1 // merge.h -- handle section merging for gold -*- C++ -*-
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
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.
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.
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.
28 #include "stringpool.h"
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.
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
49 add_mapping(Relobj
* object
, unsigned int shndx
, off_t offset
, off_t length
,
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.
58 get_output_offset(const Relobj
* object
, unsigned int shndx
, off_t offset
,
59 off_t
*output_offset
) const;
62 // A general class for SHF_MERGE data, to hold functions shared by
63 // fixed-size constant data and string data.
65 class Output_merge_base
: public Output_section_data
68 Output_merge_base(uint64_t entsize
, uint64_t addralign
)
69 : Output_section_data(addralign
), merge_map_(), entsize_(entsize
)
72 // Return the output offset for an input offset.
74 do_output_offset(const Relobj
* object
, unsigned int shndx
, off_t offset
,
75 off_t
* poutput
) const;
78 // Return the entry size.
81 { return this->entsize_
; }
83 // Add a mapping from an OFFSET in input section SHNDX in object
84 // OBJECT to an OUTPUT_OFFSET in the output section.
86 add_mapping(Relobj
* object
, unsigned int shndx
, off_t offset
,
87 off_t length
, off_t output_offset
)
89 this->merge_map_
.add_mapping(object
, shndx
, offset
, length
, output_offset
);
93 // A mapping from input object/section/offset to offset in output
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.
101 // Handle SHF_MERGE sections with fixed-size constant data.
103 class Output_merge_data
: public Output_merge_base
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))
111 // Add an input section.
113 do_add_input_section(Relobj
* object
, unsigned int shndx
);
115 // Set the final data size.
117 set_final_data_size();
119 // Write the data to the file.
121 do_write(Output_file
*);
123 // Write the data to a buffer.
125 do_write_to_buffer(unsigned char*);
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.
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
;
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
140 Merge_data_hash(const Output_merge_data
* pomd
)
145 operator()(Merge_data_key
) const;
148 const Output_merge_data
* pomd_
;
151 friend class Merge_data_hash
;
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.
161 Merge_data_eq(const Output_merge_data
* pomd
)
166 operator()(Merge_data_key k1
, Merge_data_key k2
) const;
169 const Output_merge_data
* pomd_
;
172 friend class Merge_data_eq
;
174 // The type of the hash table.
175 typedef Unordered_set
<Merge_data_key
, Merge_data_hash
, Merge_data_eq
>
176 Merge_data_hashtable
;
178 // Given a hash table key, which is just an offset into the section
179 // data, return a pointer to the corresponding constant.
181 constant(Merge_data_key k
) const
183 gold_assert(k
>= 0 && k
< this->len_
);
187 // Add a constant to the output.
189 add_constant(const unsigned char*);
191 // The accumulated data.
193 // The length of the accumulated data.
195 // The size of the allocated buffer.
198 Merge_data_hashtable hashtable_
;
201 // Handle SHF_MERGE sections with string data. This is a template
202 // based on the type of the characters in the string.
204 template<typename Char_type
>
205 class Output_merge_string
: public Output_merge_base
208 Output_merge_string(uint64_t addralign
)
209 : Output_merge_base(sizeof(Char_type
), addralign
), stringpool_(),
212 gold_assert(addralign
<= sizeof(Char_type
));
213 this->stringpool_
.set_no_zero_null();
217 // Add an input section.
219 do_add_input_section(Relobj
* object
, unsigned int shndx
);
221 // Do all the final processing after the input sections are read in.
222 // Returns the final data size.
224 finalize_merged_data();
226 // Set the final data size.
228 set_final_data_size();
230 // Write the data to the file.
232 do_write(Output_file
*);
234 // Write the data to a buffer.
236 do_write_to_buffer(unsigned char*);
238 // Writes the stringpool to a buffer.
240 stringpool_to_buffer(unsigned char* buffer
, size_t buffer_size
)
241 { this->stringpool_
.write_to_buffer(buffer
, buffer_size
); }
243 // Clears all the data in the stringpool, to save on memory.
246 { stringpool_
.clear(); }
249 // As we see input sections, we build a mapping from object, section
250 // index and offset to strings.
253 // The input object where the string was found.
255 // The input section in the input object.
257 // The offset in the input section.
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.
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
),
271 typedef std::vector
<Merged_string
> Merged_strings
;
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
277 Merged_strings merged_strings_
;
280 } // End namespace gold.
282 #endif // !defined(GOLD_MERGE_H)