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