aboutsummaryrefslogtreecommitdiff
path: root/gold/fileread.h
blob: 4236ce0ccef66edae4275d05a02a8ff512205973 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
// fileread.h -- read files 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.

// Classes used to read data from binary input files.

#ifndef GOLD_FILEREAD_H
#define GOLD_FILEREAD_H

#include <list>
#include <map>
#include <string>
#include <vector>

#include "token.h"

namespace gold
{

class Position_dependent_options;
class Input_file_argument;
class Dirsearch;
class File_view;

// File_read manages a file descriptor and mappings for a file we are
// reading.

class File_read
{
 public:
  File_read()
    : name_(), descriptor_(-1), is_descriptor_opened_(false), object_count_(0),
      size_(0), token_(false), views_(), saved_views_(), contents_(NULL),
      mapped_bytes_(0), released_(true)
  { }

  ~File_read();

  // Open a file.
  bool
  open(const Task*, const std::string& name);

  // Pretend to open the file, but provide the file contents.  No
  // actual file system activity will occur.  This is used for
  // testing.
  bool
  open(const Task*, const std::string& name, const unsigned char* contents,
       off_t size);

  // Return the file name.
  const std::string&
  filename() const
  { return this->name_; }

  // Add an object associated with a file.
  void
  add_object()
  { ++this->object_count_; }

  // Remove an object associated with a file.
  void
  remove_object()
  { --this->object_count_; }

  // Lock the file for exclusive access within a particular Task::run
  // execution.  This routine may only be called when the workqueue
  // lock is held.
  void
  lock(const Task* t);

  // Unlock the file.
  void
  unlock(const Task* t);

  // Test whether the object is locked.
  bool
  is_locked() const;

  // Return the token, so that the task can be queued.
  Task_token*
  token()
  { return &this->token_; }

  // Release the file.  This indicates that we aren't going to do
  // anything further with it until it is unlocked.  This is used
  // because a Task which locks the file never calls either lock or
  // unlock; it just locks the token.  The basic rule is that a Task
  // which locks a file via the Task::locks interface must explicitly
  // call release() when it is done.  This is not necessary for code
  // which calls unlock() on the file.
  void
  release();

  // Return the size of the file.
  off_t
  filesize() const
  { return this->size_; }

  // Return a view into the file starting at file offset START for
  // SIZE bytes.  OFFSET is the offset into the input file for the
  // file we are reading; this is zero for a normal object file,
  // non-zero for an object file in an archive.  ALIGNED is true if
  // the data must be naturally aligned; this only matters when OFFSET
  // is not zero.  The pointer will remain valid until the File_read
  // is unlocked.  It is an error if we can not read enough data from
  // the file.  The CACHE parameter is a hint as to whether it will be
  // useful to cache this data for later accesses--i.e., later calls
  // to get_view, read, or get_lasting_view which retrieve the same
  // data.
  const unsigned char*
  get_view(off_t offset, off_t start, section_size_type size, bool aligned,
	   bool cache);

  // Read data from the file into the buffer P starting at file offset
  // START for SIZE bytes.
  void
  read(off_t start, section_size_type size, void* p);

  // Return a lasting view into the file starting at file offset START
  // for SIZE bytes.  This is allocated with new, and the caller is
  // responsible for deleting it when done.  The data associated with
  // this view will remain valid until the view is deleted.  It is an
  // error if we can not read enough data from the file.  The OFFSET,
  // ALIGNED and CACHE parameters are as in get_view.
  File_view*
  get_lasting_view(off_t offset, off_t start, section_size_type size,
		   bool aligned, bool cache);

  // Mark all views as no longer cached.
  void
  clear_view_cache_marks();

  // Discard all uncached views.  This is normally done by release(),
  // but not for objects in archives.  FIXME: This is a complicated
  // interface, and it would be nice to have something more automatic.
  void
  clear_uncached_views()
  { this->clear_views(false); }

  // A struct used to do a multiple read.
  struct Read_multiple_entry
  {
    // The file offset of the data to read.
    off_t file_offset;
    // The amount of data to read.
    section_size_type size;
    // The buffer where the data should be placed.
    unsigned char* buffer;

    Read_multiple_entry(off_t o, section_size_type s, unsigned char* b)
      : file_offset(o), size(s), buffer(b)
    { }
  };

  typedef std::vector<Read_multiple_entry> Read_multiple;

  // Read a bunch of data from the file into various different
  // locations.  The vector must be sorted by ascending file_offset.
  // BASE is a base offset to be added to all the offsets in the
  // vector.
  void
  read_multiple(off_t base, const Read_multiple&);

  // Dump statistical information to stderr.
  static void
  print_stats();

 private:
  // This class may not be copied.
  File_read(const File_read&);
  File_read& operator=(const File_read&);

  // Total bytes mapped into memory during the link.  This variable
  // may not be accurate when running multi-threaded.
  static unsigned long long total_mapped_bytes;

  // Current number of bytes mapped into memory during the link.  This
  // variable may not be accurate when running multi-threaded.
  static unsigned long long current_mapped_bytes;

  // High water mark of bytes mapped into memory during the link.
  // This variable may not be accurate when running multi-threaded.
  static unsigned long long maximum_mapped_bytes;

  // A view into the file.
  class View
  {
   public:
    View(off_t start, section_size_type size, const unsigned char* data,
	 unsigned int byteshift, bool cache, bool mapped)
      : start_(start), size_(size), data_(data), lock_count_(0),
	byteshift_(byteshift), cache_(cache), mapped_(mapped), accessed_(true)
    { }

    ~View();

    off_t
    start() const
    { return this->start_; }

    section_size_type
    size() const
    { return this->size_; }

    const unsigned char*
    data() const
    { return this->data_; }

    void
    lock();

    void
    unlock();

    bool
    is_locked();

    unsigned int
    byteshift() const
    { return this->byteshift_; }

    void
    set_cache()
    { this->cache_ = true; }

    void
    clear_cache()
    { this->cache_ = false; }

    bool
    should_cache() const
    { return this->cache_; }

    void
    set_accessed()
    { this->accessed_ = true; }

    void
    clear_accessed()
    { this->accessed_= false; }

    bool
    accessed() const
    { return this->accessed_; }

   private:
    View(const View&);
    View& operator=(const View&);

    // The file offset of the start of the view.
    off_t start_;
    // The size of the view.
    section_size_type size_;
    // A pointer to the actual bytes.
    const unsigned char* data_;
    // The number of locks on this view.
    int lock_count_;
    // The number of bytes that the view is shifted relative to the
    // underlying file.  This is used to align data.  This is normally
    // zero, except possibly for an object in an archive.
    unsigned int byteshift_;
    // Whether the view is cached.
    bool cache_;
    // Whether the view is mapped into memory.  If not, data_ points
    // to memory allocated using new[].
    bool mapped_;
    // Whether the view has been accessed recently.
    bool accessed_;
  };

  friend class View;
  friend class File_view;

  // The type of a mapping from page start and byte shift to views.
  typedef std::map<std::pair<off_t, unsigned int>, View*> Views;

  // A simple list of Views.
  typedef std::list<View*> Saved_views;

  // Open the descriptor if necessary.
  void
  reopen_descriptor();

  // Find a view into the file.
  View*
  find_view(off_t start, section_size_type size, unsigned int byteshift,
	    View** vshifted) const;

  // Read data from the file into a buffer.
  void
  do_read(off_t start, section_size_type size, void* p);

  // Add a view.
  void
  add_view(View*);

  // Make a view into the file.
  View*
  make_view(off_t start, section_size_type size, unsigned int byteshift,
	    bool cache);

  // Find or make a view into the file.
  View*
  find_or_make_view(off_t offset, off_t start, section_size_type size,
		    bool aligned, bool cache);

  // Clear the file views.
  void
  clear_views(bool);

  // The size of a file page for buffering data.
  static const off_t page_size = 8192;

  // Given a file offset, return the page offset.
  static off_t
  page_offset(off_t file_offset)
  { return file_offset & ~ (page_size - 1); }

  // Given a file size, return the size to read integral pages.
  static off_t
  pages(off_t file_size)
  { return (file_size + (page_size - 1)) & ~ (page_size - 1); }

  // The maximum number of entries we will pass to ::readv.
  static const size_t max_readv_entries = 128;

  // Use readv to read data.
  void
  do_readv(off_t base, const Read_multiple&, size_t start, size_t count);

  // File name.
  std::string name_;
  // File descriptor.
  int descriptor_;
  // Whether we have regained the descriptor after releasing the file.
  bool is_descriptor_opened_;
  // The number of objects associated with this file.  This will be
  // more than 1 in the case of an archive.
  int object_count_;
  // File size.
  off_t size_;
  // A token used to lock the file.
  Task_token token_;
  // Buffered views into the file.
  Views views_;
  // List of views which were locked but had to be removed from views_
  // because they were not large enough.
  Saved_views saved_views_;
  // Specified file contents.  Used only for testing purposes.
  const unsigned char* contents_;
  // Total amount of space mapped into memory.  This is only changed
  // while the file is locked.  When we unlock the file, we transfer
  // the total to total_mapped_bytes, and reset this to zero.
  size_t mapped_bytes_;
  // Whether the file was released.
  bool released_;
};

// A view of file data that persists even when the file is unlocked.
// Callers should destroy these when no longer required.  These are
// obtained form File_read::get_lasting_view.  They may only be
// destroyed when the underlying File_read is locked.

class File_view
{
 public:
  // This may only be called when the underlying File_read is locked.
  ~File_view();

  // Return a pointer to the data associated with this view.
  const unsigned char*
  data() const
  { return this->data_; }

 private:
  File_view(const File_view&);
  File_view& operator=(const File_view&);

  friend class File_read;

  // Callers have to get these via File_read::get_lasting_view.
  File_view(File_read& file, File_read::View* view, const unsigned char* data)
    : file_(file), view_(view), data_(data)
  { }

  File_read& file_;
  File_read::View* view_;
  const unsigned char* data_;
};

// All the information we hold for a single input file.  This can be
// an object file, a shared library, or an archive.

class Input_file
{
 public:
  Input_file(const Input_file_argument* input_argument)
    : input_argument_(input_argument), found_name_(), file_(),
      is_in_sysroot_(false)
  { }

  // Create an input file with the contents already provided.  This is
  // only used for testing.  With this path, don't call the open
  // method.
  Input_file(const Task*, const char* name, const unsigned char* contents,
	     off_t size);

  // Open the file.  If the open fails, this will report an error and
  // return false.
  bool
  open(const General_options&, const Dirsearch&, const Task*);

  // Return the name given by the user.  For -lc this will return "c".
  const char*
  name() const;

  // Return the file name.  For -lc this will return something like
  // "/usr/lib/libc.so".
  const std::string&
  filename() const
  { return this->file_.filename(); }

  // Return the name under which we found the file, corresponding to
  // the command line.  For -lc this will return something like
  // "libc.so".
  const std::string&
  found_name() const
  { return this->found_name_; }

  // Return the position dependent options.
  const Position_dependent_options&
  options() const;

  // Return the file.
  File_read&
  file()
  { return this->file_; }

  const File_read&
  file() const
  { return this->file_; }

  // Whether we found the file in a directory in the system root.
  bool
  is_in_sysroot() const
  { return this->is_in_sysroot_; }

  // Return whether this file is to be read only for its symbols.
  bool
  just_symbols() const;

 private:
  Input_file(const Input_file&);
  Input_file& operator=(const Input_file&);

  // Open a binary file.
  bool
  open_binary(const General_options&, const Task* task,
	      const std::string& name);

  // The argument from the command line.
  const Input_file_argument* input_argument_;
  // The name under which we opened the file.  This is like the name
  // on the command line, but -lc turns into libc.so (or whatever).
  // It only includes the full path if the path was on the command
  // line.
  std::string found_name_;
  // The file after we open it.
  File_read file_;
  // Whether we found the file in a directory in the system root.
  bool is_in_sysroot_;
};

} // end namespace gold

#endif // !defined(GOLD_FILEREAD_H)