1// descriptors.cc -- manage file descriptors for gold
2
3// Copyright 2008, 2009 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#include "gold.h"
24
25#include <cerrno>
26#include <cstdio>
27#include <cstring>
28#include <fcntl.h>
29#include <unistd.h>
30
31#include "parameters.h"
32#include "options.h"
33#include "gold-threads.h"
34#include "descriptors.h"
35#include "binary-io.h"
36
37// Very old systems may not define FD_CLOEXEC.
38#ifndef FD_CLOEXEC
39#define FD_CLOEXEC 1
40#endif
41
42// O_CLOEXEC is only available on newer systems.
43#ifndef O_CLOEXEC
44#define O_CLOEXEC 0
45#endif
46
47namespace gold
48{
49
50// Class Descriptors.
51
52// The default for limit_ is meant to simply be large.  It gets
53// adjusted downward if we run out of file descriptors.
54
55Descriptors::Descriptors()
56  : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(),
57    stack_top_(-1), current_(0), limit_(8192 - 16)
58{
59  this->open_descriptors_.reserve(128);
60}
61
62// Open a file.
63
64int
65Descriptors::open(int descriptor, const char* name, int flags, int mode)
66{
67  // We don't initialize this until we are called, because we can't
68  // initialize a Lock until we have parsed the options to find out
69  // whether we are running with threads.  We can be called before
70  // options are valid when reading a linker script.
71  bool lock_initialized = this->initialize_lock_.initialize();
72
73  gold_assert(lock_initialized || descriptor < 0);
74
75  if (descriptor >= 0)
76    {
77      Hold_lock hl(*this->lock_);
78
79      gold_assert(static_cast<size_t>(descriptor)
80		  < this->open_descriptors_.size());
81      Open_descriptor* pod = &this->open_descriptors_[descriptor];
82      if (pod->name == name
83	  || (pod->name != NULL && strcmp(pod->name, name) == 0))
84	{
85	  gold_assert(!pod->inuse);
86	  pod->inuse = true;
87	  if (descriptor == this->stack_top_)
88	    {
89	      this->stack_top_ = pod->stack_next;
90	      pod->stack_next = -1;
91	      pod->is_on_stack = false;
92	    }
93	  return descriptor;
94	}
95    }
96
97  while (true)
98    {
99      // We always want to set the close-on-exec flag; we don't
100      // require callers to pass it.
101      flags |= O_CLOEXEC;
102
103      // Always open the file as a binary file.
104      flags |= O_BINARY;
105
106      int new_descriptor = ::open(name, flags, mode);
107      if (new_descriptor < 0
108	  && errno != ENFILE
109	  && errno != EMFILE)
110	{
111	  if (descriptor >= 0 && errno == ENOENT)
112	    {
113	      {
114		Hold_lock hl(*this->lock_);
115
116		gold_error(_("file %s was removed during the link"), name);
117	      }
118
119	      errno = ENOENT;
120	    }
121
122	  return new_descriptor;
123	}
124
125      if (new_descriptor >= 0)
126	{
127	  // If we have any plugins, we really do need to set the
128	  // close-on-exec flag, even if O_CLOEXEC is not defined.
129	  // FIXME: In some cases O_CLOEXEC may be defined in the
130	  // header file but not supported by the kernel.
131	  // Unfortunately there doesn't seem to be any obvious way to
132	  // detect that, as unknown flags passed to open are ignored.
133	  if (O_CLOEXEC == 0
134	      && parameters->options_valid()
135	      && parameters->options().has_plugins())
136	    fcntl(new_descriptor, F_SETFD, FD_CLOEXEC);
137
138	  {
139	    Hold_optional_lock hl(this->lock_);
140
141	    if (static_cast<size_t>(new_descriptor)
142		>= this->open_descriptors_.size())
143	      this->open_descriptors_.resize(new_descriptor + 64);
144
145	    Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
146	    pod->name = name;
147	    pod->stack_next = -1;
148	    pod->inuse = true;
149	    pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
150	    pod->is_on_stack = false;
151
152	    ++this->current_;
153	    if (this->current_ >= this->limit_)
154	      this->close_some_descriptor();
155
156	    return new_descriptor;
157	  }
158	}
159
160      // We ran out of file descriptors.
161      {
162	Hold_optional_lock hl(this->lock_);
163
164	this->limit_ = this->current_ - 16;
165	if (this->limit_ < 8)
166	  this->limit_ = 8;
167	if (!this->close_some_descriptor())
168	  gold_fatal(_("out of file descriptors and couldn't close any"));
169      }
170    }
171}
172
173// Release a descriptor.
174
175void
176Descriptors::release(int descriptor, bool permanent)
177{
178  Hold_optional_lock hl(this->lock_);
179
180  gold_assert(descriptor >= 0
181	      && (static_cast<size_t>(descriptor)
182		  < this->open_descriptors_.size()));
183  Open_descriptor* pod = &this->open_descriptors_[descriptor];
184
185  if (permanent
186      || (this->current_ > this->limit_ && !pod->is_write))
187    {
188      if (::close(descriptor) < 0)
189	gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
190      pod->name = NULL;
191      --this->current_;
192    }
193  else
194    {
195      pod->inuse = false;
196      if (!pod->is_write && !pod->is_on_stack)
197	{
198	  pod->stack_next = this->stack_top_;
199	  this->stack_top_ = descriptor;
200	  pod->is_on_stack = true;
201	}
202    }
203}
204
205// Close some descriptor.  The lock is held when this is called.  We
206// close the descriptor on the top of the free stack.  Note that this
207// is the opposite of an LRU algorithm--we close the most recently
208// used descriptor.  That is because the linker tends to cycle through
209// all the files; after we release a file, we are unlikely to need it
210// again until we have looked at all the other files.  Return true if
211// we closed a descriptor.
212
213bool
214Descriptors::close_some_descriptor()
215{
216  int last = -1;
217  int i = this->stack_top_;
218  while (i >= 0)
219    {
220      gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
221      Open_descriptor* pod = &this->open_descriptors_[i];
222      if (!pod->inuse && !pod->is_write)
223	{
224	  if (::close(i) < 0)
225	    gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
226	  --this->current_;
227	  pod->name = NULL;
228	  if (last < 0)
229	    this->stack_top_ = pod->stack_next;
230	  else
231	    this->open_descriptors_[last].stack_next = pod->stack_next;
232	  pod->stack_next = -1;
233	  pod->is_on_stack = false;
234	  return true;
235	}
236      last = i;
237      i = pod->stack_next;
238    }
239
240  // We couldn't find any descriptors to close.  This is weird but not
241  // necessarily an error.
242  return false;
243}
244
245// The single global variable which manages descriptors.
246
247Descriptors descriptors;
248
249} // End namespace gold.
250