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