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.
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 // We build a mapping from OBJECT/SHNDX/OFFSET to an offset and
63 // length in the output section.
74 operator()(const Merge_key
&, const Merge_key
&) const;
83 typedef std::map
<Merge_key
, Merge_value
, Merge_key_less
> Merge_mapping
;
85 // A mapping from input object/section/offset to offset in output
87 Merge_mapping merge_map_
;
90 // A general class for SHF_MERGE data, to hold functions shared by
91 // fixed-size constant data and string data.
93 class Output_merge_base
: public Output_section_data
96 Output_merge_base(uint64_t entsize
, uint64_t addralign
)
97 : Output_section_data(addralign
), merge_map_(), entsize_(entsize
)
100 // Return the output offset for an input offset.
102 do_output_offset(const Relobj
* object
, unsigned int shndx
, off_t offset
,
103 off_t
* poutput
) const;
106 // Return the entry size.
109 { return this->entsize_
; }
111 // Add a mapping from an OFFSET in input section SHNDX in object
112 // OBJECT to an OUTPUT_OFFSET in the output section.
114 add_mapping(Relobj
* object
, unsigned int shndx
, off_t offset
,
115 off_t length
, off_t output_offset
)
117 this->merge_map_
.add_mapping(object
, shndx
, offset
, length
, output_offset
);
121 // A mapping from input object/section/offset to offset in output
123 Merge_map merge_map_
;
124 // The entry size. For fixed-size constants, this is the size of
125 // the constants. For strings, this is the size of a character.
129 // Handle SHF_MERGE sections with fixed-size constant data.
131 class Output_merge_data
: public Output_merge_base
134 Output_merge_data(uint64_t entsize
, uint64_t addralign
)
135 : Output_merge_base(entsize
, addralign
), p_(NULL
), len_(0), alc_(0),
136 hashtable_(128, Merge_data_hash(this), Merge_data_eq(this))
139 // Add an input section.
141 do_add_input_section(Relobj
* object
, unsigned int shndx
);
143 // Set the final data size.
145 do_set_address(uint64_t, off_t
);
147 // Write the data to the file.
149 do_write(Output_file
*);
152 // We build a hash table of the fixed-size constants. Each constant
153 // is stored as a pointer into the section data we are accumulating.
155 // A key in the hash table. This is an offset in the section
156 // contents we are building.
157 typedef off_t Merge_data_key
;
159 // Compute the hash code. To do this we need a pointer back to the
160 // object holding the data.
161 class Merge_data_hash
164 Merge_data_hash(const Output_merge_data
* pomd
)
169 operator()(Merge_data_key
) const;
172 const Output_merge_data
* pomd_
;
175 friend class Merge_data_hash
;
177 // Compare two entries in the hash table for equality. To do this
178 // we need a pointer back to the object holding the data. Note that
179 // we now have a pointer to the object stored in two places in the
180 // hash table. Fixing this would require specializing the hash
181 // table, which would be hard to do portably.
185 Merge_data_eq(const Output_merge_data
* pomd
)
190 operator()(Merge_data_key k1
, Merge_data_key k2
) const;
193 const Output_merge_data
* pomd_
;
196 friend class Merge_data_eq
;
198 // The type of the hash table.
199 typedef Unordered_set
<Merge_data_key
, Merge_data_hash
, Merge_data_eq
>
200 Merge_data_hashtable
;
202 // Given a hash table key, which is just an offset into the section
203 // data, return a pointer to the corresponding constant.
205 constant(Merge_data_key k
) const
207 gold_assert(k
>= 0 && k
< this->len_
);
211 // Add a constant to the output.
213 add_constant(const unsigned char*);
215 // The accumulated data.
217 // The length of the accumulated data.
219 // The size of the allocated buffer.
222 Merge_data_hashtable hashtable_
;
225 // Handle SHF_MERGE sections with string data. This is a template
226 // based on the type of the characters in the string.
228 template<typename Char_type
>
229 class Output_merge_string
: public Output_merge_base
232 Output_merge_string(uint64_t addralign
)
233 : Output_merge_base(sizeof(Char_type
), addralign
), stringpool_(),
236 gold_assert(addralign
<= sizeof(Char_type
));
237 this->stringpool_
.set_no_zero_null();
240 // Add an input section.
242 do_add_input_section(Relobj
* object
, unsigned int shndx
);
244 // Set the final data size.
246 do_set_address(uint64_t, off_t
);
248 // Write the data to the file.
250 do_write(Output_file
*);
253 // As we see input sections, we build a mapping from object, section
254 // index and offset to strings.
257 // The input object where the string was found.
259 // The input section in the input object.
261 // The offset in the input section.
263 // The string itself, a pointer into a Stringpool.
264 const Char_type
* string
;
265 // The length of the string in bytes, including the null terminator.
268 Merged_string(Relobj
*objecta
, unsigned int shndxa
, off_t offseta
,
269 const Char_type
* stringa
, size_t lengtha
)
270 : object(objecta
), shndx(shndxa
), offset(offseta
), string(stringa
),
275 typedef std::vector
<Merged_string
> Merged_strings
;
277 // As we see the strings, we add them to a Stringpool.
278 Stringpool_template
<Char_type
> stringpool_
;
279 // Map from a location in an input object to an entry in the
281 Merged_strings merged_strings_
;
284 } // End namespace gold.
286 #endif // !defined(GOLD_MERGE_H)