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// descriptors.cc -- manage file descriptors for gold

// Copyright 2008, 2009 Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

#include "gold.h"

#include <cerrno>

#include <cstdio>

#include <cstring>

#include <fcntl.h>

#include <unistd.h>

#include "parameters.h"

#include "options.h"

#include "gold-threads.h"

#include "descriptors.h"

#include "binary-io.h"

// Very old systems may not define FD_CLOEXEC.

#ifndef FD_CLOEXEC

#define FD_CLOEXEC 1

#endif

// O_CLOEXEC is only available on newer systems.

#ifndef O_CLOEXEC

#define O_CLOEXEC 0

#endif

namespace gold

{

// Class Descriptors.

// The default for limit_ is meant to simply be large.  It gets

// adjusted downward if we run out of file descriptors.

Descriptors::Descriptors()

  : lock_(NULL), initialize_lock_(&this->lock_), open_descriptors_(),

    stack_top_(-1), current_(0), limit_(8192 - 16)

{

  this->open_descriptors_.reserve(128);

}

// Open a file.

int

Descriptors::open(int descriptor, const char* name, int flags, int mode)

{

  // We don't initialize this until we are called, because we can't

  // initialize a Lock until we have parsed the options to find out

  // whether we are running with threads.  We can be called before

  // options are valid when reading a linker script.

  bool lock_initialized = this->initialize_lock_.initialize();

  gold_assert(lock_initialized || descriptor < 0);

  if (descriptor >= 0)

    {

      Hold_lock hl(*this->lock_);

      gold_assert(static_cast<size_t>(descriptor)

                  < this->open_descriptors_.size());

      Open_descriptor* pod = &this->open_descriptors_[descriptor];

      if (pod->name == name

          || (pod->name != NULL && strcmp(pod->name, name) == 0))

        {

          gold_assert(!pod->inuse);

          pod->inuse = true;

          if (descriptor == this->stack_top_)

            {

              this->stack_top_ = pod->stack_next;

              pod->stack_next = -1;

              pod->is_on_stack = false;

            }

          return descriptor;

        }

    }

  while (true)

    {

      // We always want to set the close-on-exec flag; we don't

      // require callers to pass it.

      flags |= O_CLOEXEC;

      // Always open the file as a binary file.

      flags |= O_BINARY;

      int new_descriptor = ::open(name, flags, mode);

      if (new_descriptor < 0

          && errno != ENFILE

          && errno != EMFILE)

        {

          if (descriptor >= 0 && errno == ENOENT)

            {

              {

                Hold_lock hl(*this->lock_);

                gold_error(_("file %s was removed during the link"),

                           this->open_descriptors_[descriptor].name);

              }

              errno = ENOENT;

            }

          return new_descriptor;

        }

      if (new_descriptor >= 0)

        {

          // If we have any plugins, we really do need to set the

          // close-on-exec flag, even if O_CLOEXEC is not defined.

          // FIXME: In some cases O_CLOEXEC may be defined in the

          // header file but not supported by the kernel.

          // Unfortunately there doesn't seem to be any obvious way to

          // detect that, as unknown flags passed to open are ignored.

          if (O_CLOEXEC == 0

              && parameters->options_valid()

              && parameters->options().has_plugins())

            fcntl(new_descriptor, F_SETFD, FD_CLOEXEC);

          {

            Hold_optional_lock hl(this->lock_);

            if (static_cast<size_t>(new_descriptor)

                >= this->open_descriptors_.size())

              this->open_descriptors_.resize(new_descriptor + 64);

            Open_descriptor* pod = &this->open_descriptors_[new_descriptor];

            pod->name = name;

            pod->stack_next = -1;

            pod->inuse = true;

            pod->is_write = (flags & O_ACCMODE) != O_RDONLY;

            pod->is_on_stack = false;

            ++this->current_;

            if (this->current_ >= this->limit_)

              this->close_some_descriptor();

            return new_descriptor;

          }

        }

      // We ran out of file descriptors.

      {

        Hold_optional_lock hl(this->lock_);

        this->limit_ = this->current_ - 16;

        if (this->limit_ < 8)

          this->limit_ = 8;

        if (!this->close_some_descriptor())

          gold_fatal(_("out of file descriptors and couldn't close any"));

      }

    }

}

// Release a descriptor.

void

Descriptors::release(int descriptor, bool permanent)

{

  Hold_optional_lock hl(this->lock_);

  gold_assert(descriptor >= 0

              && (static_cast<size_t>(descriptor)

                  < this->open_descriptors_.size()));

  Open_descriptor* pod = &this->open_descriptors_[descriptor];

  if (permanent

      || (this->current_ > this->limit_ && !pod->is_write))

    {

      if (::close(descriptor) < 0)

        gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));

      pod->name = NULL;

      --this->current_;

    }

  else

    {

      pod->inuse = false;

      if (!pod->is_write && !pod->is_on_stack)

        {

          pod->stack_next = this->stack_top_;

          this->stack_top_ = descriptor;

          pod->is_on_stack = true;

        }

    }

}

// Close some descriptor.  The lock is held when this is called.  We

// close the descriptor on the top of the free stack.  Note that this

// is the opposite of an LRU algorithm--we close the most recently

// used descriptor.  That is because the linker tends to cycle through

// all the files; after we release a file, we are unlikely to need it

// again until we have looked at all the other files.  Return true if

// we closed a descriptor.

bool

Descriptors::close_some_descriptor()

{

  int last = -1;

  int i = this->stack_top_;

  while (i >= 0)

    {

      gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size());

      Open_descriptor* pod = &this->open_descriptors_[i];

      if (!pod->inuse && !pod->is_write)

        {

          if (::close(i) < 0)

            gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));

          --this->current_;

          pod->name = NULL;

          if (last < 0)

            this->stack_top_ = pod->stack_next;

          else

            this->open_descriptors_[last].stack_next = pod->stack_next;

          pod->stack_next = -1;

          pod->is_on_stack = false;

          return true;

        }

      last = i;

      i = pod->stack_next;

    }

  // We couldn't find any descriptors to close.  This is weird but not

  // necessarily an error.

  return false;

}

// The single global variable which manages descriptors.

Descriptors descriptors;

} // End namespace gold.