| // merge.h -- handle section merging for gold -*- C++ -*- |
| |
| // Copyright (C) 2006-2021 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 |
| { |
| |
| // 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() |
| : 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 Output_section_data*, 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(unsigned int shndx, |
| section_offset_type offset, |
| section_offset_type* output_offset); |
| |
| const Output_section_data* |
| find_merge_section(unsigned int shndx) const; |
| |
| // 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>*); |
| |
| // 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 list of entries for a particular input section. |
| struct Input_merge_map |
| { |
| void add_mapping(section_offset_type input_offset, section_size_type length, |
| section_offset_type output_offset); |
| |
| 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 Output_section_data* output_data; |
| // The list of mappings. |
| Entries entries; |
| // Whether the ENTRIES field is sorted by input_offset. |
| bool sorted; |
| |
| Input_merge_map() |
| : output_data(NULL), entries(), sorted(true) |
| { } |
| }; |
| |
| // Get or make the Input_merge_map to use for the section SHNDX |
| // with MERGE_MAP. |
| Input_merge_map* |
| get_or_make_input_merge_map(const Output_section_data* merge_map, |
| unsigned int shndx); |
| |
| private: |
| // 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; } |
| }; |
| |
| // Map input section indices to merge maps. |
| typedef std::vector<std::pair<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. |
| const Input_merge_map* |
| get_input_merge_map(unsigned int shndx) const; |
| |
| Input_merge_map * |
| get_input_merge_map(unsigned int shndx) { |
| return const_cast<Input_merge_map *>(static_cast<const Object_merge_map *>( |
| this)->get_input_merge_map(shndx)); |
| } |
| |
| Section_merge_maps section_merge_maps_; |
| }; |
| |
| // 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), entsize_(entsize), |
| keeps_input_sections_(false), first_relobj_(NULL), first_shndx_(-1), |
| input_sections_() |
| { } |
| |
| // 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(); } |
| |
| // Whether this keeps input sections. |
| bool |
| keeps_input_sections() const |
| { return this->keeps_input_sections_; } |
| |
| // Set the keeps-input-sections flag. This is virtual so that sub-classes |
| // can perform additional checks. |
| void |
| set_keeps_input_sections() |
| { this->do_set_keeps_input_sections(); } |
| |
| // Return the object of the first merged input section. This used |
| // for script processing. This is NULL if merge section is empty. |
| Relobj* |
| first_relobj() const |
| { return this->first_relobj_; } |
| |
| // Return the section index of the first merged input section. This |
| // is used for script processing. This is valid only if merge section |
| // is not valid. |
| unsigned int |
| first_shndx() const |
| { |
| gold_assert(this->first_relobj_ != NULL); |
| return this->first_shndx_; |
| } |
| |
| // Set of merged input sections. |
| typedef Unordered_set<Section_id, Section_id_hash> Input_sections; |
| |
| // Beginning of merged input sections. |
| Input_sections::const_iterator |
| input_sections_begin() const |
| { |
| gold_assert(this->keeps_input_sections_); |
| return this->input_sections_.begin(); |
| } |
| |
| // Beginning of merged input sections. |
| Input_sections::const_iterator |
| input_sections_end() const |
| { |
| gold_assert(this->keeps_input_sections_); |
| return this->input_sections_.end(); |
| } |
| |
| 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; |
| |
| // This may be overridden by the child class. |
| virtual bool |
| do_is_string() |
| { return false; } |
| |
| // This may be overridden by the child class. |
| virtual void |
| do_set_keeps_input_sections() |
| { this->keeps_input_sections_ = true; } |
| |
| // Record the merged input section for script processing. |
| void |
| record_input_section(Relobj* relobj, unsigned int shndx); |
| |
| private: |
| // 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_; |
| // Whether we keep input sections. |
| bool keeps_input_sections_; |
| // Object of the first merged input section. We use this for script |
| // processing. |
| Relobj* first_relobj_; |
| // Section index of the first merged input section. |
| unsigned int first_shndx_; |
| // Input sections. We only keep them is keeps_input_sections_ is true. |
| Input_sections input_sections_; |
| }; |
| |
| // 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); |
| |
| // Set keeps-input-sections flag. |
| void |
| do_set_keeps_input_sections() |
| { |
| gold_assert(this->input_count_ == 0); |
| Output_merge_base::do_set_keeps_input_sections(); |
| } |
| |
| 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_(addralign), |
| merged_strings_lists_(), input_count_(0), input_size_(0) |
| { |
| 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; } |
| |
| // Set keeps-input-sections flag. |
| void |
| do_set_keeps_input_sections() |
| { |
| gold_assert(this->input_count_ == 0); |
| Output_merge_base::do_set_keeps_input_sections(); |
| } |
| |
| 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 offset in the input section. |
| section_offset_type offset; |
| // The key in the Stringpool. |
| Stringpool::Key stringpool_key; |
| |
| Merged_string(section_offset_type offseta, Stringpool::Key stringpool_keya) |
| : offset(offseta), stringpool_key(stringpool_keya) |
| { } |
| }; |
| |
| typedef std::vector<Merged_string> Merged_strings; |
| |
| struct Merged_strings_list |
| { |
| // The input object where the strings were found. |
| Relobj* object; |
| // The input section in the input object. |
| unsigned int shndx; |
| // The list of merged strings. |
| Merged_strings merged_strings; |
| |
| Merged_strings_list(Relobj* objecta, unsigned int shndxa) |
| : object(objecta), shndx(shndxa), merged_strings() |
| { } |
| }; |
| |
| typedef std::vector<Merged_strings_list*> Merged_strings_lists; |
| |
| // 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_lists merged_strings_lists_; |
| // The number of entries seen in input files. |
| size_t input_count_; |
| // The total size of input sections. |
| size_t input_size_; |
| }; |
| |
| } // End namespace gold. |
| |
| #endif // !defined(GOLD_MERGE_H) |