eae9c0623d
BUG=68682 TEST=compiles Review URL: http://codereview.chromium.org/6085015 git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70975 0039d316-1c4b-4281-b951-d872f2087c98
326 lines
8.8 KiB
C++
326 lines
8.8 KiB
C++
// Copyright (c) 2010 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/shared_memory.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "base/file_util.h"
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#include "base/logging.h"
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#include "base/threading/platform_thread.h"
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#include "base/safe_strerror_posix.h"
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#include "base/threading/thread_restrictions.h"
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#include "base/utf_string_conversions.h"
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namespace base {
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namespace {
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// Paranoia. Semaphores and shared memory segments should live in different
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// namespaces, but who knows what's out there.
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const char kSemaphoreSuffix[] = "-sem";
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}
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SharedMemory::SharedMemory()
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: mapped_file_(-1),
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mapped_size_(0),
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inode_(0),
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memory_(NULL),
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read_only_(false),
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created_size_(0) {
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}
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SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
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: mapped_file_(handle.fd),
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mapped_size_(0),
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inode_(0),
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memory_(NULL),
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read_only_(read_only),
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created_size_(0) {
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struct stat st;
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if (fstat(handle.fd, &st) == 0) {
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// If fstat fails, then the file descriptor is invalid and we'll learn this
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// fact when Map() fails.
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inode_ = st.st_ino;
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}
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}
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SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
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ProcessHandle process)
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: mapped_file_(handle.fd),
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mapped_size_(0),
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inode_(0),
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memory_(NULL),
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read_only_(read_only),
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created_size_(0) {
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// We don't handle this case yet (note the ignored parameter); let's die if
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// someone comes calling.
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NOTREACHED();
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}
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SharedMemory::~SharedMemory() {
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Close();
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}
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// static
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bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
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return handle.fd >= 0;
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}
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// static
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SharedMemoryHandle SharedMemory::NULLHandle() {
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return SharedMemoryHandle();
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}
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// static
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void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
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DCHECK(handle.fd >= 0);
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close(handle.fd);
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}
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bool SharedMemory::CreateAndMapAnonymous(uint32 size) {
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return CreateAnonymous(size) && Map(size);
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}
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bool SharedMemory::CreateAnonymous(uint32 size) {
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return CreateNamed("", false, size);
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}
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// Chromium mostly only uses the unique/private shmem as specified by
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// "name == L"". The exception is in the StatsTable.
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// TODO(jrg): there is no way to "clean up" all unused named shmem if
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// we restart from a crash. (That isn't a new problem, but it is a problem.)
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// In case we want to delete it later, it may be useful to save the value
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// of mem_filename after FilePathForMemoryName().
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bool SharedMemory::CreateNamed(const std::string& name,
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bool open_existing, uint32 size) {
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DCHECK(mapped_file_ == -1);
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if (size == 0) return false;
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// This function theoretically can block on the disk, but realistically
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// the temporary files we create will just go into the buffer cache
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// and be deleted before they ever make it out to disk.
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base::ThreadRestrictions::ScopedAllowIO allow_io;
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FILE *fp;
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bool fix_size = true;
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FilePath path;
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if (name.empty()) {
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// It doesn't make sense to have a open-existing private piece of shmem
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DCHECK(!open_existing);
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// Q: Why not use the shm_open() etc. APIs?
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// A: Because they're limited to 4mb on OS X. FFFFFFFUUUUUUUUUUU
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fp = file_util::CreateAndOpenTemporaryShmemFile(&path);
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// Deleting the file prevents anyone else from mapping it in
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// (making it private), and prevents the need for cleanup (once
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// the last fd is closed, it is truly freed).
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if (fp)
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file_util::Delete(path, false);
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} else {
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if (!FilePathForMemoryName(name, &path))
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return false;
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fp = file_util::OpenFile(path, "w+x");
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if (fp == NULL && open_existing) {
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// "w+" will truncate if it already exists.
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fp = file_util::OpenFile(path, "a+");
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fix_size = false;
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}
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}
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if (fp && fix_size) {
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// Get current size.
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struct stat stat;
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if (fstat(fileno(fp), &stat) != 0)
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return false;
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const uint32 current_size = stat.st_size;
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if (current_size != size) {
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if (ftruncate(fileno(fp), size) != 0)
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return false;
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if (fseeko(fp, size, SEEK_SET) != 0)
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return false;
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}
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created_size_ = size;
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}
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if (fp == NULL) {
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#if !defined(OS_MACOSX)
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PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
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FilePath dir = path.DirName();
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if (access(dir.value().c_str(), W_OK | X_OK) < 0) {
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PLOG(ERROR) << "Unable to access(W_OK|X_OK) " << dir.value();
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if (dir.value() == "/dev/shm") {
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LOG(FATAL) << "This is frequently caused by incorrect permissions on "
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<< "/dev/shm. Try 'sudo chmod 1777 /dev/shm' to fix.";
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}
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}
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#else
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PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
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#endif
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return false;
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}
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return PrepareMapFile(fp);
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}
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// Our current implementation of shmem is with mmap()ing of files.
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// These files need to be deleted explicitly.
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// In practice this call is only needed for unit tests.
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bool SharedMemory::Delete(const std::string& name) {
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FilePath path;
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if (!FilePathForMemoryName(name, &path))
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return false;
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if (file_util::PathExists(path)) {
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return file_util::Delete(path, false);
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}
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// Doesn't exist, so success.
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return true;
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}
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bool SharedMemory::Open(const std::string& name, bool read_only) {
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FilePath path;
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if (!FilePathForMemoryName(name, &path))
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return false;
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read_only_ = read_only;
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const char *mode = read_only ? "r" : "r+";
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FILE *fp = file_util::OpenFile(path, mode);
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return PrepareMapFile(fp);
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}
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bool SharedMemory::Map(uint32 bytes) {
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if (mapped_file_ == -1)
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return false;
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memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
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MAP_SHARED, mapped_file_, 0);
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if (memory_)
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mapped_size_ = bytes;
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bool mmap_succeeded = (memory_ != (void*)-1);
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DCHECK(mmap_succeeded) << "Call to mmap failed, errno=" << errno;
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return mmap_succeeded;
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}
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bool SharedMemory::Unmap() {
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if (memory_ == NULL)
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return false;
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munmap(memory_, mapped_size_);
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memory_ = NULL;
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mapped_size_ = 0;
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return true;
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}
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SharedMemoryHandle SharedMemory::handle() const {
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return FileDescriptor(mapped_file_, false);
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}
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void SharedMemory::Close() {
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Unmap();
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if (mapped_file_ > 0) {
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close(mapped_file_);
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mapped_file_ = -1;
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}
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}
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void SharedMemory::Lock() {
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LockOrUnlockCommon(F_LOCK);
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}
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void SharedMemory::Unlock() {
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LockOrUnlockCommon(F_ULOCK);
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}
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bool SharedMemory::PrepareMapFile(FILE *fp) {
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DCHECK(mapped_file_ == -1);
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if (fp == NULL) return false;
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// This function theoretically can block on the disk, but realistically
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// the temporary files we create will just go into the buffer cache
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// and be deleted before they ever make it out to disk.
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base::ThreadRestrictions::ScopedAllowIO allow_io;
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file_util::ScopedFILE file_closer(fp);
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mapped_file_ = dup(fileno(fp));
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if (mapped_file_ == -1) {
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if (errno == EMFILE) {
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LOG(WARNING) << "Shared memory creation failed; out of file descriptors";
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return false;
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} else {
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NOTREACHED() << "Call to dup failed, errno=" << errno;
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}
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}
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struct stat st;
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if (fstat(mapped_file_, &st))
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NOTREACHED();
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inode_ = st.st_ino;
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return true;
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}
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// For the given shmem named |mem_name|, return a filename to mmap()
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// (and possibly create). Modifies |filename|. Return false on
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// error, or true of we are happy.
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bool SharedMemory::FilePathForMemoryName(const std::string& mem_name,
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FilePath* path) {
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// mem_name will be used for a filename; make sure it doesn't
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// contain anything which will confuse us.
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DCHECK(mem_name.find('/') == std::string::npos);
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DCHECK(mem_name.find('\0') == std::string::npos);
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FilePath temp_dir;
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if (!file_util::GetShmemTempDir(&temp_dir))
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return false;
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*path = temp_dir.AppendASCII("com.google.chrome.shmem." + mem_name);
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return true;
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}
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void SharedMemory::LockOrUnlockCommon(int function) {
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DCHECK(mapped_file_ >= 0);
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while (lockf(mapped_file_, function, 0) < 0) {
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if (errno == EINTR) {
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continue;
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} else if (errno == ENOLCK) {
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// temporary kernel resource exaustion
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base::PlatformThread::Sleep(500);
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continue;
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} else {
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NOTREACHED() << "lockf() failed."
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<< " function:" << function
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<< " fd:" << mapped_file_
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<< " errno:" << errno
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<< " msg:" << safe_strerror(errno);
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}
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}
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}
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bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
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SharedMemoryHandle *new_handle,
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bool close_self) {
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const int new_fd = dup(mapped_file_);
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DCHECK(new_fd >= 0);
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new_handle->fd = new_fd;
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new_handle->auto_close = true;
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if (close_self)
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Close();
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return true;
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}
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} // namespace base
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