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// target.h -- target support for gold -*- C++ -*-
// The abstract class Target is the interface for target specific
// support. It defines abstract methods which each target must
// implement. Typically there will be one target per processor, but
// in some cases it may be necessary to have subclasses.
// For speed and consistency we want to use inline functions to handle
// relocation processing. So besides implementations of the abstract
// methods, each target is expected to define a template
// specialization of the relocation functions.
#ifndef GOLD_TARGET_H
#define GOLD_TARGET_H
#include <cassert>
#include "elfcpp.h"
#include "symtab.h"
namespace gold
{
class General_options;
class Object;
template<int size, bool big_endian>
class Sized_object;
template<int size, bool big_endian>
struct Relocate_info;
// The abstract class for target specific handling.
class Target
{
public:
virtual ~Target()
{ }
// Return the bit size that this target implements. This should
// return 32 or 64.
int
get_size() const
{ return this->pti_->size; }
// Return whether this target is big-endian.
bool
is_big_endian() const
{ return this->pti_->is_big_endian; }
// Machine code to store in e_machine field of ELF header.
elfcpp::EM
machine_code() const
{ return this->pti_->machine_code; }
// Whether this target has a specific make_symbol function.
bool
has_make_symbol() const
{ return this->pti_->has_make_symbol; }
// Whether this target has a specific resolve function.
bool
has_resolve() const
{ return this->pti_->has_resolve; }
// Return the default address to use for the text segment.
uint64_t
text_segment_address() const
{ return this->pti_->text_segment_address; }
// Return the ABI specified page size.
uint64_t
abi_pagesize() const
{ return this->pti_->abi_pagesize; }
// Return the common page size used on actual systems.
uint64_t
common_pagesize() const
{ return this->pti_->common_pagesize; }
protected:
// This struct holds the constant information for a child class. We
// use a struct to avoid the overhead of virtual function calls for
// simple information.
struct Target_info
{
// Address size (32 or 64).
int size;
// Whether the target is big endian.
bool is_big_endian;
// The code to store in the e_machine field of the ELF header.
elfcpp::EM machine_code;
// Whether this target has a specific make_symbol function.
bool has_make_symbol;
// Whether this target has a specific resolve function.
bool has_resolve;
// The default text segment address.
uint64_t text_segment_address;
// The ABI specified page size.
uint64_t abi_pagesize;
// The common page size used by actual implementations.
uint64_t common_pagesize;
};
Target(const Target_info* pti)
: pti_(pti)
{ }
private:
Target(const Target&);
Target& operator=(const Target&);
// The target information.
const Target_info* pti_;
};
// The abstract class for a specific size and endianness of target.
// Each actual target implementation class should derive from an
// instantiation of Sized_target.
template<int size, bool big_endian>
class Sized_target : public Target
{
public:
// Make a new symbol table entry for the target. This should be
// overridden by a target which needs additional information in the
// symbol table. This will only be called if has_make_symbol()
// returns true.
virtual Sized_symbol<size>*
make_symbol()
{ abort(); }
// Resolve a symbol for the target. This should be overridden by a
// target which needs to take special action. TO is the
// pre-existing symbol. SYM is the new symbol, seen in OBJECT.
// This will only be called if has_resolve() returns true.
virtual void
resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*)
{ abort(); }
// Scan the relocs for a section, and record any information
// required for the symbol. OPTIONS is the command line options.
// SYMTAB is the symbol table. OBJECT is the object in which the
// section appears. SH_TYPE is the type of the relocation section,
// SHT_REL or SHT_RELA. PRELOCS points to the relocation data.
// RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the
// number of local symbols. PLOCAL_SYMBOLS points to the local
// symbol data from OBJECT. GLOBAL_SYMBOLS is the array of pointers
// to the global symbol table from OBJECT.
virtual void
scan_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_object<size, big_endian>* object,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
size_t local_symbol_count,
const unsigned char* plocal_symbols,
Symbol** global_symbols) = 0;
// Relocate section data. SH_TYPE is the type of the relocation
// section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
// information. RELOC_COUNT is the number of relocs. VIEW is a
// view into the output file holding the section contents,
// VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
// the size of the view.
virtual void
relocate_section(const Relocate_info<size, big_endian>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr view_address,
off_t view_size) = 0;
protected:
Sized_target(const Target::Target_info* pti)
: Target(pti)
{
assert(pti->size == size);
assert(pti->is_big_endian ? big_endian : !big_endian);
}
};
} // End namespace gold.
#endif // !defined(GOLD_TARGET_H)
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