1 // descriptors.cc -- manage file descriptors for gold
2
3 // Copyright (C) 2008-2016 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 "debug.h"
32 #include "parameters.h"
33 #include "options.h"
34 #include "gold-threads.h"
35 #include "descriptors.h"
36 #include "binary-io.h"
37
38 // O_CLOEXEC is only available on newer systems.
39 #ifndef O_CLOEXEC
40 #define O_CLOEXEC 0
41 #endif
42
43 // Very old systems may not define FD_CLOEXEC.
44 #ifndef FD_CLOEXEC
45 #define FD_CLOEXEC 1
46 #endif
47
48 static inline void
set_close_on_exec(int fd ATTRIBUTE_UNUSED)49 set_close_on_exec(int fd ATTRIBUTE_UNUSED)
50 {
51 // Mingw does not define F_SETFD.
52 #ifdef F_SETFD
53 fcntl(fd, F_SETFD, FD_CLOEXEC);
54 #endif
55 }
56
57 namespace gold
58 {
59
60 // Class Descriptors.
61
62 // The default for limit_ is meant to simply be large. It gets
63 // adjusted downward if we run out of file descriptors.
64
Descriptors()65 Descriptors::Descriptors()
66 : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(),
67 stack_top_(-1), current_(0), limit_(8192 - 16)
68 {
69 this->open_descriptors_.reserve(128);
70 }
71
72 // Open a file.
73
74 int
open(int descriptor,const char * name,int flags,int mode)75 Descriptors::open(int descriptor, const char* name, int flags, int mode)
76 {
77 // We don't initialize this until we are called, because we can't
78 // initialize a Lock until we have parsed the options to find out
79 // whether we are running with threads. We can be called before
80 // options are valid when reading a linker script.
81 bool lock_initialized = this->initialize_lock_.initialize();
82
83 gold_assert(lock_initialized || descriptor < 0);
84
85 if (is_debugging_enabled(DEBUG_FILES))
86 this->limit_ = 8;
87
88 if (descriptor >= 0)
89 {
90 Hold_lock hl(*this->lock_);
91
92 gold_assert(static_cast<size_t>(descriptor)
93 < this->open_descriptors_.size());
94 Open_descriptor* pod = &this->open_descriptors_[descriptor];
95 if (pod->name == name
96 || (pod->name != NULL && strcmp(pod->name, name) == 0))
97 {
98 gold_assert(!pod->inuse);
99 pod->inuse = true;
100 if (descriptor == this->stack_top_)
101 {
102 this->stack_top_ = pod->stack_next;
103 pod->stack_next = -1;
104 pod->is_on_stack = false;
105 }
106 gold_debug(DEBUG_FILES, "Reused existing descriptor %d for \"%s\"",
107 descriptor, name);
108 return descriptor;
109 }
110 }
111
112 while (true)
113 {
114 // We always want to set the close-on-exec flag; we don't
115 // require callers to pass it.
116 flags |= O_CLOEXEC;
117
118 // Always open the file as a binary file.
119 flags |= O_BINARY;
120
121 int new_descriptor = ::open(name, flags, mode);
122 if (new_descriptor < 0
123 && errno != ENFILE
124 && errno != EMFILE)
125 {
126 if (descriptor >= 0 && errno == ENOENT)
127 {
128 {
129 Hold_lock hl(*this->lock_);
130
131 gold_error(_("file %s was removed during the link"), name);
132 }
133
134 errno = ENOENT;
135 }
136
137 gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"",
138 new_descriptor, name);
139 return new_descriptor;
140 }
141
142 if (new_descriptor >= 0)
143 {
144 // If we have any plugins, we really do need to set the
145 // close-on-exec flag, even if O_CLOEXEC is not defined.
146 // FIXME: In some cases O_CLOEXEC may be defined in the
147 // header file but not supported by the kernel.
148 // Unfortunately there doesn't seem to be any obvious way to
149 // detect that, as unknown flags passed to open are ignored.
150 if (O_CLOEXEC == 0
151 && parameters->options_valid()
152 && parameters->options().has_plugins())
153 set_close_on_exec(new_descriptor);
154
155 {
156 Hold_optional_lock hl(this->lock_);
157
158 if (static_cast<size_t>(new_descriptor)
159 >= this->open_descriptors_.size())
160 this->open_descriptors_.resize(new_descriptor + 64);
161
162 Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
163 pod->name = name;
164 pod->stack_next = -1;
165 pod->inuse = true;
166 pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
167 pod->is_on_stack = false;
168
169 ++this->current_;
170 if (this->current_ >= this->limit_)
171 this->close_some_descriptor();
172
173 gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"",
174 new_descriptor, name);
175 return new_descriptor;
176 }
177 }
178
179 // We ran out of file descriptors.
180 {
181 Hold_optional_lock hl(this->lock_);
182
183 this->limit_ = this->current_ - 16;
184 if (this->limit_ < 8)
185 this->limit_ = 8;
186 if (!this->close_some_descriptor())
187 gold_fatal(_("out of file descriptors and couldn't close any"));
188 }
189 }
190 }
191
192 // Release a descriptor.
193
194 void
release(int descriptor,bool permanent)195 Descriptors::release(int descriptor, bool permanent)
196 {
197 Hold_optional_lock hl(this->lock_);
198
199 gold_assert(descriptor >= 0
200 && (static_cast<size_t>(descriptor)
201 < this->open_descriptors_.size()));
202 Open_descriptor* pod = &this->open_descriptors_[descriptor];
203
204 if (permanent
205 || (this->current_ > this->limit_ && !pod->is_write))
206 {
207 if (::close(descriptor) < 0)
208 gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
209 pod->name = NULL;
210 --this->current_;
211 }
212 else
213 {
214 pod->inuse = false;
215 if (!pod->is_write && !pod->is_on_stack)
216 {
217 pod->stack_next = this->stack_top_;
218 this->stack_top_ = descriptor;
219 pod->is_on_stack = true;
220 }
221 }
222
223 gold_debug(DEBUG_FILES, "Released descriptor %d for \"%s\"",
224 descriptor, pod->name);
225 }
226
227 // Close some descriptor. The lock is held when this is called. We
228 // close the descriptor on the top of the free stack. Note that this
229 // is the opposite of an LRU algorithm--we close the most recently
230 // used descriptor. That is because the linker tends to cycle through
231 // all the files; after we release a file, we are unlikely to need it
232 // again until we have looked at all the other files. Return true if
233 // we closed a descriptor.
234
235 bool
close_some_descriptor()236 Descriptors::close_some_descriptor()
237 {
238 int last = -1;
239 int i = this->stack_top_;
240 while (i >= 0)
241 {
242 gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
243 Open_descriptor* pod = &this->open_descriptors_[i];
244 if (!pod->inuse && !pod->is_write)
245 {
246 if (::close(i) < 0)
247 gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
248 --this->current_;
249 gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\"",
250 i, pod->name);
251 pod->name = NULL;
252 if (last < 0)
253 this->stack_top_ = pod->stack_next;
254 else
255 this->open_descriptors_[last].stack_next = pod->stack_next;
256 pod->stack_next = -1;
257 pod->is_on_stack = false;
258 return true;
259 }
260 last = i;
261 i = pod->stack_next;
262 }
263
264 // We couldn't find any descriptors to close. This is weird but not
265 // necessarily an error.
266 return false;
267 }
268
269 // Close all the descriptors open for reading.
270
271 void
close_all()272 Descriptors::close_all()
273 {
274 Hold_optional_lock hl(this->lock_);
275
276 for (size_t i = 0; i < this->open_descriptors_.size(); i++)
277 {
278 Open_descriptor* pod = &this->open_descriptors_[i];
279 if (pod->name != NULL && !pod->inuse && !pod->is_write)
280 {
281 if (::close(i) < 0)
282 gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
283 gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\" (close_all)",
284 static_cast<int>(i), pod->name);
285 pod->name = NULL;
286 pod->stack_next = -1;
287 pod->is_on_stack = false;
288 }
289 }
290 this->stack_top_ = -1;
291 }
292
293 // The single global variable which manages descriptors.
294
295 Descriptors descriptors;
296
297 } // End namespace gold.
298