gold/descriptors.cc

   1 // descriptors.cc -- manage file descriptors for gold
   2
   3 // Copyright 2008, 2009, 2010, 2011 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 // O_CLOEXEC is only available on newer systems.
  38 #ifndef O_CLOEXEC
  39 #define O_CLOEXEC 0
  40 #endif
  41
  42 // Very old systems may not define FD_CLOEXEC.
  43 #ifndef FD_CLOEXEC
  44 #define FD_CLOEXEC 1
  45 #endif
  46
  47 static inline void
  48 set_close_on_exec(int fd)
  49 {
  50 // Mingw does not define F_SETFD.
  51 #ifdef F_SETFD
  52   fcntl(fd, F_SETFD, FD_CLOEXEC);
  53 #endif
  54 }
  55
  56 namespace gold
  57 {
  58
  59 // Class Descriptors.
  60
  61 // The default for limit_ is meant to simply be large.  It gets
  62 // adjusted downward if we run out of file descriptors.
  63
  64 Descriptors::Descriptors()
  65   : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(),
  66     stack_top_(-1), current_(0), limit_(8192 - 16)
  67 {
  68   this->open_descriptors_.reserve(128);
  69 }
  70
  71 // Open a file.
  72
  73 int
  74 Descriptors::open(int descriptor, const char* name, int flags, int mode)
  75 {
  76   // We don't initialize this until we are called, because we can't
  77   // initialize a Lock until we have parsed the options to find out
  78   // whether we are running with threads.  We can be called before
  79   // options are valid when reading a linker script.
  80   bool lock_initialized = this->initialize_lock_.initialize();
  81
  82   gold_assert(lock_initialized || descriptor < 0);
  83
  84   if (descriptor >= 0)
  85     {
  86       Hold_lock hl(*this->lock_);
  87
  88       gold_assert(static_cast<size_t>(descriptor)
  89                   < this->open_descriptors_.size());
  90       Open_descriptor* pod = &this->open_descriptors_[descriptor];
  91       if (pod->name == name
  92           || (pod->name != NULL && strcmp(pod->name, name) == 0))
  93         {
  94           gold_assert(!pod->inuse);
  95           pod->inuse = true;
  96           if (descriptor == this->stack_top_)
  97             {
  98               this->stack_top_ = pod->stack_next;
  99               pod->stack_next = -1;
 100               pod->is_on_stack = false;
 101             }
 102           return descriptor;
 103         }
 104     }
 105
 106   while (true)
 107     {
 108       // We always want to set the close-on-exec flag; we don't
 109       // require callers to pass it.
 110       flags |= O_CLOEXEC;
 111
 112       // Always open the file as a binary file.
 113       flags |= O_BINARY;
 114
 115       int new_descriptor = ::open(name, flags, mode);
 116       if (new_descriptor < 0
 117           && errno != ENFILE
 118           && errno != EMFILE)
 119         {
 120           if (descriptor >= 0 && errno == ENOENT)
 121             {
 122               {
 123                 Hold_lock hl(*this->lock_);
 124
 125                 gold_error(_("file %s was removed during the link"), name);
 126               }
 127
 128               errno = ENOENT;
 129             }
 130
 131           return new_descriptor;
 132         }
 133
 134       if (new_descriptor >= 0)
 135         {
 136           // If we have any plugins, we really do need to set the
 137           // close-on-exec flag, even if O_CLOEXEC is not defined.
 138           // FIXME: In some cases O_CLOEXEC may be defined in the
 139           // header file but not supported by the kernel.
 140           // Unfortunately there doesn't seem to be any obvious way to
 141           // detect that, as unknown flags passed to open are ignored.
 142           if (O_CLOEXEC == 0
 143               && parameters->options_valid()
 144               && parameters->options().has_plugins())
 145             set_close_on_exec(new_descriptor);
 146
 147           {
 148             Hold_optional_lock hl(this->lock_);
 149
 150             if (static_cast<size_t>(new_descriptor)
 151                 >= this->open_descriptors_.size())
 152               this->open_descriptors_.resize(new_descriptor + 64);
 153
 154             Open_descriptor* pod = &this->open_descriptors_[new_descriptor];
 155             pod->name = name;
 156             pod->stack_next = -1;
 157             pod->inuse = true;
 158             pod->is_write = (flags & O_ACCMODE) != O_RDONLY;
 159             pod->is_on_stack = false;
 160
 161             ++this->current_;
 162             if (this->current_ >= this->limit_)
 163               this->close_some_descriptor();
 164
 165             return new_descriptor;
 166           }
 167         }
 168
 169       // We ran out of file descriptors.
 170       {
 171         Hold_optional_lock hl(this->lock_);
 172
 173         this->limit_ = this->current_ - 16;
 174         if (this->limit_ < 8)
 175           this->limit_ = 8;
 176         if (!this->close_some_descriptor())
 177           gold_fatal(_("out of file descriptors and couldn't close any"));
 178       }
 179     }
 180 }
 181
 182 // Release a descriptor.
 183
 184 void
 185 Descriptors::release(int descriptor, bool permanent)
 186 {
 187   Hold_optional_lock hl(this->lock_);
 188
 189   gold_assert(descriptor >= 0
 190               && (static_cast<size_t>(descriptor)
 191                   < this->open_descriptors_.size()));
 192   Open_descriptor* pod = &this->open_descriptors_[descriptor];
 193
 194   if (permanent
 195       || (this->current_ > this->limit_ && !pod->is_write))
 196     {
 197       if (::close(descriptor) < 0)
 198         gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 199       pod->name = NULL;
 200       --this->current_;
 201     }
 202   else
 203     {
 204       pod->inuse = false;
 205       if (!pod->is_write && !pod->is_on_stack)
 206         {
 207           pod->stack_next = this->stack_top_;
 208           this->stack_top_ = descriptor;
 209           pod->is_on_stack = true;
 210         }
 211     }
 212 }
 213
 214 // Close some descriptor.  The lock is held when this is called.  We
 215 // close the descriptor on the top of the free stack.  Note that this
 216 // is the opposite of an LRU algorithm--we close the most recently
 217 // used descriptor.  That is because the linker tends to cycle through
 218 // all the files; after we release a file, we are unlikely to need it
 219 // again until we have looked at all the other files.  Return true if
 220 // we closed a descriptor.
 221
 222 bool
 223 Descriptors::close_some_descriptor()
 224 {
 225   int last = -1;
 226   int i = this->stack_top_;
 227   while (i >= 0)
 228     {
 229       gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());
 230       Open_descriptor* pod = &this->open_descriptors_[i];
 231       if (!pod->inuse && !pod->is_write)
 232         {
 233           if (::close(i) < 0)
 234             gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
 235           --this->current_;
 236           pod->name = NULL;
 237           if (last < 0)
 238             this->stack_top_ = pod->stack_next;
 239           else
 240             this->open_descriptors_[last].stack_next = pod->stack_next;
 241           pod->stack_next = -1;
 242           pod->is_on_stack = false;
 243           return true;
 244         }
 245       last = i;
 246       i = pod->stack_next;
 247     }
 248
 249   // We couldn't find any descriptors to close.  This is weird but not
 250   // necessarily an error.
 251   return false;
 252 }
 253
 254 // The single global variable which manages descriptors.
 255
 256 Descriptors descriptors;
 257
 258 } // End namespace gold.