514 lines
15 KiB
C++
514 lines
15 KiB
C++
// merge.h -- handle section merging for gold -*- C++ -*-
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// Copyright (C) 2006-2022 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_MERGE_H
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#define GOLD_MERGE_H
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#include <climits>
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#include <map>
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#include <vector>
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#include "stringpool.h"
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#include "output.h"
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namespace gold
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{
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// For each object with merge sections, we store an Object_merge_map.
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// This is used to map locations in input sections to a merged output
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// section. The output section itself is not recorded here--it can be
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// found in the output_sections_ field of the Object.
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class Object_merge_map
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{
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public:
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Object_merge_map()
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: section_merge_maps_()
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{ }
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~Object_merge_map();
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// Add a mapping for MERGE_MAP, for the bytes from OFFSET to OFFSET
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// + LENGTH in the input section SHNDX to OUTPUT_OFFSET in the
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// output section. An OUTPUT_OFFSET of -1 means that the bytes are
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// discarded. OUTPUT_OFFSET is relative to the start of the merged
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// data in the output section.
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void
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add_mapping(const Output_section_data*, unsigned int shndx,
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section_offset_type offset, section_size_type length,
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section_offset_type output_offset);
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// Get the output offset for an input address. MERGE_MAP is the map
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// we are looking for, or NULL if we don't care. The input address
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// is at offset OFFSET in section SHNDX. This sets *OUTPUT_OFFSET
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// to the offset in the output section; this will be -1 if the bytes
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// are not being copied to the output. This returns true if the
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// mapping is known, false otherwise. *OUTPUT_OFFSET is relative to
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// the start of the merged data in the output section.
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bool
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get_output_offset(unsigned int shndx,
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section_offset_type offset,
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section_offset_type* output_offset);
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const Output_section_data*
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find_merge_section(unsigned int shndx) const;
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// Initialize an mapping from input offsets to output addresses for
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// section SHNDX. STARTING_ADDRESS is the output address of the
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// merged section.
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template<int size>
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void
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initialize_input_to_output_map(
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unsigned int shndx,
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typename elfcpp::Elf_types<size>::Elf_Addr starting_address,
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Unordered_map<section_offset_type,
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typename elfcpp::Elf_types<size>::Elf_Addr>*);
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// Map input section offsets to a length and an output section
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// offset. An output section offset of -1 means that this part of
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// the input section is being discarded.
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struct Input_merge_entry
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{
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// The offset in the input section.
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section_offset_type input_offset;
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// The length.
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section_size_type length;
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// The offset in the output section.
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section_offset_type output_offset;
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};
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// A list of entries for a particular input section.
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struct Input_merge_map
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{
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void add_mapping(section_offset_type input_offset, section_size_type length,
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section_offset_type output_offset);
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typedef std::vector<Input_merge_entry> Entries;
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// We store these with the Relobj, and we look them up by input
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// section. It is possible to have two different merge maps
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// associated with a single output section. For example, this
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// happens routinely with .rodata, when merged string constants
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// and merged fixed size constants are both put into .rodata. The
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// output offset that we store is not the offset from the start of
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// the output section; it is the offset from the start of the
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// merged data in the output section. That means that the caller
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// is going to add the offset of the merged data within the output
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// section, which means that the caller needs to know which set of
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// merged data it found the entry in. So it's not enough to find
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// this data based on the input section and the output section; we
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// also have to find it based on a set of merged data in the
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// output section. In order to verify that we are looking at the
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// right data, we store a pointer to the Merge_map here, and we
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// pass in a pointer when looking at the data. If we are asked to
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// look up information for a different Merge_map, we report that
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// we don't have it, rather than trying a lookup and returning an
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// answer which will receive the wrong offset.
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const Output_section_data* output_data;
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// The list of mappings.
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Entries entries;
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// Whether the ENTRIES field is sorted by input_offset.
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bool sorted;
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Input_merge_map()
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: output_data(NULL), entries(), sorted(true)
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{ }
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};
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// Get or make the Input_merge_map to use for the section SHNDX
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// with MERGE_MAP.
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Input_merge_map*
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get_or_make_input_merge_map(const Output_section_data* merge_map,
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unsigned int shndx);
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private:
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// A less-than comparison routine for Input_merge_entry.
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struct Input_merge_compare
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{
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bool
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operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const
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{ return i1.input_offset < i2.input_offset; }
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};
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// Map input section indices to merge maps.
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typedef std::vector<std::pair<unsigned int, Input_merge_map*> >
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Section_merge_maps;
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// Return a pointer to the Input_merge_map to use for the input
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// section SHNDX, or NULL.
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const Input_merge_map*
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get_input_merge_map(unsigned int shndx) const;
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Input_merge_map *
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get_input_merge_map(unsigned int shndx) {
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return const_cast<Input_merge_map *>(static_cast<const Object_merge_map *>(
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this)->get_input_merge_map(shndx));
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}
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Section_merge_maps section_merge_maps_;
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};
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// A general class for SHF_MERGE data, to hold functions shared by
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// fixed-size constant data and string data.
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class Output_merge_base : public Output_section_data
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{
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public:
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Output_merge_base(uint64_t entsize, uint64_t addralign)
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: Output_section_data(addralign), entsize_(entsize),
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keeps_input_sections_(false), first_relobj_(NULL), first_shndx_(-1),
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input_sections_()
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{ }
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// Return the entry size.
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uint64_t
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entsize() const
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{ return this->entsize_; }
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// Whether this is a merge string section. This is only true of
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// Output_merge_string.
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bool
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is_string()
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{ return this->do_is_string(); }
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// Whether this keeps input sections.
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bool
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keeps_input_sections() const
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{ return this->keeps_input_sections_; }
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// Set the keeps-input-sections flag. This is virtual so that sub-classes
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// can perform additional checks.
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void
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set_keeps_input_sections()
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{ this->do_set_keeps_input_sections(); }
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// Return the object of the first merged input section. This used
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// for script processing. This is NULL if merge section is empty.
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Relobj*
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first_relobj() const
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{ return this->first_relobj_; }
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// Return the section index of the first merged input section. This
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// is used for script processing. This is valid only if merge section
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// is not valid.
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unsigned int
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first_shndx() const
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{
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gold_assert(this->first_relobj_ != NULL);
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return this->first_shndx_;
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}
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// Set of merged input sections.
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typedef Unordered_set<Section_id, Section_id_hash> Input_sections;
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// Beginning of merged input sections.
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Input_sections::const_iterator
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input_sections_begin() const
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{
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gold_assert(this->keeps_input_sections_);
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return this->input_sections_.begin();
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}
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// Beginning of merged input sections.
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Input_sections::const_iterator
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input_sections_end() const
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{
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gold_assert(this->keeps_input_sections_);
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return this->input_sections_.end();
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}
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protected:
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// Return the output offset for an input offset.
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bool
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do_output_offset(const Relobj* object, unsigned int shndx,
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section_offset_type offset,
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section_offset_type* poutput) const;
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// This may be overridden by the child class.
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virtual bool
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do_is_string()
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{ return false; }
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// This may be overridden by the child class.
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virtual void
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do_set_keeps_input_sections()
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{ this->keeps_input_sections_ = true; }
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// Record the merged input section for script processing.
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void
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record_input_section(Relobj* relobj, unsigned int shndx);
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private:
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// The entry size. For fixed-size constants, this is the size of
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// the constants. For strings, this is the size of a character.
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uint64_t entsize_;
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// Whether we keep input sections.
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bool keeps_input_sections_;
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// Object of the first merged input section. We use this for script
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// processing.
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Relobj* first_relobj_;
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// Section index of the first merged input section.
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unsigned int first_shndx_;
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// Input sections. We only keep them is keeps_input_sections_ is true.
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Input_sections input_sections_;
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};
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// Handle SHF_MERGE sections with fixed-size constant data.
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class Output_merge_data : public Output_merge_base
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{
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public:
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Output_merge_data(uint64_t entsize, uint64_t addralign)
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: Output_merge_base(entsize, addralign), p_(NULL), len_(0), alc_(0),
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input_count_(0),
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hashtable_(128, Merge_data_hash(this), Merge_data_eq(this))
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{ }
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protected:
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// Add an input section.
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bool
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do_add_input_section(Relobj* object, unsigned int shndx);
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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 the data to a buffer.
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void
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do_write_to_buffer(unsigned char*);
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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, _("** merge constants")); }
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// Print merge stats to stderr.
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void
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do_print_merge_stats(const char* section_name);
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// Set keeps-input-sections flag.
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void
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do_set_keeps_input_sections()
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{
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gold_assert(this->input_count_ == 0);
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Output_merge_base::do_set_keeps_input_sections();
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}
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private:
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// We build a hash table of the fixed-size constants. Each constant
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// is stored as a pointer into the section data we are accumulating.
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// A key in the hash table. This is an offset in the section
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// contents we are building.
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typedef section_offset_type Merge_data_key;
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// Compute the hash code. To do this we need a pointer back to the
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// object holding the data.
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class Merge_data_hash
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{
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public:
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Merge_data_hash(const Output_merge_data* pomd)
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: pomd_(pomd)
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{ }
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size_t
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operator()(Merge_data_key) const;
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private:
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const Output_merge_data* pomd_;
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};
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friend class Merge_data_hash;
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// Compare two entries in the hash table for equality. To do this
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// we need a pointer back to the object holding the data. Note that
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// we now have a pointer to the object stored in two places in the
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// hash table. Fixing this would require specializing the hash
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// table, which would be hard to do portably.
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class Merge_data_eq
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{
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public:
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Merge_data_eq(const Output_merge_data* pomd)
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: pomd_(pomd)
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{ }
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bool
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operator()(Merge_data_key k1, Merge_data_key k2) const;
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private:
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const Output_merge_data* pomd_;
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};
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friend class Merge_data_eq;
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// The type of the hash table.
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typedef Unordered_set<Merge_data_key, Merge_data_hash, Merge_data_eq>
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Merge_data_hashtable;
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// Given a hash table key, which is just an offset into the section
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// data, return a pointer to the corresponding constant.
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const unsigned char*
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constant(Merge_data_key k) const
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{
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gold_assert(k >= 0 && k < static_cast<section_offset_type>(this->len_));
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return this->p_ + k;
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}
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// Add a constant to the output.
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void
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add_constant(const unsigned char*);
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// The accumulated data.
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unsigned char* p_;
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// The length of the accumulated data.
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section_size_type len_;
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// The size of the allocated buffer.
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section_size_type alc_;
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// The number of entries seen in input files.
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size_t input_count_;
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// The hash table.
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Merge_data_hashtable hashtable_;
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};
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// Handle SHF_MERGE sections with string data. This is a template
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// based on the type of the characters in the string.
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template<typename Char_type>
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class Output_merge_string : public Output_merge_base
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{
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public:
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Output_merge_string(uint64_t addralign)
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: Output_merge_base(sizeof(Char_type), addralign), stringpool_(addralign),
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merged_strings_lists_(), input_count_(0), input_size_(0)
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{
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this->stringpool_.set_no_zero_null();
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}
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protected:
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// Add an input section.
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bool
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do_add_input_section(Relobj* object, unsigned int shndx);
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// Do all the final processing after the input sections are read in.
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// Returns the final data size.
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section_size_type
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finalize_merged_data();
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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 the data to a buffer.
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void
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do_write_to_buffer(unsigned char*);
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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, _("** merge strings")); }
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// Print merge stats to stderr.
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void
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do_print_merge_stats(const char* section_name);
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// Writes the stringpool to a buffer.
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void
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stringpool_to_buffer(unsigned char* buffer, section_size_type buffer_size)
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{ this->stringpool_.write_to_buffer(buffer, buffer_size); }
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// Clears all the data in the stringpool, to save on memory.
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void
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clear_stringpool()
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{ this->stringpool_.clear(); }
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// Whether this is a merge string section.
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virtual bool
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do_is_string()
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{ return true; }
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// Set keeps-input-sections flag.
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void
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do_set_keeps_input_sections()
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{
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gold_assert(this->input_count_ == 0);
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Output_merge_base::do_set_keeps_input_sections();
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}
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private:
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// The name of the string type, for stats.
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const char*
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string_name();
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// As we see input sections, we build a mapping from object, section
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// index and offset to strings.
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struct Merged_string
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{
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// The offset in the input section.
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section_offset_type offset;
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// The key in the Stringpool.
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Stringpool::Key stringpool_key;
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Merged_string(section_offset_type offseta, Stringpool::Key stringpool_keya)
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: offset(offseta), stringpool_key(stringpool_keya)
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{ }
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};
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typedef std::vector<Merged_string> Merged_strings;
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struct Merged_strings_list
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{
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// The input object where the strings were found.
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Relobj* object;
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// The input section in the input object.
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unsigned int shndx;
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// The list of merged strings.
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Merged_strings merged_strings;
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Merged_strings_list(Relobj* objecta, unsigned int shndxa)
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: object(objecta), shndx(shndxa), merged_strings()
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{ }
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};
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typedef std::vector<Merged_strings_list*> Merged_strings_lists;
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// As we see the strings, we add them to a Stringpool.
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Stringpool_template<Char_type> stringpool_;
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// Map from a location in an input object to an entry in the
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// Stringpool.
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Merged_strings_lists merged_strings_lists_;
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// The number of entries seen in input files.
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size_t input_count_;
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// The total size of input sections.
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size_t input_size_;
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};
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} // End namespace gold.
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#endif // !defined(GOLD_MERGE_H)
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