binutils-gdb/gold/descriptors.cc

299 lines
7.9 KiB
C++

// descriptors.cc -- manage file descriptors for gold
// Copyright (C) 2008-2020 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 <string>
#include <unistd.h>
#include "debug.h"
#include "parameters.h"
#include "options.h"
#include "gold-threads.h"
#include "descriptors.h"
#include "binary-io.h"
// O_CLOEXEC is only available on newer systems.
#ifndef O_CLOEXEC
#define O_CLOEXEC 0
#endif
// Very old systems may not define FD_CLOEXEC.
#ifndef FD_CLOEXEC
#define FD_CLOEXEC 1
#endif
static inline void
set_close_on_exec(int fd ATTRIBUTE_UNUSED)
{
// Mingw does not define F_SETFD.
#ifdef F_SETFD
fcntl(fd, F_SETFD, FD_CLOEXEC);
#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 (is_debugging_enabled(DEBUG_FILES))
this->limit_ = 8;
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;
}
gold_debug(DEBUG_FILES, "Reused existing descriptor %d for \"%s\"",
descriptor, name);
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"), name);
}
errno = ENOENT;
}
gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"",
new_descriptor, name);
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())
set_close_on_exec(new_descriptor);
{
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();
gold_debug(DEBUG_FILES, "Opened new descriptor %d for \"%s\"",
new_descriptor, name);
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;
}
}
gold_debug(DEBUG_FILES, "Released descriptor %d for \"%s\"",
descriptor, pod->name);
}
// 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_;
gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\"",
i, pod->name);
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;
}
// Close all the descriptors open for reading.
void
Descriptors::close_all()
{
Hold_optional_lock hl(this->lock_);
for (size_t i = 0; i < this->open_descriptors_.size(); i++)
{
Open_descriptor* pod = &this->open_descriptors_[i];
if (pod->name != NULL && !pod->inuse && !pod->is_write)
{
if (::close(i) < 0)
gold_warning(_("while closing %s: %s"), pod->name, strerror(errno));
gold_debug(DEBUG_FILES, "Closed descriptor %d for \"%s\" (close_all)",
static_cast<int>(i), pod->name);
pod->name = NULL;
pod->stack_next = -1;
pod->is_on_stack = false;
}
}
this->stack_top_ = -1;
}
// The single global variable which manages descriptors.
Descriptors descriptors;
} // End namespace gold.