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// merge.h -- handle section merging for gold -*- C++ -*- // Copyright 2006, 2007, 2008 Free Software Foundation, Inc. // Written by Ian Lance Taylor <iant@google.com>. // This file is part of gold. // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, // MA 02110-1301, USA. #ifndef GOLD_MERGE_H #define GOLD_MERGE_H #include <climits> #include <map> #include <vector> #include "stringpool.h" #include "output.h" namespace gold { class Merge_map; // For each object with merge sections, we store an Object_merge_map. // This is used to map locations in input sections to a merged output // section. The output section itself is not recorded here--it can be // found in the output_sections_ field of the Object. class Object_merge_map { public: Object_merge_map() : first_shnum_(-1U), first_map_(), second_shnum_(-1U), second_map_(), section_merge_maps_() { } ~Object_merge_map(); // Add a mapping for MERGE_MAP, for the bytes from OFFSET to OFFSET // + LENGTH in the input section SHNDX to OUTPUT_OFFSET in the // output section. An OUTPUT_OFFSET of -1 means that the bytes are // discarded. OUTPUT_OFFSET is relative to the start of the merged // data in the output section. void add_mapping(const Merge_map*, unsigned int shndx, section_offset_type offset, section_size_type length, section_offset_type output_offset); // Get the output offset for an input address. MERGE_MAP is the map // we are looking for, or NULL if we don't care. The input address // is at offset OFFSET in section SHNDX. This sets *OUTPUT_OFFSET // to the offset in the output section; this will be -1 if the bytes // are not being copied to the output. This returns true if the // mapping is known, false otherwise. *OUTPUT_OFFSET is relative to // the start of the merged data in the output section. bool get_output_offset(const Merge_map*, unsigned int shndx, section_offset_type offset, section_offset_type *output_offset); // Return whether this is the merge map for section SHNDX. bool is_merge_section_for(const Merge_map*, unsigned int shndx); // Initialize an mapping from input offsets to output addresses for // section SHNDX. STARTING_ADDRESS is the output address of the // merged section. template<int size> void initialize_input_to_output_map( unsigned int shndx, typename elfcpp::Elf_types<size>::Elf_Addr starting_address, Unordered_map<section_offset_type, typename elfcpp::Elf_types<size>::Elf_Addr>*); private: // Map input section offsets to a length and an output section // offset. An output section offset of -1 means that this part of // the input section is being discarded. struct Input_merge_entry { // The offset in the input section. section_offset_type input_offset; // The length. section_size_type length; // The offset in the output section. section_offset_type output_offset; }; // A less-than comparison routine for Input_merge_entry. struct Input_merge_compare { bool operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const { return i1.input_offset < i2.input_offset; } }; // A list of entries for a particular input section. struct Input_merge_map { typedef std::vector<Input_merge_entry> Entries; // We store these with the Relobj, and we look them up by input // section. It is possible to have two different merge maps // associated with a single output section. For example, this // happens routinely with .rodata, when merged string constants // and merged fixed size constants are both put into .rodata. The // output offset that we store is not the offset from the start of // the output section; it is the offset from the start of the // merged data in the output section. That means that the caller // is going to add the offset of the merged data within the output // section, which means that the caller needs to know which set of // merged data it found the entry in. So it's not enough to find // this data based on the input section and the output section; we // also have to find it based on a set of merged data in the // output section. In order to verify that we are looking at the // right data, we store a pointer to the Merge_map here, and we // pass in a pointer when looking at the data. If we are asked to // look up information for a different Merge_map, we report that // we don't have it, rather than trying a lookup and returning an // answer which will receive the wrong offset. const Merge_map* merge_map; // The list of mappings. Entries entries; // Whether the ENTRIES field is sorted by input_offset. bool sorted; Input_merge_map() : merge_map(NULL), entries(), sorted(true) { } }; // Map input section indices to merge maps. typedef std::map<unsigned int, Input_merge_map*> Section_merge_maps; // Return a pointer to the Input_merge_map to use for the input // section SHNDX, or NULL. Input_merge_map* get_input_merge_map(unsigned int shndx); // Get or make the the Input_merge_map to use for the section SHNDX // with MERGE_MAP. Input_merge_map* get_or_make_input_merge_map(const Merge_map* merge_map, unsigned int shndx); // Any given object file will normally only have a couple of input // sections with mergeable contents. So we keep the first two input // section numbers inline, and push any further ones into a map. A // value of -1U in first_shnum_ or second_shnum_ means that we don't // have a corresponding entry. unsigned int first_shnum_; Input_merge_map first_map_; unsigned int second_shnum_; Input_merge_map second_map_; Section_merge_maps section_merge_maps_; }; // This class manages mappings from input sections to offsets in an // output section. This is used where input sections are merged. The // actual data is stored in fields in Object. class Merge_map { public: Merge_map() { } // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in the // input section SHNDX in object OBJECT to OUTPUT_OFFSET in the // output section. An OUTPUT_OFFSET of -1 means that the bytes are // discarded. OUTPUT_OFFSET is not the offset from the start of the // output section, it is the offset from the start of the merged // data within the output section. void add_mapping(Relobj* object, unsigned int shndx, section_offset_type offset, section_size_type length, section_offset_type output_offset); // Return the output offset for an input address. The input address // is at offset OFFSET in section SHNDX in OBJECT. This sets // *OUTPUT_OFFSET to the offset in the output section; this will be // -1 if the bytes are not being copied to the output. This returns // true if the mapping is known, false otherwise. This returns the // value stored by add_mapping, namely the offset from the start of // the merged data within the output section. bool get_output_offset(const Relobj* object, unsigned int shndx, section_offset_type offset, section_offset_type *output_offset) const; // Return whether this is the merge mapping for section SHNDX in // OBJECT. This should return true when get_output_offset would // return true for some input offset. bool is_merge_section_for(const Relobj* object, unsigned int shndx) const; }; // A general class for SHF_MERGE data, to hold functions shared by // fixed-size constant data and string data. class Output_merge_base : public Output_section_data { public: Output_merge_base(uint64_t entsize, uint64_t addralign) : Output_section_data(addralign), merge_map_(), entsize_(entsize) { } // Return the entry size. uint64_t entsize() const { return this->entsize_; } // Whether this is a merge string section. This is only true of // Output_merge_string. bool is_string() { return this->do_is_string(); } protected: // Return the output offset for an input offset. bool do_output_offset(const Relobj* object, unsigned int shndx, section_offset_type offset, section_offset_type* poutput) const; // Return whether this is the merge section for an input section. bool do_is_merge_section_for(const Relobj*, unsigned int shndx) const; // Add a mapping from an OFFSET in input section SHNDX in object // OBJECT to an OUTPUT_OFFSET in the output section. OUTPUT_OFFSET // is the offset from the start of the merged data in the output // section. void add_mapping(Relobj* object, unsigned int shndx, section_offset_type offset, section_size_type length, section_offset_type output_offset) { this->merge_map_.add_mapping(object, shndx, offset, length, output_offset); } // This may be overriden by the child class. virtual bool do_is_string() { return false; } private: // A mapping from input object/section/offset to offset in output // section. Merge_map merge_map_; // The entry size. For fixed-size constants, this is the size of // the constants. For strings, this is the size of a character. uint64_t entsize_; }; // Handle SHF_MERGE sections with fixed-size constant data. class Output_merge_data : public Output_merge_base { public: Output_merge_data(uint64_t entsize, uint64_t addralign) : Output_merge_base(entsize, addralign), p_(NULL), len_(0), alc_(0), input_count_(0), hashtable_(128, Merge_data_hash(this), Merge_data_eq(this)) { } protected: // Add an input section. bool do_add_input_section(Relobj* object, unsigned int shndx); // Set the final data size. void set_final_data_size(); // Write the data to the file. void do_write(Output_file*); // Write the data to a buffer. void do_write_to_buffer(unsigned char*); // Write to a map file. void do_print_to_mapfile(Mapfile* mapfile) const { mapfile->print_output_data(this, _("** merge constants")); } // Print merge stats to stderr. void do_print_merge_stats(const char* section_name); private: // We build a hash table of the fixed-size constants. Each constant // is stored as a pointer into the section data we are accumulating. // A key in the hash table. This is an offset in the section // contents we are building. typedef section_offset_type Merge_data_key; // Compute the hash code. To do this we need a pointer back to the // object holding the data. class Merge_data_hash { public: Merge_data_hash(const Output_merge_data* pomd) : pomd_(pomd) { } size_t operator()(Merge_data_key) const; private: const Output_merge_data* pomd_; }; friend class Merge_data_hash; // Compare two entries in the hash table for equality. To do this // we need a pointer back to the object holding the data. Note that // we now have a pointer to the object stored in two places in the // hash table. Fixing this would require specializing the hash // table, which would be hard to do portably. class Merge_data_eq { public: Merge_data_eq(const Output_merge_data* pomd) : pomd_(pomd) { } bool operator()(Merge_data_key k1, Merge_data_key k2) const; private: const Output_merge_data* pomd_; }; friend class Merge_data_eq; // The type of the hash table. typedef Unordered_set<Merge_data_key, Merge_data_hash, Merge_data_eq> Merge_data_hashtable; // Given a hash table key, which is just an offset into the section // data, return a pointer to the corresponding constant. const unsigned char* constant(Merge_data_key k) const { gold_assert(k >= 0 && k < static_cast<section_offset_type>(this->len_)); return this->p_ + k; } // Add a constant to the output. void add_constant(const unsigned char*); // The accumulated data. unsigned char* p_; // The length of the accumulated data. section_size_type len_; // The size of the allocated buffer. section_size_type alc_; // The number of entries seen in input files. size_t input_count_; // The hash table. Merge_data_hashtable hashtable_; }; // Handle SHF_MERGE sections with string data. This is a template // based on the type of the characters in the string. template<typename Char_type> class Output_merge_string : public Output_merge_base { public: Output_merge_string(uint64_t addralign) : Output_merge_base(sizeof(Char_type), addralign), stringpool_(), merged_strings_(), input_count_(0) { gold_assert(addralign <= sizeof(Char_type)); this->stringpool_.set_no_zero_null(); } protected: // Add an input section. bool do_add_input_section(Relobj* object, unsigned int shndx); // Do all the final processing after the input sections are read in. // Returns the final data size. section_size_type finalize_merged_data(); // Set the final data size. void set_final_data_size(); // Write the data to the file. void do_write(Output_file*); // Write the data to a buffer. void do_write_to_buffer(unsigned char*); // Write to a map file. void do_print_to_mapfile(Mapfile* mapfile) const { mapfile->print_output_data(this, _("** merge strings")); } // Print merge stats to stderr. void do_print_merge_stats(const char* section_name); // Writes the stringpool to a buffer. void stringpool_to_buffer(unsigned char* buffer, section_size_type buffer_size) { this->stringpool_.write_to_buffer(buffer, buffer_size); } // Clears all the data in the stringpool, to save on memory. void clear_stringpool() { this->stringpool_.clear(); } // Whether this is a merge string section. virtual bool do_is_string() { return true; } private: // The name of the string type, for stats. const char* string_name(); // As we see input sections, we build a mapping from object, section // index and offset to strings. struct Merged_string { // The input object where the string was found. Relobj* object; // The input section in the input object. unsigned int shndx; // The offset in the input section. section_offset_type offset; // The string itself, a pointer into a Stringpool. const Char_type* string; // The length of the string in bytes, including the null terminator. size_t length; // The key in the Stringpool. Stringpool::Key stringpool_key; Merged_string(Relobj *objecta, unsigned int shndxa, section_offset_type offseta, const Char_type* stringa, size_t lengtha, Stringpool::Key stringpool_keya) : object(objecta), shndx(shndxa), offset(offseta), string(stringa), length(lengtha), stringpool_key(stringpool_keya) { } }; typedef std::vector<Merged_string> Merged_strings; // As we see the strings, we add them to a Stringpool. Stringpool_template<Char_type> stringpool_; // Map from a location in an input object to an entry in the // Stringpool. Merged_strings merged_strings_; // The number of entries seen in input files. size_t input_count_; }; } // End namespace gold. #endif // !defined(GOLD_MERGE_H)
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