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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2008 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/platform_thread.h"
#include "base/string_util.h"
#include "mozilla/UniquePtr.h"
namespace base {
SharedMemory::SharedMemory()
: mapped_file_(-1),
inode_(0),
memory_(NULL),
read_only_(false),
max_size_(0) {
}
SharedMemory::~SharedMemory() {
Close();
}
bool SharedMemory::SetHandle(SharedMemoryHandle handle, bool read_only) {
DCHECK(mapped_file_ == -1);
struct stat st;
if (fstat(handle.fd, &st) < 0) {
return false;
}
mapped_file_ = handle.fd;
inode_ = st.st_ino;
read_only_ = read_only;
return true;
}
// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
return handle.fd >= 0;
}
// static
SharedMemoryHandle SharedMemory::NULLHandle() {
return SharedMemoryHandle();
}
bool SharedMemory::Create(const std::string &cname, bool read_only,
bool open_existing, size_t size) {
read_only_ = read_only;
std::wstring name = UTF8ToWide(cname);
int posix_flags = 0;
posix_flags |= read_only ? O_RDONLY : O_RDWR;
if (!open_existing || mapped_file_ <= 0)
posix_flags |= O_CREAT;
if (!CreateOrOpen(name, posix_flags, size))
return false;
max_size_ = size;
return true;
}
// 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::wstring& name) {
std::wstring mem_filename;
if (FilenameForMemoryName(name, &mem_filename) == false)
return false;
FilePath path(WideToUTF8(mem_filename));
if (file_util::PathExists(path)) {
return file_util::Delete(path);
}
// Doesn't exist, so success.
return true;
}
bool SharedMemory::Open(const std::wstring &name, bool read_only) {
read_only_ = read_only;
int posix_flags = 0;
posix_flags |= read_only ? O_RDONLY : O_RDWR;
return CreateOrOpen(name, posix_flags, 0);
}
// For the given shmem named |memname|, return a filename to mmap()
// (and possibly create). Modifies |filename|. Return false on
// error, or true of we are happy.
bool SharedMemory::FilenameForMemoryName(const std::wstring &memname,
std::wstring *filename) {
std::wstring mem_filename;
// mem_name will be used for a filename; make sure it doesn't
// contain anything which will confuse us.
DCHECK(memname.find_first_of(L"/") == std::string::npos);
DCHECK(memname.find_first_of(L"\0") == std::string::npos);
FilePath temp_dir;
if (file_util::GetShmemTempDir(&temp_dir) == false)
return false;
mem_filename = UTF8ToWide(temp_dir.value());
file_util::AppendToPath(&mem_filename, L"com.google.chrome.shmem." + memname);
*filename = mem_filename;
return true;
}
namespace {
// A class to handle auto-closing of FILE*'s.
class ScopedFILEClose {
public:
inline void operator()(FILE* x) const {
if (x) {
fclose(x);
}
}
};
typedef mozilla::UniquePtr<FILE, ScopedFILEClose> ScopedFILE;
}
// Chromium mostly only use 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 FilenameForMemoryName().
bool SharedMemory::CreateOrOpen(const std::wstring &name,
int posix_flags, size_t size) {
DCHECK(mapped_file_ == -1);
ScopedFILE file_closer;
FILE *fp;
if (name == L"") {
// It doesn't make sense to have a read-only private piece of shmem
DCHECK(posix_flags & (O_RDWR | O_WRONLY));
FilePath path;
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).
file_util::Delete(path);
} else {
std::wstring mem_filename;
if (FilenameForMemoryName(name, &mem_filename) == false)
return false;
std::string mode;
switch (posix_flags) {
case (O_RDWR | O_CREAT):
// Careful: "w+" will truncate if it already exists.
mode = "a+";
break;
case O_RDWR:
mode = "r+";
break;
case O_RDONLY:
mode = "r";
break;
default:
NOTIMPLEMENTED();
break;
}
fp = file_util::OpenFile(mem_filename, mode.c_str());
}
if (fp == NULL)
return false;
file_closer.reset(fp); // close when we go out of scope
// Make sure the (new) file is the right size.
// According to the man page, "Use of truncate() to extend a file is
// not portable."
if (size && (posix_flags & (O_RDWR | O_CREAT))) {
// Get current size.
struct stat stat;
if (fstat(fileno(fp), &stat) != 0)
return false;
size_t current_size = stat.st_size;
if (current_size != size) {
if (ftruncate(fileno(fp), size) != 0)
return false;
if (fseeko(fp, size, SEEK_SET) != 0)
return false;
}
}
mapped_file_ = dup(fileno(fp));
DCHECK(mapped_file_ >= 0);
struct stat st;
if (fstat(mapped_file_, &st))
NOTREACHED();
inode_ = st.st_ino;
return true;
}
bool SharedMemory::Map(size_t 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_)
max_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_, max_size_);
memory_ = NULL;
max_size_ = 0;
return true;
}
bool SharedMemory::ShareToProcessCommon(ProcessId processId,
SharedMemoryHandle *new_handle,
bool close_self) {
const int new_fd = dup(mapped_file_);
DCHECK(new_fd >= -1);
new_handle->fd = new_fd;
new_handle->auto_close = true;
if (close_self)
Close();
return true;
}
void SharedMemory::Close(bool unmap_view) {
if (unmap_view) {
Unmap();
}
if (mapped_file_ >= 0) {
close(mapped_file_);
mapped_file_ = -1;
}
}
#ifdef ANDROID
void SharedMemory::LockOrUnlockCommon(int function) {
DCHECK(mapped_file_ >= 0);
struct flock lockreq;
lockreq.l_type = function;
lockreq.l_whence = SEEK_SET;
lockreq.l_start = 0;
lockreq.l_len = 0;
while (fcntl(mapped_file_, F_SETLKW, &lockreq) < 0) {
if (errno == EINTR) {
continue;
} else if (errno == ENOLCK) {
// temporary kernel resource exaustion
PlatformThread::Sleep(500);
continue;
} else {
NOTREACHED() << "lockf() failed."
<< " function:" << function
<< " fd:" << mapped_file_
<< " errno:" << errno
<< " msg:" << strerror(errno);
}
}
}
void SharedMemory::Lock() {
LockOrUnlockCommon(F_WRLCK);
}
void SharedMemory::Unlock() {
LockOrUnlockCommon(F_UNLCK);
}
#else
void SharedMemory::LockOrUnlockCommon(int function) {
DCHECK(mapped_file_ >= 0);
while (lockf(mapped_file_, function, 0) < 0) {
if (errno == EINTR) {
continue;
} else if (errno == ENOLCK) {
// temporary kernel resource exaustion
PlatformThread::Sleep(500);
continue;
} else {
NOTREACHED() << "lockf() failed."
<< " function:" << function
<< " fd:" << mapped_file_
<< " errno:" << errno
<< " msg:" << strerror(errno);
}
}
}
void SharedMemory::Lock() {
LockOrUnlockCommon(F_LOCK);
}
void SharedMemory::Unlock() {
LockOrUnlockCommon(F_ULOCK);
}
#endif
SharedMemoryHandle SharedMemory::handle() const {
return FileDescriptor(mapped_file_, false);
}
} // namespace base
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