| 1 | // descriptors.cc -- manage file descriptors for gold |
| 2 | |
| 3 | // Copyright (C) 2008-2019 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 <string> |
| 30 | #include <unistd.h> |
| 31 | |
| 32 | #include "debug.h" |
| 33 | #include "parameters.h" |
| 34 | #include "options.h" |
| 35 | #include "gold-threads.h" |
| 36 | #include "descriptors.h" |
| 37 | #include "binary-io.h" |
| 38 | |
| 39 | // O_CLOEXEC is only available on newer systems. |
| 40 | #ifndef O_CLOEXEC |
| 41 | #define O_CLOEXEC 0 |
| 42 | #endif |
| 43 | |
| 44 | // Very old systems may not define FD_CLOEXEC. |
| 45 | #ifndef FD_CLOEXEC |
| 46 | #define FD_CLOEXEC 1 |
| 47 | #endif |
| 48 | |
| 49 | static inline void |
| 50 | set_close_on_exec(int fd ATTRIBUTE_UNUSED) |
| 51 | { |
| 52 | // Mingw does not define F_SETFD. |
| 53 | #ifdef F_SETFD |
| 54 | fcntl(fd, F_SETFD, FD_CLOEXEC); |
| 55 | #endif |
| 56 | } |
| 57 | |
| 58 | namespace gold |
| 59 | { |
| 60 | |
| 61 | // Class Descriptors. |
| 62 | |
| 63 | // The default for limit_ is meant to simply be large. It gets |
| 64 | // adjusted downward if we run out of file descriptors. |
| 65 | |
| 66 | Descriptors::Descriptors() |
| 67 | : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(), |
| 68 | stack_top_(-1), current_(0), limit_(8192 - 16) |
| 69 | { |
| 70 | this->open_descriptors_.reserve(128); |
| 71 | } |
| 72 | |
| 73 | // Open a file. |
| 74 | |
| 75 | int |
| 76 | Descriptors::open(int descriptor, const char* name, int flags, int mode) |
| 77 | { |
| 78 | // We don't initialize this until we are called, because we can't |
| 79 | // initialize a Lock until we have parsed the options to find out |
| 80 | // whether we are running with threads. We can be called before |
| 81 | // options are valid when reading a linker script. |
| 82 | bool lock_initialized = this->initialize_lock_.initialize(); |
| 83 | |
| 84 | gold_assert(lock_initialized || descriptor < 0); |
| 85 | |
| 86 | if (is_debugging_enabled(DEBUG_FILES)) |
| 87 | this->limit_ = 8; |
| 88 | |
| 89 | if (descriptor >= 0) |
| 90 | { |
| 91 | Hold_lock hl(*this->lock_); |
| 92 | |
| 93 | gold_assert(static_cast<size_t>(descriptor) |
| 94 | < this->open_descriptors_.size()); |
| 95 | Open_descriptor* pod = &this->open_descriptors_[descriptor]; |
| 96 | if (pod->name == name |
| 97 | || (pod->name != NULL && strcmp(pod->name, name) == 0)) |
| 98 | { |
| 99 | gold_assert(!pod->inuse); |
| 100 | pod->inuse = true; |
| 101 | if (descriptor == this->stack_top_) |
| 102 | { |
| 103 | this->stack_top_ = pod->stack_next; |
| 104 | pod->stack_next = -1; |
| 105 | pod->is_on_stack = false; |
| 106 | } |
| 107 | gold_debug(DEBUG_FILES, "Reused existing descriptor %d for \"%s\"", |
| 108 | descriptor, name); |
| 109 | return descriptor; |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | while (true) |
| 114 | { |
| 115 | // We always want to set the close-on-exec flag; we don't |
| 116 | // require callers to pass it. |
| 117 | flags |= O_CLOEXEC; |
| 118 | |
| 119 | // Always open the file as a binary file. |
| 120 | flags |= O_BINARY; |
| 121 | |
| 122 | int new_descriptor = ::open(name, flags, mode); |
| 123 | if (new_descriptor < 0 |
| 124 | && errno != ENFILE |
| 125 | && errno != EMFILE) |
| 126 | { |
| 127 | if (descriptor >= 0 && errno == ENOENT) |
| 128 | { |
| 129 | { |
| 130 | Hold_lock hl(*this->lock_); |
| 131 | |
| 132 | gold_error(_("file %s was removed during the link"), name); |
| 133 | } |
| 134 | |
| 135 | errno = ENOENT; |
| 136 | } |
| 137 | |
| 138 | gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"", |
| 139 | new_descriptor, name); |
| 140 | return new_descriptor; |
| 141 | } |
| 142 | |
| 143 | if (new_descriptor >= 0) |
| 144 | { |
| 145 | // If we have any plugins, we really do need to set the |
| 146 | // close-on-exec flag, even if O_CLOEXEC is not defined. |
| 147 | // FIXME: In some cases O_CLOEXEC may be defined in the |
| 148 | // header file but not supported by the kernel. |
| 149 | // Unfortunately there doesn't seem to be any obvious way to |
| 150 | // detect that, as unknown flags passed to open are ignored. |
| 151 | if (O_CLOEXEC == 0 |
| 152 | && parameters->options_valid() |
| 153 | && parameters->options().has_plugins()) |
| 154 | set_close_on_exec(new_descriptor); |
| 155 | |
| 156 | { |
| 157 | Hold_optional_lock hl(this->lock_); |
| 158 | |
| 159 | if (static_cast<size_t>(new_descriptor) |
| 160 | >= this->open_descriptors_.size()) |
| 161 | this->open_descriptors_.resize(new_descriptor + 64); |
| 162 | |
| 163 | Open_descriptor* pod = &this->open_descriptors_[new_descriptor]; |
| 164 | pod->name = name; |
| 165 | pod->stack_next = -1; |
| 166 | pod->inuse = true; |
| 167 | pod->is_write = (flags & O_ACCMODE) != O_RDONLY; |
| 168 | pod->is_on_stack = false; |
| 169 | |
| 170 | ++this->current_; |
| 171 | if (this->current_ >= this->limit_) |
| 172 | this->close_some_descriptor(); |
| 173 | |
| 174 | gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"", |
| 175 | new_descriptor, name); |
| 176 | return new_descriptor; |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | // We ran out of file descriptors. |
| 181 | { |
| 182 | Hold_optional_lock hl(this->lock_); |
| 183 | |
| 184 | this->limit_ = this->current_ - 16; |
| 185 | if (this->limit_ < 8) |
| 186 | this->limit_ = 8; |
| 187 | if (!this->close_some_descriptor()) |
| 188 | gold_fatal(_("out of file descriptors and couldn't close any")); |
| 189 | } |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | // Release a descriptor. |
| 194 | |
| 195 | void |
| 196 | Descriptors::release(int descriptor, bool permanent) |
| 197 | { |
| 198 | Hold_optional_lock hl(this->lock_); |
| 199 | |
| 200 | gold_assert(descriptor >= 0 |
| 201 | && (static_cast<size_t>(descriptor) |
| 202 | < this->open_descriptors_.size())); |
| 203 | Open_descriptor* pod = &this->open_descriptors_[descriptor]; |
| 204 | |
| 205 | if (permanent |
| 206 | || (this->current_ > this->limit_ && !pod->is_write)) |
| 207 | { |
| 208 | if (::close(descriptor) < 0) |
| 209 | gold_warning(_("while closing %s: %s"), pod->name, strerror(errno)); |
| 210 | pod->name = NULL; |
| 211 | --this->current_; |
| 212 | } |
| 213 | else |
| 214 | { |
| 215 | pod->inuse = false; |
| 216 | if (!pod->is_write && !pod->is_on_stack) |
| 217 | { |
| 218 | pod->stack_next = this->stack_top_; |
| 219 | this->stack_top_ = descriptor; |
| 220 | pod->is_on_stack = true; |
| 221 | } |
| 222 | } |
| 223 | |
| 224 | gold_debug(DEBUG_FILES, "Released descriptor %d for \"%s\"", |
| 225 | descriptor, pod->name); |
| 226 | } |
| 227 | |
| 228 | // Close some descriptor. The lock is held when this is called. We |
| 229 | // close the descriptor on the top of the free stack. Note that this |
| 230 | // is the opposite of an LRU algorithm--we close the most recently |
| 231 | // used descriptor. That is because the linker tends to cycle through |
| 232 | // all the files; after we release a file, we are unlikely to need it |
| 233 | // again until we have looked at all the other files. Return true if |
| 234 | // we closed a descriptor. |
| 235 | |
| 236 | bool |
| 237 | Descriptors::close_some_descriptor() |
| 238 | { |
| 239 | int last = -1; |
| 240 | int i = this->stack_top_; |
| 241 | while (i >= 0) |
| 242 | { |
| 243 | gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size()); |
| 244 | Open_descriptor* pod = &this->open_descriptors_[i]; |
| 245 | if (!pod->inuse && !pod->is_write) |
| 246 | { |
| 247 | if (::close(i) < 0) |
| 248 | gold_warning(_("while closing %s: %s"), pod->name, strerror(errno)); |
| 249 | --this->current_; |
| 250 | gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\"", |
| 251 | i, pod->name); |
| 252 | pod->name = NULL; |
| 253 | if (last < 0) |
| 254 | this->stack_top_ = pod->stack_next; |
| 255 | else |
| 256 | this->open_descriptors_[last].stack_next = pod->stack_next; |
| 257 | pod->stack_next = -1; |
| 258 | pod->is_on_stack = false; |
| 259 | return true; |
| 260 | } |
| 261 | last = i; |
| 262 | i = pod->stack_next; |
| 263 | } |
| 264 | |
| 265 | // We couldn't find any descriptors to close. This is weird but not |
| 266 | // necessarily an error. |
| 267 | return false; |
| 268 | } |
| 269 | |
| 270 | // Close all the descriptors open for reading. |
| 271 | |
| 272 | void |
| 273 | Descriptors::close_all() |
| 274 | { |
| 275 | Hold_optional_lock hl(this->lock_); |
| 276 | |
| 277 | for (size_t i = 0; i < this->open_descriptors_.size(); i++) |
| 278 | { |
| 279 | Open_descriptor* pod = &this->open_descriptors_[i]; |
| 280 | if (pod->name != NULL && !pod->inuse && !pod->is_write) |
| 281 | { |
| 282 | if (::close(i) < 0) |
| 283 | gold_warning(_("while closing %s: %s"), pod->name, strerror(errno)); |
| 284 | gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\" (close_all)", |
| 285 | static_cast<int>(i), pod->name); |
| 286 | pod->name = NULL; |
| 287 | pod->stack_next = -1; |
| 288 | pod->is_on_stack = false; |
| 289 | } |
| 290 | } |
| 291 | this->stack_top_ = -1; |
| 292 | } |
| 293 | |
| 294 | // The single global variable which manages descriptors. |
| 295 | |
| 296 | Descriptors descriptors; |
| 297 | |
| 298 | } // End namespace gold. |