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 47namespace 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 55Descriptors::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 64int 65Descriptors::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"), 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 == 0 134 && parameters->options_valid() 135 && parameters->options().has_plugins()) 136 fcntl(new_descriptor, F_SETFD, FD_CLOEXEC); 137 138 { 139 Hold_optional_lock hl(this->lock_); 140 141 if (static_cast<size_t>(new_descriptor) 142 >= this->open_descriptors_.size()) 143 this->open_descriptors_.resize(new_descriptor + 64); 144 145 Open_descriptor* pod = &this->open_descriptors_[new_descriptor]; 146 pod->name = name; 147 pod->stack_next = -1; 148 pod->inuse = true; 149 pod->is_write = (flags & O_ACCMODE) != O_RDONLY; 150 pod->is_on_stack = false; 151 152 ++this->current_; 153 if (this->current_ >= this->limit_) 154 this->close_some_descriptor(); 155 156 return new_descriptor; 157 } 158 } 159 160 // We ran out of file descriptors. 161 { 162 Hold_optional_lock hl(this->lock_); 163 164 this->limit_ = this->current_ - 16; 165 if (this->limit_ < 8) 166 this->limit_ = 8; 167 if (!this->close_some_descriptor()) 168 gold_fatal(_("out of file descriptors and couldn't close any")); 169 } 170 } 171} 172 173// Release a descriptor. 174 175void 176Descriptors::release(int descriptor, bool permanent) 177{ 178 Hold_optional_lock hl(this->lock_); 179 180 gold_assert(descriptor >= 0 181 && (static_cast<size_t>(descriptor) 182 < this->open_descriptors_.size())); 183 Open_descriptor* pod = &this->open_descriptors_[descriptor]; 184 185 if (permanent 186 || (this->current_ > this->limit_ && !pod->is_write)) 187 { 188 if (::close(descriptor) < 0) 189 gold_warning(_("while closing %s: %s"), pod->name, strerror(errno)); 190 pod->name = NULL; 191 --this->current_; 192 } 193 else 194 { 195 pod->inuse = false; 196 if (!pod->is_write && !pod->is_on_stack) 197 { 198 pod->stack_next = this->stack_top_; 199 this->stack_top_ = descriptor; 200 pod->is_on_stack = true; 201 } 202 } 203} 204 205// Close some descriptor. The lock is held when this is called. We 206// close the descriptor on the top of the free stack. Note that this 207// is the opposite of an LRU algorithm--we close the most recently 208// used descriptor. That is because the linker tends to cycle through 209// all the files; after we release a file, we are unlikely to need it 210// again until we have looked at all the other files. Return true if 211// we closed a descriptor. 212 213bool 214Descriptors::close_some_descriptor() 215{ 216 int last = -1; 217 int i = this->stack_top_; 218 while (i >= 0) 219 { 220 gold_assert(static_cast<size_t>(i) < this->open_descriptors_.size()); 221 Open_descriptor* pod = &this->open_descriptors_[i]; 222 if (!pod->inuse && !pod->is_write) 223 { 224 if (::close(i) < 0) 225 gold_warning(_("while closing %s: %s"), pod->name, strerror(errno)); 226 --this->current_; 227 pod->name = NULL; 228 if (last < 0) 229 this->stack_top_ = pod->stack_next; 230 else 231 this->open_descriptors_[last].stack_next = pod->stack_next; 232 pod->stack_next = -1; 233 pod->is_on_stack = false; 234 return true; 235 } 236 last = i; 237 i = pod->stack_next; 238 } 239 240 // We couldn't find any descriptors to close. This is weird but not 241 // necessarily an error. 242 return false; 243} 244 245// The single global variable which manages descriptors. 246 247Descriptors descriptors; 248 249} // End namespace gold. 250