523 lines
16 KiB
C++
523 lines
16 KiB
C++
// ehframe.h -- handle exception frame sections for gold -*- C++ -*-
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// Copyright 2006, 2007, 2008, 2010, 2011 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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#ifndef GOLD_EHFRAME_H
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#define GOLD_EHFRAME_H
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#include <map>
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#include <set>
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#include <vector>
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#include "output.h"
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#include "merge.h"
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namespace gold
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{
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template<int size, bool big_endian>
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class Track_relocs;
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class Eh_frame;
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// This class manages the .eh_frame_hdr section, which holds the data
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// for the PT_GNU_EH_FRAME segment. gcc's unwind support code uses
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// the PT_GNU_EH_FRAME segment to find the list of FDEs. This saves
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// the time required to register the exception handlers at startup
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// time and when a shared object is loaded, and the time required to
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// deregister the exception handlers when a shared object is unloaded.
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class Eh_frame_hdr : public Output_section_data
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{
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public:
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Eh_frame_hdr(Output_section* eh_frame_section, const Eh_frame*);
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// Record that we found an unrecognized .eh_frame section.
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void
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found_unrecognized_eh_frame_section()
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{ this->any_unrecognized_eh_frame_sections_ = true; }
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// Record an FDE.
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void
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record_fde(section_offset_type fde_offset, unsigned char fde_encoding)
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{
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if (!this->any_unrecognized_eh_frame_sections_)
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{
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Hold_lock(*this->lock_);
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this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
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}
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}
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protected:
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// Set the final data size.
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void
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set_final_data_size();
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// Write the data to the file.
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void
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do_write(Output_file*);
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// Write to a map file.
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void
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do_print_to_mapfile(Mapfile* mapfile) const
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{ mapfile->print_output_data(this, _("** eh_frame_hdr")); }
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private:
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// Write the data to the file with the right endianness.
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template<int size, bool big_endian>
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void
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do_sized_write(Output_file*);
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// The data we record for one FDE: the offset of the FDE within the
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// .eh_frame section, and the FDE encoding.
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typedef std::pair<section_offset_type, unsigned char> Fde_offset;
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// The list of information we record for an FDE.
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typedef std::vector<Fde_offset> Fde_offsets;
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// When writing out the header, we convert the FDE offsets into FDE
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// addresses. This is a list of pairs of the offset from the header
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// to the FDE PC and to the FDE itself.
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template<int size>
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class Fde_addresses
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{
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public:
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typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
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typedef typename std::pair<Address, Address> Fde_address;
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typedef typename std::vector<Fde_address> Fde_address_list;
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typedef typename Fde_address_list::iterator iterator;
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Fde_addresses(unsigned int reserve)
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: fde_addresses_()
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{ this->fde_addresses_.reserve(reserve); }
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void
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push_back(Address pc_address, Address fde_address)
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{
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this->fde_addresses_.push_back(std::make_pair(pc_address, fde_address));
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}
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iterator
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begin()
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{ return this->fde_addresses_.begin(); }
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iterator
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end()
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{ return this->fde_addresses_.end(); }
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private:
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Fde_address_list fde_addresses_;
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};
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// Compare Fde_address objects.
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template<int size>
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struct Fde_address_compare
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{
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bool
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operator()(const typename Fde_addresses<size>::Fde_address& f1,
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const typename Fde_addresses<size>::Fde_address& f2) const
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{ return f1.first < f2.first; }
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};
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// Return the PC to which an FDE refers.
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template<int size, bool big_endian>
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typename elfcpp::Elf_types<size>::Elf_Addr
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get_fde_pc(typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address,
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const unsigned char* eh_frame_contents,
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section_offset_type fde_offset, unsigned char fde_encoding);
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// Convert Fde_offsets to Fde_addresses.
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template<int size, bool big_endian>
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void
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get_fde_addresses(Output_file* of,
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const Fde_offsets* fde_offsets,
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Fde_addresses<size>* fde_addresses);
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// The .eh_frame section.
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Output_section* eh_frame_section_;
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// The .eh_frame section data.
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const Eh_frame* eh_frame_data_;
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// Data from the FDEs in the .eh_frame sections.
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Fde_offsets fde_offsets_;
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// Whether we found any .eh_frame sections which we could not
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// process.
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bool any_unrecognized_eh_frame_sections_;
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// Lock held while updating fde_offsets_.
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Lock* lock_;
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};
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// This class holds an FDE.
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class Fde
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{
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public:
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Fde(Relobj* object, unsigned int shndx, section_offset_type input_offset,
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const unsigned char* contents, size_t length)
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: object_(object),
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contents_(reinterpret_cast<const char*>(contents), length)
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{
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this->u_.from_object.shndx = shndx;
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this->u_.from_object.input_offset = input_offset;
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}
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// Create an FDE associated with a PLT.
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Fde(Output_data* plt, const unsigned char* contents, size_t length,
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bool post_map)
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: object_(NULL),
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contents_(reinterpret_cast<const char*>(contents), length)
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{
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this->u_.from_linker.plt = plt;
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this->u_.from_linker.post_map = post_map;
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}
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// Return the length of this FDE. Add 4 for the length and 4 for
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// the offset to the CIE.
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size_t
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length() const
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{ return this->contents_.length() + 8; }
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// Add a mapping for this FDE to MERGE_MAP, so that relocations
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// against the FDE are applied to right part of the output file.
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void
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add_mapping(section_offset_type output_offset, Merge_map* merge_map) const
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{
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if (this->object_ != NULL)
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merge_map->add_mapping(this->object_, this->u_.from_object.shndx,
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this->u_.from_object.input_offset, this->length(),
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output_offset);
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}
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// Return whether this FDE was added after merge mapping.
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bool
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post_map()
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{ return this->object_ == NULL && this->u_.from_linker.post_map; }
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// Write the FDE to OVIEW starting at OFFSET. FDE_ENCODING is the
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// encoding, from the CIE. Round up the bytes to ADDRALIGN if
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// necessary. ADDRESS is the virtual address of OVIEW. Record the
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// FDE in EH_FRAME_HDR. Return the new offset.
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template<int size, bool big_endian>
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section_offset_type
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write(unsigned char* oview, section_offset_type offset,
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uint64_t address, unsigned int addralign,
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section_offset_type cie_offset, unsigned char fde_encoding,
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Eh_frame_hdr* eh_frame_hdr);
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private:
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// The object in which this FDE was seen. This will be NULL for a
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// linker generated FDE.
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Relobj* object_;
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union
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{
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// These fields are used if the FDE is from an input object (the
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// object_ field is not NULL).
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struct
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{
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// Input section index for this FDE.
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unsigned int shndx;
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// Offset within the input section for this FDE.
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section_offset_type input_offset;
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} from_object;
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// This field is used if the FDE is generated by the linker (the
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// object_ field is NULL).
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struct
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{
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// The only linker generated FDEs are for PLT sections, and this
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// points to the PLT section.
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Output_data* plt;
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// Set if the FDE was added after merge mapping.
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bool post_map;
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} from_linker;
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} u_;
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// FDE data.
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std::string contents_;
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};
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// A FDE plus some info from a CIE to allow later writing of the FDE.
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struct Post_fde
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{
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Post_fde(Fde* f, section_offset_type cie_off, unsigned char encoding)
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: fde(f), cie_offset(cie_off), fde_encoding(encoding)
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{ }
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Fde* fde;
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section_offset_type cie_offset;
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unsigned char fde_encoding;
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};
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typedef std::vector<Post_fde> Post_fdes;
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// This class holds a CIE.
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class Cie
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{
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public:
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Cie(Relobj* object, unsigned int shndx, section_offset_type input_offset,
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unsigned char fde_encoding, const char* personality_name,
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const unsigned char* contents, size_t length)
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: object_(object),
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shndx_(shndx),
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input_offset_(input_offset),
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fde_encoding_(fde_encoding),
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personality_name_(personality_name),
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fdes_(),
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contents_(reinterpret_cast<const char*>(contents), length)
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{ }
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~Cie();
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// We permit copying a CIE when there are no FDEs. This is
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// convenient in the code which creates them.
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Cie(const Cie& cie)
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: object_(cie.object_),
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shndx_(cie.shndx_),
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input_offset_(cie.input_offset_),
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fde_encoding_(cie.fde_encoding_),
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personality_name_(cie.personality_name_),
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fdes_(),
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contents_(cie.contents_)
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{ gold_assert(cie.fdes_.empty()); }
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// Add an FDE associated with this CIE.
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void
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add_fde(Fde* fde)
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{ this->fdes_.push_back(fde); }
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// Return the number of FDEs.
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unsigned int
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fde_count() const
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{ return this->fdes_.size(); }
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// Set the output offset of this CIE to OUTPUT_OFFSET. It will be
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// followed by all its FDEs. ADDRALIGN is the required address
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// alignment, typically 4 or 8. This updates MERGE_MAP with the
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// mapping. It returns the new output offset.
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section_offset_type
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set_output_offset(section_offset_type output_offset, unsigned int addralign,
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Merge_map*);
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// Write the CIE to OVIEW starting at OFFSET. Round up the bytes to
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// ADDRALIGN. ADDRESS is the virtual address of OVIEW.
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// EH_FRAME_HDR is the exception frame header for FDE recording.
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// POST_FDES stashes FDEs created after mappings were done, for later
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// writing. Return the new offset.
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template<int size, bool big_endian>
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section_offset_type
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write(unsigned char* oview, section_offset_type offset, uint64_t address,
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unsigned int addralign, Eh_frame_hdr* eh_frame_hdr,
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Post_fdes* post_fdes);
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friend bool operator<(const Cie&, const Cie&);
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friend bool operator==(const Cie&, const Cie&);
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private:
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// The class is not assignable.
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Cie& operator=(const Cie&);
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// The object in which this CIE was first seen. This will be NULL
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// for a linker generated CIE.
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Relobj* object_;
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// Input section index for this CIE. This will be 0 for a linker
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// generated CIE.
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unsigned int shndx_;
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// Offset within the input section for this CIE. This will be 0 for
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// a linker generated CIE.
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section_offset_type input_offset_;
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// The encoding of the FDE. This is a DW_EH_PE code.
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unsigned char fde_encoding_;
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// The name of the personality routine. This will be the name of a
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// global symbol, or will be the empty string.
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std::string personality_name_;
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// List of FDEs.
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std::vector<Fde*> fdes_;
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// CIE data.
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std::string contents_;
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};
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extern bool operator<(const Cie&, const Cie&);
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extern bool operator==(const Cie&, const Cie&);
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// This class manages .eh_frame sections. It discards duplicate
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// exception information.
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class Eh_frame : public Output_section_data
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{
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public:
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Eh_frame();
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// Record the associated Eh_frame_hdr, if any.
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void
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set_eh_frame_hdr(Eh_frame_hdr* hdr)
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{ this->eh_frame_hdr_ = hdr; }
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// Add the input section SHNDX in OBJECT. SYMBOLS is the contents
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// of the symbol table section (size SYMBOLS_SIZE), SYMBOL_NAMES is
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// the symbol names section (size SYMBOL_NAMES_SIZE). RELOC_SHNDX
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// is the relocation section if any (0 for none, -1U for multiple).
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// RELOC_TYPE is the type of the relocation section if any. This
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// returns whether the section was incorporated into the .eh_frame
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// data.
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template<int size, bool big_endian>
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bool
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add_ehframe_input_section(Sized_relobj_file<size, big_endian>* object,
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const unsigned char* symbols,
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section_size_type symbols_size,
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const unsigned char* symbol_names,
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section_size_type symbol_names_size,
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unsigned int shndx, unsigned int reloc_shndx,
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unsigned int reloc_type);
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// Add a CIE and an FDE for a PLT section, to permit unwinding
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// through a PLT. The FDE data should start with 8 bytes of zero,
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// which will be replaced by a 4 byte PC relative reference to the
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// address of PLT and a 4 byte size of PLT.
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void
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add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
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size_t cie_length, const unsigned char* fde_data,
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size_t fde_length);
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// Return the number of FDEs.
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unsigned int
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fde_count() const;
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protected:
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// Set the final data size.
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void
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set_final_data_size();
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// Return the output address for an input address.
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bool
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do_output_offset(const Relobj*, unsigned int shndx,
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section_offset_type offset,
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section_offset_type* poutput) const;
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// Return whether this is the merge section for an input section.
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bool
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do_is_merge_section_for(const Relobj*, unsigned int shndx) const;
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// Write the data to the file.
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void
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do_write(Output_file*);
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// Write to a map file.
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void
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do_print_to_mapfile(Mapfile* mapfile) const
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{ mapfile->print_output_data(this, _("** eh_frame")); }
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private:
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// The comparison routine for the CIE map.
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struct Cie_less
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{
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bool
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operator()(const Cie* cie1, const Cie* cie2) const
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{ return *cie1 < *cie2; }
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};
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// A set of unique CIEs.
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typedef std::set<Cie*, Cie_less> Cie_offsets;
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// A list of unmergeable CIEs.
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typedef std::vector<Cie*> Unmergeable_cie_offsets;
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// A mapping from offsets to CIEs. This is used while reading an
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// input section.
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typedef std::map<uint64_t, Cie*> Offsets_to_cie;
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// A list of CIEs, and a bool indicating whether the CIE is
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// mergeable.
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typedef std::vector<std::pair<Cie*, bool> > New_cies;
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// Skip an LEB128.
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static bool
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skip_leb128(const unsigned char**, const unsigned char*);
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// The implementation of add_ehframe_input_section.
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template<int size, bool big_endian>
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bool
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do_add_ehframe_input_section(Sized_relobj_file<size, big_endian>* object,
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const unsigned char* symbols,
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section_size_type symbols_size,
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const unsigned char* symbol_names,
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section_size_type symbol_names_size,
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unsigned int shndx,
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unsigned int reloc_shndx,
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unsigned int reloc_type,
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const unsigned char* pcontents,
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section_size_type contents_len,
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New_cies*);
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// Read a CIE.
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template<int size, bool big_endian>
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bool
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read_cie(Sized_relobj_file<size, big_endian>* object,
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unsigned int shndx,
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const unsigned char* symbols,
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section_size_type symbols_size,
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const unsigned char* symbol_names,
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section_size_type symbol_names_size,
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const unsigned char* pcontents,
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const unsigned char* pcie,
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const unsigned char* pcieend,
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Track_relocs<size, big_endian>* relocs,
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Offsets_to_cie* cies,
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New_cies* new_cies);
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// Read an FDE.
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template<int size, bool big_endian>
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bool
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read_fde(Sized_relobj_file<size, big_endian>* object,
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unsigned int shndx,
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const unsigned char* symbols,
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section_size_type symbols_size,
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const unsigned char* pcontents,
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unsigned int offset,
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const unsigned char* pfde,
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const unsigned char* pfdeend,
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Track_relocs<size, big_endian>* relocs,
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Offsets_to_cie* cies);
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// Template version of write function.
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template<int size, bool big_endian>
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void
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do_sized_write(unsigned char* oview);
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// The exception frame header, if any.
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Eh_frame_hdr* eh_frame_hdr_;
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// A mapping from all unique CIEs to their offset in the output
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// file.
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Cie_offsets cie_offsets_;
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// A mapping from unmergeable CIEs to their offset in the output
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// file.
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Unmergeable_cie_offsets unmergeable_cie_offsets_;
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// A mapping from input sections to the output section.
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Merge_map merge_map_;
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// Whether we have created the mappings to the output section.
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bool mappings_are_done_;
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// The final data size. This is only set if mappings_are_done_ is
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// true.
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section_size_type final_data_size_;
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};
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} // End namespace gold.
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#endif // !defined(GOLD_EHFRAME_H)
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