gold/descriptors.cc

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