273 lines
8.7 KiB
C++
273 lines
8.7 KiB
C++
// target.h -- target support for gold -*- C++ -*-
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// Copyright 2006, 2007 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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// The abstract class Target is the interface for target specific
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// support. It defines abstract methods which each target must
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// implement. Typically there will be one target per processor, but
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// in some cases it may be necessary to have subclasses.
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// For speed and consistency we want to use inline functions to handle
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// relocation processing. So besides implementations of the abstract
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// methods, each target is expected to define a template
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// specialization of the relocation functions.
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#ifndef GOLD_TARGET_H
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#define GOLD_TARGET_H
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#include "elfcpp.h"
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namespace gold
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{
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class General_options;
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class Object;
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template<int size, bool big_endian>
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class Sized_relobj;
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template<int size, bool big_endian>
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struct Relocate_info;
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class Symbol;
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template<int size>
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class Sized_symbol;
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class Symbol_table;
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// The abstract class for target specific handling.
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class Target
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{
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public:
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virtual ~Target()
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{ }
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// Return the bit size that this target implements. This should
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// return 32 or 64.
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int
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get_size() const
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{ return this->pti_->size; }
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// Return whether this target is big-endian.
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bool
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is_big_endian() const
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{ return this->pti_->is_big_endian; }
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// Machine code to store in e_machine field of ELF header.
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elfcpp::EM
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machine_code() const
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{ return this->pti_->machine_code; }
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// Whether this target has a specific make_symbol function.
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bool
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has_make_symbol() const
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{ return this->pti_->has_make_symbol; }
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// Whether this target has a specific resolve function.
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bool
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has_resolve() const
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{ return this->pti_->has_resolve; }
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// Whether this target has a specific code fill function.
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bool
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has_code_fill() const
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{ return this->pti_->has_code_fill; }
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// Return the default name of the dynamic linker.
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const char*
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dynamic_linker() const
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{ return this->pti_->dynamic_linker; }
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// Return the default address to use for the text segment.
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uint64_t
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default_text_segment_address() const
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{ return this->pti_->default_text_segment_address; }
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// Return the ABI specified page size.
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uint64_t
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abi_pagesize() const
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{ return this->pti_->abi_pagesize; }
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// Return the common page size used on actual systems.
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uint64_t
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common_pagesize() const
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{ return this->pti_->common_pagesize; }
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// If we see some object files with .note.GNU-stack sections, and
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// some objects files without them, this returns whether we should
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// consider the object files without them to imply that the stack
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// should be executable.
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bool
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is_default_stack_executable() const
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{ return this->pti_->is_default_stack_executable; }
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// This is called to tell the target to complete any sections it is
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// handling. After this all sections must have their final size.
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void
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finalize_sections(Layout* layout)
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{ return this->do_finalize_sections(layout); }
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// Return the value to use for a global symbol which needs a special
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// value in the dynamic symbol table. This will only be called if
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// the backend first calls symbol->set_needs_dynsym_value().
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uint64_t
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dynsym_value(const Symbol* sym) const
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{ return this->do_dynsym_value(sym); }
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// Return a string to use to fill out a code section. This is
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// basically one or more NOPS which must fill out the specified
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// length in bytes.
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std::string
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code_fill(off_t length)
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{ return this->do_code_fill(length); }
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protected:
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// This struct holds the constant information for a child class. We
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// use a struct to avoid the overhead of virtual function calls for
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// simple information.
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struct Target_info
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{
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// Address size (32 or 64).
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int size;
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// Whether the target is big endian.
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bool is_big_endian;
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// The code to store in the e_machine field of the ELF header.
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elfcpp::EM machine_code;
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// Whether this target has a specific make_symbol function.
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bool has_make_symbol;
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// Whether this target has a specific resolve function.
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bool has_resolve;
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// Whether this target has a specific code fill function.
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bool has_code_fill;
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// Whether an object file with no .note.GNU-stack sections implies
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// that the stack should be executable.
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bool is_default_stack_executable;
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// The default dynamic linker name.
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const char* dynamic_linker;
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// The default text segment address.
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uint64_t default_text_segment_address;
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// The ABI specified page size.
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uint64_t abi_pagesize;
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// The common page size used by actual implementations.
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uint64_t common_pagesize;
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};
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Target(const Target_info* pti)
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: pti_(pti)
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{ }
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// Virtual function which may be implemented by the child class.
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virtual void
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do_finalize_sections(Layout*)
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{ }
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// Virtual function which may be implemented by the child class.
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virtual uint64_t
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do_dynsym_value(const Symbol*) const
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{ gold_unreachable(); }
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// Virtual function which must be implemented by the child class if
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// needed.
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virtual std::string
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do_code_fill(off_t)
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{ gold_unreachable(); }
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private:
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Target(const Target&);
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Target& operator=(const Target&);
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// The target information.
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const Target_info* pti_;
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};
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// The abstract class for a specific size and endianness of target.
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// Each actual target implementation class should derive from an
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// instantiation of Sized_target.
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template<int size, bool big_endian>
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class Sized_target : public Target
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{
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public:
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// Make a new symbol table entry for the target. This should be
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// overridden by a target which needs additional information in the
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// symbol table. This will only be called if has_make_symbol()
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// returns true.
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virtual Sized_symbol<size>*
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make_symbol() const
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{ gold_unreachable(); }
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// Resolve a symbol for the target. This should be overridden by a
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// target which needs to take special action. TO is the
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// 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
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// has_resolve() returns true.
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virtual void
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resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
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const char*)
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{ gold_unreachable(); }
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// Scan the relocs for a section, and record any information
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// required for the symbol. OPTIONS is the command line options.
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// SYMTAB is the symbol table. OBJECT is the object in which the
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// section appears. DATA_SHNDX is the section index that these
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// relocs apply to. SH_TYPE is the type of the relocation section,
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// SHT_REL or SHT_RELA. PRELOCS points to the relocation data.
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// RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the
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// number of local symbols. PLOCAL_SYMBOLS points to the local
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// symbol data from OBJECT. GLOBAL_SYMBOLS is the array of pointers
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// to the global symbol table from OBJECT.
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virtual void
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scan_relocs(const General_options& options,
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Symbol_table* symtab,
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Layout* layout,
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Sized_relobj<size, big_endian>* object,
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unsigned int data_shndx,
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unsigned int sh_type,
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const unsigned char* prelocs,
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size_t reloc_count,
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size_t local_symbol_count,
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const unsigned char* plocal_symbols,
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Symbol** global_symbols) = 0;
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// Relocate section data. SH_TYPE is the type of the relocation
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// section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
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// information. RELOC_COUNT is the number of relocs. VIEW is a
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// view into the output file holding the section contents,
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// VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
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// the size of the view.
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virtual void
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relocate_section(const Relocate_info<size, big_endian>*,
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unsigned int sh_type,
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const unsigned char* prelocs,
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size_t reloc_count,
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unsigned char* view,
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typename elfcpp::Elf_types<size>::Elf_Addr view_address,
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off_t view_size) = 0;
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protected:
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Sized_target(const Target::Target_info* pti)
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: Target(pti)
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{
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gold_assert(pti->size == size);
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gold_assert(pti->is_big_endian ? big_endian : !big_endian);
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}
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};
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} // End namespace gold.
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#endif // !defined(GOLD_TARGET_H)
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