emission later.
void
save(Symbol* sym, Relobj*, unsigned int shndx,
Output_section* output_section, const elfcpp::Rela<size, big_endian>&);
// Return whether there are any relocs to emit. This also discards
// entries which need not be emitted.
bool
any_to_emit();
// Emit relocs for each symbol which did not get a COPY reloc (i.e.,
// is still defined in the dynamic object).
template<int sh_type>
void
emit(Output_data_reloc<sh_type, true, size, big_endian>*);
private:
typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
// This POD class holds the entries we are saving.
class Copy_reloc_entry
{
public:
Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
Relobj* relobj, unsigned int shndx,
Output_section* output_section,
Address address, Addend addend)
: sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
shndx_(shndx), output_section_(output_section),
address_(address), addend_(addend)
{ }
// Return whether we should emit this reloc. If we should not
// emit, we clear it.
bool
should_emit();
// Emit this reloc.
void
emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*);
void
emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*);
private:
Symbol* sym_;
unsigned int reloc_type_;
Relobj* relobj_;
unsigned int shndx_;
Output_section* output_section_;
Address address_;
Addend addend_;
};
// A list of relocs to be saved.
typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
// The list of relocs we are saving.
Copy_reloc_entries entries_;
};
// Track relocations while reading a section. This lets you ask for
// the relocation at a certain offset, and see how relocs occur
// between points of interest.
template<int size, bool big_endian>
class Track_relocs
{
public:
Track_relocs()
: prelocs_(NULL), len_(0), pos_(0), reloc_size_(0)
{ }
// Initialize the Track_relocs object. OBJECT is the object holding
// the reloc section, RELOC_SHNDX is the section index of the reloc
// section, and RELOC_TYPE is the type of the reloc section
// (elfcpp::SHT_REL or elfcpp::SHT_RELA). This returns false if
// something went wrong.
bool
initialize(Object* object, unsigned int reloc_shndx,
unsigned int reloc_type);
// Return the offset in the data section to which the next reloc
// applies. THis returns -1 if there is no next reloc.
off_t
next_offset() const;
// Return the symbol index of the next reloc. This returns -1U if
// there is no next reloc.
unsigned int
next_symndx() const;
// Advance to OFFSET within the data section, and return the number
// of relocs which would be skipped.
int
advance(off_t offset);
private:
// The contents of the input object's reloc section.
const unsigned char* prelocs_;
// The length of the reloc section.
section_size_type len_;
// Our current position in the reloc section.
section_size_type pos_;
// The size of the relocs in the section.
int reloc_size_;
};
} // End namespace gold.
#endif // !defined(GOLD_RELOC_H)
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