gold/descriptors.cc

   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 <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
  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
  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
  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
 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
 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
 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.