| 1 | // merge.h -- handle section merging for gold -*- C++ -*- |
| 2 | |
| 3 | // Copyright 2006, 2007 Free Software Foundation, Inc. |
| 4 | // Written by Ian Lance Taylor <iant@google.com>. |
| 5 | |
| 6 | // This file is part of gold. |
| 7 | |
| 8 | // This program is free software; you can redistribute it and/or modify |
| 9 | // it under the terms of the GNU General Public License as published by |
| 10 | // the Free Software Foundation; either version 3 of the License, or |
| 11 | // (at your option) any later version. |
| 12 | |
| 13 | // This program is distributed in the hope that it will be useful, |
| 14 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | // GNU General Public License for more details. |
| 17 | |
| 18 | // You should have received a copy of the GNU General Public License |
| 19 | // along with this program; if not, write to the Free Software |
| 20 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, |
| 21 | // MA 02110-1301, USA. |
| 22 | |
| 23 | #ifndef GOLD_MERGE_H |
| 24 | #define GOLD_MERGE_H |
| 25 | |
| 26 | #include <climits> |
| 27 | |
| 28 | #include "stringpool.h" |
| 29 | #include "output.h" |
| 30 | |
| 31 | namespace gold |
| 32 | { |
| 33 | |
| 34 | // This class manages mappings from input sections to offsets in an |
| 35 | // output section. This is used where input sections are merged. The |
| 36 | // actual data is stored in fields in Object. |
| 37 | |
| 38 | class Merge_map |
| 39 | { |
| 40 | public: |
| 41 | Merge_map() |
| 42 | { } |
| 43 | |
| 44 | // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in the |
| 45 | // input section SHNDX in object OBJECT to OUTPUT_OFFSET in the |
| 46 | // output section. An OUTPUT_OFFSET of -1 means that the bytes are |
| 47 | // discarded. |
| 48 | void |
| 49 | add_mapping(Relobj* object, unsigned int shndx, off_t offset, off_t length, |
| 50 | off_t output_offset); |
| 51 | |
| 52 | // Return the output offset for an input address. The input address |
| 53 | // is at offset OFFSET in section SHNDX in OBJECT. This sets |
| 54 | // *OUTPUT_OFFSET to the offset in the output section; this will be |
| 55 | // -1 if the bytes are not being copied to the output. This returns |
| 56 | // true if the mapping is known, false otherwise. |
| 57 | bool |
| 58 | get_output_offset(const Relobj* object, unsigned int shndx, off_t offset, |
| 59 | off_t *output_offset) const; |
| 60 | }; |
| 61 | |
| 62 | // A general class for SHF_MERGE data, to hold functions shared by |
| 63 | // fixed-size constant data and string data. |
| 64 | |
| 65 | class Output_merge_base : public Output_section_data |
| 66 | { |
| 67 | public: |
| 68 | Output_merge_base(uint64_t entsize, uint64_t addralign) |
| 69 | : Output_section_data(addralign), merge_map_(), entsize_(entsize) |
| 70 | { } |
| 71 | |
| 72 | // Return the output offset for an input offset. |
| 73 | bool |
| 74 | do_output_offset(const Relobj* object, unsigned int shndx, off_t offset, |
| 75 | off_t* poutput) const; |
| 76 | |
| 77 | protected: |
| 78 | // Return the entry size. |
| 79 | uint64_t |
| 80 | entsize() const |
| 81 | { return this->entsize_; } |
| 82 | |
| 83 | // Add a mapping from an OFFSET in input section SHNDX in object |
| 84 | // OBJECT to an OUTPUT_OFFSET in the output section. |
| 85 | void |
| 86 | add_mapping(Relobj* object, unsigned int shndx, off_t offset, |
| 87 | off_t length, off_t output_offset) |
| 88 | { |
| 89 | this->merge_map_.add_mapping(object, shndx, offset, length, output_offset); |
| 90 | } |
| 91 | |
| 92 | private: |
| 93 | // A mapping from input object/section/offset to offset in output |
| 94 | // section. |
| 95 | Merge_map merge_map_; |
| 96 | // The entry size. For fixed-size constants, this is the size of |
| 97 | // the constants. For strings, this is the size of a character. |
| 98 | uint64_t entsize_; |
| 99 | }; |
| 100 | |
| 101 | // Handle SHF_MERGE sections with fixed-size constant data. |
| 102 | |
| 103 | class Output_merge_data : public Output_merge_base |
| 104 | { |
| 105 | public: |
| 106 | Output_merge_data(uint64_t entsize, uint64_t addralign) |
| 107 | : Output_merge_base(entsize, addralign), p_(NULL), len_(0), alc_(0), |
| 108 | hashtable_(128, Merge_data_hash(this), Merge_data_eq(this)) |
| 109 | { } |
| 110 | |
| 111 | // Add an input section. |
| 112 | bool |
| 113 | do_add_input_section(Relobj* object, unsigned int shndx); |
| 114 | |
| 115 | // Set the final data size. |
| 116 | void |
| 117 | set_final_data_size(); |
| 118 | |
| 119 | // Write the data to the file. |
| 120 | void |
| 121 | do_write(Output_file*); |
| 122 | |
| 123 | // Write the data to a buffer. |
| 124 | void |
| 125 | do_write_to_buffer(unsigned char*); |
| 126 | |
| 127 | private: |
| 128 | // We build a hash table of the fixed-size constants. Each constant |
| 129 | // is stored as a pointer into the section data we are accumulating. |
| 130 | |
| 131 | // A key in the hash table. This is an offset in the section |
| 132 | // contents we are building. |
| 133 | typedef off_t Merge_data_key; |
| 134 | |
| 135 | // Compute the hash code. To do this we need a pointer back to the |
| 136 | // object holding the data. |
| 137 | class Merge_data_hash |
| 138 | { |
| 139 | public: |
| 140 | Merge_data_hash(const Output_merge_data* pomd) |
| 141 | : pomd_(pomd) |
| 142 | { } |
| 143 | |
| 144 | size_t |
| 145 | operator()(Merge_data_key) const; |
| 146 | |
| 147 | private: |
| 148 | const Output_merge_data* pomd_; |
| 149 | }; |
| 150 | |
| 151 | friend class Merge_data_hash; |
| 152 | |
| 153 | // Compare two entries in the hash table for equality. To do this |
| 154 | // we need a pointer back to the object holding the data. Note that |
| 155 | // we now have a pointer to the object stored in two places in the |
| 156 | // hash table. Fixing this would require specializing the hash |
| 157 | // table, which would be hard to do portably. |
| 158 | class Merge_data_eq |
| 159 | { |
| 160 | public: |
| 161 | Merge_data_eq(const Output_merge_data* pomd) |
| 162 | : pomd_(pomd) |
| 163 | { } |
| 164 | |
| 165 | bool |
| 166 | operator()(Merge_data_key k1, Merge_data_key k2) const; |
| 167 | |
| 168 | private: |
| 169 | const Output_merge_data* pomd_; |
| 170 | }; |
| 171 | |
| 172 | friend class Merge_data_eq; |
| 173 | |
| 174 | // The type of the hash table. |
| 175 | typedef Unordered_set<Merge_data_key, Merge_data_hash, Merge_data_eq> |
| 176 | Merge_data_hashtable; |
| 177 | |
| 178 | // Given a hash table key, which is just an offset into the section |
| 179 | // data, return a pointer to the corresponding constant. |
| 180 | const unsigned char* |
| 181 | constant(Merge_data_key k) const |
| 182 | { |
| 183 | gold_assert(k >= 0 && k < this->len_); |
| 184 | return this->p_ + k; |
| 185 | } |
| 186 | |
| 187 | // Add a constant to the output. |
| 188 | void |
| 189 | add_constant(const unsigned char*); |
| 190 | |
| 191 | // The accumulated data. |
| 192 | unsigned char* p_; |
| 193 | // The length of the accumulated data. |
| 194 | off_t len_; |
| 195 | // The size of the allocated buffer. |
| 196 | size_t alc_; |
| 197 | // The hash table. |
| 198 | Merge_data_hashtable hashtable_; |
| 199 | }; |
| 200 | |
| 201 | // Handle SHF_MERGE sections with string data. This is a template |
| 202 | // based on the type of the characters in the string. |
| 203 | |
| 204 | template<typename Char_type> |
| 205 | class Output_merge_string : public Output_merge_base |
| 206 | { |
| 207 | public: |
| 208 | Output_merge_string(uint64_t addralign) |
| 209 | : Output_merge_base(sizeof(Char_type), addralign), stringpool_(), |
| 210 | merged_strings_() |
| 211 | { |
| 212 | gold_assert(addralign <= sizeof(Char_type)); |
| 213 | this->stringpool_.set_no_zero_null(); |
| 214 | } |
| 215 | |
| 216 | protected: |
| 217 | // Add an input section. |
| 218 | bool |
| 219 | do_add_input_section(Relobj* object, unsigned int shndx); |
| 220 | |
| 221 | // Do all the final processing after the input sections are read in. |
| 222 | // Returns the final data size. |
| 223 | off_t |
| 224 | finalize_merged_data(); |
| 225 | |
| 226 | // Set the final data size. |
| 227 | void |
| 228 | set_final_data_size(); |
| 229 | |
| 230 | // Write the data to the file. |
| 231 | void |
| 232 | do_write(Output_file*); |
| 233 | |
| 234 | // Write the data to a buffer. |
| 235 | void |
| 236 | do_write_to_buffer(unsigned char*); |
| 237 | |
| 238 | // Writes the stringpool to a buffer. |
| 239 | void |
| 240 | stringpool_to_buffer(unsigned char* buffer, size_t buffer_size) |
| 241 | { this->stringpool_.write_to_buffer(buffer, buffer_size); } |
| 242 | |
| 243 | // Clears all the data in the stringpool, to save on memory. |
| 244 | void |
| 245 | clear_stringpool() |
| 246 | { stringpool_.clear(); } |
| 247 | |
| 248 | private: |
| 249 | // As we see input sections, we build a mapping from object, section |
| 250 | // index and offset to strings. |
| 251 | struct Merged_string |
| 252 | { |
| 253 | // The input object where the string was found. |
| 254 | Relobj* object; |
| 255 | // The input section in the input object. |
| 256 | unsigned int shndx; |
| 257 | // The offset in the input section. |
| 258 | off_t offset; |
| 259 | // The string itself, a pointer into a Stringpool. |
| 260 | const Char_type* string; |
| 261 | // The length of the string in bytes, including the null terminator. |
| 262 | size_t length; |
| 263 | |
| 264 | Merged_string(Relobj *objecta, unsigned int shndxa, off_t offseta, |
| 265 | const Char_type* stringa, size_t lengtha) |
| 266 | : object(objecta), shndx(shndxa), offset(offseta), string(stringa), |
| 267 | length(lengtha) |
| 268 | { } |
| 269 | }; |
| 270 | |
| 271 | typedef std::vector<Merged_string> Merged_strings; |
| 272 | |
| 273 | // As we see the strings, we add them to a Stringpool. |
| 274 | Stringpool_template<Char_type> stringpool_; |
| 275 | // Map from a location in an input object to an entry in the |
| 276 | // Stringpool. |
| 277 | Merged_strings merged_strings_; |
| 278 | }; |
| 279 | |
| 280 | } // End namespace gold. |
| 281 | |
| 282 | #endif // !defined(GOLD_MERGE_H) |