gold/descriptors.cc

   1 // descriptors.cc -- manage file descriptors for gold
   2
   3 // Copyright (C) 2008-2020 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.