blob: c64e8e86405884726a049c9f3c6c8b69a26d7aa5 [file] [log] [blame]
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/shared_memory.h"
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "base/file_util.h"
#include "base/logging.h"
#include "base/threading/platform_thread.h"
#include "base/safe_strerror_posix.h"
#include "base/threading/thread_restrictions.h"
#include "base/utf_string_conversions.h"
namespace base {
namespace {
// Paranoia. Semaphores and shared memory segments should live in different
// namespaces, but who knows what's out there.
const char kSemaphoreSuffix[] = "-sem";
}
SharedMemory::SharedMemory()
: mapped_file_(-1),
mapped_size_(0),
inode_(0),
memory_(NULL),
read_only_(false),
created_size_(0) {
}
SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
: mapped_file_(handle.fd),
mapped_size_(0),
inode_(0),
memory_(NULL),
read_only_(read_only),
created_size_(0) {
struct stat st;
if (fstat(handle.fd, &st) == 0) {
// If fstat fails, then the file descriptor is invalid and we'll learn this
// fact when Map() fails.
inode_ = st.st_ino;
}
}
SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
ProcessHandle process)
: mapped_file_(handle.fd),
mapped_size_(0),
inode_(0),
memory_(NULL),
read_only_(read_only),
created_size_(0) {
// We don't handle this case yet (note the ignored parameter); let's die if
// someone comes calling.
NOTREACHED();
}
SharedMemory::~SharedMemory() {
Close();
}
// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
return handle.fd >= 0;
}
// static
SharedMemoryHandle SharedMemory::NULLHandle() {
return SharedMemoryHandle();
}
// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
DCHECK(handle.fd >= 0);
if (HANDLE_EINTR(close(handle.fd)) < 0)
PLOG(ERROR) << "close";
}
bool SharedMemory::CreateAndMapAnonymous(uint32 size) {
return CreateAnonymous(size) && Map(size);
}
bool SharedMemory::CreateAnonymous(uint32 size) {
return CreateNamed("", false, size);
}
// Chromium mostly only uses the unique/private shmem as specified by
// "name == L"". The exception is in the StatsTable.
// TODO(jrg): there is no way to "clean up" all unused named shmem if
// we restart from a crash. (That isn't a new problem, but it is a problem.)
// In case we want to delete it later, it may be useful to save the value
// of mem_filename after FilePathForMemoryName().
bool SharedMemory::CreateNamed(const std::string& name,
bool open_existing, uint32 size) {
DCHECK_EQ(-1, mapped_file_);
if (size == 0) return false;
// This function theoretically can block on the disk, but realistically
// the temporary files we create will just go into the buffer cache
// and be deleted before they ever make it out to disk.
base::ThreadRestrictions::ScopedAllowIO allow_io;
FILE *fp;
bool fix_size = true;
FilePath path;
if (name.empty()) {
// It doesn't make sense to have a open-existing private piece of shmem
DCHECK(!open_existing);
// Q: Why not use the shm_open() etc. APIs?
// A: Because they're limited to 4mb on OS X. FFFFFFFUUUUUUUUUUU
fp = file_util::CreateAndOpenTemporaryShmemFile(&path);
// Deleting the file prevents anyone else from mapping it in
// (making it private), and prevents the need for cleanup (once
// the last fd is closed, it is truly freed).
if (fp)
file_util::Delete(path, false);
} else {
if (!FilePathForMemoryName(name, &path))
return false;
fp = file_util::OpenFile(path, "w+x");
if (fp == NULL && open_existing) {
// "w+" will truncate if it already exists.
fp = file_util::OpenFile(path, "a+");
fix_size = false;
}
}
if (fp && fix_size) {
// Get current size.
struct stat stat;
if (fstat(fileno(fp), &stat) != 0)
return false;
const uint32 current_size = stat.st_size;
if (current_size != size) {
if (HANDLE_EINTR(ftruncate(fileno(fp), size)) != 0)
return false;
if (fseeko(fp, size, SEEK_SET) != 0)
return false;
}
created_size_ = size;
}
if (fp == NULL) {
#if !defined(OS_MACOSX)
PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
FilePath dir = path.DirName();
if (access(dir.value().c_str(), W_OK | X_OK) < 0) {
PLOG(ERROR) << "Unable to access(W_OK|X_OK) " << dir.value();
if (dir.value() == "/dev/shm") {
LOG(FATAL) << "This is frequently caused by incorrect permissions on "
<< "/dev/shm. Try 'sudo chmod 1777 /dev/shm' to fix.";
}
}
#else
PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
#endif
return false;
}
return PrepareMapFile(fp);
}
// Our current implementation of shmem is with mmap()ing of files.
// These files need to be deleted explicitly.
// In practice this call is only needed for unit tests.
bool SharedMemory::Delete(const std::string& name) {
FilePath path;
if (!FilePathForMemoryName(name, &path))
return false;
if (file_util::PathExists(path)) {
return file_util::Delete(path, false);
}
// Doesn't exist, so success.
return true;
}
bool SharedMemory::Open(const std::string& name, bool read_only) {
FilePath path;
if (!FilePathForMemoryName(name, &path))
return false;
read_only_ = read_only;
const char *mode = read_only ? "r" : "r+";
FILE *fp = file_util::OpenFile(path, mode);
return PrepareMapFile(fp);
}
bool SharedMemory::Map(uint32 bytes) {
if (mapped_file_ == -1)
return false;
memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
MAP_SHARED, mapped_file_, 0);
if (memory_)
mapped_size_ = bytes;
bool mmap_succeeded = (memory_ != (void*)-1);
DCHECK(mmap_succeeded) << "Call to mmap failed, errno=" << errno;
return mmap_succeeded;
}
bool SharedMemory::Unmap() {
if (memory_ == NULL)
return false;
munmap(memory_, mapped_size_);
memory_ = NULL;
mapped_size_ = 0;
return true;
}
SharedMemoryHandle SharedMemory::handle() const {
return FileDescriptor(mapped_file_, false);
}
void SharedMemory::Close() {
Unmap();
if (mapped_file_ > 0) {
if (HANDLE_EINTR(close(mapped_file_)) < 0)
PLOG(ERROR) << "close";
mapped_file_ = -1;
}
}
void SharedMemory::Lock() {
#if !defined(ANDROID)
LockOrUnlockCommon(F_LOCK);
#endif
}
void SharedMemory::Unlock() {
#if !defined(ANDROID)
LockOrUnlockCommon(F_ULOCK);
#endif
}
bool SharedMemory::PrepareMapFile(FILE *fp) {
DCHECK_EQ(-1, mapped_file_);
if (fp == NULL) return false;
// This function theoretically can block on the disk, but realistically
// the temporary files we create will just go into the buffer cache
// and be deleted before they ever make it out to disk.
base::ThreadRestrictions::ScopedAllowIO allow_io;
file_util::ScopedFILE file_closer(fp);
mapped_file_ = dup(fileno(fp));
if (mapped_file_ == -1) {
if (errno == EMFILE) {
LOG(WARNING) << "Shared memory creation failed; out of file descriptors";
return false;
} else {
NOTREACHED() << "Call to dup failed, errno=" << errno;
}
}
struct stat st;
if (fstat(mapped_file_, &st))
NOTREACHED();
inode_ = st.st_ino;
return true;
}
// For the given shmem named |mem_name|, return a filename to mmap()
// (and possibly create). Modifies |filename|. Return false on
// error, or true of we are happy.
bool SharedMemory::FilePathForMemoryName(const std::string& mem_name,
FilePath* path) {
// mem_name will be used for a filename; make sure it doesn't
// contain anything which will confuse us.
DCHECK_EQ(std::string::npos, mem_name.find('/'));
DCHECK_EQ(std::string::npos, mem_name.find('\0'));
FilePath temp_dir;
if (!file_util::GetShmemTempDir(&temp_dir))
return false;
*path = temp_dir.AppendASCII("com.google.chrome.shmem." + mem_name);
return true;
}
void SharedMemory::LockOrUnlockCommon(int function) {
DCHECK_GE(mapped_file_, 0);
#if !defined(ANDROID)
while (lockf(mapped_file_, function, 0) < 0) {
if (errno == EINTR) {
continue;
} else if (errno == ENOLCK) {
// temporary kernel resource exaustion
base::PlatformThread::Sleep(500);
continue;
} else {
NOTREACHED() << "lockf() failed."
<< " function:" << function
<< " fd:" << mapped_file_
<< " errno:" << errno
<< " msg:" << safe_strerror(errno);
}
}
#endif
}
bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
SharedMemoryHandle *new_handle,
bool close_self) {
const int new_fd = dup(mapped_file_);
DCHECK_GE(new_fd, 0);
new_handle->fd = new_fd;
new_handle->auto_close = true;
if (close_self)
Close();
return true;
}
} // namespace base