binutils-gdb/gold/target.h

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// target.h -- target support for gold -*- C++ -*-
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// Copyright 2006, 2007, 2008 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.
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// 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 "elfcpp.h"
#include "options.h"
#include "parameters.h"
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namespace gold
{
class General_options;
class Object;
template<int size, bool big_endian>
class Sized_relobj;
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class Relocatable_relocs;
template<int size, bool big_endian>
class Relocate_info;
class Symbol;
template<int size>
class Sized_symbol;
class Symbol_table;
class Output_section;
// The abstract class for target specific handling.
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class Target
{
public:
virtual ~Target()
{ }
// Return the bit size that this target implements. This should
// return 32 or 64.
int
get_size() const
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{ return this->pti_->size; }
// Return whether this target is big-endian.
bool
is_big_endian() const
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{ 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
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{ return this->pti_->has_make_symbol; }
// Whether this target has a specific resolve function.
bool
has_resolve() const
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{ return this->pti_->has_resolve; }
// Whether this target has a specific code fill function.
bool
has_code_fill() const
{ return this->pti_->has_code_fill; }
// Return the default name of the dynamic linker.
const char*
dynamic_linker() const
{ return this->pti_->dynamic_linker; }
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// Return the default address to use for the text segment.
uint64_t
default_text_segment_address() const
{ return this->pti_->default_text_segment_address; }
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// Return the ABI specified page size.
uint64_t
abi_pagesize() const
{
if (parameters->options().max_page_size() > 0)
return parameters->options().max_page_size();
else
return this->pti_->abi_pagesize;
}
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// Return the common page size used on actual systems.
uint64_t
common_pagesize() const
{
if (parameters->options().common_page_size() > 0)
return std::min(parameters->options().common_page_size(),
this->abi_pagesize());
else
return std::min(this->pti_->common_pagesize,
this->abi_pagesize());
}
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// If we see some object files with .note.GNU-stack sections, and
// some objects files without them, this returns whether we should
// consider the object files without them to imply that the stack
// should be executable.
bool
is_default_stack_executable() const
{ return this->pti_->is_default_stack_executable; }
// Return a character which may appear as a prefix for a wrap
// symbol. If this character appears, we strip it when checking for
// wrapping and add it back when forming the final symbol name.
// This should be '\0' if not special prefix is required, which is
// the normal case.
char
wrap_char() const
{ return this->pti_->wrap_char; }
// This is called to tell the target to complete any sections it is
// handling. After this all sections must have their final size.
void
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finalize_sections(Layout* layout)
{ return this->do_finalize_sections(layout); }
// Return the value to use for a global symbol which needs a special
// value in the dynamic symbol table. This will only be called if
// the backend first calls symbol->set_needs_dynsym_value().
uint64_t
dynsym_value(const Symbol* sym) const
{ return this->do_dynsym_value(sym); }
// Return a string to use to fill out a code section. This is
// basically one or more NOPS which must fill out the specified
// length in bytes.
std::string
code_fill(section_size_type length) const
{ return this->do_code_fill(length); }
// Return whether SYM is known to be defined by the ABI. This is
// used to avoid inappropriate warnings about undefined symbols.
bool
is_defined_by_abi(const Symbol* sym) const
{ return this->do_is_defined_by_abi(sym); }
protected:
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// 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;
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// Whether this target has a specific make_symbol function.
bool has_make_symbol;
// Whether this target has a specific resolve function.
bool has_resolve;
// Whether this target has a specific code fill function.
bool has_code_fill;
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// Whether an object file with no .note.GNU-stack sections implies
// that the stack should be executable.
bool is_default_stack_executable;
// Prefix character to strip when checking for wrapping.
char wrap_char;
// The default dynamic linker name.
const char* dynamic_linker;
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// The default text segment address.
uint64_t default_text_segment_address;
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// 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)
{ }
// Virtual function which may be implemented by the child class.
virtual void
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do_finalize_sections(Layout*)
{ }
// Virtual function which may be implemented by the child class.
virtual uint64_t
do_dynsym_value(const Symbol*) const
{ gold_unreachable(); }
// Virtual function which must be implemented by the child class if
// needed.
virtual std::string
do_code_fill(section_size_type) const
{ gold_unreachable(); }
// Virtual function which may be implemented by the child class.
virtual bool
do_is_defined_by_abi(const Symbol*) const
{ return false; }
private:
Target(const Target&);
Target& operator=(const Target&);
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// The target information.
const Target_info* pti_;
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};
// 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>*
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make_symbol() const
{ gold_unreachable(); }
// 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.
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// VERSION is the version of SYM. This will only be called if
// has_resolve() returns true.
virtual void
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resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
const char*)
{ gold_unreachable(); }
// 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. DATA_SHNDX is the section index that these
// relocs apply to. 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. OUTPUT_SECTION is the output section.
// NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
// sections are not mapped as usual. 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_relobj<size, big_endian>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_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.
// OUTPUT_SECTION is the output section.
// NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
// to correspond to the output section. 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. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
// parameters refer to the complete output section data, not just
// the input section data.
virtual void
relocate_section(const Relocate_info<size, big_endian>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr view_address,
section_size_type view_size) = 0;
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// Scan the relocs during a relocatable link. The parameters are
// like scan_relocs, with an additional Relocatable_relocs
// parameter, used to record the disposition of the relocs.
virtual void
scan_relocatable_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<size, big_endian>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
bool needs_special_offset_handling,
size_t local_symbol_count,
const unsigned char* plocal_symbols,
Relocatable_relocs*) = 0;
// Relocate a section during a relocatable link. The parameters are
// like relocate_section, with additional parameters for the view of
// the output reloc section.
virtual void
relocate_for_relocatable(const Relocate_info<size, big_endian>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
Output_section* output_section,
off_t offset_in_output_section,
const Relocatable_relocs*,
unsigned char* view,
typename elfcpp::Elf_types<size>::Elf_Addr
view_address,
section_size_type view_size,
unsigned char* reloc_view,
section_size_type reloc_view_size) = 0;
protected:
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Sized_target(const Target::Target_info* pti)
: Target(pti)
{
gold_assert(pti->size == size);
gold_assert(pti->is_big_endian ? big_endian : !big_endian);
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}
};
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} // End namespace gold.
#endif // !defined(GOLD_TARGET_H)